Healthy Dogs

Seizure Disorders in Dogs

A seizure is caused by an abnormal burst of electrical activity within the brain, commonly in one of the cerebral hemispheres. The electrical activity sometimes spreads out and involves other areas, including the midbrain.

A typical grand mal seizure is preceded by a period of altered behavior, called the aura. During the aura dogs may be restless and anxious, cry out, demand affection, or seek seclusion. The actual seizure normally lasts less than two minutes, and is characterized by collapse with rigid extension of the legs. The dog becomes unconscious and may stop breathing for 10 to 30 seconds. This is followed by rhythmic jerking of the legs (which resembles running or paddling). Some dogs also chomp, chew, drool, or urinate and defecate. As the dog regains consciousness there is a postseizure state characterized by disorientation and confusion. The dog may stumble into walls and appear blind. The postseizure state can persist for minutes or hours. Grand mal seizures are typical of epilepsy.

A focal motor or partial seizure is one in which the jerking or twitching is limited (at least initially) to a particular part of the body. A focal seizure usually indicates a specific brain lesion, such as a scar, tumor, or abscess.

Seizures are commonly associated with brain injury, encephalitis, heat stroke, brain abscess, brain tumor, stroke, poisoning, kidney failure, or liver failure. Seizures associated with a concussion frequently occur weeks or months after the head injury and are caused by a focus of scar tissue in the brain.

Postencephalitic seizures occur three to four weeks after the onset of encephalitis. Distemper, in particular, is characterized by attacks that begin with chomping, tongue chewing, foaming at the mouth, head shaking, and blinking, all followed by a dazed look.

Postvaccination seizures have been described in puppies under 6 weeks of age following inoculation with a combined distemper-parvovirus vaccine. This is extremely rare with current vaccines.

A bitch may develop low blood calcium levels after whelping and have seizures. A sudden drop in blood sugar (hypoglycemia) can also trigger a seizure. This occurs in newborn pups with cardiopulmonary syndrome. It can also occur in small-breed puppies who have not been fed adequately. A common cause of hypoglycemia is giving too much insulin to a diabetic dog.

Common poisons that cause seizures are animal baits such as strychnine, antifreeze (ethylene glycol), lead, insecticides (organophosphates), and chocolate. Seizures caused by organophosphates are preceded by drooling and muscle twitching. Exposure to a spray, dip, or premise treatment suggests the diagnosis.

There are a number of conditions that, while not true seizures, are often mistaken for them. Bee stings, for example, can cause frenzied barking followed by fainting or collapse. Cardiac arrhythmias can be mistaken for seizures because they cause loss of consciousness and collapse.