Motor cortical excitability remains unaffected of short-term hyperglycemia in Type 1 diabetic patients

In diabetic patients, hyperglycemia may precipitate seizures, and in experimental diabetes, indications for an increased neuronal excitability have been found. In this study, the excitability of the motor cortex and conduction of the central motor pathways were studied in diabetic patients in relation to the glycemic level.

Using a double-blind study protocol, transcranial magnetic stimulation (TMS) was performed in five Type 1 diabetic patients during normo- and hyperglycemia, using a hyperglycemic clamp technique. Single and paired-pulse transcranial magnetic and single root stimulations were applied before and after 3 h of a fixed glucose level of 5 and 16 mmol/l. The percentage of change from baseline at the two glycemic levels was calculated and compared.

No difference in central motor conduction time was found comparing the change following normo- and hyperglycemia. Furthermore, no difference was observed for the changes in latency and amplitude following double stimulation with interstimulation intervals (ISIs) of 0-125 ms comparing normo- and hyperglycemia.

The excitability of motor cortex and central motor nerve conduction in Type 1 diabetic patients are unaffected by short-term moderate hyperglycemia as compared with normoglycemia.