Brain Abscess

Case History: 50-year-old woman with onset of fever and altered mental status.

A non enhanced-contrast brain CT showed an ill-defined round hypodense area surrounded by vasogenic edema is present within the temporal lobe of the left cerebral hemisphere. After IV contrast, the images of brain CT showed a well-defined area with ring irregular enhancement of the lesion in the left temporal lobe. The paranasal sinuses and mastoid air cells appear normal.

Diagnosis: Brain abscess of the left temporal lobe.

Discussion: Brain abscess is an infectious process that causes high morbidity and mortality if undiagnosed and untreated directly. Despite the present era of antibiotics and refined neurosurgical technique, the major obstacle to successful treatment is delayed diagnosis. The development of diagnostic imaging, particularly noninvasive diagnostic imaging, plays a vital role in diagnosis and is directly responsible for improved patient outcomes.

Brain abscess often presents as a rapid developing space-occupying lesion. It usually begins with a headache, followed by focal neurological deficit or seizure, and sometimes progresses to increased intracranial pressure, vomiting, nausea and, finally, loss of consciousness. Fever is only present in 50 percent of cases, as in this case.

The causes of the brain Infection include the extension from a direct cranial focus (50 percent) or by hematogenous dissemination from an extracranial source (50 percent). The most common cranial source is mastoiditis (30 percent) followed by sinusitis (15 percent). Whereas, the most common cause of the extracranial source is hematogenous seeding from endocarditis, no identified cause is found in 20 percent of cases. In addition, rare causes include meningitis complication, retrograde thrombophlebitis from a dental or facial infection, penetrating trauma and surgery.

On CT, the typical appearance of brain abscess is a focal round lesion with a hypodense center surrounded by vasogenic edema. On CT after IV contrast, ring enhancement of the lesion is seen. Abscess secondary to mastoiditis occurs in the temporal lobe and sometimes the posterior cranial fossa. Paranasal sinusitis results in frontal lobe location and hematogenous dissemination usually results in multiple lesions following a vascular distribution.