C-reactive protein levels in the differential diagnosis of brain abscesses.

C-reactive protein (CRP) is a protein found in plasma at elevated concentrations during acute or chronic infections. As an aid in the differential diagnosis between brain tumor and abscess, the CRP levels were measured in 20 patients with intracranial mass lesions and the appearance of ring-like contrast enhancement on computerized tomography (CT) scans. In nine of these patients, the final diagnosis was abscess, based on either biopsy of the mass (eight patients) or the clinical course (one patient). In seven of the nine patients, there was a significant increase in CRP levels in two consecutive measurements. In particular, patients with cerebritis who were examined early in the course of the disease and who showed nonspecific CT scans exhibited extremely high levels of CRP. Two patients had no measurable CRP activity although they both had brain abscesses. In 12 patients harboring either gliomas or metastatic intracerebral tumors, CRP levels were significantly lower than those found in patients with brain abscesses but were nevertheless higher compared to those of a group of patients with benign tumors. It is concluded, therefore, that the measurement of CRP can have some value in the differential diagnosis between brain abscess and brain tumor. The measurement technique is inexpensive and is available in the clinical laboratories of most hospitals with a neurosurgical department.