Objectives: Norrie disease is an X-linked recessive disorder in which patients are born blind and develop sensory hearing loss in adolescence. The hearing loss associated with Norrie disease has been shown in a genetically altered knockout mouse to involve dysfunction of the stria vascularis; most other structures are preserved until the later stages of the disease. The objective of this study was to characterize the audiologic phenotype of Norrie disease for comparison with the pathophysiologic mechanism.
Methods: The design combined two series of clinical audiologic evaluations, with special attention to speech intelligibility.
Results: The audiologic results for 12 affected individuals and 10 carriers show that patients with Norrie disease retain high speech intelligibility scores even when the threshold loss is severe.
Conclusions: The cochlear mechanism-- failure of the stria vascularis-- accounts for some of the higher values in the wide distribution of speech scores in cases with similar pure tone audiograms.