Primary Inherited Epilepsy

by Roy F. Dvorak


There are many things that can cause a seizure in a person or a dog. Epilepsy is a subset of one of the many things that cause seizures. Just because a dog has a seizure does not mean that the dog has epilepsy. Seizures come in two "flavors" or types, primary and secondary. Some external influence or some outside stimulus causes secondary seizures. With secondary seizures, the source is known. We discuss several types of secondary seizures(e.g., distemper, brain tumor) as they relate to Korie (see Brain Tumor, Head Injury, Lyme’s Disease and Rocky Mountain Spotted Fever, Distemper, and Environment - Toxins ). Primary epilepsy, also known by the names of idiopathic or genetic or inherited or true epilepsy, has no known source. A genetic factor is highly suspected when seizures occur in dogs 1 to 3 years of age. Korie’s seizures began at 14 months of age or at 1.1667 years - near the beginning of the accepted age range.

Before going into any detail about epilepsy, it is best to define the act of epilepsy itself, the seizure. By way of the thesaurus that comes with this word processor, the word "seizure" has the following synonyms: fit, convulsion, attack, epileptic fit, paroxysm, etc. A seizure begins unexpectedly and ends suddenly and does occur again. Epilepsy is referred to as being idiopathic when the seizures it causes have no known origin and the seizures do recur. Idiopathic, from the Greek language, is a combination of "idio" meaning "one’s own or personal" and "pathy" meaning "disease". So idiopathic really means "one’s own disease". One veterinarian that we talked to stated that idiopathic is really a fancy term for saying "we do not know".

A seizure falls into two classifications - partial and generalized. For the most part, we have witnessed a small number of Korie’s seizures that may be considered as partial - the last 2 seizures she had on the infamous 1996 Memorial Day weekend, 1 on the 1996 July 4th weekend, and 16 in January 1997. These seizures consisted of biting and salivation ("foaming" at the mouth), and they stopped suddenly. They lasted between 15 to 45 seconds. It was extremely interesting to observe these petit mal seizures that occurred in January 1997. When the seizure activity commenced, we could feel a "shock wave" or contraction of sorts progress down her spine from her head to her tail.

As the uncontrolled discharge of neurons in the brain spreads, a partial seizure can become a generalized seizure. A generalized or grand mal is the most common form of a seizure. It is interesting to note that ‘mal’, meaning bad or wrong or ill, is generally used as a prefix, for example "maladroit" (bungling). The seizure itself is broken into 3 stages, the pre ictal, ictal and post ictal. Ictal is from the Latin ‘ictus’ meaning attack. Korie’s grand mal seizures have lasted anywhere from 1 minute up to 7 minutes. She has urinated during some seizures; released her anal glands during some seizures, and has done both. She has not defecated during any seizure, yet.

In a text book seizure, the dog will lose consciousness, will paddle or go through running movements, will bite and will salivate. In a seizure caused by strychnine poisoning for example, stiffening of the legs is observed but there is no leg movement or paddling. If you have seen Korie’s video, you know that she paddles quite vigorously in her seizures.

In his exemplary text Veterinary Neuroanatomy and Clinical Neurology, Dr. Alexander de Lahunta of Cornell University, mentions that all dogs have a seizure threshold. A seizure occurs when this threshold is exceeded. Dogs with a low seizure threshold are divided into 2 groups - stimulus and non-stimulus. In the stimulus group, seizures may be caused by some external influence such as hormones, (e.g., estrogen which can lower the threshold to seizures in parts of the brain), fatigue or injury, and hyperventilation. Since Korie is spayed, the estrus cycle is not a factor. Korie and her "little" brother chase each other around the back yard and house until they almost collapse. This occurs on a daily basis, more so in the warmer weather, so fatigue is not a factor. Korie has not experienced hyperventilation, not even on a hot summer day after strenuous playing. The majority of her seizures occur when she is at rest or sleeping. Excluding Korie’s Memorial Day seizures, 80% of her seizures occur when Korie is sleeping or at rest. Considering our observation, we can rule out the stimulus group of seizures.

