Otitis Media

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Chapter 632 Otitis Media

Over 80% of children will have experienced at least one episode of otitis media (OM) by the age of 3 yr. The peak incidence and prevalence of OM is during the 1st 2 yr of life. OM is the leading reason for physician visits and for use of antibiotics and figures importantly in the differential diagnosis of fever. OM is the most common reason for prescribing antimicrobial drugs to children, often serves as the sole or the main basis for undertaking the most frequently performed operations in infants and young children: myringotomy with insertion of tympanostomy tubes and adenoidectomy. It is the most common cause of hearing loss in children. An important characteristic of OM is its propensity to become chronic and recur. The earlier in life a child experiences the 1st episode, the greater the degree of subsequent difficulty he or she is likely to experience in terms of frequency of recurrence, severity, and persistence of middle-ear effusion.

Accurate diagnosis of OM in infants and young children may be difficult (Table 632-1). Symptoms may not be apparent, especially in early infancy and in chronic stages of the disease. The eardrum may be obscured by cerumen, removal of which may be arduous and time-consuming. Abnormalities of the eardrum may be subtle and difficult to appreciate. In the face of these difficulties, both underdiagnosis and overdiagnosis occur. Once a diagnosis of OM has been established, its significance to the child’s health and well-being and its optimal method of management remain open to question and the subjects of continuing controversy. There is lack of consensus among authorities concerning benefit-risk ratios of available medical and surgical treatments; while OM can be responsible for serious infectious complications, middle- and inner-ear damage, hearing impairment, and indirect impairments of speech, language, cognitive, and psychosocial development, most cases of OM are not severe and are self-limiting.

The term otitis media has 2 main categories: acute infection, which is termed suppurative or acute otitis media (AOM); and inflammation accompanied by effusion, termed nonsuppurative or secretory OM, or otitis media with effusion (OME). These 2 main types of OM are interrelated: acute infection usually is succeeded by residual inflammation and effusion that, in turn, predispose children to recurrent infection. Middle-ear effusion (MEE) is a feature both of AOM and of OME and is an expression of the underlying middle-ear mucosal inflammation. In children with OM, mucosal inflammation is also present in the mastoid air cells, which are in continuity with the middle-ear cavity. It is this MEE that results in the conductive hearing loss associated with OM. The hearing loss is of a variable degree ranging from none to as much as 50 decibels hearing level (dB HL). Losses of 21-30 dB HL are usual. Although most individual episodes of OM subside within several weeks, MEE persists for 3 mo or longer in approximately 10-25% of cases.

Epidemiology

Factors believed to affect the occurrence of OM include age, gender, race, genetic background, socioeconomic status, type of milk used in infant feeding, degree of exposure to tobacco smoke, degree of exposure to other children, presence or absence of respiratory allergy, season of the year, and vaccination status. Children with certain types of congenital craniofacial anomalies are particularly prone to OM.

Congenital Anomalies

OM is universal among infants with unrepaired palatal clefts, and is also highly prevalent among children with submucous cleft palate, other craniofacial anomalies, and Down syndrome (Chapter 76). The common feature in these congenital anomalies is a deficiency in the functioning of the eustachian tubes, which predisposes these children to middle ear disease.

Vaccination Status

Streptococcus pneumoniae (Chapter 175) has historically been the most common pathogen identified in patients with acute OM. Vaccination of infants with a conjugated pneumococcal vaccine has a modest effect, lowering visits to physicians and antibiotic prescriptions for OM by only 6-8%. Vaccination does appear to have a somewhat more protective effect in limiting frequent OM episodes and the need for surgical intervention with tympanostomy tubes. Pneumococcal vaccination has decreased the overall rate of episodes of OM associated with pneumococcus and increased quality of life (Fig. 632-1). Annual influenza virus vaccination also results in a decrease in OM incidence.

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Figure 632-1 Quality of life and frequency of acute otitis media (AOM).

