Incidence of subclinical trigeminal and facial nerve involvement in diabetes mellitus.

We investigated the frequency of subclinical trigeminal and facial nerve involvement in 40 patients with diabetes mellitus and without clinical signs of cranial nerve lesions. 60% of the patients had distal symmetric sensory polyneuropathy which was confirmed by nerve conduction studies. Trigeminal and facial nerve functions were evaluated electrophysiologically using the blink-reflex R1 component (BlinkR-R1), masseter reflex (MassR), the first exteroceptive suppression of the masseter muscle (Mass-ES1), and distal motor latency of the facial nerve (DML VII). Latencies were significantly prolonged for the BlinkR-R1 (p < 0.0001), the Mass-ES1 (p < 0.05), and DML VII (p < 0.005) in diabetics compared with controls. No significant difference was found for the MassR. Prolonged latencies (> mean + 2.5 SD of age-matched controls) were demonstrated for the Mass-ES1 in 12.5%, BlinkR-R1 in 10%, DML VII in 6.2%, and MassR in 5% in individual of patients. Our findings indicate that trigeminal and facial nerve involvement is not infrequent in diabetics, although it is significantly less frequent than limb nerve involvement.