The objective of this work is to highlight and discuss a rare cause of curable spinal cord compression with a favourable evolution, through the case of a posterior thoracic epidural arachnoid cyst for which we will discuss its clinical, paraclinical, therapeutic and evolutionary characteristics, with review of the literature. The patient was a six and a half year old boy with no previous pathological history. He was admitted for progressive gait problems with myalgia. MRI showed an extradural cystic lesion in the thoracic spinal cord opposite D5-D10 with a signal similar to that of the CSF. A laminectomy followed by evacuation of the cyst with partial removal of the wall was performed. Pathological examination confirmed the diagnosis. The evolution was marked by a total disappearance of the initial clinical symptomatology in the patient. Although rare, the extradural arachnoid cyst is a potential cause of reversible spinal cord compression for which surgical resection is the treatment of choice.
