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
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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
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.