Acute Otitis Media

An estimated 85% of all children experience at least one episode of AOM, making it the most common bacterial infection of childhood.³ Predisposing factors include young age; male sex; receiving bottle feedings; and being exposed to a daycare environment, crowded living conditions, or smoking within the home. Medical conditions such as cleft palate; Down syndrome; and mucous membrane abnormalities such as cystic fibrosis, ciliary dyskinesia, and immunodeficiency states also predispose individuals to otitis media.

AOM is a bacterial infection of the middle ear space characterized by vascular dilation and proliferation (manifested externally by tympanic membrane edema and erythema), mucosal edema, exudation, bacterial proliferation, white blood cell infiltration, and pus formation. AOM here refers only to an acute infection that arises de novo, in a previously normal middle ear, rather than an acute clinical infection arising in long-standing otitis media with effusion. This distinction underscores that patterns of complications are different in AOM versus COM.

After the first few weeks of life, acute suppurative otitis media is caused primarily by three organisms: Streptococcus pneumoniae, Haemophilus influenzae, and Branhamella catarrhalis, composing roughly 30%, 20%, and 10% of isolates.³ Optimal treatment for acute suppurative otitis media with complications includes appropriate antibiotics in addition to myringotomy and placement of a ventilating tube. Tympanocentesis is used primarily to obtain material for culture and sensitivity to identify the offending organism, but it can also reduce the bacterial population. Myringotomy and tube placement also provide material to identify the involved organism. After treatment, the physician should document that the AOM has completely resolved by tympanometry and otoscopy if the tympanic membrane is intact, and by otoscopy if a ventilating tube is in place. If the complication was intracranial, a computed tomography (CT) scan or magnetic resonance imaging (MRI) study should be obtained.

Chronic Otitis Media

AOM is primarily a middle ear infection that extends into the contiguous mastoid, whereas COM reflects persistent mastoid infection with concurrent otitis media. COM is present when an infectious process persists for longer than the 1 to 3 weeks usually necessary for resolving AOM in a previously healthy ear. COM can occur with or without cholesteatoma. Without cholesteatoma, there is typically a tympanic membrane perforation. A third type of COM is evident in young children with persistent otorrhea with a patent middle ear ventilating tube.

If infection in the middle ear and mastoid does not resolve, mucosal edema and exudation increase, and mucous glands and secretory elements proliferate. Mucosal edema in the spaces between the middle ear and the epitympanum and in the aditus between the epitympanum and mastoid antrum block the normal pathways for aeration and decrease oxygenation and vascularity. At the same time, the blockage prevents pharmacologic agents from reaching the attic and mastoid. Radiographically, the mastoid air cell system is partly or completely opaque, reflecting the loss of aeration.

COM changes are accompanied by a characteristic bacteriology compared with acute conditions. Harker and Koontz⁴ cultured 30 cholesteatomas at surgery and isolated at least one anaerobic organism in 67% of the cases, at least one aerobic organism in 70%, and both organisms in 50%. In 57% of the cholesteatomas, multiple organisms were cultured; in 30%, five or more bacteria were identified. Even without clinical infection, anaerobes, such as Propionibacterium acnes, were frequently isolated. An ear with COM is highly likely to harbor multiple bacteria of anaerobic and aerobic types.

COM that develops in patients with indwelling middle ear ventilating tubes has a different bacterial flora. In most instances, these cases begin with an upper respiratory infection or with water contamination. A series of events, including treatment with antibiotic drops, treatment with oral antibiotics, repeated contamination, repeated culture and sensitivity tests, increasing patient and physician frustration, decreasing patient compliance, and fungal overgrowth, frequently results in resistant organisms developing. The resistant bacteria most often found are Pseudomonas aeruginosa, Achromobacter xylosoxidans, and methicillin-resistant Staphylococcus aureus, although the etiologic importance of individual organisms identified on swab culture is unclear. A fungal component of the external auditory canal and the middle ear and mastoid should be considered.

History

The clinician must establish when the patient’s ear was last free of disease and perfectly normal to differentiate AOM from COM because the bacteriology, medical treatment, and most probable complications are different for each. Key questions relate to the following: (1) prior evaluation of the involved ear, (2) past history and treatment of the otitis media, (3) the order of appearance and magnitude of symptoms, and (4) objective evidence that the ear was normal recently (e.g., tympanogram, radiographic study that included the ears).

Intracranial complications, most notably meningitis, intraparenchymal brain abscess, and subdural empyema, can alter the patient’s level of consciousness. Of patients in the study by Singh and Maharaj,¹ 15% were drowsy on admission, 18% were stuporous, and 2% presented in a comatose state. Establishing the chronology of this alteration of sensorium helps the physician differentiate among diagnoses of brain abscess, meningitis, and subdural empyema. A brain abscess takes weeks to develop, whereas it takes only a few hours to several days for meningitis and subdural empyema to become fulminant and progress to coma.

Physical Examination

The vital signs, especially the temperature, provide a pretreatment baseline and one parameter for following the course of the disease and the treatment; however, if the patient has previously received oral or parenteral antibiotics, he or she may present without a fever. Although some patients with extracranial or intracranial complications remain afebrile during the entire course of their illnesses, the temperature curve can provide useful information in other patients.

Patients with intracranial or multiple complications often appear more systemically ill than patients with otitis alone. They can present with toxicity or with obtundation, manifesting depressed levels of consciousness that can vary from lethargy to total unresponsiveness. Focal neurologic signs may be absent, subtle, or florid. The physical examination of the ear itself usually does little to pinpoint a specific complication, unless there is an obvious postauricular, cervical, or temporal abscess.

A complete neurologic examination is essential. The clinician should evaluate the mental status and evaluate the station and gait along with the Romberg and sharpened Romberg tests. The motor and sensory function of the extremities should be evaluated, and a complete cranial nerve evaluation should be performed, including an assessment of vision, extraocular muscle function, facial nerve function, and facial sensation. The presence of nystagmus should be assessed. The clinician should evaluate cerebellar function by checking the alternate motion rate of the extremities, determining whether past pointing is present or absent, and performing the finger-to-nose test. Ocular saccades and smooth pursuit should be assessed.

It is crucial to determine whether nuchal rigidity is present, and if so, Kernig’s and Brudzinski’s signs must be sought. The optic discs should be observed with an ophthalmoscope to determine whether papilledema is present.

The otologic examination should begin with an assessment of the color, size, shape, and position of the pinna compared with the opposite side. The clinician should make note of any erythema, tenderness, or drainage, and any evidence of trauma, excoriation, or protrusion outward or downward. Next, the clinician should observe the regions adjacent to the auricle and note any swelling, erythema, tenderness, purulent drainage, or fluctuation.

The external auditory canal and tympanic membrane should be examined using a microscope and fine suction. If purulent secretions are present, a culture test should be performed. The clinician should document the presence of any edema, and whether it primarily affects the posterosuperior bony canal wall or the entire canal circumference. A drawing of the tympanic membrane should be made, illustrating any perforation, granulation tissue, or epithelial debris, and any erosion of the scutum. Pneumatic otoscopy should determine if there is conjugate deviation of the eyes suggesting a labyrinthine fistula.

The tympanic membrane can appear normal or near-normal even when an otologic complication is suspected because it reflects only the status of the middle ear. Although mastoid infection always begins with a middle ear infection, suppuration in these two locations can proceed differently, in that the middle ear may revert to normal or near-normal under treatment, whereas the mastoid may not.

We make special notation of the problem of an aditus block. The middle ear can appear normal after several courses of antibiotics while symptoms from the mastoid persist (see section on masked mastoiditis). When evaluating a patient with any infectious condition that could be caused by AOM or COM, a CT scan can evaluate the possibility of an aditus block as the cause, even if the tympanic membrane appears normal.

Imaging Techniques

CT scanning is essential for all patients suspected to have complications of otitis media. CT is a fast and reliable method for assessing the status of the middle ear and the mastoid air cell system and diagnosing intracranial complications of otitis media.^5,6 CT reveals bony details of the middle ear, epitympanic, and mastoid structures, and documents pneumatization versus opacification by inflammatory process. CT can show progressive demineralization and loss of the bony septa of air cells in coalescent mastoiditis, and reveal erosion of the bony plates covering the sigmoid sinus, cerebellum, or tegmen of the middle ear, mastoid, and bony labyrinth itself.

