Artifact Flashcards
Glossokinetic Potentials
Normal, Reproduced to verify (lalala). Mistaken for slow wave abnormal & FIRDA. Produced by the tongue just like eyes, except opposite polarity. Back of tongue is positive compared to the tip in frontal and temporal leads. Theta or Delta and about 75uV.
What are ‘O’ waves?
Eye blinks or EC in infants that produce large slow wave responses.
Breach Artifact
Localized, increased amplitude of high and low frequencies occurring over a skull defect such as that caused by craniotomy, burr hole, trauma, etc. Beta may appear quite sharp and mistaken for epileptiform activity.
IV Drip Artifact
Rare. Looks like small sharp or spike and wave but precise timing like EKG and other artifacts of the like.
Intraventricular Artifact
High amplitude sharps or spikes that resemble EKG in timing, but are usually generalized and can make a record unreadable.
Feeding Pump Artifact
Circular occipital/temporal slow waves.
Walking Artifact
Looks like the opposite of biphasic or triphasic waves. Occurs in the occipito-tempro-posterio head regions.
Back Patting Artifact
Looks like electrode artifact. Rhythmic and sharp.
Pulse Artifact
Slow waves that follow EKG and is commonly seen at the fontanelle in neonates.
What can disrupt an EEG and affect study interpretation?
Artifacts
Artifacts can significantly disturb background activity.
What are Glossokinetic potentials or Hypoglossal artifacts caused by?
Movement of the tongue
These artifacts appear as slower, diffuse delta frequency activity.
How do Hypoglossal artifacts appear in an EEG?
Slower, diffuse delta frequency activity that is mostly synchronized and symmetrical with frontal dominance
They can enhance artifacts from eye movement or tongue movement.
What references may enhance artifacts from eye movement in EEG?
Chin, nose, or cheek references
These references can be associated with glossokinetic potentials.
What should be done with any observed artifact by the technologist?
Eliminated and/or replicated to prove its source
This helps in verifying the artifact.
How can the hypoglossal artifact be reproduced for verification?
By asking the patient to move their tongue or say ‘la la la’ or ‘lilt’
This helps differentiate it from frontal delta activity.
What happens to the electrical field when the tongue moves?
The change spreads to the scalp and is recorded by scalp electrodes
This is how the artifact is captured in the EEG.
What type of waveform can be produced by tongue movement in an EEG?
Single or rhythmic diffuse delta waves
The delta waves are prominent in the frontal region.
What may the delta appearing waves in an EEG look like?
Vertical eye movement artifact
This similarity can complicate interpretation.
Does the appearance of the Glossokinetic artifact vary between individuals?
Yes, the same tongue movement can produce large artifacts in some but not in others
Individual differences affect artifact visibility.
What can help differentiate hypoglossal artifacts from infraorbital artifacts?
The use of eye electrodes
Eye electrodes provide additional data for differentiation.
What is an electroretinogram artifact?
Seen during photic in the prefrontal leads (fp1/fp2) at high sensitivities for recording suspected electrocerebral inactivity. Artifact matches the frequency of photic.
Hold an opaque card over the eye to block photic light flash from reaching the retina.
What is a tremor artifact?
Rhythmic theta activity with myogenic potentials superimposed occurring at 4-7 Hz as the head or body tremors.
Put leads on extremities with tremors.
How do you monitor eye movement artifact?
Place additional electrodes infraorbitally or on the outer canthus of each eye and reference eye leads to ear.
How are 60Hz artifacts caused by electromagnetic effects?
Caused by electrical appliances or equipment.
Eliminate by determining cause of 60Hz and remove, put on battery power, or turn off.
What is the best way to monitor EKG artifact?
No way to eliminate; use 2 EKG leads (1 on upper right, 1 on upper left or on each wrist).
What causes glossokinetic artifact?
Artifact from tongue movement; tip of tongue is negative, root of tongue is positive.
Monitor by placing one electrode above the mouth and one below, ask patient to say ‘lilt’ or ‘lala’ to produce artifact.
