Cochlear implantation in deafness-dystonia-optic neuronopathy (DDON) syndrome.

To report the results of the first known cochlear implantation in a patient with deafness-dystonia-optic neuronopathy (DDON) syndrome (Mohr-Tranebaerg syndrome, DFN-1). DDON syndrome is an X-linked condition characterized by postlingual sensorineural hearing loss in early childhood followed by dystonia, psychosis, and optic atrophy in adolescence and adulthood. The gene responsible for the condition maps to Xq22 adjacent to the gene causally related to X-linked agammaglobulinemia. The audiometric characteristics of DDON syndrome are typical of auditory neuropathy, with spiral ganglion cells being the suspected site of pathology. Performance following cochlear implantation in auditory neuropathy patients is variable and has yet to be reported in any patients with DDON syndrome. The reported case describes a male initially diagnosed with X-linked agammaglobulinemia due to recurrent infections. Speech, language and hearing were typical of a child in the first year of life; however profound hearing loss developed and cochlear implantation was performed at age 4. Following implantation, further genetic workup determined that the patient carries a deletion that includes BTK and DDP1/TIMM8a, consistent with the diagnosis of X-linked agammaglobulinemia and DDON syndrome. The patient's performance with the cochlear implant was marginal even after 2 years of use, with continued poor scores in standardized speech, language and audiometric tests. Additionally, his most-comfortable-level implant setting requires higher-than-normal current applied to the electrode array. This case report supports other studies showing that DDON syndrome results in an auditory neuropathy. Further investigation is required to determine the efficacy of cochlear implantation in this patient population. DDON syndrome should be considered in patients with X-linked agammaglobulinemia and hearing loss.

Deletion of and novel missense mutation in POU3F4 in 2 families segregating X-linked nonsyndromic deafness.

OBJECTIVE: To analyze the physical manifestations and genetic features of 2 families segregating X-linked deafness, which is most commonly reported to be caused by mutations of the POU domain gene POU3F4 at the DFN3 locus. DESIGN: Computed tomographic study of the temporal bone in probands from each family, followed by mutation screening and deletion mapping of POU3F4 in family members. SETTING: Two midwestern genetics clinics. PARTICIPANTS: Two families with X-linked deafness. MAIN OUTCOME MEASURES: Anomalies of the inner ear in the probands; results of gene mapping and severity and effects of hearing loss in the family members. RESULTS: In the first family, a large deletion was identified that includes POU3F4 and extends upstream approximately 530 kilobases; in the second family, a novel serine-to-leucine (S228L) amino acid mutation was identified in the POU-specific domain of POU3F4. Both the deletion and the missense mutation segregate with the clinical phenotype and are causally related to the deafness in these families. CONCLUSIONS: Deafness related to the POU3F4 gene is associated with dilation of the internal auditory canal and a spectrum of other temporal bone anomalies that range in severity from mild to severe dysplasia of the cochlea and semicircular canals. The consequence of these anomalies is a congenital mixed hearing loss, the sensorineural component of which progresses over time. Affected males can also present with vestibular dysfunction that is associated with delayed developmental motor milestones. Intrafamilial variability occurs.