CT scans can help to establish the specific primary otologic diagnosis (e.g., AOM, COM, cholesteatoma), and several of the specific cranial and intracranial complications of otitis media. In addition to their diagnostic value, CT scans are useful in assessing the results of therapy, and provide a baseline post-treatment study of the mastoid for comparison in case of further complications.

When the patient is somnolent or unstable, and when intracranial complications are suspected, CT may be the study of choice because it is fast and gives the health care team better access to the patient during the study than MRI does. Even without enhancement, CT scanning can be an adequate diagnostic tool for a febrile, stuporous patient with meningeal irritation when ruling out the presence of an intraparenchymal brain abscess or communicating hydrocephalus before performing lumbar puncture to establish the diagnosis of meningitis. Intravenous injection of an iodinated contrast agent is essential, however, when using CT to diagnose cerebritis, cerebral abscess, subdural empyema, and ventriculitis.

MRI provides sensitive imaging for diagnosing intracranial complications because paramagnetic contrast agents such as gadolinium-DTPA (pentetic acid) cross the blood-brain barrier in areas of cerebritis or abscess. Meningeal enhancement is easily seen with MRI (and not on CT scanning, in which the adjacent bony skull often obscures the meninges). T2-weighted MR images can show intraparenchymal edema from subtle brain infection much earlier than a CT scan can. When otitic complications are suspected, CT scans and MRI provide valuable complementary information.

Fibrous tissue in the mastoid that is a result of previous (nonactive) COM or prior surgery enhances on MRI and may be misinterpreted by the radiologist as “mastoiditis.” In such cases, the enhancement reflects the increased vascularity of this fibrous tissue and is analogous to the routine observation of enhancement of the highly vascular nasal turbinates with gadolinium.

Lumbar Puncture

To detect meningitis, the physician must perform a lumbar puncture, measuring the cerebrospinal fluid (CSF) pressure when starting and ending the procedure. The CSF is examined for bacteria on direct smear and measured for glucose, chloride, and protein to compare with their concentrations in serum. Lumbar puncture should be undertaken only after clinical assessment, ophthalmoscopic examination (noting that papilledema sometimes requires hours to develop), and CT scan have ruled out significantly increased intracranial pressure that can result in herniation of the cerebellar tonsils during or after the procedure. Lumbar puncture is contraindicated in the presence of elevated intracranial pressure with brain abscess and subdural empyema.

Acute Mastoiditis

Acute mastoiditis can develop when AOM fails to resolve. According to Luntz and colleagues,⁷ acute mastoiditis exists when there are signs of AOM on otoscopy and local inflammatory findings over the mastoid process (e.g., pain, erythema, tenderness, auricular protrusion), or when the mastoid inflammatory changes coexist with radiographic or surgical findings of mastoiditis with or without evidence of AOM. Other authors insist on the concomitant presence of AOM, mastoid physical findings, and radiologic findings.⁸

Luntz and colleagues⁷ reported results of a multicenter retrospective study of 223 such patients that provided valuable insight into the process. Of patients, 28% were younger than 1 year at diagnosis, 38% were 1 to 4 years old, and 21% were 4 to 8 years old. Although one third of patients experienced signs and symptoms of AOM immediately preceding the mastoiditis, two thirds did not. Thirty percent of the patients had a history of recurrent AOM, and 5% (all of whom had recurrent AOM) had a prior episode of acute mastoiditis.

One third of the patients exhibited symptoms for 48 hours or less before diagnosis, and another third had symptoms for 2 to 6 days before presenting with acute mastoiditis. Spontaneous tympanic membrane perforation occurred in less than one fourth of patients; the tympanic membrane was bulging or erythematous in two thirds. Twenty-two percent of the patients presented with complications on admission, the most common of which was subperiosteal abscess (Fig. 140-1), followed by meningoencephalitis and occasional cases of other complications.

Figure 140-1. Axial temporal bone CT scan showing opacification of mastoid with preservation of bony septa. Note defect in cortical bone (white arrow) and postauricular swelling and fluid collection (black arrow).

Despite parenteral antibiotics, 8% of the patients who had been free of complications on admission developed complications of acute mastoiditis during hospitalization. The most common was subperiosteal abscess, but three patients developed intracranial complications, and two developed facial paralysis while receiving parenteral antibiotics. One third of patients required surgery because they had extracranial or intracranial complications on admission, failed to exhibit satisfactory clinical improvement, or developed complications despite adequate antibiotic treatment during hospitalization.

Bak-Pedersen and Ostri⁹ reviewed the records of 79 patients who underwent acute cortical mastoidectomy for acute mastoiditis. All patients had erythema and swelling and pain over the mastoid associated with a current or recent episode of AOM that did not improve after 24 to 48 hours of intravenous antibiotics. The average age in the series was 16 months, and the average duration from the onset of disease (AOM) until admission for acute mastoiditis was 9 days. Only one third of the patients exhibited an asymptomatic interval between AOM symptoms and the mastoiditis.

Both of the aforementioned studies established that acute mastoiditis is a disease of the very young. Also, they dispelled the classic notion that acute mastoiditis develops only after an asymptomatic period of 3 to 4 weeks.

Van Zuijlen and colleagues¹⁰ pointed out that in countries such as the Netherlands, where it is unusual to prescribe antibiotics as first-line treatment for AOM, the incidence of acute mastoiditis is considerably higher than in countries where antibiotics are routinely prescribed for AOM. Lower overall costs and reduced incidence of allergic reactions resulting from withholding antibiotics in routine AOM must be weighed against heightened risks of mastoiditis and other complications.

Coalescent Mastoiditis

Diagnosis

Symptoms of coalescent mastoiditis (purulent otorrhea, fever, toxicity, and ear pain) are the same as symptoms seen in patients with uncomplicated AOM. The strongest historic suggestion of coalescent mastoiditis is the chronology of the infection in which purulent drainage or significant otalgia persists for 2 or more weeks, recurs after 10 to 14 days, or significantly worsens after that time interval. As a group, children with coalescent mastoiditis look sicker and have more toxicity with higher temperature and more persistent fevers than children with AOM. Older children may be able to localize the pain to the postauricular area rather than the ear canal. Physical findings that are most helpful include mastoid tenderness to percussion, mastoid erythema, and sagging of the posterosuperior external auditory canal wall.

The clinician should order a complete blood count and hematologic studies followed by CT scanning, which can establish the diagnosis by documenting the breakdown of the bony cell walls and opacification of the pneumatized spaces (Figs. 140-2 and 140-3). If any suggestion of an intracranial complication exists, the clinician should obtain an enhanced MRI scan.

Figure 140-2. Axial temporal bone CT scan showing opacification of mastoid with loss of bony septa. Note defect in cortical bone and postauricular fluid collection (arrow).

Figure 140-3. Coronal temporal bone CT scan of patient in Figure 140-2. Note defect in cortical bone (arrow).

Chronic Mastoiditis

Etiology

Chronic mastoiditis can occur in association with a long-standing tympanic membrane perforation, with cholesteatoma, or as a complication from an infection after placement of a middle ear ventilating tube. As noted previously, ventilating tube mastoiditis tends to occur in young children who have experienced water contamination and have undergone cultures and treatment with multiple antibiotic drops and oral antibiotics. Mastoiditis with tympanic membrane perforation occurs when an episode of AOM with perforation pursues a course of chronic infection, rather than resolving or developing into coalescent mastoiditis. Chronic mastoiditis of this type can also begin when a long-established uninfected central perforation becomes infected and extends to the mastoid (Fig. 140-4).

Figure 140-4. Axial temporal bone CT scan showing opacification of middle ear (white arrow) and mastoid (black arrow).

Although cholesteatoma frequently remains uninfected for long periods, it tends to suppurate, form granulation tissue, and erode bone. When any type of mastoiditis causes continuous purulent drainage, there is little likelihood of complete resolution with antibiotics. Chronic mastoiditis requires surgical intervention to heal, and an infected cholesteatoma requires surgical ablation, regardless of duration. Complications in patients with chronic mastoiditis with tympanic membrane perforation can develop at any time, but often occur only after weeks or months of otorrhea. In contrast, cholesteatoma typically requires months or years to produce complications.

