Canine Seizures

Out of the blue, your dog rolls on his side and starts to shake. What’s going on?
By Michael A Wong DVM, January 2015, Updated May 2016

Charlie, a four-year-old Shih Tzu mix, held his head low and cried out when touched. His regular veterinarian performed blood tests and took X-rays, none of which revealed a reason for the neck pain. After discussing possible causes—a slipped disk and meningitis among them—the vet prescribed a trial of antibiotics and pain medication. At first, Charlie improved, but within a few days, his pain seemed to increase. Then he had a seizure.

His people rushed him to a local emergency clinic, where he was admitted. The clinic kept Charlie overnight to stabilize him, and the next day, transferred him to our practice, Southeast Veterinary Neurology in Miami, Fla.

Charlie was minimally responsive. When we examined him, we saw that he tended to turn his head to the left and didn’t react to stimuli on the right side of his body; he didn’t blink when touched near the right eye or when his right eye was approached. After a magnetic resonance imaging (MRI) and spinal fluid analysis, we had a diagnosis: encephalitis. Treatment was started immediately.

Seizures—a manifestation of uncontrolled electrical activity in the cerebral cortex—are the most common canine neurological disorder. The cerebral cortex is made up of cells (neurons) that communicate with each other via electrical activity. A seizure happens when that electrical activity becomes excessive or uncontrolled.

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Seizures are classified as either focal or generalized, with the latter being the most frequently seen. In a classic generalized seizure, all four legs become stiff and the dog lies down or falls over before losing consciousness and convulsing. During a convulsion, many dogs will vocalize and salivate; some will urinate or defecate. The seizure may last anywhere from a few seconds to several minutes, or longer.* Focal seizures are milder and only affect one part of the body—part of the face, or one leg.

Any disturbance that either increases the electrical activity in the brain or decreases the control mechanisms that prevent seizures can cause these episodes. There are three basic types of disturbances: extracranial (problems outside of the brain that secondarily affect the brain), intracranial (physical or structural problems with the brain itself) and idiopathic epilepsy.

Low blood sugar, severe liver or kidney disease, electrolyte abnormalities such as low calcium, and toxins/poisons are among the causes of extracranial seizures. All of these conditions are relatively easy to identify with blood and urine tests.

Intracranial causes include brain tumors, strokes, encephalitis/ meningitis (as in Charlie’s case), head injury or a malformation such as hydrocephalus (“water on the brain”). Diagnosing these conditions requires an evaluation by a neurologist, an MRI of the brain, and possibly a cerebrospinal f luid analysis. Seizures experienced by certain breeds of dogs—including Boxers, Yorkshire Terriers, Maltese and other terriers—are more likely to have an intracranial cause.

Idiopathic epilepsy—seizures with no known cause—is the most common reason for recurrent seizures, and is the result of an inherent hyperexcitability of the neurons of the cerebral cortex. In general, dogs with idiopathic epilepsy are between one and five years of age when they have their first seizure, which is usually of the generalized type. In between seizures, they’re completely normal, as are their neurological examinations.

Seeing your dog have a seizure can be distressing, but the primary thing you need to do is to remain calm. Do not put your hands near your dog’s mouth, as in the throes of a seizure, he’s not aware of his actions and may unintentionally bite you. Keep your dog in a safe area where he is unlikely to hurt himself, moving him away from stairs, pools or other hazards. If this is your dog’s first seizure, take him to your veterinarian immediately.

Your vet will likely start with a series of blood and urine tests to evaluate the liver, kidneys, electrolytes and other internal organs, looking for an extracranial cause. A consultation with a veterinary neurologist and an MRI may be recommended if the blood tests are normal, if your dog is younger than one or older than six, or if he acts abnormally between seizures.

Diazepam (Valium) or midazolam, fast-acting drugs, will halt a seizure in progress. Depending on the cause and the dog’s response to treatment, longer-acting anti-seizure medications are also prescribed. Among these are phenobarbital, potassium bromide, levetiracetam (Keppra), zonisamide (Zonegran) and felbamate (Felbatol); each has both positive and potentially adverse effects. Your veterinarian or neurologist will discuss which medication makes the most sense for your dog. For many conditions, including idiopathic epilepsy, medication can help reduce the frequency and severity of seizures, but some seizure activity can still be expected.

Seizures are indeed scary, but understanding their causes and knowing what to do when they occur go a long way toward successfully coping with them.

*Ed. note: According to other sources, a seizure that lasts more than five minutes or that reoccurs three times in a 24-hour period should be considered an emergency.

Article first appeared in The Bark, Issue 80: Winter 2014

Michael Wong, DVM, is one of fewer than 200 board-certified veterinary neurologists in North America. He founded Southeast Veterinary Neurology in 2010.