Canine Epilepsy: Where We Are and Where We are Going

Speaker: William B. Thomas, DVM, DACVIM (Neurology), University of Tennessee

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Investigation of Cranial Cruciate Ligament Deficiency and Associated Surgical Interventions Using Computer Simulation
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High-Risk High-Reward Focus Areas for Research in Canine Gastroenterology: A Clinician-Scientists Perspective 
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Idiopathic epilepsy is the most common chronic neurologic disorder in dogs, affecting approximately 1-2% of all dogs. Idiopathic means that it occurs spontaneously, without an external cause, such as trauma, poisoning, metabolic diseases, or tumors. It is believed to be genetic in origin. Idiopathic seizures usually appear when the dog is between 1-5 years old. Seizures occur when there is excessive and/or hypersynchronous activity in the brain. As in humans, there are different types of seizures: generalized and focal. As in humans, medications are used in attempts to control them. Unfortunately, about 1 in 4 dogs do not obtain seizure control with meds.

There are several areas of canine research that include:

  1. Investigation of genetic factors
  2. Evaluation of the effectiveness of newer human drugs in dogs and the development of drugs especially for dogs
  3. Alternatives to drug therapy for seizure control

Generalized seizures are not difficult to identify, since they involve both sides of the brain. When a dog has a generalized seizure, the dog is not conscious and has abnormal limb movements including paddling, stiffening and even loss of movement.This may last for seconds to minutes.Once the seizure ceases, the dog is in the recovery stage as the brain waves are getting back to normal.This is called the “postictal” phase and the dog is disoriented with possible leg twitches, chewing, salivation, weakness, or loss of bladder/bowel control. The dog may not be breathing well. This can last for minutes to hours.

Focal seizures can be more difficult to identify, with the appearance that the dog is awake, but exhibiting inappropriate activities like barking, disorientation, tail chasing, “fly biting” movements or aggression. It is a single area of the brain that is experiencing disordered electrical activity.  There is no loss of consciousness. It is believed that the dog is seeing flickers of light during a “fly biting” seizure. These are types of unusual behaviors that can last from seconds to a minute.

"Status epilepticus" is a prolonged seizure, or a cluster of seizures, lasting greater than five minutes.This is an emergencyand the dog needs immediate medical attention.The consequences of untreated status epilepticus include elevated body temperature, low oxygen levels, and brain damage. Death is a possibility. Dogs who suffer with status or cluster seizures have a shortened lifetime to 8 years (considering average lifespan of a dog is 11).

Any dog that presents with seizures for the first time will need to have a medical workup that can include blood work, physical exam, EEG (electroencephalogram to read the electrical signals from the brain), spinal fluid analysis, and CT or PET scans. There are many other causes of seizures, such as brain tumors, stroke, and brain infections. Client awareness is paramount in diagnosis and treatment.

There are two drugs that are commonly used to treat canine epilepsy, but both have side effects and neither one can control all seizures. Phenobarbital was invented in 1912; potassium bromide was first used in the 1850s. Both of them can cause sedation, imbalance, weight gain, increased thirst and urination. Newer drugs are needed and there are trials with human medications ongoing; some of the ones mentioned were: zonisamide, levetiracetam, gabapentin, and pregabalin. Other treatments include vagus nerve stimulators, surgery and acupuncture.

In 2014, the AKC Canine Health Foundation launched the Epilepsy Research Initiative.

Dr. Thomas is a Professor of Neurology and Neurosurgery with a specific interest in brain surgery and the imaging of brain disease. His research interests include transcranial Doppler ultrasonography and treatment of epilepsy.

 

 

 
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