CPT: Epilepsy Flashcards
What is epilepsy?
A neurological disease that has a range of symptoms that are associated with a moment of scncronized abnormal electrical activity in the brain
Who is effected by the disease?
- Over 65s
- Young children
What causes it?
- 70% - unknown
30%:
- head trauma
- posioning
- infection
- maternal injury
- cardiovascular
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How is Epilepsy diagnosed?
- Detailed history taken - eye witness may be needed as when seizure their mind will be blank
- Physical exam
- Blood tests
- ECG
- EEG
- imaging: CT scan, MRI
- NEuropsychological assessment
Seizures are broken up into different classes depending on what?
- Where they start in the brain (onset)
- Whether or not the persons awareness is affected
- whether or not seizures involve other symptoms such as movements
Why would an MRI be used?
To see potential area in the brain that have been damaged or a brain tumour
What is EEG?
Electroencephalography
What classifications of seizures are there?
- Focual (awarenes/ impaired): when affects only a part of the brain
- Generalised: Affects both hemispheres
Describe focal awareness seizures
- Affects only a small part of the brain
- Person is conscious
- Range of symptoms depending on the affected area: Tingling (sensory), twitching (motor), flashing lights (visual)
Describe focal impaired awareness seizures
- Affects a larger part of one hemisphere
- Person may be confused
What is automatism?
Strange repetitive movements
Describe generalised seizures
Affects both hemispheres
- Abscene
- Tonic clonic
- Atonic
- Myoclonic
- stratus epilepticus
What is absence?
Blank, unresponsive, breifly unconscious
What is tonic clonic
Unconscious, muscle become stiff (tonic) and then shake and jerk (clonic). After wards patient feels tired and has a headache
What is Atonic?
Muscles relax
What is myoclonic?
Conscious muscle jerk
What is stratus epilepticus?
Seizures lasting more than 5 minutes
What is the pathophysiological cause of seizures?
- Membrane depolarisation
Alterations in NA (reduce threshold/ increase AP rate) or K channel function and/or extracellular potassium pump
- Increased Excitation
Release of excitatory AA - Glutamate
- Decreased inhibition
Reduced inhibitory transmission - GABA mainly
What are the sequence of events that occur during a seizure?
- Intitation- High frequency burts of APs
- Syncronisation- hyper-syncronisation of the neuronal population. Leads to hyper excitability
- Propagation- Loss of surrounding inhibition and recruitment via antatomical connections. Propagates across both hemispheres
What are the aims for antiepileptic drugs? (AEDs)
- stabilize membrane potential and prevent depolarisation by action of on ion channels (K, Na, Ca)
- Increase inhibitory (GABA) transmission
- Decrease excitatiry transmission (Glutamate)
What are targets for where AEDs will act?
- Inhibit Ca/ Na channels
- Activate K channels
- Increase GABA transmission
- Decrease glutamate transmission
What is the mechanism of action of phenytoin?
Phenytoin binds to the inactive state of the Na channel and temporaly blocks and delays its activation
What are sites of action for AEDs - excitatory synapes?
- Na channels in nerve terminals - phenytoin
- Ca channels - reduces NT release - Gabapentin
- Acts on glutamate receptors (NMDA, AMPA) - less likely to work
- Activate K channels
What are sites of action of AED - inhibitory synapes?
- Release Gaba - benzodiaepens, barbituates
- Block reuptake of GABA - round for longer
- MOdify degradation of GABA
What are examples of AEDs and where they act
- Na channels - phenytoin, lamotrigine
- Ca - Gabapentin, sodium valporate
- K - Retigabine
- Enhance GABA transmission - Benzos, barbituates
- Inhibit EAA transmission - valporate
