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Seizures and Epilepsy part II

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Causes of Seizures in pets

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).{{more}}

Possible extracranial (outside the brain) causes of seizures in dogs include: Poisoning, 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. 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.

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.

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.

Continued next week

For further information, contact: Dr. Collin Boyle
Unique Animal Care Co. Ltd. Tel: 456 4981