What does pacemaker artifact look like?
Seen as a fast spike, which is the electrical stimulus delivered to the heart by an internal cardiac pacemaker.
Seen in channel monitoring EKG.
What is corneoretinal potential?
The cornea is (+) relative to the retina which is (-).
How do you monitor respiration artifact?
Fairly rhythmic slow activity synchronous with movement related to respiration.
Try to eliminate by repositioning the patient’s head.
How are 60Hz artifacts caused by electrostatic effects?
Caused by capacitance between 60Hz conductor.
Eliminate by determining cause and removing.
What is an electrode malfunction artifact?
Caused by an electrically unstable electrode of high impedance, known as ‘electrode pop.’
Eliminate by repairing electrode.
What does pulse artifact look like?
Periodic slow wave that has a slight delay but is time locked to the EKG waveform.
Monitor by recording EKG.
What is muscle artifact?
A very short duration potential that usually occurs in clusters or periodic runs.
To eliminate, ask the patient to relax the jaw.
What causes skin potentials artifact?
Areas of skin with many sweat glands are electrically negative; sweating can cause slow waves, most likely slow rolling delta waves.
Eliminate by wiping head with alcohol, cooling head, etc., and place 2 leads on hand (one on palm, one on dorsum).
What does intravenous (IV) drip artifact resemble?
Resembles EKG artifact.
Monitor by typing ‘X’ on EEG; eliminate by asking the nurse to turn off use or use battery power.
What are artifacts in the context of ECG and EEG recordings?
Recorded activities that originate somewhere other than the area of interest.
When recording an ECG, what is considered an artifact?
Anything recorded which does not originate in the heart.
In EEG recordings, what is classified as an artifact?
Anything recorded that is not cerebral in origin.
Is it possible for an EEG to be free of artifacts?
No, no EEG is free of artifacts.
What is an essential role of an expert in EEG?
Identifying artifacts correctly.
What are the major roles of an EEG technologist?
Identifying, documenting, and eliminating artifacts.
What can high-amplitude artifacts do to EEG activity?
Totally obscure EEG activity.
What is the effect of low amplitude artifacts on EEG activity?
They can subtly minimize or distort the cerebral activity.
Are all artifacts considered useless?
No, some artifacts provide crucial information for interpretation.
What is an integral part of skilled EEG interpretation?
Correlating artifacts with an ongoing EEG.
List the three groups by which artifacts can be categorized.
- Artifacts of physiological origins
- Artifacts associated with body or head movements
- Artifacts of nonphysiological (electrical) origins
What are physiological artifacts?
Physiological artifacts originate from the body itself.
Are physiological artifacts avoidable in EEG recordings?
No, the contamination of physiological artifacts is inevitable in any EEG.
How can physiological artifacts be modified or minimized?
By appropriate technical adjustments.
What are myogenic artifacts?
EMG artifacts arise from nearby muscles introducing ‘muscle artifacts’ mostly in the temporal and frontal electrodes.
Which patients are more likely to exhibit tonic muscle artifacts?
Elderly or uncooperative patients.
What is the frequency of EMG artifacts?
The frequency of EMG artifacts varies from patient to patient.
How can excessive EMG artifacts be minimized?
By lowering the high filter from 70 to 35 or 15 Hz.
What caution should be exercised when lowering the high filter for EMG artifacts?
Filtered muscle can resemble beta activity.
What can filtered muscle artifacts mimic?
Filtered muscle artifacts could mimic ‘spike’ discharges.
Where are EMG artifacts usually prominent?
In the ear or mastoid electrodes due to proximity to the temporalis muscles.
What can be done if the contamination of artifacts is excessive?
The reference can be switched to the vertex (Cz) where muscle artifacts are minimal.
What is often contaminated by EMG artifact?
EEG
EMG artifact can interfere with the accuracy of EEG readings.
How can EMG artifact contamination be minimized?
By using Cz reference
Using a specific electrode reference can help reduce the impact of muscle artifacts.
