MODULE II - GENERALITIES OF EEG Flashcards
(1) BRIEF HISTORY OF EEG (2) DEFINITION AND PURPOSE OF EEG (3) EEG GUIDELINES (4) MEASUREMENT AND NOMENCLATURE (5) PRINCIPLES OFF BRAIN ACTIVITY
Name 7 Common EEG artifacts
Muscle, Eye Movement, Electrode Popping/Movement, Environmental Noise, Electrode Impedance, Sweating/Salt Bridge, Electrical Interference
What are examples of muscle artifact?
eye blinks, eye movement, jaw clenching, facial movements, body twitches
True/False - muscle artifacts appears as low amplitude wave forms
False
How do muscle artifacts appear as waves?
As sharp, spiky waves that coincide with the timing of the muscle activity
What is the fix for muscle artifacts?
Try to calm the patient. Change the high frequency to check if the activity attenuates and make notations
What causes eye movement artifacts?
Eye movement artifacts are caused by rapid eye movements (saccades) or slow eye drifts during wakefulness or rapid eye movement (REM) sleep
How do eye movement artifacts appear as wave
They appear as slow waves or sharp deflections, often with horizontal or vertical orientation
Where are the eye movement artifacts commonly seen?
In the frontal or prefrontal electrode channels
When does electrode popping (or movement) occur?
When electrodes become loose resulting in intermittent loss of contact or displacement from the scalp
How do electrode popping or movement manifest as waves?
As abrupt signal loss or fluctuating amplitudes often affecting specific channels
What is the fix for electrode popping?
Rescrub or reapply electrode or replace if necessary
What are the external source types that cause environmental noise artifacts?
Electrical equipment, power lines, electromagnetic fields, or radio frequency
Describe the environmental noise artifacts
They can cause rhythmic or irregular disturbances across multiple channels and often appear as high frequency, low amplitude waves or irregular patterns unrelated to brain activity.
What is the fix for environmental noise artifacts?
Check connection of cables to amplifiers
What is electrode impedance?
Refers to the resistance encountered between the electrode and the scalp which affects the quality of the recorded signals
What is the fix for electrode impedance issues?
Rescrub and reapply electrode - or replace if necessary
What is common mode rejection?
It refers to the ability of an EEG system to reject unwanted signals that are present in equal measure at multiple electrodes
How does the wave form look with sweating or salt bridge?
Inconsistent, erratic or attenuated signal
What is the fix for sweating (or salt bridge) issues?
Clean between electrodes with alcohol and or turn temperature in the room down
What is an electrical interference artifact.
a
Results from nearby electronic devices, power sources or faulty grounding
How do electronic interference artifacts appear?
As regular, rhythmic, or repetitIve patterns across multiple channels manifesting as sharp waves, spikes for oscillations.
What is the fix for electrical interference?
Let Pt and family know that personal devices may not be charging when in contact with patient or anything patient is sitting or lying on
What are phase reversals?
Pendaflection (deflection) peaks pointing in opposite directions in two channels within a chain. Used to localize normal and abnormal brain waves in bipolar montages that can be significant to a lesion, tumour, structural and/or chemical abnormalities
What is common mode rejection?
When the software rejects similar wave activity
Explain differential amplifier
Measures the voltage difference between two electrodes and amplifies the difference as shown in a montage tracing
What does electrodecriment mean
When the EEG channel is of an attenuated (decreased) amplitude
Explain posterior dominant rhythm (PDR)
Wave pattern seen in the occipital (posterior) region, especially when the person is awake, relaxed and has their eyes closed
Explain AP Gradient
When the anterior to posterior rhythm starts accentuating when you get more to the posterior; when the frequency of wave activity changes from front (anterior) to back (posterior); is prominent when awake and relaxed and is a normal EEG
What is burst suppression?
