This week, surgery expert Aidan McAlinden explains some technical terms related to the shape of the skull and what this means for brachycephalic dog breeds.
What is a brachycephalic dog?
Brachycephalia refers to a flat and wide skull shape. In dogs, it is the opposite to the skull shape of long nosed breeds such as the Greyhound which is called dolichocephalia. A brachycephlic (pronounced ‘brackee – cefalic’) skull therefore appears as though the skull has been severely compressed from front to back. In extreme cases it may appear that there is no nose present at all (see skeleton images below).
What breeds have this conformation?
Pugs are a classic brachycephalic breed
Breeds that have this skull conformation include: the Pug, English Bulldog, French Bulldog, Cavalier King Charles Spaniel, Boston Terrier, Shih Tzu and Pekinese to name the most common.
Does this conformation pose any threat to the health of these breeds?
Unfortunately the answer to this question is yes. This skull shape gives these dogs the characteristic flattened face and short nose. Although this conformation makes them appear extremely cute; a feature which matches the big personalities of many of these breeds, it also causes some serious health issues. These include skin, eye and breathing problems and a poor ability to tolerate heat.
Health issues related to a dog being brachycephalic are becoming a more significant problem. Genetic pressure has been applied over many years to achieve more extreme versions of this appearance but this has been to the detriment of their general health. This means that we are seeing these breeds earlier in life with more severe manifestations of these health problems. If we compare the skull shape and appearance of the English Bulldog of today with a skull from the same breed from fifty years ago the change is quite dramatic. Fifty years ago the skull was much longer and there was an obvious nose. However, today in most of the breed the nasal bones are extremely short or almost absent altogether.
The change in the skull shape of the British Bulldog over the last fifty years. Notice particularly the extreme for-shortening of the nasal cavity.
Image courtesy of Natural History Museum, Bern
How is their health affected by this conformation?
Deep crevices created by skin folds create an ideal environment for growth of bacteria and yeasts.
Skin: With the skull getting shorter and flatter there is excessive skin covering the underlying bones. This skin is thrown up into folds especially over the front of the face. The deep crevice created by the fold creates a warm and moist environment that encourages growth of bacteria and yeasts. These may ultimately invade the skin causing infection and inflammation. Although antibiotics and local cleansing and drying may help, recurrent infections are common because the underlying cause is not removed.
Eyes: The flattening of the skull causes the eye sockets to become shallow. This means that the eyeball protrudes significantly. As a result the cornea (outer surface of the eye) is more exposed which makes it more likely to become dry and can lead to ulceration or direct trauma.
Respiratory system: Although the skull has been getting progressively smaller over time, the amount of soft tissue in the nose and throat has remained the same. These soft tissues include the soft palate, turbinates (cartilage inside the nose) and tongue. These are all crammed into a smaller space. In addition, a lack of underlying nasal bones also causes the nostrils to become very narrow, appearing like small slits instead of open holes. The crowding of this tissue inside the nose and the back of the throat obstructs airflow through the upper airways which can lead to significant problems related to breathing. If this causes a clinical problem it is referred to as Brachycephalic Upper Airway Obstructive Syndrome – commonly abbreviated to BUAOS.
In his next article Aidan will explain this important condition in more detail.