Open fontanel in dogs

Overview

A dog's skull is actually made up of several separate plate-like bones that start out somewhat soft, small, and separated. During birth, these plates allow the skull to flex as the head passes through the birth canal. As a puppy grows, the plates gradually grow around the brain, become more rigid (ossify).  As the bones meet, they fuse together. Four of these bones meet up at the center top of the skull; this center is the last open space to fill in with bone tissue. This space is known as the fontanel (or fontanelle) and will usually close when the puppy is 4-6 weeks of age, or may close slowly over a three to six month period. Sometimes, the fontanel never closes, leaving a hole in the top of the skull.

Open fontanels can occur in any dog, but are most prevalent in the toy breeds, including Chihuahuas, Maltese, Pomeranians and Yorkshire Terriers. Because the condition is hereditary, a dog with open fontanel should not be used for breeding.

Open fontanels can create two possible problems. The soft spot in the skull leaves the brain unprotected by bone and can be a place for a brain injury to occur. Animals with open fontanels often have other birth defects, such as hydrocephalus.  Hydrocephalus is a condition where fluid accumulates in the brain, causing neurologic signs. 

Treatment

There is no treatment for an open fontanel. This means that the owner has to be particularly aware as to the sensitivity of this area and extra care should be taken.  Care should be taken to avoid touching the area due to the potential for accidentally damaging brain tissue.  However, keep in mind that many dogs with an open fontanel live normal active lives.

References:

Bullock, Jennie. Open Fontanels. (26 February 2008).

The Hune Corporation. Open Fontanelle. (27 February 2008).

Terrificpets.com Open Skull Bones May, May Not Be Sign of Deadly Disorder. (26 February 2008).