In the non-stimulus group, the seizures occur spontaneously, or as stated earlier, they have a sudden beginning. According to Dr. de Lahunta, the non-stimulus seizure is typical of many idiopathic epileptics.

The table shown below is similar to the one that appears on page 329 - Table 18-1 - in Dr. de Lahunta’s text Veterinary Neuroanatomy and Clinical Neurology. The table lists the 3 categories that cause seizures and the agents under each category. Please note, that there are no agents listed under idiopathic epilepsy - they just happen.

Hypoglycemia Degeneration’s (poisons)  
Hypocalcemia Inflammations (distemper, encephalitis)  
Hypoxia or Hyopoxemia Neoplasia (brain tumor)  
Hepatic Encephalopathy or
Liver Disease
Renal (kidney) disease    
Gastrointestinal disease ("garbage" poisoning)    
Tick bites    

Dr. de Lahunta also discusses the "interictal" period in his text. The interictal period is the time frame between seizures or clusters of seizures. We consider Korie to be in an interictal period, yet she does not show any of the symptoms that a seizure prone dog may display. The interictal symptoms are listed here:

  • paresis - the diminished ability to move muscles or body parts voluntarily.
    Korie is very coordinated as she trots and runs in her back yard.
  • infarct - localized tissue death.
  • lesions - any disease induced abnormality of tissue or tissue function. A
    lesion could be an abscess, ulcer, or tumor. We have not found
    any surface infarct or lesions during Korie’s weekly grooming.
  • neoplasia - formation of a tumor or tumors. Assuming a brain tumor, the MRI
    showed none and any tumor growth would show progressive
    deterioration of all activity. Korie has not slowed down from the
    day she arrived at our Schnauzer home.

These symptoms are usually the result of one of the extracranial agents that are discussed in detail below. If Korie were suffering from any of these interictal symptoms, we would be giving her special medication to control the affliction. Korie’s anticonvulsant medications are mentioned in the web page titled Korie Lynn's Background. Korie is a bundle of energy and loves to play, chase squirrels, bark at dogs on the other side of the fence, play, ... .

In the many years since Korie’s first seizure, she has shown no signs of any of the above abnormalities. Dr. de Lahunta states in his text that "Dogs with idiopathic epilepsy do not have interictal signs."

In the next several sections, we will briefly describe the agents mentioned in each category in the table above and show how they do not relate to Korie.

1. Hypoglycemia.

A dog with hypoglycemia (low blood sugar) usually has seizures prior to feeding when their blood sugar or glucose levels are at a low level. The signs of hypoglycemia depend on 1) level of the blood glucose and 2) the rate the glucose level drops. Some of the causes of hypoglycemia are:

  • a pancreatic tumor that produces an insulin like substance
  • liver disease
  • cortisone deficiency
  • diabetic dogs that obtain an insulin overdose

The majority of Korie’s seizures occur when she is at rest. Seizures are occasionally observed in hunting dogs during periods of excessive activity. Korie, and our other Standard Schnauzers, are in their crates in the bedroom when we are not home. On Saturday and Sunday they are constantly doing something, and after 3 or 4 hours of doing something they are usually tired, sometimes exhausted from their activities. Korie has never seizured after any period of excessive activity or stress. To repeat, Korie’s seizures occur when she is at rest. We can safely say that Korie’s seizures are not due to hypoglycemia.

2. Hypocalcemia.

This is an endocrine disorder (affects electrolyte, calcium, magnesium, and phosphorous) that is characterized by low levels of calcium. Typically the acceptable range of calcium levels from the blood serum chemistry is in the range of 8.5 to 11.0 (mg/dl). Section 6 on hyperkalemia contains a table which lists the potassium and calcium levels from Korie’s blood work.

Loss of appetite in a dog will cause the calcium levels to decrease which in turn may cause seizures. Some dogs may develop muscle weakness early in the disease. At no time have we ever observed Korie to stumble or fail to go up 10 stairs in less than 3 leaps. Korie has a very healthy appetite and always eats the food that we place in front of her. Another symptom of hypocalcemia is cataracts. As we stated in the section on distemper, Korie’s eyes were CERFed in October 1996 and each year thereafter, and no cataracts were found. We can safely say that Korie’s seizures are not due to hypocalcemia.

