title: Surgical evaluation of magnetic resonance imaging findings in piriformis muscle syndrome.
abstract: OBJECTIVE
  The objective of this study was to evaluate the accuracy of magnetic resonance imaging (MRI) in the diagnosis of the piriformis muscle syndrome (PMS).
  
  
  METHODS
  In ten patients, seven female and three male, with a long history of clinical symptoms of the PMS, an MRI was performed as the last preoperative diagnostic tool. All patients were imaged using 2T MR system (Elscint, Haifa, Israel). Axial and coronal spin-echo, fast spin-echo (FSE), and fat-suppressed FSE-weighted images were made through the pelvic region with 3-mm section thickness and a 0.5-mm gap to show the whole piriformis muscle and the course of sciatic nerve on its way out of the pelvis. A routine examination also included axial fast spin-echo T2, three-dimensional gradient echo.
  
  
  RESULTS
  In seven cases, an MRI abnormality for the PMS was found. In two women, the MRI demonstrated a bigastric appearance of the piriformis muscle with a tendinous portion between the muscle heads and the course of the common peroneal nerve through the muscle between the tendinous portions of the muscle. In one female patient, the common peroneal nerve passed through the hypertrophied piriformis muscle. In four patients, the MRI showed a hypertrophied aspect of the piriformis muscle and an anteriorly displaced sciatic nerve. All MRI findings were confirmed surgically. In three patients, no apparent abnormalities could be observed, but after a surgical treatment, i.e., a tenotomy of the piriformis muscle and neurolysis of the sciatic nerve, all symptoms disappeared.
  
  
  CONCLUSIONS
  In piriformis muscle syndrome, MRI may demonstrate signal abnormalities of the sciatic nerve as well as its relationship with the normal and abnormal piriformis muscle.
authors.affiliation: Department of Radiology, Clinical Hospital Sestre Milosrdnice, Vinogradska 29, 10000, Zagreb, Croatia. marko.pecina@zg.t-com.hr
authors.forename: Hrvoje Ivan
authors.initials: HI
authors.lastname: Pecina
authors.forename: Igor
authors.initials: I
authors.lastname: Boric
authors.forename: Tomislav
authors.initials: T
authors.lastname: Smoljanovic
authors.forename: Davor
authors.initials: D
authors.lastname: Duvancic
authors.forename: Marko
authors.initials: M
authors.lastname: Pecina
mesh_terms: D000293:Adolescent; D000328:Adult; D002081:Buttocks / Q000473:pathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000002:abnormalities*; D009468:Neuromuscular Diseases / Q000175:diagnosis* / Q000601:surgery*; D020426:Sciatic Neuropathy / Q000209:etiology* / Q000473:pathology*; D013577:Syndrome