Masked Mastoiditis

Chronic otitis with granulation tissue formation and bone erosion can occur without otorrhea. It can persist despite a normal or near-normal tympanic membrane. This condition has been referred to as masked mastoiditis and usually occurs in patients who have received numerous courses of antibiotics. In this complication, the middle ear and much of the mastoid respond to the antibiotics, but a focal area of persistent infection somewhere in the mastoid does not. Patients experience chronic but not severe auricular and postauricular pain, slight but definite tenderness to percussion of the mastoid cortex, and CT scan evidence of a localized area of opacification in an otherwise normal mastoid. Surgical excision eliminates the symptoms.

Samuel and Fernandez¹⁴ described 21 cases of mastoiditis with retroauricular swelling and an intact tympanic membrane in a South African population (19 patients were <13 years old) in whom the duration of symptoms was shorter than that usually seen with coalescent mastoiditis. The predominant finding at mastoidectomy was granulation tissue filling the mastoid cavity and the antrum. The tympanic membrane was described as hyperemic, dull, bluish, bulging, or retracted. In addition to their mastoiditis, 10 patients had postauricular abscesses, 3 had Bezold’s abscesses, and 2 had facial nerve palsy. Four patients had cellulitis or abscess in the posterior fossa. Although these cases do not represent masked mastoiditis, they show the important fact that medically significant mastoiditis can exist without purulent otorrhea. There are two keys to the successful diagnosis and management of masked mastoiditis: (1) mastoid disease is not always reflected by the appearance of the tympanic membrane, and (2) chronic mastoiditis is a surgical condition, regardless of the appearance of the tympanic membrane. In this regard, the diagnosis and management of masked mastoiditis are no different from the diagnosis and management of mastoiditis with otorrhea emanating from other causes.

Postauricular Abscess

Postauricular abscess is the most common complication of mastoiditis. It is most often seen accompanying acute or coalescent mastoiditis in young children. The infection extends from the mastoid to the subperiosteal space; this usually occurs by direct extension subsequent to bone destruction or by phlebitis and periphlebitis of mastoid veins. The tiny pits in adult temporal bones that make up the cribriform area of the mastoid near the spine of Henle exist in newborns as a series of open channels between the interior of the mastoid and the cortex. Until these channels have closed, infection can pass directly from the mastoid to the subperiosteal space in these very young children. Regardless of how it starts, soft tissue infection leads to tissue necrosis and abscess formation. The surrounding soft tissue exhibits thickening, inflammation, erythema, tenderness, and fluctuation.

The diagnosis is usually obvious. Because only the upper part of the mastoid is pneumatized, the process develops in that upper portion, and the tissue edema and the abscess drive the auricle downward and laterally (Fig. 140-5). In the early stages, if fluctuation is not obvious, the clinician should use imaging studies or ultrasonography to document the presence of air within the soft tissue or an abscess cavity with its capsule (Figs. 140-6 and 140-7). When mastoiditis has produced an abscess, excision and drainage in conjunction with mastoidectomy is indicated. Only in the most unusual of circumstances would treatment by prolonged antibiotics and drainage of the abscess without mastoidectomy be appropriate.

Figure 140-5. Postauricular abscess associated with coalescent mastoiditis. Auricle is displaced laterally and inferiorly.

(From Harker LA. Cranial and intracranial complications of acute and chronic otitis media. In: Snow JB, Ballenger JJ, eds. Ballenger’s Otorhinolaryngology Head and Neck Surgery. 16th ed. Hamilton, Ontario: Decker; 2003.)

Figure 140-6. Axial temporal bone CT scan (soft tissue) showing abscess cavity with gas (arrow). Note cortical defect (arrowhead) and mastoid opacification and loss of bony septa (star).

Figure 140-7. Axial temporal bone CT scan (soft tissue) with contrast enhancement. Note postauricular abscess with enhancing capsule (arrow).

Bezold’s Abscess

In his 1913 text, Diseases of the Ear, Kerrison¹⁵ described a Bezold abscess as a condition:

The cervical infection develops into an abscess in the upper neck deep to the sternocleidomastoid muscle. Bezold’s abscess can also develop without any erosion or penetration of the inner and outer cortex of the mastoid if phlebitis and periphlebitis propagate the infection to the same area. Because infants have limited mastoid pneumatization, Bezold’s abscess occurs more commonly in older children in whom pneumatization has extended into the mastoid tip and in adults who have either chronic mastoiditis or cholesteatoma.

Often, the diagnosis of Bezold’s abscess is not considered initially in young patients with deep, tender, upper cervical masses because inflamed lymph nodes from many causes are so common. If the history and physical examination do not reveal a specific etiology, the clinician should obtain a CT scan to identify or rule out a mastoid source (Figs. 140-8 through 140-11).

Figure 140-8. Axial temporal bone CT scan showing opacification of external auditory canal and middle ear (white arrow). Also note the destruction of bony septa in the inferior part of the mastoid process (black arrow).

Figure 140-9. Axial temporal bone CT scan of the patient in Figure 140-8 at level of the root of styloid process (white arrow) showing destruction of bone at the anterior aspect of mastoid tip (black arrow).

Figure 140-10. CT scan of patient in Figure 140-8 showing Bezold’s abscess with enhancing capsule (arrows) at level of the mastoid tip.

Figure 140-11. CT scan of patient in Figure 140-8 showing the abscess cavity (arrows) extending lower in the neck to level of hyoid bone (arrowhead).

The recommended treatment is complete surgical excision of the mastoid pathology, drainage of the abscess, and removal of any associated granulation tissue. The surgeon should use bipolar electrocautery, copious suction irrigation, and coarse diamond burs to allow him or her to visualize the pathology adequately and exenterate all of the diseased cells thoroughly. The surgeon should drain the mastoid and the abscess cavity.

Temporal Root Abscess

The soft tissues above and even anterior to the auricle can become infected and form an abscess from suppuration that involves the cells of the zygomatic root of the mastoid (temporal root of the zygoma). Similar to Bezold’s abscesses, temporal root abscesses can form by direct extension via bone erosion through epitympanic temporal root cells or via phlebitis. The clinical picture may be confusing because abscesses in this location are rare. CT scanning is always recommended to rule out mastoiditis as the source. Surgical drainage is recommended.

Petrous Apicitis

Each petrous apex is undeveloped (sclerotic), contains marrow, or exhibits a variable degree of pneumatization. Pneumatization develops in only approximately 30% of temporal bones.¹² Much has been written about the different cell tracts that extend into and pneumatize the petrous apex. Basically, the cells extend into the apex above (supralabyrinthine) (Fig. 140-12), behind (retrolabyrinthine) (Fig. 140-13), beneath (infralabyrinthine) (Fig. 140-14), or in front of the labyrinth (anterior labyrinthine). Petrous apicitis is essentially mastoiditis that occurs in the petrous apex. It is rare because infection in sclerotic apices or petrous apices containing marrow is uncommon, and because the prevalence of pneumatization is low. Petrositis develops by direct extension of a mastoid infection, but the mastoid may respond to medical or surgical treatment without apical resolution. Just as there can be disjunction between the state of infection in the middle ear and the mastoid, the same holds true between the mastoid and the petrous apex.

Figure 140-12. A and B, Petrous apex pneumatization via supralabyrinthine cell tract at level of vestibule (A) and posterior semicircular canal (B).

(From Harker LA. Cranial and intracranial complications of acute and chronic otitis media. In: Snow JB, Ballenger JJ, eds. Ballenger’s Otorhinolaryngology Head and Neck Surgery. 16th ed. Hamilton, Ontario: Decker; 2003.)

Figure 140-13. Petrous apex pneumatization via retrolabyrinthine cell tract at two levels of internal auditory canal and vestibule.

(From Harker LA. Cranial and intracranial complications of acute and chronic otitis media. In: Snow JB, Ballenger JJ, eds. Ballenger’s Otorhinolaryngology Head and Neck Surgery. 16th ed. Hamilton, Ontario: Decker; 2003.)

Figure 140-14. Petrous apex pneumatization via infralabyrinthine cell tract in right temporal bone at level of internal auditory canal.

(From Harker LA. Cranial and intracranial complications of acute and chronic otitis media. In: Snow JB, Ballenger JJ, eds. Ballenger’s Otorhinolaryngology Head and Neck Surgery. 16th ed. Hamilton, Ontario: Decker; 2003.)

