Posttraumatic subdural hygroma: CT findings and differential diagnosis.

Subdural hygroma is a cerebrospinal fluid accumulation in the subdural space. It is an epiphenomenon of head injury. CT is the preferred diagnostic imaging modality. Differential diagnosis has to be made with chronic subdural hematoma, and atrophy with enlargement of the subarachnoid space. As time goes by, subdural hygroma either resolves, or it becomes a chronic subdural hematoma. Neurosurgical evacuation is only required when mass effect creates neurologic symptoms.