Seizures and Syncope

By Catherine Barnette, DVM

Seizures and syncope are commonly confused, due to similarities between the appearance of these episodes. In order to arrive at an accurate diagnosis and treatment plan, it is essential to work with your veterinarian to accurately identify the cause of your dog’s episodic weakness, as there are significant treatment differences between seizures and syncope.

What is a seizure?seizures_general_info_2018-01

A seizure is a sudden, uncontrolled movement of the body caused by abnormal brain activity. Some dogs may have partial seizures, involving only a limited portion of the body. Many dogs have generalized, or tonic-clonic seizures, involving movements of the entire body and a loss of consciousness.

"A seizure is a sudden, uncontrolled movement of the body caused by abnormal brain activity."

Seizures can be caused by a number of underlying conditions. The most common cause of seizures is idiopathic epilepsy, an inherited condition that results in increased excitability of the brain’s neurons. Dogs with idiopathic epilepsy typically have their first seizure between the ages of six months and six years. In addition to idiopathic epilepsy, other causes of seizures include toxins, liver or kidney disease, head trauma, or brain tumors.

What is syncope?

Syncope describes a temporary loss of consciousness and posture, also known as 'fainting' or 'passing out'. Syncope is caused by a temporary disruption in blood flow or oxygen delivery to the brain. Typically, this is caused by episodes of low blood pressure, although other internal changes can also trigger syncope.

"Syncope describes a temporary loss of consciousness and posture, also known as 'fainting' or 'passing out'. "

Common underlying causes of syncope include heart disease, heart tumors, emotional stress or anxiety, hypoglycemia (low blood sugar), or abnormalities in blood electrolyte levels. Additionally, some episodes of syncope are triggered by specific actions or activities, including coughing, urination, defecation.

What does a typical seizure look like?

A dog with a generalized seizure often begins showing abnormal behaviors prior to the actual seizure. Dogs may hide, whine, act anxious, tremble, or salivate for anywhere from several seconds to several hours prior to a seizure. This period of time is called the pre-ictal phase, or aura.

In a generalized, or tonic-clonic seizure, the dog will typically be seen to suddenly fall on his side. The legs will first become stiff, and this stiffening is often followed by rhythmic/jerky paddling motions. The head is often held back, with the neck extended. Dogs may vocalize, will often have repeated chewing or chomping motions of the jaw, and often will salivate excessively. Typically, dogs will also urinate or defecate during seizures. Seizures typically last approximately one to two minutes, although prolonged seizures can occur and require treatment.

Once the seizure has ended, dogs will have a prolonged post-ictal recovery period. This period may last up to 24 hours, depending on the individual dog. During the post-ictal period, dogs are typically confused and disoriented. They may be observed to pace and wander aimlessly, while some dogs may show further signs such as blindness, increased thirst, and increased urination.

What does a typical episode of syncope look like?

A typical syncopal episode will start suddenly, with no aura or pre-ictal phase. Syncope is often triggered by activity, happening while a dog is exerting himself. You may initially notice that your dog appears weak or wobbly, but this is not always observed and, if observed, this period will be short-lived. When the dog collapses, he will go suddenly limp. Like a dog having a seizure, a syncopal dog may urinate or defecate during the episode.

A syncopal dog may move his legs, but these movements are typically associated with the dog trying to get back up off the ground. These movements are in contrast to the paddling, rhythmic leg movements that are more commonly associated with a seizure. Syncopal dogs typically will not have chewing-gum motions of the jaw or increased salivation. The episode will end within seconds to minutes and the dog will recover rapidly, with no post-ictal period of disorientation.

What characteristics can be used to distinguish seizures from syncope?

A number of characteristics can be used to distinguish seizures from syncope.

1.      What was the dog doing when the episode started? Syncope is often triggered by activity, such as exercise, excessive barking, coughing, urination, defecation, or severe pain. Seizures may happen during activity or at rest, but typically are not associated with any particular trigger.

2.      Were behavior changes noticed prior to the episode? Dogs with seizures often demonstrate pre-ictal behavior changes, such as anxiety or whining. Syncope tends to come on unexpectedly, with no advance warning.

3.      What did the episode look like? Although there is considerable overlap between the signs of seizures and syncope, close analysis can often reveal differences. For example, a dog with rhythmic paddling are most likely having a seizure while a dog lying limp is most likely experiencing syncope.

4.      How quickly did the dog recover? A dog with syncope typically shows near-instantaneous recovery, while a dog with a seizure often shows prolonged disorientation or lethargy after an episode.

How are seizures and syncope treated?seizure_vs_syncope

Treatment is dependent on accurately determining whether your dog is experiencing seizures or syncope.

If you and your veterinarian determine that your dog is having seizures, further workup will depend on such details as your dog’s age, seizure history, and other concurrent medical issues. Most likely, the next steps will include bloodwork to assess cell counts and organ function. Following bloodwork, your dog may be started on anti-seizure medication or may be referred to a specialist for more advanced testing to assess for possible underlying neurologic

"Treatment is dependent on accurately determining whether your dog is experiencing seizures or syncope."

If you and your veterinarian determine that your dog is having syncope, your veterinarian will likely develop a plan to evaluate your pet’s heart function. Your pet may need to go on medications to help correct underlying heart abnormalities if one is detected, or your veterinarian may have other suggestions to decrease the frequency of your dog’s syncopal episodes.


What is the prognosis for a dog with seizures or syncope?

Your dog’s prognosis will depend on the cause of his seizures or syncope. In general, seizures in young dogs with idiopathic epilepsy typically respond well to treatment, while some other causes of seizures carry a more guarded prognosis. The prognosis for syncope is also dependent on the underlying cause – in some cases, avoiding triggers may be enough to eliminate your dog’s risk, while other dogs may have significant heart disease that carries a more guarded prognosis. Your veterinarian will be able to discuss your pet’s prognosis more specifically once an accurate diagnosis has been obtained.

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