Genital Pain caused by Accessory Piriformis Successfully Treated with Piriformis Injection

Case Diagnosis: Neuropathic Genital Pain caused by Accessory Piriformis

Case Description or Program Description: A 40 year old male presented with two years of neuropathic left buttock pain radiating to the left perineum, scrotum and penis, triggered by sex, prolonged sitting, and hip flexion. The patient previously tried antibiotics for presumed prostatitis which were ineffective, and pelvic floor physical therapy which provided only minimal relief.

Setting: Hospital Based Outpatient Clinic

Assessment/Results: The patient was evaluated, and given the distribution of clinical symptoms, pudendal neuralgia was suspected. A fluoroscopic and neurostimulator guided pudendal nerve block with dexamethasone and bupivacaine 0.5% provided complete anesthetic phase relief, but no lasting benefit. A prior MRI pelvis demonstrated asymmetric left piriformis hypertrophy, with accessory bundles of the piriformis overlying the S2 nerve roots. An ultrasound guided piriformis injection was performed, which provided substantial, but incomplete benefit at 2 week follow up. A repeat piriformis injection was performed, with further benefit. After 3 months, symptoms began to recur, and an ultrasound guided botulinum toxin injection (50 units) was performed into the left piriformis. This completely resolved genital symptoms and substantially improved buttock pain. The patient reported no functional limitations at follow up and was able to resume sexual activity.

Discussion (relevance): While neural irritation from the piriformis is known to cause lumbosacral radicular pain, it rarely cause referred genital pain. An accessory piriformis muscle is an anatomic variation of the piriformis, which can lead to separate fibers contacting sacral nerve roots. In our case, we report a patient who had genital pain due to neural irritation of the lower sacral nerve roots or proximal pudendal nerve from an accessory piriformis.

Conclusions: Anatomic variations of the piriformis can be a source of piriformis syndrome. While piriformis syndrome typically causes pain traveling down the leg, it can cause genital pain in cases of anatomic variation.