Complementary Specific Pelvic Sequences on Routine Lumbar Magnetic Resonance Imaging Scans: An Imaging-Based Study Focused on Piriformis Syndrome.

To discuss the rationale and merit of specific pelvic sequences as an adjunct to routine lumbar magnetic resonance imaging (MRI) for early detection of piriformis syndrome (PS) and to disclose its frequency in patients who underwent radiological evaluation. This retrospective, imaging-based study included all individuals who underwent lumbar MRI and those who were further evaluated with a pelvic MRI, but excluded all high-energy trauma cases. The patients' demographics and radiological features were reviewed using electronic patient records and hospital-based picture image archiving and communication system. Overall, 1321 individuals (659 females; 662 males) underwent lumbar MRI during the study period, and of these, 485 (238 females; 247 males) were further analyzed with a pelvic MRI for differential diagnosis. Forty patients (8.2%) (23 females; 17 males) were diagnosed with PS-all confirmed with MR neurography (MRN). On re-evaluation of all lumbar and pelvic MRIs and MRNs, we realized that adding just three specific pelvic sequences to routine lumbar MRI scans were enough to accurately delineate the piriformis muscle pathologies and sciatic nerve intensities. The calculated frequencies of PS in females, males, and the whole study population within 57 months were 3.49%, 2.57%, and 3.03%, respectively. Although PS being a clinical diagnosis, this study indicated that in patients whom PS was not suspected at the initial examination, 8.2% of them were finally diagnosed after MRI evaluations. Performing specific pelvic sequences as an adjunct to routine lumbar MRI can salvage underdiagnosed patients with PS and facilitate early detection of this pathological condition.