Three-dimensional phase-contrast magnetic resonance imaging for the detention of a small communicating defect in a patient with a spinal extradural arachnoid cyst: illustrative case.

BACKGROUND:Spinal extradural arachnoid cysts are thought to be pouches that communicate with the intraspinal subarachnoid space through a dural defect. The treatment for these cysts is resection of the cyst wall followed by obliteration of the communicating defect, which is often elusive. OBSERVATIONS:The authors report the case of a 22-year-old man with an extradural arachnoid cyst with claudication and progressive motor weakness. Regular magnetic resonance imaging (MRI) and computed tomography did not reveal the location of the defect in the cyst. However, three-dimensional (3D) phase-contrast MRI clearly indicated the location of the defect and the flow of cerebrospinal fluid into the cyst. These findings allowed the authors to perform the least invasive surgery; the patient recovered motor function and could walk more smoothly. LESSONS:3D phase-contrast MRI can reveal a subtle dural defect in patients with spinal extradural arachnoid cysts.