Seizures in Dogs | Types of Seizures
What is a seizure?
Seizures are caused by an electrical storm in the brain. Normal brain cells (neurons) use the electrical and chemical signals to communicate with each other. This communication can either be excitatory, tending to activate the next neuron, or inhibitory, tending to shut the next neuron off. A delicate balance of these excitatory and inhibitory influences on any given neuron determines whether it is going to become activated and pass information on to other neurons. If the balance within the brain shifts too far toward excitation, too many cells may become too excited and a seizure can result. Keep in mind, we are talking about excitation or inhibition of individual neurons in the brain, not whether your pet is excited to see you when you get home. In fact, seizures in dogs occur most commonly when the pet is relaxed or asleep, although they can occasionally be associated with exercise or emotional arousal.
We can see this excess excitation if we record the electrical activity of the brain through an electroencephalogram (EEG). On the EEG, the seizure will appear as a series of sharp spikes as waves of excitation overtake the brain. This electrical storm then causes changes in the behavior and movement of the animal which we recognize as a seizure. There are several different types of seizures depending upon the nature and location of the electrical storm.
Types of Seizures
Seizures are broadly divided into two types: generalized and focal (or partial) seizures. In a generalized seizure, the electrical storm appears to arise everywhere at once. In a partial seizures, the abnormal activity arises in a small area of the brain. Since your veterinarian may not see one of the seizures, he or she will rely on your description of what your pet does during the seizure to help them classify it. The descriptions provided here will help you understand the types of seizures, but don’t jump to conclusions. Describe for your veterinarian or the neurologist exactly what you observe.
Generalized, tonic-clonic (grand mal) seizures
Generalized seizures are further divided into two sub-types: major motor seizures (grand mal) and absence seizures (petit mal). The major motor seizures is the classic seizure. It is also sometimes called a tonic-clonic seizure. A classic seizure can have three phases, the aura or prodrome, the seizure itself (sometimes called the ictus), and post-ictal (post seizure) behavior. Not all seizures have three phases, but commonly they will.
The most common time for a dog to have a seizure is when they are relaxed and quiet. They may even occur from a sound sleep. Seizures can occur anytime, but if they occur only when an animal is excited or exercising, it may indicate a heart problem or low blood sugar.
Just as some dogs can sense when their epileptic owner is going to have a seizure, some owners can sense when their epileptic dog is going to have a seizure. The aura or prodrome is a recognizable change in the pet’s behavior that alerts the owner to an impending seizure. Most commonly, the pet that has an aura will act upset and anxious. He may seek attention from his owner or withdraw and hide. This aura may represent a focal beginning of the seizure and thus indicate a focal seizure, but we commonly see it in generalized seizures as well.
The classic seizure itself is called a tonic-clonic seizure. It begins with a stiffening of the muscles (the tonic part). Usually the pet will fall to their side with the legs stretched out and the head back. Once the seizure has begun, the pet is no longer conscious even though his eyes will remain open. Sometimes they will vocalize or the face may twitch. The vocalizations are involuntary and do not indicate pain. Often he will drool excessively, or he may urinate, defecate, or empty his anal glands causing a foul smell. He has no control over these “accidents” and is completely unconscious during the seizure. This tonic phase is usually very brief (less than 30 seconds) and gives way to rhythmic movements (the clonic part). Typically this consists of chomping of the jaws and jerking or running movements of the limbs. Often he will not breath well during a seizure and the tongue may turn blue. Even though the seizure may seem to go on forever, the average seizure lasts less than 2 minutes. If the seizure goes on much longer, we become concerned that the pet may go into a continuous seizure (an emergency situation).
Following the seizure, the pet may lay motionless for a period of time. Eventually he gets back on his feet. He may bounce back and be perfectly normal afterwards, but more typically there is a period of post-ictal behavior. Often the pet appears blind and disoriented during this post-ictal phase. He may pace or run about the house, bumping into things as he goes. Sometimes they are excessively hungry and will devour any food available. Rarely, a dog may behave aggressively during this period, especially if they are restrained. While such aggressive behavior is rare, it is important to recognize the possibility, especially if the dog is large and there are children in the household. Usually this post-ictal behavior begins to resolve within a few hours after the seizure and the dog gets back to normal.
Variations on the Theme
Not all generalized seizures follow this pattern. Some won’t show any aura but strike out of the blue. Some pets bounce back immediately after the seizures as if nothing had happened, while others may be disoriented for days. Some may show only tonic rigidity during the seizure itself, while others may show only clonic jerking and paddling. More rarely still, the pet may simply drop limply to the ground and lay motionless. A “drop attack” like this is more typical of a fainting spell, but can occur with seizures.
Cluster Seizures and Status Epilepticus
Most seizures are brief and isolated, but sometimes they can be more serious. The large-breed dogs tend to have clusters of seizures. In these cases, the dog will have one seizure and recover from it. Then a few hours later, they have another. They never completely recover before another seizure strikes. Then they have another seizure, then another seizure, then another, another, another … Sometimes this culminates into a continuous seizure that doesn’t stop, a condition called status epilepticus. Occasionally status epilepticus can arise out of the blue; the animal begins seizing and never stops. Either way, this is a true emergency requiring immediate veterinary care.
Source: Seizures: What You Need to Know; Hurricane Animal Hospital