Seizures in dogs: causes & signs
Published on 15 Oct 2021
Seizures are sudden transient involuntary events. Although they are not uncommon in dogs, witnessing your pet having a seizure can be distressing. There are multiple causes of seizures, both metabolic diseases and diseases affecting the brain tissue itself.
The most common type of seizures are generalised motor seizures however focal seizures or focal seizures that become more generalised can also be seen. Status epilepticus describes prolonged seizure activity and represents a medical emergency.
The treatment and prognosis of a seizure disorder is dependent on the underlying cause.
Signs of seizures in dogs
A seizure is defined as a sudden transient event. Epileptic seizures represent excessive, synchronous activity of neurons in the brain and this activity results in the transient signs we see in our pets. It is as if the brain has a circuit overload and the part of the brain that is overloaded, most commonly the front or the middle of the brain, then translates to the signs that we can see.
The signs of seizures are very variable and can be specific to an individual, however most animals that seizure will have the same signs every time.
The most common signs of seizures are:
- short episodes of convulsions or involuntary movements affecting a single limb, the muscles of the face or jaw or all limbs, frothing at the mouth, limb rigidity and urination or defaecation.
- Most animals will fall to the side during a seizure however some may be sitting or even standing.
- Alterations in behaviour such as aggression, avoidance or hiding away can also be seen.
- Most animals lose consciousness during a seizure; this manifests as a lack of responsiveness to their surroundings including touch and sound.
In some cases, seizures can be silent where no external signs of movement are seen. This may manifest as your dog staring off into space and being unrousable during the event.
The pre-ictal period refers to the period immediately prior to a seizure. People with seizure disorders often know they are going to have a seizure as they learn to identify what the ‘’pre-ictal’’ signs or changes are. This can be more difficult in dogs as they can’t talk! Some things you may see are agitation, pacing, being more ‘’clingy’’ or other alterations in behaviour. The duration of these signs is also variable.
Follow a seizure there is a post-ictal period. The signs during the postictal period are again very variable and so is the duration. Things that may be seen are disorientation, seeming to be a little ‘’out of it’’, walking as if drunk, bumping into things, blindness, circling, behavioural changes such as aggression or being very lethargic. Animals may have abnormalities on the neurological exam for up to 7 days post a seizure. There is an enormous amount of energy expended by the body during a seizure and as a result, it is not unusual for animals to take time to get back to normal following an event.
Types of seizures in dogs
The most common and recognisable type of seizure is a generalised motor seizure. This is a result of abnormal neuronal activity that originates from both sides of the front of the brain (cerebral hemispheres) and manifests as symmetrical, generalised signs such as tonic-clonic contractions of the limbs (convulsions), jaw chomping and salivation, loss of consciousness and urination and defecation.
Focal seizures occur secondary to excessive activity in a specific area of the front or the middle of the brain and as such tend to manifest as asymmetric signs such as focal limb movement, facial twitching or behavioural change. Dogs may or may not appear conscious during focal seizures. If the seizure activity spreads from the original focal area to both sides of the front of the brain, the seizure can progress to become generalised ad progress to a generalised motor seizure.
Cluster seizures refers to 2 or more distinct seizure events within 24 hours where the patient regains consciousness between these events. These can be focal or generalised.
Status epilepticus is generally defined as prolonged seizure activity lasting over 5 mins or 2 or more seizures in succession without regaining consciousness in between. Prolonged seizure activity can result in significant damage to the brain and other organs in the body such as the heart, muscles, kidneys and lungs and may result in permanent and irreversible effects. Status epilepticus is a life-threatening veterinary emergency and requires immediate intensive veterinary care
What causes seizures in dogs?
The causes of seizures can be largely divided into two broad categories – disease inside the brain (intracranial) or diseases outside of the brain (extracranial).
Intracranial disease is further divided into idiopathic epilepsy or structural epilepsy.
Idiopathic epilepsy is an overarching term that includes genetic epilepsy, suspected genetic epilepsy and epilepsy of unknown cause. Most animals with idiopathic epilepsy will be normal in between events. Males are more commonly affected than females and the majority of dogs with idiopathic epilepsy will have their first seizure between 1-5 years of age. A genetic mutation associated with idiopathic epilepsy in dogs has been identified in Lagotto Romagnolo dogs, however a large number of other breeds are overrepresented in cases of idiopathic epilepsy where a genetic cause is suspected. These include Labrador Retrievers, German Shepherd Dogs, Golden Retrievers, Bernese Mountain Dogs, Belgian Tervurens, Vizslas, Keeshonds, English Springer Spaniels, and Border Collies.
