Axonal excitability during ischemia in MELAS.

INTRODUCTION

In mitochondrial disease, it is likely that energy substrate depletion leads to paralysis of ATPase-dependent pumps, resulting in membrane depolarization. Axonal depolarization has been demonstrated in a crisis, but not in the resting state. We, therefore, stressed axons using ischemia to see if this would reveal abnormal responses, as occurs in diabetes mellitus.

METHODS

Excitability of median nerve axons at the wrist was studied in 13 patients with MELAS (6 with glucose intolerance) and 17 control subjects in response to ischemia due to inflation of a cuff around the arm for 10 min.

RESULTS

There were no significant differences in preischemic measures of axonal excitability or in the intra- and postischemic responses.

CONCLUSIONS

Although depolarization has been noted to occur spontaneously during a crisis, we could not demonstrate a defect of axonal ATP-dependent mechanisms. The mechanisms underlying axonal excitability and neuropathy in diabetes may not apply to MELAS.