What it is
Cerebrospinal fluid (CSF) is produced continuously in the brain's ventricles, circulates through and around the brain and spinal cord, and is absorbed back into the bloodstream. Hydrocephalus develops when this flow is disrupted — either because the pathways are obstructed (obstructive hydrocephalus), absorption is impaired (communicating hydrocephalus), or, rarely, because production is excessive.
When fluid accumulates faster than it is absorbed, the ventricles enlarge and intracranial pressure can rise. The effects depend on whether this happens acutely (which can be life-threatening) or gradually (which may produce a more subtle, progressive picture).
Normal pressure hydrocephalus
A distinct syndrome called normal pressure hydrocephalus (NPH) predominantly affects older adults and produces a characteristic triad: gait difficulty, cognitive decline, and urinary urgency or incontinence. Despite ventricular enlargement on imaging, opening pressure on lumbar puncture is often in the normal range. Shunting can produce meaningful improvement, particularly in gait, in appropriately selected patients.
Treatment
Two main approaches are used depending on the type of hydrocephalus:
- Ventriculoperitoneal (VP) shunt — a catheter placed in the ventricle drains excess fluid to the abdominal cavity where it is absorbed. Reliable and durable, though shunts can malfunction over time and may require revision.
- Endoscopic third ventriculostomy (ETV) — a small opening is made in the floor of the third ventricle to allow CSF to bypass the obstruction. Avoids hardware altogether when anatomy is appropriate. Best suited for obstructive hydrocephalus in certain age groups.
The correct choice depends on the underlying cause, patient anatomy, age, and prior surgical history.