Sept 2020 The Hearing Journal

Mitochondrial diseases are conditions caused by a mutation of the mitochondrial respiratory chain. It is often associated with a plethora of symptoms affecting the circulatory, neural, and skeletal and at times the sensory systems. Mitochondrial diseases, either in isolation or as a part of multisystem failure have presented with hearing loss caused by ATP defect. Such hearing loss has been commonly dubbed as mitochondrial deafness.

Kearns-Sayre Syndrome (KSS), a rare mitochondrial DNA deletion syndrome, is characterized by chronic progressive external ophthalmoplegia, cerebellar ataxia, a combination of cardiac conduction defects and progressive SNHL; it typically presents itself before the age of 20 years. 

We report a case of a 41-year-old cochlear implant user who presented with progressive hearing loss in both ears since the age of 15 years and recent bilateral profound hearing loss. 

A 41-year-old male presented with progressive hearing loss in both the years. The patient had a known case of KSS. In 1984, he underwent lamellar keratoplasty for his right eye, and in 1992, penetrating keratoplasty was done for his left eye. In 2000, he reported having reduced hearing in both ears. On evaluation, he was found to have bilateral moderate-to-severe sensorineural hearing loss and advised to use hearing aids. In 2014, he noted a significant progression of his hearing loss, and his audiological evaluation revealed bilateral severe-to-profound hearing loss. He was advised to get better hearing aids with advanced speech discrimination features. His speech perception improved with his new hearing aids. Over the past five years, he developed a tremor in the left upper limb but reported no cognitive decline.

In 2020, he experienced a sudden deterioration in hearing. On audiological evaluation, he was found to have bilateral profound hearing loss. He could not repeat spondee and PB words. Speech detection was reported at 100 dBHL. Impedance audiometry revealed a bilateral A-type tympanogram with ipsilateral and contralateral reflexes absent. DPOAEs were absent in both the ears. BERA results revealed no identifiable peaks even at 96 dBnHL click and tone burst (500 Hz) stimuli, suggestive of profound hearing loss. The aided responses were out of the speech spectrum.

A detailed speech and language evaluation was conducted. His speech and language skills were observed to be age adequate. His speech perception scores were significantly low. His revised Category of Auditory Perception (CAP) score was zero, and he was found to be unaware of environmental sounds.

The HRCT Temporal bone plane revealed normal bilateral ossicles and inner ear structures. Bilateral normal cochlear lumen. MRI findings revealed symmetric T2 hyperintensity in the bilateral caudate nucleus, globus pallidus, thalamus, anterior lentiform nucleus, frontoparietal white matter, and midbrain, including periaqueductal white matter cerebellar hemisphere and the middle cerebellar peduncle-favor mitochondrial encephalopathy. The inner ear structures were found to be normal.

After detailed audiological and speech and language evaluations, cochlear implantation surgery was recommended. The cochlear implantation surgery was carried out in the left ear with Advanced Bionics HiRes 90K Advantage CI HiFocus 1j electrode through a round window approach. During intraoperative measurements, impedance and Neural Response Imaging were obtained across all electrodes, except at the 9th electrode, which was an open circuit. 

The switch-on was done two weeks after the surgery. The impedance and NRI measurements were observed at all electrodes, except at the 9th electrode. Hence, instead of disabling the 9th electrode, SPAN was done,so that the patient could appreciate all channels.

Following the switch on, the patient started attending auditory training. After five months of therapy, he was observed to have a significant progression in speech perception. The revised CAP score at this point was 9, which suggested that he was able to understand conversations with unfamiliar people.

DISCUSSION

Hearing loss is one of the main manifestations of KSS syndrome. Speech perception data and electrophysiological responses among patients with KSS were similar to those obtained from non-KSS patients (Ear Hear. 2008;[3]:472-475. MED: 1838237). Literature is limited about cochlear implants results in this population; however, this case report suggests that CI can be considered as a favorable option for hearing rehabilitation of these patients.

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