12.1 Epilepsy Flashcards
What is a seizure?
Abnormal electrical activity in the brain leading to transient occurrence of signs of symptoms such as disturbance of consciousness, behaviour, emotion, motor function or sensation
What are the three different types of neurones in the brain?
Excitatory
Inhibitory
Interneurones
What is the most important excitatory neurotransmitter and how does it work?
Glutamate via the NMDA receptor
What is the most important inhibitory neurotransmitter and how does it act?
GABA via the GABAa receptor
Briefly describe the excitatory action of glutamate on neurones?
Glutamate binds to the NMDA receptor. The NMDA receptor is a cation channel, letting in Na and Ca and letting K+out. This increases the membrane potential, depolarising the neurone. This makes it more likely to fire an AP with less stimulation as closer to threshold
Describe the inhibitory action of GABA on neurones?
GABA binds to a GABAa receptor. The GABAa receptor is an allosteric modulator that results in the opening of a chloride channel. Chloride ions can then move into the neurone, resulting in it hyperpolarising. This moves the resting potential away from the threshold and makes it harder to fire an action potential
What is the pathology of a seizure?
A seizure is the clinical manifestation of abnormal and excessive excitation and synchronisation of a group of neurones within the brain
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
What causes the imbalance of excitatory and inhibitory signals in the brain?
- 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
What are the common signs and symptoms of a seizure?
Shaking / rapid clonus Loss of consciousness Changes in muscle tone Tongue biting Post-octal period Aura prior to having a seizure
What is the post-ictal period?
The period of time immediately following a seizure. Can last minutes to hours. Confusion and vacancy during this time
What age group is most likely to experience epilepsy?
disease affects children and teenagers as well as
over 60s almost as common and incidence increases with age
What is epilepsy?
Epilepsy is a tendency toward recurrent seizures unprovoked by a systemic or neurological insult
What is the diagnostic criteria of epilepsy?
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)
Or diagnosed with an epilepsy syndrome
What is a reflex seizure?
A seizure brought on by a particular stimulus
What are the different types of reflex seizures?
Photogenic Musicogenic Thinking Eating Hot water immersion Reading Orgasm Movement
What are the three main categories of basic seizures?
Focal onset - only occurs in one particular small part of the brain
Generalised onset - occurs on both sides of the hemispheres
Unknown onset - unknown as to where the seizures occurring.
What are the different types of focal onset seizures that can occur?
Aware - maintain consciousness (e.g. only in hand)
Impaired awareness - reduced cognition
Motor onset
Non motor onset
Focal to bilateral tonic-clonic (Development of the seizure)
What are some of the presentations of a generalised onset seizure?
Always lose consciousness Tonic-cloning = period of hypertonicity followed by rapid jerking movements Myoclonus = jerking Atonic = complete loss of muscle tone (sudden drop to the floor) Non motor (absence) = vacant episodes for minutes to hours
What is the development of a generalised seizure?
Originate at some point
within and rapidly engage both hemispeheres
Describe the distribution of the brain affected in a focal seizure
• Originate within networks limited to one hemisphere
• May be discretely localized
or more widely distributed.…
What is a Grand mal seizure?
Generalised seizure
What is a petit mal seizure?
Absence seizure
What is a partial seizure?
A focal seizure
What is a provoked seizure?
A seizure as a result of another medical condition
Give examples of what can cause a provoked seizure?
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 (any illness that causes fever)
Uncontrolled hypertension
What are differential diagnosis of seizures?
Syncopal episodes e.g vasovagal syncope
Cardiac issues including reflex anoxic seizures, arrythmias (hypoxic brain can cause jerking)
Movement disorders e.g Parkinsons, Huntingtons
TIAs
Migraines
Non-epileptic attack disorders (formerly pseudo-seizures)
What is the initial management of a seizure?
- primary survey (Airway, Breathing, Circulation, Disability,exposure/everything else)
- apply oxygen as in high metabolic state
- lock at clock/start a timer
- get some help
What is status epilepticus?
A seizure of any variety lasting more than 5 minutes or more, or multiple seizures without a complete recovery between them. Medical emergency
When are drugs used to treat seizures?
In status epilepticus - if the seizure/ episode lasts longer than 5 minutes
What is the pharmalogical treatment for status epilepticus?
- full does of benzodiazepines
- if no improvement in 5 minutes give another 2nd full dose of benzodiazapine
- if after 15 minutes no improvement give 2nd line anti-epileptic drugs (phenytoin, levetiracetam). Need to monitoring patient
- consider IV thiamine if alcohol use
- if still no improvement get anaesthetist and consider general anaesthesia (thiopentone) with support
What are benzodiazepines mechanism of action?
GABAa agonists
Increased Cl- conductance, = more negative resting potential, less likely to fire.
Why are benzodiazapines not used as a preventative drug for having seizures?
As Work best when membrane positive i.e in seizures. Also have significant side effects. Be wary of addiction, cardiovascular collapse, airway issues.
What are benzodiazepines used for?
Stopping seizures (status epilepticus )
Anxiolytics
Sleep aids
Alcohol withdrawal
What are the different benzodiazepine options for treating status epilepticus?
Intravenous Lorazepam (need IV access- can be hard) Diazepam rectally Buccal or intranasal Midazolam – Don’t lose a finger IO/IM can also work, and various IM preparations are on different local guidelines
How is epilepsy diagnosed?
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 are done to diagnose epilepsy?
