Pterygoid bone medialisation linked to poor BOAS surgical outcomes in French Bulldogs, new research shows

15 September 2025

A new study has found that medialisation of the pterygoid bones can significantly narrow the nasopharynx and limit the effectiveness of Brachycephalic Obstructive Airway Syndrome (BOAS) surgery, especially in French Bulldogs. Measuring the severity of pterygoid bone medialisation before surgery may be useful as a guide to the likely prognosis.

The study, funded by BSAVA PetSavers and published in the Journal of Small Animal Practice, is the first to investigate the effect of pterygoid bone medialisation and nasopharyngeal narrowing on BOAS surgical outcomes in brachycephalic and non-brachycephalic dogs.

Researchers at the University of Cambridge Department of Veterinary Medicine analysed computed tomography (CT) images of the head and neck of 144 brachycephalic dogs (French Bulldogs, Pugs and English Bulldogs) and compared with 30 non-brachycephalic control dogs. A BOAS index was determined both pre-operatively and post-operatively.

Medialisation of the pterygoid bones was more severe in brachycephalic breeds compared to non-brachycephalic breeds and was associated with nasopharyngeal narrowing. French Bulldogs were particularly affected, and those with more severe pterygoid bone medialisation were far more likely to have a poor BOAS surgical outcome.

There are currently no effective surgical interventions to correct the deformities of the pterygoid bones in BOAS-affected dogs. These findings highlight the importance of evaluating pterygoid malformations as part of clinical assessments to make more informed predictions of surgical prognosis and advise owners. Medialisation of the pterygoid bones can be easily identified via CT scans, or alternatively, simple palpation of the pterygoid bone during surgery from the oral cavity can give an indication of how medialised the pterygoid bones are.

Dr. Sze Lynn Yuen, lead author of the study, said: “BOAS is a complex disease which encompasses breed-specific anatomical lesions. The medialisation index will be useful for vets in practice to guide them on the likely prognosis prior to surgery. It would be beneficial to identify the significance of the medialisation index on a larger dataset of BOAS-affected patients as the next step.”

Read the full study here: https://onlinelibrary.wiley.com/doi/10.1111/jsap.70028