What is a seizure?
A seizure is a burst of uncontrolled electrical activity between brain cells that causes temporary abnormalities in muscle tone or movements, such as twitching stiffness, limpness or spasms. Seizures are also called convulsions or fits.
Some dogs may have partial seizures that only involve part of the body. These are called petit mal seizures. Many dogs have seizures that include movements of the entire body and a loss of consciousness. These are called tonic-clonic or grand mal seizures.
In dogs, seizures typically happen suddenly, without warning, and last just a brief period of time, usually a few seconds to a few minutes. If your dog has a seizure, try to remain calm and remember that most dogs having a seizure do not hurt themselves. Any seizure or suspected seizure is a reason for a visit to your veterinarian.
What causes seizures?
There are many causes of seizures in dogs. These are grouped into two categories: problems that are confined to the brain and generalized conditions that affect the entire dog.
The brain, or intracranial, causes include congenital conditions that are present at birth. A common example is hydrocephalus, also known as “water on the brain.”
The most common intracranial cause of seizures is epilepsy. This is an inherited condition that results in increased excitability of the brain’s nerve cells. Dogs with epilepsy typically have their first seizure between the ages of six months and six years.
Infections and inflammation of the brain, such as meningitis, encephalitis, granulomatous meningitis-encephalitis (GME), canine distemper and rabies, will cause seizures. Interference with the blood supply to the brain, such as an infarction, or bleeding in the brain, will cause “stroke”-like conditions that may result in seizures.
Head trauma and the development of scar tissue in the brain are another intracranial cause. Cancer that develops directly from brain tissue or metastatic cancer that has spread to the brain from another part of the body will produce seizures.
Extracranial causes are conditions that affect the body, not just the brain. These include exposure to certain toxic substances such as lead, chocolate, antifreeze, marijuana, snail/slug bait (metaldehyde), organophosphate or carbamate pesticides, and ingestion of some human medications.
Metabolic problems such as low blood sugar (hypoglycemia) and low blood calcium (hypocalcemia) can produce seizures. Dogs suffering from advanced forms of liver and kidney disease can also have seizures.
How can I tell if my dog is having a seizure?
A dog that is going to have a grand mal seizure often begins showing abnormal behavior before the actual seizure. Dogs may hide, whine, act anxious, tremble or salivate anywhere from several seconds to several hours before a seizure. This period is called the aura, or pre-ictal phase.
In a generalized, grand mal seizure, the dog will suddenly fall on his side. The legs will first become stiff, followed by jerky, paddling, “bicycling” motions. The head is often held back with the neck extended. Dogs may cry out, have “gum-chewing” or chomping motions of the jaw, and salivate excessively. During most grand mal seizures, dogs will urinate and defecate.
The actual seizure is known as ictus and can last from a few seconds to several minutes. There is no response to your voice because the dog is in an altered state of consciousness while this is happening.
After a seizure, the post-ictal phase occurs. This is the recovery stage after the seizure. Some dogs continue to lie on their side for a few minutes, and some fall into a deep sleep. During the post-ictal period, dogs may be confused and disoriented. They may pace and wander aimlessly. Some dogs appear temporarily blind or deaf. These behaviors can last from minutes to hours, but they rarely persist for more than 24 hours.
Cluster seizures are two or more seizures within a 24-hour period with the dog regaining full consciousness between the seizures. Status epilepticus refers to either a single seizure lasting longer than five minutes or a number of seizures over a short period of time without regaining full consciousness between each seizure. This is a medical emergency. Seizures lasting more than five minutes can be life threatening.
How will my veterinarian determine the cause of the seizure?
Your veterinarian will perform a thorough physical examination and take a detailed medical history of your dog to try to determine what might have caused the seizure. You will be asked about your dog’s behavior before, during and after the seizure, and the frequency of the episodes. Information about vaccination status, medication, nutrition, supplements, preventives and any potentially toxic substances in and around the home is important. Capturing the event on video can help the veterinarian understand what happened.
As part of the workup, a neurologic exam is performed. This is a series of simple physical maneuvers such as shining a light in the eyes to assess the response of the pupils, checking the knee-jerk reflexes by tapping on the patellar tendons, and manipulating the legs to evaluate the strength and function of the legs. Your veterinarian may dilate your dog’s pupils in order to fully examine the eyes.
Blood tests, including a complete blood count and a chemistry panel, along with a urinalysis are run in order to identify the source of the seizure trigger. Specialized, advanced radiology tests such as MRI or CT scan of the skull may be required. If the test results are all negative or normal, it is assumed that the problem is a biochemical disorder within the brain, which is epilepsy.
What is the treatment for seizures?
The goal of treatment is to find the cause of the seizures and eliminate it. If a specific cause cannot be determined, oral anticonvulsant medication can be given to reduce the number, frequency and length of the seizures.
Phenobarbital has been the first-line therapy for canine seizure control for decades. It is effective, reasonably priced and can be given twice daily, which is relatively convenient. The downsides are the potential side effects. Sedation, hunger and thirst are the most common ones. Phenobarbital blood levels need to be periodically monitored, as higher dose levels can lead to the development of liver disease.
Potassium bromide is an effective drug for controlling seizures in dogs. This drug may take months to reach a stable blood level. Many dogs with seizures that are not controlled on phenobarbital alone respond well when this drug is given in combination with phenobarbital.
Levetiracetam (Keppra) is prescribed for refractory epilepsy in dogs because it has been shown to be fairly reliable and has minimal side effects. It appears to work best in combination with other seizure medications rather than as a sole therapy, but many dogs are able to use it as a single agent. There are no monitoring tests recommended for its use, and an extended-release formula allows for twice-daily use.
Zonisamide is an anti-seizure medication that is rapidly becoming a first-line treatment choice but is also used to supplement the more traditional drugs. It is a sulfa drug and may produce the side effects associated with sulfa antibiotics. These are mostly tear production and dry-eye issues, but also some immune-mediated reactions. Zonisamide can be used twice daily in dogs.
The treatment is not a cure. It is important to understand that seizures may still occur, regular blood tests are required to measure the level of medication, and the medication may be required for the rest of the dog’s life.
