Epilepsy and its Treatment Flashcards
What is epilepsy?
A group of CNS disorders in which recurrent seizures occur due to chronic underlying processes, affecting motor, sensory and autonomic outputs
What are idiopathic seizures?
cannot be ascribed to a particular cause i.e. benign neonatal convulsions
What are secondary seizures?
associated with an illness, trauma, neoplasm, infection or developmental abnormality i.e West Syndrom
How are epilepsies classified?
The locus of the epilepsy: Generalised or focal
The basis of aetiology : idiopathic or symptomatic
How is an EEG used to record brain waves?
records brain waves to detect spikes, rhythms etc can be used to view things like sleep cycles as well as epilepsy
What are the different types of partial seizure?
simple - no impaired consciousness
complex - confusion, stumbling and consciousness impaired
partial with secondary generalisation
synchronicity confined to one brain region
What are the different types of generalised seizure?
tonic-clonic - tonic rigidity followed by tremor, clonic phase results in relaxations causing jerking
absence - altered conciousness with a few mild clonic spasms, only 10-45s but can happen alot throughout day
Myoclonic - isolated clonic jerks
Atonic - sudden loss of posture leading to collapse
Infantile Spasms - bilateral myoclonic jerks, before 12months
What is status epilepticus?
term given to continuous seizures lasting more than 30mins where inadequate treatment can result in brain damage or death
What can cause status epilepticus?
non-compliance, suffering from fever, infection, hypoxia, encephalitis, subarachnoid haemorrhage, or sudden withdrawal from sedatives, or BDZs
What does the initiation of a seizure involve?
high frequency bursts of APs
hypersynchronicity
How might other neurons be recruited in a seizure?
Increase EC K+ depolarises surrounding neurons
Accumulation of Ca in presynaptic terminals enhance NT
Depolarisation induced activation of NMDA receptors resulting in Ca influx
How can we make experimental models of epilepsy?
Maximal electric shock test - partial and tonic
PT2 - pentylenetetrazol induced seizures - generalised absence seizures
Lethargic, star-gazer and tottering mutant mice - generalised
Minimal metrazol induced seizures - thought to model myoclonic seizures in humans
What are some of the channelopathies associated with Epilepsy?
nAChRa7 - juvenile myoclonic
nAChRa4b2 - autosomal dominant nocturnal FL epilepsy
GABAaRa1,y2,d - generalised epilepsy with febrile seizures
Na - Channels
K - channels
What do neurons need to produce GABA?
GAD
How is glutamine synthesised to glutamate?
glutaminase
What are treatments aimed at in treating epilepsy?
interfering with the metabolism of GABA
How are BDZs used in epilepsy and what are their features?
Used for stopping status epilepticus
Clonazepam - absence and tonic-clonic
enhance affinity for GABA
What are the possible drugs for use in treatment of epilepsy?
Phenytoin Carbamazepine Valproate Ethosuxamide Lamotrigine Topiramate Gabapentin Vigabatrin
What are the features of phenytoin?
blocks tetanic firing by increasing Na channel inactivation
reduces NT release
What are the features of carbamazepine?
acts like phenytoin and also potentiates GABA responses
is also a tricyclic antidepressant
What are the features of valproate?
acts like phenytoin and reduces Ca-T-type activity and increases GABA levels by inhibiting breakdown
used in absence seizures
What are the features of Ethosuxamide?
inhibits T-Ca-Channel activity in thalamic neurons
used in absence and myoclonic seizures
What are the features of Lamotrigine?
blocks Na channels
inhibits release of excitatory amino acids
phenytoin and carbamezapine reduce the half life
valproate prolongs half life
rashes in children
What are the features of Topiramate?
similar to phenytoin and carbamezapine also inhibits kainate receptors and enhances GABA
What are the features of Gabapentin?
elevates GABA and binds to Ca channel subunit
used for partial with or without secondary generalisation
few drug interactions - cimitedine
What are the features of vigabatrin?
inibits GABA-T
used to treat partial seizures
psychosis is a rare side-effect