Electroencephalography
MRI
What is 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
Why are MRIs used in epilepsy diagnosis?
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
What are the 6 different anti-epileptic drugs?
Carbamazepine Phenytoin Valproate Lamotrigine Levetiracetam Benzodiazepines
Why do patients generally stay on the same type of anti-epileptic?
Different brands will have slightly different pharmacodynamics and pharmacokinetics
Should stay on same formulation so in a steady state
Why is it vital to have good seizure control?
As sudden unexplained death in epilepsy (SUDEP) is more frequent in patients with poorer seizure control
Massive burden- can impact ability to drive, swim, have a bath, time out of school or university
Why are sodium channel blockers useful for treatment of epilepsy?
Blocking of Na channels in central neurones slows recovery of neurones from inactive to closed state. Reduces neuronal transmission
What is the mechanism of action of carbamazepines?
Sodium channel blocker. Slows recovery of recently fired neurones, reducing the neuronal transmission.
What are carbamazepines used for?
Epilepsy
Bipolar disorder
Chronic pain / neuropathic pain (trigeminal neuralgia)
What are the ADRs of carbamazepines?
Suicidal thoughts
Joint pain
Bone marrow failure
Give an example of a carbamazepine
Tegretol
What is the mechanism of action of phenytoin?
Sodium channel blocker.
What is the common indications for phenytoin?
Status epilepticus
Adjunct in generalised seizures
Why must physicians take care when adjusting doses of phenytoin?
Exhibits zero order kinetics
What are the ADRs of phenytoin?
Bone marrow suppression
Hypotension
Arrhythmia (IV use)
What is the mechanism of action of sodium valproate?
Probably a mix of GABAa effects and sodium channel blockade
What is the 1st line treatment of generalised epilepsies in adults?
Sodium valproate
Give examples of sodium valproate drugs
Epilim
Depakote
What are the ADRs of sodium valproate?
Liver failure
Pancreatitis
Lethargy
What is lamotrigine?
Primarily a sodium channel blocker, may also affect calcium channels (stopping in flux of +ve ions, hyperpolarising membrane, further away from seizure threshold)
What is lamotrigine used for?
Good for focal epilepsy
Used often where valproate contraindicated in generalised epilepsy
What is the mechanism of action of levetiracetam?
Synaptic vesicle glycoprotein binder. Stops the release of neurotransmitters into
synapse and reduces neuronal activity
What are levetiracetam used for?
Focal seizures
Generalised seizures
May start being used for status epilepticus
Safe in pregnancy
Why is levetiracetam a preferential treatment option for epilepsy?
Well tolerated
Easy dosing
Safe in pregnancy
What are the common side effects of AEDs?
Largely common across all drugs:
Tiredness/drowsiness
Nausea and vomiting
Mood changes and suicidal ideation
Cause or increase risk of Osteoporosis
Rashes, including Steven Johnson syndrome can be caused by all. Most likely in carbamazepine or phenytoin (1 in 1000)
Many can cause anaemia, thrombocytopenia or bone marrow failure
What are the key drug drug interactions of anti epileptics?
Patients on anti-epileptics and warfarin will need close monitoring
Ideally patients on AEDs should not consume alcohol Carbamazepine and phenytoin may decrease the effectiveness of oral contraceptive pills
Carbamazepine and phenytoin may decrease the effectiveness of some antibiotics
Valproate can increase the plasma concentration of other AEDs
Why is Levetiracetam preferred over other older anti epileptic drugs?
Newer AEDs have less side effects, or are metabolised in other ways, not including the CYP450 enzymes (levetiracetam)
What commonly prescribed drugs are CYP450 inducers?
Phenytoin Carbamazepine Barbituates Rifampicin Alcohol (chronic) Sulphonylureas
What drugs are CYP450 inhibitors?
Omeprazole Disulfiram Erythromycin Valproate Isoniazid Ciprofloxacin Ethanol Sulphonamides
How do you start someone on anti epileptic drugs?
- Based on guidelines, pick a drug
- Start on a low dose and build up
- Trial drug - ADR and efficacy
- Aim is seizure free with minimal or acceptable side effects
- Plasma levels can be monitored e.g. pregnant,loses seizure control, issues with adherence
- transition to new drug carefully
- Should be overseen by a specialist
Why should valproate not be prescribed in women?
As in women of childbearing age, there is a high risk of major malformation in pregnancy.
Only prescribed if they meet the conditions of a
pregnancy prevention programme (contraception and signing of form)
What antiepileptic drugs are prescribed to women of childbearing age
Lamotrigine and particularly Levetiracetam are the safest
How does Epilepsy affect driving?
Need to ask all patients with seizures about
driving and will temporarily lose license and need to be seizure free for one year before reapplying
For bus lorry or coach drivers you need to be seizure free for 5 years off medication for a single seizure, or 10 years if had multiple Patients responsibility to inform DVLA
A 26 year old arrives in resus fitting. The ambulance crew state this began 10 minutes ago, she has received a single dose of IV lorazepam.
What is the first step in your management?
Primary assessment
Apply oxygen
2nd dose of benzodiazepines
Get help
You have treated her with further a further dose of lorazepam, and given a loading dose of phenytoin. It is 30 minutes later and she continues to fit. What do you do next?
Give thiopentone and call intensive care
She has now stopped seizing, and you see her in 2 weeks later in the epilepsy clinic. She is not on any contraception. Which of the following drugs should be avoided?
Valproate
