Accidental injuries can happen to any horse at any time, and a fairly common and usually catastrophic injury is trauma to the head resulting in fracture of the skull, writes veterinarian Dr Neil Williams.
Horses often are victims of accidental injury. Their gregarious nature, social hierarchy, heightened flight response, and handling and confinement by humans puts them at increased risk of trauma.
The head of a typical adult horse weighs more than 40 pounds (18kg). This, coupled with the long neck placing the head well outside the center of mass, causes the head to strike the ground with tremendous force during a fall. Also, the speed and strength of a horse can result in severe impact of the head against an object when rearing or running.
Over a five-year period, the University of Kentucky Livestock Disease Diagnostic Center has diagnosed 34 cases of skull fracture, with a yearly average of 6.8 cases. These were diagnosed in several breeds, with Thoroughbreds predominating. The affected horses ranged in age from 2 days to 23 years. Most cases were adult horses, but yearling and younger horses were affected as well.
Horses suffering a skull fracture often had a history of being handled with the horse rearing and flipping over, striking the head on the ground, or hitting its head on an overhead structure such as a trailer or stall ceiling. In other instances the history indicated the horse running directly into an object, such as a tree, fence, or barn. Occasionally, the horse was simply found dead with the causative event not being observed. The clinical signs in horses suffering a skull fracture included ataxia, recumbancy, paralysis, blindness, nystagmus, seizures, coma, and death. Hemorrhage from the nose or an ear was sometimes observed. Medical treatment was usually attempted; however, the horses often died or the severity of the injury necessitated euthanasia.
The diagnosis was made or confirmed at necropsy. The pathological findings among cases were similar. These sometimes included scrapes or excoriation of the skin on the head, and bruising and hemorrhage of the subcutaneous tissue at the point of impact. Hemorrhage in an ear canal, nasal passages, or a gutteral pouch was not unusual.
Commonly, there was epidural hemorrhage and tearing of the meninges, with hemorrhage into the brain and around the anterior cervical spinal cord. Fractures involved many of the different bones comprising the skull. The structure of the skull makes the occurrence of one fracture unlikely. The force resulting in a fracture and displacement in one area is transferred across the skull, fracturing another area. The occipital bone was most commonly fractured with a concurrent fracture of the basisphenoid bone. These fractures sometimes involved the acoustic meatus, with bleeding into the ear.
Fractures of this type are typical in a horse that flips over backward, striking its head. In contrast, running into an object or being kicked was associated with fracture of the frontal bone. Other bones fractured in this type of injury included the parietal, temporal, and zygomatic bones. Fractures of the frontal bone were often associated with hemorrhage into the frontal sinus and nosebleed.
It is important to recognize that horses are susceptible to this type of injury and how serious head injury can be. Special care is warranted when handling extremely nervous or “flighty” horses so that they are not put in situations or an environment where injury is more likely to occur if the horse becomes unruly or panics.