Intracranial Epidural Abscess and Subdural Empyema
(See also Overview of Brain Infections.)
An intracranial epidural abscess is a pocket of pus that develops between the skull and the top layer of tissues (dura mater) covering the brain. A subdural empyema is a pocket of pus that develops between the dura mater and the middle layer of the tissues (arachnoid mater) covering the brain.
Intracranial epidural abscesses and subdural empyemas develop outside the brain itself but within the skull (intracranial):
Tissues Covering the Brain
Within the skull, the brain is covered by three layers of tissue called the meninges:
An intracranial epidural abscess develops between the dura mater and the skull. A subdural empyema develops between the arachnoid mater and the dura mater.
Epidural abscesses and subdural empyemas may result from
The same kinds of bacteria that cause brain abscesses (such as Staphylococcus aureus and Bacteroides fragilis) can cause epidural abscesses and subdural empyemas.
In children younger than 5 years, the cause is usually bacterial meningitis. Because meningitis is now uncommon in children, epidural abscesses and subdural empyemas are also uncommon in children.
Like a brain abscess, an epidural abscess or a subdural empyema can cause headache, sleepiness, vomiting, seizures, a stiff neck, and other signs of brain dysfunction.
The symptoms can evolve over several days. Meningitis or a brain abscess may develop. Or a blood clot may form in the large veins (venous sinuses) that carry blood from the brain.
Without treatment, symptoms progress rapidly, leading to coma and death.
To diagnose an epidural abscess or a subdural empyema, doctors use magnetic resonance imaging (MRI) done after gadolinium is injected intravenously. Gadolinium (an MRI contrast agent) makes abscesses and empyemas easier to see on MRI scans. If MRI is not available, computed tomography (CT) is done after a radiopaque contrast agent (which makes abscesses and empyemas easier to see on CT scans) is injected.
A spinal tap (lumbar puncture) is of little help and may be dangerous. If a large abscess, empyema, or other mass is present in the skull, removing spinal fluid during a spinal tap can cause the brain to shift down and be forced through a small natural opening in the tissue that divides the brain into compartments (called brain herniation). The resulting damage can be fatal.
In infants, a needle can sometimes be inserted directly into the abscess or empyema through a fontanelle (a soft spot between the skull bones) to drain the pus, relieve pressure, and help doctors make the diagnosis.
Epidural abscesses and subdural empyemas must be drained surgically. If the infection occurred because of an abnormality in the sinuses or middle ear, the surgeon may need to repair the abnormality at the same time.
Antibiotics (such as cefotaxime or ceftriaxone, metronidazole, and vancomycin) are given intravenously.
Anticonvulsants to control seizures and measures to reduce pressure within the skull may be needed. These measures include the following:
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