Lateral semicircular canal dilatation in a patient with congenital hearing loss due to α-tectorin mutation: microanatomical considerations.

The tectorial membrane is crucial in the physiology of the auditory neuroepithelium. Mutations in one of its functional molecules, α-tectorin, lead to autosomal dominant and recessive congenital mid-frequency, non-syndromic hearing loss.Typically, α-tectorin mutations are not accompanied by any morphological abnormalities of the labyrinth. For the first time, we present a case of a toddler boy with congenital hearing loss due to gene mutation and concomitant bilateral dilation of the lateral semicircular canals.The expression of glycoproteins, like α-tectorin, varies between the distinct labyrinth acellular membranes. Various mutations in the gene may affect additional glycoproteins that share a high percentage of sequence similarity at the amino acid level with α-tectorin. The mutated glycoproteins differ in the hydration level of their side chains of glycosaminoglycans. Hydration level could affect the mass of the ampullary cupula of the lateral semicircular canal leading to its dilation during embryogenesis.