Predisposing factors in Bell's palsy: a case-control study.

The frequency of diabetes mellitus reported in subjects affected by Bell's palsy varies widely. In this investigation, a case-control study, we encountered a frequency of 24.8%. In addition, arterial hypertension and lipid disturbances were found to affect subjects with Bell's palsy more frequently than controls. These findings appear to suggest a primarily ischaemic pathogenesis for most cases of idiopathic peripheral facial paralysis. Furthermore, the finding of significantly lower taste impairment in diabetics than in non-diabetics with Bell's palsy may support the hypothesis of a vascular rather than a metabolic pathogenesis in these cases also. In fact, the vessels supplying the distal portion of the facial nerve, probably more affected in the diabetic patients in order to preserve taste sensation, have such a particular anatomical configuration that this might favour the onset of a diabetic small vessel disease which, in turn, would represent a factor of easier decompensation.