What is a Seizure?
A seizure is an external manifestation (something we can see) of abnormal, intermittent electrical activity inside the brain. Although seizures may occur only occasionally, the source or cause of the electrical abnormality is our top concern. It is important that we determine, to the best of our ability, where the seizure activity comes from if we are to best help, if not cure, your pet.
A seizure is also sometimes referred to as a convulsion, a fit or an ictus. A common form of a seizure may consist of the following symptoms; the dog stiffens, loses consciousness, urinates and salivates, jerks intermittently, and paddles and then recovers. Before the seizure, the dog may run to the owner or whine as if it feels uneasy or knows something is about to happen. This is called an aura and may last a few seconds or may hours. After the seizure, the dog may pace up and down or in circles, be disoriented, lose sight or may show other behavioral changes. These are called post-ictal signs and may last from a few minutes to several days. The seizure itself usually lasts from 1-5 minutes, although it may be much longer. If a seizure lasts more than 15 minutes, or if one seizure rapidly follows another, the dog is said to be in “status epilepticus.” “Status epilepticus” is an emergency situation!
Recognizing a Seizure
Depending on the parts of the brain affected by the burst of electrical activity, the signs that the dog shows during a seizure may vary. For example, if the behavioral areas of the brain are affected, then changes in behavior may be apparent. The dog may also seem to be hallucinating. Similarly, if the visceral centers are involved, the dog will urinate, salivate, defecate or vomit. Muscle spasms, twitches and paddling are the result of motor areas of the brain being affected. Loss of consciousness, disorientation and hysteria are a result of effects on the centers controlling the alert state of the dog.
Causes of Seizures
Intracranial (within the brain) causes of seizures in dogs include: Acute brain infection (encephalitis), increased size of the fluid-filled cavities in the brain (hydrocephalus), brain tumor, acute brain injury and acute infection of the outer coverings of the brain (meningitis).
Possible extracranial (outside the brain) causes of seizures in dogs include: Poisoning, Valley Fever, Tick fever, liver disease, low blood sugar, diabetes, kidney disease, low thyroid (hypothyroidism), other infections and low blood calcium. Statistically, about 60% of seizures are caused by external circumstances.
What is Epilepsy?
Epilepsy is defined as a state of repeated intermittent seizures that originate within the brain. It is not a single disease. Epilepsy has several causes, the most common of which are postencephalitis (acquired) and inherited (genetic). Other less common causes are shortage of oxygen (posthypoxia) or injury at birth, and brain injury (post-trauma) at any time in life. “Post" is used indicate an ongoing seizure problem that persists after the acute infection or injury has occurred. Seizures may not even be seen at the time of the brain infection or injury – they may not start until many months or years later.
Types of Seizures
Recognized seizures in dogs include: Focal motor (twitches limited to one part of the body with no loss of consciousness), generalized motor (loss of consciousness with gross body movements) and psychomotor (marked behavioral changes seen either after the generalized motor seizures or making up the entire seizure). “Limbic”, “temporal lobe” or “diencephalic” may also be used to describe a seizure with largely behavioral or visceral (vomit, diarrhea) changes. A few seconds before some generalized seizures a dog may twitch one leg. This is called a localizing sign and indicates which area of the brain is involved first.
Veterinarians do not recognize “Jacksonian” seizures in the dog, although the term may be used to describe focal motor seizures. The terms “petit mal” and “grand mal” are sometimes used to describe focal or generalized seizures.
Frequency of Seizures
Seizures due to causes other than epilepsy tend to follow the course of that disease. Many seizures may occur initially with an increasing frequency and severity. Then they occur less frequently and with less severity as the acute disease passes or recovery occurs. The frequency and severity of the initial seizures are an indication, but not a reliable one, of the probable cause of the seizures. Seizures due to epilepsy tend to begin as short, mild episodes that become more frequent and severe during the initial 1-2 years. After that, the pattern tends to stabilize for many years and the frequency may decrease in old age. Unfortunately, this is only a tendency because epileptics may have an episode of “status epilepticus” as their first seizure, having several seizures one after the other, and fall immediately into a fixed, very frequent pattern. They may show a rapidly increasing frequency or have a varied pattern of months with no seizures followed by frequent attacks. A seizure pattern may do just about anything. The variability of seizure patterns makes evaluation of therapy difficult. Veterinarians do not know in advance what the dog’s pattern will be and treatment is usually started in the early phase when seizure patterns are developing.
