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PL6009 Neurology > EEG > Flashcards

EEG Flashcards

1
Q

What is EEG

A

electrical activity of the brain measured on the scalp surface

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2
Q

Name the lobes of the cerebral cortex

A

Frontal, parietal, occipital and temporal

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3
Q

What are sulci

A

the grooves (low parts)

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4
Q

What a gyri

A

the bumps (raised parts)

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5
Q

How many layers are in the cortex

A

6 (I to V)

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6
Q

Which neuron type generate EEG

A

pyramidal neurones

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7
Q

Explain EPSP

A

depolarizations induced by a neurotransmitter
Usually receptor linked to Na/Ca entry into cells.
Example- NMDA/AMPA

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8
Q

Explain IPSP

A

hyperpolarization
usually K/Cl
example- GABA

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9
Q

What layer are pyramidal neurons in

A

layer V

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10
Q

where do pyramidal neurons project

A

Layer I

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11
Q

what kind of flow of current do EPSP cause

A

vertical

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12
Q

how are pyramidal cells orientated

A

vertically

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13
Q

what do coordinated EPSP generate

A

a current sink (this is what is picked up on scalp surface)

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14
Q

What deflection does activity in cortex layer 5 cause

A

positive (downward)

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15
Q

what deflection does activity in cortex layer 2 cause

A

negative (upward)

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16
Q

What is a dipole in terms of EEG

A

separation of charge over distance
This is what EEG picks up

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17
Q

Explain EEG rhythms

A

neuronal networks have intrinsic rhythmicity with pacemaker cells in the thalamus
they generate feedback loops with cortex (thalamo-cortical circuit)

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18
Q

What is paroxysmal depolarization shift

A

sustained period of neuronal depolarization
may get superimposed action potential
primary cause of epileptiform spikes

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19
Q

what is the primary cause of epileptiform spikes

A

paroxysmal depolarizing shifts.

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20
Q

What are the types of electrodes:

A

silver/silver chloride
gold collodion
re-useable
disposable

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21
Q

name the electrode placement system

A

10:20 system

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22
Q

What planes are the head divided up into

A

coronal, sagittal, horizontal

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23
Q

what other physiological parameters are measured during EEG

A

ECG
EMG
eye movement

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24
Q

what side is odd and even number correlated with

A

odd - left
even - right

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25
Q

What is a montage in EEG

A

refers to the arrangement of electrodes used in your recording measuring potential difference

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26
Q

What is a bipolar montage

A

chains of electrodes (a-b, b-c, c-d)
can be longitudinal or transverse

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27
Q

what is a referential montage

A

a-r, b-r, c-r
common reference used to compare all electrodes to

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28
Q

Negative potential has a ….

A

upward deflection

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29
Q

and upward deflection is a….

A

negative potential

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30
Q

What are examples of common references in referential montage

A
  1. vertex (Cz)
  2. Mastoid (A1-A2)
  3. to external point (neck)
  4. average (AvRef)
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31
Q

what amplifier is used in EEG

A

differential

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32
Q

what is normal gain/sensitivity of EEG

A

7 mV/mm

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33
Q

Why is a low pass filter used in EEG

A

for muscle/electrical noise
very little useful bio-electrical activity >70Hz

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34
Q

Why is a high pass filter used

A

for sweat artefact/ respiration
normally set at 1Hz

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35
Q

Why is a notch filter used

A

50Hz - mains

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36
Q

Explain the time constant in EEG

A

The time in seconds required for the signal to attenuate by 37% of it’s original value

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37
Q

What is an impedance check

A

A means of checking the integrity of each electrode
>5kOhms
should be done prior/post any recording.

