Hydrocephalus and CSF Disorders - exam-focused guide
Hydrocephalus and CSF Disorders covers communicating and obstructive hydrocephalus, normal-pressure hydrocephalus, shunt and endoscopic management, and CSF leaks. The exam tests diagnosis, CSF dynamics and complication recognition.
Core rules
- CSF is produced mainly by choroid plexus at about 500–600 mL/day; total volume is about 150 mL. Absorption occurs at arachnoid granulations.
- Obstructive hydrocephalus blocks ventricular flow, commonly at the aqueduct or fourth ventricle outlet. Communicating hydrocephalus has free ventricular–subarachnoid communication but impaired absorption.
- Normal-pressure hydrocephalus presents with gait disturbance, urinary incontinence and cognitive decline. Ventriculomegaly is out of proportion to atrophy. A large-volume lumbar tap that improves gait supports shunt responsiveness.
- Shunt complications include infection, obstruction, overdrainage and slit-ventricle syndrome. Shunt infection usually requires removal and antibiotics.
- Endoscopic third ventriculostomy creates a stoma in the third ventricle floor; it is suitable for selected obstructive hydrocephalus. CPC is used in selected infants.
- CSF leak after skull base surgery may cause headache, rhinorrhea and meningitis risk; confirm with beta-2 transferrin and repair.
Worked example: A 72-year-old has magnetic gait, urinary urgency and mild cognitive decline. MRI shows ventriculomegaly with tight high-convexity sulci. A 40-mL lumbar tap improves walking. This supports NPH; a programmable shunt is offered, with counseling about subdural hematoma and infection.
Traps: calling NPH "normal pressure" at all times; missing shunt malfunction because CT looks unchanged; treating slit ventricles by simply increasing shunt pressure; ignoring CSF leak after transsphenoidal surgery.