Cochlear Nerve Deficiency and Brain Abnormalities in Pediatric Patients

Hypothesis: To investigate the intracranial abnormalities present in children with cochlear nerve deficiency (CND), including abnormalities of other cranial nerves, and to describe their auditory abilities. Background: The prevalence of CND has increased with the development of high resolution magnetic resonance imaging (MRI). There are varying degrees of CND from true aplasia to hypoplasia. The etiology of CND remains unclear and it may be associated with intracranial abnormalities in some instances. CND needs to be identified as early as possible to ensure prompt and adequate management of hearing loss since hearing aids and cochlear implants may not be an option. Methods: A retrospective chart review of 56 ears of pediatric patients with CND was conducted between August 2006 and November 2014 at a tertiary care pediatric hospital. Results: 27.6% of children had cochlear abnormalities and 48.9.8% had concomitant vestibular anomalies. Five patients had absent or abnormal facial nerves and two patients had aplastic bilateral olfactory nerves. In the 27 ears with an absent nerve that were functionally tested, eight (29.6%) had partial hearing which indicates the presence of an extremely small nerve whose size is below the limits of spatial resolution of the MRI. Conclusion: MRI is becoming the initial imaging choice for children with sensorineural hearing loss to identify CND and other brain anomalies. Concomitant vestibular and cochlear abnormalities were observed in respectively half and onethird of the pediatric patients with CND. The incidence of vestibular malformation suggests that balance testing should be recommended for most if not all CND patients.