3. Hypoxia or Hypoxemia.

Hypoxia (Hypoxemia) is a condition of low blood oxygen levels that results in reduction in the capability of the red blood cells to carry oxygen. It may be the result of a disease of the lungs that prevents an adequate supply of oxygen getting to the brain thus causing seizures. As we have stated many times in this document, Korie loves to play and run. Dr. Scott Carpenter has listened to her heart and lungs many times and has never indicated any problems or any minor item that would lead him to say, "let’s watch that". We can safely say that Korie’s seizures are not due to hypoxia.

4. Hepatic Encephalopathy or Liver Disease.

Excess ammonia in the blood from liver disease may be a cause of seizures. Measurements of blood ammonia provides a truly reliable test to identify a dog with liver disease. According to the UC Davis School of Veterinary Medicine Book of Dogs, "It is the only test that can determine whether clinical signs of central nervous system dysfunction can be attributed to liver disease (hepatic encephalopathy)". Of all the signs of liver disease, anorexia (reduced food intake) is the first to appear and it too is a sign of hepatic encephalopathy.

Korie has had 6 panels of complete blood work done since her first seizure on June 1, 1995. All test results show no elevated levels of ammonia in her blood. Korie would eat all day, if permitted, but her larger than normal appetite is due to her medications. We can safely say that Korie’s seizures are not due to hepatic encephalopathy or liver disease.

5. Renal (kidney) disease.

Kidney disease and kidney failure are two different conditions. The kidney fails when it is unable to perform its function of cleansing the blood of impurities. A kidney disease may hamper the kidneys from performing but it is still able to remove impurities from the blood. Uremia is a condition when there are high levels of urea nitrogen in the blood, other nitrogenous waste products in the blood, and the body pH falls below 7.0. The bodies buffering mechanisms that are under the control of the kidneys regulate the acidity in the blood and the body itself. High acidic levels of the body or acidosis may be the cause of seizures. The seizures are the result of the buildup of toxins (high nitrogen levels) in the blood. Uremia occurs at the terminal stages of kidney failure. It may also cause the body temperature to lower and may increase the respiratory rate. On page 270 of the UC Davis School of Veterinary Medicine Book of Dogs, the authors state "Failure to initiate therapy in a timely manner will result in irreversible damage to kidney tissue and ultimately death".

Part of a complete blood work-up is the chemistry analysis. Included in that are the blood urea nitrogen (BUN) and creatinine, the two most common tests used to evaluate kidney performance. The normal BUN range for an adult dog is 10 to 25 (MG/DL) with the average being 17.5. The range for the creatinine is 1.0 to 2.2 (MG/DL) with the average being 1.6. The following table shows Korie’s BUN and creatinine levels. The first two blood tests were done in the summer of 1995 when Korie started seizing.

BUN (10-25)
Creatinine (1.0-2.2)
Glucose (60-115)
June 3, 1995 19 0.9 (10?)
August 8, 1995 15 0.9 (10?)
November 4, 1996 14 0.9 102
April 3, 1997 13 0.9 96
September 23, 1997 12 0.9 90
March 2, 1998 12 0.8 93

If Korie has or had any type of kidney failure these levels would be much higher. We have never initiated any type of therapy for a kidney disease or kidney failure. We can safely say that Korie’s seizures are not due to any type of kidney disease or kidney failure.

6. Hyperkalemia

Hyperkalemia is the condition of a high concentration of potassium in the blood. Another term for this condition is Addison’s disease. Going back to the complete blood work, we show Korie’s potassium levels (MEQ/L) in the following table. Note that the level for November 1996 is higher than previous levels. This is a result of the addition of 1.5 cc of potassium bromide that she receives once a day as part of her drug therapy. The average potassium value is 4.7.

