First described in 1937, piriformis syndrome is caused by abnormal piriformis bundles compressing the sciatic nerve, leading to pain in the buttocks, hips, and/or lower limbs. We present a video of a case of a right-sided intrapelvic entrapment of sacral nerve roots by the piriformis and review our initial results.

A 36 year-old man was seen with a 8-month history of moderate sciatica, describing aching pain in the gluteal region and sharp pain in the lower limbs. Hip abduction aggravated the pain, while ambulating alleviated his symptoms. He denied erectile dysfunction.
Associated urinary symptoms were frequency, urgency, and urge incontinence. Regular medications included pregabalin 75 mg BID and dipyrone 1 g Q6h. Past medical history included dyslipidemia. Examination revealed allodynia in the proximal scrotum, along the S2 dermatome. Urodynamic investigations suggested urinary incontinence due to detrusor overactivity. Magnetic resonance imaging showed an anomalous piriformis bundle compressing L5 to S2 nerves.

Laparoscopy was performed under general anesthesia. After developing the pre-sacral space, an anomalous piriformis muscle bundle compressing the S2 and S3 nerve roots was observed. The muscle fibres were divided, and the right sacral nerve roots then revealed. The previously divided muscle fibres were then mobilized to retract into the deep gluteal space.  
Post-operatively, the patient reported full resolution of his urinary and motor symptoms. However, generalized sciatica occurred at 6 weeks post-operatively due to the retraction of the distal portion of the transected piriformis muscle into the deep gluteal space, which fibrosed and adhered to the sciatic nerve at that level. A second operation was ultimately required, utilizing a transgluteal approach to detrap the sciatic nerve. 
Three additional patients underwent a similar operation. Of four patients, the average age was 42.5 ± 11.7 (36 – 60) years, and three (75%) were female. The average time from symptom onset to diagnosis was 6.2 ± 6.2 (0.7 – 15) years, and patients had undergone 1.8 ± 2.1 (0 – 4) surgeries. Prior to our surgery, the VAS score was 9.3 ± 1.0 (8 – 10); however, post-operatively, this decreased to 2.0 ± 1.8 (0 – 4). The average surgical time was 119 ± 39.5 (66 – 161) minutes. None of the other three patients experienced recurrent symptoms or required a second transgluteal approach.

Intrapelvic entrapment of sacral nerve roots by abnormal piriformis muscle bundles is a possible extra-spinal cause of sciatica and neurogenic pelvic floor dysfunction that can be treated successfully by laparoscopy.