subdural effusion
subdural hygroma

A CT scan performed in May 1991 shows a shrunken brain surrounded by chronic subdural effusions.

Subdural effusion refers to an effusion in the subdural space, usually of cerebrospinal fluid.

There are few exceptions to this rule: Haemophilus influenzae meningitis is often associated with subdural effusions that are mistaken for subdural empyemas.

A CT scan after the operation revealed bilateral subdural hygroma.

One of the common causes of subdural hygroma is a sudden decrease in pressure by ventricular shunting.

A subdural hygroma is a subdural body of cerebrospinal fluid (CSF), without blood.

Magnetic resonance imaging (MRI) should be done to differentiate a chronic SDH from a subdural hygroma, when clinically warranted.

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.

McCluney KW, Yeakley JW, Fenstermacher MJ, et al. "Subdural hygroma versus atrophy on MR brain scans: "the cortical vein sign"".

A tear between the dura and the arachnoid membranes, called a CSF fistula, can cause CSF to leak out of the subarachnoid space into the subdural space; this is called a subdural hygroma.