Subdural Empyema

What Is It?

Subdural empyema is an infection in the subdural space, the space between the dura mater and arachnoid membrane around the brain, caused by bacteria. The infection causes a fluid-filled mass in the subdural space as it enlarges, filled with purulent material (puss). Another name for an infected mass filled with purulent material is an abscess.

There are many types of bacteria that can cause infection in this area, including various streptococci, staphylococci, pseudomonas, bacteroides, enterobacter, klebsiella, H. influenzae, and E. coli. In young children, these infections can occur as a complication of meningitis. In older children and adults, spontaneous subdural empyema can occur from extension from a nearby infection of the paranasal sinuses, middle ear and mastoid sinuses. Therefore, while rare, bacterial infection in these areas (sinusitis, otitis media and mastoiditis) is a risk factor for this infection around the brain. Some patients may have a history of recent pulmonary infection (pneumonia) or brain abscess. Finally, subdural abscess can occur following brain surgery or penetrating head trauma if bacteria are introduced into the area.

Subdural empyema can also occur in the spine.

What Types of Symptoms Are Typical?

In addition to being an infection, the empyema acts like a mass, enlarging as it worsens. This can both put pressure on the adjacent brain and lead to inflammation of the underlying brain. Typical symptoms that are possible include fever and headache initially. Patients will usually have a recent history of sinusitis, otitis media (ear infection), mastoiditis, meningitis, brain surgery or penetrating head trauma. As the infection progresses and causes pressure and inflammation in the adjacent brain, neurological symptoms can occur including seizures, mental status changes (confusion, stupor or coma), weakness or paralysis, nausea and vomiting, visual problems or other neurological dysfunction.

On physical examination patients may also exhibit signs of meningeal irritation (stiff neck, photophobia), evidence of sinus infection or recent surgery/trauma, or cranial nerve deficits.

How Is The Diagnosis Typically Made?

Patients who present with symptoms consistent with subdural empyema generally receive a complete neurological evaluation. CBC blood count may show an increase in white blood cells and ESR may be elevated, consistent with infection. Blood is often cultured for bacteria. Most importantly, imaging of the brain including either MRI and/or CT with contrast can help to identify the fluid-filled mass lesion in the subdural space and associated swelling. Ultimately, open surgical sampling of the purulent material can allow the causative bacteria to be cultured and identified.

In some cases, a lumbar puncture (spinal tap) may be performed to assess the cerebrospinal fluid and evaluate for the presence of meningitis.

What Are Some Common Treatments?

Subdural empyema is a medical emergency as it can rapidly progress to cause significant neurological impairment and even death. Antibiotic treatment, by intravenous adminstration, is generally started immediately. While this may be sufficient for very small, early empyemas, surgical treatment is often indicated as well. The goal of surgery is to open the empyema cavity to drain the purulent, infected material and wash the area thoroughly. Because antibiotics typically do not get into abscesses well on their own, surgical drainage and debridement is usually the best treatment option. Additionally, surgery provides the opportunity to sample the infected material to isolate and identify the bacteria. This can help guide the most appropriate antibiotic therapy. The patient is then kept on a course of antibiotics for some time.

Each patient is different. Consult your own treating physicians about the most appropriate treatment strategies in your specific case.

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Important Note: This site is not intended to offer medical advice. Every patient is different, and only your personal physician can help to counsel you about what is best for your situation. What we offer is general reference information about various disorders and treatments for your education.

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