Is Your Dog at Risk for Hydrocephalus?

Chihuahua puppy
Small dogs and brachycephalic breeds are most at risk of developing congenital hydrocephalus.

Specific breeds of dogs can often have a higher risk of certain health conditions. I'm well aware of this: Our little QT Pi Becker is a Chihuahua, a breed that can be prone to hydrocephalus, or water on the brain. QT Pi doesn’t have it, thank goodness, but it’s certainly something to be aware of if you have a breed at increased risk for the condition.

Here’s what you should know about diagnosing and treating hydrocephalus.

What Is Hydrocephalus?

When we say “water on the brain,” what we’re actually referring to is cerebrospinal fluid (CSF), which normally bathes and cushions the brain and spinal cord, and serves other vital neurological functions. In some dogs, excess fluid accumulates inside the skull and especially in the brain’s ventricles (the cavities that contain the fluid). When too much CSF accumulates, the ventricles become enlarged, building up pressure and potentially damaging the brain by pressing it against the skull. It gives me a headache just thinking about it.

The results of all that fluid buildup can be devastating for a pet. While some animals show no signs, seizures, gait abnormalities, partial or complete blindness, and other signs may occur. It’s not unusual for hydrocephalic dogs to die or be euthanized at an early age.

Dog breeds at risk of the congenital form of hydrocephalus (meaning that it's present at birth) include Chihuahuas, Boston Terriers, Cairn Terriers, English Bulldogs, Lhasa Apsos, Maltese, Pekingese, Pomeranians, Toy Poodles, Pugs, Shih Tzus and Yorkshire Terriers. It can also occur later in life, secondary to trauma, brain infections, tumors and other causes.

Hydrocephalus is also seen in cats, such as the Siamese breed, but with much less frequency.

Signs and Diagnosis

A pup who’s born with hydrocephalus may have a dome-shaped skull and an open fontanelle, or soft area on the top of the head where the skull hasn't completely closed, and eyes that don't align properly. An affected dog may walk funny, circle or fall over, and have difficulty gaining weight as he grows. Some press their heads against the wall or other surfaces. Other signs are behavioral, such as confusion, dullness, sleepiness, aggression or difficulty with house-training.

Most dogs with congenital hydrocephalus show signs by the time they are a year old. It can occur later in life, though, even in the geriatric years. This is known as acquired, or secondary, hydrocephalus.

A combination of physical examination, clinical signs, ultrasound of the ventricles and, in difficult cases, electroencephalograms (EEGs) and CT or MRI scans are used to diagnose hydrocephalus. Congenital hydrocephalus is usually diagnosed if the ventricles are enlarged, the dog shows clinical signs of brain dysfunction, and no other cause of the signs can be identified.

Some dogs have what’s called subclinical hydrocephalus. In other words, the ventricles are enlarged, but the dogs don’t demonstrate any of the clinical signs described above. That can change, though, especially if they develop a brain infection or suffer some sort of trauma, such as being hit on the head.


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