Enhanced lumbar nerve roots in the spine without prior surgery: radiculitis or radicular veins?

PURPOSE To evaluate the clinical significance of continuous intradural lumbosacral nerve root enhancement in symptomatic patients without prior lumbar surgery. METHODS Fifty-three patients without prior back surgery, referred to our institution for evaluation of low-back pain and radiculopathy, were studied with gadolinium-enhanced MR (0.1 mmol/kg) of the lumbar spine. Scans were reviewed for the presence of lumbosacral nerve root enhancement and any associated nerve root compression. Results were correlated with clinical history and physical examinations. RESULTS Seventeen continuously enhancing nerve roots and two enhancing fila terminale were observed in 13 patients. Eight of 17 (47%) had no referable symptoms. Nine of these nerve roots (53%) were not associated with any degree of nerve root compression. Seven cases (41%) were noted to have flow-related enhancement on the entry section of the T1-weighted axial sequence. CONCLUSIONS Lumbosacral nerve root enhancement correlates poorly with clinical radiculopathy. The use of contrast enhancement to detect lumbosacral nerve root enhancement in cases in which the unenhanced scan is less than diagnostic is not warranted. The high association between lumbosacral nerve root enhancement and entry-section flow-related enhancement suggests that these enhancing structures within the cauda equina are vessels. It is likely that lumbosacral nerve root enhancement represents intravascular enhancement of radicular veins and not a breakdown in the blood-nerve barrier.