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Neurology Flashcards

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1
Q

What is EEG?

A

electrical activity of the brain measured on the scalp surface

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2
Q

Pyramidal neuron

A

Span entire cortex
Radial
Lined up in same direction - vertically oriented
Create circuit in layer around cell as different parts of the cells have different electric potentials

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3
Q

EPSP

A

Excitatory postsynaptic potential
movement of ions, positive change, more electrically excitable
big enough change generates an AP
generated at same time

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4
Q

IPSP

A

Inhibitory postsynaptic potential
movement of ions, negative change, less electrically excitable
big enough change generates an AP
generated at same time

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5
Q

Current source

A

Current (positive ions) flows out of cells

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6
Q

Current sink

A

Current (positive ions) flows into cells
Co-ordinated EPSP generates sink

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7
Q

Dipole

A
  • One surface negative
  • Corresponding area of surface positive
  • Depends on orientation of the EEG source
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8
Q

Name the 4 lobes of the brain and their function

A

Frontal: higher executive function, decision making
Parietal: processing sensory info
Temporal: speech, language, learning, memory
Occipital: processing visual info

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9
Q

Cerebral cortex

A

Most EEG gerentating regions at surface (scalp EEG)
Grey matter at top
Large surface area: many bulges (gyri) and deep furrows (sulci) - allows for more neurons

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10
Q

Sulci & gyri

A

sulci = deep groove
gyri = bumps and ridges in cerebral cortex

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11
Q

How many layers does the cerebral cortex have?

A

6

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12
Q

What type of neurons generate EEG?

A

Pyramidal neurons

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13
Q

What is the primary cause of epileptiform spikes?

A

paraoxysmal depolarising shifts

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14
Q

Paraoxysmal depolarising shifts

A

Sustained period of neuronal depolarisation

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15
Q

What type of cells and in what region of the brain generate EEG rhythms?

A

Pacemaker cells in thalmus
(pacemaker cells drive the reactions

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16
Q

Why is it that EPSPs/IPSPs can be measured in EEG but APs can’t?

A

EPSPs/IPSPs: last 5-20ms
APs: last 1ms

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17
Q

How do Pyramidal Neurons and EPSPs relate to EEG generation?

A

inside of cell more positive,
outside more negative,
loop of current flowing,
surface negative potential can be measured,
flow of EPSPs all together create a large enough current to be measured on the scalp

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18
Q

Cl- & K+ are EPSPs or IPSPs?

A

IPSPs

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19
Q

Ca2+ & Na2+ are EPSPs or IPSPs?

A

EPSPs

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20
Q

Name the 6 layers of cerebral cortex

A

Layer I: Molecular layer
Layer II: External granular layer
Layer III: Extrenal pyramidal layer
Layer IV: Internal granular layer
Layer V: Ganglionic layer
Layer VI: Multiform cell layer
(surface in)

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21
Q

Depolarisation induced by neurotransmitter - EPSP or IPSP?

A

EPSP

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22
Q

Hyperpolarisation - EPSP or IPSP?

A

IPSP

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23
Q

Electrode types for EEG (3) + examples of each

A

EEG Surface Electrodes: Ag/AgCl, Au, Pt

Supplementary electrodes: ECG, EOG, EMG (deltoid)