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38
Q

What are usual EEG display setting

A

30mm/sec, 10s/page

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39
Q

Give examples of artefacts

A

is activity not generated by brain
muscle, movement, eye movement, eyelids, ECG

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40
Q

Name the two activation protocols in EEG

A
  1. Hyperventilation (3 mins)
  2. Photic stimulation (2-20-50-30-25 Hz)
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41
Q

What general factors are used to describe background EEG

A

frequency, location, symmetry and responsiveness

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42
Q

What is the frequency for alpha

A

8-13Hz

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43
Q

what is frequency of beta

A

> 13 Hz

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44
Q

what is frequency of theta

A

4-8 Hz

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45
Q

what is frequency of delta

A

0.5 - 1 Hz

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46
Q

How do you determine localization from EEG

A
  1. what electrode is its highest amplitude (referential montage)
  2. phase reversal in bipolar chain
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47
Q

Describe healthy EEG in terms of symmetry

A

both hemispheres usually symmetrical
synchronous

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48
Q

Describe features of a normal adult EEG

A

alpha rhythm that is posterior dominant and blocked on eye opening
Mu rhythm
lambda waves

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49
Q

what are lambda waves

A

bilateral symmetric sharply contoured positive occipital waves with a sail like appearance
seen on eye opening

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50
Q

what is mu rhythm

A

prominent in children and young adults
frequency of approx 9Hz
mainly in central regions - unilateral
blocked by movement of contralateral limb

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51
Q

List the ‘states’ of sleep

A

drowsiness
N1
N2
N3
REM

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52
Q

What are featured of N1 stage

A

alpha dropout
vertex sharp waves

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53
Q

What are features of N2

A

vertex sharp waves and K complex - spindles

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54
Q

What are features of N3 sleep

A

spindle and delta

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55
Q

What is feature of stage 4 sleep

A

delta

56
Q

what are features of REM sleep

A

alpha
visible eye movements

57
Q

Describe vertex sharp waves

A

located to vertex
Cz - high amplitude
Broad V shaped
striking feature of light sleep

58
Q

Describe K complexes

A

sharp wave + slow wave + spindle
seen in stage 2 sleep
maximal in vertex / midline

59
Q

Describe progression of physiological coma

A

beta activity
increasing theta activity
increasing delta (maybe IRDA)
suppression bursts
isoelectric

60
Q

what does isoelectric mean in EEG

A

complete loss of cortical activity

61
Q

How does coma differ from adult awake

A

theta/delta (which is abnormal in awake adult)
discontinuity

62
Q

List some causes of encephalopathy

A

medications
metabolic disturbances (Na, urea, NH3)
hypoxia
encephalitis (infections/auto-immune)

63
Q

List some infections which cause encephalitis

A

herpes simplex
varicella
and other viruses
bacteria abscess
fungi

64
Q

Name some metabolic disturbaces

A

ammonium toxicity (hepatic encephalopathy)
uremia
toxicity - centrally active medications (benzos, barbiturates, opioids)

65
Q

List pathological EEG features in coma

A
  • PLEDS (periodic lateralized epileptiform discharges)
  • triphasic complexes
  • asymmetry
  • desynchrony
  • extreme delta brush
66
Q

In what clinicals scenarios do you get PLEDS

A

represent acute focal neurological disturbances
- stroke
- focal infection (herpes simplex)
- focal inflammation (auto-immune encephalitis)

67
Q

In what clinical scenarios do you find triphasic complexes

A
  • a wide range of encephalopathy
  • hypoxia
  • NH3 (liver)
  • uremia (kidneys)
  • prion
68
Q

What is extreme delta brush associated with

A

anti-NMDA encephalitis

69
Q

What features of an EEG would be considered normal in children

A
  1. delta initially (0-3 years)
  2. theta (3-6 years)
  3. some theta even in adolescence
  4. dominant rhythm gradually increases with age.
  5. 8Hz by 3 years old
  6. Can be asymmetric
  7. alpha sub harmonic
  8. posterior slow waves
70
Q

What is epilepsy

A

a predisposition to recurrent seizures

71
Q

How does a seizure manifest

A

may be brief period of involuntary movement, may be a brief disturbance of consciousness,

72
Q

What are the types of epilepsy

A
  1. Partial/focal (frontal, temporal, parietal, occipital, secondary generalized)
  2. generalized
73
Q

