Clinical Features of Unilateral Cochlear Nerve Deficiency

Abstract

Objective: Cochlear nerve deficiency (CND) is increasingly recognized as a cause of sensorineural hearing loss. Our objectives were to 1) describe the clinical and genetic features of children with unilateral CND, 2) understand the relationships to other features on imaging, and 3) determine if either the IAC or bony cochlear nerve canal (BCNC) could predict CND.

Method: Clinical and genetic data were reviewed in 66 children with unilateral CND, defined either by our MRI criteria or by atresia of the BCNC. Temporal bone imaging was reviewed for any additional anomalies. BCNC and IAC diameters were compared with CN size by regression analysis.

Results: In most patients, the cochlear division was the only branch involved (72%). Associated labyrinthine anomalies were uncommon (21%). Most children (71%) were non- syndromic. Of the 9 with syndromes, 2 each had 22q11.2 deletion, Down syndrome, and VACTERL, and 1 had a mild form of CHARGE syndrome. BCNC width correlated significantly with CN size (r² 0.50, P < .0001). Though only 61% sensitive for CND, it was 100% specific. Size of the IAC was highly variable and showed no relationship to CN size.

Conclusion: Most cases of unilateral CND appear sporadic and non-syndromic, with no other anomalies of the temporal bone. Nevertheless, it can occur as part of certain syndromes. CT is only useful in diagnosis if it shows a stenotic cochlear aperture, which strongly predicts CND. However, CT alone will miss the diagnosis in 39% of cases.