Special EEG Electrodes: subdermal needle, nasopharyngeal

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24
Q

Most common EEG electrode

A

Ag/AgCl surface electrode

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25
Types of EEG surface electrodes (3)
Disposable Reusable Caps
26
Electrode application for EEG
Adhesives: - conductive paste for routine EEG - Collodion longterm EEG studies Skin Prep (NuPrep): lower electrode impedance
27
Electrode placement for EEG (4)
10-20 system (10%/20% of total size of head) -measurement: use china marker & disposable tape -anatomical landmarks: nasion/inion &preauricular points -electrode nomenclature: letter & number
28
Anatomical landmarks for 10-20 system (2)
nasion/inion (anterior - posterior) preauricular points (transverse)
29
Electrode nomenclature: letter system (5)
F = frontal C = centre P = parietal O = occipital T = temporal
30
Electrode nomenclature: number system (3)
Right side: even number Left side: odd number Centre: z
31
10-20 system: views (3)
Saggital plane (side view) Horizontal plane (top view) Coronal plane (front view)
32
Ideal electrode impedance on EEG
<5kohm
33
Min electrode impedance on EEG
<10kohm
34
What does a higher amplitude of electrical impedance indicate?
More artefact
35
What is the purpose of electrical impedance?
Measure integrity of each electrode
36
Amplifier (EEG)
capture signal, amplify, and convert to digital for computer processing purposes
37
Display (EEG) (2)
Amplitude (vertical scale) - sensitivity control, commonly set at 7-10microV, high amplitude activity = decreased sensitivity Time (horizontal scale) - sweep speed (30mm/s), 15s/page of EEG
38
Filters (EEG) (4)
Purpose: attenuate frequency, enhance region of interest Types: Low Pass Filter (0.5Hz) High Pass Filter (70Hz) Notch Filter (50Hz)
39
What type of high frequency signal would be filtered out in a low pass filter?
Sweat, respiration
40
What type of low frequency signal would be filtered out in a high pass filter?
Muscle movement, electrical noise
41
What type of signal would be filtered out in a notch filter?
AC Mains Supply
42
Time constant (EEG)
time (s) it takes for a signal to decay to 37% of it's initial amplitude when a square wave is applied to the input terminals
43
Aliasing (2)
Occurs when system measured at inefficient sampling rate Creates frequency misinterpretation of recorded signal
44
Montage
Arrangement of electrodes used in recording
45
Location of maximal potential / region of interest found most easily on EEG by...
phase reversal
46
Bipolar montage
Serial pairs of electrodes compared with each other to record difference between each pair
47
Bipolar montage: Bipolar longitudinal
aka Double Banana useful to view symmetry between left and right hemispheres can determine potential gradient in anterior-posterior direction
48
Bipolar montage: Transverse
side by side useful to determine if activity has temporal / parasagittal dominance
49
What type of montage is useful in sleep studies & why?
Transverse Centre line active in sleep Vertex waves seen
50
Referential montage
multiple scalp electrodes (input 1) connected to common reference (input 2)
51
Common referential montages
To Mastoid (A1/A2) To Vertex (Cz) External point (neck to cervical) Avg reference
52
Assumption of referential montage
Reference electrode assumed electrically inactive
53
Activations in EEG (3)
Hyperventilation Photicstimulation Sleep/sleep deprivation
54
Hyperventilation EEG Activation
Rate of 3-4 breaths / 10s 3 mins Children use a pinwheel
55
Expected EEG for Hyperventilation EEG Activation (2)
Bilaterally diffuse synchronous slow wave bursts Theta > Delta "HV buildup"
56
Contraindications for Hyperventilation EEG Activation
Recent stroke, TIA, pregnant, >65y/o, recent cardiac/resp issues
57
Photicstimulation EEG Activation
Performed to elicit a photoparoxysmal response (PPR) for diagnosis of photosensitive epilepsy - Strobe Light - Distance 30cm from patient - Repetitive flashing light – 10 seconds on/off - Frequency 2Hz-20Hz, 50Hz, 30Hz, 25Hz - Eye opening and eye closure for each flash frequency
58
Sleep/sleep deprivation EEG Activation
Increases the diagnostic yield of EEG Enhances generalised discharges > focal discharges Unclear if sleep deprivation or sleep itself is the true activator
59
EEG artefact
Anything recorded no cerebral in origin
60
EEG artefact examples (2)
Physiological/Biological origins Nonphysiological (electrical) origin
61
EEG Waveform (4)
Frequency & Amplitude Location: which region of the brain is affected? Occipital? Posterior vs Anterior? Symmetry Responsiveness: change with a given action? e.g. eye opening
62
EEG Frequency (4)
Alpha 8-13Hz eyes closed, awake Beta >13Hz awake Theta 4-8Hz Delta 0.5-1Hz
63
EEG Amplitude
Find which channel amplitude is highest in - referential montage
64
EEG Location
Phase reversal & max amplitude What electrode is this happening in?(find common)
65
Phase reversal
Find pair of electrodes (2 channels) where EEG signal changes direction Phase reversal in a bipolar chain OR Find which channels amplitude is highest in Phase reversal at B Posterior lead: posterior dominant
66
Symmetry in EEG (2)
Synchronous & Symmetrical (same in both hemispheres)
67
Normal adult EEG (5)
Alpha Rhythm Posterior dominant Blocked eye opening Mu Rhythm Lambda waves
68
Lamda Waves
awake state (seen on eye opening) small triangular 'sail-like' shapes small 'evoked potentials'
69
Mu Rhythm
common in children and YAs f ~9Hz central regions - unilateral blocked by movement of contralateral limb
70
Sleep EEG - stages (5)
Drowsiness N1 N2 N3 REM
71
Sleep EEG - characteristics (6)
Drowsiness N1/stage 1: alpha loss, vertex sharp waves (CZ) N2/stage 2: vertex sharp waves, K spindles N3: spindles & delta Stage 4: deltas REM: alpha, visible eye movements
72
Delta wave progression through sleep stages
Increases as sleep stages increase
73
What sleep stage is not reached in EEG lab?
REM
74
Vertex sharp waves
Located to vertex Cz-High amplitude Broad-V-shaped Striking features of light sleep
75
K complexes
Sharp wave+Slow wave+ spindle Stage 2/N2 sleep Maximal in vertex/mid-line
76
Coma
Increased theta activity Increased delta activity Supression burst Isoelectric Abnormal theta, delta, discontinuity
77
Pathological features in coma (5)
- Periodic lateralized epileptiform discharges (PLEDS) - Triphasic complexes - Asymmetry - Dysynchrony - Extreme delta brush
78
PLEDs (4)
Periodic lateralized epileptiform discharges - Represent acute focal neurological disturbance - Stroke - Focal Infection-Herpes Simplex - Focal inflammation-Auto-immune encephalitis
79
Triphasic Complexes (4)
- Characteristic of a wide range of encephalopathy - Hypoxia - NH3 (Liver) - Uraemia (Kidney)
80
Extreme Delta Brush
Delta Super-imposed higher frequency activity Associated with anti-NMDA encephalitis
81
EEG in children (4)
EEG changes as children get older (up to 20 y/o) Decreasing EEG activity as age increases Delta initially decreases in first 3 yrs Some theta Dominant rhythm increases as age increases
82
EEG in children - specific to children (2)
Alpha sub-harmonic Posterior slow waves of youth
83

Physiology (8 decks)

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