Hydrocephalus in Cats: Symptoms, Causes, and Risk
By Dr. Zubair Khalid, DVM, MS, PhD ·
Hydrocephalus in cats symptoms usually show up as a change in head shape, an unsteady walk, or unusual behavior. The condition means fluid builds up inside or around the brain and presses on brain tissue. Some cats are born with it, and others develop it later after an infection, injury, or tumor.
This article is educational and is not a substitute for veterinary diagnosis or treatment.
Quick Answer
- A domed, rounded skull in a kitten or young cat is the classic early sign, especially in Siamese and other oriental breeds.
- A wobbly, wide-based walk, head tilt, or circling often points to pressure on the brain or brainstem.
- Behavior changes such as lethargy, staring, head pressing, or a sudden loss of house training can be the first thing you notice.
- Hydrocephalus is uncommon in cats overall, but it is more likely in certain breeds and after neurologic feline infectious peritonitis (FIP).
- Any cat with a new head tilt, seizure, or sudden collapse needs to be seen by a veterinarian right away.
What Hydrocephalus Means in Plain Words
Hydrocephalus is a buildup of cerebrospinal fluid (CSF) in the spaces around and inside the brain. CSF normally cushions the brain and spinal cord. When it cannot drain or when it is produced faster than it drains, pressure rises and squeezes brain tissue.
Vets divide it into two broad types. Congenital hydrocephalus is present at birth and often comes from a malformation that blocks fluid flow. Acquired hydrocephalus develops later in life, usually because something blocks the drainage pathways or takes up space in the skull.
The pressure can be mild or severe. In one dog, MRI showed severe congenital hydrocephalus with marked thinning of the gray and white matter of the forebrain [1]. Cats can have a similar range, from subtle changes that barely affect daily life to life-threatening compression of the brainstem.
Hydrocephalus in Cats Symptoms: What Owners Notice First
The earliest signs are often easy to miss because kittens can be clumsy anyway. Watch for a pattern that gets worse over days to weeks.
Head shape changes
A rounded, dome-shaped skull is the most recognizable sign. It happens because the skull bones of a young cat are still soft and can expand as fluid pressure rises. This is most obvious in kittens and young adults. If you compare littermates, the affected kitten may have a noticeably broader, taller head.
Walking and balance problems
An unsteady gait is common. Your cat may walk with a wide stance, sway, or stumble. Some cats circle in one direction. A head tilt or head shaking can appear when the brainstem or cerebellum is compressed. In one young adult cat, a chronic subdural hematoma caused severe cerebellar and brainstem compression along with obstructive hydrocephalus, and the cat had a one-month history of cautious ambulation, head shaking, and lethargy [2]. That case shows how pressure in the back of the brain can change how a cat moves.
Behavior and mental changes
You may see lethargy, reduced interaction, or a dull, staring look. Some cats press their head against walls or furniture. Others seem confused or stop using the litter box reliably. In severe cases, seizures or collapse can occur.
Vision and eye changes
Rising pressure can affect the optic nerves and the parts of the brain that process vision. Some cats go blind or bump into objects. A veterinarian can check pupil responses and the back of the eye during an exam.
Appetite and thirst changes
Brain pressure can disturb the centers that control thirst and appetite. A dog with hydrocephalus developed a dangerous rise in blood sodium because it stopped drinking, a problem called hypodipsic hypernatremia [1]. Cats can develop similar thirst and appetite problems. If your cat suddenly drinks much more or much less than usual, that is worth a vet visit. You can read more about this in Cat Drinking a Lot of Water: Is It a Sign of Illness?.
Causes and Risk Factors
Congenital causes
Most congenital cases come from a malformation that blocks CSF flow. The cause is often unknown. Genetics likely play a role in some breeds.
Hydrocephalus in Siamese Cats and Other Breeds
Siamese cats and related oriental breeds appear to carry a higher risk of congenital hydrocephalus. The domed head and slightly flattened face that breeders once selected for may be linked to skull shape differences. If you have a Siamese kitten, watch closely for balance problems or a head that seems to grow faster than the body. Other breeds can be affected too, so breed alone does not rule it out.
How Common Is Hydrocephalus in Cats?
Hydrocephalus is uncommon in cats compared with dogs. There is no single reliable number for how often it occurs, and most cases are reported in young cats with congenital disease. Acquired cases are rarer still and usually tied to a specific trigger.
