Use of mammalian inner ear antigens for the diagnosis of autoimmune sudden loss of vestibular function

It has been postulated that bilateral sensorineural hearing loss (SNHL) may be the result of an ongoing autoimmune process against the inner ear and a pattern of progressive bilateral SNHL linked to an autoimmune inner ear disorder has been reported. Various attempts have been made to develop an assay to confirm the diagnosis of autoimmune inner ear disease. In this study we used a Western blot assay to determine the presence of IgG antibodies directed against a P∅ antigen (30 kDa) of the guinea pig in the sera of patients affected by sudden loss of vestibular function (SLVF). Ten patients affected by vestibular neuritis were enrolled: eight with unilateral vestibular loss and two with sequential bilateral impairment. We also tested nine patients with sudden unilateral hearing loss, five with benign paroxysmal positional vertigo and six normal subjects. In the present study only one patient, a woman affected by bilateral vestibular impairment, had IgG antibodies against the P∅ protein. Our results indicate either that the antigen P∅ is not a valid marker for autoimmune unilateral SLVF or that our patients did not have an immunological basis for their disease. However, we can suggest that bilateral impairment of vestibular function and bilateral progressive SNHL are more likely to be immune-mediated disorders and that P∅ could be a valid marker for these diseases. As bilateral vestibular neuritis is an uncommon disease, a multicentre study is required to confirm our suggestions.