[An intradural arachnoid cyst of the craniovertebral junction; a case report].

An intradural arachnoid cyst of the craniovertebral junction possibly of traumatic origin is reported. A 59-year-old man was admitted to our hospital with a 10-month history of progressive gait disturbance. He had a history of head injury with a fracture of the occipital bone. Myelography revealed pooling of the contrast medium in the posterior fossa and on the dorsal sides of C1 and C2. Metrizamide-enhanced computed tomography also showed pooling at the same level. Magnetic resonance imaging indicated a large cystic lesion at the craniovertebral junction. Craniectomy of the posterior fossa and laminectomy of C1, C2 and C3 were performed, and an intradural cyst with thickened dura and arachnoid was found. The cyst wall was opened to communicate with the subarachnoid space. Histological findings of the specimen showed that the arachnoid was thickened. There are over 130 reports of intradural arachnoid cyst of the spine, but those of traumatic origin are rare, and cysts located in the intracranial to spinal region are extremely rare.