Lecture 3: Epilepsy and Neuroplasticity

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What is epilepsy classified as?

brain disease

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Definition of epilepsy

chronic medical condition produced by temporary changes in the electrical function of the brain, causing seizures which affect awareness, movement, and/or sensation

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% of the population affected by epilepsy

0.5-1%

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Who is most affected by epilepsy

children and the elderly

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Duration of epilepsy

chronic- can be life long, or a few years

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What type of population distribution does epilepsy have?

bimodal for age

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Simply, what happens to brain waves causing seizures?

big synchronisation of waves of activity → seizures

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Cause of epilepsy

idiopathic

  • no single cause

  • often no known clear cause as to why sm1 is experiencing epilepsy and why they are at a specific time

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Factors that may cause epilepsy

brain injury, swelling in brain, hydrocephalous

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What determines epilepsy symptoms?

type of epilepsy and location of epileptic activity

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Is a diagnosis of ‘epilepsy’ that useful?

  • no

  • not very informative or useful

  • b/c heterogeneity of disease types

  • affect individual differently

  • require treatment/adjustment in different ways

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Two main subtypes of epilepsy

  • partial

  • generalised

(big distinction between two)

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Partial epilepsy

not involving whole brain

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Generalised epilepsy

involving much wider range of functions

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What does knowing the type of epilepsy enable?

knowing type of seizure, when might happen, why might happen, what is required

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Partial epilepsy: seizures

  • simple partial seizures

  • complex partial seizures

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Generalised epilepsy: seizures

  • grand mal seizures

  • petit mal seizures

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Simple partial seizures: neural level

  • localised to specific areas of brain

  • problematic electrical activity, overly synchronised waves of neurons → only in one part of brain

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Simple partial seizures: effects

  • localised effects according to localisation of epileptiform activity

  • usually sensory and/or motor

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Jacksonian March

  • simple partial seizures

  • wave of sensation travelling down arm

  • localised jerking beginning in hand and progressing to clonic movements of entire arm (focal motor seizure))

  • produced by epileptiform activity in the motor cortex that controls the arm

    → can infer movement in seizure activity and spread re sensory and motor changes in arm

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What does this describe:

“localised jerking beginning in right hand and progressing to clonic movements of entire right arm”

partial epilepsy > simple partial seizure > Jacksonian March

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Complex partial seizures are also referred to as…

  • focal onset impaired awareness seizures

  • temporal lobe epilepsy

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Complex partial seizures: neural level

  • partial

  • localised to specific brain areas

  • common localisation in temporal lobe (about 50% adult epileptics are complex partial, temporal lobe)

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Complex partial seizures: effects

  • associated with apparently ordered/ co-ordinated, but inappropriate, motor behaviour

    • e.g.: running, chewing, buttoning

  • may be absent (impaired consciousness)

    • partial consciousness, moving about, awareness impaired

    • could know someone is speaking but be unable to respond

  • lasts a few mins

  • often no memory of episode

  • quick recovery time

  • focus on impaired awareness, but some motor symptoms

  • no running awareness through period of seizure even though may appear quite normal

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Earliest start point of partial seizure

aura

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What do auras precede?

partial seizures

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Aura: definition

abnormal sensations, e.g.:

  • sense of fear, doom

  • rising feeling in abdomen

  • strange tastes or odours - ‘metallic’

  • sensory disturbances

  • visual sensations akin to hallucinations

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Cause of aura

  • abnormal electrical activity originating from seizure focus

  • epileptic activity starts to increase before huge waves → low level changes

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What are petit mal seizures also referred to as?

absence seizures

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Petit mal seizures: neural level

  • can involve entire brain

  • large area of brain disrupted by seizure activity

  • generalised

  • whole brain, but at quite low level

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What can petit mal seizures appear like?

conscious seizures

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Petit mal seizures: effects

  • person briefly ‘absent’

  • disrupted consciousness

  • very brief, sometimes just 1 sec

  • may look like zooming out

  • can have some eye or lip movement resembling normal movement

  • able to maintain stream of dialogue sometimes

  • unaware

  • gaps - like a pause button

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Petit mal seizures + school children

  • can be seen as daydreaming, not paying attention

  • miss things in class and be unaware

  • unaware during brief absence seizure episodes

  • difficult to pick up on

  • important to diagnose and pick up early on

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Why is absence different to partial seizure?

can’t do any level of interaction

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Which two seizure types have high overlap?

petit mal and complex partial

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Petit mal most common in…

  • children

  • tends to subside or reduce after puberty

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Grand mal seizures: neural level

  • can involve whole brain

    • usually does to some level

  • generalised

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Grand mal seizures aka as…

tonic clonic seizures

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Tonic phase

rigidly extend limbs

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Clonic phase

jerks in all extremities

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Grand mal seizures: effects

  • may lose consciousness and/or fall to ground

  • rigidly extend all limbs (tonic phase)

  • then have jerks in all extremities (clonic phase)

  • tend to make more of impact bc of nature of it

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Commonality of grand mal seizures

  • less common than other types

  • lot of epilepsy not this

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Are types of epilepsy mutually exclusive?

no

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Further spreading of epileptic activity

  • partial seizures can generalise

  • can begin w/ partial seizures that then becomes generalised epilepsy

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<p>What does this show?</p>

What does this show?

  • partial seizure generalising

  • in focal: normal in 1 and 2, abnormal in 3 and 4

  • after a while, may spread, so abnormal in 1,2,3,4

  • referred to as focal with secondary generalisation

  • can also spread to thalamus, and via the thalamus

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Thalamus

big group of nuceli at base of brain, relay station

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<p>What does this show?</p>

What does this show?

  • generalised seizure

  • primary generalised seizure

  • abnormal in 1,2,3,4

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How do seizures generalise?

  • capacity for seizure activity to spread and spread through major connecting pathways in brain

  • can spread to/via the thalamus

  • big white matter pathways linking millions of neurons

  • seizure activity in group of neurons > neurons connected to other groups of neurons through axons/white matter pathways > seizure activity can transfer across

  • transfer pathways = (usually) big white matter pathways

  • connection between left and right hemisphere- corpus callosum- enables spread

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Transfer pathways

usually big white matter/ myelinated axon pathways linking millions of neurons

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What is white matter made up of?

myelinated axon pathways

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