(From Brouwer AR, Maillé M, Rovers R, et al: Effect of pneumococcal vaccination on quality of life in children with recurrent otitis media: a randomized, controlled trial, Pediatrics 115:273–279, 2005, Fig 2.)

Etiology

Acute Otitis Media (AOM)

Pathogenic bacteria can be isolated by standard culture techniques from middle-ear fluid in a majority of well-documented AOM. A high percentage of cases have cultures with either no growth or the presence of organisms generally considered nonpathogenic. Three pathogens predominate in AOM: Streptococcus pneumoniae, nontypeable Haemophilus influenzae, and Moraxella catarrhalis. The overall incidence of these organisms has changed with the widespread use of the conjugate pneumococcal vaccine. In countries where this vaccine is employed, nontypeable H. influenzae has overtaken S. pneumoniae as the most common pathogen; found in 40-50% of cases. S. pneumoniae still represents a common pathogen found in 30-50% of cases with M. catarrhalis representing the majority of the remaining cases. Other pathogens include group A streptococcus, Staphylococcus aureus, and gram-negative organisms. S. aureus and gram-negative organisms are found most commonly in neonates and very young infants who are hospitalized; in outpatient settings, the distribution of pathogens in these young infants is similar to that in older infants. Molecular techniques to identify bacterial pathogens have suggested the importance of other bacterial species such as Alloiococcus otitidis.

Evidence of respiratory viruses also may be found in middle-ear exudates of children with AOM, either alone or, more commonly, in association with pathogenic bacteria. Of these viruses, rhinovirus and respiratory syncytial virus (RSV) are found most often. AOM is a known complication of bronchiolitis; middle ear aspirates in children with bronchiolitis regularly contain bacterial pathogens, suggesting that RSV is rarely, if ever, the sole cause of their AOM. Using more precise measures of viable bacteria than standard culture techniques, such as polymerase chain reaction assays, a much higher rate of bacterial pathogens can be demonstrated. It remains uncertain whether viruses alone can cause AOM, or whether, their role is limited to setting the stage for bacterial invasion, and perhaps also to amplifying the inflammatory process and interfering with resolution of the bacterial infection. Viral pathogens have a negative impact on eustachian tube function, can impair local immune function, increase bacterial adherence and change pharmacokinetics reducing the efficacy of antimicrobial medications.

Pathogenesis

Anatomic Factors

Patients with significant craniofacial abnormalities affecting the eustachian tube function have an increased incidence of OM. In addition, during the pathogenesis of OM the eustachian tube demonstrates decreased effectiveness in ventilating the middle-ear space.

Under usual circumstances the eustachian tube is passively closed and is opened by contraction of the tensor veli palatini muscle. In relation to the middle ear, the tube has 3 main functions: ventilation, protection, and clearance. The middle-ear mucosa depends on a continuing supply of air from the nasopharynx delivered by way of the eustachian tube. Interruption of this ventilatory process by tubal obstruction initiates an inflammatory response that includes secretory metaplasia, compromise of the mucociliary transport system, and effusion of liquid into the tympanic cavity. Measurements of eustachian tube function have demonstrated that the tubal function is suboptimal during the events of OM with increased opening pressures.

Eustachian tube obstruction may result from extraluminal blockage via hypertrophied nasopharyngeal adenoid tissue or tumor, or may result from intraluminal obstruction via inflammatory edema of the tubal mucosa, most commonly as a consequence of a viral upper respiratory tract infection. Progressive reduction in tubal wall compliance with increasing age may explain the progressive decline in the occurrence of OM as children grow older. The protection and clearance functions of the eustachian tube may also be involved in the pathogenesis of OM. Thus, if the eustachian tube is patulous or excessively compliant, it may fail to protect the middle ear from reflux of infective nasopharyngeal secretions, whereas impairment of the mucociliary clearance function of the tube might contribute to both the establishment and persistence of infection. The shorter and more horizontal orientation of the tube in infants and young children may increase the likelihood of reflux from the nasopharynx and impair passive gravitational drainage through the eustachian tube.