Structural epilepsy refers to seizures that are provoked by abnormalities of the forebrain or midbrain including; infectious and non-infectious inflammatory disease (meningoencephalitis), cerebrovascular accident (similar to a stroke in people), space occupying lesions such as brain tumours, brain trauma, degenerative disease of the brain, altered metabolism of the brain cells or developmental abnormalities (eg. hydrocephalus). Structural epilepsy can be accompanied by other neurological abnormalities in between seizures.
Extracranial causes result in symptomatic or reactive seizures which are the normal brains’ response to alterations in brain cell function due to metabolic disease, intoxications, or nutritional deficiencies. Seizures may be reversible if the underlying cause is rectified if there has not been irreversible damage to the brain cells.
Metabolic disease that may result in seizures includes liver dysfunction (hepatic encephalopathy), severe kidney disease (renal encephalopathy), low blood glucose levels (hypoglycaemia), high or low blood salt (hypernatremia, hyponatremia) or high or low blood calcium levels (hypercalcaemia, hypocalcaemia).
Nutritional deficiencies such as thiamine deficiency can result in a seizure as well as other neurological signs.
Intoxications such as heavy metals (lead), pesticides (snail bait, strychnine, permethrins), caffeine or chocolate intoxication (methylxanthines), toxins associated with ingestion of mouldy substances (mycotoxins), artificial sweeteners (xylitol) that results in low blood glucose levels or illicit drugs (eg. methamphetamines) have been associated with seizures. Symptomatic or reactive seizures are often accompanied by other physical exams or neurological abnormalities in between seizures.
In some cases, it can be difficult to determine if the ‘sudden event’ is a seizure or not. Other causes of sudden onset or episodic events may include; syncope (similar to fainting in people), movement disorders, acute vestibular episodes (disease affecting the balance system), sleep disorders (narcolepsy/cataplexy) or collapse from severe systemic disease.
What should you do if your dog has a seizure?
The first thing to remember is that when your dog is having a seizure, they are not aware of what it happening, nor are they aware of their surroundings. It is best to try not to touch your pet during this time and especially avoid the head to prevent injury to yourself. Generally speaking, the best thing to do is to try to prevent your dog from suffering further harm. This can be done by removing additional dangers such as preventing them from falling (off the bed/couch/ down the stairs/ into the pool), and remove any objects from around them that could cause harm (chairs, small tables etc). If it is safe to do, you may also carefully place something soft under their head. Take care not to put your hands/ fingers near their mouth to prevent the possibility of being bitten.
Seizures can be very scary to witness, and it can be difficult to recall what has happened or how long the event may have lasted when asked by your veterinarian. We would recommend stating a timer to record how long the event was and if possible, record a video of the event, as both of these things can provide very useful information to your veterinarian.
Most epileptic seizures are short (less than 1- 2 mins) and animals recover back to normal within a short period of time. If this is the case, we would recommend continuing to monitor your dog at home until such time as you can make an appointment to see your veterinarian. If your dog has; a prolonged seizure (over 3-5 mins) or 2 or more seizures in succession without regaining consciousness (status epilepticus), over 2 seizures with 24-hour period (cluster seizures), has a very prolonged postictal recovery or they appear significantly neurologically altered following the seizure, immediate veterinary attention should be sort.
Seizures are a serious condition, and, in all cases, veterinary advice should be sort.
The general investigation that your veterinarian may recommend includes; a thorough history, physical exam and neurological exam and basic screen blood and urine tests (complete blood count, serum biochemistry – including blood calcium, salt and glucose levels and a thyroid level). Following this, more specific investigation may be recommended such as urine drug screening, liver function tests, infectious disease blood tests and ultimately advanced brain imaging (MRI scan).
Treatment and prognosis for seizures is highly variable and dependent on the underlying cause. In most cases, seizures have a cumulative effect, the more seizures that occur the more likely it is for your dog is to continue to have seizures. Seeking veterinary advice early will allow for the appropriate diagnosis and treatment plan to be implemented.