Table 2. Kynurenic acid (KYNA) levels in the serum of patients with normal pressure hydrocephalus (NPH) and hydrocephalus e-vacuo (He-v), and in the corresponding control subjects (controls). Data represent mean ± SEM. Number (N) of subjects is given in parentheses. Significance: **p < 0.01 vs. the respective control group age ≤ 50 years or ≥ 51 years using a Student's t-test