In special patient populations with craniofacial abnormalities there exists an increased incidence of OM that has been associated with the abnormal eustachian tube function. In children with cleft palate, where OM is a universal finding, the main factor underlying the chronic middle-ear inflammation appears to be impairment of the opening mechanism of the eustachian tube, due perhaps to greater-than-normal compliance of the tubal wall. Another possible factor is defective velopharyngeal valving, which may result in disturbed aerodynamic and hydrodynamic relationships in the nasopharynx and proximal portions of the eustachian tubes. In children with other craniofacial anomalies and with Down syndrome, the high prevalence of OM has also been attributed to structural and/or functional eustachian tubal abnormalities.

Host Factors

The effectiveness of a child’s immune system in response to the bacterial and viral insults of the upper airway and middle ear during early childhood probably is the most important factor in determining which children are otitis prone. The maturation of this immune system during early childhood is most likely the primary event leading to the decrease in incidence of OM as children move through childhood. IgA deficiency is found in some children with recurrent AOM but the significance is questionable, inasmuch as IgA deficiency is also found not infrequently in children without recurrent AOM. Selective IgG subclass deficiencies (despite normal total serum IgG) may be found in children with recurrent AOM in association with recurrent sinopulmonary infection, and these deficiencies probably underlie the susceptibility to infection. Children with recurrent OM that is not associated with recurrent infection at other sites rarely have a readily identifiable immunologic deficiency. Nonetheless, evidence that subtle immune deficits play a role in the pathogenesis of recurrent AOM is provided by studies involving antibody responses to various types of infection and immunization; by the observation that breast milk feeding, as opposed to formula feeding, confers limited protection against the occurrence of OM in infants with cleft palate; and by studies in which young children with recurrent AOM achieved a measure of protection from intramuscularly administered bacterial polysaccharide immune globulin or intravenously administered polyclonal immunoglobulin. This evidence, along with the documented decrease incidence of upper respiratory tract infections and OM as children’s immune systems develop and mature is indicative of the importance of a child’s innate immune system in the pathogenesis of OM (Chapter 118).

Viral Pathogens

Although OM may develop and certainly may persist in the absence of apparent respiratory tract infection, many, if not most, episodes are initiated by viral or bacterial upper respiratory tract infection. In a study of children in group daycare, AOM was observed in approximately 30-40% of children with respiratory illness caused by RSV (Chapter 252), influenza viruses (Chapter 250), or adenoviruses (Chapter 254), and in approximately 10-15% of children with respiratory illness caused by parainfluenza viruses, rhinoviruses, or enteroviruses. Viral infection of the upper respiratory tract results in release of cytokines and inflammatory mediators, some of which may cause eustachian tube dysfunction. Respiratory viruses also may enhance nasopharyngeal bacterial colonization and adherence and impair host immune defenses against bacterial infection.

Clinical Manifestations

Symptoms of AOM are variable, especially in infants and young children. In young children, evidence of ear pain may be manifested by irritability or a change in sleeping or eating habits and occasionally, holding or tugging at the ear (see Table 632-1). Pulling at the ear has a low sensitivity and specificity. Fever may also be present. Rupture of the tympanic membrane with purulent otorrhea is uncommon. Systemic symptoms and symptoms associated with upper respiratory tract infections also occur; occasionally there may be no symptoms, the disease having been discovered at a routine health examination. OME often is not accompanied by overt complaints of the child but can be accompanied by hearing loss. This hearing loss may manifest as changes in speech patterns but often goes undetected if unilateral or mild in nature, especially in younger children. Balance difficulties or disequilibrium can also be associated with OME and older children may complain of mild discomfort or a sense of fullness in the ear (Chapter 628).

