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Hydrocephalus in Chihuahua puppies

Buying a healthy puppy is more than just having the vet check the puppy over at 6 weeks when a breeder takes the litter in for their first vaccinations.

Health testing is breeding from healthy (tested) parents, understanding the DNA results you have, adjusting your breeding to account for what might be revealed by the DNA profile, and recognising health issues when they crop up, like hydrocephalus.

Hydrocephalus occurs when there’s an abnormal amount of cerebrospinal fluid around the brain. The fluid build-up puts pressure on the brain and causes severe problems for affected dogs. The pressure causes brain swelling, puts pressure on the brain and can lead to permanent brain damage or death.

Chihuahuas, because of their head shape, are predisposed to hydrocephalus. There are varying degrees of severity, but these are the main symptoms to look for:

  • Excessively domed skull (out of proportion to the rest of their body)

  • Wide set eyes (often with the whites showing)

  • Open fontanel (molera) or soft spot on the head

  • Lack of coordination

  • Kicking out front legs when walking

  • Weak back legs

  • Smaller in size than littermates

In severe cases, you may also notice:

  • Erratic or restless behaviour

  • Standing with legs crossed

  • Bumping into things

  • Slow growth

  • Difficulty in house training

  • Difficulty drinking or eating

  • Compulsive circling

  • Seizures

  • Blindness

Congenital hydrocephalus is a birth defect. The skull appears very large and domed (and many breeders get excited at this point because of the “great head”) with a large open molera located on the top of the skull. It’s not until other symptoms appear that this joy turns to disappointment, when a breeder realises that not only do they not have a great breeding/showing prospect, but the dog may suffer a shortened life and ongoing pain from the pressure on its brain.

It’s not easy to diagnose congenital hydrocephalus in very young puppies. The symptoms don’t really become obvious until the puppy is walking and eating on their own and things like lack of coordination can be put down to the puppy just being a puppy. And not all puppies with large open fontanels will develop hydrocephalus. An ultrasound evaluation is needed to confirm the diagnosis. It will show dilation of the brain ventricles if the pup is affected. A CT scan or MRI is needed to determine the exact source of the fluid build-up and how severely the dog is affected, although that may be obvious if the dog is already having seizures.

Unaffected dogs can develop the same symptoms through Acquired Hydrocephalus. This occurs when something happens to the dog (injury or tumour, for example) and the cerebrospinal fluid is blocked or altered by swelling, infection or a tumour.

When caught in the early stages, hydrocephalus can be treated to reduce inflammation or the amount of cerebrospinal fluid being produced. Severe cases are treated with corticosteroids and anti-seizure medications. Surgery to place a ventriculoperitoneal shunt can be done, but it’s a very specialist and expensive procedure.

Puppies with congenital hydrocephalus generally do all right once treatment has begun if there is no severe brain damage, although obviously they can’t be bred from. With acquired hydrocephalus, the treatment plan would focus on the underlying condition causing the problem. This could mean anything from medication to surgery or even radiation therapy. In extreme cases, supportive care may be the only course of action to keep the dog comfortable.

We’ve been very fortunate to only have one pup affected so far, and sadly he crossed the Rainbow Bridge at 4 weeks of age from a brain bleed and was diagnosed post-mortem. But it is endemic in the breed and sometimes ignored by breeders who either don’t know the symptoms of hydrocephalus, don’t know what it is, or are unethical enough to think that fabulous round head is worth it, even if it means the dog leads a life of pain and discomfort.

Always check, when buying a puppy, that the pup is not showing any symptoms of Hydrocephalus and if you’re not sure, talk to your breeder. If their answer is “hydro-what?” then you’ll have a fairly good indication of their level of knowledge and how perfunctory their “health testing” is.

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