Use of botulinum neurotoxin in the treatment of piriformis syndrome: A systematic review.

Objective: To determine the pain, functional and adverse outcomes of patients with piriformis syndrome who received botulinum neurotoxin injection, and to determine the optimal dosing of botulinum neurotoxin and choices of modality used during this intervention.

Literature survey: Systematic review of relevant clinical studies published in English language using PubMed/Medline, Embase and CINAHL databases from October 1, 2002 to October 6, 2020.

Methodology: A comprehensive search was performed to identify all studies addressing the treatment of piriformis syndrome with botulinum toxin. Two reviewers independently screened the titles, abstracts, and full texts and extracted data based on a set of predefined inclusion and exclusion criteria. 23 full-text articles were identified of which consensus was achieved for seven articles for data extraction and quality assessment. The qualities and risk of potential bias of the seven studies were appraised using the National Heart, Lung and Blood Institute (NIH) Study Quality Assessment tools for case controls, cohort studies and randomized trials.

Synthesis: Seven studies (n = 152 patients) were included consisting of three randomized controlled studies (RCTs), two case control studies and two cohort studies. The qualities of these studies were: Two good and one fair for the RCTs, fair for both the case controls and one good and fair for the cohort studies. Most studies reported some reduction in pain using various modalities to guide injection (CT, EMG, US or fluoroscopy). However, the included studies were heterogeneous, making it difficult to quantify pain reduction. There was minimal description of other functional outcomes. Botulinum toxin A doses range from 100 to 300U. Mild adverse effects were reported with no medical intervention needed.

Conclusions: There is fair quality of evidence to suggest botulinum toxin is safe to reduce pain in piriformis syndrome. There is insufficient data to quantify pain reduction and to describe other functional outcomes. The optimal dose of botulinum toxin A remains unclear. Modalities to guide botulinum injection into the piriformis muscle remain heterogeneous.