April 06, 2018

Idiopathic Epilepsy and Cognitive Dysfunction in Dogs

In the first study of its kind, researchers examined the connection between idiopathic epilepsy and cognitive dysfunction in dogs.
By JoAnna Pendergrass, DVM
Epilepsy is a serious brain disorder that is characterized by recurrent seizures and, according to human studies, strongly associated with cognitive dysfunction. This dysfunction varies widely in severity and tends to be more severe with symptomatic epilepsy than idiopathic epilepsy (IE).

However, whether epilepsy-associated cognitive dysfunction is progressive (due to recurrent seizures), static (present from epilepsy onset), or the result of other comorbidities like dementia remains debatable.

In dogs, IE is the most common chronic neurologic disorder and typically begins between 6 months and 6 years of age. Its effect on canine cognition has not yet been researched. Canine cognitive dysfunction (CCD), on the other hand, has been widely researched and is characterized by various deficits, including learning and memory, in senior dogs.

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Geriatric disorders like CCD have become increasingly important in veterinary medicine. Because CCD and IE can negatively affect quality of life, particularly as comorbidities, a research team recently investigated cognitive impairments in dogs with IE. The results of their study, which was the first of its kind, were reported in PLoS ONE.

Data Collection
Using an online survey, the investigators collected data from the owners of over 4000 dogs. A short series of questions determined whether the dogs had IE; dogs without IE served as controls.

The canine cognitive dysfunction rating (CCDR) scale was used to measure the frequency and progression of cognitive deficits, with a score 50/80 or higher indicating CCD. Training history data were also collected to account for environmental effects on canine cognition.

Basic demographic data on all dogs was collected. For dogs with IE, information on seizure activity was obtained.

Survey Results
Of the 4051 dogs on which data were collected, 286 had IE. Compared with controls, dogs with IE were younger, heavier, and had less training.

CCD prevalence was highest at a much younger age for dogs with IE (4.1 to 6 years) than for controls (> 14 years), signifying a strong association between IE and age. Four major risk factors for CCD were identified:
  • IE
  • Older age
  • Less training
  • Lower body weight

Cognitive impairments (eg, “How often does your dog walk into walls or doors?”) were more frequent in dogs with IE and primarily reflected memory deficits. Interestingly, social impairments—a hallmark of classic CCD—were not more frequent in dogs with IE than in controls, suggesting a difference between IE-associated CCD and classic CCD.

Progression of cognitive impairments was not reported in dogs with IE, suggesting early progression and stabilization by the time of the survey, the investigators believed. Progression was reported in the control dogs, however, likely due to the natural aging process.

For the dogs with IE, the median CCDR score was approximately 35/80, with 11 dogs scoring 50 or higher. The median age for the first seizure was 32 months. Approximately 75% of the dogs had cluster seizures, and 40% experienced status epilepticus. Nearly 90% were on anti-epileptic drugs at the time of the survey, with variable changes in seizure frequency. The investigators identified several factors for increased CCDR scores in dogs with IE:
  • Status epilepticus
  • Higher seizure frequency
  • History of cluster seizures

Bringing It Together
The survey results indicate that IE-associated CCD may differ from classic CCD in terms of age of onset, nature, and progression, the researchers concluded. Stemming from these findings, future research includes identifying neuroprotective factors in dogs and conducting longitudinal studies to characterize cognitive impairment progression in dogs with IE.

 
Dr. Pendergrass received her doctor of veterinary medicine degree from the Virginia-Maryland College of Veterinary Medicine. Following veterinary school, she completed a postdoctoral fellowship at Emory University’s Yerkes National Primate Research Center. Dr. Pendergrass is the founder and owner of JPen Communications, a medical communications company.

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