Piriformis pyomyositis, a cause of piriformis syndrome—a systematic search and review

Piriformis pyomyositis is a rare form of purulent skeletal myositis. As previous studies concerning piriformis pyomyositis had lower level of evidence and no systematic review has been published yet, we performed a systematic search to review and describe causes, symptoms, red flags, and available treatment options for piriformis pyomyositis. Using PubMed and PubMed Central databases, we found 21 articles describing 23 cases of piriformis pyomyositis. Based on the retrieved information, alongside acute sciatica like buttock and/or hip pain, high-grade fever, aggressive deep seated gluteal pain, neurological deficit of sciatic nerve distribution, positive straight leg raising test, and raised inflammatory biomarkers (erythrocyte sedimentation rate, ESR, C-reactive protein, CRP) provide clues for diagnosis of piriformis pyomyositis. Some cases were very ill but no death was documented. Staphylococcus aureus was the most common pathogen, but Group A as well as Group β Streptococcus, Salmonella typhi, Proteus mirabilis, Brucella melitensis, and Escherichia coli were also involved in the disorder. To treat the piriformis pyomyositis, broad-spectrum antibiotics were found to be useful; however, sometimes, antibiotic switching was warranted based on blood and tissue aspirate reports. Drainage and/or surgical exploration of the affected piriformis muscle were required in cases where antibiotics appeared ineffective. Piriformis pyomyositis is a rara avis and performing of prospective studies will hardly be feasible.