Pathophysiology
Seizures represent an uncontrolled, paroxysmal discharge from the neurons in the brain. Any involuntary event that is brief
and episodic should be considered a possible seizure. A typical seizure is characterized by 4 stages. The Prodrome stage is characterized by altered behavior preceding the seizure by hours to days. This stage is rarely recognized in animals. The
Aura occurs minutes before the seizure and is characterized by restlessness, attention seeking, hiding, whining, salivating, or
trembling. The Ictus refers to the actual seizure. It typically lasts seconds to a few minutes, though owners frequently overestimate the duration.
The Postictal period generally lasts minutes to hours, and is characterized by disorientation, restlessness, temporary blindness, and occasionally
aggression.
History Taking
Accurate description of the episode from start to finish helps to rule out other seizure-like conditions such as syncope,
vestibular disease, tremors, pain, stereotypies, dreaming, or narcolepsy. It is important to ask about the presence of, and
symptoms related to, auras, ictus, and post-ictal periods, as well as their approximate duration. The presence of salivation,
urination, defecation, and chewing motions should be also be determined as these are frequently associated with seizures.
Owners should be questioned about whether any localizing signs could be identified. Did it start with one leg, or on one particular side of the face? Questions should also be directed towards previous illnesses or injuries that could have resulted in seizures. For example,
a history of vomiting or respiratory signs might suggest distemper as a possibility. A history of heart disease could suggest
that syncope, rather than a seizure is the problem. Intoxications should be ruled out through careful history taking, particularly
with regard to lead paints, home remodeling, and so on. Vaccination status should be confirmed, particularly if distemper
is a possibility. Problems associated with littermates or related animals could suggest congenital or hereditary disease.
Questions should also be asked about relationship of episodes to feeding, as patients with hepatic encephalopathy may have
seizures in response to high protein meals. Finally, indoor/outdoor and free-roaming status should be ascertained to find
out if the possibility exists for unknown toxin exposure or trauma.
Physical Examination
A complete physical exam is important and may help to differentiate systemic versus intracranial causes of seizuring. Skull
conformation may suggest the presence of congenital diseases like hydrocephalus. Cardiac auscultation may reveal the presence
of arrhythmias or murmurs, potentially associated with syncopal episodes. The presence of (or history of) respiratory signs
could suggest the possibility of syncopal episodes secondary to hypoxia (eg. laryngeal paralysis) or canine distemper in the
young dog. Gastrointestinal signs could go along with lead toxicity, distemper, or metabolic disease. Careful attention should
be taken to evaluate for the possibility of trauma or toxin exposure, particularly in pets allowed to roam freely. Petechiation
could suggest rickettsial diseases like RMSF, which has been associated with seizures secondary to vasculitis. Fundic exam
should always be performed, as many systemic diseases such as neoplasia, FIP, toxoplasma, cryptococcus, distemper, and hydrocephalus
are associated with ocular manifestations such as retinal plaques, papilledema, or anterior uveitis. Nasal discharge in the
older pet may suggest the presence of a nasal tumor that has broken through the cribiform plate. Various endocrinopathies,
such as hypo- or hyperthyroidism have also been associated with seizures, the former as a result of hyperlipidemia leading
to hyperviscosity and atherosclerotic plaques, and the latter as a result of hypertension.
The neurological exam is a very important component to the diagnosis of seizure disorders, as it may help to identify focal
or multifocal lesions indicative of structural or systemic disease. In animals with idiopathic epilepsy, the neurological
exam is frequently normal, though abnormalities such as weakness, lethargy, or disorientation may be present during the post-ictal
period, and transient blindness or aggression are occasionally seen. In animals with post-ictal abnormalities, neurological
exam should be repeated interictally to see if abnormalities have resolved.
