 Acute subdural hygromas can be a potential neurosurgical emergency, requiring decompression.Acute hygromas are typically a result of head trauma—they are a relatively common posttraumatic lesion—but can also develop following neurosurgical procedures, and have also been associated with a variety of conditions, including dehydration in the elderly, lymphoma and connective tissue diseases.In the majority of cases, if there has not been any acute trauma or severe neurologic symptoms, a small subdural hygroma on the head CT scan will be an incidental finding.