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SEIZURE DISORDERS

Seizures, convulsions, fits…these are all words commonly used to describe abnormal nervous system behaviors that occur sporadically and for a brief period of time. While alarming to watch, they are seldom painful. Technically, these sporadic, paroxysmal, electric discharges involve diffuse or focal areas of the brain’s cortex and result in partial or complete loss of consciousness, or other specific neurological dysfunctions. Depending on which part of the brain is involved, they may range from mild twitching episodes (focal seizures) to fulminating, unconscious convulsions (generalized seizure). While rarely life threatening, they are always terrifying.

Seizures can occur in any species, but the dog is a more common victim. The term "seizure’ is not synonymous with epilepsy. Presently, almost every breed of dog has been affected by primary CONGENITAL epilepsy, an error of the brain that one is born with, but only a few actually have documented evidence of inherited epilepsy, that which is passed from generation to generation. The EXTRACRANIAL (outside of the brain) causes of seizures include poisons or toxins (organo-phosphates, chlorinated hydrocarbons, strychnine, tetanus, hallucinogenic drugs, etc.) and the chronic toxicity of lead. Within the body, all cardiac and respiratory abnormalities which result in hypoxia (a relative lack of oxygen) can result in seizures. Metabolically induced seizures (seen with certain liver and kidney diseases, diabetes mellitus, etc.) are generally reversible once diagnosed and treated. INTRACRANIAL (within the brain) etiologies represent the most common causes of seizure disorders. Epilepsy is the most frequent diagnosis. Encephalitis is also common. Canine distemper, for example, can manifest itself in numerous forms and can be seen in young or old dogs. Feline infectious peritonitis (FIP) and feline leukemia (FELV) related illnesses can cause seizures. Blood and cerebral spinal fluid tests are invaluable in determining the definitive diagnosis.

Bacterial encephalitis can result from an infection in the blood stream or infections extending from the eye, ear or nose. Clinical signs vary from depression, rigidity, and fever, to seizures. Protozoal (toxoplasmosis, neosporosis) and fungal (blastomycosis, cryptoccosis and coccidioidomycosis) infections all result from extensions or infections and can often be fatal.

Tumors (neoplasia) that occur in the brain can be benign or malignant and frequently elicit seizure activity. Depending on their extent and location there are a variety of management and/or treatment choices.

Acquired or inherited hydrocephalus (abnormal accumulation of fluid in the brain causing enlargement of the skull and pressure on the brain) can also cause seizures. It can be managed medically, if diagnosed prior to extensive cortical damage, or surgically in advanced cases.

Intracranial trauma with anoxia (loss of oxygen) or subsequent scar tissue can result in seizure disorders. These seizures may not arise for weeks or even years after the initiating event occurs, making the diagnostic workup far more important than the recent history.

Inherited conditions center around epilepsy. In certain toy breeds (Poodle and Pekingese) the seizures are often responsive to common anticonvulsant therapies. Seizures resulting from epilepsy in larger breeds (German Shepherd, St. Bernard, Irish Setter, Retriever, Husky, Malamute and Old English Sheepdog) are among the most challenging. They may be difficult to control with single anticonvulsants and often require safe levels of a combination of anticonvulsants.

Epilepsy originates from a cluster of physically normal, but electrically malfunctioning nerve cells. The abnormal electrical discharges cause no problem as long as they do not reach a specified level of activity. However, at that threshold level the electrical discharge recruits adjacent neurons (nerve cells), the activity spreads, and either mild (petit mal) or severe (grand mal) seizures develop. Treatment is aimed at making the threshold harder to reach or limiting the spread of the abnormal electrical activity.

Due to the many possible causes of seizures, your family veterinarian may recommend a full seizure workup. Seizures must be treated on the basis of their origin (i.e. metabolic and toxin based seizures are often treated as emergencies with depressants or anticonvulsants but must ultimately be managed by correcting the specific abnormality). This workup will include blood tests to evaluate internal organ function such as a Total Body Function Profile and Bile acid Assay. In addition, skull x-rays, a spinal tap to obtain cerebrospinal fluid (CSF) samples and pressure levels, a CT scan or MRI may be indicated. While these more specialized tests may require sedation or anesthesia, the utilization of new gas anesthetics (Isoflurane) and advanced monitoring techniques have made these procedures routine with minimal complications.

    TREATMENT

Once the diagnosis or cause of your pet’s seizures is determined, a course of treatment can be selected. Many times this will be in the form of medications administered at home with follow up visits with your family veterinarian. On occasion, a surgical procedure may be needed to alleviate the source of the problem in combination with medical therapy. In all cases, the determination of the cause of the seizures is the first and foremost consideration when selecting a treatment plan.

If your pet is diagnosed with having idiopathic epilepsy, we will advise you on a long term control plan. Because this disorder does not involve a well isolated brain lesion, but instead is a cyclic electrical malfunction, medication will need to be given regularly on a daily basis. Periodically, your pet’s blood level of anticonvulsant will be checked along with blood tests to monitor and minimize its potential long term side effects.

Because we treat epilepsy, not cure it, an occasional seizure is not "unexpected" while on anticonvulsant medication. We therefore target our treatment to reduce the severity and frequency of seizure activity, not to necessarily eliminate its occurrence. Rarely, a condition of Status Epilepticus may occur where many seizures occur one after another. This is an emergency situation and your pet must be seen immediately to stop the seizures and save his/her life. This requires intravenous medications and careful monitoring.

We also request that you keep a log of all seizure activity. Many times seizures occur at specific intervals, accompanying specific stressful situations, hormonal cycles, or other unusual events. These logs may allow us to alter specific doses or augment medications at peak times to better control seizure activity as well as minimize the circumstances precipitating a seizure.

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