Secondary changes in segmental neurons below a spinal cord lesion in man.

The function of sensory and motor neurons below the level of a spinal cord injury (SCI) was assessed in 23 patients by recording the nerve conduction velocities and the amplitudes of evoked nerve and muscle compound action potentials for sural and posterior tibial nerves. Sensory and motor conduction velocities were generally normal when obtainable. Two patients had a unilateral reduction in the sural nerve and abductor hallucis muscle compound action potentials which may have been due to peripheral nerve compression. In 11 patients the abductor hallucis muscle compound action potential was below the normal range, while sural nerve action potentials remained within the normal range. Motor unit counts showed a reduction in the number of functioning motor units in these muscles.