Sciatica of nondisc origin and piriformis syndrome: diagnosis by magnetic resonance neurography and interventional magnetic resonance imaging with outcome study of resulting treatment

Abstract

<jats:p content-type="fine-print"><jats:italic>Object.</jats:italic> 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.</jats:p> <jats:p content-type="fine-print"><jats:italic>Methods.</jats:italic> 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%).</jats:p> <jats:p content-type="fine-print">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%.</jats:p> <jats:p content-type="fine-print"><jats:italic>Conclusions.</jats:italic> 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 &lt; 0.01).</jats:p> <jats:p content-type="fine-print">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.</jats:p>

Brief review: Piriformis syndrome: etiology, diagnosis, and management

“…• Gluteal trauma in the sacroiliac or gluteal areas (possibly several years previously) 13,22,33 • Predisposing anatomic variants 4,5,7,14,15,40,41 • Myofascial trigger points 7,20,38,39,42 • Hypertrophy and spasm of the piriformis muscle 14,18,[43][44][45] • Secondary to laminectomy 13,38,39,43,[46][47][48][49][50] • Abscess, 51 hematoma, 52,53 myositis, 54 bursitis of the piriformis muscle, 55 neoplasms in the area of the infrapiriform foramen, 56 colorectal carcinoma, 57 neurinoma of the sciatic nerve, 18 episacroiliac lipoma 50 • Intragluteal injection 58 • Femoral nailing 18 • Myositis ossificans of the piriformis muscle 3,59 • Klippel-Trénaunay syndrome 18 Table 2 Differential diagnosis of piriformis syndrome…”

Magic Angle Effect: A Relevant Artifact in MR Neurography at 3T?

“…7,8 The MA is associated with a hyperintense T2 signal-intensity alteration in tissues densely composed of collagen, was first observed in tendons and ligaments, and was later reported also to occur in peripheral nerves. [9][10][11][12] It is conceived as a T2 signal-intensity increase related to the suppression of dipole-dipole interactions of the hydrogen protons bound to quasicrystalline structures such as tropocollagen, the triple-helical main compound of various types of fibrillary collagen.…”

Role of Skeletal Muscle MRI inPeripheral Nerve Disorders

“…Filler and colleagues demonstrated that unilateral T2 high intensity of the sciatic nerve at the sciatic notch and asymmetry of the piriformis muscle on the MRI are the findings specific to piriformis syndrome (Filler et al, 2005). No abnormalities of the sciaticinnervated muscles are seen on the MRI.…”