Epilepsy Flashcards
What are the different types of epileptic seizure?
Generalised seizure (grand mal) Absence seizure (petit mal) Focal seizure (partial seizure)
What is a seizure and the pathophysiology?
Transient occurrence of signs or symptoms due to abnormal electrical activity in the brain, leading to a disturbance of consciousness, behaviour, emotion, motor function or sensation.
Abnormal and excessive excitation and synchrony of neurones within the brain, due to either a loss of inhibitory signals or too much excitatory signals.
What is the most important excitatory neurotransmitter and its receptor?
Glutamate - NMDA receptor
What is the most important inhibitory neurotransmitter and its receptor?
GABA - GABAa receptor
What might be the cause of a seizure?
Genetic differences- brain chemistry or receptors
Drugs inducing exogenous activation of receptors
Acquired brain chemistry changes- drug withdrawal, metabolism.
Damage to the networks- strokes/tumours
List some signs and symptoms of a seizure
- loss of consciousness
- change in muscle tone
- hypertonic phase
- shaking/jerking
- post-ictal period lasting minutes to hours
- aura prior to seizure
Why is epilepsy just as common in the over 60s?
Incidence increases with age, related to cerebral vasculature and strokes.
How is epilepsy defined ?
- at least 2 unprovoked (or reflex) seizures occuring >24hrs apart
- one unprovoked (or reflex) seizure and a probability of further seizures similar to the general reoccurrence risk (at least 60% over next 10 years).
- diagnosis of an epilepsy syndrome
What is a reflex seizure and suggest some triggers?
A seizure brought on by a particular stimulus.
- photogenic
- musicogenic
- eating
- hot water immersion
- reading
- orgasm
- movement
What happens in a generalised seizure?
They originate at one point and rapidly engage bilateral networks. This can include cortical and subcortical structures. Not necessarily the entire cortex.
What occurs in a focal seizure?
Originates within networks limited to one hemisphere and this may be discreetly organised or more widely distributed.
What is meant by a provoked seizure?
A seizure which is a result of another medical condition.
- drug use/withdrawal
- alcohol withdrawal
- head trauma/ intracranial bleed
- CNS infections
- metabolic disturbance - hyponatraemia or hypoglycaemia
- uncontrolled hypertension
- febrile seizure in infants
What are some differential diagnoses?
Syncope
Cardiac issues- reflex anoxic seizure, arrhythmia
Movement disorders
TIA
Migraines
Non-epileptic attack disorders (pseudo seizures)
What is the initial management of a seizure?
Airway Breathing - sats/o2 Circulation - high HR, wary of BP Disability- reduced or full consciousness E- recovery position if able
Get help and start a timer
How long should you wait before giving drugs?
5 minutes
What is status epliepticus?
A seizure lasting more than 5 minutes or multiple seizures without a complete recovery between.
It is a medical emergency and has a 30 day mortality of 20%.
What is the pharmacological treatment for status epilepticus?
Wait 5 mins Benzodiazepines Benzodiazepines Phenytoin or levetiracetam Call intensive care - thiopentone/anaesthetic
How do benzodiazepines work and what are the ADRs?
GABAa agonists, ending in the suffix -apam.
Increased Cl conductance= more negative resting potential, less likely to fire. Work best in positive membranes.
They can be addictive, cause cardiovascular collapse and airway issues.
Also used as sleep aids, alcohol withdrawal and anxiolytics.
What are the different administration routes for diazepam?
IV -lorazepam
Rectal - diazepam
Buccal or intranasal - midazolam
IM preparations available.
How is a diagnosis of epilepsy made and what are the appropriate investigations?
Should be made by a specialist - in epilepsy or first fit clinic.
Based largely on history from patients and eyewitness
Videos helpful
EEG - episode capture (more likely when sleep deprived) or abnormal pattern.
Imaging - MRI to rule out vascular or structural abnormalities
Many anti-epileptic drugs are sodium channel blockers- what is the mechanism behind this?
Block the Na channel in central neurones; slows the rate of recovery neurones from inactive to closed state. This reduces neuronal transmission.
How does carbamazepine work and what are the side effects?
Sodium channel blocker
Sometimes used for bipolar and chronic pain
Suicidal thought
Joint pain
Bone marrow failure
How does phenytoin work and its side effects?
Sodium channel blocker - mainly used in status epilepticus or adjunct in generalised seizures.
Has zero order kinetics.
Bone marrow suppression
Hypotension
Arrhythmia (IV use)
What is sodium valproate mechanism and its side effects?
Mix of GABAa effects and sodium channel blocker - 1st line for generalised epilepsy. Aka epilim,depakote.
- liver failure
- pancreatitis
- lethargy
