Cardiac Changes with Idiopathic Epilepsy?

A recent study from Brazil (www.veterinaryworld.org/Vol.17/February-2024/13.pdf) evaluated 10 dogs diagnosed with Tier I level idiopathic epilepsy to determine if changes to the EKG were present. The rationale for doing this study was initiated by the human epileptic syndrome of "sudden death in epilepsy, or SUDEP". SUDEP is a devastating syndrome wherein human patients are found dead after recovery from a recent seizure. This is most traumatic for the parents of pediatric epileptics who may help their child through a seizure, see that they are recovered and then find them deceased a short while later without any signs of additional seizures. The cause of SUDEP is debated however a cardiovascular cause appears most likely. This syndrome is rarely identified and poorly published in veterinary medicine. 

During a seizure, a tremendous release of catecholamines occurs which may stimulate hypertension, as well as intoxicate the cardiac muscle causing poor relaxation and cardiomyopathy. The study reported findings in 10 dogs with epilepsy and compared them to 11 dogs without epilepsy who were apparently healthy on laboratory testing, physical and neurologic examination and without a seizure history. 

Results

The QRS complex was significantly longer in dogs with epilepsy compared to the control group suggesting left ventricular enlargement or left bundle branch block. Additionally, the QT interval was prolonged, and this was attributed to the below reference range ionized calcium concentrations in the epileptic dogs. Interestingly, the control dogs also had lower ionized calcium concentrations so one might question the validity of this test. What do these cardiac changes mean for us? It means that even "well controlled, healthy" epileptic dogs may have occult cardiac damage. Use caution when providing anesthesia to this group and perhaps reach for a preoperative EKG for this population even if their breed or age wouldn't otherwise spur you to do so. Lastly, I found it interesting that the serum glucose concentration was significantly higher in dogs with idiopathic epilepsy compared to the control group. This likely harkens back to the high sympathetic response and catecholamine release mentioned above but another idea crosses my mind as well. Many internet sites still recommend giving glucose or honey to a pet after a seizure, even without evidence of hypoglycemia. Ice cream, popsicles, and honey are frequent additions to post-ictal care in many of our patients. If given prior to the laboratory samples, it could falsely increase the serum glucose concentration. What's the take away here? Don't rule out hypoglycemia as a seizure etiology on a single blood sample. Consider a second one 4-6 hours later, during hospitalization, and note if the glucose drops below the therapeutic range. (Oh, and make sure your clients are advised against giving sugar products postictal. No one needs a sugar rush when you're on a catecholamine rush!)

Thanks for reading! This little article crossed my radar this week and I thought it was good enough to share with all of you! I hope you have a great first full week of Spring (anyone else looking at snow on their forecast??) and I look forward to working with you soon.

What If We Could See a Seizure Focus?

Idiopathic epilepsy is something we all see on a regular basis. However, when we diagnose something by exclusion, I often wonder what we are missing. Currently idiopathic epilepsy is diagnosed if dogs meet the following criteria:

Tier I

• Normal neurologic examination

• Normal CBC, serum biochemistry and bile acid test

Tier II

• All of the above PLUS

• Normal brain MRI

• Normal CSF analysis results

(There is a Tier III, but it is rarely used.)

What if we could actually see a seizure focus?

This is the stuff of science-fiction, folks! A recent article in JVIM (https://doi.org/10.1111/jvim.16270) utilized an MRI technique that has been used in human epilepsy to try to visualize a seizure focus in dogs with idiopathic epilepsy. MRI works by affecting magnetic fields in the brain. With this new technique, neuronal currents are mapped with a specific oscillating magnetic field. This has been shown to be an effective mapping technique for humans with idiopathic epilepsy. The researchers applied the technique to a group of control dogs (those without seizures) and dogs diagnosed with idiopathic epilepsy with Tier II level confidence.

Results

There were three different frequencies used in the protocol however the authors combined the results from the different frequencies and found that 11 of 12 dogs with idiopathic epilepsy had a bright spot identified in their brain, with this technique. Even cooler, 4 of the 5 control dogs did NOT have any bright spots visualized in their brains. Perfect? No. Super cool? Yes!

Take Home Message

What does this mean for you and me? It means that as we test this new protocol a bit more we are one step closer to "seeing" the seizure focus in the brain. Who cares, you may ask? We all should!! If we can see it, we can remove it surgically (maybe), target it with radiation (already being done but this will improve accuracy), or start to identify different "types" of idiopathic epilepsy and assess how our drug protocols are affecting animals with specific forms of epilepsy. All of this allows us to target epilepsy much more specifically, and ultimately improve quality of life.

Thanks for reading! Hopefully you can use this new information to give your clients hope, when faced with a diagnosis of canine idiopathic epilepsy. Researchers (vets!) are working tirelessly to find a way to make life better for owners, and their pets with epilepsy.

Have a great week and be safe!

How to Diagnose Idiopathic Epilepsy in the Exam Room

In 2015, the International Veterinary Epilepsy Task Force (IVETF) published a list of criteria to diagnose idiopathic epilepsy in dogs (not cats). The IVETF consisted of a group of veterinary neurologists, neuropathologists, and epileptologists. If you wish to see all of the resulting publications, just let me know! (They are available open access.)

The IVETF listed several ways to make a diagnosis of idiopathic epilepsy, starting with the lowest level of confidence (Tier I) and rising to the top with the most confidence in the diagnosis (Tier III). When using this information in your daily practice, consider writing "diagnosis: idiopathic epilepsy with Tier 1 confidence" in the medical record when a patient meets the criteria for a Tier I diagnosis of idiopathic epilepsy.

