16 Seizures – an introduction
Seizures originate from the brain. They are the physical manifestation of abnormal synchronous electrical discharge in the brain. The brain can be stimulated to do so by intracranial or extracranial causes. The chief purpose of clinical examination and laboratory tests is to differentiate the two.
2. Intracranial causes:
a. Structural: physical interruption of brain tissue; inflammation, malformation, degeneration, trauma, haemorrhage/ischemia or tumour
DESCRIPTION OF THE SEIZURE
1. Prodromal phase: change in mood or behaviour lasting 1–24 hours before seizure activity. Not classified as seizure activity, e.g. clinging to/following the owner, appearing anxious or restless. Usually only noticed by those familiar with the animal’s normal behaviour.
2. Pre-ictal phase (aura): commencement of seizure before impairment of consciousness occurs. Lasts seconds to minutes and is characterized in humans by altered sensory perception.
3. Ictus/fit/seizure: Commonly identified by a lack of consciousness/responsiveness and rhythmic involuntary motor activity lasting seconds to minutes. Variations exist. The point of describing or classifying a seizure is that different types may respond better to certain anticonvulsants and some seizures occur more often in specific diseases. A convulsion is a series of involuntary contractions of skeletal muscles. The term is commonly used as a synonym for seizure.
