Watching your dog have a seizure can be a terrifying experience. The sudden collapse, involuntary movements, and potential loss of consciousness are deeply distressing, especially if it’s the first time. A prolonged seizure is a medical emergency. If you’re reading this, it’s likely your dog has experienced some form of involuntary fit, and you’re seeking answers about what it means and how to prevent future episodes. Let’s explore the essential information you need to know about seizures in dogs.
What is a Seizure and How Do You Recognize Them?
A seizure is caused by abnormal, excessive electrical activity in the brain’s cerebral cortex. This electrical surge begins in a specific area called the seizure focus and spreads through a process known as kindling. While classic seizures involve loss of consciousness, collapse, initial stiffness followed by paddling or struggling, seizures can manifest in many ways. Any unusual, involuntary behavior could potentially be a seizure. Seizures are categorized into several types:
Generalized (Grand Mal) Seizures
This is the most commonly recognized type of seizure in dogs. Generalized seizures involve the entire body. Your dog may become stiff and exhibit rhythmic stiffness and contraction cycles (tonic-clonic action). Loss of consciousness is typical, and your dog might urinate or defecate during the seizure.
Focal Seizures (Partial Motor Seizures)
Focal seizures affect only a specific part of the body, resulting in involuntary activity in that area. Consciousness may or may not be impaired. A classic example is the “chewing gum” fit sometimes seen with canine distemper, but it can also occur in other seizure disorders.
Psychomotor Seizures
Psychomotor seizures are a type of focal seizure that manifests more as abnormal behavior than a physical convulsion. Your dog’s consciousness is altered during these seizures, and they may appear to be hallucinating or in a confused state. Psychomotor seizures can range from episodes of rage or aggression, where your dog doesn’t recognize familiar people, to brief periods of disorientation or “spacing out.” “Fly-biting,” where a dog snaps at imaginary flies, is an example of a psychomotor seizure.
Distinguishing Seizures from Fainting
It can be challenging to differentiate seizures (neurological events) from fainting spells (cardiovascular events). True seizures are often preceded by an aura, a subtle change in behavior or feeling that the animal experiences before the seizure. However, since dogs can’t communicate these sensations, auras usually go unnoticed. Seizures are typically followed by a post-ictal period, where the dog appears disoriented, and may even seem blind. This post-ictal phase can last from a few minutes to several hours. In contrast, dogs that faint usually recover quickly, often within seconds, and don’t exhibit post-episode disorientation.
Post-ictal disorientation is a key indicator of a seizure.
Alt text: Veterinarians conducting neurological exam on a yellow Labrador, overlayed with a brain graphic to illustrate canine seizure diagnosis.
Causes of Seizures and Diagnosis in Dogs
Seizures in dogs can stem from a wide range of causes, including toxins, brain tumors, genetic predispositions like epilepsy, infections, and even brain scarring from past injuries. Seizures caused by metabolic issues or toxins, where the brain itself is normal, are termed reactive seizures. Seizures resulting from identifiable brain abnormalities are called structural seizures. When no underlying cause can be determined, the seizures are classified as primary seizures, and the dog is diagnosed with epilepsy.
Age plays a significant role in identifying the likely cause of seizures in dogs. Certain age groups are more prone to specific causes, making certain diagnostic tests more relevant depending on the dog’s age. Here’s a breakdown of age-related considerations:
- Reactive Seizures: Seizures due to metabolic problems or toxins (brain is structurally normal).
- Secondary Seizures (Structural Seizures): Seizures caused by a identifiable brain abnormality.
- Primary Seizures (Epilepsy): Seizures with no identifiable underlying cause.
Dogs Less Than Six Months Old
In puppies and young dogs under six months, brain infections are a primary cause of seizures. Infectious diseases like canine distemper or parasitic infections such as Toxoplasma or Neospora are common culprits. Diagnosing infections often involves analyzing cerebrospinal fluid (CSF), obtained through a spinal tap under anesthesia. PCR technology is now available to detect the DNA of infectious organisms in CSF, such as bacteria, fungi, and other pathogens. Less invasive tests may also be recommended depending on the suspected infection.
