Flashcards in Epilespy Deck (57)
What is a seizures?
The clinical manifestation of an abnormally excessive and hypersynchronous activity of neurones located predominantly in the cerebral cortex
Why do epileptic seizures manifest in different ways?
It depends on their site of origion and subsequent spread.
How does epileptic seuizures occur?
The cortical discharges can be transmitted to the muscles, causing twitches or convulsions
What are the 3 classification of seizures?
What is the generalized classification of seizures?
With initial activation of neurones throughout both hemispheres
What is the partial classification of seizures?
With the initial activation of a limited number of neurones in a part of 1 hemisphere
What is secondary generalized seizures?
A partial seizure that later spreads to involve the majority of the 2 cerebral hemispheres)
What is a tonic-clonic seizure?
Typical type with stiffening, fallng and jerking of the body --> example of generalized seizure
What occurs with a complex seizure?
Type of partial seizure were there is seizure activity with change in awareness of surroudnings
What is the manifestation of partial seizuredependent on?
Depends on the site of origion
What is electroencephalogram?
Electroencephalography (EEG) uses scalp electrodes to record the electrical activity along the scalp produced by the firing of neurones within the brain.
What is status epolepticus?
Status epilepticus (SE) is a life-threatening condition in which the brain is in a state of persistent seizure
What has to occur for a person to be defined as having status epilepticus?
More than 30 mins continuous seizure activity OR
Two or more sequential seizures spanning this period without full recovery between seizures
What is the complication of status epilepticus?
SE is a medical emergency because the longer a seizure lasts, the less likely it is to stop on its own
SE confers greater risk for future unprovoked seizures
What is the treatment for status epilepticus?
Injection of GABAa receptor agonist
What is a definition of epilepsy?
Epilepsy can then be defined as a condition in which seizures recur, usually spontaneously; a single seizure episode is not considered as epilepsy, i.e. 2 or more unprovoked seizures
What caues to much neuronal activity and therefore seizures?
Excitation --> to much
Ionic—Na+, Ca2+ influx
Neurotransmitter—glutamate, aspartate release
Inhibition (too little)
Ionic—CI- influx, K+ efflux
What is the normal status quo of the brain?
Normally in the brain very small numbers of brain cells are active at any given time --> tightly focused the activity and not allowed to spread.
What allows brain activity to spread in one direction but not to spread out sideways?
A group of brain cells called inhibitory interneurones
They release the inhibitory neurotransmitter GABA
What percentage of neurones are interneurones?
What happens in the absence of inhibitory nternurones?
The initially localized hyperexcitability spreads into surrounding neuronal networks after involving more and more neurones, cause a clinically visible seizure
GABA is a major inhibitory neurotransmitter found in 30% of syanapses and acts on two different receptors. What are they and which one is targete dby epileptic drugs?
GABAa--> affects ligand gated chloride channel receptor
GABAb --> G protein coupled receptor
Epileptic drugs act on to GABAa to prevent the brain waves and seizures
What are the normal 5 subunits of GABAa receptor?
Pentameric: typical in vivo subunit composition is two α, two β and one γ or δ subunit
What determines the intrinisc properties of the GABAa channels? What is the implications of this?
It is effected by the GABAa subunit composition --> which effects the ability of different drugs on the receptor
What are the different types of known epilepsies causes by GABAa receptor mutation?
CAE (childhood absence epilepsy)
FS (pure febrile seizures)
GEFS+ (generalized epilepsy with febrile seizures plus)
JME (juvenile myoclonic epilepsy)
DS (Dravet syndrome – also know as SMEI (severe myoclonic epilepsy in infancy))
What is the characteristic of Dravet syndrome?
Patients experience frequent seizures, poor seizure control, and developmental delays. -
What is the action of antiepileptic drugs?
A drug which decreases the frequency and/or severity of seizures in people with epilepsy
Treats the symptom of seizures, not the underlying epileptic condition
Correct classification of seizures leads to correct Anti epileptic drug selection
What are the mode of actions of antiepileptic drugs?
1)Suppress action potential:
Sodium channel blocker or modulator
Potassium channel opener
2. Enhance GABA transmission
GABA uptake inhibitor
3. Suppression of excitatory transmission
Glutamate receptor antagonist
What are the different actions that a anticonvulsant can have?
Enhancement of GABAergic transmission
Inhibition of Na+ channels
Mixed actions--> Combination of some or all of the above and also inhibiting neurotransmitter release