SUMMARY
Several types of intraspinal cyst develop within the spinal canal from the craniovertebral junction to the sacrum. These lesions occur in both children and adults. Arachnoid cysts are one of them and are more frequent in the paediatric population, being a relatively uncommon lesion in adults. The arachnoid cyst may be located intradurally or extradurally. The intradural type may be congenital or from spinal trauma, infection or spondylosis. Although intradural arachnoid cysts are often asymptomatic, they may give early symptoms when they exist with synchronous pathologies constricting the spinal canal gradually as in cervical spondylosis. In this report, a 60-year-old man with an arachnoid cyst of the cervicothoracic spine is presented. His cyst remained undiagnosed because of the nonspecific nature of the symptoms. It was only when he developed right hemiparesis that a posterior fluid collection compressing the spinal cord was found in Magnetic resonance imaginig. An intradural extramedullary cyst was removed with successful surgery and cord compression and symptoms were reversed. We discuss radiological diagnosis and surgical treatment of an arachnoid cyst in this report.