The pathology of the infection can mirror that seen in coalescent mastoiditis, with dissolution of thin cellular septa and coalescence, or it can resemble the formation of granulation tissue with chronic bone erosion seen with chronic mastoiditis. Rarely, there is extension of cholesteatoma to the apex. Imaging studies usually include CT and MRI. CT scan shows the bony details of the septa of the air cells and the size and contour of the entire apex (Figs. 140-15 through 140-20). MRI differentiates marrow from mucus or CSF. CT and MRI studies are essential to establish when there is opacification of the air cells in the petrous apex under suspicion, as opposed to asymmetric pneumatization. When one petrous apex is well pneumatized, a small sclerotic or marrow-containing apex on the opposite side can be misinterpreted as a pneumatized apex opacified by fluid or infection.

Figure 140-15. Axial temporal bone CT scan showing left petrous apicitis. Note opacification of the petrous apex with destruction on bony septa (star). A dehiscence of the carotid canal and narrowing of the petrous carotid artery (arrow) also are seen on this contrast study.

Figure 140-16. Axial non–contrast-enhanced T1-weighted MRI of the patient in Figure 140-15 showing mastoid opacification (star). The left petrous apex is also opacified (triangle) in contrast to the bright fat signal seen on the right side. Note narrow caliber of left internal carotid artery (short arrow) compared with internal carotid artery on the right (arrows).

Figure 140-17. Axial contrast-enhanced T1-weighted MRI of the patient in Figure 140-15 showing low signal in left petrous apex with peripheral contrast enhancement (black arrowhead) consistent with inflammation. Note narrow caliber of left internal carotid artery (short arrow) compared with internal carotid artery on the right (arrows).

Figure 140-18. Coronal contrast-enhanced T1-weighted MRI of the patient in Figure 140-15 showing low signal in left petrous apex with peripheral contrast enhancement (black arrow). Note enhancement of dura and temporal lobe adjacent to petrous apex (white arrowhead).

Figure 140-19. MR angiography of the patient in Figure 140-15 showing narrowing of left petrous internal carotid artery (arrow).

Figure 140-20. MR angiography of the patient in Figure 140-15 showing normal caliber of internal carotid artery after resolution of narrowing (arrow).

The symptoms of infection in the petrous apex reflect the innervation of the air cells and the structures adjacent to the apex itself. Although increased pressure within the mastoid air cell system causes pain in the region of the mastoid and the ear itself, pressure within the petrous apex usually results in pain referred to the retro-orbital area or deep within the skull. Patients with petrous apicitis can have symptoms that reflect infection in the middle ear and mastoid, and symptoms emanating from the apex. The most common symptoms are deep or retro-orbital pain (from irritation of the contiguous trigeminal ganglion in Meckel’s cave), paralysis of cranial nerve VI as it passes through Dorello’s canal abutting the petrous apex, dysfunction of cranial nerves VII and VIII, or labyrinthitis. In 1904, Gradenigo described the triad of retro-orbital pain, sixth cranial nerve paralysis, and otorrhea, since known as Gradenigo’s syndrome.¹² Only a few patients with petrous apicitis exhibit the full triad today.

The treatment of the apicitis depends on the duration, severity, and presence or absence of associated complications. Because of the anatomic complexities and the necessity to work around the labyrinth and the carotid artery, petrous apex air cell disease cannot be excised. Established drainage and prolonged antibiotics are an integral part of treatment, with or without surgery. When there is obvious necrotic bone, surgical drainage is a necessary adjunct to intravenous antibiotic therapy. When there is adequate access and widespread disease, even partial apicectomy can reduce the bacterial load so that antibiotics and host defenses can control the disease.

The surgical approach to the apex depends on available air cell pathways and the portion of the apex involved. In some temporal bones, access can be gained by a route posterior to the posterior semicircular canal; in others, the best route is subcochlear, infralabyrinthine. In a small percentage of temporal bones, there is an opportunity to provide drainage via cells extending over the superior semicircular canal and through the “hole in the doughnut,” working through the center of the superior semicircular canal. Air cell tracts containing granulation tissue can usually be followed into the apex. The original anterior petrous apex drainage procedure described by Lempert necessitated a radical mastoidectomy and is rarely used today. Occasionally, with evidence of osteitis or abscess formation in the apex, and limited or inadequate access via the existing air cells pathways, the middle cranial fossa approach can provide access for exposure, culture, and irrigation.

Labyrinthine Fistula

Labyrinthine fistula represents an erosive loss of the endochondral bone overlying the semicircular canals without loss of perilymph (distinguished from perilymphatic fistula, discussed elsewhere in this text). This loss of the overlying protective bone allows pressure or mass-induced motion of the underlying endosteum, perilymph, and, by contiguity, endolymphatic compartment, evoking vestibular and sometimes auditory symptoms. Most labyrinthine fistulas involve only the lateral semicircular canal. In a few instances, these erosions expose the superior or posterior semicircular canal, the vestibule, or the cochlea.

This bone resorption is almost exclusively secondary to cholesteatoma, and it occurred in 7% of the cholesteatomas in the large series by Gersdorff and Nouwen.¹⁶ Higher percentages have been reported, but the actual incidence is hard to determine. Most reports of labyrinthine fistulas caused by cholesteatoma are from tertiary care referral centers that include many large or previously operated cases, perhaps biasing the prevalence. Studies reviewing suppurative complications of otitis media usually do not include all cases of labyrinthine fistulas because many are not infected, or do not cause significant symptoms and are detected only at surgery. The mechanisms by which cholesteatoma causes this bony erosion are not fully understood, and are the subject of other chapters. Suffice it to say, first there is demineralization of the dense endochondral bone, and then loss of bone substance, so that the perilymph and its surrounding endosteal membrane have less and less bone between them and the overlying cholesteatoma matrix. As the bone becomes thin, it can be observed at surgery as a “blue line” parallel to the underlying semicircular canal lumen because the illuminating light along the blue line is no longer reflected off the dense bone, but absorbed into the underlying fluid.

Manolidis¹⁷ reviewed the records of 111 inner-city patients in Texas with labyrinthine fistulas, and assessed their coexisting complications. Two associations were prominent. The facial nerve was involved with cholesteatoma or functionally damaged by a cholesteatoma in 60% of the patients, and dehiscences of the tegmen occurred in 39%. Most of these cases were reoperations, with an average of 2.6 operations per patient. Although the data are biased by the number of revision operations, surgeons should always assume that the bony fallopian canal is eroded and the facial nerve is in direct contact with cholesteatoma whenever a lateral semicircular canal fistula is suspected, and they should consider the possibility of defects in the tegmen in such patients, especially patients with previous mastoid surgery.

Most patients present with signs and symptoms of the underlying cholesteatoma. Symptoms attributable to labyrinthine fistulas are primarily vestibular. Patients recount brief periods of imbalance, dysequilibrium, or vertigo, but have normal equilibrium most of the time. Some may be able to recall causing momentary imbalance by pushing on their external ear canal, such as with a washcloth, or have noticed that loud sounds provoke brief imbalance (Tullio’s phenomenon).

After a suspicious history, the principal diagnostic maneuver is the fistula test. The clinician occludes the external auditory canal of the ear with the pneumatic otoscope, and then gently increases and decreases the external auditory canal pressure so that the changes are transmitted from the external auditory canal to the middle layer and mastoid air cells system via an intact or perforated tympanic membrane. During the procedures, the patient is asked to fix the eyes in the cardinal position, and the physician observes the patient’s eyes for any deviation from that cardinal position. In the case of a normal ear, no eye motion or symptoms are provoked. With a lateral canal fistula, positive external auditory canal pressure causes compression of the lateral semicircular canal endosteum, and utriculopetal endolymph flow resulting in conjugate deviation of the eyes away from the side of compression, a positive fistula sign. Negative external auditory canal pressure results in conjugate deviation toward the ear under the test. The patient may subjectively note motion of the environment or slight nausea during the pressure alterations.

