The pinna (Fig. 26.1) is made of fibroelastic cartilage. The external auditory meatus has an outer cartilage portion; the inner part is formed by the tympanic bone (Fig. 26.2). It is lined by squamous epithelium and contains ceruminous glands that produce wax. There is very little subcutaneous tissue and soft tissue swelling is very painful.

Fig. 26.1 Anatomy of the pinna.

Fig. 26.2 Anatomy of the ear.

Middle ear

The vibrating tympanic membrane is conical and attached to the margin of the bony ear canal laterally and to the handle of the malleus, the first of the three ossicles, medially (Fig. 26.2). The head of the malleus is attached to the body of the incus in the space superior to the middle ear known as the attic. The long process of the incus attaches to the head of the stapes via its lenticular process. The stapes is joined to the oval window margin by the annular ligament. The middle ear is lined by simple cuboidal epithelium containing some mucus-secreting cells. The middle ear space is connected to the nasopharynx by the Eustachian tube, which maintains the middle ear at atmospheric pressure.

The inner ear

The inner ear membrane encloses a labyrinth filled by a fluid called endolymph. This is surrounded by a bony labyrinth, the otic capsule, which is filled with perilymph. The cochlea, the hearing component of the inner ear, is a tube linking the oval and round windows, coiled up like a shell. The vestibular (balance) portion of the inner ear consists of three semicircular canals, together with their vestibule, which contains the saccule and utricle, medial to the stapes footplate. The cochlear and vestibular nerves combine in the internal auditory meatus and pass medially to the brainstem. The facial nerve enters the temporal bone through the internal auditory meatus and passes laterally to the geniculate ganglion, where it turns posteriorly (the first genu). It passes through the middle ear above the oval window and turns inferiorly (the second genu) to exit at the stylomastoid foramen.

Physiology

The pinna funnels sound into the ear canal. The tympanic membrane lever mechanism, the ossicular lever mechanism and the large size of the drum relative to the stapes footplate act as an impedance-matching transformer. Vibrations in air are thus transferred to the cochlear fluids without excessive loss of energy. The cochlea converts these endolymph vibrations into electrical impulses in the auditory nerve, by stimulation of hair cells in the organ of Corti. The maximum response to high frequencies occurs in the basal turn of the cochlea. Low frequencies maximally stimulate the apex. Auditory neurons connect via the brainstem to the auditory cortex, where again different groups of cells are stimulated by nerve impulses coded for different frequencies. The hair cells in the ampullae of the semicircular canals are stimulated by angular acceleration. The saccule and utricle are stimulated by linear acceleration. Information from the labyrinths, eyes and limbs is combined within the brainstem. Connections from the vestibular nuclei pass to the cortex and the cerebellum (Fig. 26.3).

Fig. 26.3 The vestibular system.

Assessment

Clinical features

Disorders of the external or middle ear can impair sound transmission to the inner ear and cause conductive deafness. Sensorineural deafness results from lesions of the cochlea or its nerve. Deafness is often associated with a noise in the ear (tinnitus). Ear pain (otalgia) may be due to ear disease but may also be referred from other sites (Table 26.1). Ear-related disorders of balance usually cause a sensation of movement (vertigo), most often rotation. ‘Unsteadiness’ however, typically has a non-otological cause. Patients with ear disease occasionally fall to the ground but never lose consciousness.

Table 26.1 Causes of referred otalgia

Pharynx and larynx

Mouth

Temporomandibular joints (TMJ)

• TMJ dysfunction

• Arthritis

Neck

• Cervical spondylosis

• Tumour

Paranasal sinuses

• Maxillary sinusitis

Examination

The ear canal and tympanic membrane are inspected with an otoscope, a rigid telescope or a microscope. Microscopy can assist in wax or discharge removal. Tuning fork tests differentiate between conductive and sensorineural hearing loss (Rinne’s test). In health or sensorineural deafness, a tuning fork is heard better via the ear canal (air conduction) than via the mastoid process (bone conduction). When there is a conductive hearing loss, the tuning fork is heard better by bone conduction. When hearing is symmetrical, a tuning fork placed in the centre of the forehead is heard equally well in both ears (Weber’s test). If a conductive hearing loss is present in one ear, the tuning fork is heard better in the deaf ear if the loss is conductive which can be easily shown by occluding one ear and applying the fork to your own head. Conversely, in a unilateral sensorineural deafness, the sound is louder in the good ear.

Audiometry

Hearing by air conduction can be assessed by pure tone audiometry, in which sounds of known pitch and loudness are presented to each ear in turn via headphones. Bone conduction (cochlear function) can be separately tested by applying sounds to the mastoid process. A masking tone is needed if the two cochleae are to be tested separately. The difference between the air and bone conduction gives the level of conductive hearing loss (Figures 26.4 and 26.5). The patient’s ability to hear speech can be tested by presenting lists of words via headphones. The percentage correctly identified at different loudness levels allows derivation of a speech reception threshold (50% of words correct) and a discrimination score. Middle ear function (compliance) can be assessed by tympanometry. The amount of sound from a probe reflected back from the drum is measured while the pressure in the ear canal is made to vary. The compliance is maximal when the pressure in the ear canal equals the pressure in the middle ear, because when pressure is the same on both sides of the drum it is maximally mobile. Tympanometry is most often used to confirm the presence of fluid in the middle ear.

