Seizures 1 Flashcards
Seizure
sudden, short lasting and transient event. It does not imply that the event is epileptic
Epileptic seizure
Manifestation of excessive and/or synchronous activity of neurons in the brain, resulting in a
transient occurrence of certain signs.
Clinical signs for seizures
Loss or altered consciousness
Altered behavior
Autonomic disturbance
Altered tone or movement
Altered sensation
Epilepsy
disease of the brain characterized by an enduring
predisposition to generate epileptic seizures.
having at least two unprovoked epileptic seizures >24 h apart
Reactive seizure
occurring as a natural response from the normal brain to a transient disturbance in function (metabolic or toxic in nature)—
reversible when the cause or disturbance is rectified. A provoked seizure can be considered as being synonymous with a reactive seizure.
Cause of reactive seizure
Toxin
Metabolic disorder
Causes of epileptic seizures
Idiopathic epilepsy
Structural epilepsy
Unknown cause
Categories for reactive seizure causes
Metabolic - hypoglycemia, hepatic or renal encephalopathy
Toxins - meds, plants, food, rodenticide, illicit drugs, misc: alcohol, mycotoxins, bee, excessive Na
Idiopathic vs structural epilepsy
Structural is the result of an intracranial lesion leading to seizures. Examples include brain tumor, stroke, encephalitis, hydrocephalus, or head trauma.
Terminology for seizures
Focal
Generalized
Focal that can become generalized
Pre-ictal period
Prodrome - sensory, motor, behavioral abnormalities preceding a seizure, could be long durations, normal EEG
Aura - abnormal sensation that precedes seizures, short duration, EEG abnormal
Ictus stage
The epileptic seizure itself stage
Post-ictal period stage
Transient, brain restores to normal function
Interictal period
Time between resolution of post-ictal signs and onset of next ictus
Generalized epileptic seizure phenotype
Tonic-clinic - alteration between clonus and tonus Tonic – increased tone
Clonic – convulsions
^^ all common phenotypes
Myoclonic – jerking movements of a muscle group Atonic – loss of tone
Status epilepticus
20-30 minutes of continuous seizure activity
Practically - seizure ≥5 minutes in duration
≥2 seizures without recovery in between
Syncope
Lack of blood flow to the brain
What causes epileptic seizures
Reactive epileptic seizures
Epilepsy - idiopathic, structural, unknown
reactive epileptic seizures
Hepatic Encephalopathy
Hypoglycemia
Electrolyte abnormalties
Toxin
Can cause changes in resting mem potential
Too much excitation or too little inhibition
Hypoglycemia
Patients need glucose
Na/K pump fails = paradoxical excitation of cell = seizure
Serum osmolality equation
= 2Na + glucose/18 + BUN/2.8
Hypoatremia
Common change that leads to seizures w sodium
Increased Na intracellular = change in resting membrane potential = paradoxical neuronal excitation
Neuronal swelling from water following concentration gradient
Hypocalcemia
Ca does not directly contribute to RMP but is needed to keep Na channels in check
Decreased Ca = more Na into cell easier = change in RMP and paradoxical excitation
Too much excitation
Glutamate
Acetylcholine
Na inactivation gate
Mycotoxins
Glutamate agonist - bind to glutamate receptors opening Ca or Na channels = depolarization = seizures
acetylcholine
Organophosphate cross BBB and bind to acetylcholine esterase = increase in acetylcholine = depolarization = SLUD signs = seizures can result with higher levels of toxin
Drug for organophosphate seizures
Atropine
Inactivation gate
Prevents sodium from entering cell
Pyrethins binds to those sights = more Na in cell
Too little inhibition
Cl channels
K channels
4-aminopyridine
Blocks K channels = inhibiting hyperpolarization leading to excessive excitiabiltiy and seizures
Common condition in cats that leads to same effect
Chloride
Strychnine - interferes w binding of glycine aka inhibitory NT in chloride channels
Bicucuilline - plant neurotoxin, similar fashion
