Neurophysiological evidence for altered higher brain functions in NIDDM

To investigate neurophysiological alterations of higher brain function in patients with NIDDM.

Auditory P300 event-related potentials were recorded in 60 NIDDM patients who had no evidence of stroke, dementia, or any other neurological illnesses. The P300 wave latencies in diabetic patients were compared with those in neurologically healthy control subjects, with consideration of clinical parameters and diabetic complications.

Diabetic patients had significantly longer P300 latencies than control subjects. Seven diabetic patients had pathologically prolonged P300 values. There was a trend toward longer P300 latencies in diabetic patients with retinopathy and in those with HbA1 of > or = 10%; the differences between these diabetic subgroups and control subjects were both statistically significant. However, three of seven diabetic patients with abnormal P300 latencies had no retinal lesions, and no significant correlation was observed among diabetic patients between P300 latencies and HbA1 levels. Peripheral neuropathy, nephropathy, blood glucose levels, and disease duration appeared not to correlate with P300 alterations.

These findings suggest the presence of central nervous pathological processes in NIDDM that affect higher brain functions, as assessed by P300 latencies. Our findings also suggest that microangiopathy and metabolic derangement during the preceding 4- to 8-week period may contribute in small part to the pathophysiology of this central nervous involvement.