Diagnosis and findings
The occurrence and severity of TBI in horses may be determined through neurologic exam and with radiographs, endoscopy and
computed tomography (CT).
Though survey radiographs can be helpful, computed tomography (CT) may be even more useful in detection and precise localization
of intracranial structural lesions, to more precisely define the extent of cranial trauma.
Looking inside: Cranial radiograph demonstrating a basilar fracture.
What about MRI? If available, does it enhance the ability to diagnose and to see more subtle brain injuries? "Absolutely,
without a doubt," says Gary Magdesian, DVM, Dipl. ACVIM, Dipl. ACVECC, Dipl. ACVCP, associate professor, chief of equine medicine
and critical care at the UC-Davis Veterinary Medicine Teaching Hospital and Feary's mentor during her fellowship there.
"CT has markedly improved our detection of fractures and MRI would do the same for soft-tissue injury," says Magdesian.
According to Feary, "findings of clinicopathologic and cerebrospinal fluid analyses may provide additional information."
Of 34 horses with TBI (previously admitted to the UC-Davis teaching hospital), most records showed various neurologic abnormalities,
including ataxia, nystagmus, abnormal mentation, abnormal pupil size, symmetry or PLR (pupillary light reflexes), and head
Several of the horses exhibited recumbency of greater than four hours' duration, epistaxis, facial-nerve paralysis, strablamus
and seizures. Fewer showed otorrhea (blood or cerebrospinal fluid), dysphagia or blindness, and were unconscious for some
The clinicopathologic variables predominantly seen were moderate neutrophilia and mild lymphopenia; plasma osmolarity of venous
blood was reported for 13 of the 34 animals. Horses with higher PCV at the time of hospitalization were less likely to survive.
Defining view: A CT image demonstrates a fracture of the calvarium.
In Feary's study, the dominant injury (15 of 34 horses) was basilar and temporal bone fractures associated with poll impact,
as well as bony fractures of the calvarium.
Of the 34 horses, 11 did not have a fracture of the cranium identified by radiography, CT or endoscopy, nor upon postmortem
diagnosis. "It should be noted that serious brain injury in no way requires the presence of a fracture, and the presence of
a fracture does not necessarily indicate severe brain damage," says Ragle. "The most important indication of the seriousness
of head injury is the duration and progression of recumbency and mental stupor."
Though obvious severe head trauma often leads to TBI, and the result is fairly obvious, that is not always the case. "I believe
head trauma can be subtle. We often see horses that are mildly depressed or have altered gait or subtle neurologic abnormalities
that could be the result of TBI. Many cases are likely missed and heal with time," Magdesian says.