Reply to ‘Migraine,sudden sensorineural hearing loss and autoimmune ear disease’

We thank Drs Espinosa-Sanchez and Lopez-Escamez (1) for showing interest in this study (2). He questioned first that autoimmune inner ear diseases may explain the differences in the incidence rates of sudden sensorineural hearing loss (SSNHL) between migraine and the matched control groups. We would like to declare that it is important to ensure high validity while using a population-based claim dataset. We excluded cases with Meniere’s disease (MD) any time in the study period because the first attack of MD in some patients might be misdiagnosed as SSNHL (3). Furthermore, the comorbidity of migraine and MD has been reported (4). Therefore, we excluded MD cases to minimize the confounding effect of MD that links migraine and SSNHL. In contrast, patients with autoimmune diseases are not excluded in our study because the role of autoimmune diseases in SSNHL remains speculative and the specific immunologic markers for autoimmune inner ear disease are not determined (5).

The second question is about the consideration of vestibular migraine (VM). We did not exclude patients with VM because there is no formal coding for it in the International Classification of Diseases, Ninth Revision, Modification (ICD-9-CM). In fact, the diagnosis of VM is not adopted in the International Headache Classification, 2nd edition (2004) either (6).

The last question is that the incidence of MD reported here seems too high. Actually, it had been reported that the annual incidence ranged from 8.2 to 157 per 100,000 (7). The incidence rate of MD in our study, 168 per 100,000 (227 MD in 13,532 migraine patients during the 10-year follow-up), was reasonable since this incidence was estimated from a migraine cohort with female predominance.