subdural abscess

Last reviewed 01/2018

This is a collection of pus in the subdural space. It is about one-fifth as common as cerebral abscess. It rarely affects the underlying arachnoid and subarachnoid space but may compress the brain and produce mass effects.

Most commonly, it follows infection of the skull bones or air sinuses. Streptococcus is the most likely infective organism but other bacteria - such as Staphylococci and gram negatives - and occasionally, fungi, may be involved.

Presentation is usually with fever, followed by lethargy, reduced level of consciousness, and focal neurological signs, usually with neck stiffness. Seizures occur in 70% of cases, as a result of cortical involvement.

Diagnosis may be difficult, even with high resolution CT.

Treatment is as for brain abscesses. Resolution usually occurs from the dural side, and when complete, may leave a thickened dura as the only sequelae.

Untreated, the patient is at risk of thrombophlebitis in the cerebral veins that cross the subdural space to the dural venous sinuses. This may result in venous occlusion and subsequent venous infarction.