A 10-year-old female quarter horse flipped over backwards onto its head after being spooked. Following the incident, the patient made multiple attempts to rise but would flail and progressed to having multiple seizure episodes and bilateral epistaxis. Due to the grave prognosis and perceived likelihood of potential traumatic injury to the brain and spinal cord, humane euthanasia was elected.
A necropsy exam was performed at TVMDL that revealed multiple skull fractures along the region of the basisphenoid and basioccipital bones with surrounding soft tissue edema and hemorrhage. There was edema and hemorrhage with large blood clots surrounding the ventral aspect of the cerebellum, brainstem, and spinal cord.
Image from Dyce KM, et al. Textbook of Veterinary Anatomy. Philadelphia: WB Saunders Co., 2002.
Head trauma is common in horses and can occur during normal activities such as halter training, loading onto a trailer, restraining for an examination, and grooming. It can result from things such as the horse flipping and falling over backwards, running into a fixed object (i.e fence posts), getting hit by a moving object, entrapments, trailer accidents, or direct injury from being kicked by another animal. Head trauma is often more common in young animals due to a lack of training experience or overexcitability. Clinical signs of a traumatic brain injury can include: seizures, fainting, epistaxis, sudden blindness, ataxia, unresponsiveness, and nystagmus.
An initial examination can include a thorough physical examination, sedation, and gentle cleaning and palpation of visible external wounds. Skull radiographs or CT images can allow for better evaluation of the fracture site and to see which structures are involved. If the nasal passages are impaired, then breathing can be compromised. Unfortunately, in some case, sudden injury to the head can result in sudden death of the horse.
In horses, many injuries to the skull result in fractures to the basisphenoid and basioccipital bones. This is due to an inherent structural failure of the insertion point of the rectus capitus ventralis muscles (Fig 1: C) at the junction between the basisphenoid (Fig 1: A) and basioccipital (Fig 1: B) bones. When the horse flips over and hits the poll of the head, the forces that drive the head forward create traction on the rectus capitus ventralis muscles resulting in an avulsion of the basisphenoid and basioccipital bones from the rest of the skull. Hemorrhage comes from rupture of the musculature and associated vasculature but also from the the venus sinuses associated with the adjacent roof of the guttural pouch. Many horses will exhibit neurological signs immediately after the trauma occurs. This is a catastrophic injury and associated with high morbidity and mortality.
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REFERENCES
Ramirez, O., III, Jorgensen, J.S. and Thrall, D.E. (1998), Imaging basilar skull fractures in the horse: a review. Veterinary Radiology & Ultrasound, 39: 391-395.