This clinical case of intramedullary arachnoid cyst is the second reported case in Senegal. It concerns a 50-yearold woman, with no particular history, admitted for back pain associated with intermittent spinal claudication. The physical examination showed a dorsal spinal syndrome, spastic paraparesis, hypoesthesis under T9 sensitive territory with bilateral Babinski sign. Cutaneous-abdominal reflexes were abolished at T8. Magnetic resonance imaging (MRI) revealed an intramedullary cyst formation. The patient was operated on the day after her admission by a posterior approach with scopic tracking. She underwent a laminectomy from T7 to T9. Thereafter the cyst has been removed, then discharged three days after the surgery. The clinical follow-up showed a full recovery.