Serious severity

Hydrocephalus (Water on the Brain)

A build-up of fluid within the brain that raises pressure inside the skull, most often seen in kittens and causing a domed head, clumsiness and behavioural changes.

⚠️ Common symptoms

A rounded, dome-shaped skull, sometimes with a soft spot on topClumsiness, circling, or difficulty learning normal kitten skillsEyes that appear to point outward and downwardSeizures, dullness or episodes of confusionSlow growth and poor coordination compared with littermates

Hydrocephalus, sometimes described as 'water on the brain', occurs when cerebrospinal fluid — the clear liquid that normally cushions and nourishes the brain — builds up faster than it can drain away. As the fluid accumulates inside the brain's chambers, pressure rises within the confined space of the skull and begins to press on delicate nervous tissue.

In cats the condition is most often congenital, meaning a kitten is born with it, and affected youngsters may show a characteristically rounded, dome-shaped head, sometimes with a soft spot where the skull bones have not fully closed. Owners may notice the kitten is clumsy, struggles to learn ordinary things like using the litter tray, circles, or seems dull and behind its littermates. The eyes may take on a distinctive outward-and-downward cast. In older cats, hydrocephalus can develop as a result of inflammation, infection or a growth blocking fluid flow.

How much trouble the condition causes varies widely. Some cats have only mild signs and cope reasonably well with medication to reduce fluid and control seizures, while severely affected animals may need specialist surgery to drain the fluid, or may have a guarded outlook. A veterinary examination, often with advanced imaging, is essential to gauge severity and to give each cat the best possible plan for a comfortable life.

🔍 Causes

Hydrocephalus results from too much cerebrospinal fluid accumulating within the chambers of the brain, either because its normal flow is blocked or because it is not reabsorbed properly. In kittens it is frequently congenital — present from birth due to abnormal brain development, sometimes following an infection in the womb. It can also arise later in life from inflammation, infection or a mass that obstructs fluid drainage.

🛡 Prevention

Congenital hydrocephalus cannot usually be prevented, though good queen care, vaccination and parasite control reduce infections that can affect a developing litter. Responsible breeding that avoids repeating affected lines helps lower the risk, and prompt treatment of head infections or injuries in older cats may prevent acquired cases.

💊 Treatment

Treatment depends on how severe the fluid build-up and pressure are. Milder cases are often managed medically with drugs that reduce fluid production, such as corticosteroids or diuretics, sometimes alongside anti-seizure medication. In selected severe cases a surgical shunt can be placed to drain excess fluid away from the brain, though this is specialised surgery with real risks. A vet or neurology specialist will tailor the plan to the individual cat and monitor its response closely.

When to see a vet: See a vet promptly if a kitten has an unusually domed head, seems clumsy or slow to learn, circles, or has seizures, and seek urgent care for any cat that suddenly becomes disoriented, collapses or convulses. Early assessment gives the best chance of controlling pressure before lasting damage occurs.

⚕️ Medical disclaimer

  • This information is educational only and is not a substitute for veterinary advice.
  • Symptoms overlap between conditions — only a vet can diagnose accurately.
  • Never withhold treatment or self-medicate based on information found online.
  • When in doubt, call your vet. Early intervention almost always leads to better outcomes.

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