THE RECORDING OF LATERAL POPLITEAL NERVE ACTION POTENTIALS IN MAN

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Abstract
As a means of evaluating patients with neurological disorders affecting the lower extremities the action potentials of the lateral popliteal nerve were recorded. The study was made on 39 control subjects and 35 patients with spinal cord or peripheral nerve lesions affecting the legs. The action potentials were much smaller than those previously recorded in the arm, consequently paired needle electrodes at the head of the fibula were used for recording with stimulation of the anterior tibial nerve at the ankle. In four control subjects the muscle action potential was recorded simultaneously from the extensor digitorum brevis. The conduction velocity was found to be greater in the sensory fibres than the motor fibres of the anterior tibial nerve. No significant differences were found in patients with multiple sclerosis. In patients with motor neurone disease nerve action potnetials were recorded even when the motor fibres had been destroyed. Abnormalities of the action potential were seen in cases of polyneuritis, localized lesions of the lateral popiteal nerve, subacute combined degeneration of the spinal cord and peroneal muscular atrophy. Polyphasic potentials were attributed to late components due to activity in slowly conducting fibres. It is concluded that the nerve action potential is a more sensitive index of disturbed function than the measurement of conduction time for the fastest surviving motor fibres.