Subdural empyema (SDE) is a focal intracranial suppurative collection, usually in supratentorial subdural space. Etiologies include:181
- paranasal sinusitis (most common cause)
- postoperative neurosurgical infection
- posttraumatic complication
- middle ear or mastoid disease (10%)
- hematogenous spread (5%)
- meningitis (infrequent)
Streptococci are causative half the time, and Staphylococcus aureus in 10% of cases. Polymicrobial infection is frequent, including anaerobic organisms. Although loculation is common, infection can spread over the convexities and along the falx.
The most consistent clinical complaint is a progressively severe headache, often related to the sinusitis. Malaise, fever, and declining mental status can occur rapidly.
Complications can include dural venous thrombosis, parenchymal abscess, epidural abscess, and meningitis. Mass effect or secondary venous infarction can cause focal neurologic deficits.
Seizures are one of the most common presenting signs of SDE, occurring in up to 50% of patients.13 They are usually focal, relating to empyema site.
Diagnosis relies on clinical manifestations (especially the dyad of fever and focal seizures) and brain imaging, which usually reveals a crescent-shaped hypodensity along the dura or falx.181 Lumbar puncture is risky, secondary to mass effect of the SDE.
Antibiotics appropriate to the suspected etiology (similar to the treatment of epidural abscess) and prompt neurosurgical empyema evacuation are required.182 Seizure management is mandatory, especially given the frequent complication of increased intracranial pressure.13 Untreated patients can die within days. Even with treatment, the mortality rate remains as high as 40%.
Maintenance anticonvulsant therapy after successful empyema cure often is necessary because of the epileptogenic potential of residual scarring.
Adapted from: Goldstein MA and Harden CL. Infectious states. In: Ettinger AB and Devinsky O, eds. Managing epilepsy and co-existing disorders. Boston: Butterworth-Heinemann; 2002;83-133.
With permission from Elsevier (www.elsevier.com).