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What is Open Fontanel?

In many cases, open fontanelles in dogs may be a sign of a condition called hydrocephalus, or an abnormal cerebrospinal fluid accumulation in the brain. Many believe that the increased pressure from this accumulation can cause the holes in the skull.  Hydrocephalus can be acquired or genetic, and can be a fatal condition. While it is often seen with open fontanelles in dogs, there are many cases of the presence of these skull holes without hydrocephalus.

Open fontanelles are holes in the skull that result from incomplete closures of the skull’s soft spots during normal growth in puppies. While for many dogs these soft spots close completely by 9 to 12 weeks of age, various smaller breeds of dogs, including toy and tea cups breeds, retain these holes past puppyhood. For Chihuahuas, the open fontanelles are considered a breed standard and are called moleras. For other dogs, they can be a symptom of a serious problem.

Symptoms of Open Fontanel in Dogs

The main symptom of an open fontanel is a soft spot or hole in the skull that remains into adulthood in a dog. For many dogs, these open fontanelles will cause no problems, but can result in injuries if subject to trauma. For other dogs, open fontanelles can be a sign of a bigger problem, such as hydrocephalus. Signs your dog may be experiencing this condition can include:

  • Presence of soft spots or holes in skull, usually located on the top of the head
  • Round, domed, or apple-shaped skull
  • Eyes directed downwards or upwards
  • Head pressing
  • Difficulties with housetraining
  • Puppies slow to grow
  • Restlessness
  • Aimless wandering
  • Lack of coordination
  • Blindness 
  • Seizures


Causes of Open Fontanel in Dogs

Open fontanelles are often a congenital defect, but it can be an acquired condition due to a problem that puts pressure on the skull and cause it to be unable to fuse completely. Reasons for open fontanelles to occur include:

  • Genetic defect
  • Hydrocephalus
  • Swelling or infection of the brain
  • Brain tumor
  • Disease process that blocks cerebrospinal fluid drainage

Breeds commonly affected with open fontanelles include many toy breeds and short faced, or brachycephalic breeds, such as: 

  • Chihuahuas 
  • Miniature Dachshunds 
  • Pomeranians
  • Shih Tzus
  • Yorkshire Terriers 
  • Maltese
  • English Bulldogs 
  • Lhasa Apsos
  • Boston Terriers 
  • Cairn Terriers 
  • Pugs
  • Pekingese 
  • Toy Poodles


Diagnosis of Open Fontanel in Dogs

If you’ve noticed a domed or apple-shaped appearance to your dog’s skull, or have felt soft spots past puppyhood, you should talk with your veterinarian. The sooner you seek medical advice, the better it may be for your dog. Be sure to inform your vet about any symptoms you may have seen. 

Your veterinarian will examine your dog and ask questions about any behavioral or neurological abnormalities. Imaging techniques can show the presence of an open fontanel, fluid accumulation, tumors, or other abnormalities, and can include X-rays, ultrasounds, CT scans or MRIs. Results from these tests can confirm the presence of an open fontanel, as well as a condition such as hydrocephalus.



Treatment of Open Fontanel in Dogs

For some dogs, the presence of an open fontanel requires no treatment, but may necessitate some special handling. Often, these dogs are adopted into families without other animals or even children, with instructions to avoid any traumas to the head. While it may resolve in puppies, an open fontanel will remain with an adult dog throughout his entire life. For those dogs who have associated or concurrent problems, such as hydrocephalus, treatment is usually needed. 


If caught early, hydrocephalus is treated with medication to reduce both brain inflammation, such as with corticosteroids, and the amount of cerebrospinal fluid produced, often with omeprazole. More severe cases may also need anti-seizure medications, diuretics to reduce fluid production, and electrolytes.


For a more permanent solution, a ventriculoperitoneal shunt can be placed. This is a small tube surgically implanted into a ventricle of the brain to take the excess cerebrospinal fluid and safely drain it to another part of the body. As your dog grows, additional surgeries are often required to re-fit the shunt. Complications of this procedure include infections, and over or under drainage. The success rate for a shunt is approximately 80%. While this procedure can help a case of hydrocephalus from worsening, it does not resolve the open fontanel itself.



Recovery of Open Fontanel in Dogs

Recovery of an open fontanel in your dog will depend on the severity of his condition. If your dog has an open fontanel, but no other medical issues, then he can live a long and healthy life, so long as he receives no direct trauma to that area. If your dog’s condition is more severe, with associated hydrocephalus, treatment can help to resolve symptoms. While symptoms in some dogs may resolve in two years, other cases may need repeated treatments of medications or surgery to place or re-fit a shunt. You may need to administer medications or postoperative care to your dog at home, and ensure a safe and trauma free environment throughout his lifetime. 

Prevent open fontanelles and hydrocephalus in future generations by refraining from breeding affected dogs. If you have a breed of dog which is known for these conditions, monitor your puppy’s growth and seek advice from your veterinarian if you notice any of the associated symptoms.



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Open Fontanel Questions and Advice from Veterinary Professionals

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Hi!😊 I have a 12-13 months old Chihuahua puppy at home and I am scared that he can hit his soft spot. In general he is a quite jumpy and happy dog which is super cute but it doesn't make it easier or makes it less scary when he comes really close to the wall etc.😐 He has quite good coordination and he walks, runs and jumps normally. How can I tell if he hit it? And any tips of preventing it besides when playing a little to sit at the door to cover the pointy edge? Thanks in advance for the help!😊

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