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B33CNS > Epilepsy Causes and Treatments (O'Donoghue M DR) > Flashcards

Epilepsy Causes and Treatments (O'Donoghue M DR) Flashcards

1
Q

What goes wrong in a seizure?

A

Hyper-synchronised activity within a neural network

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2
Q

What varies between different types of seizure?

A

Pattern of epileptic discharges, circuits involved, likely cause, drugs for treatment, chance of cure (also varies between patients).

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3
Q

Why are some people prone to seizures?

A

Brain lesions and disorders of channels or receptors

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4
Q

How do anti-epileptic drugs work?

A 
They target neuronal channels and neurotransmitter receptors:
Na+ K+ Ca++
GABA and Glutamate 
SV2a
Cannabinergic mechanisms
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5
Q

What is a ‘seizure’?

A

Clinical manifestation of a disordered and hyper-synchronised discharge in a network of cerebral neurons

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6
Q

How do we study seizures clinically?

A

Careful history from patient and witness
Home videos of seizure
Combined video-EEG
Result > Classification of seizures

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7
Q

What determines the type of seizure?

A

Location of onset
Type of discharge
Patter of spread

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8
Q

Where does a generalised seizure start?

A

Both hemispheres simultaneously

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9
Q

Where does a focal seizure start?

A

Seizure starts in a focus and then spreads

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10
Q

What three types of generalised seizures are there?

A

Typical absence
Myoclonic
Tonic-Clonic

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11
Q

When is the onset of Absence Seizures? How do they manifest?

A 
Onset in childhood mainly 
Frequent, brief attacks (1-30s)
Sudden loss and return of consciousness
No aura or post-ictal state
Some involuntary movements
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12
Q

What is the presentation of a Myoclonus Seizure?

A

Sudden, bried, shock-like muscle contraction
Usually bilateral arm jerks
Often worse in the morning
Precipitated by sleep deprivation and alcohol
Occurs in Epilepsy syndromes and certain non-epileptic causes

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13
Q

What are tonic-clonic seizures?

A

Sudden onset, gasp, fall
Tonic phase (stiff) with cyanosis (blueish discolouration)
Clonic phase
Post-ictal phase - confusion, exhaustion, disorrientation
Tongue bitten and incontinence
Noisy breathing
Headache and muscle pain afterwards

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14
Q

What three sub groups are there to Uncommon Generalised Seizures?

A

Atypical absence
Tonic - stiff
Atonic a.k.a drop seizure
Usually associated with severe epilepsy

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15
Q

What are the features of Focal (Partial) Seizures?

A

Focal onset means there is often an aura (warning to the beginning)
As seizures spread, a ‘complex partial seizure’ develops with loss of awareness and automatisms
In a ‘simple partial’, awareness is maintained, but in a ‘complex partial’ when the seizure spreads, alertness and awareness is lost.

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16
Q

In Focal Seizures the location of onset determines the seizure symptoms - which zones are potential sites?

A

Temporal lobe
Frontal lobe
Occipital lobe
Parietal lobe

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17
Q

What presents in a temporal lobe seizure?

A

Aura
-epigastric rising sensation, olfactory and gustatory (smell and taste)
-De ja vu
In a complex partial seizure starting in the temporal lobe; arrest reaction and blank stare, oral automatisms (lip smacking) and manual automatisms.

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18
Q

What is the hallmark EEG of generalised seizures?

A

Bilateral activity spike in waves

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19
Q

Are tonic clonic seizures ever seen in focal epilepsy?

A

Yes, the final culmination of a focal seizure

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20
Q

What are the key regulators in neuronal activity? Channels

A

Non-gated
Voltage-gated
Ligad-gated

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21
Q

Which receptors are key regulators in neuronal activity?

A

Metabotropic receptors (second messenger role)

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22
Q

Which cells have a role in neuronal activity?

A

Glia (astrocytes)

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23
Q

What is Ictogenesis?

A

The generation of a seizure

The inter-ictal spike; a short burst of epileptiform activity lasting 200ms

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24
Q

What is an inter-ictal spike?

