Subdural hygroma
（重定向自Hydroma）
A subdural hygroma is a subdural body of cerebrospinal fluid (CSF), without blood. Most subdural hygromas are believed to be derived from chronic subdural hematomas. It is commonly seen in elderly patients after minor trauma but can be seen in children after an infection. One of the common causes of subdural hygroma is a sudden decrease in pressure by ventricular shunting. This can lead to leakage of CSF into the subdural space especially in cases with moderate to severe brain atrophy. In these cases the symptoms such as mild fever, headache, drowsiness and confusion can be seen, which are relieved by draining this subdural fluid.