365 Sciatica of Non-Disc Origin

Abstract

INTRODUCTION: Sciatica resulting from piriformis muscle compression may respond to surgical decompression of the sciatic nerve via piriformis release. The topic has been very controversial. Pre-operative evaluation with MRI is useful to identify potential changes in either the piriformis muscle or the sciatic nerve that may help confirm the diagnosis of piriformis syndrome. METHODS: A retrospective analysis of all patients who underwent piriformis release to decompress the sciatic nerve. All surgeries were performed using a transgluteal approach. All patients (15) had preoperative localization of the piriformis muscle via percutaneous wire placement by interventional radiology using either CT or ultrasound guidance. 30 patients, who had MRI scans of their pelvis unrelated to sciatica, served as the control cohort. We also looked for signal changes in the sciatic nerve seen on MRI, piriformis muscle thickness, and pre versus post-operative numeric rating scale (NRS) assessment. RESULTS: Between treatment and control cohorts, there was no difference in basic demographics (other than age). In comparing the surgical and control cohorts, we found that a significant number of patients in the surgical cohort had the sciatic nerve riding over the ischial spine. Distance between the midpoint of the sciatic nerve to the ischial spine was also significantly lower in the surgical cohort. Piriformis thickness was essentially identical between the cohorts. In comparing pre and postoperative NRS pain scores, the aggregate of surgically treated patients had a significant improvement in their pain scores by approximately 4 points. Subgroup analysis of the surgical cohort demonstrated trends toward a larger improvement in NRS when the distance between the midpoint of the sciatic nerve to the ischial spine was <9mm, BMI <25, and piriformis thickness <2cm. CONCLUSION: Identifying clear MRI findings related to the sciatic nerve and its trajectory through the pelvis can potentially help identify patients who will better respond to surgery.