Temporal lobe epilepsy (TLE) is a specific form of epilepsy that has specific pathology. As you might imagine, the pathology is found in the temporal lobe and consists of given cellular degeneration, loss of neurons and sprouting of mossy fibers (what a great term for a fiber). Clinically, TLE often shows facial automatisms (focal seizures) and is commonly drug resistant. As a result, patients with TLE may under go radiation or surgical intervention to manage their epilepsy. A group from the University of Wisconsin Neurology service recently investigated a cohort of 7 dogs with clinical seizures suggestive of TLE to determine if the same pathology was represented in dogs.

Materials and Methods

Seven dogs with focal facial seizures who were euthanized due to progressive disease were included.

Key neuropathologic findings

· No significant hilar neuron loss was identified in any dog. Cell counts fell within a relatively narrow range, and no hippocampus showed neuron numbers >2 SD below the group mean.

· No hippocampal asymmetry was detected in neuronal counts between left and right hippocampi.

· Mossy fiber sprouting was mild in all dogs (median score ~1.1/5), with no cases showing extensive sprouting typical of TLE.

· No asymmetry in mossy fiber sprouting was found between hippocampi.

· Overall, none of the dogs met human neuropathologic criteria for TLE, despite having focal seizure semiology.

What does this mean?

These findings indicate that focal seizures in dogs with idiopathic epilepsy are not necessarily associated with TLE-like hippocampal pathology, contrasting with humans. The mild hippocampal changes observed may reflect seizure-related or age-related alterations rather than a distinct epileptogenic lesion. Importantly, previously reported MRI hippocampal asymmetry in some epileptic dogs may be a consequence of focal seizure activity, not evidence of true TLE. This data does not support pursuit of radiation therapy or surgery in dogs with resistant epilepsy, however there may be specific individual differences that warrant considering these treatments on a case-by-case basis.

I thought this article was worth discussing even though the results were negative. Maybe because the results were negative? We always think we could or should be doing more for some pets who are suffering from refractory seizures – and we should keep trying – but this study did not support similarities between human TLE and canine focal seizures. Therefore, without similar pathology, we cannot pursue similar treatments.

Hope you have survived the January vortex and are beginning to get out and enjoy all that winter has to offer in Wisconsin (or wherever you live!). If you enjoy reading the TidBits, please tell associates, new graduates and your veterinary friends. Thanks for reading. I look forward to seeing you soon.

Reference: https://avmajournals.avma.org/view/journals/ajvr/aop/ajvr.25.07.0260/ajvr.25.07.0260.xml

Use of CBD Oil for Refractory Epileptic Dogs

It's baaaack! At the ACVIM conference a few weeks ago I had the pleasure of listening to researchers from Colorado State University present data from a recent double blinded, placebo controlled prospective study evaluating CBD oil in resistant epileptic dogs.

How the Study Worked

51 client owned dogs, taking at least 1 ACD (anticonvulsant drug) and continuing to have 2 or more seizures every month, were included. Resistant epileptics are already the hardest subset to manage so this was a really tough crowd for the researchers to target. The dogs were given either placebo or CBD oil for 3 months and then switched and given the other compound for 3 months. Initially, they dosed at 2.5 mg/kg PO q12h but no effect was noted so after 12 dogs the dose was increased to 4.5 mg/kg PO q12h.

Key Points

ALP and ALT were elevated in this study. This is the first study to document elevated ALT during CBD administration in dogs. The researchers aren't sure why this happened but hepatocellular damage of some sort was suspected. Bile acids were normal in all dogs except 2.
No significant difference in response (response = a > 50% reduction in seizures) was noted between the placebo and CBD administrations group.
Total number of seizures/month and seizure days/month was reduced in the CBD group compared to the placebo group BUT over all seizures went UP with both groups

Should we use CBD to manage seizures for resistant epilepsy?

Sorry, not based on this study. It's not compelling enough to suggest that we should be using this drug PLUS it showed evidence of liver enzyme changes that could be concerning AND phenobarbital serum concentration went by 11% when the dogs were on CBD. That said, they targeted resistant epileptic dogs so could this be effective in "easier" to control dogs? Maybe. Could this increased phenobarbital concentration mean that we could lower the dose of phenobarbital in these pets? Maybe. Do we need to check out different doses? Maybe - but at least with this question I am cautious because of the new elevation of ALT at this higher dose. Can we safely increase the CBD dose? Unknown.

This is a good step forward but alas, we still don't have enough compelling evidence to say CBD should be a part of seizure therapy and at what dose.

Keep up the good work managing epileptic dogs! I'm available if you have questions about a case or need a second opinion. Have a great week!

Comparing Dog to Human Temporal Lobe Epilepsy

CBD Treatment for Resistant Epilepsy in Dogs