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Intracranial Epidural Abscess and Subdural Empyema

by John E. Greenlee, MD

Epidural abscess is a collection of pus between the dura mater and skull. Subdural empyema is a collection of pus between the dura mater and the underlying arachnoid mater. Symptoms of epidural abscess include fever, headache, vomiting, and sometimes lethargy, focal neurologic deficits, seizures, and/or coma. Symptoms of subdural empyema include fever, vomiting, impaired consciousness, and rapid development of neurologic signs suggesting widespread involvement of one cerebral hemisphere. Diagnosis is by contrast-enhanced MRI or, if MRI is not available, contrast-enhanced CT. Treatment is with surgical drainage and antibiotics.

Etiology

Cranial epidural abscess and subdural empyema are usually complications of sinusitis (especially frontal, ethmoidal, or sphenoidal), but they can follow ear infections, cranial trauma or surgery, or, rarely, bacteremia. Pathogens are similar to those that cause brain abscess (see Brain Abscess : Etiology). In children < 5 yr, the usual cause is bacterial meningitis; because childhood meningitis is now uncommon, childhood subdural empyema is uncommon.

Complications

Epidural abscess may extend into the subdural space to cause subdural empyema. Both epidural abscess and subdural empyema may progress to meningitis, cortical venous thrombosis, or brain abscess. Subdural empyema can rapidly spread to involve an entire cerebral hemisphere.


Symptoms and Signs

Fever, headache, lethargy, focal neurologic deficits (often indicating subdural empyema when rapidly developing deficits suggest widespread involvement of one cerebral hemisphere), and seizures usually evolve over several days. Patients with intracranial epidural abscess may also develop a subperiosteal abscess and osteomyelitis of the frontal bone (Pott puffy tumor), and patients with subdural empyema develop meningeal signs. In epidural abscess and subdural empyema, vomiting and papilledema are common. Without treatment, coma and death occur rapidly.

Diagnosis

  • Contrast-enhanced MRI

Diagnosis is by contrast-enhanced MRI or, if MRI is not available, by contrast-enhanced CT. Blood and surgical specimens are cultured aerobically and anaerobically.

Lumbar puncture provides little useful information and may precipitate transtentorial herniation. If intracranial epidural abscess or subdural empyema is suspected (eg, based on symptom duration of several days, focal deficits, or risk factors) in patients with meningeal signs, lumbar puncture is contraindicated until neuroimaging excludes a mass lesion. In infants, a subdural tap may be diagnostic and may relieve pressure.

Treatment

  • Surgical drainage

  • Antibiotics

Emergency surgical drainage of the epidural abscess or subdural empyema and any underlying sinusitis should be done. Pending culture results, antibiotic coverage is the same as that for brain abscess except in young children, who may require antibiotics for any accompanying meningitis (see Table: Initial Antibiotics for Acute Bacterial Meningitis and Common IV Antibiotic Dosages for Acute Bacterial Meningitis*). Anticonvulsants and measures to reduce intracranial pressure may be needed.

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