What are some causes for epilepsy

A
  1. structural brain abnormalities (tumors, stroke, abscess, congenital).
  2. focal inflammation
  3. genetic disorders (channelopathy - SCN, KCN etc., CaCN)
74
Q

How do focal/partial seizure of motor cortex manifest

A

twitching of contralateral limb (Jacksonian March)

75
Q

How do focal/partial seizure of occipital lobe manifest

A

visual hallucination

76
Q

How do focal/partial seizure of temporal lobe manifest

A
  • memory disturbances
  • automatisms (picking at bed clothes/rubbing head)
  • dystonic posturing of contralateral limb
  • autonomic sensation - epigastric rising sensation
  • heart rate disturbance (bradycardia/tachycardia)
77
Q

How do focal/partial seizure of frontal lobe manifest

A
  • supplementary motor area - fencing posture/head deviation
  • violent movements
  • sudden short lived seizures often out of sleep
78
Q

what are the types
of generalized seizures

A

tonic clonic
myoclonic - brief shock like movements
absence - brief periods of staring/unawareness

79
Q

What is a secondary generalized seizure

A

starts as partial seizure - becomes a generalized seizure

80
Q

What is status epilepticus

A

a continuous seizure or frequent seizures - with no recovery of normal brain function
generalized - convulsive - medical emergency
partial/absence - non-convulsive

81
Q

What medications are used to treat seizures

A
  1. carbamazepine
  2. levaracetam
  3. lacosamide
  4. sodium valporate
  5. benzos
82
Q

What methods are there to treat seizures

A

medication
or surgery (localize and remove epileptogenic zone - mesial temporal area)

83
Q

What is the role of EEG in epilepsy

A

functional test
high temporal resolution
interictal abnormalities
ictal abnormalities

84
Q

What is the sensitivity of EEG

A

low (50%)
thus normal EEG does not exclude epilepsy

85
Q

How is the specificity of EEG

A

high specificity - rule in test
abnormal EEG gives a precise classification, allows us to predict prognosis and decide management

86
Q

What are some interictal features of EEG

A

sharp waves/spikes/ associated slow waves
represent paroxysmal depolarizing shifts

87
Q

how do you localize focal abnormalities

A

phase reversal (bipolar)
or highest amplitude (referential)

88
Q

Describe a seizure/status epilepticus on EEG

A
  • dynamic process
  • evolving frequency and amplitude
  • evolving anatomical location
  • start/middle/end
89
Q

What is asymmetry a sign of

A

focal encephalopathy or structural lesion

90
Q

Describe ictal interictal continuum

A
  • discharges that are epileptiform and continuous
  • do not fulfil the criteria for an electrographic seizure
    example - PLEDS, triphasic complexes
91
Q

What are strengths of EEG

A
  • can be done immediately and anywhere
  • can be used to monitor progression
  • high temporal resolution
92
Q

what are weaknesses of EEG

A
  • poor spatial resolution
  • broad differential of patterns
93
Q

Why are electrochemical syndromes important

A
  • Help look for appropriate causes (imagine/genetics)
  • give accurate prognostication
  • helps decide treatment
94
Q

What are the broad groupings for electroclinical syndromes

A

Epileptic encephalopathies
benign partial epilepsies
genetic generalized epilepsy

95
Q

What EEG feature is seen in Otahara syndrome

A

Suppression burst

96
Q

What EEG feature is seen in West Syndrome

A

hypsarrhythmia
- high amplitude
- chaotic
- multi focal spikes
- electro decremental seizures

97
Q

what EEG feature is seen in Lennox-Gaustaut syndrome

A

slow spike and wave (1 or 2 Hz)

98
Q

What EEG feature is seen in Landau Kleffner

A

increasing epileptiform features as child enters sleep with continuous spike and wave in sleep

99
Q

What EEG feature is seen in Panaytiopolous syndrome

A

occipital spikes / multifocal
spikes in posterior quadrant usually but not necessarily

100
Q

Explain Gastaut type

A

in older children
visual hallucinations
occipital spikes

101
Q

Explain genetic generalized epilepsy

A

a looser classification
better prognosis than epileptic encephalopathy
developmentally normal
usually no cause found
normal genetics/brain imaging

