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


BACKGROUND
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.


CONCLUSIONS
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.


METHODS
N/A.
Department of Neurosurgery, University of California, San Francisco, San Francisco, CA.
W Bradford
WB
DeLong
The Mountain-Whisper-Light Statistics, Seattle, WA.
Nayak L
NL
Polissar
The Mountain-Whisper-Light Statistics, Seattle, WA.
Moni B
MB
Neradilek
Health Services Research and Policy, University of Rochester Medical Center Rochester, Rochester, NY.
Leslie A
LA
Laam
D002420:Cauda Equina / Q000601:surgery*; D019299:Decompression, Surgical / Q000379:methods; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000601:surgery*; D012189:Retrospective Studies; D016896:Treatment Outcome; D001743:Urinary Bladder / Q000503:physiopathology*; D001750:Urinary Bladder, Neurogenic / Q000503:physiopathology*; D016055:Urinary Retention / Q000601:surgery*