Arachnoiditis ossificans is a uncommon disorder, is generally associated with neurologic deficits, but patients could be only mild sintomatic, regardless of the degree of ossification. Unenhanced CT has been well show to be sensitive for the disorder, useful to evaluate the full extenstion of the ossified mass and their remotion if surgical intervention is needed. On MRI imaging the manifestations could be minimal and variable, being important to access another pathologic conditions (arachnoid cysts, intramedullary cysts and syringomyelia).