Examination of the Eardrum

Otoscopy

Two types of otoscope heads are available: surgical or operating, and diagnostic or pneumatic. The surgical head embodies a lens that can swivel over a wide arc and an unenclosed light source, thus providing ready access of the examiner’s instruments to the external auditory canal and tympanic membrane. Use of the surgical head is optimal for removing cerumen or debris from the canal under direct observation, and is necessary for satisfactorily performing tympanocentesis or myringotomy. The diagnostic head incorporates a larger lens, an enclosed light source, and a nipple for the attachment of a rubber bulb and tubing. When an attached speculum is fitted snugly into the external auditory canal, an airtight chamber is created comprising the vault of the otoscope head, the bulb and tubing, the speculum, and the proximal portion of the external canal. Although examination of the ear in young children is a relatively invasive procedure that is often met with lack of cooperation by the patient, this task can be enhanced if done with as little pain as possible. The outer portion of the ear canal contains hair-bearing skin and subcutaneous fat and cartilage that allow a speculum to be placed with relatively little discomfort. Closer to the tympanic membrane the ear canal is made of bone and is lined only with skin and no adnexal structures or subcutaneous fat; a speculum pushed too far forward and placed in this area often causes skin abrasion and pain. Using a rubber-tipped speculum or adding a small sleeve of rubber tubing to the tip of the plastic speculum may serve to minimize patient discomfort and enhance the ability to achieve a proper fit and an airtight seal.

Learning to perform pneumatic otoscopy is a critical skill in being able to assess a child’s ear and in making an accurate diagnosis of OM. By observing as the bulb is alternately squeezed gently and released, the degree of tympanic membrane mobility in response to both positive and negative pressure can be estimated providing a critical assessment of middle ear fluid which is a hallmark sign of both AOM and OME. With both types of otoscope heads, bright illumination is also critical for adequate visualization of the tympanic membrane.

Clearing the External Auditory Canal

If the tympanic membrane is obscured by cerumen, the cerumen may be removed under direct observation through the surgical head of the otoscope, using a Buck curette (N-400-0, Storz Instrument Co). Remaining bits can then be wiped away using a Farrell applicator (N-2001A, Storz Instrument Co), with its tip (triangular in cross section) wrapped with a bit of dry or alcohol-moistened cotton to create a dry or wet “mop.” Alternatively, gentle suction may be applied, using a No. 5 or 7 French ear suction tube. During this procedure it may be most advantageous to restrain the infant or young child in the prone position, turning the child’s head to the left or right as each ear is cleared. One adult, usually a parent, can place one hand on each of the child’s buttocks and brace the child’s hips against the examining table, using his or her own weight for additional bracing if necessary. Another adult can restrain the child’s head with one hand and the child’s free arm with the other, changing hands for the opposite ear. In children old enough to cooperate, usually beginning at about 5 yr of age, clearing of the external canal may be achieved more easily and safely and less traumatically by lavage than by mechanical removal, provided one can be certain that a tympanic membrane perforation is not present. In general, many children’s ears are “self-cleaning” due to squamous migration of ear canal skin, and parental cleaning of cerumen with cotton swabs often complicates cerumen impaction by pushing cerumen deeper into the canal and compacting it.

Diagnosis

A certain diagnosis of OM should contain all of the following elements: (1) recent and usually acute onset of illness, (2) presence of MEE, and (3) signs and symptoms of middle-ear inflammation including erythema of the tympanic membrane or otalgia (see Table 632-1). A simplified differentiating schema establishes a diagnosis of AOM when, in addition to having MEE, a child gives evidence of recent, clinically important ear pain or the tympanic membrane shows marked redness or distinct fullness or bulging.

