Screening for Usher Syndrome in an established cochlear implant program: the merits of a collaborative paradigm

Abstract

Purpose: To evaluate the role of systematic ophthalmic assessment in children with sensori-neural hearing loss (SNHL) and peripheral vestibular impairment.

Methods: Twenty-three children with profound SNHL and bilateral vestibular dysfunction of unknown etiology were referred for an ophthalmic assessment to evaluate their risk for Usher syndrome. All children had received cochlear implants. Bilateral vestibular impairment was confirmed by clinical exam, abnormal vestibular end-organ testing (caloric, rotational chair and vestibular evoked myogenic potential testing) and poor static and dynamic balance was identified using the balance subset of the Bruininks-Oseretsky test of motor proficiency. Ophthalmic assessment included a comprehensive eye exam and electroretinography (ERG). Genetic testing and counseling were provided when appropriate.

Results: The average age at ophthalmic examination was 12.8 years (7-19 years). Over 75% had a refractive error warranting correction; only one had hypermetropia. Anisometropic amblyopia was seen in 2 cases. Half of the patients had an abnormal ERG suggestive of a rod cone dystrophy/retinitis pigmentosa (RP). Only a third of these cases had symptoms of decreased night vision while 80% showed some visual field constriction. Mutations of the MYO7A and CDH23 genes supported a diagnosis of Usher Syndrome type 1 in these patients.

Conclusions: The high prevalence of refractive errors (80%) and that of retinal dystrophies (50%) was higher than previously published in congenital SNHL. Children with SNHL with a vestibular deficit of unknown etiology should receive an ocular exam including ERG. This can contribute to the identification of the molecular cause and allows optimal genetic counseling.

Keywords: 696 retinal degenerations: hereditary • 539 genetics • 688 retina