Epilepsy is the term used to describe a condition where a dog suffers many seizures. Primary epilepsy has no known cause, but secondary epilepsy has many. Secondary epilepsy is not a disease in itself, but rather a symptom of neural damage that causes what the Canine Epilepsy Network refers to as an "electrical storm" in the brain when cells become too stimulated. This malfunction of the brain's electrical signals can take control of the dog's major motor functions, causing the jerking motions known as a seizure. Many things can cause epilepsy, stemming from hereditary, infectious or traumatic triggers.
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Trauma
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Severe head injury can lead to seizures. Although the part of the brain that initiates the "electrical storm" is small, trauma to any part of the brain can trigger epilepsy, although the exact mechanism is unknown. Infection can also damage the brain physically, as the bacteria or virus attacks the brain cells and some cells die. In most cases, repair of the brain damage will cure the epilepsy, but sometimes the dog continues to experience seizures years after recovery from the trauma.
Metabolic Deficiency
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Different metabolic conditions such as low blood sugar, low thyroid function and low calcium levels can cause an electrolyte deficiency that can disrupt the normal firing of neurons. If the condition deprives the brain cells of necessary nutrients, the cells get over-excited and a seizure can result. These types of epilepsy can be either chronic or acute, but medication or changes to the dog's diet can bring them under control.
Toxins
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Some plants contain toxins that have evolved specifically to cause damage to a predator's brain. These chemicals enter the bloodstream and work inside the brain to disrupt or over-stimulate the electrical signals. These misfires interrupt the normal working of the brain, and epilepsy can occur, although it is normally reversible as soon as the system flushes the toxin. In some cases, a liver shunt causes the buildup of toxins, as the shunt allows ingested toxins to bypass the liver and be absorbed into the bloodstream. This condition may be hereditary and requires surgical correction.
Tumors
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A tumor causes epilepsy in much the same way as trauma, by causing damage to the brain tissue. The tumor also diverts blood supply away from the healthy tissues of the brain, causing the electrical signals to revolt and misfire. This begins the "electrical storm" that causes the seizure. Removal of the tumor may stop the epilepsy, but, in some cases, the epilepsy remains permanent.
Heart Condition
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When the heart is not working properly, the body does not efficiently circulate blood. As the function of blood is to carry oxygen to the organs, any deficiency can cause severe damage, especially in the brain. When the brain is oxygen-deprived for even a few seconds, severe damage can result. A seizure can be the visible sign of the brain's reaction to oxygen deprivation. This type of epilepsy is generally chronic and may be hereditary.
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