102
Q

What EEG features are for genetic generalized epilepsy

A

generalized spike and wave during hyperventilation and photic stimulus

103
Q

List types of genetic generalized epilepsy

A
  1. childhood absence
  2. juvenile absence
  3. juvenile myoclonic
  4. absence with eyelid myoclonus
104
Q

what EEG feature is seen in childhood absence epilepsy

A

3 Hz spike and wave

105
Q

What EEG feature is seen in juvenile myoclonic seizures

A

polyspike and wave

106
Q

Describe extreme delta brush

A

super imposed higher frequency activity

107
Q

What is the general physiology of a seziure

A

transient disturbance in function in a group of brain cell with excessive electrical activity

108
Q

Name the epileptic encephalopathies

A
  • Otahara syndrome
  • west syndrome
  • lennox gastaut
  • landau kleffner
109
Q

What are some general characteristics of epileptic encephalopathies

A
  • difficult to control seizures
  • developmental delay
  • learning disabilities
  • many different causes (structural, chromosomal, monogenetic disorders)
110
Q

What is another name for Otahara syndrome

A

Early infantile developmental and epileptic encephalopathy

111
Q

When does Otahara present

A

first 3 months

112
Q

what seizure types are seen in otahara

A

multiple but often myoclonic jerks

113
Q

What developmental delay symptoms are associated with Otahara

A
  • poor tone
  • no visual interest
114
Q

What is the alternative name for West syndrome

A

infantile spasm

115
Q

What characteristic seizure is seen in West

A

infantile spasm
- transient increase in tone
- stiffening of arms and legs
- back arching
- jack knife/ flexor spasms

116
Q

What age is the onset of West

A

3-12 months

117
Q

How long do infantile spasm seizures last

A

brief (1-2 seconds)

118
Q

What causes West syndrome

A

chromosomal causes
or hypoxic brain injury

119
Q

What age is the onset of Lennox-Gastaut

A

1-2 years

120
Q

What type of seizures is seen in Lennox-Gastaut

A
  • atonic drop attacks
  • myoclonic jerks
  • generalized tonic colonic seizures
  • atypical - absence (with funny movement associated)
121
Q

what is an atypical seizure type in Lennox-Gastaut

A

absence with funny movements associated

122
Q

What epilepsy can be treated with cannabis oil legally

A

Lennox-Gastaut

123
Q

Explain initial development in landau kleffner

A

normal initial development

124
Q

what age does landau kleffner onset

A

2-3 years

125
Q

What are typical features of landau kleffner

A

loss of language/speech

126
Q

What is the main pathology in ESWS

A

cognitive decline

127
Q

Explain childhood benign partial epilepsies.

A
  • Development normal or near normal
  • onset 2-9 years
  • infrequent partial seizures (often only one)
  • abnormal EEG with normal brain imaging
  • seizures vary according to site.
128
Q

List examples of a childhood benign partial epilepsy

A
  1. Benign rolandic
  2. Panayiotopoulos
  3. Gastaut
129
Q

What is an alternative term for benign rolandic

A

childhood epilepsy with centro-temporal spikes

130
Q

what age is the onset for benign rolandic

A

2-9 years

131
Q

when do seizures typically onset in benign rolandic

A

with sleepw

132
Q

what are some typical features of the seizure

A
  • cry
  • facial droop
  • drooling
  • facial twitch
  • and spreads to generalized seizure
133
Q

Describe the EEG of Benign Rolandic

A

dramatic spikes over centro-temporal spikes

134
Q

Treatment for benign rolandic

A

usually self limiting and no anti seizure meds needed.

135
Q

What age is the onset for Panayiotopoulos syndrome

A

2-5 years

136
Q

Name some features of the seizure associated with Panayiotopoulos syndrome

A
  • ictal vomiting’s is characteristic
  • seizures are infrequent, prolonged and autonomic
  • usually only 1 or 2 seizures
137
Q

What ages is the onset of childhood absence epilepsy

A

5 or 6

PL6009 Neurology (4 decks)

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