It is a pattern seen on an EEG characterized by alternating periods of high amplitude brain activity (bursts). This pattern often indicates a severely altered state of brain function (abnormal brain function)
Explain discontinuous pattern
brain wave activity that shows intermittent periods of electrical activity interspersed with periods of little or no activity
What is continuity?
where the waveforms are not interrupted by periods of flat or very attenuated activity
What is symmetry
Where both sides have the same or similar activity referring to amplitude and frequency
Describe the transverse montage and why they are used
This is referred to as the sleep montage and used to analyze brain activity of electrodes placed on the central plane
Describe the double banana montage and what they are useful for
The wave amplification that is representative of the electrodes placed on the parasagittal and temporal chains; when traced as electrodes they look like bananas; these are useful for identifying focal nor general activity
Describe differential amplification
Capability inherent in the software that amplifies the difference of multiple signals occurring between electrodes
inherent in EEG software systems is the ability suppress voltage patterns between electrode that are common in nature and to amplify/illustrate the resultant voltage difference
What’s the fix for electrical interference artifacts?
Advise patient that charging devices cannot be on bed or in contact with patient; find out from nurse if anything can be moved or unplugged where potentially causing the artifact
What does the EEG look like with electrical interference?
These appear as regular, rhythmic or respective patterns across multiple channels - and they show as sharp 3aves, spikes or oscillations unrelated to brain activity
Describe what happens with electrical interference artifacts
This results from nearby electronic devices (like smartphones when charging), power sources or faulty grounding. Electronic personal devices are fine but should not be used while charging when the EEG is running
What is the fix for sweating or salt bridge artifacts?
Clean between electrodes with alcohol and/or turn temperature down (make room cooler) in the room
Describe what the EEG looks like for sweating or salt bridge
Fluctuating signal amplitudes, increased noise, or unstable baselines; inconsistent, erratic or attenuated signal
Describe what happens with sweating or salt bridge artifacts
Sweat or too much electrode 10/20 paste on the scalp introduces noise or affects the electrical contact between the electrodes and the scalp
What is the fix for electrode impedance issues?
Rescrub, reapply or replace electrodes
Identify what electrode impedance issues look like on the EEG
Noise, signal distortion or baseline drift is observed; irregular or unstable signal patterns, noisy background or exaggerated baseline fluctuations
Describe what happens with electrode impedance artifacts
The resistance encountered between electrode and the scalp which affects the quality of the recorded signals
What do environmental noise artifacts look like on the EEG?
They appear as high frequency , low amplitude waves or irregular patterns unrelated to brain activity
Describe how electrode popping artifacts look like on the EEG
They manifest as fluctuating amplitudes often affecting specific channels - and appear as sudden changes in amplitude or loss of signal in affected channels
Describe what is happening with the environmental noise artifact
These artifacts originate from external sources such as electrical equipment, power lines, electromagnetic fields work radio frequency interference
What is the fix for the electrode popping issue?
Rescrub, reapply or replace the electrode if necessary
Describe what is happening with electrode popping or movement?
This happens when electrodes become loose, resulting in intermittent loss of contact or displacement from the scalp
How is the eye movement artifact issue fixed?
Making notations
Describe what eye movement artifacts look like on the EEG
They appear as slow waves or sharp deflections and are commonly seen in the frontal or prefrontal electrode channels
Describe what happens with eye movement artifacts
Eye movement are caused by rapid eye movements (saccades) or slow eye drifts during wakefulness or REM (rapid eye movement) sleep
How do you fix the issue of muscle artifacts?
Try to calm the patient, ask them to stop chewing, change the high frequency filter to check if the activity attenuates and make notations
What do muscle artifacts look like on the EEG?
High amplitude, sharp or spiky waves that coincide with the timing of the muscle activity and often affect multiple channels
Describe what happens in the patient with muscle artifacts?
muscle activity such as eye blinks, eye blinks, eye movements, jaw clenching, facial movements or body twitching
List 7 common EEG artifacts?
muscle artifacts, eye movement artifacts, electrode popping or movement artifacts, environmental noise, electrode impedance, sweating or salt bridge, electrical interference.
what are common mode signals and give example/s/
unwanted electrical interference picked up by the electrodes which are outside of the electrical activity of the brain [INSERT EXAMPLES]
What are artifacts
Extraneous signals that interfere with the EEG recording
What is common mode rejection (eg Salt Bridge)
The ability of an EEG system to reject signals that are common between paired electrodes in the montage
What is the ACNS guidelines for EEG about?
EEG Guidelines (from the American Clinical Neurophysiology Society)
pertains to the standards of practice for running a brain study with a report of the results obtained during EEG studies
