Epilepsy Flashcards
is epilepsy acute or chronic
it can be both
note epilepsy was known as the sacred disease by the ancient greeks
the most common ages affected in epilepsy
note it can affect all ages
under 20 and over 65
possible causes of epilepsy
cause mostly unknown in most cases
Brain infection, e.g. meningitis
* Birth complications leading to lack of oxygen
* Stroke
* Brain tumour
* Head injury
* Drug/alcohol abuse
* Genetic element
Meningitis is a serious infection of the membranes that surround the brain and spinal cord
the main characteristic of epilepsy
Abnormal and excessive discharge of a set of neurons in the brain, resulting to seizures.
note that the seizures in epilepsy are unprovoked and recurrent, so 2 or more
discharge= depolarization basically
what is resting membrane potential
-70mv
where in a neuron is an action potential generated
the axon hilock
difference between seizures and convulsions
A broader term encompassing any abnormal brain electrical activity, which can cause various symptoms including convulsions, altered consciousness, or even subtle changes in behavior
while
convulsions refer to the physical manifestation of rapid, uncontrolled muscle contractions and jerking movements that can happen during some types of seizures.
not all seizures are charatcerised by convulsions
some symptoms of seizures
note that there are differnt types of seizures, and symptoms are dependent on the type
Convulsions
Abnormal sensory experience
Effects on mood and behaviour
Loss of consciousness
Increased salivation
Stereotyped movements (e.g. rubbing
the types of seizures and their descriptions
simple: no loss of consciousness
complex : there is impaired consciousness
partial: does not involve the entire brain
generalised: affects the whole brain, or a larger portion of it
status epilepticus: Uninterrupted seizure activity (life threatening condition)
Status epilepticus (SE) is a medical emergency that occurs when a seizure lasts longer than five minutes or when a person has multiple seizures without regaining consciousness
types of partial seizures
simple
complex
secondary generalised(eventually develops into generalised)
types of generalised seizures
tonic-clonic(Period of increased muscle tone and jerking)
absence(Loss of motor activity)
myoclonic
atonic(drop attacks)
clonic (repetitive jerks )
tonic(Immediate increase of muscle tone)
A drop attack is a sudden fall to the ground without losing consciousness.
how can we diagnose epilepsy
The description of symptoms(patient history)
Blood tests
EEG (Electroencephalogram)
MRI (Magnetic Resonance Imaging)
An electroencephalogram (EEG) is a painless test that measures the electrical activity of your brain. It’s also known as a brain wave test.
epileptogenesis
Epileptogenesis is the process of developing epilepsy
the main mechanisms of action of antiepileptic drugs
Enhancement of GABA action( GABA selectivity)
Inhibition of sodium channels
Inhibition of calcium channels
these are all aimed at producing an inhibitory effect, to prevent excitation of the neurons
glutamate and calcium channel inhibition can also help in epilepsy
how can the action of GABA be enhanced for the treatment of epilepsy
GABA is a neurotransmitter btw
Activation of GABA receptors by allosteric modulation
Inhibition of GABA transaminase
Inhibition of GABA reuptake( preventing the reabsorption of GABA from the synapse)
Allosteric modulation of GABA receptors is a process that involves binding of a compound to a receptor at a different site than the neurotransmitter GABA. This changes the receptor’s conformation, which in turn affects the receptor’s affinity for GABA
GABA transaminase function
An enzyme that helps break down a brain chemical (neurotransmitter) called GABA when it is not needed
inactivated sodium channels description and their functions
After a sodium channel opens and allows sodium ions to flow into the neuron, the channel quickly enters the inactivated state. In this state, the channel cannot reopen immediately, even though it is still technically “open” in the sense that it’s not in its resting state.
Essential for the refractory periods after depolarisation
prevents repetitive firing..etc
the inactivated channels are also referred to as the second gates, and while one sodium channel opens to allow influx, these close to prevent further sodium influx, preventing repetitive firing.
what does it mean when we say sodium channel inhibitors in epilepsy are use-dependent
Use-dependence means that the more often the sodium channels are activated (i.e., the more frequently a neuron fires), the more the sodium channel inhibitor binds to the channels and prevents further activation. In essence, the drug is more effective when the neuron is firing more rapidly.
the primary target for calcium channel blockers/inhibitors in epilepsy
t-type calcium channels
T-type calcium channels are important for
the discharge associated with absence
seizures
antiepileptic drugs can be known as anticonvulsant drugs, true or false
true
some common examples of use-dependent sodium channel blockers
phenytoin
carbamazepine
lidocaine
mexiletine
flecainide
phenytoin MoA
acts on the sodium channels in both neuronal and cardiac tissue. Blocks the channels
note , it is effective for most forms of seizures apart from absent seizures
plasma half life of phenytoin
20 hours
what are some of the side effects of phenytoin(usually at concentrations over 100micromole/L)
Ataxia
Gum hyperplasia
- Confusion
- Headache
- Skin rashes
- Teratogenesis risk
- Anaemia (can be corrected with folic acid)
