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Few events are as terrifying as witnessing your pet in the throes of a full seizure. One second, he looks perfectly normal, and the next, he’s on his side, eyes glazed, muscles twitching frenetically. He may even lose control of his bladder or bowels. A result of abnormal electrical activity in the brain, this episode may last only seconds, but when it happens, time seems to move in slow motion.
For some dogs, this is a one-time experience, but in most cases, seizures recur. If so, and if the abnormal electrical activity is caused by an underlying problem within the brain, the condition is termed epilepsy.
You might think that because epilepsy is fairly common, diagnosis and treatment are straightforward. Unfortunately, that’s not the case. Patients often show no signs; diagnostic tests are frequently negative; and, at least initially, the actual seizure events can be few and far between. These factors can contribute to a decision to take a wait-and-see approach, which can lead to problems later on.
As Dr. Michael Podell, a veterinary neurologist at the Animal Emergency and Critical Care Center in Northbrook, Ill., notes, “It’s important to identify—as much as possible—the underlying cause … Sometimes it’s easy to take the conservative approach … [but] unfortunately, it can often be a more serious problem.”
Consider, for example, one of Podell’s recent cases. “I saw an eight-year-old Shepherd mixed-breed who had her first seizure almost a year ago. The second one was several weeks later. Her regular veterinarian performed blood work and radiographs, and all was OK. She did not have another [seizure] until January. Then she had two more. Then the owners brought her to see us.” Though she looked normal, with no obvious neurological problems, says Podell, “she had a meningioma in her olfactory lobe the size of a golf ball.” Fortunately, these benign tumors, the most common type of brain tumor, can be treated with good success by veterinary neurologists.
Because there are so many potential underlying causes of seizures, the workup must be step-wise and thorough, a comprehensive attempt to parse the possible culprits: disorders originating within the brain (tumors; viral, bacterial or parasitic infections; strokes; head trauma) from those originating outside the brain. For instance, nutritional deficiencies as well as toxins like lead, insecticides, moldy foods and some human supplements can provoke brain changes that lead to seizures. Additionally, metabolic abnormalities such as liver or kidney disease can cause seizures, and some anesthetic agents and medications may also trigger them in sensitive animals.
The workup starts with a history, including information on vaccinations, diet, exposure to toxins, and the time relationship between seizures and other activities. In most cases, blood chemistry, a complete blood count and urinalysis will help systematically rule out many of the extracranial causes. If no underlying disease process is found and the animal is between one and five years of age, idiopathic (cause unknown) epilepsy may be diagnosed. If the dog is less than one year of age, he is more likely to have a congenital abnormality, and if he’s older than five to seven years of age, specific disorders of the brain are more common. In turn, these cases (as well as those with difficult-to-regulate idiopathic epilepsy) will require further workup, which may include an MRI and cerebral spinal fluid tap.
Regardless of age and the likelihood of finding idiopathic epilepsy, early treatment is important, because with each seizure, more nerve cells within the brain will begin to fire randomly. As Dr. Podell notes, “The brain’s threshold for seizure may lower on a constant basis.” In other words, each seizure makes it more likely that another one will occur. This in turn can make the seizures progressively more difficult to manage.
So, to the bottom line: In general, Dr. Podell suggests, “If a dog has had two seizure clusters [two or more seizures occurring over a short period of time, with the dog regaining consciousness in between] in a year, or two or more regular seizures within a six-month period,” he should receive appropriate diagnostic workup and treatment as soon as possible. Early diagnosis and treatment with anti-seizure medications where indicated are critical to a successful outcome.
To find out more about canine seizures and epilepsy, start with a visit to the Canine Epilepsy Network. 
Illustration by Natalia Martinez