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What are the causes of epilepsy (seizures) in pets?
There are numerous causes of seizures. The causes fall into one of three general categories: metabolic, structural, or idiopatihic.
Metabolic or extracranial (outside the brain) disease resulting in seizures include hepatic encephalopathy (liver disease causing neurologic signs), hypoglycemia (low blood sugar), hyperglycemia (high blood sugar), renal (kidney), disease, electrolyte disturbances, several toxins, anemia, and cardiopulmonary (heart and lung) disease.
Structural (intracranial) diseases resulting in seizures include hydrocephalus (fluid accumulation in the skull), brain tumors, storage diseases, infectious and noninfestious encephalitis, injuries, and vascular disease.
If no metabolic or structural cause for seizures are found it is termed as idiopathic (of unknown cause) epilepsy. The most common seizure patient is the idiopathic epileptic. Most animals that have idiopathic epilepsy develop seizures between 1 and 4 years of age, with no identifiable metabolic, infectious, toxic, or structural cause for the seizures. The seizure episodes in idiopathic epileptics are typically less than three minutes in duration and are not harmful in themselves. Older dogs presenting for seizures for the first time rarely have idiopathic epilepsy. Certain breeds have a higher incidence of idiopathic epilepsy, including Beagles, Belgian Tervurens, Keeshounds, Collies, Saint Bernards, German Shepherds, Golden Retrievers, Irish Setters, American Cocker Spaniels, Wire Fox Terriers, Huskies, Malamutes, and Miniature Poodles.
How does the veterinarian decide what the cause of the seizures are?
After obtaining a history and examining the patient the veterinarian decides if toxin exposure or infectious causes should be considered. If toxin exposure or infection is unlikely metabloic, structural and idiopatic causes are considered. Blood work and a urinalysis is often done to rule out metabolic disease, assess the liklihood of infection and obtain a baseline in case anti-epileptics are prescribed. Specialized brain imaging (CTscan or MRI), and spinal fluid analysis may be needed. Referral to a tertiary care facility such as NC State or The Veterinary Speciality Hospital may be recommended in some cases. The aformentioned procedures do require anesthesia. There is a small chance that a pet could have complications, such as increased seizures or death after these procedures are performed However, the value outweighs the risk in most instances when these tests are indicated. A spinal tap helps us evaluate cells and protein present in the sample that may indicate infection, inflammation, or cancer. Imaging rules out structural abnormalities of the brain. If the doctor strongly suspects idiopathic epilepsy he or she may only recommend baseline bloodwork and medication or monitoring depending on the individual case.
What can be done for the other causes of seizures that are not of the idiopathic type?
If seizures are determined to be secondary to liver dysfunction anticonvulsants may or may not be used. Antibiotics, lactulose (a drug that works in the gastrointestianl tract by binding toxins involved in the cause of the seizures) and occasionaly steroids are administered. An ultrasound of the abdomen is done to evaluate the organs, including the liver. A tru-cut biopsy or fine needle aspirate at the time of the ultrasound can be helpful in pin pointing the actual disease process and assisit with the specific diagnosis and prognosis.
If seizures are suspected to be secondary to kidney disease, medications and fluids are given to help the body rid itself of nitrogenous wastes and establish or maintain electrolyte balance while the root cause is being investigated .
If the seizures are suspected be secondary to a disease process involving the brain itself, the treatment depends on the exact problem. Infections are treated with appropriate medications, tumors can sometimes be treated definitively. Seizures secondary to brain tumors that are not treated definitively are often slow growing with seizures that can be contolled with anti-convulsants . In these cases survival time with normal quality of life may be possible for sometime.
Toxic causes of seizures are treated depending on the toxin. We attempt ot bind or remove any toxin suspected of still being present in or on the patient. Lead poisoning is treated with chelating agents that help remove the lead from the body. Toxic causes of seizures that are not treated usually lead to worsening signs and are often fatal if left untreated.
