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Clinical Pharmacology > Epilepsy > Flashcards

Epilepsy Flashcards

1
Q

What is a seizure?

A

A transient occurence of signs or symptoms due to abnormal electrical activity in the brain, leading to a disturbance of conciousness, bhevaiour, emotion, motor function or sensation

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2
Q

What is the major excitatory neurotransmitter in the brain and by which receptor does it act?

A

Glutamate acting on the NMDA receptor

Lets Na+ and Ca2+ in and lets K+ out

More likely to fire action potential

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3
Q

What is the major inhibitory neurotransmitter in the brain and by which receptor does it act by?

A

GABA acting on the GABAA receptor

Cl- channel, hyperpolarises membrane → less likely to fire action potential

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4
Q

Explain the pathology behind seizures

A

A manifestation of abnormal + excessive excitation of neurones within the brain, either due to:

  • Loss of inhibititory GABA
  • Too strong excitation by NMDA/ Glutamate
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5
Q

What are some of the causes of epilepsy?

A
  • Genetic differences in brain chemistry/receptor structure
  • Exogenous receptor activation (drugs / alcohol)
  • Changes in brain chemistry - drug withdrawl, metabolic changes
  • Damage to brain - strokes, tumours
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6
Q

What are some of the signs and symptoms of epilepsy?

A
  • Shaking
  • Generalised seizures- loss of conciousness
  • Changes in muscel tone, tongue biting
  • Tonic-clonic seizures initial hypertonic phase followed by rpaid clonus (shaking)
  • Post-ictal period- minutes- hours
  • May have aura pre-seizure
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7
Q

What is the definition of epilepsy

A

The tendency toward recurrent seizures unprovoked by a systemic or neurological insult

Need at least 2 unprovoked seizures occuring more than 24 hours apart

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8
Q

What is a reflex seizure?

A

A seizure brought on by a particular stimulus

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9
Q

What kind of things can cause a reflex seizure?

A
  • Photogenic
  • Musicogenic
  • Thinking
  • Eating
  • Hot water immersion
  • Reading
  • Orgasm
  • Movement
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10
Q

What are the 3 broad classifications of seizure?

A
  1. Focal Onset - 1 side of brain, spreads slowly
  2. Generalised Onset- bilateral, spreads rapidly
  3. Unknown Onset
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11
Q

What are generalised seizures?

A

Originate at some point within the brain and rapidly engage bilaterally distributed networks

Can include cortical and subcortical structures not necessarily the entire cortex

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12
Q

What are focal seizures?

A

Seizures that originate within brain networks limited to one hemisphere

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13
Q

What is grand mal?

A

Grand mal= generalised seizure

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14
Q

What is Petit mal?

A

Petit mal= absence seizure

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15
Q

What is another term for partial seizure?

A

Focal seizure

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16
Q

What is a provoked seizure? Give examples

A

A seizure as a result of another medical contition

e.g.

  • Drug use/ withdrawl
  • Alcohol withdrawl
  • Head trauma/ intracranial bleed
  • Metabolic disturbance (hyponatraemia, hypoglycaemia)
  • CNS infection: meningitis and encephalitis
  • Febrile seizures in infants
  • Uncontrolled hypertension
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17
Q

How do you treat provoked seizures?

A

Treat the underlying condition

18
Q

What are some differential diagnosis of seizures?

A
  • Syncopal episodes
  • Cardiac issues (reflec anoxic seizures, arrhythmias)
  • Movement disorders e.g. Parkinsons, Huntingtons
  • TIAs
  • Migraines
  • Non epileptic attack disorder (pseudo-seizure)
19
Q

What is the initial management of a seizure?

A

Primary survery A→E assessment

Airway- it it patent, can you do anything about it?

Breathing - sats, oxygen

Circulation- expect HR to be high

Disability- Will hae reduced conciousness in generalised seizures but may be awake in partial

E- may want to get into recovery position if possible

20
Q

At what point should you administer drugs for seizures?

A

Should wait for 5 minutes to see if seizure still going then give seizure terminating drugs

Most seizures will self-terminate without drugs

21
Q

What is status epilepticus?

