Lumbar intraspinal arachnoid cyst superimposed by hyperacute spinal subdural hematoma: an unusual case

Background contextLumbar intradural arachnoid cyst (AC) concomitant with hyperacute spinal subdural hematoma (SSDH) has never been reported in the literature.PurposeTo report a case of lumbar AC superimposed by hyperacute SSDH, which was difficult to diagnose preoperatively using magnetic resonance imaging. Herein, we describe diagrams showing the proposed mechanisms underlying the formation of a symptomatic AC.Study design/settingThe study was designed to be a case report and literature review.MethodsA 65-year-old man presented with acute onset of low back pain, followed by 5-day history of numbness and weakness in both legs before admission. Magnetic resonance imaging of the lumbosacral spine revealed an intradural extramedullary biconvex lesion at the L3–L4 level; the lesion compressed the cauda equina posteriorly. The lesion mainly appeared as hyperintense on T2-weighted images and hypointense on T1-weighted images. On the basis of these findings, the lesion was preoperatively diagnosed as a symptomatic lumbar subdural AC that compressed the cauda equina.ResultsThe patient underwent laminectomy from L2 to L4. After a dura incision, a partially organized subdural hematoma was noted. Beneath the subdural hematoma was an AC compressing the underlying nerve roots. The patient’s back pain and muscle strength markedly improved after the operation.ConclusionsPreoperative diagnosis of concomitant hyperacute SSDH and AC is difficult. In cases of patients who present with intraspinal AC accompanied by an acute onset of clinical presentation, an associated etiology should be considered until proven otherwise.