Fig. 26.4 Audiogram showing conductive deafness.

Fig. 26.5 Audiogram showing sensorineural deafness.

Temporal bone imaging

In patients with unilateral sensorineural hearing loss, MRI is used to detect an acoustic neuroma (Fig. 26.6). MRI also demonstrates the presence of normal fluid in the cochlea before attempting cochlear implantation. CT scans can be used to demonstrate temporal bone anatomy, congenital abnormalities and fractures or unusual pathology.

Fig. 26.6 Magnetic resonance imaging (MRI) of the cerebellopontine angle.

A Normal MRI scan of cerebellopontine angle. Thin arrow = IAM (internal auditory meatus). B MRI showing an acoustic neuroma. Thick arrow = lesion compressing cerebellum.

Diseases of the external auditory meatus

Diseases of the middle ear

Acute suppurative otitis media

This is a bacterial infection of the middle ear space, usually caused by Streptococcus pneumoniae or Haemophilus influenzae, most commonly occurring in young children (3 years of age and under). Children present with a combination of ear pain (otalgia), fever and malaise. On examination, dilated blood vessels are seen on the drum surface in the early stages. The drum then becomes red and begins to bulge. Perforation with discharge frequently occurs, usually followed by spontaneous healing. Antibiotic therapy remains controversial: the majority of cases resolve spontaneously in a few days (EBM 26.1). Antibiotics are useful in high risk patients (e.g. immunosuppression) as they shorten the episodes and reduce the rate of infective complications such as mastoiditis, facial palsy or meningitis.

26.1 Antibiotics for acute otitis media in children

‘Clinicians need to evaluate whether the minimal short-term benefit from longer treatment of antibiotics is worth exposing children to a longer course of antibiotics.’

Kozyrskyj et al. Short-course antibiotics for acute otitis media. Cochrane Database of Systematic Reviews 2010, Issue 9. Art. No.: CD001095. DOI: 10.1002/14651858.CD001095.pub2

For further information: www.cochrane.org

Otitis media with effusion (OME), or ‘glue ear’

In this condition, fluid accumulates in the middle ear space, usually in children. A minority of adult cases are caused by nasopharyngeal tumours and systemic disease. Childhood OME causes hearing loss and may interfere with the acquisition of language and performance at school. Virtually all cases resolve spontaneously, but this may take as long as 10 years. Initial management involves documentation of the presence of effusion and the degree of hearing loss during a period of watchful waiting. If the effusions persist, hearing may be improved by drainage of the effusion (myringotomy) and insertion of a ventilation tube (Fig. 26.8). In children, removal of the adenoids leads to more effective resolution. Spontaneous resolution may also occur in adults, but often effusions persist. Ventilation tubes can also be of value, but some cases are better managed with a hearing aid.

Fig. 26.8 Surgical treatment of otitis media with effusion.

A Myringotomy. B Grommet insertion.

Chronic suppurative otitis media

This causes aural discharge and deafness.

Tubotympanic or mucosal disease

This is characterized by the presence of a perforation of the tympanic membrane, which typically discharges. Swimming and other activities that involve water entering the ear may exacerbate the discharge. The hearing loss is worse when the ossicles are eroded, most commonly the incus long process. Discharge can be controlled by cleaning the ear and introducing eardrops. To minimize the risks of ototoxicity, drops should be used for a maximum of 2 weeks. Surgery is indicated to prevent discharge, improve hearing or allow the patient to swim. The operation to repair a perforation is called a myringoplasty. Defects of the ossicular chain can be repaired by removing the incus and repositioning it to bridge the gap between the malleus and stapes or by using a prosthesis (ossiculoplasty).

Atticoantral or squamous disease

A cholesteatoma forms as a retracted area of the drum in which keratin accumulates. The drum tissue at the periphery of the cholesteatoma produces a number of chemical mediators that stimulate osteoclast activity. Hence the cholesteatoma can erode surrounding bone and cause complications such as disruption of the ossicular chain, facial palsy and intracranial sepsis. The primary treatment goal is to eliminate the disease. Surgical treatment (mastoidectomy) is mandatory in all but the very elderly and those who are medically unfit.