Dogs Between Six Months and Six Years Old
Genetic epilepsy, also known as primary epilepsy, is the most frequent cause of seizures in dogs within this age range, especially in purebred dogs. Epilepsy is diagnosed when other causes of seizures are ruled out, there are no neurological abnormalities between seizures, and the first seizures occur during this age frame. Typically, basic bloodwork is performed to exclude metabolic causes. More advanced and costly tests like brain imaging are often not immediately pursued because the presentation is often consistent with epilepsy.
Certain breeds have a higher predisposition to epilepsy. Schnauzers, Basset Hounds, Collies, and Cocker Spaniels are two to three times more likely to develop epilepsy compared to other breeds. Labrador Retrievers and Golden Retrievers are also predisposed, but their seizures tend to start later, closer to five years of age.
Dogs More Than Five Years Old
In older dogs, brain tumors are a more common cause of seizures. Meningiomas, tumors growing from the membranes surrounding the brain, are among the most frequent types. If your older dog starts having seizures, consult your veterinarian about diagnostic and treatment options. Tumors may be surgically removable or treatable with radiation, particularly if detected early. CT scans or MRIs are often the next diagnostic step, and referral to a specialist may be necessary for these imaging procedures. If surgery is not feasible, corticosteroids can be used to reduce brain swelling. Anticonvulsant medications, as discussed below, are also often needed to manage seizures.
When to Start Seizure Treatment in Dogs
The American College of Veterinary Internal Medicine (ACVIM) published a consensus statement in 2016 providing guidelines on when to initiate medication to manage seizures in dogs. Treatment is generally recommended if your dog experiences any of the following:
- Cluster seizures: More than three seizures within a 24-hour period.
- Frequent seizures: Two or more isolated seizures within a 6-month period.
- Status epilepticus: A seizure lasting five minutes or longer.
- Severe seizures or post-ictal periods: If the seizures or the disorientation following seizures are particularly intense.
- Structural brain lesion: If a CT scan, MRI, or even radiographs reveal a visible lesion in the brain.
- History of brain injury or trauma.
- Breed predisposition and seizure risk: Certain breeds, including German Shepherds, Border Collies, Australian Shepherds, Golden Retrievers, Irish Setters, and Saint Bernards, are known for being more challenging to manage seizures in. In these breeds, it’s often advisable to start medication after the first seizure, as each subsequent seizure can make future control more difficult. The more seizures a dog experiences, the harder it can be to achieve effective long-term control.
Treatment Options: Medications for Dog Seizures
Currently, there are four primary medications used to control seizures in dogs in the United States: phenobarbital, potassium bromide, levetiracetam, and zonisamide. If one medication isn’t sufficient, combinations of two or even three may be used. The ideal first-line anticonvulsant is effective, affordable, easy to administer, and has minimal side effects. Phenobarbital and potassium bromide are often the initial choices, but let’s review the advantages and disadvantages of each.
Phenobarbital
Phenobarbital has been a cornerstone of canine seizure management for decades. It’s effective, relatively inexpensive, and typically administered twice daily, which is convenient for many owners. Studies show that approximately 31% of dogs starting phenobarbital become seizure-free, and about 80% experience a greater than 50% reduction in seizure frequency. However, 20-30% of dogs on phenobarbital may need a second anti-seizure medication for adequate control.
The main drawback of phenobarbital is its potential for side effects. Regular blood level monitoring is necessary, as high levels can lead to liver disease. The phenobarbital dosage needs to be adjusted to maintain blood levels within a safe therapeutic range. This monitoring adds to the overall cost of treatment.
Common side effects include sedation, which is usually temporary during the first week or two as the dog adjusts to the medication. Increased hunger and thirst are also common side effects and can be bothersome. Phenobarbital can also cause changes in liver function tests, which need to be recognized as drug-related effects. Because phenobarbital is metabolized by the liver, good liver function is essential, and it can also interact with other medications metabolized by the liver.
Potassium Bromide
Potassium bromide was used to treat human seizures nearly a century ago but was largely replaced by phenobarbital. However, in dogs, potassium bromide may be a superior seizure medication compared to phenobarbital. Studies indicate that around 52% of dogs starting potassium bromide become seizure-free, and approximately 70% achieve a greater than 50% reduction in seizure frequency.
A significant side effect of potassium bromide is the risk of pancreatitis. It should generally be avoided in dogs with a history of pancreatitis. Potassium bromide takes several months to reach a stable blood level, which can leave dogs vulnerable to seizures during this initial period. Like phenobarbital, potassium bromide requires monitoring blood levels, and sedation is a potential side effect.
