Broadly seizures in dogs and cats fall into two categories, those with an identifiable cause, such as toxin exposure, infections, tumours and metabolic diseases (thyroid disease, kidney disease, or high blood pressure), and those where no cause can be identified and can only be treated symptomatically.
Differentiating the two groups is very important as the seizures may be curable.
Seizures are characterised by involuntary muscle movements. These vary from minor twitching of a limb, to generalised motor seizures with complete loss of consciousness. Minor seizures can be differentiated from Ďdreamingí whilst your pet is asleep as if you wake them up, the tremors should stop.
It is important to identify non-epilepsy causes of seizures, because treating these causes may lead to seizure prevention
Common tests include:
Some of the more common causes of seizures are:
Epilepsy is a syndrome where there are recurrent seizures. It can be caused by an inherited functional problem of the brain (idiopathic epilepsy) or can be the result of trauma to the brain that causes residual brain damage (acquired epilepsy).
What is the most common form of Epilepsy?
Idiopathic epilepsy is the most common form for dogs. Affected dogs will have repeated episodes of seizures with no demonstrable cause. In between seizures, the dogs are normal or may go through a phase where they are a little quiet or vague. This vagueness usually does not last long, but can be different for each individual. With idiopathic epilepsy the onset of seizures usually starts between 1 and 3 years of age. In most breeds, the younger the age of onset, the more difficult the seizures are to control.
For acquired epilepsy, the time of onset is usually between 6 months and 3 years after the causing event. Sometimes is it is impossible to determine the cause.
The seizures generally seen with idiopathic epilepsy are usually about 1-2 minutes duration and are called tonic-clonic, where muscles contract and relax. Some dogs may have a more generalised type of seizure where they have uncontrollable trembling or muscle rigidity. Seizures due to idiopathic epilepsy recur at regular intervals, with weeks or months in-between. As the dog ages, seizures can occur more frequently or can occur in groups or clusters. Seizures may at times be very severe, and can cause a lack of oxygen to the brain resulting in further brain damage, or even death.
Seizures lasting longer than 5 minutes, or cluster seizures (more than one seizure in 24 hours), is called Status Epilepticus, and is considered an emergency. Prompt veterinary treatment is required.
Epilepsy is a diagnosis of exclusion. In other words if all the tests above are normal then a presumptive diagnosis of epilepsy is made.
Anticonvulsant therapy is the only treatment for idiopathic or acquired epilepsy. Some animals with very mild or infrequent seizures may not need any treatment at all. Sometimes treatment does not eliminate the seizures altogether, but decreases their severity, duration and increases the time between seizures. Prior to anticonvulsant therapy, other causes of seizures do need to be ruled out as discussed before. Heart disease, for example, can lead to syncope (fainting), which can mimic a seizure.
For animals with occasional seizures medciation may only be given at the time fo a seizure, to try and avoid a seizure cluster.
If animals have frequent seizures then medication will be given on a daily basis to try and stop the seizures occuring
The following points are important in managing pets who are prone to seizures
During seizure episodes
Always keep a diary of your pets seizures. Record how often they occur, and the duration of the episodes. This allows us to determine if the disease is progressing and if we need to change the treatment regime.
Many anti-convulsant medications over time promote their own metabolism. In other words over time the body learns to eliminate these drugs more effectively. This means the required dose slowly increases over time.
For this reason we generally do a blood test every 6 months to measure the level of drug in the blood. This allows us to detect a falling level before seizures recur.
In most instances we want to know the lowest level that occurs in the blood. For this reason we take the sample just before you would give the next dose. If for example you give the tablet at 7am and 7pm, we may take a sample at 6pm.
Occasionally some of these medications can increase liver enzyme levels. For this reason we generally test liver function on the same blood sample. Early detection of liver problems will allow us to change medication before your pet becomes affected clinically.
A few pets will show signs of marked sedation on these medications. This is common when you first start giving them, but the signs will generally resolve after a few weeks. If the signs donít resolve the dose may be too high. We now need to take our blood sample at a different time. We want to know the highest level achieved so take a peak sample: usually 4-6 hours after you give a dose of medication.
If this all sounds confusing donít be alarmed. We will tell you exactly what needs to be done when. If you have any concerns please ring us, so that we can discuss them with you.