Any involuntary behavior that occurs abnormally may represent a seizure. Normal animals require a strong
stimuli to induce seizures eg.(Electric shock, drugs). Mildly epileptic
individuals need less strong stimuli to seize (fatigue, exercise, fever,
excitement, photic stimuli, estrus). The Very low seizure threshold
group - require no obvious stimuli at all, spontaneously seize (idiopathic
epileptics). Epilepsy
is a brain disorder characterized by a paroxysmal cerebral dysrhythmia
(EEG diagnosis), sudden in onset, which ceases spontaneously, and has tendency
to recur. Synonym = convulsion, epilepsy, fit. Seizures arise from abnormal
neuronal activity originating in the cerebral cortex. They are nonspecific,
sudden event characterized by involuntary muscle tone (tonus) or muscle
movement (clonus) or abnormal sensations or behavior lasting seconds to
minutes (ictal period). Any activity that is involuntary, episodic
and recurrent should be considered as a possible seizure disorder - i.e.
A. Loss or deranged
consciousness
B. Increased or decreased voluntary muscle tone (tonic seizure)
or movement (clonic seizure)
C. Visceral muscle activity
D. Episodic altered behaviour
Seizures are classified into several categories.
Generalized Seizures
Generalized seizures are further divided into two sub-types: major motor
seizures (grand mal) and absence seizures (petit mal). The major motor
seizure is the classic seizure. It is also sometimes called a tonic-clonic
seizure. A classic seizure can have three phases, the aura or prodrome,
the seizure itself (sometimes called the ictus) , and post-ictal (post-seizure)
behavior. Not all seizures have the three phases, but commonly they will.
Aura -
Seizures (neurological events) are often difficult to tell from fainting
spells (cardiovascular events). Classically, true seizures are preceded by
an aura, or special feeling associated with a coming seizure. Most commonly, the pet that has an aura
will act upset and anxious. He may seek attention from his owner or withdraw
and hide. The seizure is
typically followed by a post-ictal period during which the animal appears
disoriented, even blind. This period may last only a few minutes or may
last several hours. Fainting animals are usually up and normal within seconds
of the spell.
Psychic stage -
Restless, seek attention, hide, licking, salivating.
Ictus - Actual seizure period usually 1-2 min - visceral +
somatic motor activity. Animals are unconscious, have dilated pupils,
salivate, chewing activity, tonic and/or clonic, or rarely atonic in terms
of muscular activity. Visceral signs (defecation and urination) are common.
The most common time for a dog to have a seizure is when they are
relaxed and quiet. They may even occur from a sound sleep. Seizures can
occur anytime, but if they occur only when an animal is excited or exercising,
it may indicate a heart problem or low blood sugar.
The classic seizure itself
is called a tonic-clonic seizure. It begins with a stiffening of the muscles
(the tonic part). Usually the pet will fall to their side with the legs stretched
out and the head back. Once the seizure has begun, the pet is no longer
conscious even though his eyes may remain open. Sometimes they will vocalize
or the face may twitch. The vocalizations are involuntary and do not indicate
pain. Often he will drool excessively or he may urinate, defecate, or empty
his anal glands causing a foul smell. He has no control over these "accidents"
and is completely unconscious during the seizure. This tonic phase is usually
very brief (less than 30 seconds) and gives way to rhythmic movements (the
clonic part). Typically this consists of chomping of the jaws and jerking
or running movements of the limbs. Often he will not breath well during
the seizure and the tongue may turn blue. Even though the seizure may seem
to go on forever, the average seizure lasts less than 2 minutes. If the
seizure goes on much longer, we become concerned that the pet may go into
a continuous seizure (an emergency situation).
Seizures may be “isolated”
single seizure in 24 hrs, “cluster” seizure - 2 or more in a 24 hr period,
usually, the seizures start happening closer and closer together and the
dog gets more and more disoriented after each one, or ”continuous” in which convulsion
lasts 30 minutes or more with no recovery (status epilepticus). The fear is that the dog can go into
status epilecticus where he or she is in one prolonged seizure and brain damage
can be the result.
Post-ictal phase
Post seizure period when animal appears abnormal but not seizing.
Duration and characteristics highly variable between animals but similar
in a given animal. Often the pet appears blind and disoriented during
this post-ictal phase. He may pace or run about the house, bumping into
things as he goes. Sometimes they are excessively hungry and will devour
any food available. Rarely, a dog may behave aggressively during this period,
especially if they are restrained. While such aggressive behavior is rare,
it is important to recognize the possibility, especially if the dog is
large and there are children in the household. Usually this post-ictal
behavior begins to resolve within a few hours after the seizure and the
dog gets back to normal.
