Pathophysiology
Clinical meaning
CSF is produced at 0.35 mL/min (~500 mL/day) primarily by the choroid plexus via active transport of Na+, Cl-, and HCO3- with osmotic water movement. Normal ICP is 5-15 mmHg in adults and 1.5-6 mmHg in infants. CSF absorption occurs at arachnoid granulations via pressure-dependent bulk flow. VP shunts use differential pressure valves (low, medium, high pressure), flow-regulated valves, or programmable valves (adjustable externally with magnetic tools) to regulate CSF drainage. The clinician manages the complete spectrum of shunt-dependent hydrocephalus: prescribing pre-operative medications, managing shunt valve pressure settings, treating shunt infections with targeted antimicrobial therapy, evaluating for endoscopic third ventriculostomy (ETV) candidacy, and managing long-term complications including slit ventricle syndrome, overdrainage, and shunt dependency.