Cochlear Implantation in Biotinidase Enzyme Deficiency.

Metabolic syndromes associated with hearing loss are rare and are characterized by specific enzyme pathway deficiencies involving lysosomal storage, peroxisomes, fatty acid enzymes, organic acids and amino acids. The deficiency of biotinidase, an enzyme involved in the metabolism of biotin, is one such rare cause of congenital hearing loss estimated at 1:60,000 newborns. The parents of a 5-year-old girl presented to the clinic with complaints that she was hard of hearing with no speech development. At age 2 she had been diagnosed with organic aciduria and hydronephrourethrosis and was operated for renal calculi. Clinical examination showed periorificial scaly skin lesions and eczematous otitis externa. An audiological evaluation showed bilateral profound SNHL. Imaging and routine investigations were unremarkable, except for a mild low anion gap metabolic acidosis. General anaesthesia involved avoidance of neuromuscular agents due to the risk of inducing hypotonia. Surgery consisted of cortical mastoidectomy followed by the facial recess approach. A standard electrode array was inserted via the round window technique and complete atraumatic insertion was achieved. Intraoperative electrode impedance and NRT tracings were good. Hearing loss in biotinidase deficiency may be expected to be of progressive nature and regular evaluation of hearing and speech is required. Cochlear implantation is currently the best available solution for severe to profound hearing loss in this disorder although the enzymatic pathology affects the entire auditory pathway. Biotin supplementation is required lifelong for its management.