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4/ BAB > Brain Rhythms: Epilepsy > Flashcards

Brain Rhythms: Epilepsy Flashcards

1
Q

Define a seizure

What three words describe a seizure?

A
  • the clinical manifestation and excessive excitation of a population of cortical neurones
  • an abnormal synchronous, paroxysmal neuronal discharge in the brain causing abnormal function
  • SUDDEN, TRANSIENT, DISORDERLY
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2
Q

Define epilepsy

A

a tendency towards recurrent seizures unprovoked by systemic or neurological insults

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3
Q

What is epileptogenesis?

A

sequence of events that converts a normal neuronal network into a hyperexcitable network

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4
Q

What are the causes of symptomatic seizures?

A
  • drugs, stimulants intoxication or sedative withdrawal
  • severe sleep deprivation
  • cardiovascular disease: ‘reflex anoxic seizures’
  • seizures within 24 hours of stroke or transient ischaemia attack
  • seizures during intracranial surgery
  • seizures due to hypoglycaemia
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5
Q

Why does diagnosis matter when it comes to seizures?

A
  • seizures may be as a result of underlying systemic disease (e.g. vasovagal syncope, hypoxia, endocrine abnormalities
  • epilepsy has impact on life - driving licence, some jobs and pastimes
  • stigma associated with epilepsy
  • ‘pseudoseziures’ are important differential - need appropriate psychological and psychiatric treatment
  • misdiagnosis rates can reach 20-30%
  • eye witness descriptions of seizures are crucial
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6
Q

What does an EEG do?

A

record to the rhythmical electrical activity from the surface of the scalp

  • resultant signal reflects synchronous neural activity
  • represents currents due to synaptic excitation of dendrites of pyramidal neurones the cerebral cortex
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7
Q

What typical brain waves are seen during the following:

  • awake with mental activity
  • awake and resting
  • sleeping
  • deep sleep
A
  • awake with mental activity = beta
  • awake and resting = alpha
  • sleeping = theta
  • deep sleep = delta
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8
Q

What are the two main classifications of seizures?

Give examples of each

A 
Generalised 
- convulsive (tonic-clonic, or tonic-clonic-tonic)
- absence 
- atonic 
- myoclonic 
Focal (partial/local)
- simple - no altered consciousness 
- complex - altered consciousness
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9
Q

What are the characteristics of generalised seizures?

A
  • site of onset cannot be resolved to one hemisphree
  • can by symmetric or asymmetric
  • can include cortical and subcortical structures, but not necessarily the entire cortex
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10
Q

What are the characteristics and EEG findings of a generalised absence seizure

A
  • abrupt onset and offset of altered awareness
  • memory impaired
  • clonic movements of eyelids, chin, face
  • synchronous 3Hz spike and wave recorded over most of the scalp
  • associated with loss of awareness that can be mistaken for daydreaming
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11
Q

What is the mecahsnims of absence seizures?

What is the treatment?

A
  • interactions between thalamus and cortex
  • glutaminergic and GABAergic synapses generate rhthymcycity
  • manifests as 3Hz spike and wave oscillations
    Treatment = ethosuximide (t-type Ca2+ channel blocker)
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12
Q

What are the characteristsics of focal seizures?

A
  • orginates in a specific part of the brain (localised to one hemisphere)
  • duration 10s to 2-3mins
  • 60% of adult epilepsy
  • may be imparitement of awareness
  • features dependent on location of seizure activity
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13
Q

What is it called when a focal seizure spreads over both hemispheres?

A

secondary genrealisation

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14
Q

What is SUDEP?

A

Sudden Unexpected Death in Epilepsy

  • if a person with epilepsy dies suddenly and unexpectedly, and no obvious cause of death can be found, it is called SUDEP
  • cause is unknown - seizure activity changes heart rate/breathing - autonomic effect?
  • maybe, deplete energy resources
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15
Q

What are the risk factors for SUDEP?

A
  • poor seizure control
  • young adult (males)
  • seizures when alone
  • excessive alcohol
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16
Q

What is status epilepticus?

What is the mortality rate?

A

an epileptic seizure that lasts for 30mins or longer, or a series of seizures without regainign conciousness in between
- mortality approaches 50% in some series

17
Q

What are the causes of status epilepticus?

A
  • CV disease
  • inadequate anti-epileptic drug treatment
  • brain infection
  • cerebral trauma
  • tumour
  • alcohol and drug abuse
  • hypoglycaemia
  • metabolic disturbance
18
Q

What is Torsade de Point during epilepsy?

