Session 13 Flashcards
Define seizure
“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”
Pathology of seizures
■ The brain is a complicated network of neurones ■ These are either excitatory, inhibitory or interneurons ■ The most important excitatory neurotransmitter is glutamate via the NMDA receptor ■ The most important inhibitory neurotransmitter is GABA, via the GABAa receptor
Glutamate + NMDA Receptor
■ Cation channel- lets in Na and Ca
and lets K out ■ Depolarises membrane ■ More likely to fire action potential • In the normal brain the inhibitory and excitatory sides are
in balance
GABA and GABAa Receptor
■ Cl- channel ■ Hyperpolarise membrane ■ Less likely to fire action potential
■ A seizure is the clinical manifestation of abnormal and excessive excitation and synchronisation of a group of neurones
within the brain ■ Therefore a loss of inhibitory (GABA mediated) signals ■ Or too strong an excitatory (NMDA/Glutamate) one ■ This imbalance can happen in any point in the brain, and local changes can lead to generalised effects
■ This can be caused by genetic differences in brain chemistry/receptor structure – genetic epilepsy syndromes ■ By exogenous activation of receptors- drugs ■ Acquired changes in brain chemistry- drug withdrawal, metabolic changes ■ Damage to any of these networks- strokes, tumours
Time for some ICPP
Image and panopticon
What are the signs and symptoms of a seizure
Not just shaking
For generalised seizures a loss of consciousness often (but not always) with changes in muscle tone, tongue biting
For tonic-clonic seizures initial hypertonic phase, followed by rapid clonus (shaking/jerking)
Post-ictal period present- can last minutes up to hours
Often an aura prior to seizure
May be more varied or subtle depending on type of seizure
How to define epilepsy?
■ Not everyone who has a seizure has epilepsy ■ An epilepsy diagnosis is life changing, and therefore should only be made by a
specialist, in an epilepsy or first fit clinic
■ Note not just a disease of the young, over 60s almost as common and incidence
increases with age
■ Epilepsy is a tendency toward recurrent seizures unprovoked by a systemic or
neurological insult
■ At least two unprovoked (or reflex) seizures occurring more than 24 hours apart ■ One unprovoked (or reflex) seizure and a probability of further seizures similar to the
general recurrence risk after two unprovoked seizures (at least 60% over the next 10
years) ■ Diagnosis of an epilepsy syndrome
Types of Reflex Seizure
■ Seizure brought on by a particular stimulus
■ Photogenic ■ Musicogenic ■ Thinking ■ Eating ■ Hot water immersion ■ Reading ■ Orgasm ■ Movement
What are the classifications of seizure
Images and panopto
Generalized seizures
• Originate at some point within and rapidly engage bilaterally distributed networks • Can include cortical and subcortical structures but not necessarily the entire cortex
Focal seizures
• Originate within networks limited to one hemisphere • May be discretely localized or more widely distributed.…
Older terminology
■ Grand mal= Generalised seizure ■ Petit mal= absence seizure ■ Partial seizure= focal seizure
Provoked Seizures
■ Seizure as a result of another medical condition ■ Examples include: ■ Drug use or withdrawal ■ Alcohol withdrawal ■ Head trauma and intracranial bleeding ■ Metabolic disturbances e.g hyponatraemia, hypoglycaemia ■ CNS Infections: meningitis and encephalitis ■ Febrile seizures in infants ■ Uncontrolled hypertension
■ Key is to treat both the seizure and the underlying condition. Unlikely to need ongoing AED treatment if cause treated
Differential diagnosis of seizures
■ Syncopal episodes e.g vasovagal syncope ■ Cardiac issues including reflex anoxic seizures, arrythmias ■ Movement disorders e.g Parkinsons, Huntingtons ■ TIAs ■ Migraines ■ Non-epileptic attack disorders (formerly pseudo-seizures)
Initial Management of a Seizure
■ Primary Survey/A to E assessment ■ Airway- Is it patent? Can you do anything about it it?/Adjuncts ■ Breathing- Sats reading +/- Oxygen ■ Circulation- Expect a high HR, wary of BP ■ Disability- Will have reduced consciousness in generalised seizures, may be awake in
partial ■ E- May want to get them into recovery position if able ■ Do something for the ABC problems if you can ■ Look at a clock/start a timer ■ Get some help
When to use drugs to treat seizures?
