Otitis Media with Effusion

Although, strictly speaking, AOM is a subset of OME, by implication OME describes a nonacutely infected middle ear effusion. Chronic OME is defined as an effusion persisting for more than

3 months' duration, and is a rather limiting term—perhaps a better description is persistent OME. Synonyms include serous otitis, secretory otitis, glue ear, and middle ear catarrh. Unlike AOM, OME is probably underdiagnosed and may present a diagnostic challenge, especially if otoscopy alone is used. Pneumatic otoscopy, especially if complimented by tympanometry, is sensitive in experienced hands. The natural history of this disorder is for spontaneous resolution in the majority of cases—more than 80% resolution by 2 months.31 It is the small number of children who continue to have effusions after 2 or 3 months that are of concern. An even smaller percentage will have an underlying predisposing pathology, such as Down syndrome, cleft palate, immunoglobulin deficiency, or ciliary dyskinesia.

Although balance and behavioral changes are not uncommon with OME, it is the compromise to hearing that is of greatest concern. In a small percentage of children, chronic middle ear effusions may have a role in the development of retraction pockets, ossicular erosion, and cholesteatoma formation. However, these are more likely consequences of chronic eustachian tube dysfunction (which predisposed to the effusion) than the effusion per se. A dense effusion typically may confer up to a 30-db hearing loss, which represents a significant barrier to learning. It is unknown for what duration an effusion must be present, and at what ages, to be of long-term consequence. It may well be that an effusion acts as a cofactor with other influences such as young age, low socioeconomic status, or poor teacher-to-child ratios, and that these factors act synergis-tically. The literature is highly suggestive that prolonged effusions are of long-term significance.13-16

Until recently, it was believed that for OME to be of concern, it had to be bilateral, and that there had to be at least a

15-dB hearing loss (pure-tone average) to possibly affect education.32 In fact, the Agency for Health Care Policy and Research (AHCPR) guidelines in 1994 recommended that a 20-db threshold or worse be present in the better hearing ear before the placement of tympanostomy tubes.33 There is now evidence that binaural hearing is advantageous and that children with normal pure-tone thresholds despite bilateral effusions may, in fact, still be hearing impaired. In a small but elegant study, Rosenfeld et al.34 looked at children with bilateral effusions and normal pure tone averages, who were then tested with sound field audiology with and without background noise. These investigators found that word recognition was slightly compromised at normal (50-db) conversational levels and markedly compromised at soft (35-db) conversational levels, and that with background noise, there was a marked further deterioration (as poor as 38% word recognition at 35 db with background noise). More impressively, after tympanostomy tube insertion, there was a marked improvement in word recognition. Sadly, sound-field audiology is usually practical only after the age of 4, whereas the population presumed most at risk are those even younger.

Two recent meta-analyses have come to a similar conclusion, namely that antibiotics have a small but distinct advantage over placebo in the treatment of persistent OME.28,35 It is notable that with the same premise, these two articles did not examine exactly the same set of studies, and their conclusions were not identical. Interestingly they appeared shortly after another attempted meta-analysis on the same topic was abandoned as being an area inappropriate for meta-analysis.36 There is, however, no conclusive evidence in these or any other article that one antibiotic has a distinct therapeutic advantage over any other. This is in part due to the "Pollyanna" effect, namely that in a spontaneously resolving condition in which antibiotics have only a comparatively small influence on outcome, extremely large numbers are required to show an advantage of one product over another, with the corollary being that a new product can easily be shown to be as good (or statistically no worse) as any other, particularly if the power is low.37 Similarly, there is little good evidence in the literature that any one duration of treatment offers an advantage over another, though there is a trend toward a longer duration of antibiotic treatment being more efficacious.28 The advantage of antibiotics relates only to the short-term resolution of OME, with the effects progressively diluted out by remission and spontaneous resolution the longer a study population is followed.

In children presenting with OME of presumed short duration, and who have otherwise normal otoscopic findings, antibiotic therapy is not required. Just when antibiotic therapy is required is debated, but Bluestone's 2-month recommendation is reasonable.38 The exceptions are adults, who do not tolerate effusions at all well, and are usually insistent on intervention at a much earlier interval. This does not mean that children necessarily have fewer symptoms, but rather that they cannot express or represent themselves as effectively. The ideal duration of an antibiotic course remains unclear, but most recommendations are between 10 days and 4 weeks.

