Hydrocephalus in Cats

What Is Hydrocephalus in Cats?

Hydrocephalus occurs when there is too much cerebrospinal fluid (CSF) in the brain, commonly referred to as “water on the brain.” CSF is made by the brain ventricles, hollow spaces inside the brain matter, and it bathes the brain and spinal cord. It normally provides much-needed nutrients and protection from pressure changes and physical trauma.

In cats, hydrocephalus is considered a rare condition and usually occurs because of a congenital birth defect, when the developing skull bones at first grow to adapt to the increased fluid. Then when the skull bones stop growing and fuse, there is no longer space for extra fluid, and pressure within the skull increases. This damages the brain, leading to neurologic signs.

Hydrocephalus can also develop after traumatic brain injury, infection, or cancer. Essentially, anything that would either block the flow of the CSF from the brain and down the spinal cord or cause an increase in its production can lead to hydrocephalus.

It’s usually only considered an emergency in an acute setting—usually an older cat having just experienced some sort of trauma or having severe neurologic dysfunction. For many cats, even with therapy, the disease progresses, and many are humanely euthanized.

Symptoms of Hydrocephalus in Cats

Symptoms of congenital hydrocephalus usually shows up a few months after birth, but many cats may not develop symptoms until well into adulthood. Affected kittens may be described as:

• Smaller in size than their littermates

• Having a dome-shaped skull (congenital and acquired)

• Having open fontanelles (soft spot)

• Having bilateral ventrolateral strabismus, where a cat’s eyes appear to be looking downward and outward (congenital and acquired)

• Having variable neurologic dysfunction (congenital and acquired):

  • Changes in behavior

  • Restlessness

  • Head pressing

  • Walking in circles

  • Altered walk (often appearing clumsy)

  • Tetraparesis (weakness in all four limbs)

  • Seizures, though less likely

  • Blindness

Causes of Hydrocephalus in Cats

Hydrocephalus in cats is generally classified into two categories:

1. Congenital—Congenital hydrocephalus is more common, with birth defects affecting the cerebellum and/or skull. It often occurs with other diseases such as syringomyelia (fluid pockets that develop within the spinal cord).

   • It is thought that this condition is inherited in breeds such as the Siamese, but it has been known to occur in other breeds like the Persian and Manx. Additionally, kittens exposed to the feline panleukopenia virus or certain toxins/medications such as griseofulvin before birth can develop hydrocephalus along with other birth defects.

2. Acquired—Any disease that blocks the CSF flow or any loss of brain tissue such as in the case of trauma and hemorrhage; cysts; inflammation (swelling); bacterial, fungal, and viral infections (feline infectious peritonitis); and cancer can lead to a backup of CSF into the brain or greater amounts being made.

How Veterinarians Diagnose Hydrocephalus in Cats

Diagnosis of hydrocephalus is made after finding certain characteristics during a physical examination and in imaging of the skull and brain. Cats will often have a dome-shaped head and neurologic dysfunction to some degree.

If trauma is known to have occurred, be sure to mention the details with your veterinarian, as some cases of acquired hydrocephalus require immediate lifesaving treatment.

Radiographs are also helpful, as they will show a dome-shaped yet thin-walled cranium, but the diagnosis is best made with ultrasound through the open fontanelles or with a CT scan or an MRI.

Analysis of the CSF along with a culture will most likely be recommended to rule out other conditions and to help with surgical therapy. Blood work such as a complete blood cell count, internal organ function screening test, and feline leukemia and feline AIDS (FIV) testing will also be done.

Treatment of Hydrocephalus in Cats

Treatment of hydrocephalus in cats is usually aimed at the underlying cause, if known, but it usually doesn’t lead to long-term healing, since the disease is progressive. Medical management offers temporary relief in symptoms and is usually considered palliative (not a cure). Many cats require lifelong therapy.

Certain drugs such as furosemide and prednisolone can be given, as they lower the amount of CSF made; however, cats will need to be checked often and have frequent blood work because of drug side effects such as kidney injury, heart disease, and diabetes.

In the acute setting, a drug such as mannitol may be given to lower the pressure within the brain.

Surgical management has risks but can often lead to a better long-term prognosis, with a surgical success rate anywhere from 50 to 75 percent, especially for those with a congenital cause. Cats with severe neurologic problems and those that have failed medical management are often recommended for surgery. There are several surgical techniques, but all involve the surgical placement of a shunt, or small tube, within the brain that is then tunneled underneath the skin and connected elsewhere in the body, usually the abdomen. The shunt sends extra CSF into another area of the body, where it is easily absorbed.

Cats with a CSF infection or infection elsewhere in the body or cats with abnormal CSF are often unable to receive surgery.

Cats with hydrocephalus secondary to cancer may undergo more surgeries, radiation, or chemotherapy. Immunosuppressive drugs like steroids may be used for cats with auto-immune related causes. Antibiotics and antifungal agents may be prescribed for infectious causes.

Recovery and Management of Hydrocephalus in Cats

The prognosis for cats suffering from hydrocephalus is poor. Some cats may have little pain and can manage well with medication alone, but those suffering from extreme pain or neurologic issues are less likely to recover.

Additionally, as cats affected with hydrocephalus often have neurologic problems, it is recommended to keep them away from others and away from stairs, pools, sharp corners, and other potential dangers, as their balance and coordination may be affected.

For cats having undergone surgery, recovery often takes several weeks. Some can go on to have a fairly functional life if no permanent neurologic damage occurred because of the increased pressure on the brain. Other cats may show lifelong neurologic symptoms that are mild, such as difficulty walking or trouble with future training.

A recovery cone may also be needed during recovery to prevent your cat from scratching at the shunt. Some complications can arise after surgery in cats receiving a shunt, such as infection; shunt failure from blockage, kinking, or bending; or too much draining of CSF, which can lead to low intracranial pressure and subdural hematoma (brain bruise) formation.

If you notice anything out of place or your cat’s symptoms worsening, be sure to have them examined right away!

If your cat is prescribed medication, chances are they will be on those for a long time, if not for life, so do not stop them unless told to do so by your veterinarian. The significance of these medications’ side effects is high, so future follow-ups with drug checks and blood work will be needed.

It’s important to work with your vet to help manage your cat’s condition and ensure the best outcome possible, as their pain and symptoms will most likely worsen over time, needing more follow-ups or testing.

Prevention of Hydrocephalus in Cats

Unfortunately, there’s little you can do to prevent hydrocephalus from happening, but having your cat examined at the first sign may lead to a better prognosis while minimizing its harmful effects.

Keeping your cat indoors and having them routinely examined and up to date on their vaccines and flea and heartworm preventive is very important, along with preventing head injuries, which can occur from motor vehicle accidents or falls.

Additionally, as the condition is thought to have a genetic trait, cats with this condition and cats that are carriers (i.e., breeding pairs) shouldn’t be bred, because of the possibility of passing on harmful traits.