How harmful are seizures to my pet?
Seizures can be harmful but usually are of no lasting consequence if short in duration. Prolonged or repeated seizures in a short period (cluster seizures) can cause organ damage, especially the heart and kidneys, hypoglycemia (low blood sugar) and hypoxia (low oygen in the blood). Occasionally the blood develops a clotting problem called DIC which can be fatal. Persistent, prolonged or cluster seizures are more detrimental than one isolated seizure. If a seizure lasts longer than 3 to 5 minutes or seizures are recurring frequently or in clusters emergency treatment should be obtained.
What should I do when my pet has a seizure?
Do not attempt to restrain the pet or put anything in its mouth. Keep the pet from injuing itself against sharp or hard objects in the environment. Note the duration of the episode, what the pet was doing prior to the seizure, during the seizure and how long it takes for the pet to return to normal after the seizure. If the seizure is exceeding three to five minutes or cluster seizures are occuring seek professional care as soon as possible.
Can I tell if my pet is about to have a seizure and what are the components of a seizure episode?
Some animals are anxious before a seizure and may seek out their owners. Other behaviors that are unusual for that pet may be demonstrated prior to a seizure as well. This is called the pre-ictal phase. The actual seizure is the ictal phase, and may be characterized by “chewing gum” motions of the face, muscular twitching, thrashing, paddling, urination and/or defecation, unusual vocalizations, stiffening, falling over or moving to one side, panting, vomiting, or more subtle behaviors such as staring into space or minimal twitching (these types of seizures are rare). The post-ictal phase is characterized by depression or stuporous behavior, the animal may be transiently blind, or may just not be “acting right” without any obvious problems.
Describing the event to the veterinarian may help give an indication of the cause and what course to pursue. It may even point us in another direction as some events are actually fainting episodes that are cardiac related .
How are seizures treated?
Sometimes the owner chooses not to treat the animal if the seizures are of short duration, and occur infrequently. If not, then typically the animal is given Valium intravenously if the seizure was prolonged, in clusters, or is still occurring when the animal arrives at the hospital. Then we start the pet on phenobarbital once the seizures are controlled by the Valium. This drug is given orally twice a day. After 30 days, we check a blood sample to make as sure as possible that we have achieved a therapeutic but non-toxic level. Once a therapeutic level is achieved periodic monitoring is necessary to insure there is no need to change the dosage and that there is no evidence of any adverse reactions to the drug. On occasion more than one antiseizure medication is needed or medication needs to be changed. After the therapeutic dose of phenobarbital is determined, we monitor liver and other organ function at least annually thereafter. Phenobarbital levels are also followed in many cases.
Successful seizure management is judged in consultation with the pet owner. We strive to decrease the numbers of seizures compared to pre-treament occurences as well prevent cluster seizures and severe seizure episodes.
How effective are aniconvulsant treatments and what is the prognosis for my dog?
About 70% of dogs have their seizures controlled adequately by medicatona while approximately 30% are either poorly controlled or do not respond to treatment. Prognosis depends on the cause of your pet’s seizures. Animals with idiopathic epilepsy usually live a full, normal life with good to excellent seizure control. Organ dysfunction causing seizures may have a good or a poor prognosis, depending on the severity of organ damage, and the ability of the body to recover and heal that damage. Intracranial disease can have a good prognosis (bacterial infection successfully treated) or a poorer prognosis if the seizures become or already are not contollable. Eventually brain tumors may result in a patients passing but that time can often be delayed with good to excellent quality of life in the mean time.
Once your pet has seizured, we strongly encourage you to keep a record of the events, including date, time, length of seizure and length of time it takes for your pet to get back to his or her old self (post-ictal phase). Also, note any unusual behavior prior to the event. If the seizures increase in number, severity, or frequency, it will influence our treatment decisions. Seizures become dangerous if they are unrelenting. If your pet is still seizuring after five minutes, bring it to us or to the after hours sevice for treatment and evaluation.