Fig. 5. CSF/serum ratios of kynurenic acid (KYNA) in patients with normal pressure hydrocephalus (NPH) and hydrocephalus e-vacuo (He-v) and in the corresponding control subjects (CO). Data represent mean ± SEM. Number (N) of subjects is given in parentheses. Significance: *p<0.05, **p<0.01, ***p<0.001 vs. the respective control group age ≤ 50 years or ≥ 51 years using a Student's t-test.