2007 Award Winners

E-Poster #5
Louis A. Goldstein Award Nominee

Prospective Study of Post-Operative Lumbar Epidural Hematoma: Does Size Really Matter?

Mark J. Sokolowski, MD; Timothy A. Garvey, MD; John Perl, MD; Amir A. Mehbod, MD; Burak Akesen, MD; Margaret S. Sokolowski, PhD; Ensor E. Transfeldt, MD  

Introduction: Epidural hematomas are common after lumbar surgery. Most are asymptomatic. Among symptomatic patients, a classic progression from sharp peri-incisional pain to bilateral neurologic deficits has been described. No prior study has correlated MRI hematoma features with postoperative symptoms. We propose and evaluate a new measurement (the critical ratio) to assess the extent of compression by hematoma and the potential for symptom development.

Methods: The study population consisted of 3 patient groups who underwent MRI evaluation within 3-5 days of lumbar decompression with or without fusion. Fifty consecutive patients on whom MRI data was prospectively collected comprised the “asymptomatic” group. No patient developed severe post-operative pain or neurologic deficit. Eleven additional patients who had developed immediate post-operative symptoms within the last 24 months were identified within our institutional database. The “painful” group included 6 patients with severe peri-incisional pain without neurologic deficit. The “cauda equina” group included 5 patients with post-operative cauda equina syndrome. Thecal sac cross sectional area (CSA) was measured on pre- and postoperative MRI at each level. For each patient, digital imaging software was used to calculate: critical ratio, hematoma volume, and volume per level decompressed. The critical ratio was defined as the smallest ratio of postoperative to preoperative CSA at any level within the lumbar spine.

Results: Mean critical ratios were: asymptomatic (0.73), painful (0.48), cauda equina (0.22).  Statistical significance (p<.025) was achieved between all populations for the critical ratio calculation. Neither mean hematoma volume nor volume per level decompressed differed significantly between the studied patient groups.

Conclusion: The critical ratio correlates more closely with the presence or absence of postoperative symptoms than hematoma volume, and is consistent with the clinical expectation that greater thecal compression is likely to result in more severe symptoms.

Significance: Few guidelines exist for MRI interpretation in the post-operative lumbar surgery patient. The critical ratio correlates well with symptoms due to hematoma.

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