Facial nerve conduction in diabetic neuropathy.

Diabetes mellitus (DM) has a severe influence on the nervous system and it is more likely to occur on the nerves of the upper and lower extremities than on the cranial nerves. According to the statistics, the incidence of cranial nerve involvement ranges anywhere from 3% to 14%. The aim of this study is to perform facial nerve conduction studies in diabetic patients with peripheral neuropathy, confirmed by electrophysiological methods, to determine the frequency of affection of a cranial nerve conduction in a neuropathy which mainly occurs in a distal, symmetric fashion. The study was conducted in a group of 20 diabetics who had electrophysiologically confirmed polyneuropathy. All of the patients had type 2 DM. Sixteen of the patients were receiving insulin therapy and 4 were treated with oral hypoglycaemic agents only. We found prolonged facial nerve distal latency at least on one tested side in 70% of patients. Distal latency and amplitudes of muscle responses to facial nerve stimulation showed a statistically significant difference from controls (p < 0.001). This study has shown that proximal nerves like cranial nerves are affected in a high proportion of cases in a neuropathy which mainly occurs in a distal symmetric fashion. The facial nerve is one of the most easily accessible nerves in the proximal part of the body (head-face) and makes it suitable for routine evaluation. We believe this conduction abnormality may give us the chance to classify these neuropathies as more severe than the ones that only have limb conduction abnormalities. Further studies should be performed in order to confirm these findings.