Piriformis syndrome: pain response outcomes following CT-guided injection and incremental value of botulinum toxin injection

Abstract

Purpose: Piriformis syndrome is a common pain condition affecting the buttock and posterior hip with or without radiation to the leg, and management of the condition involves many treatments. In this study, we hypothesize that a CT-guided injection with botulinum toxin is more effective in providing pain relief than a CT-guided injection without Botox.

Methods: Overall, 97 consecutive patients with piriformis syndrome presented for a CT-guided injection of the piriformis muscle and perineural injection of the sciatic nerve. After the injection, the patients received a visual analog scale pain log to record their pain level until the follow-up appointment. P values of less than 0.2 were considered as confounder and adjusted by inverse probability of treatment weighting (IPTW) via propensity score. The effect of botulinum toxin on 48-hour response and duration of response was tested using weighted chi-square test and weighted Kaplan-Meier analysis.

Results: There was a total of 97 patients in the study, and 111 injections, as some patients had bilateral injections. Patients in the Botox group had more 48-hour response than patients in the non-botulinum toxin group (P < 0.001 with IPTW, P = 0.005 without IPTW). Median pain-free survival was 30 days for Botox group and 1 day for non-Botox group (P = 0.059 with IPTW, P = 0.10 without IPTW).

Conclusion: CT-guided injections with botulinum toxin for patients with piriformis syndrome are more likely to lead to a positive response and a longer duration of response than patients who receive a CT-guided injection without botulinum toxin. We hope that this study facilitates future prospective randomized blind trials for patients with suspected piriformis syndrome.

Figure 1

Patient selection flowchart detailing inclusion and exclusion criteria.

Figure 2

Patient visual analog scale for CT-guided injection.

Figure 3

Proportion of patients having Botox injection for their first CT-guided injection before and after propensity score weighting (IPTW, inverse probability of treatment weighting; FABER, flexion, abduction, external rotation test; FADIR, flexion, adduction, internal rotation test).

Figure 4. a–e

A 57-year-old female presenting with buttock pain and back pain and diagnosed with left piriformis syndrome. She received an injection with Botox and had a positive response. Coronal 3D inversion recovery turbo spin-echo (IR TSE) image (a) shows asymmetrically hyperintense left sciatic nerve (thick arrow) at the sciatic notch compared to normal right sciatic nerve (thin arrow). Coronal maximum intensity projection (MIP) DTI image (b=600 s/mm²) (b) shows hyperintense left sciatic nerve. Axial T1-weighted image (c) shows left piriformis hypertrophy. CT-guided injection (d) with Botox and contrast of the left piriformis muscle. CT-guided injection (e) into the sciatic nerve (black arrow) showing the needle tip (thin white arrow), and the contrast (thick white arrow).

Figure 5. a–e

A 78-year-old female presenting with buttock pain and back pain and diagnosed with left piriformis syndrome. She received an injection without Botox and had a negative response. Coronal 3D IR TSE image (a) shows normal signal of the sciatic nerves. Coronal MIP DTI image (b=600 s/mm²) (b) shows no enhancement of the sciatic nerves. Axial T1-weighted image (c) shows left piriformis hypertrophy. CT-guided injection (d) without Botox of the left piriformis muscle. Post-injection image (e) of the sciatic nerve (black arrow) and medication mixture (white arrow).

Figure 6

Pain-free survival analysis comparing patients who received Botox to patients who did not receive Botox in the injection.