Sciatica of nondisc origin and piriformis syndrome: diagnosis by magnetic resonance neurography and interventional magnetic resonance imaging with outcome study of resulting treatment.
OBJECTIVE
Because lumbar magnetic resonance (MR) imaging fails to identify a treatable cause of chronic sciatica in nearly 1 million patients annually, the authors conducted MR neurography and interventional MR imaging in 239 consecutive patients with sciatica in whom standard diagnosis and treatment failed to effect improvement.


METHODS
After performing MR neurography and interventional MR imaging, the final rediagnoses included the following: piriformis syndrome (67.8%), distal foraminal nerve root entrapment (6%), ischial tunnel syndrome (4.7%), discogenic pain with referred leg pain (3.4%), pudendal nerve entrapment with referred pain (3%), distal sciatic entrapment (2.1%), sciatic tumor (1.7%), lumbosacral plexus entrapment (1.3%), unappreciated lateral disc herniation (1.3%), nerve root injury due to spinal surgery (1.3%), inadequate spinal nerve root decompression (0.8%), lumbar stenosis (0.8%), sacroiliac joint inflammation (0.8%), lumbosacral plexus tumor (0.4%), sacral fracture (0.4%), and no diagnosis (4.2%). Open MR-guided Marcaine injection into the piriformis muscle produced the following results: no response (15.7%), relief of greater than 8 months (14.9%), relief lasting 2 to 4 months with continuing relief after second injection (7.5%), relief for 2 to 4 months with subsequent recurrence (36.6%), and relief for 1 to 14 days with full recurrence (25.4%). Piriformis surgery (62 operations; 3-cm incision, transgluteal approach, 55% outpatient; 40% with local or epidural anesthesia) resulted in excellent outcome in 58.5%, good outcome in 22.6%, limited benefit in 13.2%, no benefit in 3.8%, and worsened symptoms in 1.9%.


CONCLUSIONS
This Class A quality evaluation of MR neurography's diagnostic efficacy revealed that piriformis muscle asymmetry and sciatic nerve hyperintensity at the sciatic notch exhibited a 93% specificity and 64% sensitivity in distinguishing patients with piriformis syndrome from those without who had similar symptoms (p < 0.01). Evaluation of the nerve beyond the proximal foramen provided eight additional diagnostic categories affecting 96% of these patients. More than 80% of the population good or excellent functional outcome was achieved.
Filler
Aaron G
AG
Institute for Spinal Disorders, Cedars Sinai Medical Center, Los Angeles, California, USA. afiller@nervemed.com
Haynes
Jodean
J
Jordan
Sheldon E
SE
Prager
Joshua
J
Villablanca
J Pablo
JP
Farahani
Keyvan
K
McBride
Duncan Q
DQ
Tsuruda
Jay S
JS
Morisoli
Brannon
B
Batzdorf
Ulrich
U
Johnson
J Patrick
JP
D000328:Adult; D000368:Aged; D001415:Back; D002045:Bupivacaine / Q000008:administration & dosage*; D003937:Diagnosis, Differential; D005500:Follow-Up Studies; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D007405:Intervertebral Disc Displacement / Q000175:diagnosis*; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000187:drug effects*; D009408:Nerve Compression Syndromes / Q000601:surgery; D009460:Neurologic Examination; D009485:Neuroradiography; D010043:Outcome and Process Assessment, Health Care; D010147:Pain Measurement; D012008:Recurrence; D012585:Sciatica / Q000175:diagnosis* / Q000209:etiology / Q000601:surgery*; D012680:Sensitivity and Specificity; D013126:Spinal Nerve Roots / Q000187:drug effects / Q000601:surgery; D025321:Surgery, Computer-Assisted; D013531:Surgicenters; D013577:Syndrome
D002045:Bupivacaine