A

A seizure (any variety) lasting more than 5 minutes , or multiple seizures without complete recovery between them

Status epilepticus is a medical emergency

22
Q

What is the treatment for status epilepticus?

A
  • Wait 5 minutes
  • Benzodiazepines
  • Benzodiazepines again
  • Phenytoin (or maybe Levetiracetam)
  • Thiopentone (must be given by an anaesthatist)
23
Q

Explain how benzodiazepines work

A

Bind to GABAa receptor, increase Cl- conductance and taking neurones membrane potential away from threshold

24
Q

What must you be caredful of when prescribing benzodiazepines?

A
  • Addiction
  • Cardiovascular collapse (if giving too much, too quick)
  • Airway issues
25
Q

Give some other uses of benzodiazepines except for treating seizures?

A
  • Alchol withdrawl
  • Sleep aid
  • Anxiolytics
26
Q

Name the drug options of benzodiazepine that can be used in status epilepticus

A
  • Lorazepam (i.v.- 1st line choice)
  • Diazepam (rectally- difficult when shaking)
  • Buccal or intranasal Midazolam (hard to get into mouth when biting)
27
Q

What is used to help record electrical activity of the brain?

A

Electroencephalography

  • Useful but relies on capturing a seizure whilst wearing
  • Can bring on seizures by sleep depriving patient
28
Q

What is the imaging method of choice when investigating epilepsy?

A

MRI

May detect vascular or structural abnormalities to account for epilepsy

29
Q

Name 3 anti-epileptics that are sodium channel blockers

A
  1. Phenytoin
  2. Carbamezepine
  3. Lamotrigine
30
Q

Explain how sodium channel blockers work as anti-epileptics

A
  • Block Na channels in central neurones
  • This slows the recovery rate of neurones from inactive to closed state
  • Reducing neuronal transmission
31
Q

What are some of the side effects of carbamezepine (Tegretol)

A
  • Suicidal thoughts
  • Joint pain
  • Bone marrow suppression
32
Q

What is unique about the metabolism of carbemezepine

A

Carbemezepine induces its own metabolism

Induces CYP3A4 which is also the CYP that metabolises it

33
Q

What do you need to bear in bind when prescribing phenytoin?

A

Phenytoin exhibits zero order kinetics- take care when adjusting dose

34
Q

What are some specific side effects of phenytoin?

A
  • Bone marrow suppression
  • Hypotension
  • Arrythmias (if give i.v.)
35
Q

What is the mechanism of action of sodium valporate?

A

Works by a mixture of ways on the GABAA receptor and by increasing GABA synthesis

1st line treatment for generalised epilepsy

36
Q

What are some of the side effects of sodium valporate?

A
  • Liver failure
  • Pancreatitis
  • Lethargy
  • Avoid in pregnancy -high risk of congenital abnormality. Must make sure females of reproductive age are on a pregnancy prevention programme
37
Q

When is Lamotrigine used to treat epilepsy?

A
  • Good for focal epilepsy
  • Often used when sodium valporate is contraindicated in generalised epilepsy
38
Q

How does Levetiracetam (Keppra) work?

A

Novel mechanism, unclear

Thought to be a synaptic cleft glycoprotein binder that stops the release of neurotransmitter into the synapse to reduce neuronal activity

39
Q

What are some of the general side effects of anti-epileptic drugs?

A
  • Tiredness/ drowsiness
  • Nausea and vomiting
  • Mood changes and suicidal ideation
  • Osteoprosis (in older patients)
  • Rashes e.g. Steven Johnson more likely in carbamezepine or phenytoin
  • Many cause thrombocytopenia, anaemia or bone marrow failure
40
Q

What is the effect of carbemezepine and phenytoin on other drugs

A
  • Reduces effectiveness of oral contraceptive pill
  • Reduces effectiveness of some antibiotics
41
Q

What are the safest anti-epileptics to use in pregnancy?

A
  • Lamotrigine
  • Levetiracetam
42
Q

What is the impact on epilepsy and driving?

A
  • Will lose lisence
  • Patients responsibility to inform DVLA
  • Need to be 1 year seizure free before reapplying
  • Need to be 5 years seizure free off medication if a bus, lorry or coach driver

Clinical Pharmacology (25 decks)

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