The fistula test results are reported as positive in only 55% to 70% of patients with lateral canal erosion, but if positive, they are highly reliable and facilitate surgical planning and execution.¹⁸ CT scanning (Figs. 140-21, 140-22, and 140-23) also provides preoperative evidence suggesting a labyrinthine fistula, and images in the bone algorithm usually document the bone erosion of the lateral semicircular canal and show other signs suggestive of cholesteatoma.

Figure 140-21. Axial temporal bone CT scan showing soft tissue density in a mastoid cavity eroding into horizontal semicircular canal (arrow).

Figure 140-22. Axial temporal bone CT scan of the patient in Figure 140-21 showing erosion of anterior limb of superior semicircular canal (arrowhead).

Figure 140-23. Coronal temporal bone CT scan of the patient in Figure 140-21 showing erosion of horizontal semicircular canal (arrow).

The treatment of labyrinthine fistulas addresses the underlying cholesteatoma. When there are other, more grave complications, their management supersedes that of the fistula. The decision whether to remove the external auditory canal and perform an open cavity mastoidectomy or to retain the canal wall in a canal wall up technique is made on the basis of the surgeon’s ability to eradicate the cholesteatoma completely, the degree of pneumatization of the temporal bone (adequate access), and the surgeon’s confidence that he or she can completely remove the cholesteatoma matrix from the fistula site. Whether the canal wall up or canal wall down technique is used, the operation is completed, leaving the fistula site for last.

The surgeon identifies the blue line of the actual fistula and the adjacent thinned layer of bone on either side of it. The plane separating the matrix and the endosteum is developed, and under high magnification with good hemostasis a flat dissector wider than the semicircular canal itself is used to peel the matrix gently from the underlying endosteum. A fine microsuction elevates the cholesteatoma and facilitates visualization and removal. If the endosteum is torn, it is best to replace the adjacent matrix and terminate the procedure. If it is successfully removed, a small piece of tissue or a shaped cap of bone is placed over the site and secured in place with fibrin glue or packing. In some cases, especially with large fistulas, it may be best to perform a canal wall down procedure and leave the fistula covered by matrix, which later forms the mastoid cavity lining.

Removal of the fistula generally improves the vestibular symptoms, although symptoms related to pressure transmitted from the external auditory canal can persist for some time. Because there is no protective bone to prevent compression of the endolymphatic compartment by pressure changes in the external auditory canal, a positive fistula sign persists until there is a regrowth of bone. Loss of hearing in the involved ear and worsening of existing hearing are the risks that always accompany the procedure, but these have been reported to occur in less than 20% of carefully managed fistula cases.⁹

Facial Nerve Paralysis

Facial nerve paralysis can result from AOM, COM without cholesteatoma, or cholesteatoma. Bacteria reach the nerve because of congenital dehiscences of the bony fallopian canal or via erosion with granulation tissue or cholesteatoma. Facial nerve function is lost with inflammatory pressure or suppurative neurapraxia. If the edema persists, axonotmesis can ensue.

In young children, facial paralysis that is caused by AOM is frequently incomplete and probably occurs only in infants with congenital dehiscence of the fallopian canal in the middle ear adjacent to the stapes. Facial weakness in these cases rarely lasts longer than 3 weeks even when complete paralysis is present.

Facial nerve paralysis caused by COM without cholesteatoma also usually affects the horizontal portion of the facial nerve near the stapes.¹⁹ In these cases, the clinical course of the paralysis is more likely to be prolonged, with a gradual progression from slight weakness to full paralysis; sometimes the progression to complete paralysis is rapid (Figs. 140-24 and 140-25). Facial nerve paralysis caused by cholesteatoma can produce extensive erosion of the horizontal segment of the fallopian canal—especially common in large, uninfected, primary acquired cholesteatomas. An erosive cholesteatoma can expose the facial nerve anywhere in the temporal bone and cause paralysis. In these cases, the onset of the paralysis is usually gradual, and sometimes the progression is so slow that patients do not seek medical attention for months. When the onset of facial paralysis is this slow, the paralysis is more likely to persist after surgical treatment.

Figure 140-24. Coronal temporal bone CT scan showing cholesteatoma (arrow) eroding the facial nerve canal (arrowhead).

Figure 140-25. Coronal T1-weighted MRI of the patient in Figure 140-24 showing cholesteatoma (arrow).

When facial paralysis is caused by AOM, appropriate antibiotic therapy for AOM may be adequate treatment, although myringotomy with evacuation of the purulent material and reduction of the numbers of bacteria is recommended. When facial nerve paralysis follows chronic suppurative otitis media (with or without cholesteatoma), the surgeon should remove the infection surrounding the nerve as part of the mastoidectomy. The surgeon gradually approaches the granulation tissue or cholesteatoma overlying the nerve from the proximal and distal portions of the nerve, which are uninvolved by the chronic infection. Diamond burs should be used to remove carefully the bone of the fallopian canal on both sides of the diseased portion. The surgeon uses a flat blunt instrument to dissect the chronic inflammatory tissue from the nerve while elevating the diseased tissue with a small suction tip. It may be necessary to use sharp dissection to separate the inflammatory tissue from the epineurium. The outcome for surgical decompression of the facial nerve caused by chronic suppurative otitis media primarily depends on whether the nerve has undergone complete degeneration before surgery.

Acute Suppurative Labyrinthitis

Bacterial invasion of the labyrinth is always promptly followed by total loss of auditory and vestibular function (Figs. 140-26 through 140-29). Usually, AOM extends into the labyrinth through a weakened or dehiscent oval window membrane, as occurs in congenital labyrinthine deformities such as Mondini’s deformity and enlarged vestibular aqueducts, and in individuals who have undergone stapes surgery. Although it is not proven, suppurative labyrinthitis may be a common mechanism for unilateral anacusis in children with Mondini’s deformity. These children are at additional risk. The foramina of the internal auditory canal opening into the medial aspects of the labyrinth may also be weak or dehiscent, and those foramina and the cochlear aqueduct can permit bacterial infection to progress from the labyrinth to the meninges or vice versa. It is unknown how frequently suppurative labyrinthitis causes meningitis, or how often meningitis subsequently causes bacterial labyrinthitis, but both probably occur, especially in the special population of children with congenital labyrinthine abnormalities.

Figure 140-26. Axial temporal bone CT scan showing chronic mastoiditis with opacification of mastoid, external auditory canal, and middle ear. Note erosion and involvement of vestibule (arrowhead).

Figure 140-27. Coronal temporal bone CT scan of the patient in Figure 140-26. Note the erosion and involvement of the fundus of the internal auditory canal (arrowhead).

Figure 140-28. Axial contrast-enhanced T1-weighted MRI of the patient in Figure 140-26 showing enhancement of middle ear, vestibule, and internal auditory canal (arrowhead).

Figure 140-29. Coronal contrast-enhanced T1-weighted MRI of the patient in Figure 140-26 showing enhancement of temporal lobe dura (white arrowhead) and internal auditory canal (black arrowhead).

Direct bacterial invasion of the labyrinth through a cholesteatomatous lateral semicircular canal fistula is another cause for acute suppurative labyrinthitis. In this situation, infected granulation tissue beneath the cholesteatoma matrix lies directly on the endosteal membrane and its underlying perilymph. The bacteria causing the labyrinthitis are those of the underlying AOM or the cholesteatoma.

The diagnosis of acute suppurative labyrinthitis is clinical. Tinnitus and dizziness rapidly progress to whirling vertigo, pallor, diaphoresis, nausea, and vomiting. Brisk labyrinthine nystagmus directed toward the opposite ear accompanies the vertigo. After the first several hours, the spontaneous vertigo and nystagmus gradually begin to abate. Symptomatic improvement continues during the next few days. Over the next 2 to 3 weeks, central nervous system compensation occurs, and normal or near-normal balance is restored. Tinnitus often abates, but all hearing is lost.

No specific diagnostic studies are necessary when the typical clinical picture develops in a patient with AOM or COM and a predisposing condition. Although there is no possibility of reversing the clinical course, appropriate antibiotic treatment for 10 days is recommended to eradicate the labyrinthine infection and to prevent propagation to the meninges. Other therapeutic measures are dictated by the underlying otitis, but labyrinthectomy is unnecessary in labyrinthitis secondary to AOM.

Encephalocele and Cerebrospinal Fluid Leakage

Encephalocele (brain hernia, brain fungus, meningoencephalocele) and CSF leakage are associated with cranial or intracranial complications when they coexist with AOM or COM. Three different clinical patterns can occur.

