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+==Introduction==
+
+* Seizures are paroxysmal changes in cerebral cortex electrical activity that start abruptly, end suddenly and have a tendency to recur.
+* Epilepsy is the occurence of recurrent seizures.
+
+==Pathophysiology==
+
+* Seizures occur when there is imbalance between exitatory and inhibitory processes. This may be due to :
+** Inadequate neuronal inhibition.
+*** Major inhibitory neurotransmitters include GABA and glycine.
+** Excessive neuronal excitation.
+*** Major excitatory neurotransmitters include aspartate and glutamate.
+
+===Proposed Mechanisms===
+
+* Defective feed-forward inhibition or feed-back initiation of inhibitory neurons in cortical circuits.
+** Recurrent excitatory collaterals may be formed.
+* Changes in membrane properties of neurons.
+** These may include changes at:
+*** Potassium, sodium, chloride and calcium ion channels
+*** GABA receptors
+*** Nicotinic acetyl choline receptors
+*** NMDA receptors
+**** Activation.
+* Changes in the ionic microenvironment.
+
+===Seizure Development===
+
+# At the onset of a seizure, abnormal neurons undergo prolonged depolarisations.
+#* These depolarisations are associated with the rapid firing of repeated action potentials.
+# Depolarisation of abnormal neurons recruits adjacent neurons with which they are connected.
+# The electrical discharges of the large number of neurons involved become linked together.
+# A storm of electrical activity results, causing a clinical seizure.
+# Seizures may then spread:
+#* To adjacent areas of the brain.
+#* Through established anatomic pathways to other distant areas.
+
+==Nomenclature==
+
+* '''Status epilepticus''' is the term used to describe
+** A seizure lasting longer than 5 minutes, or
+** A collection of discrete seizures without full recovery of consciousness.
+* '''Cluster seizures''' occur when 2 or more seizures are experienced in a brief periods, but the patient regains consciousness between them.
+* Three classes of seizures are recognised:
+*# Generalised seizures
+*# Focal seizures
+*# Focal generalising seizures
+
+===Generalised Seizures===
+
+* Generalised seizures may be:
+** Idiopathic
+** Due to an intrinsic disorder in the brain
+** Aquired
+*** Due to some lesion in the brain
+** Reactive
+*** Due to some extracranial disoerder, for example a toxin or metabolic disorder.
+
+====Clinical Signs====
+
+* Initial clinical signs show involvement of both cerebral hemispheres.
+* Generalised seizures result in:
+** Change in consciousness
+** Motor activity
+*** Tonic-clonic seizures are most common in dogs and cats.
+** Autonomic signs
+* The body's energy utilisation can increase to around 250% of the normal value during a generalised seizure.
+
+====Stages====
+
+# Prodrome
+#* The animal experiences an indication of a forthcoming seizure.
+#* This occurs hours to days before the event itself.
+# Aura
+#* This is the very start of the seizure.
+#* Behaviour changes may be apparent.
+# Ictus
+#* The seizure "proper".
+# Postictal phase
+#* Consists of transient neurological and behavious changes, which can last from hours to days.
+
+====Idiopathic Epilepsy====
+
+* Idiopathic epilepsy is a relatively common cause of generalised seizures in the dog.
+** NOT in the cat.
+* The onset of seizures is between 1 and 5 years of age.
+* The condition presents as recurrent, unprovoked seizures, with no specific cause.
+* There are no neurological defects between episodes.
+* Seizures tend to start as generalised seizures, with no aura.
+
+====Acquired Generalisd Seizures====
+
+* Other general seizures may be acquired.
+* Seizures can occur at any age, but generally occur in animals younger than 2 years and older than 5 years.
+* Causes may include:
+** Intracranial disease
+*** Neoplasia
+*** Trauma
+*** Infection
+*** Inflammation
+** Extracranial disease (also known as "reactive epilpsy").
+*** Electolyte disorders
+*** Metabolic disorders
+*** Toxicity
+
+===Focal Seizures===
+
+* Almost always an acquired disease.
+* Active diseases often progress to become more general.
+** Cause generalised seizures.
+
+===Simple Focal Seizures===
+
+* Onset occurs in a limited area of one cerebral hemisphere.
+* No impairment of consciousness.
+
+=== Complex Focal Seizures===
+
+* Arise in a single brain region, but cause impaired consciousness.
+
+==Causes of Acquired Seizures==
+
+{| border="3" cellpadding="8"
+!width="150"|'''<u>Cause</u>'''
+!width="400"|'''<u>Examples</u>'''
+
+|-
+|Neoplasia
+|Primary or metastatic
+|-
+|Inflammatory
+|Distemper, FIP, FeLV/FIV, rabies, cryptococcosis (cats), toxoplasmosis
+|-
+|Traumatic
+|Immediate or delayed
+|-
+|Vascular
+|Feline ischaemic encephalopathy, thromboembolism, hypertenstion
+|-
+|Anomalous
+|Hydrocephalus
+|-
+|Metabolic
+|Hepatic encephalopathy, uraemia, hyperparathyroidism, hypolycaemia, hyperkalaemia, hypocalcaemia, hypoxia, acid-base disorders, hyperthermia
+|-
+|Toxic
+|Lead, organophosphates, metaldehyde, strychnine
+|}
+
+==Investigation of Seizures==
+
+* It must first be determined whether seizure activity is in fact a seizure, rather than a non-epileptic paroxysmal event, for example:
+** Syncope
+** Exercise-induced weakness
+** Obsessive-compulsive behaviour
+** Narcolepsy
+* Idiopathic epilepsy may be differentiated from secondary or reactive seizures by considering:
+** Age of onset
+** Breed disposition
+** Partial seizures or asymmetrical post-ictal signs
+*** These suggest a discrete lesion.
+** Older animals (>5 years) may be more likely to have an acquired aetiology.
+** Younger animals (<6 months) may be more likely to have toxic or metabolic causes.
+* Useful tests include:
+** Metabolic screening
+** Haematology
+** Serum biochemistry
+** Urinalysis
+** Serology.
+** Bile acid stimulation test
+** Serum lead
+** MRI and CT scanning, and CSF analysis, help rule out cancer.