Presentation
Recent (days to a couple of weeks) of cognitive decline and behavioral change.
Patient Data
CT demonstrates a left-sided, hypodense, frontotemporal lesion with ill-defined margins and patchy contrast enhancement, most notable in the leptomeninges of the Sylvian fissure and floor of the middle cranial fossa.
MRI confirmed these findings. The peripheral contrast enhancement around the lesion is irregular (sometimes referred to as furry). The degree of vasogenic edema is less than one would expect for a cerebral abscess, which may be due to partial treatment and relatively chronic time-course.
MRS demonstrates a very high lactate peak.
Most convincing is the very pronounced restricted diffusion (DWI and ADC).
Features are consistent with an abscess, likely secondary to pachy / leptomeningitis which in turn was secondary to direct ascent of infection from the neck - probably from a thrombosed and infected emissary vein.
Case Discussion
This patient had been treated over the preceding weeks for a left-sided parapharyngeal abscess, before presenting with altered mentation. They went on to have a craniotomy and evacuation of the cerebral abscess.
Microbiology
Specimen Type: Pus
Description: Left Frontal Cerebral Abscess
GRAM STAIN
- Leukocytes: +++
- Gram-positive bacilli: +++
- Gram-negative coccobacilli: +++
- Gram-negative bacilli: +
CULTURE
- Prevotella Sp: +++
- Propionibacterium acnes: +++
Discussion
Historically direct extension from adjacent infections was the most common source of cerebral abscesses. More recently hematological spread has become the most common etiology.
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