Spontaneous CSF leakage sometimes develops in conjunction with defects in the tegmen tympani or, less commonly, the tegmen mastoideum. May and colleagues,²⁰ Lundy and associates,²¹ and others have reported this in more than 50 patients who have not undergone previous otologic surgery. Of such patients, 70% to 80% are older than 45 years. The defects range in diameter from 2 mm to 2 cm, and sometimes are multiple. Usually, an encephalocele protrudes through the defect (Figs. 140-30 and 140-31). There is no agreement as to why the dura breaks down and allows protrusion of cerebral contents and escape of CSF in these older patients, although Jackson and colleagues²² have suggested that aging, increased intracranial pressure, low-grade inflammation, arachnoid granulation, and irradiation can play a part. Patients frequently visit their physicians because of hearing loss secondary to reduced ossicular motion from the middle ear fluid or the encephalocele. Myringotomy and placement of a ventilating tube manifest profuse watery otorrhea that tests positive for CSF. Other patients present with signs and symptoms of meningitis, and many of these patients have experienced one or more previous bouts of that disease.

Figure 140-30. Coronal temporal bone CT scan showing encephalocele (star) going through a tegmen defect (arrow).

Figure 140-31. Coronal T2-weighted MRI of the patient in Figure 140-30 showing encephalocele (arrows).

Encephalocele and CSF leakage secondary to COM occur when a cholesteatoma and granulation tissue erode through the bony plates separating the mastoid from the temporal lobe, the cerebellum, and the dura adjacent to the bone. The mastoid and epitympanic tegmen are involved more frequently than the cerebellar plate. A cholesteatoma needs to be present for many months to years to cause this degree of bone erosion, cerebral prolapse, and dural erosion.

Traumatic encephalocele and CSF leakage is the most common pattern. Although a few of these cases occur because of temporal bone fracture, most are a consequence of surgical trauma, such as when portions of the tegmen or cerebellar plates have been surgically removed, and the dura is exposed and sometimes traumatized. In these situations, the disease process and the surgery can contribute to the bony and dural trauma that facilitates the development of an encephalocele, CSF leakage, and intracranial complications. Manolidis²³ reported a series of 29 such patients from an inner-city population. More than 80% of the patients had cholesteatoma, and half had undergone one or two previous operations. All had dural herniations and encephaloceles, but only one had CSF leakage. Labyrinthine fistulas, suppurative intracranial complications, and associated facial paralysis were noted.

Jackson and colleagues²² have written an excellent review of this subject. The size of the bony defect and the volume of herniated brain are two of the important factors in choosing a surgical approach. Small defects are managed adequately through the mastoid; multiple and larger defects are repaired by the middle cranial fossa approach in combination with mastoid exposure.

The middle fossa approach provides excellent exposure of the tegmen defect and access to repair the dural defect. A temporalis fascia graft is used to repair the dura, which is often quite attenuated. The bony defect can be repaired with a split calvarial bone graft taken from the inner table of the craniotomy flap. It is fashioned larger than the bony defect, and is placed on the intracranial surface so that it can support the brain. Another technique to repair the tegmen defect is the use of hydroxyapatite cement. The floor of the middle fossa can be reconstituted, and a watertight seal can be obtained. Care must be taken to avoid cement contact with the ossicles, or a conductive hearing loss results.

Meningitis

A dramatic reduction in the incidence of meningitis caused by AOM and COM has occurred because of immunizations against the common causative organisms. Two decades ago, H. influenzae and S. pneumoniae caused nearly all cases of otogenic meningitis. After H. influenzae type B vaccination became part of routine pediatric immunizations in the United States in the early 1980s, H. influenzae meningitis dramatically decreased and has now almost disappeared. Today, pneumococcal conjugate vaccine PCU-7 (Prevnar), the multivalent pneumococcal vaccine effective in young children, is also a routine pediatric immunization in the United States, and similar reductions in otogenic streptococcal meningitis are occurring in the most susceptible age group—younger than 2 years old. In any given country, the incidence of meningitis as a complication of suppurative otitis is inversely proportional to the prevalence of immunizations against these two bacteria.

In the past, meningitis was the most common complication of AOM and COM. In the series by Gower and McGuirt²⁴ of 100 consecutive patients with intracranial complications of AOM and COM, 76 had meningitis, and 53 of those patients were younger than 2 years. In that age group, most cases occurred by hematogenous dissemination of infection during AOM. Sometimes, these patients are not tabulated in reports documenting the complications of otitis,^1,25 and in those reports the frequency of otitis-induced meningitis is low.

Conditions that allow CSF to gain access to the middle ear cavity predispose to the development or recurrence of bacterial meningitis. CSF otorrhea is common after lacerations of the dura by longitudinal temporal bone fractures. Congenital defects of the tegmen, with or without encephalocele, can also be accompanied by CSF leakage into the epitympanum and middle ear, as can unrecognized injury to the dura of the posterior or middle cranial fossae during mastoid surgery. Patients with syndromic or nonsyndromic congenital stapes fixation, Mondini’s dysplasia, and enlarged vestibular aqueducts also are at risk for a bacterial middle ear infection to spread to the CSF. The pathway can be obvious, such as when a “perilymph gusher” is discovered during stapes surgery, or it can be more subtle, when there are microscopic disruptions of the continuity of the oval or round windows, the internal auditory canal, and the cochlear aqueduct. Meningitis can occur even in individuals with normal middle ear and labyrinthine anatomy if AOM complicates conditions such as traumatic stapes dislocation or perilymphatic fistula and then progresses on to acute suppurative labyrinthitis.

The predominant symptoms of meningitis are a generalized severe headache, nausea, and social withdrawal. The patient tends to lie quietly, with photophobia and general hyperesthesia. The patient’s level of consciousness may vary from normal to unresponsive. Fever is universal, high, and sustained. Nuchal rigidity and pain with attempted flexion of the neck are ominous cardinal signs, and abnormal abdominal reflexes strengthen the clinical impression. In Brudzinski’s sign, passive flexion of the head on the chest is followed by involuntary flexion of both thighs and both legs. In Kernig’s sign, the patient is in the supine position, and the thigh is flexed to a right angle, and attempts at passive extension at the knee produce pain and resistance owing to spasm of the hamstring muscles. Funduscopic examination may reveal papilledema.

Whenever meningitis is suspected, a CT scan can rule out the presence of brain abscess, cerebritis, or subdural empyema, and determine that it is safe to perform lumbar puncture (i.e., intracranial pressure is not inordinately increased). CSF from the lumbar puncture is examined for intrathecal pressure, cells, bacteria, glucose, protein, chloride, and other factors. CSF pressure is increased early in the course of the disease, and protein and glucose concentrations increase compared with serum values as it progresses, but bacteria are not present until late in the disease.

When meningitis is caused by AOM or suppurative labyrinthitis, myringotomy and appropriate antibiotics are adequate, and no surgery is indicated. When meningitis develops from COM and mastoiditis, however, the mastoid must be exenterated. When otogenic meningitis is associated with a profound ipsilateral sensorineural hearing loss, a route of infection to the meninges through the labyrinth is apparent. If the sensorineural function in the affected ear remains at the patient’s premeningitis baseline, the route was extralabyrinthine. Some patients with severe AOM experience a partial sensorineural hearing loss because of associated serous labyrinthitis. This partial loss may be reversible. Although the patient has already had a CT scan before the lumbar puncture, an enhanced MRI study should be obtained to rule out the presence of any additional intracranial complications (Fig. 140-32). The neurologic condition of the patient determines the timing of the surgery, and the mastoidectomy should be performed as soon as the patient is stable. Meningitis is one of the gravest complications of acute or chronic otitis, and it seems that it is more lethal when caused by COM and mastoiditis than when it is a hematogenous complication of AOM in the first 2 years of life.

Figure 140-32. Contrast-enhanced coronal MRI showing dural enhancement (arrowheads) caused by otogenic meningitis.

(From Head and Neck Archive, Advanced Medical Imaging Reference Systems [AMIRSYS], Salt Lake City, UT. Accessed January 2003.)

