The MRI appearances of an intradural spinal arachnoid cyst accompanying transverse myelitis

The usual magnetic resonance imaging (MRI) appearance of an intradural spinal arachnoid cyst is a slightly increased signal of the cyst with some interspersing signal voids on T2-weighted images. We report a case of an intradural spinal arachnoid cyst with an unusual MRI presentation resulting from the existence of transverse myelitis. This unusual MRI presentation was initially misinterpreted as a spinal hematoma. Therefore, recognizing the changeable signals inside an intradural spinal arachnoid cyst is crucial for a correct diagnosis and avoidance of unnecessary operations.