Seizures in Dogs
What causes seizures?
Normal neurons (brain cells) use electrical and chemical signals to communicate
with each other. This communication can either be excitatory which activates
the next neuron, or inhibitory which shuts off the next neuron. The mechanism
causing seizures in primary epilepsy is thought to be an imbalance in the
excitatory and inhibitory signals to the brain. Every dog (and person) has a
seizure threshold of neurological activity. Normally the excitatory and
inhibitory signals are in balance which keeps the electrical activity below the
seizure threshold. If the balance within the neurons shifts too far towards
excitation, too many cells may become excited and a seizure will result. This
excitation happens within the brain and is not related to your dog becoming
excited about his favorite activity. In fact most seizures occur while a dog is
at rest or asleep.
It is often difficult to determine what type of seizure your dog is having,
therefore, it is very important that you keep calm when your dog has a seizure
and observe him or her very closely. Since seizures rarely happen at your vets
office, a detailed written description or a video of the seizure may help in the
treatment and diagnosis of epilepsy.
The following is a list of seizure types in humans as defined by the
International Classification of Epileptic Seizures (ICES).
Classification of Epileptic Seizures:
I. Partial Seizures (also called focal or local seizures)
A. Simple partial seizures (consciousness is not impaired)
1. With motor symptoms
2. With somatosensory symptoms
3. With special sensory symptoms
4. With autonomic symptoms
5. With psychic symptoms
B. Complex partial seizures
1. Beginning as a simple partial seizure
a. With automatisms
b. Without automatisms
2. With impaired consciousness at onset
a. With automatisms
b. Without automatisms
C. Partial seizures with secondary generalization
II. Generalized seizures (bilateral without localized onset)
A. Absence seizures
1. True absence (petit mal)
2. Atypical absence
B. Myoclonic seizures
C. Clonic seizures
D. Tonic seizures
E. Tonic-clonic seizures (grand mal)
F. Atonic seizures
III. Unclassified seizures
Simple partial seizures
All partial seizures are characterized by onset in a limited area, or focus of
one cerebral hemisphere. The ICES classifies simple partial seizures as those
that are not associated with any impairment of consciousness. Although the
ability to respond may be preserved, motor manifestations or anxiety relating to
the seizure's symptoms may prevent your pup from responding appropriately.
There are many different types of simple partial seizures and your pup may
exhibit a wide range of unusual movements and behavior during a seizure. The
International Classification of Epileptic Seizures lists eighteen categories of
simple partial seizures. Some of the more common ones are:
Motor simple partial seizures alter muscle activity. Frequently motor seizures
Partial seizures with motor symptoms will cause stiffening or jerking of the
legs on one side of the body. Another common simple partial seizure is facial
twitching usually on one side of the head. Any muscle group may be involved.
Abnormal movements may be restricted to one body part or gradually spread to
adjacent areas on the same side of the body or both sides of the body with loss
of consciousness (secondary generalized seizure).
Sensory seizures cause hallucinations or illusions (distortion of a true
sensation). Hallucinations may remain restricted to one area or spread to other
areas. Hallucinations can involve any sensory modality, including touch (pins
and needles) smell or taste, vision and hearing (buzzing). Unfortunately our
dogs can't tell us what happened, even when consciousness is preserved during a
seizure, so we don't know for sure if our pups have sensory seizures.
Autonomic seizures cause vomiting, pain, hunger, warmth, and heart
Psychic seizures affect how dogs feel, think and experience things.
Psychic seizures can evoke spontaneous emotions like extreme fear or
aggression. A seizure should be suspected for any dog who exhibits brief
periods of unprovoked, extreme fear or aggression.
Complex partial seizures
Complex partial seizures cause impaired consciousness and arise from a single
region in the brain. Impaired consciousness implies decreased responsiveness
and awareness of self and surroundings, however consciousness many not be
impaired completely. In people, there is often no memory of what happened
during all or part of the complex partial seizure. Automatisms (automatic
repetitive movements) are common and may involve any body part. The mouth is
frequently involved and automations may include lip smacking, chewing or
swallowing. The limbs may also be involved with either simple movements
involving one leg, or with very complex coordinated movements involving
bilateral limbs. Some examples of complex movements are cycling or swimming
Seizures are classified as generalized seizures when the first clinical signs
indicate that both sides of the brain are involved in the seizure.
Consciousness may, or may not be impaired. Muscle involvement happens on both
sides of the body. The following are some types of generalized seizures:
Absence seizures (Petit Mal) are common in humans and are described as an
abrupt and brief loss of consciousness. True absence seizures are rare or at
least rarely recognized in veterinary medicine.
Myoclonic seizures are characterized by a brief, shock-like jerking of a
muscle or group of muscles.
Clonic seizures are seizures that involve rhythmic contractions of
muscles. Typically a dog will paddle or have jerking motion in the limbs and
Tonic seizures causes generalized muscle rigidity. In dogs, the limbs
are usually extended and stiff and the mouth may appear to be locked in an open
position. Some dogs do not breath during a tonic seizure or during the tonic
phase of a tonic clonic seizure.
Tonic-clonic seizures were formerly called grand mal seizures and are the
most common type of generalized seizure in dogs. Typically a dog will loose
consciousness, fall to his/her side with limbs extended and rigid. The mouth
may appear to be locked in an open position and the neck may be extended
extremely far back. All muscles in the body are contracted. The result of the
muscles in the lungs contracting forces air out which sometimes appears like
crying out. Breathing may stop for a short time and cyanosis (turning blue)
may occur. A dog may also urinate, defecate or express his anal glands during
this phase of the seizure. The tonic phase gives way to the clonic phase of the
seizure and paddling or jerking of the limbs and chewing movements begin. After
a minute or so, the muscles relax and the dog's body goes limp. At this point
the dog is deeply unconscious. Slowly they will regain consciousness, but they
may remain groggy and confused for several minutes after the seizure.
Some dogs have milder tonic-clonic seizures where consciousness is maintained
and muscle movement is not as violent.
Atonic seizures are, in a way, the opposite of tonic seizures. Instead
of the body going stiff, all muscle tone is lost. These seizures are sometimes
called "drop attacks" because when a dog looses all muscle tone he drops to the
As you can see from the descriptions, seizures are very complex. They may start
out as one type and progress to another. Knowing what type of seizure your dog
is having is not as important as knowing when your dog is in trouble. Please be
sure to ask your vet when you need to seek emergency treatment.
Berendt, M, Clinical Neurology in Small Animals-Localization,
Diagnosis and Treatment
Braund, K G; Clinical Syndromes in Veterinary Neurology
Clinical Epilepsy - American Epilepsy Society - 9/99
Plunkett, SJ; Emergency Procedures for the Small Animal Veterinarian
Thomas, W B Idiopathic Epilepsy in Dogs, Small Anim Prac Jane 2000,;184-206
Tilley, LP, The 5 Minute Veterinary Consult
©2003 -2007 Canine Seizures
All rights reserved
Last Updated March 2007
reprinted with kind permission from Sandie Snider