While some hydrocephalus is present from birth, acquired hydrocephalus develops later in life — in infancy, childhood, or adulthood — as a result of something that disrupts CSF flow or absorption. Understanding what can cause it helps explain why it happened to you or your loved one.
What it means Acquired hydrocephalus is hydrocephalus that arises after birth, in a brain that previously had normal CSF balance. Something changes — a bleed, an infection, an injury, or a growth — that interferes with the production-flow-absorption balance, and fluid begins to accumulate.
Common causes Acquired hydrocephalus can follow a range of events:
- Bleeding (hemorrhage). Bleeding in or around the brain can block CSF pathways or impair absorption. In premature babies, bleeding within the ventricles (intraventricular hemorrhage) is an important cause. In adults, bleeding from a ruptured aneurysm (subarachnoid hemorrhage) or other causes can lead to hydrocephalus.
- Infection. Infections such as meningitis can cause inflammation and scarring that block CSF flow or absorption.
- Brain tumors. A tumor can physically obstruct the ventricular system or interfere with CSF dynamics, causing fluid to back up.
- Head injury (trauma). Significant head trauma can disrupt CSF pathways or absorption.
- Complications of prior brain surgery.
How symptoms appear Because acquired hydrocephalus develops in a brain that was previously normal, symptoms reflect rising pressure inside the skull and depend on age. In adults and older children, this often means headaches (frequently worse in the morning or when lying down), nausea and vomiting, vision changes, balance problems, drowsiness, and difficulty concentrating. In babies whose skull bones haven't fused, the head may enlarge and the soft spot may bulge. Symptoms may come on suddenly (for example, after a bleed) or more gradually.
How it's diagnosed and treated Diagnosis uses brain imaging — CT or MRI — to show enlarged ventricles and often the underlying cause. Treatment addresses both the hydrocephalus and, where possible, its cause:
- The hydrocephalus itself is treated with a shunt or, for suitable obstructive cases, an ETV.
- In urgent situations (such as after a severe bleed), a temporary external ventricular drain (EVD) may be placed first to relieve pressure quickly.
- The underlying cause — a tumor, an infection, a bleed — is treated as appropriate.
Outlook The outlook for acquired hydrocephalus depends largely on its cause and how quickly it's treated, as well as on any damage from the underlying event. When the fluid buildup is relieved promptly and the cause is managed, many people recover well, though some effects may persist depending on the situation. Your care team can explain what to expect based on the specific cause.
The key point is that acquired hydrocephalus is a response to an identifiable event or condition, and treating both the fluid buildup and its cause gives the best chance of a good recovery.