Neurophysiological investigations in patients with diabetes mellitus: combined assessment of the pattern reversal visual evoked potentials and nerve conduction velocity

One hundred three diabetic patients of both type I and type II D.M were evaluated for the evidences of optic nerve and peripheral neuropathy based on the clinical and electrophysiological criteria. One hundred seventy three randomly selected non-diabetic subjects were included as the control group. Single and scattered symptoms and signs of polyneuropathy were found in both type I and type II diabetic patients. Symptomatic polyneuropathy was found in 68% of the diabetic subjects,' while polyneuropathy defined by clinical signs was found in 65% of them. Visual evoked potential (VEP) was performed to assess the optic nerve function taking in consideration the P-100 wave latency and N75-P100 amplitude. The results of this study showed significantly prolonged P-100 wave latency and significantly reduced N75-P100 amplitude in both type I and type II D.M patients No relationship was be observed between the age of patients, type of D.M, metabolic control and both the P-100 wave latency and N75-P100 amplitude. While, a significant correlation was found between the P-100 wave latency and the duration of illness (1-5 years and > 10 years). / Diabetic patients complicated with retinopathy showed lower N75-P100 implitude values than those without retinopathy although they were statistically insignificant. They expressed significantly prolonged P-100 wave latency as com­pared with those without retinopathy. The SCV and MCV of both the ulnar and peroneal nerves was evaluated in §fder to define diabetic patients who were complicated with peripheral neuropa- thy. Diabetic patients showed significantly reduced SCV and MCV of both nerves in comparison with the control group. No relationship was found between the NCV of both nerves and the age of the patient. A significant difference in the mean ulnar SCV was noticed between diabetics with and without clinically evident neuropathy. Moreover a significant difference was observed in the mean SCV of the ulnar nerve at different duration of illness. An inverse correlation was found between peroneal nerve MCV and FPG level. The EMG findings were more common in the diabetic patients than control group. No relationship was noticed between the optic nerve dysfunction and both the ulnar and peroneal nerves SCV and MCV.