Epilepsy (15) Flashcards Preview

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Flashcards in Epilepsy (15) Deck (66)
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1

Seizures

Abnormally excessive and hyper synchronous activity of neurones located predominantly in cerebral cortex

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Twitches/convulsions

Cortical discharges transmitted to muscles

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Classification of seizures

1. Generalised
2. Partial
3. Secondary generalised

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Generalised

Initial activation of neurones throughout both hemispheres (tonic clonic/clonic/atonic)

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Partial

Initial activation of a limited number of neurones in a part of 1 hemisphere (absence/myoclonic/simple/complex)

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Secondary generalised

Partial seizure that later spread to involve majority of 2 cerebral hemispheres

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Manifestation of partial seizure in parietal lobe

Tingling/jerking in leg, arm, face

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Manifestation of partial seizure in occipital lobe

Flashing lights/spots, vomiting

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Manifestation of partial seizure in temporal lobe

Strange smell or taste, altered behaviour, deja vu, lip smacking/chewing movements

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Manifestation of partial seizure in frontal lobe

- Adversive seizures (Eyes/head both turn to one side)
- Jacksonian seizure (tingling feeling in hand/arm)

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EEG

Electroencephalogram

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EEG uses

Scalp electrodes to record electrical activity along scalp - firing of neurones within brain, series of electrical impulses originating in brain are amplified and summed into waves (Spike-wave discharges)

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Status epliepticus

State of persistent seizure, more than 30 mins/2+ without full recovery

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Why is SE a medical emergency?

The longer a seizure lasts, less likely it will stop on its own and more likely to reoccur in future

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Treatment for SE

GABAa receptor agonist e.g. diazepam

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Epilepsy

2 or more unprovoked seizures

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Mechanisms underlying seziures

Excitation or inhibition > too much neuronal activity > seizure

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Excitation (too much)

Ionic - Na+, Ca2+ influx, neurotransmitter - glutamate, aspartate release

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Inhibition (too little)

Ionic - Cl-influx, K+ efflux
neurotransmitter GABA release

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Inhibitory interneurones

Allow activity to spread in one direction but not sideways, release inhibitor neurotransmitter GABA

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GABA

Major inhibitory neurotransmitter, found at 30% of synapses, acts via GABAa or GABAb

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GABAa

Ligand-gated chloride channel receptor

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GABAb

G protein-coupled receptor

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What determines intrinsic properties of each channel

GABAR subunit

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Types of epilepsies caused by mutation in GABAa receptor subunits

- Childhood absence epilepsy (CAE)
- FS (pure febrile seizures)
- GEFS+ (generalised epilepsy with febrile seizures plus)
- JME (juvenile myoclonic epilepsy)
- DS (Dravet syndrome - SMEI severe myoclonic epilepsy in infancy)

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Dravet syndrome associated with which mutation

GABRG2(Q390X) > loss of 78 C-terminal aa (changes it from transmembrane protein to a globular cytosolic protein)

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Febrile seizures

Associated with fever

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Tonic-clonic/grand mal

Generalised

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Myoclonic seizure

Involuntary twitching of a muscle/group of muscles

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Absence seizure

Lapses of awareness, staring, last only a few seconds, common in children