Infection and inflammation
Feline infectious peritonitis (FIP) is a known trigger. A 2025 case series followed four cats treated for neurologic FIP and re-examined them 13 to 15 months later. Three of the four cats came back with vestibular signs, and MRI showed progressive hydrocephalus after the infection was treated [3]. This means that even cats who survive neurologic FIP can develop fluid buildup later, so long-term monitoring matters.
Viral infection before birth can also damage the developing brain. Feline panleukopenia virus is a well-documented cause of cerebellar hypoplasia in domestic cats, and a related virus caused the same brain changes in an Amur leopard cat [4]. Cerebellar hypoplasia is a different condition from hydrocephalus, but both can cause wobbliness, and both show how early infection can reshape the brain.
Tumors, bleeding, and structural problems
Anything that blocks CSF flow or takes up space can cause acquired hydrocephalus. A 2026 report described a 2-year-old cat with abnormal blood vessel growth in the occipital bone and a chronic subdural hematoma. The mass compressed the cerebellum and brainstem and produced obstructive hydrocephalus [2]. This is a rare cause, but it shows that bleeding or a mass near the base of the skull can be the trigger.
Injury and other risks
Head trauma, certain medications, and previous brain surgery can raise the risk. In cats, body position and skull defects can also shift CSF pressure. A study of anesthetized cats found that after a parietal craniectomy, CSF pressure in the lateral ventricle dropped below zero in a head-up position while lumbar pressure rose, and the pattern reversed when the head was down [5]. This research is about pressure dynamics, not a direct cause of hydrocephalus, but it helps explain why head position and skull defects matter in cats with fluid problems.
How Veterinarians Diagnose Hydrocephalus
Diagnosis starts with a full physical and neurologic exam. Your vet will check head shape, gait, pupil responses, and reflexes. They will ask when you first noticed changes and whether your cat has had FIP, a head injury, or a recent illness.
Imaging is the next step. MRI is the best way to see fluid-filled spaces, brain compression, and any mass or bleed. In the FIP follow-up cases, MRI was used to confirm progressive hydrocephalus months after treatment [3]. In the cat with the occipital bone lesion, both MRI and CT were used to define the bone changes and the hematoma [2].
Your vet may also recommend blood work, a CSF tap, and testing for infectious diseases. CSF analysis can rule out inflammation or infection. In the dog with severe hydrocephalus, CSF results were normal, which shows that a normal tap does not rule out the condition [1].
Treatment Options
Treatment depends on the cause, the severity, and whether the hydrocephalus is congenital or acquired.
Medical management
Mild cases are sometimes managed with medication to reduce CSF production and with close monitoring. Your veterinarian will calculate any dose from your cat's weight and health. Never give human medication to a cat without veterinary guidance, because some common drugs are toxic to cats.
Surgery
When pressure is severe or a blockage can be reached, surgery may help. Options include placing a shunt to drain fluid or removing a mass that is blocking flow. The cat with occipital bone angiomatosis and a subdural hematoma had a structural cause that required surgical evaluation [2]. Shunt surgery is specialized and not available everywhere, so your vet may refer you to a veterinary neurologist or a teaching hospital.
Treating the underlying cause
If FIP is the trigger, treating the virus is part of the plan. The cats in the 2025 report had been treated with GS-441524 for neurologic FIP, yet three later developed vestibular signs and progressive hydrocephalus [3]. That finding suggests that treating the infection does not always prevent later fluid problems, so follow-up imaging and exams are important.
Supportive care
Supportive care includes managing seizures, protecting your cat from falls, and keeping food and water within easy reach. If your cat has trouble drinking, your vet may need to monitor sodium and fluid balance closely, as in the dog with hypodipsic hypernatremia [1].
Recovery, Outlook, and Long-Term Management
The outlook varies widely. Some cats with mild congenital hydrocephalus live comfortable lives with monitoring and medication. Others have progressive disease that worsens over months.
| Situation | Typical outlook | What you can do |
|---|---|---|
| Mild congenital hydrocephalus | Often stable for years with monitoring | Keep routine vet visits, watch for new neurologic signs |
| Hydrocephalus after neurologic FIP | Can progress even after infection treatment [3] | Schedule follow-up imaging and neurologic exams |
| Obstructive hydrocephalus from a mass or bleed | Depends on whether the cause can be treated | Ask about referral to a neurologist or surgeon |
| Severe compression with seizures or collapse | Guarded, needs urgent care | Go to an emergency clinic right away |
Long-term management often means regular neurologic checks, repeat imaging when signs change, and medication adjustments. Keep a simple log of your cat's gait, appetite, thirst, and behavior. That record helps your vet spot trends. If your cat also has kidney or urinary issues, our guides on Symptoms Of Kidney Disease In My Cat and Symptoms Of Urinary Infection Cats can help you tell those problems apart from neurologic ones.
