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The Spine Blog

Friday, March 22, 2019

Does immediate discectomy improve motor outcomes for patients with weakness?

The urgency of lumbar discectomy for patients with significant motor weakness has been debated, with most studies on the topic demonstrating minimal benefit for more urgent decompression. However, there is some evidence that decompression in under 48 hours following the onset of cauda equina syndrome leads to better functional outcomes. No study has looked at the role of immediate surgery for lumbar disc herniation associated with motor weakness, likely because few discectomies are performed in under 48 hours of the onset of weakness. In order to assess the effect of immediate discectomy on motor outcomes, Dr. Petr and colleagues from Innsbruck retrospectively reviewed a series of 330 lumbar disc herniation patients who presented with motor deficit. They divided the patients into two cohorts depending on whether they underwent surgery within 48 hours of the onset of weakness or beyond 48 hours. The immediate surgery group included 126 patients, while the delayed surgery group included 204. There were no significant demographic or baseline clinical differences between the two cohorts. Approximately 60% of the herniations were at L4-L5 and about 20% were at L5-S1. Twenty-four percent of patients had mild (grade 4/5) weakness, 53% had moderate (grade 3/5) weakness, and 23% had severe (grade 0-2/5) weakness. Postoperatively, the immediate surgery group had a greater improvement in motor strength at discharge, 6 weeks, and 12 weeks follow-up.  The difference was not significant for the mild weakness group, in which 96% of the immediate surgery group had complete resolution of motor weakness at 12 weeks compared to 86% in the delayed surgery group (p=0.22). The differences were significant in the moderate and severe weakness groups, with 96% of the severe weakness group undergoing immediate surgery having complete resolution at 3 months compared to 64% of the delayed surgery group. The immediate surgery group also had greater resolution of sensory deficits. There were no differences in the rate of residual sciatica between the immediate and delayed surgery groups.

The authors have presented a thorough retrospective analysis of their lumbar discectomy cohort that suggests that discectomy patients with a preoperative motor deficit have greater recovery of motor function if their surgery is performed within 48 hours of the onset of the deficit. While this intuitively makes sense, prior studies have not consistently demonstrated this. One reason for this discrepancy is that prior studies tended not to look at the effect of immediate surgery within 48 hours of symptom onset as surgery is rarely performed this quickly for logistical reasons. It is impressive that the authors were able to perform surgery within 48 hours on over 1/3 of their lumbar discectomy patients with motor deficits. The authors point out that this is not an RCT, so no strong conclusions regarding causation can be drawn. One limitation is that they did not report the duration of symptoms for patients undergoing surgery beyond 48 hours after the onset of symptoms. It is possible that some of these patients had long-term motor deficits (i.e. months or more), and these were probably less likely to improve. Many patients present with an acute motor deficit that resolves relatively quickly without surgery, so it is not clear to what degree immediate surgery changed the natural history of the motor deficit. Given that the timing of surgery was not randomized, the two groups were likely different at baseline in ways not measured by the study. A future study RCT comparing immediate surgery to delayed surgery and no surgery would answer the question, though it is not clear that such a study would ever be performed due to ethical concerns and strong patient preferences. I see very few patients in my practice who present with a motor deficit that has been present for less than 48 hours, primarily due to logistical issues around referrals and imaging. For that reason, I am not sure that immediate surgery is even logistically feasible for most healthcare systems.

Please read Dr. Petr's article on this topic in the April 1 issue. Does this change your view on immediate surgery for lumbar disc herniation with motor deficit? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor