Obstructive hydrocephalus happens when spinal fluid is blocked inside the brain, so pressure rises quickly. Symptoms can appear within hours in adults, or within days in babies.

The hallmark is a sudden, pounding headache that is worse in the morning or when bending forward. Coughing or sneezing can feel like a hammer hit inside the skull.

Nausea and vomiting follow the headache, often with little warning. A person may throw up and feel better for a short time, then the sickness returns.

Vision blurs at the edges first, like looking through a tunnel. Lights can seem too bright, and quick eye movements hurt.

Balance is shaky. Walking turns clumsy, as if the floor is tipping, and quick turns can lead to falls.

Thinking slows. Questions take longer to answer, names slip away, and a simple grocery list feels overwhelming.

In babies, the head grows faster than normal, the soft spot bulges, and the scalp veins look more noticeable. The infant may be fussy, vomit often, and their eyes may turn downward (“setting-sun” sign).