Brain Abscess

The incidence and mortality of intraparenchymal brain abscesses have decreased considerably, and almost all reports in the past 2 decades are from centers outside North America and Western Europe. Excellent reports from Africa and Asia using new imaging techniques have documented improvements in diagnosis and therapy, however, and have clarified some aspects of surgical treatment. The series by Yen and colleagues²⁶ of 122 consecutive patients seen in a Taiwan hospital between 1981 to 1994 revealed that otogenic causes were the third most common cause of intraparenchymal brain abscess, exceeded only by causes associated with cyanotic congenital heart disease and abscesses resulting from head injury or neurosurgery. Seventy-five percent of abscesses occurred in male patients—principally individuals in the lower socioeconomic classes. In the 1990s, four reports from India, Turkey, and South Africa discussed 149 patients with otogenic brain abscesses.^1,2,27,28 Abscesses from AOM and COM were almost always found on the same side as the otitis and occurred nearly equally in the temporal lobe and cerebellum. Almost three fourths were secondary to cholesteatoma, 50% occurred in the second decade of life, and two thirds affected male patients.

A brain abscess begins when bacteria propagate in and around venous channels leading from the mastoid into the adjacent brain parenchyma. The first event after the arrival of bacteria into the cortex or white matter is the migration of polymorphs into local capillaries with endothelial swelling and focal cerebritis. At this stage, the disease can be successfully managed by intravenous antibiotics alone. With more time, the tissue becomes edematous, hemorrhagic, and necrotic, and the abscess is formed. Brain abscesses may vary greatly in size, often have an irregular shape, and frequently are multilocular. At first, the capsule is poorly defined, but over time it becomes firmer and can easily be stripped from the underlying edematous brain.²⁹

In addition to symptoms and signs reflecting general intracranial sepsis, cerebellar abscess is often accompanied by coarse horizontal nystagmus, dysmetria, dysdiadochokinesia, or action tremor. Temporal lobe abscess (Figs. 140-33 through 140-36) can cause homonymous visual field defects, contralateral hemiparesis, and other focal signs listed later for subdural empyema. The physician should examine the patient and the imaging studies looking for other intracranial complications because two thirds of patients with intraparenchymal abscesses have more than one intracranial complication.²⁷

Figure 140-33. Axial T2-weighted MRI showing left mastoiditis and petrous apicitis (arrows) as high signal in mastoid and petrous apex.

Figure 140-34. Axial contrast-enhanced T1-weighted MRI of the patient in Figure 140-33 showing left temporal lobe abscess with enhancing capsule (arrow).

Figure 140-35. Axial T2-weighted MRI of the patient in Figure 140-30 showing abscess cavity and surrounding edema (arrow).

Figure 140-36. Coronal enhanced T1-weighted MRI of the patient in Figure 140-33 showing enhancing tissue in left mastoid (white arrow) and temporal lobe abscess with enhancing capsule (black arrow).

The physician should immediately begin the administration of broad-spectrum intravenous antibiotics directed at aerobic and anaerobic organisms. If imaging studies suggest no other complications, and the patient’s condition is stable, neurosurgical drainage or abscess excision is performed within the first 24 hours of admission and is followed immediately by mastoidectomy, performed through a separate surgical field. If this course is followed, mortality has decreased to approximately 10%.

Subdural Empyema

Subdural empyema is a fulminating purulent infection that develops between the dura and the pia arachnoid membranes, and represents one of the most immediate of neurosurgical emergencies. It constitutes only about 20% of all cases of localized intracranial bacterial infection, and an otologic etiology is uncommon compared with bacterial contamination (from trauma or a neurosurgical operation), suppurative sinus disease, and meningitis. At least two thirds of the cases occur in men, and most occur in the second decade of life. The abscess usually begins by direct spread from adjacent infected bone or by retrograde venous propagation. When infection enters the subdural space, pus forms rapidly and spreads widely, and thrombophlebitis of cortical veins is virtually guaranteed. Swelling, necrosis, and infarction of the cortex accounts for many of the clinical features and explains how a barely detectable thin layer of subdural pus can cause such devastating consequences as increased intracranial pressure, focal signs, and seizures.³⁰

Clinically, a patient with subdural empyema exhibits a cascade of symptoms including a severe headache, the earliest and the most persistent symptom. The patient’s temperature increases dramatically as the disease progresses. General malaise, chills, and nuchal rigidity indicate that the patient is becoming seriously ill. After an unpredictable period, the patient’s level of consciousness may abruptly decline, and focal signs and symptoms may develop. Most patients with left-sided collections develop aphasia and a progressive contralateral hemiparesis. Paralysis of conjugate gaze to the contralateral side and deviation of the eyes toward the side of the lesion are also common. Jacksonian seizures are common at this stage, and papilledema may be evident. In patients with posterior fossa collections, localizing signs are often absent, but marked neck stiffness and papilledema are always present. The entire clinical picture of subdural empyema can evolve in a few hours or can take 10 days to develop.

In a well-developed subdural empyema, a contrast-enhanced CT scan shows a crescent-shaped, low-density collection of pus displacing the brain away from the inner table of the skull, with enhancement of the adjacent edge of the cortex. The scan may appear normal early in the course of the disease. When this happens, the clinician should obtain a contrast-enhanced MRI study or repeat the CT scan after a suitable interval. Lumbar puncture is dangerous and is contraindicated because it can precipitate transtentorial coning with elevated intracranial pressure. If the CT scan fails to detect the lesion, and focal signs are absent, lumbar puncture may be unavoidable to rule out meningitis.

Emergency neurosurgical drainage and appropriate antibiotic therapy are necessary. Survival is related to the level of consciousness at the time of surgery. The presence of localizing signs in any patient with COM whose level of consciousness is declining requires immediate and decisive action.

Subdural empyema can also develop in neonates as a complication of meningitis. In 30% of cases of H. influenzae meningitis, a collection of fluid develops in the subdural space (usually bilaterally) that varies from 5 to 100 mL.³¹ This problem is less common after meningitis from other organisms and is decreasing in frequency because universal immunization against H. influenzae has dramatically reduced the incidence of meningitis. Uninfected subdural collections after meningitis are called subdural effusions. If bacteria are evident on direct examination of the fluid, the collections are called infected subdural effusions, and if the fluid is grossly purulent, they are classified as subdural empyemas. Subdural collections from meningitis secondary to COM that require otologic attention are rare in the neonatal age group.

Epidural Abscess

Epidural abscess results from bone erosion caused by cholesteatoma, granulation tissue, or coalescence. In addition to the bone erosion, an intense inflammatory response to the infection results in granulation tissue formation and forms an abscess between the temporal bone and the underlying dura mater. The involved dura thickens in response to its contact with granulation tissue on its surface (pachymeningitis). Although it can occur as the only complication of chronic mastoiditis, epidural abscess is frequently associated with lateral sinus thrombophlebitis, meningitis, and cerebritis or brain abscess. Rarely, epidural abscess can result from acute otitis and mastoiditis in the same way as was described for lateral sinus thrombosis.

Most patients experience deep mastoid pain, but there are no signs or symptoms specifically attributable to epidural abscess, and many of the cases without associated complications are discovered only at surgery. If it is large enough, the abscess can be detected on contrast-enhanced CT or MRI scans as a fluid-filled cavity between the temporal bone and the enhanced dura. Surgery is the only recommended treatment. The surgeon performs the type of mastoidectomy that is appropriate for the underlying otitis and mastoiditis.

After removal of the cortex, the surgeon should progressively exenterate the air cells, proceeding from lateral to medial, and from regions with less disease to regions with more disease. When the locus of pathology is the cerebellar plate, the surgeon should smooth the tegmen mastoideum and the tegmen tympani first, and then the thin posterior aspect of the bony external auditory canal; the tip cells should be removed. This removal maximizes exposure and hemostasis. Then the surgeon approaches the diseased area along the cerebellar plate from the superior, the inferior, the lateral, and finally the medial direction, removing the overlying bone down to a thin plate. Because the dura is thickened by the infection, blunt flat instruments such as a Freer elevator or large curets can safely scrape the granulation tissue from the abscess cavity and identify the most centripetal extent of the abscess. The surgeon should remove all of the bone overlying the abscess using diamond burs, rongeurs, or curets until healthy dura without granulation tissue is evident on all margins of the abscess. When the abscess involves the tegmen, the order is changed, and the surgeon should complete the surgery in the other areas first, addressing the tegmental abscess last.

