[Diagnostic problems in brain abscess: 45 cases]

We analysed the difficulties encountered in the differential diagnosis between brain abscess and brain tumor and their influence on treatment and outcome.

- Forty-five adults with brain abscess operated on between 1993 and 1999 were retrospectively reviewed. We studied preoperative diagnosis, clinical, radiological, bacteriological findings, surgical procedure, primary sources of infection and outcome.

Preoperative diagnosis was right in 55.6% (25/45), wrong in 22.2% (10/45) and doubtful in 22.2% (10/45). Diffusion-weighted MR imaging was successfully used in 4 doubtful cases to make the differential diagnosis between abscess and tumor. When the preoperative diagnosis was right, the surgical procedure was a burr-hole aspiration in 73.3% (22/25) whereas when it was wrong, an excision was performed in 60% (6/10) of the cases. Aspiration was the last diagnostic investigation in 80% (8/10) of doubtful cases. Microbacterial organisms were identified in 75.5% (34/45) of the cases and primary cause of infection in 62.2% (28/45). The outcome depended on clinical status on admission, preoperative diagnosis and surgical procedure. In four cases, diffusion-weighted MRI allowed differential diagnosis between brain abscess and tumor through calculation of the Apparent Diffusion Coefficient which is low in abscess and high in cystic tumor.

The diagnosis of brain abscess remains difficult in certain patients. Correct preoperative diagnosis influences the decision on the appropriate surgical procedure and helps improve outcome.