Epilepsy Flashcards
What is epilepsy
Disorder of the CNS characterised by recurrent, sudden large increases in electrical activity (electrical seizures) that may be localised or generalised. Electroencephalogram diagnoses epilepsy.
What do symptoms depend on
The CNS region, e.g. if motor cortex is included area of seizure then uncontrolled movements would be expected
Whether the seizure is localised in one hemisphere or a particular part of the brain or is generalised throughout the brain
If localised initially, whether the seizure then becomes generalised by spreading to other regions of the CNS
What is a partial seizure
if the seizure is restricted to a limited region. Simple if the subject remains conscious and aware or complex is consciousness is impaired.
What is a primarily generalised seizure
most of the CNS is involved but no focus can be distinguished
What is a secondarily generalised seizure
most of the CNS is involved but the excitation has spread from an initial focus
How many children have seizures and how many go on to develop epilepsy
2-5% of children experience one or more seizures. 10% go on to develop some form of epilepsy in adulthood.
What is tonic clonic seizure
a motor seizure, impaired awareness, generalised onset, 2-5 minutes. Sudden stiffening of muscles, followed by a fall and jerking movements
What is a temporal lobe seizure
focal onset seizure of temporal lobe, characterised by emotional, sensory or memory related phenomena. No loss of awareness. Developing as the seizure spreads throughout the temporal lobe impairing consciousness to become a focal or bilateral generalised tonic clonic seizure
What is an absence seizure
non-motor seizure with impaired awareness. Generalised onset, common in children. Repeated periods of sudden loss of awareness.
What is status epilepticus
seizure does not spontaneously stop. Lasts > 30 minutes
What are epilepsy syndromes in children
Generalised epilepsy with febrile seizure plus Lennox-Gastaut syndrome (multiple seizures and intellectual disability) Dravet syndrome (epilepsy caused by hot temperature)
What is benign febrile epilepsy linked to
mutation in KCNQ2 and KCNQ3 , which encodes voltage gated potassium channels.
What is GEFS+ linked to
SCN1B, a gene that encodes an accessory subunit of the voltage gated sodium channel
What does paroxysmal depolarising shift do
Initiates seizures. Epilepsy is often described as being due to an imbalance between glutamate-mediated excitation and GABA-mediated inhibition.
What happens with surround inhibition
mediated by interneurons through feedback pathways has the effect of limiting spread of the input signalling. Increase GABA to improve inhibition.
What happens with no surround inhibition
No surround inhibition - diverging synaptic connections of neurones in a relay nucleus can lead to spreading as well as blending of information flowing out of the nucleus
What do sodium channel blockers do
Tonic clonic, partial and temporal lobe seizures
Carbamazepine, phenytoin, lacosamide
What are the side effects of carbamazepine and phentonin
increase the frequency of absence seizures
How do voltage gated sodium channels work
Drugs will reduce the likelihood of action potentials firing at high frequencies but have relatively little effect at low frequencies. Drug binds at inactivated state and stabilise it. Increases the refractoriness of the cell and limits the maximum frequency at which the cell can fire.
What treats tonic clonic and absence seizures
Sodium valproate: mechanism uncertain. Combines a weak blocking action on voltage gated sodium channels with a weak inhibition of GABA transaminase.
Lamotrigine: Use dependent sodium channel blocker
What does enhancing the activity of GABAergic system treat
Tonic clonic, partial, temporal
What drugs treat GABergic systems
Benzos Barbiturates Vigabartin Tiagabin Gabapentin, pregablin Retigabine Perampanel Leveiracetam
What do benzodiazepiens do
enhance GABA activity. Bind to regulatory site on the GABAa receptor and increase the affinity of the receptor for GABA.
What do barbiturates do
Prolongs GABA-activated Cl- channels opening when GABAa receptor is occupied
What does vigabatrin do
contraindicated for absences): inhibits GABA transaminase
What does tiagabin do
(contraindicated for absences): inhibits GABA uptake an therefore increases the concentration of GABA in extracellular space
What do gabapentin and pregablin do
molecular target voltage-gated Ca2= channels, compromise NT release
What does retigabine do
provoking the opening of k+ channels of the KCNQ type so the anticonvulsant effect is probably due to stabilisation of the resting membrane potential of neurones
What perampanel do
Antagonist of AMPA
What does vagal stimualtion do
electrical stimuli to affect vagus nerve. Activated by a magnet to deliver a predefined program of stimuli to abort an ongoing or impending attack.
What is a ketogenic diet
high fat, low carb. Used in children