Summary Box 26.1 Otitis media

• Acute otitis media is extremely common under the age of 3 years

• The child typically awakes crying at night with a painful ear. The diagnosis is confirmed by a red, inflamed bulging tympanic membrane on otoscopy

• Pain relief is important. Antibiotics should be given to prevent the development of complications

• Otitis media with effusion (glue ear) occurs transiently in many children and is manifested by temporary hearing impairment. Most cases settle spontaneously. Bilateral persistent hearing impairment may demand surgery (adenoidectomy, or insertion of a grommet)

• Chronic otitis media involves the middle ear and mastoid mucosa. There is permanent perforation of the tympanic membrane, hearing loss and a mucopurulent discharge. Inactive ears require closure of the perforated membrane (myringoplasty) and rebuilding of the ossicular chain. Ears with cholesteatoma may require surgical removal of the posterior canal wall to open the attic or mastoid cavity and so reduce the risk of meningitis, intracranial abscess and facial palsy.

Otosclerosis

This is a condition in which the stapes becomes fixed by new bone formation. It is more common in females and sometimes runs in families. It can be treated by an operation called stapedectomy, in which the stapes is replaced by a piston attached to the incus. This produces excellent hearing improvement in the majority of patients, but a minority suffer surgically-induced, permanent inner ear damage. The hearing loss can be managed with a hearing aid.

Diseases of the inner ear

Deafness

Deafness is most commonly due to changes in the cochlea. Ageing produces a gradual deterioration in hearing acuity (presbycusis). The cochlea may be damaged by chronic noise exposure, blast injuries and temporal bone fractures. Significant noise exposure may occur in heavy industry and agriculture, from playing in rock bands and shooting. Deafness may also be inherited or a manifestation of systemic disease. Some drugs, such as aminoglycosides and cytotoxic agents like cisplatinum, can damage the cochlea. Viral infections such as mumps and rubella can also cause sensorineural deafness. Unilateral hearing loss occurs in acoustic neuroma (Fig. 26.6B).

Most cases of inner ear deafness are managed with a hearing aid, but in cases of profound deafness, hearing may be restored by a cochlear implant. This consists of a series of electrodes surgically introduced into the cochlea. A speech processor converts sound into electrical energy, which stimulates the cochlear nerve.

Vertigo

In some cases, balance disorders may arise from abnormalities of the vestibular portion of the inner ear.

Benign paroxysmal positional vertigo is a very common condition in middle age and is due to debris floating in the posterior semicircular canal which stimulates the ampulla hair cells, producing vertigo. Episodes are triggered when the affected ear is down-most – as when the patient turns over in bed. Debris can be displaced therapeutically from the posterior canal by positioning the head so that it floats out of the canal into the vestibule (Epley’s particle repositioning manoeuvre). If this fails, division of the ampullary (singular) nerve or occlusion of the posterior semicircular canal is beneficial.

Vestibular neuronitis causes severe vertigo lasting for as long as several weeks. The hearing remains normal. It is due to severe temporary reduction of vestibular function in the affected ear. Patients are managed by bed rest and vestibular sedatives, such as prochlorperazine.

Abnormal fluctuations of fluid pressure within the inner ear (endolymphatic hydrops) produce a combination of fluctuating deafness, tinnitus and vertigo known as Ménière’s disease. This uncommon condition is initially treated medically, using either a vasodilator agent (e.g. betahistine) or a diuretic. If medical treatment fails, the vestibular portion of the labyrinth may be destroyed by a middle ear injection of gentamicin. Procedures of last resort are surgical destruction of the labyrinth, or section of the vestibular nerve.

Disorders of the facial nerve

Facial palsy may result from temporal bone fractures or surgical trauma. When the nerve is divided, it may be repaired by end-to-end anastomosis or a cable graft derived from a sensory nerve of the right size, such as the sural nerve. Bell’s palsy is an idiopathic (lower motor neuron) facial palsy that usually improves spontaneously. There is some evidence that it is caused by viral infection. Steroid therapy given soon after the onset is beneficial. Herpes zoster infection of the geniculate ganglion causes facial palsy, often associated with deafness and vertigo (Ramsay–Hunt syndrome). Vesicles may be seen on the palate and on the tympanic membrane. Antiviral treatment appears helpful for Ramsay–Hunt syndrome (unlike Bell’s palsy). Intracranial disease and malignant tumours in the parotid area of the neck can also cause facial palsy.

Nose

Anatomy

The nasal skeleton consists of two nasal bones superiorly and two pairs of cartilages inferiorly (Fig. 26.9). The nasal cavity is divided in two by a partition composed of cartilage anteriorly and bone posteriorly (the nasal septum). Three turbinate bones protrude from the lateral wall of the nose (Fig. 26.10). Between the inferior and middle turbinates is the middle meatus of the nose. Most of the paranasal sinuses open into this area under cover of a soft tissue flap known as the uncinate process. Obstruction of the sinus ostia in this area can cause sinus pain and may lead to sinus infection. Superior to the superior turbinate is an area of olfactory epithelium from which arise the nerve fibres of the olfactory nerve. The anterior portion of the nasal septum is called Little’s area. Here prominent veins are often found, and nose bleeds most often arise from this part of the nose.