Flashcards in L16 - Epilepsy Deck (19):
Abnormal excessive electrical discharge from neurons.
An imbalance between excitation and inhibition in the brain
Loss of consciousness?
Often associated but not always produced.
0.5-1% population affected.
1 in 20 will have a seizure at some stage in their life.
Children often grow out of it.
Focal = partial, only affects part of the brain.
Manifestation will depend on the part of the brain affected.
"focal aware seizure"
"focal impaired awareness seizure"
depending on level of consciousness
Causes of focal seizure
Focal cortical dysplasia (neurons never developed)
Subependymal grey matter heterotopia (neurons failed to migrate)
Affects extensive covering of both hemispheres.
Manifestations vary greatly
Record electrical activity from scalp.
50% of patients will show a normal EEG
Only used to classify seizure type.
Following a seizure there is large EEG suppression. This can be fatal
calcium enters synaptic cleft and triggers exocytosis -- glutamate binds to AMPA and NMDA receptors
AMPA receptors open and partially depol to dislodge Mg2+ so NMDA receptors open
GABAA receptor binds 2 GABA
Opens Cl- channel = hyperpolarisation of neurons
Mutation in V-gated K+ channels:
Benign familial neonatal epilepsy
Mutation in V-gated Na+ channels:
• Severe myoclonic epilepsy of infancy (Dravet’s syndrome) – SCN1A
• Benign familial neonatal epilepsy – SCN2A
• Generalised epilepsy with febrile seizures – SCN1A, SCN1B, SCN2A
• Early onset absence seizures – SCN1B
Mutation in Ca2+ channels:
• Absence seizures due to abnormal activation of T-type Ca2+ channels in thalamus
Mutation in NAChR:
• Autosomal dominant nocturnal frontal lobe epilepsy
Mutation in GABAA receptor:
• Generalised epilepsy with febrile seizures
Drugs inducing seizures: (3)
Blockade of GABAa receptors e.g. picrotoxin
Activation of glutamate receptors (unblocks NMDA receptors by low Mg) e.g. kainite
Blockage of K channels e.g. 4-aminopyridine
Drugs to treat seizures (4)
Na+ channel blockers on presynaptic cell (prevent extended depolarisation)
Enhanced GABA neurotransmission (increased inhibition)
Ca2+ channels e.g. sodium valproate
Block glutamate transmission
Auto-antibody-induced epilepsy syndromes (3)
• Anti-voltage gated potassium channels
− E.g. focal impaired awareness seizures, limbic encephalitis, facio-brachial dystonic seizures, hyponatraemia
• Anti-NMDA receptor
− E.g. psychiatric features, dyskinesia, focal impaired awareness seizures
• Anti-GAD, anti-AMPA
Effects of seizures:
Repetitive initial exposure to brain stimulation will cause seizures, and eventually the seizures will continue even without stimulation