seizures and epilepsy Flashcards
seizures have a variety of different?
presentations and triggers
seizures are?
an acute, excessive, uncontrolled neural stimulation
seizures are a…._____ not a _____
symptom NOT a disease
epilepsy is a …..
disease! characterized by recurrent, unprovoked, chronic seizures
-trigger cannot be identified so the seizures occur for unknown reasons (if trigger identified—> can be prevented and disease can be treated)
etiology of seizures?- unprovoked
2/3 idiopathic
1/3 genetic (not clearly understood)
etiology of seizures?- provoked
known trigger, secondary to other diseases or infections
- trauma, infection or other CNS insult
- febrile (especially kids)
- metabolic seizures: hypoglycemia: decreased glucose, hypoxia: decreased O2, electrolyte imbalance
classification of seizures? (focal vs. generalized)
focal: localized in 1 hemisphere, abnormalities originate within a small group of neurons, may spread to a large group
COMPLEX partial= loss of consciousness
SIMPLE partial= no loss of consciousness
generalized= originates in both hemispheres, several subtypes
pathology of seizures?
- resting membrane potential is about -70mv. inside of neuron is 70mv less than outside
- AP travel along axon until they reach a synapse, during this time the neuron is depolarized and becomes more positive than outside
- each AP that fires results in depol and repol of neuron
- amplitude of AP in seizures is INCREASED (neurons get more positive) and the frequency is INCREASED- more AP fired
in seizures, neurons are…
hyper-responsive and are triggered by a stimulus (known or unknown) and fire excessively
ACUTE increased neuronal discharge in cerebral cortex and hippocampus
epileptogenic focus=
in cerebral cortex and hippocampus, triggered—> appearance of seizures
inhibitory neurons in seizures?
neurons that are responsible for releasing NT’s that hyperpolarize the neuron (make it more negative, harder to reach threshold)
—> normal inhibition is overwhelmed for several minutes—> abnormal movement and behaviour
AP spreads to all neurons!
when does a seizure end
when the discharge is eventually controlled, inhibitory neurons eventually control the excessive neural activity
what does intermittent contraction-relaxation phases mean?
there are spastic, rigid movement
once the inhibitory neurons kick in…
ALL neurons are SUPPRESSED
—-> resulting in decreased activity and movements (patient may appear sleeping or even comatose d/t depressed CNS
complications of a seizure (to do with oxygen and glucose!)
- excessive discharge from neurons increases O2 demand and glucose (glucose is utilized by brain for energy)
- however, d/t constant muscle stimulation, muscles are using large supply of the bodys ATP
- so muscle and brain are competing for resources
- if seizures lasts longer than a few minutes… brain will not receive enough oxygen, glucose, or ATP to function properly, neural deficits created
- body cannot supply adequate o2 and ATP to both the hypercontracting muscles and the brain—> inadequate brain perfusion—> hypoxia and lactic acidosis ***DAMAGE!
