Cerebral abscess

IMAGE OF THE WEEK 2012

WEEK 18

CEREBRAL ABSCESS

	Figure 1: Non-contrast CT brain showing an area of low attenuation in the right temporal region suggestive of an infarct or oedema. (Click on picture to enlarge)
	Figure 2: Contrast CT brain showing the same area as Figure 1 which is cystic and well demarcated with surrounding oedema typical of a cerebral abscess (Click on picture to enlarge)
	Figure 3: Contrast CT brain (saggital cut) showing the same area as Figure 1 which is cystic and well demarcated with surrounding oedema typical of a cerebral abscess (Click on picture to enlarge)
	Figure 4: Contrast CT brain (coronal section) showing the same area as Figure 1 which is cystic and well demarcated with surrounding oedema typical of a cerebral abscess (Click on picture to enlarge)

Cerebral abscess can occur de-novo secondary to septacemia, but are most commonly associated with infection in the adjacent para-nasal sinuses, mastoid air cells, ear or dentition.

The immunosuppressed are most susceptible, either due to retroviral disease, immunosuppressive therapy or those with diabetes mellitus.

Anaerobic Streptococcus is the most commonly responsible organism, although cerebral abscesses not uncommonly (up to 20%) contain multiple organisms.

Abscesses are commoner in the supra-tentorial brain, classically located at the corticomedullary junction. CT is usually diagnostic with 90% showing rim enhancement and significant perilesional oedema. Only a small proportion contain gas.

MR is most sensitive showing a cystic lesion with high T2 signal, usually with a well-defined wall, which may be of low signal. The characteristic feature is that the diffusion weighted imaging shows restricted diffusion – bright on the B1000 image and dark on the ADC map. This is characteristic, but can also occur with necrotic tumours, so requires strong clinical correlation.

Images and text contributed and prepared by

Dr Ian Bickle, Department of Radiology,