Factors Affecting Frequency of Seizures
Physical irritations such as itchy skin, sore ears and pain will increase the frequency of seizures. Also, emotional irritation, worry or stress such as a visit to the veterinarian or kennel, visitors, another dog, a new baby, a party, the weekend, a child leaving for college, unaccustomed boredom or any event in the life of the owner that makes the owner change habits or be upset may increase the frequency of seizures.
Hormones such as estrogen can lower the threshold to seizures of parts of the brain. Estrogen is at high levels in female dogs in heat. (Therefore intact females should be spayed) Drugs such as phenothiazine derivatives may precipitate seizures in epileptics. Most antihistamines, tranquilizers and antiemetics (anti-travel sickness) are phenothiazine derivatives. Such drugs should not usually be given to epileptics. Seizures tend to occur when a dog is in light sleep or relaxing, although some dogs may be affected while they are excited. Thus, the night is a common time for seizures to occur.
Any dog may become an epileptic for acquired reasons such as postencephalitis, brain trauma or birth injury. However, in certain breeds, epilepsy is a common problem. Such breeds are regarded as having a high incidence of genetic epilepsy or at least a tendency to epilepsy. Some breeds have been studied carefully and the exact genetic mechanism of epilepsy is known (Beagles, Keeshunds). In others, it is generally accepted that genetic epilepsy occurs (German Shepherds, St. Bernards, all Schnauzers, Cocker Spaniels, Irish Setters, all Poodles, Tervurens). Some breeds are suspected (Retrievers, Labradors, Shetland Sheepdogs, Siberian Huskies). In some breeds the problem may be limited to just a few blood lines, but in other it seems widespread. Any individual dog may have epilepsy for genetic reasons or it may have acquired it. It is rarely possible to diagnose the exact cause with certainty.
The problem of genetics is the major reason that no dog that has had seizures of unknown (perhaps inherited) cause should be used for breeding. Females should always be spayed to achieve better control of seizures. Male dogs also benefit form neutering because of reduced sexual stress.
Diagnosis of Seizure Cases
The general health, age, breed and seizure pattern may suggest that some causes are more likely than others. The history, physical examination and neurologic examination all play a vital part in the diagnosis. There is no specific test for epilepsy in the dog; not even the electroencephalogram (EEG) is sufficiently reliable. Epilepsy is a diagnosis of elimination – elimination of all other causes of the seizures.
Generally, a study of the blood cells (CBC – complete blood count) and a panel of chemical analyses of the blood are done. This is to detect low blood sugar or calcium and liver or kidney disease. In instances associated with intracranial causes, a cerebrospinal fluid (CSF) tap may be performed to measure the pressure inside the brain and to obtain fluid for analysis. An EEG may also be obtained. Other research-type procedures may be available at veterinary colleges, but they usually do not specifically diagnose epilepsy. Computerized axial tomography (CAT) or magnetic resonance imaging (MRI) scans may be used if a brain tumor is suspected.
Treatment of Seizures
Dogs with seizures due to diseases other than epilepsy are given specific treatments for their disease. They may also be given anti-convulsants. Epileptics are treated with anti-convulsant drugs. There are a few common anti-convulsants and several newer or less commonly used drugs. If seizures are mild, occur singly and less frequently than one every 1-2 months, the side effects of the drugs may outweigh the benefits of seizure control. If status or multiple seizures on 1 day have occurred, then the epileptic must be treated. 80-90 percent of epileptic dogs are controlled – that is most epileptic dogs can be well treated. This does not mean cured. In some breeds, such as German Shepherds, this may drop to 25 percent control. Control – which is a dramatic decrease in, but not necessarily absence of, seizures – may only be achieved after many months of therapy with a variety of drugs or drug combinations. Control may be lost even after several years of success.
Common side effects with anti-convulsants are increased thirst, urination or appetite, drowsiness, clumsiness and hyperexcitability. These effects may be temporary or may persist as long as the drug is given. Some drugs produce liver changes. These changes may become serious in some individuals. Epileptics on medication require periodic physical examinations and blood tests. Evidence suggests that dogs do not suffer during a seizure, but disorientation commonly occurs after a seizure. This may be upsetting to the dog. Some dogs may scream or moan in a seizure. This appears to be involuntary and not associated with pain. Provided the epilepsy is controlled, the life expectancy of an epileptic dog is not shortened but normal. If a dog has had no convulsions for 1 year, your veterinarian may slowly reduce the dose of anti-convulsant over several months. During a seizure, the dog is rarely dangerous but should not be moved or handled unnecessarily except to stop it form injuring itself. Talking to the dog may help reassure it. If the seizure lasts over 10 minutes, call your veterinarian.