The link between head injuries (specifically traumatic brain injuries) and subsequent development of seizures in people is clear. So, I was surprised to learn that, until recently, no similar studies have been done in dogs and cats. I’d have thought that with the number of cases of hit-by-car, high-rise syndrome, etc., that we vets see, someone would have thought to investigate the question, "Do dogs and cats develop seizures after head trauma?"
Two papers published in the December 1, 2012 issue of the Journal of the American Veterinary Medical Association seek to provide an answer. A team of German veterinarians reviewed medical records from the Small Animal Clinic of the Department of Veterinary Clinical Sciences at Justus-Liebig-University in Giessen, Germany. They interviewed the owners of 52 cats that had been admitted for treatment of head trauma, at least 2 years later, to determine whether their pets had developed seizures. None of the cats did.
The situation is different in dogs. Another team of veterinarians looked at the records of 259 dogs that were evaluated for head trauma at The Ohio State University. They found that 3.5% of these dogs developed seizures while they were still hospitalized, and 6.8% developed them after being discharged from the hospital. When a specific diagnosis of traumatic brain injury could be made, 10% of dogs developed seizures while hospitalized. For comparison, the veterinary hospital had a background epilepsy rate in dogs of 1.4 %.
Why the difference between cats and dogs? I don’t have a definitive answer, but these results fit with my clinical experience. Primary care veterinarians see dogs with a history of seizures on an almost daily basis. This is not the case with cats. I remember from my vet school days being taught that seizures in cats are "really bad." When a cat has seizures you can be fairly certain that something important (tumor, infection, etc.) is going on intracranially. On the other hand, some dogs just seem to be looking for an opportunity to seize. (I once had a patient that would drop to the floor and convulse every time he walked through my clinic’s door. We assumed it was stress and made house calls from then on.)
Anatomy may also be playing a role. Cats are just smaller and more delicate than all but the tiniest breeds of dogs. I suspect events that might cause a traumatic brain injury in a dog are frequently fatal in cats. Many years ago, I saw a dog run into the side of a moving car. The leading edge of the bumper clocked him hard on the head. He literally shook off the episode and continued running on his merry way. That dog may have subsequently developed seizures, but if the same thing had happened to a cat, he or she may not have survived long enough for them to become a problem.
The take home message? If your dog experiences head trauma, ask your veterinarian what you should do in the not at all unlikely event he should develop seizures in the coming days, weeks, or months. If it’s your cat that is injured, you probably have more pressing problems to worry about than seizures.
Dr. Jennifer Coates
Prevalence of seizures in cats after head trauma. Grohmann KS, Schmidt MJ, Moritz A, Kramer M. J Am Vet Med Assoc. 2012 Dec 1;241(11):1467-70.
Seizures following head trauma in dogs: 259 cases (1999-2009). Friedenberg SG, Butler AL, Wei L, Moore SA, Cooper ES. J Am Vet Med Assoc. 2012 Dec 1;241(11):1479-83.