Magnetic resonance spectroscopic imaging associated with analysis of fluid in cystic brain tumors.

Objective: There is a growing interest in cystic lesions of the brain. Examining the cyst content of brain tumors may contribute in determining the malignancy of the given tumor accompanied by a cyst.

Methods: In this work, samples of cyst fluid from 18 patients with brain tumor were collected and studied biochemically regarding their protein, lactate contents and pH values; magnetic resonance spectroscopic images of these patients were also compared. We investigated the relation between the grade of malignancy and the lactate concentration and the discrepancy between the high levels of lactate in cysts and their alkaline environment.

Results: There appears to be a positive relation between the grade of malignancy and the concentration of lactate in the cysts' fluid. A significant two-fold increase in lactate concentration in malignant tumors cysts has been found as compared with the more benign tumor cysts (p<0.001). This increase in lactate level is probably because of aerobic glycolysis, which causes lactate production by the tumor.

Discussion: High lactate levels found through magnetic resonance spectroscopy are positively related to the grade of tumor malignancy. The pH values in the cyst fluids were above normal, resulting to a discrepancy in high levels of lactate in the cyst and the alkaline environment. This suggests efflux of H+ ions by a Na/H exchange mechanism to compensate for the change of pH.