[MR imaging of a spinal arachnoid cyst: report of two cases]

Two cases of spinal arachnoid cyst were examined by MR imaging at 1, 5 T (Signa; General Electric). In both cases, a large cystic mass was demonstrated in the thoraco-lumbar region. On a T2-weighted mid-sagittal image, a hypointense septum between the cystic mass and the subarachnoid space was identified in both cases. At surgery, an extradural arachnoid cyst was found in case 2. But, case 1 had an intradural one.