QUARTERLY BEAT / DECEMBER 2025
DIFFERENTIALS I cannot stress the importance of coming up with a list of differentials for your seizure patients, because this will help guide your diagnostic recommendations. The International League Against Epilepsy publishes new etiologic classifications for epilepsy every couple of years and often the veterinary field will make modifications on our classification based on these changes. I don't worry so much about the classification, just use what works best for you to come up with a good list of differentials. For example, if you are used to using the DAMNIT-V scheme, below is a list of some differentials that you may want to consider for a feline patient with seizures. This is by no means an exhaustive list of causes of seizures.
Some key features that are commonly seen with seizure activity include:
Apprehensive behavior, pacing, agitation, seeking out the owners, hiding, etc.
Pre-ictal
Tonic-clonic: loss of consciousness, autonomic dysfunction, less than 2 minutes (can be longer but most seizures are 2 minutes or less), facial twitching Focal: Uni-lateral facial twitching, contracture of a forelimb, consciousness normally maintained Cats: Orofacial
Ictal
Confused/disoriented, blind, restless, hungry, thirsty, aggression, etc.
Post-ictal
DEGENERATIVE
Lysosomal storage diseases
Complete details of the seizures that I obtain from owners include the following information:
DEVELOPMENTAL
Hydrocephalus, lissencephaly, cortical dysplasia
ANOMALOUS
Epilepsy of unknown cause
• When seizure activity started • Total seizures • Seizure frequency • Description of seizure activity, time of day, associated with any exercise, etc. • Length of seizure • Pre-ictal phase
• Post-ictal phase • Toxin exposure • Behavior in between seizures • History of trauma • Anti-epileptic drugs (AEDs) currently being administered and any recent blood levels • Improvement of seizure activity with AEDs
Hepatic disease, renal disease, electrolyte abnormalities, hypoglycemia, hypoxia, mitochondrial encephalopathy
METABOLIC
NEOPLASTIC
Primary or secondary
NUTRITIONAL
Thiamine deficiency
Infectious (FIP, Cryptococcus, toxoplasmosis, etc.) vs non-infectious (meningoencephalitis of unknown etiology) feline limbic encephalitis-hippocampal necrosis complex
INFLAMMATORY
PHYSICAL AND NEUROLOGIC EVALUATION A complete physical and neurologic evaluation should be performed on every patient. If there are abnormal physical examination findings, then diagnostics based on those findings should be pursued. In regards to the neurologic evaluation, a cat is always going to be a cat and makes things a little tricky. Do the best you can, but it is highly unlikely that you will be performing a complete neurologic evaluation AND THAT’S OKAY! Special attention should be paid to any other signs of forebrain dysfunction (e.g., circling, head pressing, cortical blindness, conscious proprioception deficits). Many animals will have an abnormal neurologic evaluation in the post-ictal period. Normally if you have abnormal neurologic examination findings, it makes epilepsy of unknown cause less likely, but a lot of cats will have mentation changes, visual deficits, ataxia or paresis for hours or sometimes days after seizure activity. So don't necessarily give the cat a bad prognosis if they have neurologic deficits immediately after a seizure, but if the deficits remain after 1-2 days, or worsen, then other causes besides epilepsy of unknown cause need to be considered. One abnormal neurologic examination finding that wouldn’t be due to the post ictal state would be spinal hyperesthesia – if spinal hyperesthesia is present inflammatory disease of the nervous system should be high on your differential list. After you have completed your full evaluation, you will then neurolocalize your patient. If a patient is presenting for seizures, you know that the forebrain is involved. The importance of the neurologic evaluation is to be sure that other parts of the nervous system aren’t involved, in which case your neurolocalization would change from forebrain to multifocal. Based on where you neurolocalize your patient will then allow you to form an appropriate list of differentials.
TOXIC
Pesticides, lead, ethylene glycol, mycotoxins
TRAUMATIC
Traumatic brain injury, skull fractures
Cerebral vascular accidents (ischemic vs. hemorrhagic)
VASCULAR
DIAGNOSTICS Recommended diagnostics for the epileptic patient will largely depend on your differentials, but at a minimum these patients should be receiving complete blood cell counts, full chemistry profiles, urinalysis, and a liver function test (either bile acids or ammonia). From there, further testing that you may include would be thoracic and abdominal radiographs, abdominal ultrasound, brain MRI +/- cerebrospinal fluid analysis. It is important to stress that in our feline patients, a complete neurologic work-up, including a brain MRI and CSF evaluation, is recommended if indicated and safe to do so.
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