In a clinical study with very small sample size, IL-18 was found to be significantly increased together with another two pro-inflammatory cytokines (IL-33 and IL-9) in the CSF specimen collected during the MVD procedure of patients with TN (n = 8) compared to individuals undergoing MVD for hemifacial spasm (HFS; n = 2) or participants with normal pressure hydrocephalus (NPH; n = 2) (49), suggesting the presence of neuroinflammation in TN. This evidence concerns the gene IL9 and normal pressure hydrocephalus.