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No Correlation Between IAC Diverticula Presence/Size and Degree of Hearing Loss

by Amy E. Hamaker •

What is the relationship between hearing loss and internal auditory canal (IAC) diverticula, and are diverticula within or medial to the otic capsule?

Bottom line: IAC diverticula size does not correlate with hearing loss degree, and there is no statistically significant association between SNHL and IAC diverticulum presence.

Background: Authors previously highlighted the association between IAC diverticula (small, nonvascular, low-density outpouchings from the normal linear contour of the IAC wall) and hearing loss, which occurred in 91% of the patients with IAC diverticula and no signs of fenestral or retrofenestral otosclerosis. This prompted the question: Does an IAC diverticulum itself cause hearing loss?

Study design: Retrospective review of adult patients with radiologic evidence of an IAC diverticulum, no evidence of otosclerosis, and audiometric testing between January 2013 and January 2016.

Synopsis: In the control group of 160 patients and 320 temporal bones, nine patients had bilateral IAC diverticula; their mean age was 61. In those with hearing loss, the majority of audiograms displayed a sloping curve similar to presbycusis. Forty-three temporal bones with an IAC diverticulum without radiographic evidence of fenestral or retrofenestral otosclerosis showed a mean pure tone average (PTA) of 50, a mean air-bone gap of 9, and a mean word recognition score of 67. Of these temporal bones, four of 43 showed no hearing loss; 27 of 43 showed sensorineural hearing loss (SNHL); 12 of 43 showed mixed hearing loss; and none showed conductive hearing loss. The mean diverticulum length was 0.95 mm, the mean width at mouth was 1.30 mm, and the mean width at middle was 0.95 mm. Spearman’s rho failed to show a correlation between diverticula measurements and audiometric data. There was a statistically insignificant difference between unilateral and contralateral diverticulum patients. Limitations included sampling bias innate to a case series.

Citation: Muelleman TJ, Pippin K, Shew M, et al. The size of internal auditory canal diverticula is unrelated to degree of hearing loss. Laryngoscope. 2020;130:1011-1015.