We report a case of painless progressive leg amyotrophy without intermittent claudication due to spinal lumbar stenosis. Our attention was drawn to the lumbar region because of the discrepancy between normal leg sensory potentials and altered somatosensory evoked potentials, prompting us to perform a myelography. The rapid though partial, clinical improvement following decompressive surgery suggested that some of the symptoms may have been due to a reversible nerve conduction block