The post-ictal stage
may last few minutes to several
days. There is no correlation with severity of fit.
Status Epilepticus
Most seizures are brief and isolated, but sometimes they can be more
serious. The large-breed dogs tend to have clusters of seizures. In these
cases, the dog will have one seizure and recover from it. Then a few hours
later, they have another. They never completely recover before another seizure
strikes. Then they have another seizure, then another seizure, then another,
another, another.... Sometimes this culminates in a continuous seizure that
doesn't stop, a condition called status epilepticus. Occasionally status
epilepticus can arise out of the blue; the animal begins seizing and never
stops. Either way, this is a true emergency requiring immediate veterinary
care.
Focal Seizures
The other type of generalized
seizures in people is the absence or petit mal seizure. These are more common in cats than
dogs and may subdivided into simple or complex partial seizures. Petit mal seizures differ from
other seizures in several important aspects. First there is little movement
during a petit mal seizure. As the name "absence" implies, the person simply
loses contact with the world during the seizure. They stare blankly and
may blink but do little else. Absence seizures are also different in that
they probably represent a storm of inhibition rather than a storm of excitation
within the brain. This creates a unique EEG pattern. This means that very
different drugs are used to treat petit mal seizures. We're not sure if
petit mal seizures really occur in pets. Most of the seizures that are called
petit mal seizures in pets are actually focal seizures. In focal or partial seizures, the electrical
storm begins in an isolated area of the brain. If we are recording an EEG
at the beginning of such a seizure, we can see the storm starting in one
part of the brain. A focalal seizure may stay localized, or it may spread
and affect the whole brain causing a classic, generalized, tonic-clonic
seizure. In some cases, the aura preceding a generalized seizure may actually
be a focal seizure. The fact that the seizure starts in a local area suggests
that localized damage has occurred. As a result, when we see focal seizures,
we are more worried about diseases which will cause local damage, such as
a brain tumor or infection. focal seizures are further divided into two
subtypes (simple or complex) depending on where the storm originated and
how it affects the pet.
Simple partial seizures
These are associated with
localized motor or sensory abnormalities without a change in consciousness.
Focal facial twitching, head turning, or excessive pawing or biting at
a body part. Cyclic vomiting,
diarrhea, salivation (visceral epilepsy). Most commonly, the face is affected
resulting in twitching or blinking. This is usually limited to one side of
the face. If the seizure spreads a bit, other parts of the body on that side
will be affected. For example, the front limb may then begin to twitch and
buckle. During a simple focal seizure, the pet is usually alert and aware.
They may attempt to seek out their owner, confused about what is happening.
The seizure may stop there or it may generalize. If it generalizes, the pet
loses consciousness and has a classic grand-mal seizure.
Complex partial seizures
This type of seizure is predominantly behavioral with the animal involuntarily
howling, snapping, circling, etc. The abnormal behavior may be followed by
a generalized seizure. These have a significant change in behavior
accompanying the focal motor or sensory signs (also termed psychomotor
seizures). ”Fly biters, incessant howling, excessively restless. Complex
focal seizures originate in the areas of the brain that control emotions
and behavior (the temporal lobes) and are sometimes called psychomotor seizures.
When a seizure begins in one of these areas, the animal's consciousness
is altered and they behave bizarrely. They may run uncontrollably, engage
in senseless, repetitive behavior, or rarely fly into a rage. Other times,
we see bodily functions affected and the pet may have diarrhea or vomit.
Following a typical generalized seizure, unusual behavior (post-ictal behavior)
is common and may go on for hours. Complex focal seizures, like other types
of seizures, are typically very brief.
Most often, an animal behaving aggressively or acting strangely has a
behavioral problem or some other reason for the change in behavior. If, however,
these changes occur as discrete episodes, and the pet also has a generalized
seizure, we can be sure that this is a complex focal seizure and treat it
accordingly. People with complex focal seizures may experience hallucinations.
Some dogs have episodes of fly-biting where they appear to be biting at
imaginary flies around their head. Some of these may be complex focal seizures
although we cannot tell for sure.
Jacksonian epilepsy
(marching fit or jumping up and down like a kangaroo)
This begins in one group of muscles and spreads sequentially to others.
Stays ipsilateral until one entire side is involved.
Canine Cataplexy
the abrupt, temporary paralysis
of all postural muscles, suddenly dropping a group of excited dogs into a
silent heap on the floor. Attacks last only a few seconds, but can
occur hundreds of times a day.
There are many seizure patterns,
no two dogs are the same. Here are just a sample of what you may
encounter if your dog suffers from epilepsy.
These Videos curtesy of YouTube.com
