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Lower lumbar and sacral regions intraspinal extra-axial collection involving subdural space along the ventral and dorsal aspects, preserving epidural fat, and exerting a mass effect upon cauda equina roots. They elicit high signal on T1 and low signal on T2 (early subacute blood; intracellular methemoglobin). "Inverted Mercedes-Benz sign' could be noted on axial T1WI.