Toxins That Can Cause Seizures in Dogs & CatsMarch 15, 2018
What is a Seizure?
The word seizure, convulsion, attack, or fit describes a sudden abnormal electrical event in the brain that temporarily interrupts normal brain function. Chaotic electrical activity replaces the normal electrical signals coming from the brain cells.
There are many different diseases known to cause seizures in animals. Anything that can change the function of the neuron within the brain may produce a seizure. Your veterinarian or veterinary neurologist determines the cause of the seizures through a complete physical and neurological examination plus appropriate diagnostic testing.
What Causes a Seizure?
The cause of seizures is usually classified into two categories; extra-cranial and intra-cranial. Extra-cranial causes come from outside the brain but affect the brain through the action of toxins or metabolic dysfunction. Toxin exposure is an uncommon cause for seizures but should be carefully considered. Ingestion of some plants, moldy foods, chocolate, an artificial sweetener called xylitol, drugs (including inadvertent ingestion of human medications), heavy metals (i.e. lead), pesticides (i.e. snail bait) and some chemical agents (i.e. antifreeze) can all lead to seizures. Routine blood work is needed to look for metabolic causes of seizures such as low blood sugar, electrolyte abnormalities, hypoxia, hyperlipidemia and liver or kidney problems.
Intra-cranial disorders that cause seizures include congenital malformations (hydrocephalus, lissencephaly), degenerative diseases (storage diseases), immune-inflammatory diseases, infectious agents (viral and fungal), cancer (brain tumors), severe trauma, and vascular disorders (strokes). Intra-cranial causes are usually diagnosed by brain imaging and analysis of cerebrospinal fluid.
An MRI is necessary to look inside the brain and cerebrospinal fluid collection, a CSF tap, is necessary to evaluate for infections, inflammatory diseases, and some kinds of cancer (such as lymphoma). Pets that are five and older are at a higher risk for cancer. Prior to pursuing more advanced testing such as an MRI and CSF tap, chest x-rays +/- abdominal ultrasound should be considered to screen for cancer. If cancer is found on these screening tests, pursuing costly anesthetic procedures may not be desirable.
This is the most common type of seizure. It is characterized by falling over, loss of consciousness, and/or stiff limbs followed by paddling movements, +/- jaw chomping, drooling, urination and defecation.
These seizures are sometimes called psychomotor seizures. They are variable in appearance and can be characterized by anything from simple facial twitching or staring off into space, to complex behaviors like suddenly running around or biting at imaginary flies.
This is when either of the above types of seizures happens repeatedly (2 or more times) in a 24-hour period.
The post-ictal phase can last from minutes to days. This is the period of time after a seizure has occurred when your pet is still not acting normal but is not actively seizing. It is often characterized by disorientation, poor balance, and pacing. Some animals become very thirsty, hungry or vomit. They can also become aggressive. Do not interact with your pet if he/she becomes aggressive. If he/she is not him/herself, they can harm people and other pets during this period.
The Three Phases of Seizures
Most seizures occur in three stages. The first part of the seizure, called the ‘aura’ often is not noticed. Owners who have dealt with seizures in their epileptic pets are often aware of certain changes in their pets’ behavior prior to a seizure. The pet often shows signs of apprehension, restlessness, nervousness, or salivation. Some can be clingy while others may act aloof.
The second stage is the ‘ictus’. The ictus usually lasts for 1-3 minutes. It often seems longer to an owner. During the seizure, the animal usually collapses on its side and has a series of violent muscle contractions that cause the body to be rigid and the legs to paddle. Loss of consciousness, salivation, involuntary urination and defecation may also occur in more severe seizures. A less common form of milder seizures occurs without loss of consciousness with the animal developing stiffness, uncontrolled trembling and attempting to crawl or move to the owner. There is no standard type of seizure and other variants do occur.
The period immediately following the seizure is the ‘post-ictal’ phase. It usually lasts less than an hour but may last many hours or as long as 1-2 days. Some pets are confused, disoriented, restless and temporarily blind during this period. They are usually tired, but typically want to eat and drink.
What should you do if your dog or cat has a seizure?
Seizures are very frightening and scary to pet owners, especially when it is the first seizure. Owners should take certain steps during a seizure to prevent injury not only to themselves but also to their pets. Keep in mind that dogs and cats do not experience pain during a seizure, or even remember it, as they are unconscious during the event.
• Ensure your pet is on the floor away from objects (corners of coffee tables). Do not allow the pet to fall off furniture or down stairs.
• To prevent choking, make sure that collars or leashes do not get caught on protruding objects.
• Keep your hands away from the mouth! Animals are unconscious during typical seizures. They have no control over their mouth and jaw muscles and may bite anything put in their mouth.
• Dogs can not swallow their tongues despite what you may have heard. Do not attempt to restrain the dog or pull the tongue during a seizure.
• Some pets will vocalize, salivate, urinate or defecate during a seizure. Their limbs may become rigid and they may paddle. These actions are involuntary.
• Most seizures last 1-3 minutes and are not life threatening. If the pet has repeated seizures and fails to regain consciousness between the seizures, or if a single seizure lasts longer than 5 minutes, it is in status epilepticus. This is an emergency and your pet needs to be seen by a veterinarian immediately. If your veterinarian is closed, you should go to the nearest emergency hospital. You can pull your pet onto a blanket and then lift the blanket to get them in the car for transport.
Diagnosing the Cause of Seizures
Your veterinarian will perform a physical and neurological exam and run the appropriate diagnostic tests to evaluate the cause of the seizures. Your veterinarian may refer you to a veterinary neurologist for additional testing and treatment. Tests that may be recommended include a CBC (complete blood count), chemistry profile (blood test), urinalysis, x-rays of the chest and/or abdomen, blood pressure, abdominal ultrasound, certain infectious disease titers (specific blood tests), CSF (cerebrospinal fluid) analysis, and MRI (magnetic resonance imaging).
Imaging of the brain is very important in diagnosing the underlying cause of seizures. Magnetic resonance imaging (MRI) is the gold standard to evaluate the brain. A computed tomography (CT) scan is no longer the recommended imaging test for the brain now that MRI is available. At VSH, the neurologists are intimately involved in performing and interpreting the MRI.
Treatment of Common Brain Diseases
Once the specific type of brain disease is diagnosed, appropriate therapy can be recommended. Treatment for brain tumors can include radiation therapy, surgery, anti-seizure medication, steroids and diuretics. Treatment for inflammatory-immune brain disease can include a combination of medications; these can include steroids, Imuran, Cytosar, cyclosporine and leflunomide. Treatment of vascular disorders (strokes) primarily includes time and supportive care. Treatment of infectious diseases is dependent upon identification of the specific organism.