Epilepsy refers to abnormal electrical activity in the brain resulting in seizures or convulsions. Brain cells called neurons are responsible for transmitting information. They communicate with one another by way of chemically-mediated electrical impulses. When too many neurons discharge their impulses simultaneously a seizure may result. The type of seizure produced depends on the location in the brain where the abnormal electrical activity occurs. There are two types of epilepsy. Primary epilepsy (also called idiopathic, inherited or true epilepsy) is the type for which no real cause can be found. Secondary epilepsy can be attributed to such things as toxins (oftentimes, lead), metabolic disorders (low blood sugar is a common cause), nutritional deficiencies, head injuries, brain tumors, etc. Seizures are also categorized by the type of activity produced. Dogs with primary epilepsy most often exhibit generalized seizure activity called a tonic-clonic seizure. The entire body is involved. The tonic phase is the period in which the dogs falls, assumes a rigid posture, becomes unconscious and stops breathing. This usually lasts 10-30 seconds. Then the clonic phase begins in which the dog's limbs exhibit a paddling motion. During the seizure, the dog may lose control of its bowel or bladder and salivate profusely. A partial seizure will affect only one area of the body. These are usually associated with secondary epilepsy. Status epilepticus is a seizure of abnormally long duration and is a medical emergency as the dog may stop breathing for a longer period of time. Clusters of seizures may also do the same thing. Both result in low blood oxygen and can produce permanent brain damage or death.
Careful observation of the dog during a seizure can provide valuable clues. There are three known seizure stages. The first is called the aura. During this phase the dog might demonstrate restlessness, nervousness, whining, trembling, salivation, wandering, hiding, hysterical running or other unusual behaviors. The second phase, called the ictus, is the actual seizure. The final, postictal stage is characterized by confusion, unresponsiveness, wandering, or temporary blindness.
Diagnosis of epilepsy is based upon testing for many causes. If one is found, the disease will be called secondary epilepsy. If none are found, primary epilepsy. Along with a history of what was witnessed during a seizure, the veterinarian may perform a physical examination and test neurologic function. Blood work-up may include a complete blood count and chemistry panel. Toxicology tests and examination of stool for parasites are also commonly done.. Additional tests that might follow include a spinal tap (with analysis of cerebral spinal fluid), skull x-rays, CAT scan, MRI, or EEG (electroencephalogram).
A number of oral drugs are available to help control seizure activity. These drugs may be prescribed on a daily, lifetime basis. There is no cure, but many dogs can lead rewarding lives despite their epilepsy. Alternative forms of therapy such as acupuncture have their proponents. As always, the wisest advice is to consult your veterinarian before making any changes or additions to your dog's treatment plan. Care recommended during a seizure includes providing a quiet environment and keeping the dog safe from injury (falling, other dogs, etc.). Whoever witnesses a seizure should also be aware of their own safety as it is not unusual for dogs to bite while seizing. Do not attempt to put anything in the dog's mouth during a seizure.
MODE OF INHERITANCE:
For those dogs diagnosed with primary epilepsy, a genetic cause is most likely. It is a single gene defect, but between different breeds, the exact disease-causing gene may differ. This is known as genetic heterogeneity in canine epilepsy. In the future, a DNA test may be developed which can identify the faulty gene at an early stage in the dog's life. Meanwhile, dogs with this diagnosis should be eliminated from breeding programs.
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Brewer, G. Clinical and genetic advances - canine epilepsy. Presentation at AKC/CHF canine health conference. St. Louis, MO., 1997, Nov.
Foster, R., Smith, M. What's the diagnosis?: Understanding your dog's health problems. New York: Howell Book House, 1995:59-60.