Prevention
You cannot prevent every case, but you can lower some risks.
- Keep your cat indoors to reduce head trauma and exposure to infectious diseases.
- Vaccinate kittens against panleukopenia and other core viruses. Early infection can damage the developing brain [4].
- If your cat is diagnosed with neurologic FIP, ask your vet about long-term follow-up, because hydrocephalus can appear months later [3].
- Spay or neuter and avoid breeding cats with known congenital neurologic problems.
- Watch kittens from high-risk breeds, such as Siamese, for early head shape or gait changes.
Limitations and When to Contact a Veterinarian
This article cannot tell you what is happening in your individual cat. Only a veterinarian who examines your cat can do that.
Call an emergency clinic now if your cat has a seizure that lasts more than a minute, collapses, cannot stand, or breathes abnormally.
Go to your vet the same day if you see a sudden head tilt, new circling, head pressing, a marked change in mentation, or a kitten with a rapidly domed head.
Schedule a routine visit soon if you notice a mild wobble, a slight change in head shape, or subtle behavior changes that have lasted more than a few days. Early imaging and a neurologic exam give your cat the best chance.
Frequently Asked Questions
Can a cat live a normal life with hydrocephalus?
Some cats with mild congenital hydrocephalus live comfortable lives with monitoring and medication. Cats with severe or progressive disease often need ongoing treatment and may have a shorter, more limited life. Your vet can give you a realistic picture after imaging.
Is hydrocephalus painful for cats?
The fluid pressure itself is not usually described as pain, but the underlying cause can be. A mass, bleeding, or severe brain compression can cause discomfort and neurologic decline. If your cat seems painful or stops eating, that needs prompt veterinary care.
Can hydrocephalus in cats be cured?
Surgery can cure some cases when a blockage or mass can be removed. Many cases are managed instead of cured, especially congenital ones. Treatment aims to control pressure, limit brain damage, and keep your cat comfortable.
Do all Siamese cats get hydrocephalus?
No. Siamese and related breeds have a higher risk, but most Siamese cats never develop it. Breed is one risk factor among several, including infection, trauma, and malformation.
Can hydrocephalus in cats get worse over time?
Yes, it can progress. Cats treated for neurologic FIP developed progressive hydrocephalus 13 to 15 months later in one report [3]. Regular checkups and repeat imaging when signs change help catch worsening early.
Related Articles
- Symptoms Of Kidney Disease In My Cat
- Symptoms Of Bladder Infection In Cats
- Symptoms Of Urinary Infection Cats
- Cat Drinking a Lot of Water: Is It a Sign of Illness?
- Pancreatitis In Cats Symptoms
- What Are Symptoms Of A Uti In A Cat
- Hydrocephalus in Cats: Signs and Persian Risk
- Hydrocephalus in Cats: Life Expectancy and Prognosis
- Hydrocephalus in Cats: Treatment and Can It Be Cured?
References
- Case Report: Hypodipsic hypernatremia secondary to hydrocephalus in a dog. Frontiers in veterinary science, 2025.
- Occipital Bone Angiomatosis and Chronic Subdural Hematoma Causing Severe Cerebellar and Brainstem Compression and Obstructive Hydrocephalus in a Young Adult Cat. Veterinary radiology & ultrasound : the official journal of the American College of Veterinary Radiology and the International Veterinary Radiology Association, 2026.
- Post feline infectious peritonitis progressive hydrocephalus: a case series. Frontiers in veterinary science, 2025.
- Cerebellar hypoplasia in an Amur leopard cat (Prionailurus bengalensis euptilura) with feline panleukopenia virus infection. Veterinarni medicina, 2025.
- Effects of craniectomy on cerebrospinal fluid pressure gradient in the craniospinal space in different body positions of cats. Croatian medical journal, 2026.