Compound muscle action potentials (CMAPs) were recorded in tibialis anterior, extensor digitorum brevis and abductor hallucis elicited by stimulation of the cauda equina. We examined twenty patients with intermittent claudication due to lumbar canal stenosis. For the purpose of analyzing the alteration on the cauda equina propergation, we recorded the CMAPs before walking and immediately after onset of the intermittent claudication, and then continuously recorded them every few seconds.
In all patients the latency of CMAPs showed no changes after walking stress. But in fifteen patients of twenty the amplitude decreased by various degrees immediately after walking stress and gardually made recovery to the control.
The decreased amplitude of CMAPs was reflected the impairment of the motor axons.
We conclude that the temporary conduction block of the cauda equina and/or lumbar nerve root occurs in the imtermittent claudicaion of the lumbar canal stenosis.
