L21 Antiepileptics Flashcards
Seizure
Transient disturbance of consciousness, behaviour, emotion, motor function or sensation due to abnormal and excessive electrical activity in the brain
Pathology of seizures at glutamate receptors
NMDA receptors: Cation channels let Na+ and Ca2+ in and K+ out Depolarises membrane More likely to fire action potentials NMDA too strong
GABA receptors: Allows Cl- influx Hyperpolarisation Less likely to fire an action potential Loss of GABA signals
Imbalance between receptors
Causes of seizures (4)
Genetic difference - genetic epilepsy syndrome
Drugs or alcohol
Drug withdrawal or metabolic changes
Damage to neuronal networks - stokes or tumours
Symptoms and signs of a general seizure
Shaking Loss of consciousness Hyper or hypotonic Tongue biting Loss of bladder or bowel control Post-ictal period present (after seizure there is reduced consciousness for mins to hours) Aura before seizure
Signs and symptoms of tonic clinic seizures
Shaking Initial hypertonic phase Followed by rapid clonus (shaking or jerking) Post ictal period present Aura before seizure
Epilepsy
Tendency toward recurrent seizures unprovoked by a systemic or neurological insult
- diagnosed by expert largely based on history
- seen in young and over 60s
Epilepsy criteria
At least 2 unprovoked (reflex) seizures occurring more than 24 hours apart
Or
One unprovoked (reflex) seizure and a probability of further seizures similar to the general recurrence risk after 2 unprovoked (reflex) seizures
Types of reflex seizure (8)
Photogenic - flashing lights Musicogenic Thinking Eating Hot water emmersion Reading Orgasm Movement
Classification of seizures
Focal onset (partial seizure) Generalised onset (grand mal) Unknown onset Absence seizure (petit mal)
Focal onset seizure presentation
1 side of the brain
Doesn’t spread rapidly
- aware or impaired awareness
- motor onset or non motor onset
- focal to bilateral tonic - clonic
Motor focal onset signs
Automatism Atonic Clonic Spasms Hyperkinetic Myoclonic Tonic
Non motor onset focal
Autonomic Cognitive impairment Sensory impairment Emotional impairment Behaviour arrest
Generalised onset symptoms
Bilateral
Rapid spread
Loss of consciousness
Motor:
- clonic
- tonic - clonic
- myoclonic
- atonic
Non motor
Provoked seizure
As a result of medical conditions
Treat the seizure and underlying condition
Unlikely to need ongoing anti epileptic drugs
Differential diagnosis of seizures (6)
Syncopal episodes Cardiac issues - reflex anoxic seizures Movement disorders - Parkinson’s or Huntington’s TIAs Migraines Non epileptic attack disorders
Initial management of seizure
A/E assessment
Recovery position
Start a timer or look at clock
Majority of seizures self terminate without the use of drugs in 5 minutes
Status epilepticus
- A seizure of any type lasting more than 5 minutes or multiple seizures without a complete recovery between them
- medical emergency
Pharmacological treatment of status epilepticus
Wait 5 minutes
- benzodiazepines
- benzodiazepines again
- phenytoin
- thiopentone or anaesthesia
Benzodiazepines mechanism
GABAa agonists - increased Cl- influx
End in - apam e.g. lorazepam or diazepam
Increases inhibition
Benzodiazepine side effects
Addiction
Cardiovascular collapse
Airways issues
Other benzodiazepine uses
Anxiolytics
Sleep disturbance
Alcohol withdrawal
Delivery of benzodiazepines
Intravenous lorazepam Rectal diazepam (difficult) Buccal or intranasal midazolam
Investigations and imaging of seizures
Electroencephalograph during episode
Imaging - MRI (generally not required)
Anti epileptic drugs
Sodium channel blocker:
- Carbamazepine
- Phenytoin
- Valproate
Calcium channel blocker:
Lamotrigine (focal onset)
SV2a - synaptic vesicle glycoprotein binder inhibition:
Levetiracetam
GABA agonist:
Benzodiazepines
