"No one would argue that surgery for congenital aural atresia has the same potential for hearing restoration as does stapedectomy; few middle ear procedures involving the middle ear ossicles do. But is the success rate so modest that unilateral cases are best observed, at least until the individual is an adult and can make his or her own decision?"
"We cannot overemphasize the importance of complete audiologic evaluation even in the child with unilateral atresia with or without microtia."
"The routine use of the facial nerve monitor supplements the surgeon's knowledge of temporal bone anatomy, the information provided by the preoperative HRCT, and provides another asset in making unilateral aural atresia repair safer for the patient."
Daniel I. Choo
Most otologic surgeons, even experienced ones, would agree that surgery for congenital aural atresia is challenging. Some submit that this procedure is inappropriate for unilateral cases, whereas others express no hesitation in recommending intervention to selected patients. The basis for this controversy has not been clearly articulated in the literature. In many cases, the bias has simply been inherited as part of the philosophy of one's training program. In order to provide more objectivity to this issue, several possible areas of concern need to be explored: (1) impact of unilateral hearing loss, (2) probability of achieving binaural hearing with surgery and stability of hearing results over time, and (3) surgical risks, especially to the facial nerve. The purpose of this chapter is to analyze these issues and draw conclusions regarding surgery for the unilateral atretic ear.
Both clinical and animal research have shown evidence of auditory brainstem abnormalities in the setting of unilateral conductive hearing loss. For example, Moore et al.6 have experimentally induced unilateral conductive hearing losses in ferrets during critical periods. Various abnormalities in the development of binaural neural elements in the auditory brainstem pathways were noted. Clinical studies of adults with unilateral conductive hearing loss using auditory brain stem responses (ABR) and the masking-level difference (MLD) have also documented abnormalities in brain stem auditory processing.7 Specifically, delays in wave V and in I to V and III to V interwave intervals were noted. The MLD, a behavioral test that measures the sensitivity of the auditory system to interaural differences of time and amplitude, was reduced, and they correlated significantly with the ABR abnormalities. These changes were similar to those observed in children with chronic otitis media with effusion.
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