CHRONIC MENINGITIS - THE ROLE OF MENINGEAL OR CORTICAL BIOPSY

MENINGEAL AND CORTICAL biopsies were evaluated in 37 patients (25 men and 12 women; mean age, 54 yr) who had chronic meningitis of an unknow n cause between 1985 and 1993 (the era of magnetic resonance imaging). Magnetic resonance imaging with gadolinium contrast was the most usef ul diagnostic imaging technique, demonstrating meningeal enhancement i n 15 of 32 patients (47%). Only 2 of 32 (6%) computed tomographic scan s revealed enhancement. A definitive diagnosis was made in 16 of 41 bi opsies (39%), but in cases where enhancement was present on either mag netic resonance imaging or computed tomography, a diagnosis was obtain ed in 80% (12 of 15 cases). Only 2 of 22 biopsies (9%) from nonenhanci ng regions were diagnostic. Although the locations of enhancement were distributed evenly, biopsies through suboccipital and pterional crani otomies gave the highest diagnostic yields (50%). Furthermore, if the biopsies were obtained from enhancing regions, the yield of these two approaches increased to 84 and 100%, respectively. Of 18 cases in whic h biopsy samples were taken from both the meninges and cortex only 1 h ad cortical involvement alone. The meninges were therefore diagnostic in 15 of the 16 definitive diagnostic cases (94%). Second biopsies wer e necessary in four cases, of which the three biopsies from enhancing regions were diagnostic. The most frequent causes of chronic meningiti s were sarcoid (31%) and metastatic adenocarcinoma (25%). We made the following conclusions: 1) magnetic resonance imaging is the preferred imaging technique; 2) a biopsy of an enhancing region is most likely t o be diagnostic; 3) posterior fossa or pterional approaches give the h ighest diagnostic yield; and 4) that a cortical biopsy, although helpf ul for preserving the structural integrity of the overlying leptomenin ges, may be unnecessary and should be individualized.