Distinguishing between AOM and OME on clinical grounds is straightforward in most cases, although each condition may evolve into the other without any clearly differentiating physical findings; any schema for distinguishing between them is to some extent arbitrary. In an era of increasing bacterial resistance, distinguishing between AOM and OME is important in determining treatment, because OME in the absence of acute infection does not require antimicrobial therapy. Purulent otorrhea of recent onset is indicative of AOM; thus, difficulty in distinguishing clinically between AOM and OME is limited to circumstances in which purulent otorrhea is not present. Both AOM without otorrhea and OME are accompanied by physical signs of MEE, namely, the presence of at least 2 of 3 tympanic membrane abnormalities: white, yellow, amber, or (rarely) blue discoloration; opacification other than that due to scarring; and decreased or absent mobility. Alternatively in OME, either air-fluid levels or air bubbles outlined by small amounts of fluid may be visible behind the tympanic membrane, a condition often indicative of impending resolution (Fig. 632-2).

To support a diagnosis of AOM instead of OME in a child with MEE, distinct fullness or bulging of the tympanic membrane may be present, with or without accompanying erythema; or, at minimum, MEE should be accompanied by ear pain that appears clinically important. Unless intense, erythema alone is insufficient because erythema, without other abnormalities, may result from crying or vascular flushing. In AOM the malleus may be obscured, and the tympanic membrane may resemble a bagel without a hole but with a central depression (Fig. 632-3). Rarely the tympanic membrane may be obscured by surface bullae, or may have a cobblestone appearance. Bullous myringitis is a physical manifestation of AOM and not an etiologically discrete entity. Within days after onset, fullness of the membrane may diminish, even though infection may still be present.

In OME, bulging of the tympanic membrane is absent or slight or the membrane may be retracted (Fig. 632-4); erythema also is absent or slight, but may increase with crying or with superficial trauma to the external auditory canal incurred in clearing the canal of cerumen. In children with MEE but without tympanic membrane fullness or bulging, the presence of unequivocal ear pain is usually indicative of AOM.

Commonly, both before and after episodes of OM and also in the absence of otitis media, the tympanic membrane may be retracted as a consequence of negative middle-ear air pressure. The presumed cause is diffusion of air from the middle-ear cavity more rapidly than it is replaced via the eustachian tube. Mild retraction cannot be considered pathologic, although in some children it is accompanied by mild conductive hearing loss. More extreme retraction, however, is of concern, as discussed later in the section on sequelae of OM.

Tympanometry

Tympanometry, or acoustic immittance testing, is a simple, rapid, atraumatic test that, when performed correctly, offers objective evidence of the presence or absence of MEE. The tympanogram provides information about tympanic membrane (TM) compliance in electroacoustic terms that can be thought of as roughly equivalent to TM mobility as perceived visually during pneumatic otoscopy. The absorption of sound by the TM varies inversely with its stiffness. The stiffness of the membrane is least, and accordingly its compliance is greatest, when the air pressures impinging on each of its surfaces—middle-ear air pressure and external canal air pressure—are equal. In simple terms, anything tending to stiffen the TM, such as tympanic membrane scarring or middle-ear fluid, reduces the TM compliance, which is recorded as a flattening of the curve of the tympanogram. An ear filled with middle-ear fluid generally has a very noncompliant TM and, therefore, a flattened tympanogram tracing.

Tympanograms may be grouped into 1 of 3 categories (Fig. 632-5). Tracings characterized by a relatively steep gradient, sharp-angled peak, and middle-ear air pressure (location of the peak in terms of air pressure) that approximates atmospheric pressure (Fig. 632-5A) (type A curve) are assumed to indicate normal middle-ear status. Tracings characterized by a shallow peak or no peak and by negative or indeterminate middle-ear air pressure, and often termed “flat” or type B (Fig. 632-5B), usually are assumed to indicate the presence of a middle-ear abnormality that is causing decreased TM compliance. The most common such abnormality, by far, in infants and children is MEE. Tracings characterized by intermediate findings—somewhat shallow peak, often in association with a gradual gradient (obtuse-angled peak) or negative middle-ear air pressure, or combinations of these features (Fig. 632-5C)—may or may not be associated with MEE, and must be considered nondiagnostic or equivocal. In general, the shallower the peak, the more gradual the gradient, and the more negative the middle-ear air pressure, the greater the likelihood of MEE.

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