Hydrocephalus in Dogs

Causes, Treatment, and Prevention

Chihuahua puppy with hydrocephalus
Hydrocephalus causes the head to swell.

Getty Images/cynoclub

Hydrocephalus, commonly called "water on the brain" is a neurological condition caused by an excess of cerebrospinal fluid (CSF) inside the skull. This creates pressure and swelling in the brain, which can lead to a variety of symptoms in dogs, including difficulty walking, inability to housebreak or learn simple cues, and changes in behavior.

Hydrocephalus in dogs can be congenital (the dog is born with the problem) or acquired. Toy and small breeds of dog, along with brachycephalic (short faced) breeds, are the most commonly affected. Chihuahuas, Boston terriers, pomeranians, pugs, and Yorkshire terriers are among the breeds likeliest to be stricken with congenital hydrocephalus, which usually becomes evident by 12 weeks of age.

Hydrocephalus is a serious and sometimes life-threatening condition, but depending on the severity and the cause, can often be successfully treated. Here's what you should know about water on the brain in dogs.

What Is Hydrocephalus?

Hydrocephalus, or water on the brain, occurs when cerebrospinal fluid (CSF) builds up in and around an animal's brain, leading to excessive pressure inside the skull. The condition occurs in many different species of animals, including humans.

Normally, CSF flows around the brain and the spinal cord, serving to provide both cushioning protection to these delicate structures, as well as a source of nutrients to the nervous system cells. If the normal flow of CSF is obstructed by a tumor, congenital malformation, or swelling due to inflammation, it accumulates within the skull, rather than draining as it should. In some rare situations, it is not a blockage, but excessive production of CSF which leads to the problem. Either way, because there is too much fluid and not enough space to store it within the tight confines of the skull, it puts pressure on the animal's brain. Without treatment, this can lead to brain damage and death.

Symptoms of Hydrocephalus in Dogs

The pressure in the brain results in the various symptoms pet owners may see in dogs with hydrocephalus. Symptoms can vary, but most often involve difficulty with walking normally or behavioral issues.


  • Unusually rounded or dome-shaped skull
  • Stiff or spastic gait
  • Falling over on one side
  • Walking in circles
  • Pressing the forehead against the wall or other surfaces
  • Seizures
  • Behavioral changes
  • Difficulty learning
  • Eye issues
  • Listlessness
  • Restlessness

Rounded Head

Since dogs with hydrocephalus have excess CSF in their skull, it is not unusual for them to have head swelling. The forehead or the entire skull may appear larger than usual due to the fluid inside, especially if the dog is a young puppy.

A bubble or dome shape is often used to describe the head of a dog with hydrocephalus. Young puppies with hydrocephalus may have softer skulls that can expand to accommodate the fluid but, once the skull hardens, the brain is put under pressure. This pressure then causes the other symptoms of the disease.

Stiff Gait

Most dogs with hydrocephalus display difficulty with walking. Their legs might be stiff, or the dog may have trouble with controlling its leg muscles to produce a smooth gait. Some dogs walk in circles or fall over onto their side when attempting to walk.

Head Pressing

One distinctive behavior seen in some dogs with hydrocephalus is head pressing. This is sitting with the forehead pressed against a wall or another surface.


Due to the increased pressure on the brain, seizures may occasionally be seen in dogs with hydrocephalus, but they are not as common as once thought, affecting less than 20 percent of puppies with the condition.

Behavioral Changes

A dog with hydrocephalus might seem to have changes in its personality due to the increasing pressure on the brain. Other dogs might be listless, restless, or seem anxious.

Slow to Learn

Puppies with hydrocephalus may be especially slow at learning things. For example, more than 75 percent of these dogs have extreme difficulty with housebreaking. Often, these dogs struggle to learn and retain simple commands, such as sit or stay, as well.

Eye Issues

Congenital hydrocephalus often presents in puppies with lateral deviation of the eyes (both eyes looking in the same direction towards one side), or the "setting sun sign" where the eyes are abnormally directed downwards. Other dogs might be blind.

What Causes Hydrocephalus in Dogs?

