MRI Findings of a Rare Case of Gradual Spinal Cord Compression Caused by a Thoracic Spinal Arachnoid Cyst

Introduction: Extradural spinal arachnoid cyst is a rare, male-dominated condition. It is usually asymptomatic, and spinal cord compression is rarely described. MRI (magnetic resonance imaging) is the gold standard for diagnosis and neurosurgical treatment. We report a case in order to study the contribution of MRI in the diagnosis. Observation: Mrs. DB, 65 years old, with no medical or surgical history, was referred by the neurosurgery department for progressive paraplegia for 02 years. The MRI made for the circumstance revealed an intraductal, extradural and extramedullary cystic lesion, at the posterior thoracic level, extending from Th6 to Th8, well circumscribed, without a wall of its own. It is in French hyposignal T1, hyper signal T2 and unrestricted diffusion in ADC. It severely compresses the spinal cord in front. No signal abnormality of the spinal cord is in the regard. It is not modified after the injection of the gadolinite contrast medium. No stigma of intra-lesional bleeding is in T2*. It was associated with a protrusive degenerative lumbo-discarthrosis stepped from L2-L3 to L5-S1 leading to a disco-radicular impingement. She was operated on by the neurosurgery team and the post-operative effects were simple. There is a clear regression in his lower limb deficit after two months. Conclusion: Compressive arachnoid cyst is rare and chest topography is the most common. MRI is the reference examination for diagnosis. The treatment is surgical and has a good prognosis.