A seizure, also known as a fit or convulsion, can be defined as “involuntary contractions of the muscles, abnormal sensations, abnormal behaviors, or some combination of these events” that can occur in some dogs. A seizure is caused by the sudden and excessive firing of nerves in the brain.
Symptoms of dog seizures can vary from generalized signs affecting all parts of the body to focal manifestations that only impact part of the body. For example, a generalized seizure may manifest as a dog falls over, paddles all limbs, teeth chattering, foaming at the mouth, urinating, defecating, barking and/or other vocal behavior. A focal seizure can cause facial twitching only.
For more information on seizures, please read our full medical article on “Seizures in Dogs”. A common question that dog owners ask is “what are the causes of dog seizures”?
Causes of Dog Seizures
Seizures are considered a symptom. A symptom can be a sign of a disease but is not actually a disease. Symptoms are a physical sign that often can have many different causes. For example, some common symptoms include diarrhea, vomiting, limping, and bad breath. If we look at the symptom of limping, possible causes could be anything from a thorn in the paw pad, a fractured leg, soft tissue injury, laceration, or a ligament tear.
It has been estimated that 0.5% to 2.3% of dogs may have seizures. Seizures occur in both males and females with equal frequency. Many dogs, in fact up to 80% of dogs, will have one seizure and never have another seizure.
Below we will review some possible causes of dog seizures:
- Hypoglycemia (Low blood glucose/sugar). When the blood glucose falls below 70 milligrams per deciliter (mg/dl) of blood, some dogs will become weak, lethargic, and as the blood sugar drops further …will seizure. The muscle activity created by the seizure is a way the body will release glucose from the muscle tissues to increase the blood glucose level. This is most common in small and toy breed dogs.
- Liver disease (called “hepatic encephalopathy”). The liver normally functions to filter toxins from the blood. When this doesn’t happen normally, toxins can build up leading to lethargy, disorientation, and seizures.
- Inflammatory or infectious diseases that affect the nervous system can cause seizures.
- Poisons or toxins. There are many toxins and poisons that can cause seizures. Some examples are bromethalin (which is a kind of rat poison), pyrethrins or organophosphates (common ingredients in over-the-counter flea products), hexachlorophene, chlorinated hydrocarbons, metaldehydate, lead, myotoxins, and strychnine.
- Brain tumors can cause seizures. A common sign of a brain tumor is seizures but other symptoms may develop over time such as abnormal eye reflexes, lameness or trouble walking, tremors, behavior changes, and disorientation. Brain tumors can occur in the following ways:
- Tumors arising from brain tissue include meningioma, glioma, choroid plexus tumors, and several others.
- Tumors can arise from tissues that live in the brain, For example, a tumor can arise from the pituitary gland (pituitary gland tumor).
- Tumors can metastases to the brain from other organs such as lung cancer could metastases to the brain.
- Tumors can grow into brain tissue from other areas. An example is a nasal tumor that grows in the brain.
- Head trauma. Head trauma is a blunt or penetrating injury that occurs to the head. The most common cause of head trauma is from a dog being hit by a car or other vehicle. Other causes of head trauma can occur from blunt trauma such as being hit by a bat or a swing. Additional causes are being stepped on, being hit or crushed by a door, being crushed in a recliner, falls, gunshot wounds, and animal fights just to name a few. All of these examples of trauma can cause swelling of the brain tissues that leads to disorientation, lethargy, weakness, abnormal eye reflexes, tremors, and potentially seizures.
- Heat stroke. Another cause of seizures can result from heat-related illness. Heat stroke is a condition arising from extremely high body temperatures (rectal temperature of 105 to 110 degrees Fahrenheit), which leads to nervous system abnormalities. Symptoms include lethargy, weakness, collapse, seizures, tremors, and/or coma. A common cause of heat stroke is an owner that allows a dog to remain in a car with closed windows on a hot summer day.
- Infectious diseases. Distemper and other viral, bacterial and fungal diseases can infect the brain and cause seizures. Many times dogs will have fevers, lack of appetite, coughing, as well as other symptoms.
- Blood vessel disorders that affect circulation or cause clots to the brain can also cause seizures.
- Seizures can also be classified as idiopathic. This means that no underlying cause for the seizures can be determined. These dogs are often determined to have “epilepsy”. This is common in young healthy dogs from 6 months to 5 years of age.
- Heart disease can cause symptoms that can appear like seizures. Some dogs will “faint” which is referred to as syncope. Signs of heart disease may include coughing, exercise intolerance, and trouble breathing. Some dogs are asymptomatic and only experience the symptom of syncope when their heart goes into an abnormal heart rhythm (arrhythmia). Heart disease does not cause seizures but is mentioned in this list as syncope is commonly mistaken as a seizure.
What’s Next in Dogs with Seizures?
If your dog is having seizures, we recommend that you see your veterinarian to identify any potential underlying cause for the seizures and determine if your dog requires treatment.