■ The majority of seizures will self terminate without the use of drugs ■ Wait for 5 minutes and if still going then give seizure terminating drugs
Status Epilepticus
A seizure (of any variety) lasting more than 5 minutes or more, or multiple seizures without a complete recovery between them
Status is a medical emergency
It occurs in around 40 out of 100,000 people per year and has a 30 day mortality of around 20%
Pharmacological Treatment for Status
■ Wait 5 minutes ■ Benzodiazepine ■ Benzodiazepines again ■ Phenytoin (or maybe Levetiracetam?) ■ Thiopentone/Anaesthesia (Call intensive care/anaesthetics)
Benzodiazepines
■ Class of drug- GABAa agonists ■ End in –apam, come in various flavours
■ Increased Cl- conductance, = more negative resting
potential, less likely to fire. ■ Work best when membrane positive i.e in seizures ■ No firing neurones=no more seizure
■ Be wary of addiction, cardiovascular collapse, airway
issues ■ Also used as anxiolytics, sleep aids, alcohol
withdrawal
Benzodiazepine Options for Status Epilepticus
■ Intravenous Lorazepam ■ Diazepam rectally- difficult to do ■ Buccal or intranasal Midazolam – Don’t lose a finger
■ IM can also work, and various IM preparations are on different local guidelines
■ The non-guideline answer, get some fast acting benzos into the patient one way or
another. ■ Remember you can always put more in but you can’t take it out so go slowly
How to make a diagnosis of epilepsy?
■ Epilepsy diagnosis should be made by a specialist, in a dedicated first fit or epilepsy
clinic ■ Largely based on history from patient and eyewitnesses to attacks ■ Video can be very helpful in determining this
What investigations should be done for someone who may have epilepsy
■ Electroencephalography:
■ Record of electrical pattern of activity in the brain ■ Can be very useful, especially if an attack is caught while being
recorded- Can make this more likely with sleep deprived EEG ■ But relies on either capturing an episode or an abnormal pattern ■ Many people without epilepsy have an abnormal EEG ■ A single EEG may show abnormalities in as few as 30% of adults
with epilepsy
What imaging can be done for someone with epilepsy
■ MRI is the imaging of choice ■ May detect vascular or structural abnormalities that
can account for epilepsy ■ Generally not required when there is a degree of
confidence that there is a generalised epilepsy
syndrome e.g generalised seizures in a young
person, associated with sleep deprivation
Anti-Epileptic Drugs (AEDs) and why do we use them?
■ There are numerous AEDs, with varying mechanisms of action ■ We will concentrate on 6: ■ Carbamazepine ■ Phenytoin ■ Valproate ■ Lamotrigine ■ Levetiracetam ■ Benzodiazepines for seizure termination (already done)
■ Sudden Unexplained Death in Epilepsy (SUDEP) ■ Occurs in 0.1% adults with epilepsy per year ■ More frequent in people with poor seizure control
■ Massive burden- can impact ability to drive, swim, have a bath, time out of school or
university
How Anti-Epileptic Drugs Work
Panopto
■ Lots of potential mechanisms ■ Many drugs act in several ways
Sodium Channel Blockade
■ Blocking of Na channels in central neurones ■ This slows recovery of neurones from inactive
to closed state ■ Reduces neuronal transmission
How does Carbamazepine (Tegretol) work and what are it’s side effects?
■ Sodium channel blocker ■ Also used as a medication for bipolar and sometimes chronic pain
■ Side effects: ■ Suicidal thoughts ■ Joint pain ■ Bone marrow failure
How does Phenytoin work and what are it’s side effects?
■ Sodium channel blocker ■ Use mainly in status epilepticus or as an adjunct in generalised seizures ■ Exhibits zero order kinetics- care when adjusting doses
■ Specific side effects: ■ Bone marrow suppression ■ Hypotension ■ Arrythmias (IV use)
How does Sodium Valproate (Epilim, Depakote)
work and what are it’s side effects?
■ Probably a mix of GABAa effects and sodium channel blockade ■ As per guidelines 1st line for generalised epilepsies
■ Specific side effects: ■ Liver failure ■ Pancreatitis ■ Lethargy
Lamotrigine
■ Primarily a sodium channel blocker, may also affect calcium channels ■ Good for focal epilepsy ■ Used often where valproate contraindicated in generalised epilepsy
