[Severe motor weakness associated with lumbar spinal stenosis. A retrospective study of a series of 61 patients]

Severe motor weakness is a rather infrequent symptom in the course of lumbar stenosis. The objectives of this study are three fold: describe the motor deficit, evaluate the prognosis factors and determine the type of stenosis the most likely to be complicated by motor loss.

61 consecutive patients with a mean age of 63 years, operated on for a lumbar stenosis and with a severe motor deficit have been retrospectively studied. The mean follow-up was 38 months. The overall functional result was evaluated according to a rating scale, specially developed in our unit for the follow-up of lumbar stenosis. The motor capacity was rated from 0 (complete paralysis) to 5 (normal strength). According to that scale the motor weakness was rated as 0, 11 times as 1, 11 times, as 2, 11 times and as 3, 28 times. The deficit was unilateral in 79 per cent of cases and multiradicular in 58 per cent of patients. Sphincter abnormalities were also present in 9 cases. In 9 out of 10 patients the motor deficit was in the L5 territory. Stenosis was extended to 3 levels in 30 cases and was focal in the remaining cases. Degenerative spondylolishthesis was disclosed in 20 patients. In 3 out of 4 cases decompression was performed after 3 weeks of motor weakness and within 3 weeks in the remaining cases.

According to our rating scale the overall results were considered excellent in 29 cases, good in 21 cases and fair in the 11 remaining cases. There was no complication, and no postoperative worsening of the deficit was observed. Regression of motor weakness was complete 22 times, partial 29 times and null 10 times. In the eleven complete deficits with a 0 cotation one receded completely, 7 receded partially and no improvement was noted in the 3 remaining cases. 6 out of the 9 patients with sphincter abnormalities recovered completely. In this study favourable prognosis parameters were as follows: age under 62 years, monoradicular deficit, stenosis at one level and association with a discal herniation. In contrast, severity of the initial motor weakness, association with sphincter abnormalities, presence or not of degenerative spondylolisthesis, or of a complete block on the myelogram were not influential variables. Chances of recovery were statistically diminished when decompression was performed after 6 weeks.

No study dealing specifically with the postoperative outcome of motor deficit caused by lumbar stenosis has been published. However the rate of motor recovery (complete or partial) disclosed in our series is comparable with that found in other series dealing more generally with the overall post-surgery outcome. At our last follow-up, 82 per cent of our patients were considered as having an excellent or good result. It can be concluded that the existence of a motor deficit is not a major pejorative factor of the overall final functional result. Motor weakness is more frequently observed in elderly patients, in cases with degenerative spondylolisthesis, or when a discal herniation is associated with a bony compression. Chances of recovery are better, when the deficit is monoradicular, when the stenosis is focal, or associated with a discal herniation and when the patient is relatively young.