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.
Diagnosis & workup
Diagnostics & workup: - Order and interpret CT/MRI for ventricular size, periventricular edema, and catheter position - Order shunt series (skull-chest-abdomen X-rays) to evaluate catheter integrity and continuity - Prescribe and interpret CSF studies from shunt tap: cell count, glucose, protein, gram stain, culture - Evaluate Evans ratio on imaging (frontal horn width / biparietal diameter; >0.3 suggests ventriculomegaly) - Order ophthalmologic evaluation for papilledema in older children - Assess for NPH triad in elderly: gait apraxia, dementia, urinary incontinence - Consider ICP monitoring (invasive or non-invasive) in complex or equivocal cases - Evaluate ETV candidacy based on etiology, age, and MRI findings