Specialty Spotlight – Seizures, A Complicated Neurologic Problem

Seizures, A Complicated Neurologic Problem
Todd Bishop, DVM, DACVIM (Neurology)

Seizures are one of the most common but also one of the most complicated neurologic problems we encounter in practice. In an effort to make these cases more manageable, I’ve created a diagnostic checklist to ensure that I am making the most informed clinical decisions possible for my patients. I hope that you find this scheme helpful in your practice.

Seizure management is like a jigsaw puzzle.  One never gets a clear picture of the outcome until all of the key pieces are in-place.  The key components to successful seizure management including: a thorough seizure history, general physical exam, neurologic assessment, routine screening lab work and anticonvulsant drug levels.  An informed clinical therapeutic decision cannot be made without each and every piece of this puzzle.

The medical history is probably the most important and most frequently overlooked component of seizure management. Details on seizure frequency, severity, duration and anticonvulsant side-effects are critically important to clinical decision making.   Below is a list of seizure questions I ask my clients:

  • When did the seizures first start (or at what age)?:
  • What do the seizures look like (severity)?:
  • Do you have a video of an episode?:
  • How often are they occurring (frequency)?:
  • How long do they last (duration)?:
  • Do they come in clusters (2 or more in 24 hours)?:
  • Does your pet ever experience continuous seizure activity lasting 5-10 minutes or longer without recovery (status epilepticus)?:
  • What happens immediately after a seizure (post-ictal phase)?:
  • How long does the post-ictal phase last?:
  • Are there any triggers or hints that a seizure may occur (aura)?:
  • What anticonvulsants have been tried and at what doses?:
  • How long have they been on these medications?:
  • Any recent dose changes?:
  • Any recent dietary changes?:
  • Has there been a change in drug supplier/manufacturer?:
  • When was the last dose given?:
  • Any side-effects of these medications?:

Perform a careful, systematic, general physical exam focusing on the organ systems that are the targets for anticonvulsant side effects including: skin, fur, eyes (sclera), mucocutaneous junctions, mucous membranes, lymph nodes, nail beds, foot pads, liver, gastrointestinal tract (stomach and pancreas), joints.

Perform a complete neurologic exam focusing in on the patient’s mentation, cranial nerves, gait and posture, postural reactions, spinal reflexes, muscle size and tone.  Pay particular attention to the patient’s mentation and pelvic limb strength/coordination as these are two areas that are particularly affected by anticonvulsants.

Assess routine screening lab work including: a complete blood cell count, biochemistry profile and thyroid level, if appropriate.  Unless it is an emergency situation, I recommend sending these samples to an outside reference laboratory.  They have better quality controls and more comprehensive panels.  Look for signs of bone marrow suppression on the CBC (low RBC, WBC and platelet counts) and hepatic dysfunction on the chemistry profile (low albumin, BUN, glucose, cholesterol and high bilirubin).  I do not get overly concerned by mild to moderate increases in hepatocellular transaminase values, particularly alkaline phosphatase (ALP) which is induced in all patients receiving phenobarbital. Remember, phenobarbital can falsely lower the total T4.

Evaluate anticonvulsant drug levels including: Phenobarbital, potassium bromide +/- Zonisamide.  I do not perform Levetiracetam, Gabapentin or Pregabalin levels as we do not have a good handle on therapeutic ranges for these drug in veterinary medicine.  It is of the utmost importance that you interpret these therapeutic levels carefully.  Some patients with refractory seizures require doses that push the serum drug levels into the high therapeutic or even low toxic range. It is not enough to say that a drug is in the therapeutic range. Always treat the patient not the lab work.

Finally, always weigh a client’s desire for better seizure control against the side-effects of these drugs on the patient. Never trade marginally better seizure control for markedly worse day to day quality life. Try to maximize monotherapy before adding a second drug. When a second drug becomes necessary ADD it to the first drug, don’t REPLACE the first drug (ask me some day about my firetruck analogy).

I hope that these tips help you better manage your challenging seizure cases. Please feel free to reach out to Dr. Krzykowski or me for advice or information about referral.

Todd M. Bishop, DVM, DACVIM (Neurology)