Lateral Sinus Thrombosis

Thrombosis of the lateral sinus usually forms as an extension of a perisinus abscess that develops after mastoid bone erosion from cholesteatoma, granulation tissue, or coalescence (Figs. 140-37 and 140-38).³² The perisinus abscess exerts pressure on the dural outer wall of the sinus leading to necrosis. The necrosis extends to the intima and attracts fibrin, blood cells, and platelets. A mural thrombus forms, then becomes infected, enlarges, and occludes blood flow through the sinus. Fresh thrombus can propagate and extend in a retrograde direction to the transverse sinus (Fig. 140-39), to the torcular Herophili, and even to the superior sagittal sinus. In the opposite direction, the clot can extend via the jugular bulb into the internal jugular vein in the neck, and can extend to the cavernous sinus via the inferior or superior petrosal sinus. The infected clot frequently showers the bloodstream with bacteria, giving rise to the signs and symptoms of septicemia and the possibility of metastatic abscesses (most commonly to the lungs).

Figure 140-37. Axial enhanced temporal bone CT scan showing absent enhancement of left sigmoid (white arrow) next to an opacified mastoid. Note the normal enhancement of the right sigmoid (black arrow).

Figure 140-38. Coronal contrast-enhanced CT scan of the patient in Figure 140-37 showing absent flow in left internal jugular vein at the skull base (white arrow) and normal flow in right internal jugular vein (black arrow).

Figure 140-39. MR venogram showing occlusion of left transverse–sigmoid sinus system.

(From Head and Neck Archive, Advanced Medical Imaging Reference Systems [AMIRSYS], Salt Lake City, UT. Accessed January 2003.)

Because of the relative frequencies of the various types of mastoiditis and the ages of the patients affected, presently lateral sinus thrombosis is most common in adults or older children with cholesteatoma, and less common from the other types of chronic mastoiditis. In addition to cases arising by direct extension from bone erosion, lateral sinus thrombosis can also be caused by osteothrombophlebitis during AOM and mastoiditis. In this situation (and in occasional cases of chronic mastoiditis), the bony sinus plate is intact at the time of surgical exploration.

Because the sinus is a continuation of the cerebellar dura mater, extension of an infection by only a few millimeters can result in meningitis, epidural abscess, subdural empyema, cerebritis, or cerebellar abscess, all equally grave complications. In two series,^32,33 14 of 19 patients with lateral sinus thrombosis had one or more of these additional complications.

Although the frequent association with other complications tends to obscure the clinical picture, the diagnosis of lateral sinus thrombosis can be strongly suspected when there are signs and symptoms of septicemia or blockage of blood flow through the sinus. The picket-fence fever pattern with diurnal temperature spikes exceeding 103° F has been described with this condition for decades. Although some more recent articles have pointed out that this pattern is not seen as frequently, in part because many patients present with previous or current antibiotic therapy, most of the 36 patients reported by Singh²⁵ were receiving intravenous antibiotics and still exhibited that fever pattern. Unless the patient has been transferred from another hospital, on admission there is only one temperature measurement to observe. Nonetheless, a single high fever reading should alert the clinician to the possibility of sigmoid sinus thrombophlebitis. Singh²⁵ also pointed out that the neck pain in lateral sinus thrombosis may be mistakenly attributed to the neck stiffness of meningitis, when it actually represents pain and tenderness along the anterior border of the sternocleidomastoid muscle, and he suggested that percussion tenderness of the mastoid tip is another important sign.

More ominous are the signs of sudden intracranial hypertension resulting from decreased venous drainage from the skull (see section on otitic hydrocephalus). Most prominent is the occurrence or sudden worsening of a severe headache. This headache is more likely to occur with the obstruction of the dominant venous drainage system (the right side in 60% of patients). More grave is progressive obtundation; this may herald the development of cerebral edema from the increased intracranial pressure caused by involvement of the superior sagittal sinus or the cavernous sinus, and it carries a very high mortality.

Imaging studies and lumbar puncture are essential to sort out the possible types of complications in obtunded patients. If the patient’s condition permits, contrast-enhanced CT scan and contrast-enhanced MRI should be performed (see Fig. 140-32). The delta sign seen on the CT scan, enhancement of the wall of the sigmoid sinus, allows preoperative diagnosis. Wall enhancement is more sensitively evaluated by MRI, which can also document abscess formation within the sinus and exclude adjacent subdural empyema, cerebritis, or cerebellar abscess.

All patients with sigmoid sinus thrombosis require mastoidectomy to treat the underlying mastoid disease adequately. When a brain abscess is also present, surgical drainage of that abscess takes precedence over a mastoid procedure (see section on brain abscess), but if the patient’s condition permits, neurosurgical drainage of the brain abscess should be followed in the same anesthetic by expeditious mastoidectomy.

Management of the clot can involve anticoagulation, ligation of the jugular vein in the neck, and opening the sinus and evacuating the infected clot. Use of anticoagulants is rarely indicated, but anticoagulation should be strongly considered when extension of the clot to the transverse sinus or cavernous sinus is suspected or documented. Other considerations in these deteriorating patients include neurosurgical decompression and steroids. Intravenous thrombolytics are not routinely used in the presence of the infected vessel wall. Similarly, routine ligation of the jugular vein in the neck seems unnecessary, but it should be considered whenever there is evidence of extension of the clot into the neck, and should be strongly considered when septic emboli are present.

The sinus is usually addressed only after mastoidectomy. The sinus and adjacent dura are addressed by removing the overlying bone. The surgeon passes an 18- or 20-gauge needle through the sinus wall, and if there is no free blood on aspiration, a linear incision is made through the sinus wall, and the abscess and any infected clots are evacuated. Further sinus incision can enable clot evacuation proximally and distally until free bleeding occurs. The mastoid and cerebellar walls of the sinus are usually thick and indurated as a result of the chronic infection. The surgeon can safely scrape them gently with a broad flat instrument such as a Freer elevator to remove the infected tissue. Syms and colleagues³³ reported treating six patients with lateral sinus thrombosis and concomitant intracranial complications with mastoidectomy, but without opening and evacuating the lateral sinus clot. All patients survived, but the average hospital stay was more than 49 days; it was 38 days when the patient with the longest stay was not included. In contrast, patients reported by Kaplan and Kraus³² underwent surgery that included incision of the sinus and evacuation of the clot or abscess, and their mean hospital stay was only 17 days.

Otitic Hydrocephalus

Otitic hydrocephalus is an entity wherein an otologic condition has resulted in signs and symptoms of acute hydrocephalus. The condition seems to result from diminished venous drainage of the cranium. With reduced venous outflow, intracranial pressure increases, brain edema ensues, and signs and symptoms of acute intracranial hypertension manifest. In most cases, otitic hydrocephalus results from initial occlusion of the sigmoid or lateral sinus, with or without extension to the transverse sinus, inferior petrosal sinus, or cavernous sinus. The likelihood that symptoms will develop after occlusion of the lateral sinus adjacent to the mastoid reflects the following: (1) the size of the involved lateral sinus compared with the opposite lateral sinus; (2) the adequacy of the collateral venous network, including the cavernous sinus and opposite inferior petrosal sinus; and (3) the likelihood that propagation of the process will involve additional venous outflow.

Some authors view otitic hydrocephalus as a distinct clinical entity consisting of intracranial hypertension and resolved or resolving (usually acute) otitis media, having no relationship to lateral sinus thrombophlebitis.²⁴ Others view it more as a pathophysiologic consequence of lateral sinus thrombosis that occurs more commonly as a result of AOM than COM and depends on the three factors mentioned in the previous paragraph. The distinction is less important than recognizing the relationship between the symptom complex, ear disease, lateral sinus, and emergent nature of the treatment.

In the early stages, a diffuse severe headache dominates the clinical picture. In uncomplicated cases with (or occasionally without) medical management, the continuous headache gradually ameliorates and dissipates over 3 to 7 days. If collateral venous drainage is inadequate, and intracranial pressure remains sufficiently elevated long enough, signs of dulling of the sensorium or decreased visual acuity from retinal vein occlusion appear. Progression to coma and death is possible. CT scanning and immediate neurologic and neurosurgical consultation are appropriate.