Idiopathic Epilepsy in Dogs
Epilepsy in Dogs
Seizures, the most common neurologic disorder diagnosed in dogs,1 are characteristic of epilepsy, which is defined as recurrent seizures over a period of time.2 Seizures are clinical manifestations of excess and hypersynchronous electrical activity in the cerebral cortex. The multiple causes of epilepsy include brain tumors, degenerative brain disease, and other brain disorders. Epilepsy affects up to 0.75% of the canine population.3
The most common type of epilepsy is idiopathic, or primary, epilepsy. In idiopathic epilepsy (IE), the underlying cause of recurrent seizures is unknown or no identifiable brain disease can be found.2
Certain breeds are predisposed to IE, which, based on epidemiologic studies, is thought to have a genetic basis.4
Breeds Predisposed to Epilepsy1
- Belgian shepherd dog
- Bernese mountain dog
- Border collie
- Cocker spaniel
- English springer spaniel
- Finnish spitz
- German shepherd dog
- Golden retriever
- Irish setter
- Irish wolfhound
- Labrador retriever
- Lagotto Romagnolo
- Miniature schnauzer
- Nova Scotia duck tolling retriever
- Saint Bernard
- Siberian husky
- Standard poodle
Most IE patients have their first seizure between 1 and 5 years of age, but patients can be older or younger at onset. In one study, 75% of dogs with recurrent seizures at less than 1 year of age (ie, juvenile epilepsy) had no identifiable brain disease.1 Another study found no apparent cause for seizures in 35% of dogs with seizure onset at more than 5 years of age (ie, late-onset epilepsy).1
Seizures are described as generalized or focal. Generalized seizures reflect involvement of both hemispheres of the cerebral cortex, whereas focal seizures indicate abnormal activity in one part of a cerebral hemisphere.4 Most IE patients display generalized tonic-clonic seizures. During the tonic phase, the patient loses consciousness and falls to one side in opisthotonus with every limb rigid and extended. The clonic phase that follows consists of limb paddling/jerking and chewing movements.1 Seizures typically have 4 stages: prodrome, preictal, ictus, and postictal.5 (See Table 1.)
|Preictal||Beginning of the seizure|
|Ictus||The visible seizure, often characterized by tonic and clonic phases|
|Postictal||Period following the seizure|
IE is diagnosed by ruling out all other possible causes of seizures by having a normal neurologic examination, normal lab tests (eg, CBC, serum chemistry, bile acids, thyroid function), a normal brain MRI, and normal spinal fluid analysis.
Treatment is specific to the patient and based on the veterinarian’s familiarity with and access to antiepileptic drugs (AEDs). A recent consensus statement recommends beginning AED therapy6:
- When the patient has more than 2 seizures every 6 months
- When cluster seizures are present
- After any episode of status epilepticus
- When the postictal period is prolonged or unusual
The goal of AED therapy is to significantly decrease seizure frequency and severity while minimizing medication side effects. A drug that decreases seizure frequency by at least 50% is considered efficacious. Treatment may include first-line AEDs only or first-line AEDs in conjunction with other anticonvulsant drugs. (See Table 2.)
|Drug||First-Line Medication||Dose||Side Effects||Therapeutic Monitoring||Therapeutic Range|
|Bromide||Yes||Loading dose: 125 mg/kg/day PO for 5 days Maintenance dose: 35 mg/kg/day PO||Polyuria, polydipsia, polyphagia, sedation, ataxia, pancreatitis, gastritis (vomiting)||Initial: CBC, serum chemistry, serum drug concentrations 2 weeks after loading Maintenance: Every 6-12 months||1-3 mg/mL|
|Gabapentin||No||10 mg/kg PO q8h1||Sedation, ataxia||None|
|Levetiracetam||Yes||20-30 mg/kg PO q8h (regular release) 20-30 mg/kg PO q12h (extended release)||Sedation, ataxia (typically none to mild)||None|
|Phenobarbital||Yes||2-3 mg/kg PO q12h||Polyuria, polydipsia, polyphagia, sedation, ataxia, hepatopathy, p450 enzyme induction, bone marrow hypoplasia (rare)||Initial: CBC, serum chemistry, serum drug concentrations in 2-3 weeks Maintenance: Every 6-12 months||10-40 µg/mL This is lab dependent (ie, Antech). Dewey quotes a range of 20-35 µg/mL.1|
|Pregabalin||No||2-4 mg/kg PO q8-12h||Sedation, ataxia||None|
|Zonisamide||Yes||10-20 mg/kg PO q12h (per the author’s experience)||Decreased appetite, sedation, idiosyncratic hepatic necrosis (rare)||Initial: CBC, serum chemistry in 2-3 weeks Maintenance: Every 6-12 months|
If seizure frequency is unacceptable (ie, >1 per month), additional treatment options are limited to increasing current medication dosages or adding a different AED. Nonmedical therapies (eg, diet changes, acupuncture, vagal nerve stimulators) have also been investigated.1 While the author does not discourage any strategy to help improve seizure control, these ancillary measures have not been studied extensively, making it difficult to advise a patient’s owner on their efficacy. Clients can be instructed to provide supportive care by remaining calm when seizures are occurring to limit injury to the patient and by creating a quiet, dimly lit environment for the recovery.