The antibiotic to use in first-line treatment of OME or AOM is hotly debated currently. There is little direct evidence to show that one has a distinct advantage over another, so it is logical to choose an agent that is tried and true, achieves good middle ear concentrations, has reasonable activity against a significant percentage of potential middle ear pathogens, is well tolerated, tastes good, has a convenient dosing schedule, is reasonably stable, and is not too ludicrously priced. Currently, Amoxil and trimethoprim/sulfamethoxazole best fit these criteria, with a variety of second-line agents. Amoxil has had an additional resurgence with the increasing percentage of Streptococcus pneumoniae that are multiply drug resistant, as many are intermediately sensitive to high-dose Amoxil. Current guidelines suggest that initial treatment (especially in AOM) with Amoxil at up to 90 mg/kg/day in two divided doses is efficacious against most resistant S. pneumoniae.39,40

If antibiotic therapy is not effective, the usual options are to observe, to continue the current course, to change antibiotics, or to consider tympanostomy tubes. The first three options are all probably of similar efficacy, although definitive data are lacking. There is, however, a vast experience with tubes accrued over the last 45 years, with nearly one million sets of tubes placed each year in the United States alone. This is the commonest operation in the world, one of the safest, and one of the most effective. The complications are well known, with ear discharge and residual perforation being the most significant. There are a plethora of different tubes from which to select, with virtually all balancing length of duration against residual perforation rate.

The other common intervention is adenoidectomy with or without tube insertion. There is little doubt that adenoidectomy is an effective therapy,41-44 probably as a result of ridding the nasopharynx of a chronic focus of infection (rather than the size of the adenoid obstructing the eustachian tube). In a proportion of children however, the size of the adenoid is also of signifi-cance.45 However, adenoidectomy is a much more invasive operation than tube insertion, with significant risks in children younger than 3 years of age that usually outweigh its benefit. Less than 20% of children receiving a first set of tubes will ever have recurrent problems of a magnitude to justify a second set. Bluestone et al.46 again provide sage advice when recommending that adenoidectomy be a consideration in the child older than 3 years of age at the time of insertion of a second set of tubes. Adenoidectomy in this population probably reduces by one-half the requirement of ultimately placing a third set of tubes.

Several other treatment options are available, most aimed at restoring the function of the eustachian tube by reducing edema at the tube orifice. Systemic antihistamines and decongestants have not proved beneficial,2 and topical decongestants and topical steroids, although having considerable theoretical appeal, so far have little evidence of efficacy. Systemic steroids, in combination with antibiotics, do appear to be effective, but the studies performed to date have been small enough that even meta-analysis still leaves wide confidence intervals that include 0.7 There are also some theoretical risks (lessening with the arrival of the varicella vaccine), such that systemic steroids should not be considered a routine therapy, but rather be reserved for selected patients on a case-by-case basis.

The most intriguing new player is the Otolam (laser assisted myringotomy), a recently introduced flashscan laser that delivers a very precise spiral of laser energy in around one-fifth of 1

second. The depth and circumference of the burn can be preselected. In fact laser myringotomy is not at all new,47 although the technology and, more importantly, the anesthetic and marketing techniques are. The use of 16% tetracaine topically is most impressive although it may take up to 45 min to have its full effect. The attraction of the laser is that the resultant myringotomy heals in around 3 weeks, as opposed to months for a tube, or hours to days for a standard myringotomy. The tetracaine and the speed and precision of the burn allow this to be performed in the office even in infants. The most obvious candidates for such technology are patients in whom a temporary myringotomy will suffice, with OME (for which 3 weeks will allow the Eustachian tube to recover, i.e., break the disease cycle) being the most obvious example. Other applications include persistent or severe AOM, hyperbaric oxygen candidates, as a bloodless method of tympanocentesis, or as a bloodless port for telescopic examination of the middle ear cleft. Tubes can obviously be inserted at the same time if desired. The initial results with the laser have been a 70% cure rate, with cure constituting a healed tympanic membrane with no effusion.48 However, this is a most expensive tool, and the economics to justify its existence have not yet been investigated. In fact, the science to justify its use, although in progress, also remains to be seen.

The next goal on the horizon is the development of an effective otitis media vaccine, aimed mainly at S. pneumoniae, a project into which considerable effort is being poured, although there are still very significant hurdles to overcome.49

0 0

Post a comment