Wednesday, April 09, 2014

Seizures in Dogs

 

A seizure is the result of uncontrolled electrical brain activity and is manifested as involuntary movement of the animal’s body. What causes seizures? How do you diagnose the cause of the seizure? Is there a treatment available?

A seizure is the result of uncontrolled electrical brain activity and is manifested as involuntary movement of the animal’s body. It is often a sudden episode and can occur at any age of your pet. Seizures can vary significantly in severity and length, which sometimes makes them hard to notice. If a seizure is severe and lasting longer then 3-5 minutes, it can cause fluid build up in the brain and lungs and a rapid increase in body temperature that can cause internal organ damage. Seizures can occur as a local or generalised seizure.

There are usually three phases of seizure:
1. Aura is the first stage of seizure and may be absent. In this phase a dog can do things it usually doesn’t such as exhibiting bizarre behaviour, being unsteady on its feet, seeking owner’s attention and hiding.
2. Seizure follows aura and the pet develops symmetric and sustained contractions of legs with head twisted backwards. Drooling, vocalising and losing control of bladder/bowel may be observed. Seizure can last from under a minute to hours. The longer it lasts the worse the prognosis. Most seizures in dogs happen at rest and majority of them are mentally aware of what is happening.
3. Recovery phase often lasts 10-15 minutes and the dog may completely recover. During this phase, some dogs can be slower than usual, hungry, disoriented, and pacing or appear to be blind.

What causes seizures?

Different causes of seizures have different patterns. Generally speaking in dogs under one year old the most likely reasons for seizure are hydrocephalus (excessive build up of fluid in the brain) and portosystemic shunt (abnormal liver blood circulation). Dogs 1-5 years of age which are overall healthy usually suffer from epilepsy. Pets older than 5 years are likely to suffer from a tumour.

Depending on the location where they come from seizures can be subdivided into two groups;
• Extracranial (outside of the head) and
• Intracranial (the cause is inside of the head)

Extracranial causes are the result of metabolic imbalance in the body such as low blood glucose or calcium, terminal liver or kidney failure and poisons.
Intracranial causes are epilepsy, tumours, trauma, infectious (bacteria, virus, fungus), protozoa (Toxoplasma and Neospora), or immune mediated disorders.

How do you diagnose the cause of the seizure?

In some cases all that has to be done is a blood sample but some pets need more invasive procedures done such as CSF (cerebrospinal fluid) tap, toxicology panels, MRI or CT. Not all dogs need an extensive work up, it depends on the symptoms and severity of the seizures.

Is there a treatment available?

Many of the causes are treatable but the hardest part is to get to a correct diagnosis. In general the treatment involves:
1. Place intravenous catheter and collect a blood sample for full blood analysis
2. Administer anticonvulsant medication to control the seizure
3. Start the patient on intravenous fluids and remove toxins (if any)
4. Adjust the treatment depending on blood results
5. Hospitalisation with monitoring and supportive treatment

The intensity and extensiveness of the treatment depends on how severe the problem is. If the dog suffers from seizures 3-4 times a year and they are mild no treatment is needed. However if fitting is more frequent or fits come in clusters this indicates that medications are needed.

The type of medication that needs to be used depends on the cause of the seizure. For example it is pointless to treat only the seizures if the patient has an underlying problem that has to be treated first (e.g. Toxoplasmosis).

Three most commonly used medications with anticonvulsant activity are diazepam, phenobarbital and potassium bromide. Human medications can be used but the cost can be significant.

Phenobarbital and potassium bromide are often effective for long-term seizure control. They do not resolve the underlying problems that made the dog fit but increase a threshold for fitting which means that the intensity of the fits has to be higher to be manifested as a fit in a dog.

Special instructions for pets on phenobarbital & potassium bromide

All pets on phenobarbital should be tested for phenobarbital levels twice a year if doing well under the treatment. If not, they will need more frequent blood tests until a good result is achieved. Liver enzymes should be monitored while the pet is on phenobarbital since it may cause liver damage. Some pets can still have an occasional fit while on medications, but if it happens two or three times a year and the fits are mild, this is still considered satisfactory.

Pets that require potassium bromide have similar requirements like the ones on phenobarbital (six monthly blood testing if doing well).