Somatic and autonomic nerve function during the first year after diagnosis of type 1 (insulin-dependent) diabetes

Somatic and autonomic nerve function was assessed by motor and sensory nerve conduction velocities (MNCV; SNCV), beat-to-beat variation at rest, speed of pupillary dilation, and pupillary latency time in 35 newly diagnosed type 1 diabetic patients aged 12-36 years. The nerve function tests were performed 18 +/- 2 (mean +/- SEM) days after the correction of initial ketosis and hyperglycaemia and again after 3 and 12 months of insulin therapy. Mean HbA1 levels of months 3 and 12 within the normal range less than 8.6% (mean: 7.2 +/- 0.2%) were observed in 24 patients (group 1) and greater than or equal to 8.6% (mean: 10.1 +/- 0.6%) in 11 patients (group 2). Group 1 showed no significant changes from baseline in the mean nerve conduction and autonomic functions after 3 and 12 months. In group 2 there was no change until three months, however, at 12 months there was a significant decrease in mean MNCV in the median, ulnar and peroneal nerves (p less than 0.05) and in mean SNCV in the median (p less than 0.05) and sural nerves (p less than 0.01), when compared to the baseline values. The autonomic function tests remained unchanged. No patient had symptoms of neuropathy during the period studied. These findings suggest that the deterioration of motor and sensory nerve conduction precedes that of cardiac and pupillary autonomic function in poorly controlled asymptomatic type 1 diabetic patients during the first year of the disease. Effective glycaemic control prevented progression of subclinical neuropathy, but did not reverse abnormalities which were present at diagnosis.