The Piriformis Syndrome. A sciatic nerve entrapment misdiagnosed as lumbar radiculopathy. A case report and literature review

The term Piriformis Syndrome describes an extrapelvic pressure of the whole or part of the Sciatic Nerve, at the level of the Piriformis muscle caused by various conditions and characterized Clinically by symptoms of sciatica. As early as 1928 Yeoman described extra pelvic entrapment of the sciatic nerve by the piriformis muscle as a cause of sciatica. After Mixter and Barr in 1934 described nerve root compression by disc prolapse as a cause of sciatica, this diagnosis dominated the Clinical thinking for nearly three decades and what had been previously described was nearly forgotten. The development of imaging techniques revealed other intraspinal compressing elements. On the other hand, cases of negative root exploration for Sciatica focused attention to extrapelvic sciatic nerve pathology. This report concerns the case of a patient, who after a negative root exploration for severe sciatica proved to have an extrapelvic cause for this problem at the level of the piriformis muscle due mainly to anatomic variation of the sciatic nerve in relation to the piriformis muscle.