Hydrocephalus and CSF Disorders
Core concepts
Understand CSF production (choroid plexus), circulation, and absorption, and the difference between communicating and noncommunicating hydrocephalus. Know the clinical presentations by age: infants (macrocephaly, sunsetting eyes, irritability), adults (headache, gait disturbance, incontinence, cognitive decline in normal pressure hydrocephalus). Understand NPH diagnosis (imaging, large-volume tap test, gait improvement) and shunt response predictors. Know shunt types (ventriculoperitoneal, ventriculoatrial, programmable valves) and complications (infection, obstruction, overdrainage). Understand endoscopic third ventriculostomy (ETV) and its indications. Recognize pseudotumor cerebri (idiopathic intracranial hypertension) and its management.
Traps
A classic trap is diagnosing NPH without a tap test or gait assessment, or attributing symptoms to NPH when another cause (Parkinson disease, spinal stenosis) is present. Another is missing shunt infection (fever, wound issues, CSF pleocytosis) and treating only for malfunction. Watch for overdrainage syndromes (subdural hematoma, slit ventricles).
Worked rule of thumb
NPH: the triad of gait disturbance, incontinence, and cognitive decline plus ventriculomegaly. A large-volume lumbar puncture with gait improvement supports shunt responsiveness. Shunt infection requires CSF analysis and often shunt removal/revision.