Does Early Surgical Decompression in Cauda Equina Syndrome Improve Bladder Outcome?: Comments on a Recent Study by Srikandarajah et al.

STUDY DESIGN AND OBJECTIVES: This study by Srikandarajah et al is a retrospective cohort study of 200 CES patients. Although parts of the study appear to be well done we identified serious problems that impacted their conclusions. SUMMARY OF BACKGROUND DATA: There is strong consensus that patients with incomplete cauda equina syndrome (CESI) should be operated upon expeditiously to prevent progression to CES with urinary retention (CESR). There is controversy concerning optimal timing of surgery in patients who have entered CESR. Some studies conclude urgent surgery for CESR does nothing to improve chance of recovery; others conclude surgery should be done within a 48 or 24-hours window after onset of bladder paralysis. Srikandarajah et al concluded that in CESI patients, decompressive surgery within 24 hours of onset of autonomic symptoms reduces bladder dysfunction at follow-up. In CESR patients, "no statistically significant difference in outcome was observed" regarding timing of surgery. METHODS: We analyzed the methods used by Srikandarajah et al to collect and analyze their data. RESULTS: The primary problem with their study is that it does not consider deterioration to CESR that occurs in CESI patients over time. We also found serious problems with the methods, implementation (including numeric errors), and interpretation of the statistical analysis. CONCLUSION: The authors' conclusion that in CESR patients, "no statistically significant difference in outcome was observed" regarding timing of surgery is not justified as a representation of their findings, because absence of statistical significance does not mean acceptance of the null hypothesis of "no effect". Their numeric results do show elevated risk of delay. We do not want to detract from the basic importance of this study, because it emphasizes the importance of operating expeditiously on patients with CESI. However, the authors' conclusions are compromised by the methodological problems. LEVEL OF EVIDENCE: N/A.