Concurrent Bell's palsy and diabetes mellitus: a diabetic mononeuropathy?

In a series of 126 patients with Bell's palsy, chemical or overt diabetes mellitus was found in 39% of the cases. A high frequency of disturbances of taste was found in the patients who had no diabetes (83%), as compared to only 14% of diabetic patients whose taste was affected (p less than 0 .001). Thus, the usual site of facial nerve lesion in diabetics appears to be distal to the chorda tympani, while in patients whose glucose tolerance is normal, no such selectivity exists. This may only be explained by a diabetes-related pathogenesis and a vascular rather than a generalised "metabolic" impairment is postulated, leading to a localised facial nerve ischaemia in the distal part of the Fallopian canal. Thus, some cases of Bell's palsy may in fact be a diabetic mononeuropathy.