Please note, idiopathic epilepsy does not mean, any seizure disorder. Idiopathic epilepsy is a specific disease, that causes repeated seizures. ANY animal with repeated seizures can be diagnosed with epilepsy, but idiopathic epilepsy is ONE form of epilepsy. Make sense?

Tier I:

A dog must have:

• A history of 2 or more seizures at least 24 hours apart

• Have the age at onset between 6 months and 6 years

• Demonstrate a normal inter-ictal physical and neurologic examination

• A normal CBC, and serum biochemistry (the IVETF lists what they consider to be standard in a serum biochemistry analysis. Let me know if you want/need this list.)

• A normal fasting bile acids and/or ammonia

• A normal urinalysis

• A familial history of IE is supportive, but not required

Tier II:

To diagnose idiopathic epilepsy with Tier II level confidence a dog must have:

• All of Tier I plus...

• A normal brain MRI

• A normal CSF analysis

• Normal fasting and post-prandial bile acids

Tier III:

• All of Tier II plus...
  

• Identification of ictal or inter-ictal EEG abnormalities suggestive of seizure disorders.

So, if a patient meets Tier I level confidence, when should MRI be performed?

• Anytime a client wishes to confirm a diagnosis of intracranial disease. (This includes idiopathic epilepsy which is diagnosed by exclusion of other causes)

• If a dog has a seizure onset of < 1 year or > 7 years of age (according to the IVETF)

• If neurologic abnormalities reflective of the prosencephalon/forebrain are identified on the neurologic examination regardless of age, breed or a familial history of seizures.

In summary, it is always worthwhile to inform clients of the option of MRI when their dog (or cat) has seizures however, if the Tier I criteria are met and MRI has a high likelihood of normal results, it is very reasonable to skip this test and begin treatment for idiopathic epilepsy.

I try to remember that MRI abnormalities were identified in 22% of dogs with a normal neurologic exam and 90% of dogs with an abnormal neurologic examination in one study.

What about CSF analysis, you ask? I'm glad you asked! Some dogs with meningitis will have a normal MRI, therefore an MRI PLUS CSF tap is often my recommendation to ensure we don't overlook those patients inappropriately by just performing an MRI.

What about cats? The IVETF recommendations do not specifically apply to cats however many neurologists, including me, extrapolate this information to cats in practice. My fingers and toes are crossed for science driven cat-specific recommendations in the near future.

Have a great week! As always stay safe, and let me know how I can help you, help your patients, with neurologic disease.

Prevalence of Idiopathic Epilepsy in Dogs

Idiopathic Epilepsy Update!

A recent article out of the Vet Record by Dr. Rachel Hall and colleagues outlines the prevalence of idiopathic epilepsy and structural epilepsy in dogs.* I found this a very interesting read, packed with useful information so I thought I'd pass along a bit (get it?) of it to you!

Study Design and Points Worth Noting

• This is a retrospective study based out of the UK. 

• 900 cases with MRI, a neurologic examination and medical record history were included. (wow!)

• Structural epilepsy is defined as a seizure disorder secondary to an identifiable structural cause. Examples include neoplasia, meningoencephalitis, hydrocephalus, etc.

• Idiopathic epilepsy is defined as the lack of identification of a structural abnormality in a pet with 2 or more discrete seizures. 

• Small (< 10 kg), medium (10-20 kg) and large breed (>20 kg) dogs were represented in approximately the same percentage in this study.

Results of Interest (there are a lot of interesting results in this study!)

• About 50% of the dogs were between 6 months and 6 years old, and 50% were > 6 years old. 

• About half of the dogs had structural epilepsy based on abnormal MRI findings

• The other half of dogs had no significant findings on MRI and the majority were classified as having idiopathic epilepsy. (The others had toxin and metabolic disease diagnosed).

  • Prevalence of idiopathic epilepsy in dogs in the UK? 50%!

Okay, fine (you might think) how does knowing the prevalence of idiopathic epilepsy in dogs in the UK help me?

I'm glad you asked...

• Idiopathic epilepsy was the leading diagnosis for dogs between 7 months and 6 years old. Inflammatory brain disease was second.

  • Take away point? Meningoencephalitis is NOT rare! Oh, and idiopathic epilepsy is most common in the group of dogs we thought it would be most common.  

• Idiopathic epilepsy was also the leading single diagnosis (34%) for dogs over 6 years of age. HOWEVER when they combined all types of neoplasia together into one group they found 43% of dogs over 6 years of age had neoplasia making it the leading singe diagnosis in this group.

  • Take away point? Read that sentence above again! I considered making this TidBit Tuesday a one line update because it's so critical to make sure we don't forget that "old" dogs can actually have idiopathic epilepsy!

  • Also, dogs over 6 years of age had structural epilepsy more often than idiopathic epilepsy if all causes for structural epilepsy were combined. (Not surprising, I know.)

What do you do with this information?

Do a neuro exam on every patient with a seizure history!

• If the exam is NORMAL, include idiopathic epilepsy on the differential diagnoses list, regardless of age. 

• If the exam is ABNORMAL, include causes for structural epilepsy on your differential diagnoses list, regardless of age.

Thanks for reading - I hope you have a great week!

Reminder! Upcoming Webinar "The Neurologic Exam for the Busy Vet" on Wednesday May 27th 12-1pm and repeated 7-8 pm.
Check out my website at www.barnesveterinaryservices.com for details and registration.

* Hall R, et al. Estimation of the prevalence of idiopathic epilepsy and structural epilepsy in a general population of 900 dogs undergoing MRI for epileptic seizures. Vet Record 2020.