A
  • specific ECG finding during a seizure
  • heart beats abnormally
  • hyperventilation
  • heart may stop beating entirely
  • life threatening
19
Q

Describe the following two mechanisms of epilepsy

  • synchronicity of neuronal firing lost
  • excitation-inhibition balance
A

Divergent connection effective synapses, minimum aggregate
- need intrinsic membrane portenial
- voltage gated ion channels Na+ and Ca2+
- synaptic properties - glutamate and GABA
- need lots of abnormal cells to produce a seizure
Excitation-inhibition balance
- inihibiorty GABA neurones inhibit spread of electrical activity and chain reaction, lost in epilepsy

20
Q

What is the difference between symptomatic and idiopathic epilepsy?

A

Symptomatic
- identifiable cause e.g brain tumour, vascular malformation
- very much the minority
Idiopathic
- no clear cause, but thought to be low seizure threshold in otherwise normal brain
- usually no other disabilities and good response to drugs

21
Q

What are the causes of epilepsy in the following times of life:

  • infancy and childhood
  • childhood and adolescence
  • adolescence and adulthood
  • older adult
A 
Infancy and childhood 
- birth injury
- inborn errors of metabolism 
- congenital malformation 
Childhood and adolescence
- idiopathic/genetic syndromes 
- CNS infection 
- high fever 
Adolescence and adulthood 
- head trauma 
- inflammation 
Older adult 
- stroke 
- brain tumour
22
Q

What pahtoigies can be seen in the epileptic brain?

A
  • neurona migration disorders
  • head injury
  • tumours
  • inflammation
  • neuronal loss and gliosis
  • temporal lobe epilepsy is often associated with neuronal loss and lgioiss in the hippocampus
23
Q

Describe the genetics of epilepsy

A 
Mendelian causes - rare
- channelopathies 
- neuronal migration disorders 
Non-Mendelian and copmlex - more common 
-
24
Q

What are anti-epileptic drugs?

What is the goal of therapy?

A
  • a drug which dercrease the frequency and/or severity of seizures in people with epilepsy
  • treats the symptom of seizures, not the underlying epileptic condition
  • GOAL: maximise quality of life by minimising seizures and minimising adverse drug effects
25
Q

What are the excitatory and inhibitory targets of epilepsy drugs?

A 
Excitation (aim to reduce)
- ionic: inward Na+, Ca2+ currents 
- neurotransmitter: glutamate 
Inhibition (aim to increase)
- ionic: inward Cl-, outward K+ currents 
- neurotransmitter: GABA
26
Q

Give some examples of drugs that block excitation and how

A
  • Block Na+ channels = phenytoin, carbamazepine, valproic acid,
  • Block L-type Ca2+ channels = gabapentin,
  • Block NT release = levetiracetam
  • Block AMPA receptors = topiramate
  • Block NMDA receptors = felbamate
27
Q

Give some examples of drugs that promote inhibition and how

A
  • Promote Cl- entry = barbiturates, benzodiazepines,
  • Inhibit GAT1 channels = tigambine
  • Block GABA-T degration of GABA = vigabatrin
28
Q

What needs to be considered when choosing anti-eptiletpic drug treatment?

A
  • relative efficacy for an individual patients
  • tolerability and safety profile
  • simplicity of dosing
  • accurate dosing, and appropriateness for seizure type
29
Q

What drugs are used for partial epilepsy?

What is their mechanism of action?

A
  • carbamazepine - blocks voltage gated Na+ channels
  • lamotrigine - blocks voltage gated Na+ channels
  • oxcarbabazepine - blocks voltage gated Na+ channels
30
Q

What drugs are used for generalised epilepsy?

What is their mechanism of action?

A
  • sodium valproate - blocks voltage gated Na+ channels
  • lamotrigine - blocks voltage gated Na+ channels
  • levetiracetam - block NT release
31
Q

What is the important clinic consideration for carbamzapine and oxcarbazepine?

A

reduce effectives of oral contraceptive

32
Q

What is the first aid management of a seizure?

A
  • do not out anything into the mouth
  • protect the patient from immediate danger
  • protect the head from injury
  • place in recovery position as soon as possible
33
Q

What other treatments are there for epilepsy other than drugs?

A
  • vagal nerve stimulation
  • surgery - excision of epiptogenic focus
  • diet (ketogenic)
34
Q

What are the future developments for epilepsy management?

A
  • seizure prediction
  • improve therapeutic index and side effect profile
  • better targeting of underlying mechanisms
  • targets delivery of drugs
35
Q

What is meant by a tonic-clonic seizure?

What is meant by a tonic-clonic-tonic seizure?

A
  • types of generalised seizure
    tonic = body is rigid
    clonic = unctronlled jerking
36
Q

What is the difference between and simple and complex focal seizure?

A 
Simple = no altered conciousness
Complex = altered consciousness

4/ BAB (25 decks)

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