Post-hemorrhagic hydrocephalus: a neuroinflammatory perspective on CSF hypersecretion and ventricular enlargement

Hydrocephalus, defined by the excessive cerebrospinal fluid (CSF) accumulation in the brain's ventricles, emerges from varied causes such as blockages and overproduction of CSF. One major type of hydrocephalus is post-hemorrhagic hydrocephalus (PHH), which typically follows hemorrhagic incidents and predominantly affects infants. Existing treatments like ventriculoperitoneal shunting are fraught with complications, underscoring the urgent need for novel therapeutic strategies. This research delves into the pathophysiological mechanisms of PHH, concentrating on inflammation, erythrocyte breakdown, choroid plexus ion transporters, aquaporins, inflammasomes, thrombin, and the complement system in CSF hypersecretion and red blood cell lysis. Our investigation reveals elevated levels of inflammatory markers, including TNF-α, IL-1β, IL-6, and chemokine CCL-19, in CSF samples from PHH patients, pointing to the significant role of inflammation. Additionally, the complement cascade and subsequent red blood cell lysis contribute to neurotoxicity and glial scarring. Released iron exacerbates PHH through oxidative damage, while hemoglobin and peroxiredoxin-2 spark neuroinflammation. Concurrently, activation of Toll-like receptor-4 and ion transporters like NKCC1 and TRPV4 in the choroid plexus amplifies CSF hypersecretion. Moreover, aquaporins AQP1 and AQP4, along with NLRP3 inflammasome activation, further promote fluid accumulation and barrier disruption. Thrombin, interacting with protease-activated receptors, intensifies PHH pathogenesis. This review synthesizes current knowledge and proposes that PHH is a multifactorial condition driven by both mechanical obstruction and a sustained neuroinflammatory response. We hypothesize that a key contributor to ventricular enlargement is an inflammation-driven hypersecretion of CSF. Based on this neuroinflammatory perspective, we propose two novel combination therapies: one targeting both complement-mediated erythrocyte lysis and thrombin's pro-inflammatory effects, and a second combining hematoma resolution enhancers such as Simvastatin with anti-inflammatory agents like TAK-242. These hypotheses offer new avenues for therapeutic intervention beyond traditional shunting, addressing the root causes of PHH by simultaneously targeting multiple pathological pathways.