Epilepsy Flashcards
What is a seizure?
- Sudden, excessive, highly synchronous high frequency neuronal discharge
- May be loss of consciousness
- Behavioural changes related to site of discharge
What is the prevelance of epilepsy?
0.5 - 1% of population
Children and elderly more susceptible
2 % one seizure
30,000 new cases /year
30 % drug-refractory
25 % refractory to surgery
1000 deaths per year 50% SUDEP
What are the causes of epilepsy?
- 70% idiopathic
- genetic - rare familial disorders (LD)
- congenital/birth trauma
- neurological/neurodegenerative
- head trauma - penetrating or non-penetrating
- disease - meningitis, tumour, abcess
What are the 2 ways of recording epilepsy?
EEG
MEG
What are the 3 ways imaging is done in epilepsy?
PET – monitors local metabolism
MRI – structure and volume
fMRI – relates activity to structure
How is epilepsy diagnosed?
EEG
MRI
video telemetry
clinical description
What is a simple focal/partial seizure?
Might be…
A rising feeling in your tummy – like the sensation in your stomach when on a fairground ride
Déjà vu
Unusual smells or tastes
Tingling in limbs
An intense feeling of fear or joy
Stiffness or twitching in part of your body, such as an arm or hand
You remain awake and aware while this happens.
What is a complex partial/focal seizure?
During a complex partial seizure, you lose your sense of awareness and make random body movements, such as:
smacking your lips
rubbing your hands
making random noises
moving your arms around
picking at clothes or fiddling with objects
chewing or swallowing
You will not be able to respond to anyone else during the seizure and you will not have any memory of it.
What is a tonic-clonic seizure?
a “grand mal”
They happen in 2 stages – an initial “tonic” stage, then a second “clonic” stage:
tonic stage – you lose consciousness, your body goes stiff, and you may fall to the floor
clonic stage – your limbs jerk about, you may lose control of your bladder or bowel, you may bite your tongue or the inside of your cheek, and you might have difficulty breathing
What is an absence seizure?
An absence seizure, which used to be called a “petit mal”, is where you lose awareness of your surroundings for a short time. They mainly affect children, but can happen at any age.
During an absence seizure, a person may:
stare blankly into space
look like they’re “daydreaming”
flutter their eyes
make slight jerking movements of their body or limbs
The seizures usually only last up to 15 seconds and you will not be able to remember them. They can happen several times a day.
What are myoclonic seizures?
A myoclonic seizure is where some or all of your body suddenly twitches or jerks, like you’ve had an electric shock. They often happen soon after waking up.
Myoclonic seizures usually only last a fraction of a second, but several can sometimes occur in a short space of time. You normally remain awake during them.
What are clonic seizures?
Clonic seizures cause the body to shake and jerk like a tonic-clonic seizure, but you do not go stiff at the start.
They typically last a few minutes and you might lose consciousness.
What are tonic seizures?
Tonic seizures cause all your muscles to suddenly become stiff, like the first stage of a tonic-clonic seizure.
This might mean you lose balance and fall over.
What are atonic seizures?
Atonic seizures cause all your muscles to suddenly relax, so you may fall to the ground.
They tend to be very brief and you’ll usually be able to get up again straight away.
Where can seizures arise?
Anywhere
Mostly cortical, subcortical rare
frontal, parietal, occipital, temporal
Temporal most prevalent - 30-40%
Hippocampus, entorhinal cortex, amygdala
How do seizures arise?
Cortical activity - dynamic balance between inhibition and excitation
Two levels
Intrinsic - ion channels
Network - synaptic transmission
Disturbed balance - excessive synchrony and epilepsy
Rapid firing signals
How does Phenytoin work?
- Blocks voltage gated Na+ channels (blocking glutanate) and prolongs the refractory period
- Good for tonic-clonics
How does carbamazepine work?
- Blocks voltage gated Na+ channels (educed release of glutamate)
- Good for tonic-clonics and partials
How does lamotrigine work?
- blocks voltage gated Na+ channels and possible Ca2+ (blocking glutanate)
How do Pregab and Gabapentin work?
- Block voltage gated Ca2+ channels (blocking glutanate)
- Mimics GABA in the brain, inhibiting excessive activity
How does levetiracetam work?
- reducing vesicle fusion (blocking glutamate)
- may inhibit release of neurotransmitters
- may also block CA2+ channels
- good for tonic-clonic and partials
How do benzos work as AEDs?
- act on GABAa receptors, increasing Cl- ions
- prolong channel open time
- treats myoclonics and status epilipticus
Alternative anticonvulsants
felbamate
- blocks NMDA receptors
topiramate
- blocks AMPA/kainate receptors
retigabine
- activates K-currents
losigamone
- blocks low threshold Na-currents
How does Valproate work and what does it treat?
- Blocks voltage gated Na+ channels
- Also inhibits GABA transaminase inhibitor, blocking GABA breakdown
- Treats tonic-clonics, partials, absent seizures
What is status epilipticus?
Seizures lasting more than 5 minutes, is a medicial emergnecy
