How Is Epilepsy Diagnosed?

Boxer dog headCanine Idiopathic Epilepsy, the most common cause of seizures in dogs, is what is known as a diagnosis of exclusion.  This means that there is no specific test for the condition.  All other causes of seizures must be ruled out first.

This means that if your dog has idiopathic epilepsy, the various tests results will all come back as ‘normal’.  This might appear frustrating but a normal result can tell your vet just as much as an abnormal one.

Idiopathic epilepsy is most commonly diagnosed in dogs when the first seizure happened between the ages of 6 months and 6 years.  The frequency of seizures is variable but the dog normally appears completely normal between episodes.  It is rare for the first seizure to last more than a few minutes.  There are some breeds that are genetically prone to the condition, in particular:

  • Golden Retriever
  • Boxer
  • Border Collie
  • German Shepherd Dog
  • Italian Spinoni
  • Hungarian Vizsla
  • Petit Basset Griffon Vendéen

Other causes of seizures include:

  • Black and tan puppy with teddy bearEating a toxic substance (for example slug bait or mouldy food).  These are often severe seizures but do not normally happen again after they have been successfully treated.
  • Liver disease – particularly due to a portosystemic shunt which is an abnormal vessel, or vessels, which bypass the liver, leading to toxin build-up in the brain.  This most commonly happens in very young puppies, where a vessel which is supposed to seal off at birth fails to do so, or in middle-aged to older dogs where abnormal vessels form within the liver.  Dogs with this condition may have other signs of illness, such as weight loss, vomiting, stunted growth in puppies, and may have other neurological signs (e.g. head-pressing, disorientation, wobbly walking).
  • Meningitis – this tends to be a fairly sudden-onset problem which tends to get worse over hours to days.
  • Brain tumour – these tend to develop in older dogs (over the age of 6 years).  The frequency of seizures tends to increase as the tumour grows and other neurological signs may develop (e.g. head-pressing, difficulty walking, vision problems).
  • Head trauma – this tends to be a fairly obvious cause of seizures, although it is possible for seizures to develop further down the line.
  • Parasitic diseases – such as Toxoplasmosis and Neosporosis
  • Metabolic abnormalities – such as abnormal calcium levels and low blood sugar

Collapse due to heart problems can also look like seizures in some cases.

First diagnostic step

Blood samplesWhen you see your vet after your dog has had a seizure, the first step will be to ask you a number of questions as to exactly what happened.  The vet will then give your dog a full examination to check for other evidence of problems.  If your dog has fully recovered from the seizure, but something on the examination gives your vet a cause for concern, further diagnostics will be needed.

If everything appears normal, the seizure was not too severe and has never happened before, your vet may decide that further investigation is not absolutely necessary at this stage.

The first step will usually be blood tests.  A full haematology and biochemistry analysis will reveal any problems such as:

  • abnormal blood calcium
  • low blood sugar
  • increases in liver parameters
  • major inflammation which may be suggestive of meningitis, for example

More specific testing can be performed to test for parasitic causes and further liver function testing.

Further testing

CT scannerThe next step after blood testing will usually be some form of imaging of the brain.  This will check for problems such as a bleed on the brain, abnormal swelling, or a brain tumour.

MRI scans or CT scans are the only methods available for looking at the brain tissue.  They will show different things so you should speak to your veterinary neurologist about the best option for your dog.  Your dog will need to be anaesthetised for these as they need to stay very still for a long time.

What happens next?

After all this testing, if everything is normal, a diagnosis of idiopathic epilepsy is likely.  The decision then is whether or not treatment is needed at this stage.

If some abnormality has been shown on one of these tests, this should be investigated and treated appropriately by your vet.

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