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[OTOF-related auditory neuropathy spectrum disorder].

Otoferlin (OTOF) gene mutations are the most common cause of hereditary ANSD according to investigations in several countries.


THE AIM
Of this study was to estimate the prevalence of OTOF mutations in Russian children with ANSD and evaluate audiological and clinical features of OTOF-related ANSD.


PATIENTS AND METHODS
28 children with bilateral ANSDwere enrolled in the investigation. Two step genetic testing was performed: first step - GJB2 gene testing to exclude GJB2-related hearing loss; second step - NGS-based sequencing to explore another 35 hearing loss genes (including OTOF).


RESULTS
OTOF mutations, including 6 new variants, were found in 5 children with ANSD (18%). All 5 children had no risk factors for hearing loss and passed hearing screening. OAE and cochlear microphonics were present till the last testing at the age of 4-5 years. ABR were not detectable. The ASSR were measurable bilaterally at all frequencies in all cases, but they did not correlate with behavioral thresholds that revealed severe hearing loss. Hearing thresholds were stable during follow up period. 3 children underwent cochlear implantation. After cochlear implantation auditory nerve action potentials to electric stimulation were detected within normal range.


CONCLUSION
Genetic testing of children with ANSD and first of all OTOF testing enables to reveal hearing loss etiology and provide the optimal rehabilitation approach, including cochlear implantation, as early as possible.