Sciatic perineural edema treated by Botulinum toxin injection on piriformis muscle

Abstract

An 80-year-old woman presented with right leg and buttock pain since a few months' duration. Paresthesias on the right leg were associated with a prolonged seated position. The right leg visual analog scale score was 6/10. The right side straight leg raise test (Lasègue test) was painless. Magnetic resonance imaging revealed mild bilateral L3–L4 and L4–L5 foraminal stenosis (Fig. 1). Transforaminal steroid injections over right L3–L4 and L4–L5 were performed but the leg and buttock pain did not improve at all. A pelvic magnetic resonance imaging revealed perineural edema of the right sciatic nerve at the level below the right piriformis muscle (Figs. 2 and 3), compatible with piriformis muscle syndrome [ [1] Michel F. Decavel P. Toussirot E. Tatu L. Aleton E. Monnier G. et al. The piriformis muscle syndrome: an exploration of anatomical context, pathophysiological hypotheses and diagnostic criteria. Ann Phys Rehabil Med. 2013; 56: 300-311 Crossref PubMed Scopus (36) Google Scholar ]. Under computed tomography-guidance, 100 IU Botulinum toxin was injected into the right piriformis muscle belly under local anesthesia (Fig. 4, Left and Middle) [ [2] Al-Al-Shaikh M. Michel F. Parratte B. Kastler B. Vidal C. Aubry S. An MRI evaluation of changes in piriformis muscle morphology induced by botulinum toxin injections in the treatment of piriformis syndrome. Diagn Interv Imaging. 2015; 96: 37-43 Crossref PubMed Scopus (33) Google Scholar ]. A repeat Botulinum toxin injection was given 3 months later to boost the muscle atrophy effect. Follow-up pelvic computed tomography demonstrated right piriformis muscle atrophy (Fig. 4, Right). After the second injection, the right leg visual analog scale score improved to 1/10. Fig. 2Sacral T1-weighted coronal magnetic resonance imaging shows right sciatic perineural edema (arrow) when comparing with the left side. View Large Image Figure Viewer Download Hi-res image Fig. 3Serial sacral T1-weighted axial magnetic resonance imaging shows right sciatic perineural edema (arrow) just below the piriformis muscle (asterisk). View Large Image Figure Viewer Download Hi-res image Fig. 4(Left) Before the computed tomography (CT)-guided Botulinum toxin injection, axial imaging shows symmetrical piriformis muscle thickness. (Middle) CT-guided Botulinum toxin was injected over the piriformis muscle belly under local anesthesia. (Right) Follow-up CT imaging revealed right piriformis muscle atrophy (arrow). View Large Image Figure Viewer Download Hi-res image