Causes of Seizures in Dogs
Seizures are the most common neurological abnormality in companion dogs. In the broadest of terms, seizures are caused by abnormally large bursts of electrical activity inside the brain. Seizures happen because of conditions, events or defects that originate either inside of the skull (intracranially) or outside of the skull (extracranially). Whether intracranial or extracranial, these incidents cause excessive and unpredictable firing of nerve cells called neurons in the cerebral cortex, which is the outer layer of brain tissue that covers both of the cerebral hemispheres. This, in turn, causes a seizure to occur.
Intracranial Causes of Canine Seizures – Many different events and conditions that happen inside of a dog’s skull can lead to seizures. Some of these include: genetic brain defects, encephalitis (inflammation of brain tissue), infection, primary benign or malignant brain tumors, metastatic tumors that develop from the spread of cancer cells from remote regions of the body, abscesses in the brain, strokes, anatomical brain malformations or lesions that are present at birth (brain cysts, hydrocephalus, others), primary (acquired) epilepsy and idiopathic epilepsy of unknown origin.
Extracranial Causes of Canine Seizures – Extracranial, or reactive causes of seizures in domestic dogs can be further sub classified into those that are systemic, meaning they affect the whole body and those that are caused by some toxic insult to normal brain tissue. Systemic extracranial causes of seizures may include: heat stroke, liver disease, kidney disease, direct trauma to the head, infection with the canine distemper virus, sudden drop in blood sugar (hypoglycemia; common with overdose of insulin in diabetic dogs or from the presence of an active insulin-producing tumor), portosystemic shunt, low blood calcium and other metabolic abnormalities. Many different neurotoxic substances can cause canine seizures, especially at the advanced stages of the dog’s condition. These include: ingestion of or exposure to antifreeze/ethylene glycol, lead, metaldehyde, strychnine and other rodent baits, insecticides/organophosphates, poisons, chocolate and many other things. Toxic insults to the brain usually first cause the dog to shake or tremble uncontrollably. The signs then progress to seizures.
Preventing Seizures in Dogs
Since there are so many potentially unrelated causes of canine seizures, there is no one way to prevent them from happening. However, once the cause of the seizures is diagnosed, many of these disorders can be well-managed with medication and lifestyle changes. Dogs known to have seizures or that are otherwise suspected to have epilepsy probably should not be bred, because a hereditary component is suspected.
Although they are fairly common in companion dogs, all seizures should be taken very seriously. Most dogs with primary seizure disorders will require lifelong treatment. Sometimes, other medical conditions cause clinical signs that look like seizures; these must be identified and addressed, as well. Owners who think that their dog may be having seizures should consult with their veterinarian as quickly as they can.