Clinical History:

A 25-year-old woman was admitted to the hospital for left sided focal seizures and obtundation. She had complained of increasing headaches over the weeks prior to admission. There was also some clumsiness of her left hand and leg. She noted clonic jerking of her right arm lasting approximately five minutes which resolved with some weakness in her arm. Twenty minutes later, a similar episode occurred. On admission she was barely responsive and had a temperature of 37.8 C (100 F). She was then noted to have a left hemiparesis.

Image 7.1:

This is an enhanced head CT scan. Describe the findings. Do they help narrow down the differential diagnosis?

There is a thin enhancing ring lesion with central lucency and surrounding edema. This narrows the diagnosis to abscess.

Further history:

The patient was found to have alpha streptococcus growing in one of her blood cultures, and an echocardiogram demonstrated an atrial septal defect.

Image 7.2:

This is a gross photograph of a section of brain from another patient with the same problem. Describe the findings.

This image shows an abscess with surrounding hyperemia and discoloration in the occipital lobe. Most of the pus has fallen out of the lesion.

Image 7.3:

This is a microscopic section with connective tissue (trichrome) stain of the lesion after some months have passed. What are the various layers of this lesion?

The central area would contain the inflammatory cells or pus, the first layer represents the granulation tissue which is surrounded by the collagen of the capsule which was laid down by the adventitia of the vessels responding to the lesion. Within the surrounding brain parenchyma outside the capsule, one finds astrocytosis and edema.

Answers:

1. What are the possible causes for this type of presentation?

Because of the fever one would think of infection. With the focality of the symptoms and the progression of symptoms over several weeks, an abscess would be suspected. Tumor would also have to be considered.

2. What studies would help define this situation?

Scans would help localize a lesion and define what type of lesion was present.

3. What further studies would help define the etiology of the lesion in the brain?

Blood cultures might isolate an organism. An echocardiogram might localize the source of infection. A chest x-ray might also help localize a source of infection.

4. How would you treat her disease? What is the prognosis?

Antibiotics specific to the organism would be given. If subsequent scans did not show improvement, surgical drainage could be considered. The prognosis with response to therapy is good.