At the Animal Clinic at Thorndale, seizures are one of the most frequently seen neurological problems in dogs. A seizure is also known as a convulsion or fit. A seizure represents a period of abnormal brain wave activity that leads to a variety of clinical signs.
Prevalence
Seizures represent a common neurologic disturbance in the dog. Seizures are seen on a fairly regular basis by veterinarians in private practice.
Clinical Signs
A number of signs may be observed when a dog is having a seizure. Signs usually start suddenly and end abruptly. They may involve the whole body or just parts of the body, such as one limb or particular muscles of the face. Some of the more common signs include:
Loss of consciousness or a change in level of consciousness
- Contractions of all the muscles in the body, paddling of the legs, chewing,fly biting
- Changes in mental awareness from non-responsiveness to hallucinations
- Behavioral changes, including non-recognition of owner, viciousness, pacing, and running in circles
Components of a Seizure
A seizure occurs in three phases:
1) The pre-ictal phase, or aura, is a period of altered behavior in which the dog may hide, appear nervous, or seek extra attention from people it knows. It may be restless, nervous, shaking, or salivating. This may last a few seconds to a few hours.
2) The ictal phase describes the seizure itself and lasts from a few seconds to about five minutes. During this period, all of the muscles of the body contract strongly. The dog usually falls on its side and seems paralyzed while shaking. The head will be drawn backward. Urination, defecation, and salivation often occur. If it is not over within five minutes, the dog is said to be in status epilepticus, or a prolonged seizure. Status epilepticus is a medical emergency.
3) During the post-ictal phase, there is confusion, disorientation, salivation, pacing, restlessness, and/or temporary blindness. There is no direct correlation between the severity of the seizure and the duration of the post-ictal phase.
Dogs that do not receive medical attention with status epilepticus are at risk for serious complications because of the physiological changes that occur. Most significant is the rise in body temperature that occurs from continuous strong muscle activity. This can lead to hyperthermia and death.
Causes/Transmission
There are many, many causes of seizures. For this reason, when we first begin an evaluation of the dog with seizures, we think less in terms of the specific disease and focus more on categories of diseases. For example, if this is a young dog, could there be an structural brain abnormality, such as hydrocephalus? In an older animal, could it be a degenerative disease or a brain tumor? For outdoor dogs, what is the potential for exposure to toxins such as antifreeze?
Epilepsy is the most common and of least consequence to the dog. These dogs are basically normal between seizure episodes, though the frequency and severity of seizures may increase over time. There is thought to be a heredity component to epilepsy, so these dogs should not be bred. The other extreme includes severe diseases such as brain tumors. Often with metabolic disorders and tumors the dog is not completely normal after a seizure and unless the underlying disorder is treated progression is inevitable.
Evaluation of the Dog with Seizures
When a seizure occurs, it is important that you give us a thorough account of recent events, especially recent exposure to any toxins, poisons, medications, hallucinogenic substances or history of head trauma. A physical examination, a basic battery of blood and urine tests, and an electrocardiogram (EKG) are also commonly performed. These tests rule out disorders of the liver, kidneys, heart, electrolytes, and blood sugar level. Additional testing for hypothyroidism may be warranted.
If these tests are normal and there is no exposure to poison or any history of trauma, further diagnostics may be performed depending on the severity and frequency of the seizures. Occasional seizures are of less concern than if seizures are increasing in severity and frequency. In this instance, a spinal fluid tap and fluid analysis may be performed. Specialized imaging of the head with a CAT scan or MRI might be performed. Fortunately, these additional tests are usually not needed. In the event that they are, we would refer you to a specialist (neurologist) for further diagnostic testing.
Treatment
Your dog may be discharged with no medications or with a 1-2 week course of anticonvulsant therapy. If the seizures are brief and not occurring more frequently than one every two or more months, it may be reasonable not to begin chronic anticonvulsant therapy until there is an increase in frequency or severity. Treatment is based on when, or if, another seizure occurs. That may be days, months, or years. At some point, many dogs have seizures frequently enough to justify continuous anticonvulsant therapy. Since that means medication must be given every 12 to 24 hours for the rest of the dog’s life, we do not recommend treatment until seizures occur about every 30 days or unless they are severe (grand Mal), last more than several minutes or occur in clusters.
It is important to avoid sudden discontinuation of any anticonvulsant medication. Even normal dogs may be induced to seizure if placed on anticonvulsant medication and then abruptly withdrawn from it. We can outline a schedule for discontinuing the medication.
Phenobarbital is generally the first anticonvulsant prescribed. It is an addictive drug and the amount of medication needed to control seizures will likely increase over the dogs lifetime. It is very important this medication not be stopped abruptly once begun. Periodic blood testing to assess the phenobarbital blood level is required. If the blood level is high or liver problems are apparent and seizures are not well controlled, other medications such as potassium bromide may be added on or substituted. There are additional anticonvulsant therapy options, such as newer medications, rectal administration of valium compounds, eye compression techniques,and acupuncture, that may be of benefit for some patients.
Status epilepticus
This is a prolonged seizure or rapid recurrence of seizures and requires immediate medical intervention. Intravenous anticonvulsants generally need to be administered to break the seizure cycle. Status epilepticus can still occur in animals on regular anticonvulsant medications. In some cases, despite appropriate medical intervention, the seizures may not be stoppable. Prompt treatment generally improves the outcome.
Additional Treatments
Some dogs with seizures are known to have granulomatous meningoencephalitis. This is a disease that causes inflammation in the brain and the tissue coverings around the brain. It is not caused by infection. The only way to make a confirmed diagnosis is with an autopsy. However, it usually responds well to corticosteroids (“cortisone ” or “steroids”). Therefore, corticosteroids may be tried when phenobarbital is not effective.
Prognosis
The prognosis is dependent upon the cause. In some cases, the cause cannot be identified so the prognosis in uncertain. In this situation, the frequency and severity of the seizures are monitored to assess progression of the underlying disease process. Even when the underlying cause is not diagnosed, these patients may benefit from anticonvulsant therapy.
Transmission to Humans
There are some infectious causes of seizures in dogs that pose a health risk to humans; most notable is rabies. Fortunately, this is uncommon.
Many owners are bitten by the seizing animal because of a well-intentioned effort to help. Despite the dramatic signs of a seizure, your dog feels no pain, only bewilderment when recovering. Dogs do not swallow their tongues. If you put your fingers into its mouth, you will not help the dog and will run a high risk of being severely bitten. The important thing is to keep the dog from falling and hurting itself. As long as it is on the floor or ground, there is little chance of harm occurring.