Nonsyndromic Isolated Unilateral Cochlear Nerve Aplasia without Narrow Internal Auditory Meatus: A Previously Overlooked Cause of Unilateral Profound Deafness in Childhood

Abstract

Juvenile or adolescent unilateral profound sensorineural deafness (worldwide prevalence, 0.1% to 0.2%) has been attributed to postnatal viral infection, sudden deafness, prenatal and perinatal problems including maternal rubella and viral infections, congenital innerear anomalies, and other factors. Herein, 2 cases are reported and another potentially important cause of unilateral profound hearing loss is proposed. Two nonsyndromic cases of a presently "very rare" cause of pediatric unilateral deafness are presented as a retrospective case study. The 2 patients showed isolated aplasia of the cochlear nerve; other branches of the eighth cranial nerve, the seventh nerve, and the inner ear were spared,and there was no anomaly of the internal auditory meatus. Both functional and imaging studies confirmed the isolated lesion (absence) of the cochlear nerve. Because of the absence of bony abnormalities, such cases may have been overlooked. The authors would like to advocate this isolated anomaly of thecochlear nerve as an important cause of juvenile or adolescent unilateral profound deafness.