MOTOR PATHWAY FUNCTION IN NORMOALBUMINURIC IDDM PATIENTS

Central motor pathways were studied in 17 normoalbuminuric insulin-dep endent diabetic (IDDM) patients who had been diabetic for more than 20 years, and compared with findings in 17 age-, sex-, and height-matche d control subjects. The central motor conduction time was calculated f rom recordings of the compound muscle action potentials of the abducto r pollicis brevis muscle after single transcranial,and spinal root mag netic stimulation. The central motor conduction time from motor cortex to cervical spinal roots was 9.8+/-1.65 ms in diabetic patients and 1 0.1+/-1.48 ms in control subjects. In diabetic patients with neuropath y the central motor conduction time was 9.5+/-1.76 ms vs 10.1+/-1.56 m s in patients without neuropathy. The excitability of the motor pathwa ys was studied by paired transcranial magnetic stimulation at intersti mulation intervals of 30-1000 ms, In normal control subjects, an early facilitation of the amplitude of the compound muscle action potential at an interstimulation interval of 30 ms was found, while no facilita tion was present in diabetic patients. In addition the compound muscle action potential latencies were prolonged at interstimulation interva ls of 30-50 ms in diabetic patients. The changes of excitability did n ot correlate with the presence of peripheral neuropathy, metabolic con trol or diabetes duration. It is concluded that long-term normoalbumin uric IDDM patients have impaired excitability but normal central condu ction time of the motor pathways.