Hydrocephalus and CSF Disorders
Core concepts
Understand CSF production, circulation, and absorption, and the classification of hydrocephalus: communicating versus noncommunicating, congenital versus acquired, and normal-pressure hydrocephalus. Know the clinical presentation across ages and the imaging findings, including ventriculomegaly, transependymal edema, and the Evans index. Learn the principles of shunt and endoscopic third ventriculostomy (ETV) management, including valve types, overdrainage, and infection. Also cover pseudotumor cerebri and its management.
Traps
- Assuming all hydrocephalus needs a shunt; obstructive hydrocephalus may be treated with ETV.
- Missing normal-pressure hydrocephalus, which presents with the triad of gait disturbance, urinary incontinence, and cognitive decline, and may improve with shunting.
- Forgetting that shunt infection often presents with fever and malfunction, and requires removal and antibiotics.
- Confusing ventriculomegaly from atrophy (ex vacuo) with true hydrocephalus.
Worked example / rule of thumb
An elderly patient with gait apraxia, urinary incontinence, and cognitive decline, with ventriculomegaly out of proportion to sulcal enlargement, may have normal-pressure hydrocephalus and warrants a trial of CSF diversion. Rule of thumb: obstructive hydrocephalus favors ETV; communicating hydrocephalus favors shunt.