What do tonic muscle artifacts indicate?
The patient’s level of consciousness
Tonic muscle artifacts are useful in assessing whether a patient is awake or drowsy.
What happens to tonic muscle artifacts during drowsiness?
They usually diminish
Diminished tonic muscle artifacts can help indicate changes in consciousness.
What EEG pattern may indicate REM sleep?
An awake or drowsy-appearing EEG with absence of tonic muscle artifact
This combination raises the possibility of the patient being in REM sleep.
What causes the lateral rectus muscle twitch artifact?
Activation of cranial nerve VI
This twitch artifact is recorded at F7 or F8 electrodes during scanning eye movements.
How does a muscle artifact typically appear?
As a single muscle ‘twitch’
Muscle artifacts can be mistaken for other electrical discharges.
What distinguishes muscle spikes from epileptiform spikes?
Narrow and closed field distribution or random and scattered occurrence
These characteristics help differentiate muscle spikes from those of cerebral origin.
What happens to muscle spikes during sleep?
They tend to have a longer duration
Muscle spikes during sleep can resemble cerebral spikes, complicating interpretation.
What can repetitive muscle twitch artifacts resemble?
Repetitive spikes or ictal discharges
These artifacts may obscure background activity in EEG readings.
What can the eyeball be regarded as?
A dipole with positivity toward the cornea and negativity toward the retina
What happens to the EEG when the eyeballs are in a fixed position?
There is no potential change
What does a moving dipole generated by eyeball movement produce?
A large and slow AC potential
Where is the large and slow AC potential detected?
By electrodes near the eyeballs
What occurs when the eyes close or blink?
Both eyeballs move in a conjugate upward direction (the Bell phenomena)
Where is the positive deflection maximal when the eyes close or blink?
At Fp1 and Fp2
What happens to the potential at Fp1 and Fp2 when the eyes open?
A downward eye movement causes a negative potential
Where are horizontal eye movements reflected maximally?
At F7 and F8
What is the polarity at F7 and F8 when looking to the left?
Positivity at F7 and negativity at F8
What is the polarity at F7 and F8 when looking to the right?
Negativity at F7 and positivity at F8
What can mimic focal delta activity in patients?
Asymmetric eye movement artifacts
This can occur when the patient has a prosthetic eye or diseased eyeball.
What can result in asymmetric eye movement artifacts despite normal eye movement?
A severely diseased eyeball with a loss of normal ocular potential
This condition can still show normal and conjugate eye movement.
What is a potential cause of asymmetric eye movement artifacts?
Asymmetrical electrode placement between homologous electrodes
Who should notice asymmetries in eye movement potentials?
An astute technologist
Fill in the blank: Asymmetric eye movement artifacts can occur when there is _______ between homologous electrodes.
asymmetrical electrode placement
What do slow-drifting (horizontal) eye movements signify?
The patient is becoming drowsy and should not be disturbed if a sleep recording is desired
This indicates a state of drowsiness during sleep studies
What artifact is often accompanied by rapid horizontal eye movements?
Lateral rectus muscle twitch artifact
This artifact can be detected at F7 or F8 electrodes
What does a lateral rectus muscle twitch cause?
The eye to move toward the contracted muscle
This results in a positive polarity deflection in the recorded data
When is the twitch artifact best seen?
In REM sleep or in a patient who has nystagmus
The twitch artifact is a key feature in specific sleep stages
Fill in the blank: Rapid horizontal eye movements are often accompanied by _______.
lateral rectus muscle twitch artifact
What artifact resembles frontal delta activity or eye movement artifacts?
Glossokinetic potential associated with tongue movement
This potential is linked to the electrical charges of the tongue during movement.
How is the tongue electrically charged?
Negativity at the tip and positivity at the root
This electrical configuration contributes to the glossokinetic potential.
What happens when the tongue moves towards the roof of the pharynx?
The change in the electrical field spreads to the scalp, causing delta waves
These waves are especially prominent in the frontal region.
What type of waves are caused by the glossokinetic potential?
