Open Fontanel and Hydrocephalus in Boston Terrier Dogs


The last bones to fuse or ossify are four plate-like bones that meet at the topmost center of the head. These bones will normally close the gap of the skull when the puppy is around 4-5 weeks of age. There are instances when the closure of the gap is quite slow and may reach until the puppy is around 6 months old.

Certain abnormal conditions can prevent the closure of the fontanel resulting in the presence of a gap on top of the skull that can predispose two important problems—first, the brain becomes vulnerable to injury; second, a dog with an open fontanel is more prone to Hydrocephalus. Hydrocephalus literally means “water-head” or “water in the head”. It is derived from the Greek words “hydro” (water) and “cephalus” (head). It is a condition which occurs when there is a defect in the drainage system within the skull which is responsible for the absorption and elimination of the cerebrospinal fluid (CSF) from the brain.


Any breed of dog can have an open fontanel however the condition is most common in toy dog breeds such as Maltese, Chihuahua, Boston Terrier, and Pomeranian. Since the condition may be hereditary, a dog with an open fontanel should never be bred.

Hydrocephalus creates a condition characterized by the accumulation of higher than normal levels of cerebro-spinal fluid (CSF) within and around the brain. When this situation is present, it puts undue pressure on the brain and the surrounding tissues within the skull and interfering with their normal physiological functions.

Aside from being congenital, Hydrocephalus is also brought about by traumatic injuries to the head or parasitism.


A dog suffering from Hydrocephalus often manifests nervous signs. The pressure exerted on the brain can damage the tissues of the brain leaving permanent effects on a dog’s intelligence and motor skills. The head may appear to be misshapen and when examined closely, the open fontanel can be felt as a soft spot on the top of the head.

Another complication associated with Hydrocephalus is impaired vision and hearing. Other nervous signs include circling, head pressing, head-tilting, and hyper-excitability.

A case of Hydrocephalus often has a poor prognosis. Supportive treatment will help reduce the build-up of fluid either by decreasing CSF production or increasing CSF absorption. However, this can only give temporary relief. Surgery can be done to shunt CSF to other parts of the body but most cases are unsuccessful and the procedure expensive.