A

A burst of activity by Na+ activity

An abnormal process / phenomenom

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25
How does neuronal firing differ in seizures compared to normal?
Burst firing behaviour of neurons | When the firing becomes hyper-synchronised this leads to a seizure.
26
In absence seizures what is cut off?
Sensory input and inter-neurons are lost
27
What are the two modes of firing of thalamic neurons?
Burst mode or tonic mode
28
What happens if you make the cortex hyper-excitable?
Causes spike and wave - absence seizure like events / discharges.
29
What happens if you stimulate the frontal cortex or intra-laminar thalamic nucleus?
Causes spike and wave - absence seizure like events / discharges.
30
During human spike and wave discharges, where can these be measured?
Thalamus - (in absence seizures).
31
What is the pathophysiology of absence seizures?
There are connections between thalamus - cortex and the thalamus itself also contains loops. The membrane and synaptic nature of these neurons in loops causes oscillations. disturbances to these oscillations may cause spike wave firing.
32
What goes wrong in absence seizures?
Primary abnormality may be bursts of abnormal activity from the cortex to the thalamus Thalamus may have a role in synchronising The reticular nucleus inhibits TC relay cells which may underlie the "absence".
33
What parts of the brain are involved in tonic-clonic seizures?
Basal ganglia / brain stem involved. Substantia nigra has gating function for severity of seizure.
34
What is the function of the basal ganglia?
The substantia nigra is the source of the striatal input of the neurotransmitter dopamine, which plays an important role in basal ganglia function.
35
What is Epileptogenesis? How does it develop?
Changes occur to : Neuronal channels, receptors (play a role in pathophysiology) Gap junctions Glia: buffering of extracellular environment BBB and inflammation Loss and reorganisation of synapses Cell loss inhibitory neurons Inherited channel defects can cause epilepst (Dravet syndrome) Some acquired epilepsies show changes in dendritic channel functions
36
What is Dravet syndrome?
Lost inhibitory neurons therefore increased neuronal firing
37
What is one of the main drug targets in epilepsy and why?
Sodium channels They are use and voltage dependent Prolongs the inactivated state of channel The strength of the block increases with repetitive activation Reduces burst firing
38
What properties are needed to block Na+ channels for therapeutic effect?
``` Drugs bind poorly to resting Na channels Fast inactivation (normal) is not affected Binding with prolonged depolarisations Main action is to stop the spread of the seizure (the onset of block is slow, can't stop all spikes but can prevent spread) ```
39
How does Lacosamide work?
Binds to Nap selectively in order to stop persistent sodium current
40
What kind of sodium channel mutation can lead to epilepsy?
Some mutations in sodium channels give increased function to Na p --> this can lead to persistent sodium current Some brain lesions may also have increased Na p channels "acquired channelopathy"
41
How can Lamotrigine worsen some epilepsy?
Patients with a mutation that results in loss of function in sodium channels might have epilepsy worsened by Lamotrigine because inhibitory neurons are inhibited further.
42
How is GABA manipulated by AEDs?
Enhancing Cl current at GABA receptors promotes inhibition of neuronal firings Reducing GABA degradation or reuptake to maximise amount at synaptic cleft.
43
How do Benzodiazepines, Barbiturates and Topiramate work as anti-epileptics?
Enhance Cl current at GABA receptors = inhibition
44
How does Vigabatrin and Tiagabine act as AED?
Vigabatrin is a GABA transaminase inhibitor Tiagabine is a GABA reuptake inhibitor These higher GABA levels prevent the fading of inhibition.
45
How does Retigabine work? (WITHDRAWN)
Augments potassium channel | Currently withdrawn due to possible retinal side effects
46
How does Perampanel work?
Highly selective non-competitive AMPA antagonist Inhibits excitatory transmission Side effect = patients can become violent as a result
47
Which AEDs are particularly poorly understood?
Valproate NA K CA GABA NMDA? Gabapentin and Pregabalin Ca, GABA, NMDA? Levetiracetam SV2a?
48
What are the key points to epilepsy management?
Ensuring correct diagnosis Determining the cause Deciding on treatment Advising on life-style issues
49
What are some of the non-epileptic causes of seizures and 'black outs'?
``` Epilepsy Fainting Cardiac causes Attacks with psychological causes Rarities ```
50
The epilepsy is then classified by what factors?
``` Seizure type EEG MRI Family history Associated causes Treatment and prognosis determined from this ```
51
What is idiopathic epilepsy?
No neurological damage Often responds well to treatment Genetic component suspected
52
What is symptomatic epilepsy?
Seizures are the symptoms of lesion, tumor, stroke etc | Focal and harder to treat, more resistant to treatment an d have associated neurological defects.
53
What are the causes of symptomatic epilepsy?
Cortical malformations (from birth due to hypoxia) Cerebral palsy Genetic and metabolic disorders Hippocampal sclerosis (convulsions as an infant) Trauma and Infection
54
What are the principles of treatment with reference to The disorder The patient The drug
The disorder - diagnosis must be certain The patient - wants treatment and is counselled about it The drug - is appropriate for the syndrome, low dose initially, side effects and interactions are explained
55
Initial treatment options fro generalised epilepsy?
Sodium valproate | (child-bearing) Lamotrigine
56
Initial treatment for focal epilepsy?
Lamotrigine
57
What are the benefits to using Lamotrigine?
Broad spectrum 1st line Focal and generalised Well tolerated, safer for women of a child-bearing age
58
How does Carbamazepine work?
``` Acts on sodium channels to suppress burst activity and spread of seizures Not helpful (makes worse), for myoclonus or absences. ```
59
How does Valproate work?
Unknown action GABA, inhibits excitatory transmission via Ca or K? 1st line for partial and generalised seizures Important for myoclonus, absences and photosensitive seizures also
60
How does Phenytoin wok?
Acts on sodium channels Suppresses burst activity and spread of seizures Not helpful for myoclonus and absences Useful in emergencies
61
Which AED is helpful for myoclonus or absence seizures?
Valproate | Topiramate
62
What is a problem in the administration of phenytoin?
Zero order kinetics, metabolism is not linear
63
How does Levetiracetam work?
Potent broad spectrum agent, targets synaptic vesicle protein 2a, well tolerated
64
What are the problems associated with enzyme inducing drugs?
Reduced combined oral contraceptive, antimicrobials, anti-virals, analgesics, oncology drugs, warfarin
65
What is Status Epilepticus?
A medical emergency Rapid treatment: IV Benzodiazepine and phenytoin IV levetiracetam or valproate or lacosamide General anesthesia
66
Which non-pharmacological treatments can be recommended for epilepsy?
Vagal nerve stimulation Resection of epileptic focus Ketogenic diet
67
What are the potential future treatments for epilepsy?
Gene therapy Deep brain stimulation Optogenetics; harnessing the power of light!
68
What are the consequences of epilepsy?
``` Loss of employment, driving license Stigmatisation and anxiety Needing AED Problems with contraception and conception Injuries and mortality ```
69
Overview of Drug Use
Absence: valproate, ethosuximide, lamotrigine, benzos Myoclonus: valproate, benzos, levetiracetam GTC; CBZ, LTG, valproate, phenytoin, topiramate Focal: carbamazepine, lamotrigine, topiramate, levetiracetam

B33CNS (20 decks)

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