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Preserved motor axonal membrane potential in mitochondrial disease
  1. K Ng1,2,
  2. S Winter1,3,
  3. C Sue1,3,
  4. D Burke2
  1. 1Department of Neurology and Clinical Neurophysiology, Royal North Shore Hospital, Sydney, Australia
  2. 2Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, The University of Sydney, Sydney, Australia
  3. 3Department of Neurogenetics, Kolling Institute, Royal North Shore Hospital, The University of Sydney, Sydney, Australia
  1. Correspondence to Dr Karl Ng, Department of Neurology and Clinical Neurophysiology, Royal North Shore Hospital, St Leonards, NSW 2065, Australia; kng{at}


Mitochondrial disorders are characterised by protean neurological manifestations including peripheral neuropathy. The neuropathy is typically an axonal process, with a proposed mechanism being degradation of the membrane potential of the axon due to dysfunction of energy-dependent Na+/K+ ATPase pump. To address this issue, we studied the excitability of motor axons in the median nerve in 16 individuals identified with gene testing or muscle biopsy. Twelve patients had clinical or nerve conduction abnormalities. Strength–duration time constant, threshold electrotonus, current–threshold relationship and recovery cycle were identical to control values. These findings imply that an alternative mechanism to a change in membrane potential is responsible for neuronal injury in these patients.

  • Nerve excitability
  • mitochondrial disease
  • peripheral neuropathy
  • membrane potential

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  • Funding National Health and Medical Research Council of Australia (ID No. 521316) and the Royal Australasian College of Physicians Glaxo-Smith-Kline Fellowship.

  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the University of Sydney and the Northern Sydney Central Coast Health Area Service.

  • Provenance and peer review Not commissioned; externally peer reviewed.