Hydrocephalus is caused by a blockage, or obstruction, of normal CSF flow around the brain and spinal cord, or by excessive CSF production that builds up faster than it can drain. In dogs, however, the first type is far more common than the second, which is usually associated with a rare form of brain tumor. There are two basic types of obstructive hydrocephalus in dogs: congenital and acquired. While the end results are the same, the causes are different.

Most dogs with hydrocephalus have the congenital form, which means they were born with structural abnormalities of their skull that restrict the ducts carrying CSF. As a result, the fluid cannot drain normally and builds up within the skull, placing pressure on the puppy's developing brain, as well as leaking into the brain itself, leading to swelling. The effects generally show within a few weeks of the puppy's birth; most begin to show symptoms between eight and 12 weeks of age.

Because congenital hydrocephalus is by far most common in certain breeds of toy, small, and brachycephalic dogs, it is assumed that the cause in these instances is an inherited characteristic. However, it is possible for any breed of puppy to have a brain infection while very young that causes narrowing of the ducts within the brain, leading to hydrocephalus. This is uncommon, though.

Breeds particularly prone to congenital hydrocephalus include:

Acquired hydrocephalus, unlike congenital hydrocephalus, does not strike certain breeds more than others, but can happen in any type of dog, young or old. In this form of obstructive hydrocephalus, the cerebrospinal fluid is unable to drain normally from the brain due to a blockage of the ducts caused most often by a brain tumor, but sometimes from swelling due to infection, inflammation, or trauma.

How Vets Diagnose Hydrocephalus in Dogs

Often, a veterinarian can diagnose congenital hydrocephalus just by the distinctive head shape and symptoms of the puppy. However, most often, the vet will order an ultrasound or CT of the puppy's head to confirm the diagnosis. In cases where acquired hydrocephalus is suspected, a CT scan or MRI of the dog's brain is required for a firm diagnosis.

Your veterinarian might also order further tests to rule out or diagnosis infections, chronic illnesses, or other conditions that might have led to acquired hydrocephalus in an older dog.

How to Treat Hydrocephalus in Dogs

Treatment of congenital hydrocephalus will vary depending on how severe the disease is. There are two possible treatment paths:

  • Medicine: Drugs that help to reduce the amount of CSF in the dog's brain, as well as relieve swelling and inflammation, are commonly prescribed, at least short-term. The antacid omeprazole, for reasons that are not understood, can reduce the amount of CSF by more than 25 percent. Corticosteroids, such as prednisone, are the most common drug used to control swelling.
  • Surgery: Surgery to place a shunt, which is basically a small tube, that stretches from the dog's brain to its abdominal cavity is the usual long-term solution for congenital hydrocephalus that doesn't respond well to medication alone. The shunt allows CSF to drain continuously from the skull, thus relieving the pressure inside the dog's head. This is a delicate surgery that is usually performed at a veterinary teaching hospital or specialty animal hospital. While the surgery carries risks, it has up to an 80 percent success rate if performed early.

For dogs with acquired hydrocephalus, treatment is aimed at the underlying cause, whether a tumor or inflammation. In these cases, options might include antibiotics, surgery, radiation, steroids or other anti-inflammatories, or a combination of treatments, depending on the situation.

Prognosis for Dogs With Hydrocephalus

Hydrocephalus is a serious condition that can have life-long ramifications. However, in puppies that are not too severely affected and receive early treatment, the prognosis is quite good, with over 70 percent showing at least some improvement of their symptoms. Dogs with acquired hydrocephalus, however, have a poorer prognosis, as most often the condition is due to a brain tumor or infection that is not easily treated, or that tends to have a fatal outcome.

How to Prevent Hydrocephalus in Dogs

Because hydrocephalus in dogs is most often an inherited defect that is present from birth, it is not easily prevented, other than by not breeding dogs with the condition.

Article Sources
The Spruce Pets uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Hydrocephalus in Toy Breed Puppies. VCA Animal Hospitals.

  3. Hydrocephalus in Canine and Feline Patients. Veterinary Neurology Center.

  4. Congenital Hydrocephalus. University of Missouri Veterinary Health Center.