<p>Sciatica is most frequently attributed to lumbar nerve root compression; however, a frequently underrecognized subset of patients presents with radicular-type symptoms arising from pathology involving the sciatic nerve beyond the spinal canal. In such cases, lumbar imaging may be normal or demonstrate incidental degenerative findings that do not account for symptom distribution, leading to diagnostic delay or inappropriate intervention. With the expanding role of high-resolution MRI and MR neurography in peripheral nerve imaging, especially in dedicated evaluation of the sciatic nerve, accurate assessment of extraspinal sciatic neuropathy has emerged as an essential component of contemporary diagnostic neuroradiology. This review provides an anatomically guided, compartment-based framework for MR-based evaluation of the sciatic nerve from the lumbosacral plexus through the deep gluteal region and posterior thigh. Imaging protocols, normal MR appearance, and key technical considerations are outlined, followed by a systematic discussion of mechanical entrapment syndromes, traumatic and postoperative neuropathies, inflammatory and infectious conditions, vascular abnormalities, and neoplastic processes. Emphasis is placed on precise neuroanatomical localization and mechanistic characterization of sciatic nerve involvement. A structured neuroradiologic approach improves diagnostic precision, refines pathophysiologic interpretation, and facilitates targeted multidisciplinary management in patients with persistent radicular symptoms and inconclusive lumbar imaging.</p>