Intracranial 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.
(See also Introduction to Brain Infections.)
Etiology
Cranial epidural abscess and subdural empyema are usually complications of sinusitis (especially frontal, ethmoidal, or sphenoidal) or otitis media, but they can follow other ear infections, cranial trauma or surgery, or, rarely, bacteremia. Pathogens are similar to those that cause brain abscess (eg, Staphylococcus aureus, Bacteroides fragilis).
In children < 5 years old, 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 often develop meningeal signs. In epidural abscess and subdural empyema, vomiting is common. Many patients may develop papilledema.
Without treatment, coma and death occur rapidly, particularly in subdural empyema.
Diagnosis
Contrast-enhanced MRI
Diagnosis of epidural abscess or subdural empyema 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 brain 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 fluid in the sinuses should be done.
Pending culture results, antibiotic coverage is the same as antibiotics used to treat brain abscessInitial Antibiotics for Acute Bacterial Meningitis and Common IV Antibiotic Dosages for Acute Bacterial Meningitis).
Key Points
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.
Fever, headache, lethargy, focal neurologic deficits, and seizures usually evolve over several days; vomiting and papilledema are common.
Without treatment, coma and death occur rapidly.
Use contrast-enhanced MRI or, if MRI is not available, contrast-enhanced CT to diagnose epidural abscess or subdural empyema.
Lumbar puncture provides little useful information and may precipitate transtentorial herniation.
