Diagnosis
It's imperative that the cause of seizures in a dog is determined because there may be an underlying disease that should be treated. The causes of seizures can be broken down into Primary Epileptic Seizures, Secondary Epileptic Seizures and Reactive Epileptic Seizures.
Primary Epileptic Seizures are seizures that occur when there is no underlying structural cause and are thought to be genetically influenced. Other terms used to describe Primary Epileptic Seizures are idiopathic epilepsy, genetic epilepsy, inherited epilepsy or true epilepsy. It is estimated that 65% of dogs with the onset of seizures between the ages of 1 year and 5 years have primary epilepsy.
Unfortunately there isn't a test to determine whether or not a dog has primary epilepsy and therefore the diagnosis is based on ruling out other diseases that can cause seizures.
Secondary Epileptic Seizures are caused by an abnormal process in the brain such as hydrocephalus (an accumulation of spinal fluid on the brain), trauma, tumor or infection. If secondary epilepsy is suspected your vet may recommend a spinal tap or diagnostic imaging of the brain.
Reactive Epileptic Seizures are seizures that are caused by metabolic dysfunction such as hypoglycemia (low blood sugar), hypothyroidism, low calcium, liver failure, toxins, kidney failure and electrolyte imbalances.
A minimum diagnostic exam will consist of:
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History of the seizures - When
a dog has partial (focal) seizures, there is more reason to suspect an
underlying disease. In addition, dogs with idiopathic epilepsy
usually have a post ictal period so the absence of post ictal symptoms
may indicate an underlying disease. |
|
History of parents and
siblings (if it is known) - Epilepsy and several other conditions that
can cause seizures are hereditary so knowing if other pups in the line
have seizures is helpful in the diagnosis. |
|
Complete neurological exam -
To determine if there are any neurological deficits between seizures. |
|
Complete blood count - To
determine if there are signs of infection. |
|
Chemistry Panel - To check the
function of liver, kidneys and other vital organs. |
|
Urine Analysis - Useful to
rule out some forms of kidney disease and some metabolic disorders. |
|
Bile Acid Test - Testing for
liver diseases such as portosystemic shunts. |
|
Complete Thyroid Panel - To test for hypothyroidism |
Other factors that your veterinarian will consider, are the age that your dog began having seizures (see chart at the bottom of this page) and the breed of your dog. A genetic basis for idiopathic epilepsy is strongly suspected in the Beagle, Belgian Tervuren, Keeshound, Dachshund, British Alsatian, Labrador Retriever, Golden Retriever and Collie. Other breeds may have a genetic basis also, however, adequate testing has not been completed.
In most cases these tests are sufficient but if a dog's first seizure happens when they are very young or very old, if there is a reason to suspect another cause based on the information contained in the history, or if the seizures don't respond to medication, your veterinarian may refer you to a neurologist so that other tests can be done.
Other tests may include some or all of the following:
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MRI or CT brain scan - will rule out diseases such as brain tumors. Both an MRI and a CT scan are similar to x-rays. They are not painful, but because they require the patient to be motionless for 15 minutes or so, dogs are given a general anesthesia. |
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Spinal Tap - Looks for infectious diseases such as distemper. The procedure involves placing a needle in the space around the spinal cord and removing a small amount of spinal fluid for analysis. This is painful and the patient must be perfectly still for the time it takes to do the procedure, so it is also typically done under general anesthesia. Complications are uncommon and there are rarely any ill effects from these tests. |
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Antibody titers - Identifies specific causes of an infection |
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Toxin Tests- Can determine if there is a toxin or poison present |
The following chart (from Clinical Syndromes in Veterinary Neurology) lists the most likely causes of seizures based on the age of onset:
|
Age of Onset |
Rare |
Most common causes |
|
Before 8 months |
Idiopathic Epilepsy |
Developmental Disorders Encephalitis or Meningitis Trauma Portacaval shunt Hypoglycemia Toxins Intestinal parasites
|
|
Age of Onset |
Seldom |
Most Common Cause |
|
8 months to 5 years |
Developmental disorders Trauma Encephalitis or meningitis Acquired hydrocephalus Neoplasia (tumor) Portacaval shunt Hypoglycemia Electrolyte disturbances Hypothyroidism Toxins |
Idiopathic Epilepsy |
| Age of Onset | Seldom | Most Common Causes |
| Above 5 years |
Idiopathic Epilepsy Trauma Encephalitis or meningitis Acquired hydrocephalus Serious Liver disease Hypocalcemia Electrolyte disturbances Hypothyroidism
|
Neoplasia (tumor) Degenerative disorders Vascular disorders
Hypoxia (lack of oxygen in Hypoglycemia |
Berendt, M, Clinical
Neurology in Small Animals-Localization, Diagnosis and Treatment
Braund, K G; Clinical Syndromes in Veterinary Neurology
Meyer & Harvey; Veterinary Laboratory Medicine-Interpretation and
Diagnosis
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
