Comparative study of clinical and surgical findings and cortical somatosensory evoked potentials in patients with lumbar spinal stenosis and disc protrusion.

This paper is dealing with a comparative study of clinico-surgical findings and cortical somatosensory evoked potentials (CSEP's) recordings after stimulation of the right and left common peroneal nerve behind the fibula head, in twenty five patients suffering from lumbar spinal stenosis and disc prolapse. In all instances, the latencies of the first positive wave (the waveform also, when the latency was not discrete) were evaluated. The neurophysiological findings were verified by surgery. In combination with other roots, L3 root was affected in 1 patient, L4 in 6, L5 in 13 and S1 in 11. L5 was affected alone in 11 and L5 and S1 were impaired in combination in 11 patients. Seven patients presented sural atrophy. The results of the neurophysiological study are described below: There was delayed response on both sides in six patients, while in ten patients delayed response was found on one (affected) side, inconclusive responses in seven and in two normal. Myelography and CT Scan were performed pre-operatively to ascertain disc protrusion and establish stenosis criteria. The surgical findings were: clear disc protrusion in 4 patients, stenosis in one and combined lesions in 20 (including central disc protrusion in seven). Sixteen patients out of twenty-five had a follow up neurophysiological evaluation in addition to the clinical follow up examination. In thirteen of the above patients, (taken with the clinical progress) the re-examination gave improved neurophysiological data both as regards latency and P1 waveform. It was obvious that high value latencies were associated with long standing clinical symptoms while at the same time root compression involved more than one level. Regarding the neurophysiological data and the surgical findings, it was found that in the majority of the cases (92%) these two parameters matched together, so that in such cases a possible prediction of the operative outcome can be given.