Chapter 2 Canalplasty for Exostoses of the External Auditory Canal and Miscellaneous Auditory Canal Problems

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Although clinical disease caused by exostoses of the external auditory canal (EAC) is infrequent, it occurs often enough that a method of surgical management should be in the armamentarium of the otologic surgeon. Because it is not a high-incidence problem or one that is life-threatening, many otolaryngologists use various independent approaches, which frequently result in elimination of or damage to the canal skin. These procedures frequently produce suboptimal results. A well-conceived approach addresses the problem of removal of exostoses, while maintaining the valuable residual skin of the EAC. This chapter begins with clinical observations regarding this condition and then describes an operative procedure that has been very successful in its management.

The etiology of these benign growths of the tympanic bone is strongly associated with the frequency and severity of exposure to cold water.¹ Frequently, these lesions are found in surfers, swimmers, or other individuals with frequent cold water exposure over several years. A widely held belief based on clinical information is that exostoses occur primarily during the years of growth, with their proliferation being enhanced or perhaps even caused by exposure to cold water during this period. This belief tends to be supported by historical information from patients with exostoses, who almost always indicate that they swam in cold water during their youth.²^–⁴ This historical information is strongly corroborated by the high incidence of exostoses in avid surfers who spend hours in the water almost daily. In our clinical experience, this problem occurs almost exclusively in men, who are more likely than women of the same age to have had frequent cold water exposure during their youth.

Most exostoses do not develop to a degree sufficient to cause clinical symptoms. Patients are frequently referred to otologists because the growths are observed, and not understood, by primary care physicians. This is particularly true with exostoses that have a more pedunculated form than the more subtle sessile configuration. When exostoses become more marked, however, they obstruct the natural elimination of desquamated epithelium from the ear canal, and patients usually present with recurrent episodes of external otitis. In their most prolific expression, exostoses can lead to hearing impairment by causing the collection of epithelial debris that tamponades tympanic membrane movement, by impinging on and limiting the mobility of the malleus, or by markedly narrowing the aperture of the canal. These conditions may manifest as a conductive hearing impairment on audiometric examination.

The EAC is part of the hearing pathway. Essentially, the EAC is a tube with resonant characteristics that amplify the incoming sound. The degree of amplification and the frequency at which it occurs are a function of the diameter and the length of the canal. When the diameter becomes small, it can interfere with the passage of sound and cause a hearing impairment. This effect does not become significant, however, until the aperture becomes very small. With apertures less than 3 mm, high-frequency sounds begin to diminish, and further compromise of the channel diameter results in increased impairment and lower frequency loss.