Furthermore, a team of veterinary scientists has determined that even treating those veterinary issues—at least among horses within a popular Arabian show lineage—is more complicated because their skulls are smaller.

“Taking in consideration specifically the Arabian show population, we have proportionally more ‘head-related’ problems, such as in the sinuses, dental structures, and guttural pouches,” said Endrigo Pompermayer, DVM, MS, of the Equine Veterinary Medical Center, in Al Rayyan, Doha, Qatar.

“And no wonder,” he said. “There are obvious differences in the head morphology (form and structure).”

Head Surgeries Harder and Riskier, but Needed More Often, in Arabians

As an equine surgeon, Pompermayer said he and his colleagues regularly operate on Arabian horses experiencing dental disease and chronic secondary sinusitis due to overcrowding teeth and poor sinus drainage.

He and his fellow surgeons started realizing that these head surgeries were not only more frequently necessary in Arabian horses but also more complicated than in horses of other breeds. In particular they consistently found that the internal structures of the head were more difficult to access, he said.

“A very common condition is an Arabian horse suffering from dental overcrowding leading to dental disease and chronic secondary sinusitis, which requires surgical treatment,” Pompermayer said. “During surgery there are often difficulties compared to other breeds, such as limited access to the same anatomical areas, making surgeries more difficult and risky for the horse.”

He and his colleagues had the impression that it wasn’t just the Arabian noses that were smaller, but the horses’ entire heads. When Pompermayer checked scientific publications on head lengths, though, he found that Arabian heads were reported to be just as long as the heads of other breeds.

In fact, in one previous study researchers suggested that Arabian heads might actually seem smaller, and that this was “just an impression given by the higher nasal profile index—the dished face,” he said. “But there were no differences on the skull length of Arabians, Thoroughbreds, and Standardbreds.”

14 Different Head Measurements Comparing Arabian and Thoroughbred Heads

Surprised by those previous findings—which didn’t line up with their own practical experience—Pompermayer and his colleagues decided to carry out their own new study.

They focused specifically on a popular Arabian show horse line, the Straight Egyptian Arabian Horse. Considered the purest line of Arabians, with pedigrees that are traceable back to the Bedouin tribes of Arabia, Straight Egyptian Arabians have since undergone “intense genetic selection for conformational traits desired for showing” and have experienced relatively high levels of inbreeding. For this reason, they are an interesting focal group for studying Arabian head dimensions, Pompermayer said.

The team recorded multiple head dimensions from 29 healthy horses aged 5 years and older, including 14 Thoroughbreds from four farms and 15 Straight Egyptian Arabian Horses from two stud farms.

Those dimensions included six basic measurements such as eye-to-eye width, muzzle circumference, and jaw width, as well as eight more advanced anatomical measurements using computed tomography (CT) on the standing, sedated horses.

The researchers found that contrary to previous studies, the Arabians’ total head length was shorter than that of the Thoroughbreds—especially relative to body size, he said.

While both breeds had similar measurements along the frontonasal bone flap, the frontal sinus was shorter in the Arabians. “In clinical cases, this means the possibility of iatrogenic (or treatment-caused) damage,” he explained.

The team also found that a sinus structure known as the maxillary septal bulla lay farther back in the Arabians. That would explain why the surgeons found it more challenging and riskier to perform maxillary septal bulla fenestrations (to facilitate sinus drainage) on Arabians, Pompermayer said.

Meanwhile, the Arabians’ maxillary bone flaps tended to be shorter than those of the Thoroughbreds, which would logically result in poorer access to their maxillary sinuses, he added.

One thing that was larger in the Arabians, though, was their globe diameter compared to their head size—meaning they had relatively bigger eyes, said Pompermayer. Thus, surgeons might need to pay special attention to sizing when performing eye surgeries and especially ocular implants or prostheses in Arabian horses, he said.

Ultimately, the team’s aim was not to prove their predecessors wrong, he explained. Rather, it was to “optimize the surgical procedures, making it safer for Arabian horses undergoing skull surgery,” Pompermayer said.

“Referring veterinarians should be aware of the anatomical differences and possibly refer to referring centers or seek for advance diagnostic imaging when dealing with Arabian head-related cases,” he said.

The study, “Straight Egyptian Arabian skull morphology presents unique surgical challenges compared to the Thoroughbred: a computed tomography morphometric anatomical study,” appeared in the American Journal of Veterinary Research in March 2023.