Single or rhythmic diffuse delta waves
These waves resemble vertical eye movement artifacts.
How can the glossokinetic potential be reproduced?
By asking the patient to say words including an ‘L’ sound, such as ‘lilt’
This method can elicit the potential for observation.
True or False: The contamination of the glossokinetic potential to the scalp electrodes is consistent across all individuals.
False
The contamination varies considerably from one person to another.
What does the glossokinetic potential resemble?
Vertical eye movement artifact
It mimics the electrical activity seen with eye movements.
What is the role of the infraorbital electrode in EEG differentiation?
It helps differentiate between glossokinetic potential and frontal delta activity
Both potentials show an inphase deflection between Fp and IO electrodes.
What is the key difference in distribution between vertical eye movements and glossokinetic potentials?
Glossokinetic potentials have a wider distribution than vertical eye movements
This differentiation can occur without eye monitor electrodes.
True or False: Both glossokinetic potential and frontal delta activity show an inphase deflection between Fp and IO electrodes.
True
This indicates a similarity in their electrical activity patterns.
What is an Electroretinogram (ERG)?
A response to photic stimulation recorded from a contact lens electrode placed over the eyeball.
Where else can ERG be recorded besides the contact lens electrode?
From Fp1 and Fp2 electrodes.
What does the ERG response consist of?
A small sharp and wave complex.
What is the relationship between ERG response and flicker frequency?
The response is time locked to the flicker frequency.
Why is ERG often seen in electrocerebral silence (ECS) recordings?
Due to high-amplification recording with absence of interfering EEG activity and remaining function of the retina.
How can normal physiological responses from the retina be distinguished from nonphysiological artifact?
By delivering high-frequency flashes (>30 Hz).
What happens to the ERG when high-frequency flashes are delivered?
The ERG cannot react to high-frequency flashes.
True or False: The ERG can be affected by high-frequency flashes.
False.
What type of muscle artifacts does swallowing produce?
Short crescendo–decrescendo bursts of muscle artifacts
Often accompanied by slow activity of glossokinetic origin.
What types of movements may cause rhythmic delta activity?
Chewing and sucking movements
Can be monitored by electrodes placed over the jaw or near the lip.
What artifacts can sobbing, sniffles, or hiccups introduce?
Artifacts resembling spike wave or other paroxysmal discharges
These artifacts may present problems in EEG interpretation.
Why must each sob or hiccup be annotated by the technologist?
To distinguish them from other EEG discharges
Important for accurate EEG interpretation.
Can a baby continue to sob during stage II sleep?
Yes
This highlights the need for careful annotation during EEG monitoring.
What are ‘sweat artifacts’?
‘Sweat artifacts’ are generated from sweat gland potentials that are electrically negative.
What type of frequency characterizes the potential of sweat artifacts?
The potential is a DC-like slow frequency.
How do sweat artifacts manifest in recordings?
They cause slow-drifting deflections.
What can minimize sweat artifacts?
Using a shorter time constant setting.
What is a consequence of using a shorter time constant or higher low-filter setting?
It will also attenuate slow waves of cerebral origin.
Where do sweat artifacts occur?
They occur randomly at any electrode without an organized potential field distribution.
How can sweat artifacts be differentiated from delta activity?
They lack an organized potential field distribution, aiding in their differentiation from delta activity of cerebral origin.
inhalation and/or exhalation
usually involving electrodes on which the patient is
What type of artifacts may patients with tremors introduce on electrodes?
Rhythmic artifacts on one or more electrodes
In which condition may patients produce 2- to 4-Hz rhythmic artifacts?
Parkinson’s disease
What types of artifacts may accompany rhythmic artifacts in patients with Parkinson’s disease?
Myogenic (EMG) artifacts
How can the movements of patients with tremors be monitored?
By placing a pair of electrodes over the involved muscles and recording EMG activity
What device can be used to register very quick movement in patients with tremors?
Accelerometer
Fill in the blank: Patients with tremors may introduce _______ artifacts on electrodes.
rhythmic