IE is not curable, and management requires a long-term commitment from the patient’s owner. Approximately 25% of patients with IE will be refractory to one or more anticonvulsant medications.5 Comorbidities (eg, anxiety, hyperactivity, behavior changes, medication side effects) contribute to a patient’s decreased quality of life. Dogs with epilepsy have been reported to have shorter lifespans because, as a result of emotional stress to pet owners, treatment cost, and/or patient quality-of-life concerns, many clients choose euthanasia over long-term treatment.7
1Ensure all team members know the signs of the 4 stages of a seizure and can communicate them clearly to clients.
2Make sure clients know what to expect by carefully explaining that idiopathic epilepsy is not curable and caring for their pet will require a long-term commitment.
A Personal Perspective on Epilepsy
What does a seizure feel like? Grand mal seizures don’t feel like anything. How do I know? Because I’ve had 2. The first led to my original diagnosis, and the second occurred when I switched medications to have children, so I speak from personal experience when I discuss a pet’s seizure disorder with a client.
Each time I had a seizure, I only realized something was wrong as I came to, surrounded by EMTs. I felt really groggy, but I didn’t hurt, and I wasn’t scared. The seizures are simply blank spots in my mind, as if I were asleep and woke up from a too-short nap.
Experiencing the seizure is the easy part. What comes afterward is hard.
It’s hard seeing the impact of my seizure on the people who watched it. It’s hard having to adjust my medication and suffer with grogginess, proprioceptive deficits, or allergic reactions. It’s hard knowing my condition could randomly kill me. Fortunately, my epilepsy is well controlled.
I don’t speak for every epileptic, and other seizure disorders are different—partial seizures in particular. However, my personal perspective helps when I talk to clients. Here is what I tell them.
- As scary as a grand mal seizure looks, your pet is not in pain.
- It is normal to worry about your pet. This will help you watch closely for seizures and medication side effects. However, you shouldn’t let your worry stop your pet from enjoying his or her life.
- While we aim to minimize and decrease seizure severity and frequency, our other goal is to give your pet a good quality of life between seizures.
At the end of the day, veterinary epileptic patients need the same things I cherish most—friends, family, and a great team to help keep them safe, healthy, and loved.
- Thomas WB, Dewey CW. Seizures and narcolepsy. In: Dewey CW, da Costa RC, eds. Practical Guide to Canine and Feline Neurology. 3rd ed. Ames, IA: Wiley Blackwell; 2016:249-267.
- Mariani CL. Terminology and classification of seizures and epilepsy in veterinary patients. Top Companion Anim Med. 2013;28(2):34-41.
- Packer RM, Volk HA. Epilepsy beyond seizures: a review of the impact of epilepsy and its comorbidities on health-related quality of life in dogs. Vet Rec. 2015;177(12):306-315.
- Berendt M, Farquhar RG, Mandigers PJ, et al. International veterinary epilepsy task force consensus report on epilepsy definition, classification and terminology in companion animals. BMC Vet Res. 2015;11(1):182.
- Thomas WB. Idiopathic epilepsy in dogs and cats. Vet Clin North Am Small Anim Pract. 2010;40(1):161-179.
- Podell M, Volk HA, Berendt M, et al. 2015 ACVIM small animal consensus statement on seizure management in dogs. J Vet Intern Med. 2016;30(2):477-490.
- Berendt M, Gredal H, Ersbøll AK, Alving J. Premature death, risk factors, and life patterns in dogs with epilepsy. J Vet Intern Med. 2007;21(4):754-759.
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