Inner ear changes in mucopolysaccharidosis type I/Hurler syndrome

Objective: Mucopolysaccharidosis type I/Hurler syndrome is an autosomal recessive disease caused by a deficiency of α-L-iduronidase activity. Recurrent middle ear infections and hearing loss are common complications in Hurler syndrome. Although sensorineural and conductive components occur, the mechanism of sensorineural hearing loss has not been determined. The purpose of this study is to evaluate the quantitative inner ear histopathology of the temporal bones of patients with Hurler syndrome. Patients: Eleven temporal bones from 6 patients with Hurler syndrome were examined. Age-matched healthy control samples consisted of 14 temporal bones from 7 cases. Main Outcome Measures: Temporal bones were serially sectioned in the horizontal plane and stained with hematoxylin and eosin. The number of spiral ganglion cells, loss of cochlear hair cells, area of stria vascularis, and cell density of spiral ligament were evaluated using light microscopy. Results: There was no significant difference between Hurler syndrome and healthy controls in the number of spiral ganglion cells, area of stria vascularis, or cell density of spiral ligament. The number of cochlear hair cells in Hurler syndrome was significantly decreased compared with healthy controls. Conclusion: Auditory pathophysiology in the central nerve system in Hurler syndrome remains unknown; however, decreased cochlear hair cells may be one of the important factors for the sensorineural component of hearing loss.