Potassium (3.6-5.8)
Calcium (8.5 - 11.0)
June 3, 1995 4.9 11.3
August 8, 1995 4.1 8.0
November 4, 1996 5.1 9.3
April 3, 1997 4.4 9.6
September 23, 1997 4.5 9.4
March 2, 1998 4.5 9.3

The heart rate of a dog suffering from hyperkalemia may be slower than normal. The condition may show itself as a generalized weakness in the dog and the condition becomes worse with exercise. To repeat ourselves again, Korie is constantly playing with her "little" brother and they love to beat up on each other in typical Schnauzer play. By performing this natural exercise, they tire each other out running and playing and running and playing. Korie shows no signs of weakness in any way, shape, manner, or form. We can safely say that Korie’s seizures are not due to any excessive levels of potassium in her blood.

7. Hyperlipoproteinemia.

Dr. de Lahunta’s text Veterinary Neuroanatomy and Clinical Neurology has a small paragraph on this disorder but we were unable to find this disorder as it is spelled or described in any of the other veterinary texts we own. He states that "defective lipid metabolism" causes this disorder. Lipids are classified as simple and complex. Simple lipids do not contain fatty acids. Complex lipids are essentially fatty acids and include glycerides, glycolipids, phospholipids, and waxes (ear wax). Lipids can combine with proteins to form lipoproteins. Apparently this disorder does not properly break down the fatty acids in the blood and the affected dog may have seizures. Dr. de Lahunta states that the Miniature Schnauzer is the most commonly affected dog.

A high concentration of lipids (triglycerides) in the blood is known as hyperlipemia. Other clinical signs of hyperlipemia include dullness, poor appetite, rapid loss of body condition. Korie is far from being dull, especially when she pulls the stuffing out of almost any stuffed toy we give her. Her appetite is quite voracious as we stated previously, and her health is excellent. We can safely say that Korie’s seizures are not due to any excessive amounts of fatty acids in her blood.

8. Gastrointestinal disease ("garbage" poisoning).

Decaying and rotten garbage may be a breeding ground for staphylococcal and or botulism toxins. These may cause central nervous system stimulation, i.e., seizures. We are quite concerned when Korie or any of our other pups are chewing on something that does not look like a chew toy or stuffed toy. We take it from them immediately and replace it with one of their toys. We keep daily garbage under the sink away from them and the garbage can itself is in the garage. Our pups only eat what we give them. The examination of Korie’s stool sample would show if she has consumed any strange substance. Her stool samples have not shown anything out of the ordinary. Her last stool sample check was on November 11, 1996. We can safely say that Korie’s seizures are not due to any ingestion of decaying garbage.

9. Tick Bites.

We discussed tick bites and two of their diseases - Rocky Mountain Spotted Fever and Lyme Disease. We maintained Korie’s coat in a show coat until the spring of 1997. However, she is still groomed on a regular basis - furnishings brushed, nails clipped, teeth brushed, etc. All of our Standard Schnauzers are inspected and bathed often, especially when we return from any extended trip, for example, after the journey to California for the SSCA National Specialty in September 1996. At no time have we ever found a tick on Korie. We can safely say that Korie’s seizures are not due to any tick bite.

10. Toxoplamosis (Toxo)

The information that we obtained on Toxo comes by way of the internet. Toxo is a disease caused by a germ (protozan parasite - Toxoplasma gondii) and the most likely places of contact are cat feces, raw meet and uncooked vegetables. Approximately half of the people in the U.S. have the Toxo parasite, but the disease is dormant. This parasite is similar to giardia in that once a dog has giardia, it is dormant and may flare up at any time to affect the dog. Toxo has many symptoms and included in these are muscle spasms and seizures (neurologic difficulties). The symptoms worsen and the patient may go into a coma if the disease is not treated properly. The 2 most common drugs used in the treatment of Toxo are the combination of sulfadiazine and pyrimethamine. Depending on the dog’s reaction to these drugs, other drugs may be substituted - clindamycin, dapsone, or doxycycline. In the winter of 1994 and 1995, Victoria B.C. experienced the world’s largest outbreak of Toxo ever reported.

We do not have Korie on either sulfadiazine or pyrimethamine and she has never taken either of these drugs. For that matter, neither of us have ever been diagnosed with or suspected of having Toxo. We can safely say that Korie’s seizures are not due to Toxoplamosis.

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