Post traumatic spinal arachnoid cysts.

Based on the study of 10 cases of post traumatic spinal arachnoid cysts (SAC), acute and chronic clinical variants are individualized. A physiopathological hypothesis is advanced to explain their mechanism of formation. Acute SACs should be operated upon immediately although the differential diagnosis with spinal epidural haematomas is difficult. Even more difficult is the diagnosis of the chronic SAC. Rare though it may be, the Neurosurgeon must be aware of the possibility of its occurrence, especially when treating rather vague and stubborn cases.