Levetiracetam (Keppra®)
Levetiracetam is a popular choice for dogs with refractory epilepsy (seizures that are difficult to control with other medications) because it’s generally effective and has a low risk of side effects. It appears to be most effective when used in combination with other seizure medications, but many dogs do well with levetiracetam as a single agent. No routine monitoring tests are needed, and an extended-release formulation allows for twice-daily dosing.
Zonisamide (Zonegran®)
Zonisamide is a sulfa-based anti-seizure medication that is becoming increasingly popular as a first-line treatment option, and can also be used to supplement traditional therapies. As a sulfa drug, it carries the potential for sulfa-related side effects, primarily dry eye (reduced tear production) and, less commonly, immune-mediated reactions. Zonisamide is usually given twice daily in dogs, but its longer duration of action in cats may allow for once-daily administration.
Dietary Support for Seizure Control
In 2017, a veterinary therapeutic diet specifically formulated to support seizure management was introduced. This diet utilizes medium-chain triglycerides (MCTs) as a primary fat source. Fats are classified as short, medium, and long-chain based on their carbon chain length. MCTs have been shown to have direct anti-seizure effects. Dogs that didn’t achieve full seizure control with medication alone showed improved seizure control or even complete seizure freedom after a three-month trial of this MCT-enriched diet. It’s important to note that this diet is intended to complement, not replace, anti-seizure medications.
Managing Seizures at Home: When is it an Emergency?
Occasional Breakthrough Seizure
Even with medication, some dogs may experience occasional breakthrough seizures. While upsetting to witness, a single breakthrough seizure is usually not a cause for serious alarm. In most cases, giving an extra dose of your dog’s regular oral anti-seizure medication is sufficient, and the episode can be considered resolved. However, you should inform your veterinarian about the breakthrough seizure so they can evaluate the medication regimen and adjust it if needed to prevent future breakthrough seizures.
Second Seizure Within 24 Hours
If your dog has a second seizure within 24 hours of the first, it’s advisable to take them to your veterinarian’s office for a “seizure watch.” This allows your dog to be monitored and receive medication to stop any further seizures. It also provides an opportunity to re-evaluate the current medication plan.
Emergency Home Care: Rectal Diazepam
Since emergency veterinary care can be costly, talk to your vet about having rectal diazepam (Valium®) on hand for home use as first aid to manage cluster seizures until you can reach your regular veterinarian. Rectal diazepam is administered using a special syringe. Compounding pharmacies also offer diazepam rectal suppositories, which may be easier to use, although absorption rates can vary, and neurologists often prefer the injectable product. Rectal diazepam administration has been used effectively in children with epilepsy for many years, and the technique translates well to veterinary patients. Nasal diazepam administration is also possible, but there’s a higher risk of being bitten.
Safety Precautions During a Seizure
It’s crucial to prioritize your safety when your dog is having a seizure. Involuntary jaw movements can cause bites, and during the post-ictal disorientation phase, your dog may not recognize you and could snap or bite.
When is a Seizure an Emergency?
While an isolated seizure at home usually doesn’t require immediate emergency action beyond ensuring your dog’s safety, certain situations are emergencies:
- Status Epilepticus: Continuous seizure activity lasting five minutes or longer.
- Serial Seizures: Repeated seizures occurring one after another without regaining consciousness in between.
Both status epilepticus and serial seizures are absolute emergencies requiring immediate veterinary attention! Seek veterinary care immediately.
- Cluster Seizures (Severe): More than 3 seizures in 24 hours.
Severe cluster seizures warrant hospitalization and close veterinary monitoring.
Can Seizure Medication Be Discontinued?
Discontinuing seizure medication carries some risk, but it may be appropriate for certain dogs. Generally, dogs should be completely seizure-free for at least a year before considering stopping medication. However, in breeds known for difficult seizure control (German Shepherds, Siberian Huskies, Keeshonds, Golden Retrievers, Irish Setters, St. Bernards), it’s often best to continue medication indefinitely. Phenobarbital should never be abruptly stopped; if you’re considering discontinuing seizure medication, discuss it thoroughly with your veterinarian to develop a safe and gradual tapering plan.
