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Drugs and diseases-2106 > Epilepsy > Flashcards

Epilepsy Flashcards

1
Q

What is epilepsy?

A
  • Family of nurological disorders charachterised by recurrent seizures
  • Affects~3% of the population
  • Manifests as periods of synchronus hyperexcitability in networks of neurons
  • Can be detected by EEG during intercital period
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2
Q

What is the basis of epileptognesis?

A
  • Cellular/molecular basis of epileptogenesis is multifactorial and incompletely understand
  • Essentially an imbalance between excitatory and inhibitory drives
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3
Q

How does epilipsy present?

A
  • Focal or partial seizure
  • Generalised seizure
  • Tonic-clonic seizure (Grand mal)
  • Absence seizure (Petit mal)
  • Myoclonic seizure
  • Lennox-Gastaut sendrome
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4
Q

What is generalised tonic-clonic epilepsy?

A

Archetypal form of epilepsy

Tonic phase:
1. Loss of consciouness
2. Muscle rigidity
3. Typically lasts for 10-30 seconds

Clonic phase:
1. Muscle twitching
2. Convulsions
3. Lasts up to several minutes

Postictal phase:
1. Confusion and amnesia
2. Fatigue/sleep
3. Headache, hypertension, nausea

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5
Q

What are treatment approaches?

A
  1. Anticonvulsant or Anti-epileptic drugs (AEDs)
  2. Surgical resection
  3. Vagus Nerve stimulation
  4. Deep Brain stimulation
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6
Q

How is surgery used in treatment of Epilepsy?

A
  • Remove regions of the cortex where focal episodes begin
  • Temporal lobe epilepsy is the commonest
  • Resection from pole to lobe, with care to preserve language and memory centres
  • Success rates with other focal points range from 30-80% depending on region
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7
Q

What is Vagus nerve stimulation?

A
  • Reduce number of seizures by >50% in 20-40% of patients

Side effects:
* Hoarse voice
* Headache
* Pain

  • Driving with ~30Hz stimulation pulses triggers central noradrenergic signalling
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8
Q

What is Deep brain stimulation?

A
  • Experimental
  • Electrode implanted into thalamus to interrupt spreading excitation

Side effects:
* Cranial bleeds
* Infection

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9
Q

Explain anti-epileptic drugs.

A
  • Wide range of AED in clinical use
  • Patients often need combinatorial treatment with two or more drugs to effectively manage symptoms
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10
Q

What are the 4 key pharmacological mechanisms?

A
  1. Voltage gated sodium channel block
  2. Voltage gated calcium channel block
  3. Inc GABA transmission
  4. Dec Glutamate transmission
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11
Q

What is Sodium valproate/valproic acid?

A
  • Anti-epileptic activity discovered and patented in 1960s
  • Marketed as Epilim
  • Other indications:
    1. Migraine
    2. Bipolar disorder
    3. Anxiety disorder
    4. Mood disorders
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12
Q

What are side effects of Sodium valproate?

A
  1. Nausea/vomiting
  2. Sleepiness
  3. Dry mouth
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13
Q

What is Valproate’s mechanism?

A
  • Targets GABAergic inhibitory transmission
  • Inhibits GABA degrading enzymes
  • Enhances and prolongs GABA transmission
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14
Q

What are additional effects of Valproate?

A
  • Block of VG-Na, K, Ca channels
  • Inhibition of histone deacetylase
  • weak inhib of NMDA receptor (glutamate) signalling
  • Disruption of Wnt and ERK signalling pathways
  • Supresses high freq firing and affects cell survival , homeostasism cytoskeletal structure etc
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15
Q

What is Lamotrigine?

A
  • Dev in wellcome labs in 1980s and release in 91
  • Marketed as Lamictal

Other indications:
* Bipolar disorder
* Schizophrenia

Side effects:
* Rash
* Nausea/vomiting
* Sleepiness
* Headache

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16
Q

What is the mechanism of action for Lamotrigine?

A
  • Block of VGSC
  • Selective action at high-freq
  • Use-dependent block of inactivation channels
17
Q

What are additional effects of Lamotrigine?

A
  • Block of VGCC
  • Inhibition of 5-HT3 receptors (Cation channel)
  • Overall effect is dec in excitatory transmission, red overall glutamate release
  • Use dependent mechanism means normal action potential propagation is unaffected, but hyperexcitability is blocked
18
Q

What is Gabapentin?

A
  • Dev in 1975 and release in 94
  • MArketed as Neurontin

Other indications:
* Neuropathic pain
* MS
* Not approved for generalised seizures

Side effects:
* Dizziness
* Fatigue
* Ataxia

19
Q

What is Gabapentin’s mechanism of action?

A
  • Intended as GABAaR agonist, but little activity
  • Blocks high-voltage activated (HVA) calcium channels
  1. Depolarisation opens HVA channels
  2. Calcium infulx triggers vesicle fusion
  3. Gabapentin reduces glutamate release
20
Q

What are additional effects of gabapentin?

A
  • No obv effects on GABA receptors or GABA release
  • Inc tonic GABA conc in brain slices
  • Mech unclear–Block of reuptake or inc synthesis
  • Confusing mix of evidence

Drugs and diseases-2106 (38 decks)

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