EEG Boards Flashcards
What additional electrodes could be placed to help decipher between artifact and cortical activity in this sample?
EOG electrodes
Brain Abcess
Focal polymorphic delta activity.
Which of the following extra electrodes might best demonstrate the EEG activity associated with focal motor twitching of the right corner of the mouth?
C5
An abbreviated 10-20 placement, respiration, ECG and EOG monitors should be used when recording…
Neonates
Sphenoidal electrodes are used to record activity from the …
Anterior temporal lobes
Why is it not best practice to allow an outpatient to sleep throughout the entire EEG recording?
Unable to evaluate the patient’s background rhythm.
Cortical EEG recordings can be obscured in patients who are tense and anxious due to …
Myogenic Artifact
What type of monitoring would be useful in an EEG patient experiencing syncope?
ECG
What additional monitoring should be done in a middle age patient who repeatedly alerts from sleep during the EEG?
Respiration
Which of the following is important for the technologist to document in order to aid in interpretations?
The patient was awake and alert during the recording
A slow wave focus is best seen with…
LF 0.3 Hz, paper speed 15 mm/sec
A waveform of 0.5 Hz can be best enhanced with a filter of
LF 0.3 Hz
Which combination of settings will help enhance a low voltage slow wave that is being masked by muscle activity?
Sensitivity 5; LF .3; HF 35
Referential recording is most appropriate for measuring
Voltage
Fourteen and six Hz positive spike are best recorded with
The contralateral ear reference
Which of the following is the most appropriate instrumentation setting change that should be made in order to enhance cortical slowing?
Change the LFF from 1 Hz to .1 Hz
When attempting to minimize relentless muscle artifact on a recording, the technologist should be aware that lowering the high filter could cause the artifact to resemble:
beta activity
When using the average reference, if a spike-and-wave focus appears at C3, the abnormality would be best enhanced by…
Excluding C3 and surrounding electrodes from reference.
To enhance the background alpha and beta asymmetry in an EEG record showing moderately high voltage delta activity, the technologist should use a…
shorter time constant and increased sensitivity
Of the following, the BEST choice of reference to be used when recording in suspected temporal lobe epilepsy is:
CZ
Which of the following sites is most commonly used for the ground electrode in EEG?
FPZ
Gradual changes in amplitude, frequency, or spatial distribution of rhythms is know as:
Evolution
What happens when a 60 cycle sine wave is sampled at 100 hertz?
Aliasing
If the Low Frequency Filter is changed from 1 Hz to 5 Hz, how will a 2 Hz slow wave be affected?
It will be significantly attenuated
Which of the following is not useful in digital EEG recordings?
bio calibration
Digital EEG montages are reformatted by using
System reference
EEG amplifiers work on the principle of
both differential and amplification
Which of the following instruments magnifies the common-mode voltage difference between two inputs?
Differential Amplifier
The 60 Hz notch filter will have the greatest effect on a waveform having a duration of
16 msec
Clipping of the waveforms occurs when:
the signal is outside the range of the digitizer
According to the Guidelines, how many bits of resolution is required?
16
A LFF setting of 5 Hz will attenuate a 5 Hz wave by approximately:
0.3
The sharpness of the frequency response curve is determined by the filter
rolloff
Time Constant
Low Frequency Filter (LFF)
The ability of an amplifier to reject like signals.
Common mode rejection
Doubling the inter-electrode distances will have what effect on the waveforms?
Increase amplitude
Which of the following is not useful in digital EEG recordings?
bio calibration
Vertical Resolution
Amplitude
Which of the following converts an analog signal into a series of digital binary numbers?
A/D converter
Digital EEG montages are reformatted by using
system reference
Frequency
Influenced by sampling rate and measured in hertz
For low frequency filters (LFFs), the corresponding time constants for LFF cutoff frequency of 3 Hz would be
0.05 sec
Which of the following is the most appropriate sampling rate that should be used for a HFF setting of 70 Hz., according to ACNS 2016 Guidelines?
210 p sec
The amount by which the differential amplifier increases the magnitude of the input signal is its
Sensitivity
Which of the following is the most appropriate sampling rate that should be used for a HFF setting of 70 Hz., according to Nyquist theory?
140 p/sec
Which of the following instruments magnifies the common-mode boltage difference between two inputs?
Differential Amplifier
In a differential amplifier, if input 1 received a voltage of +50 microvolts and input 2 a voltage of -100 microvolts, the output voltage and deflection would be approximately
150 downward
High data sampling rates in a digital EEG machine create
Smooth, connected lines
Which mathematically converts the time function into a sine wave of different frequencies?
Fast Fourier Transform
Long Time Constant
LFF of .1 Hz
Term used to describe the way a signal is sampled at intervals and assined a numberic value:
Sampling Rate
Which of the following principles best applies to the EEG amplifiers?
Common mode rejection
Common Mode Rejection
Differential amplifier
Wigh high frequency filtering, muscle artifact may become distorted and look like
beta activity
If the Low Frequency Filter is changed from 1 Hz to 5 Hz, how will a 2 Hz slow wave be affected?
It will be significantly attenuated
What percentage of actual amplitude will be visible of 15 Hz wave when using a HFF setting of 15 Hz?
0.7
Which of the following settings is most sensitive?
2 uV/mm
Clipping of the waveforms occurs when:
The signal is outside the range of the digitizer
Which of the following time constants would best display delta activity?
1.0 second
Which of the following most closely relates to the ratio of an amplifiers output to input signal?
System Gain
Increasing the number of seconds displayed on the monitor
does not change spike amplitude or duration
A 0.5 Hz wave is enhanced without affecting a spike by using
LF 0.3 Hz
Gradual changes in amplitude, frequency, or spatial distribution of rhythms is know as:
Evolution
The waveforms contain frequencies as high as 100 hertz. What is the Nyquist sampling rate?
> 200 samples/second
Signals common to both inputs of a differential amplifier with like frequency, amplitude and phase are:
Canceled
Input impedance shoud be
very high
What happens when a 60 cycle sine wave is sampled at 100 hertz?
Aliasing
EEG amplifiers work on the principles of
both differential and amplification
2016 ACNS guidelines recommends a CMRR of at least:
90 dB
What is the specification of the minimum sampling rate used, in relation to the highest frequency signal recorded?
Nyquist theory
A time constant of 0.5 sec
High Pass Filter 0.3 Hz
All of the following fators favor cancellation of signals in the two inputs of an amplifier, except
unequal impedances in the inputs
Frequency Response Curve
Filters
Low sampling rate may cause fast frequencies to appear slower.
Aliasing
A 0.3 Hz wave would be attenuated by what percentage with a 0.3 Hz filter?
0.3
The 60 Hz notch filter will have thegreatest effect on a waveform having a duration of
16msec
Undersampling
Aliasing
A device that alters the amplitude of specific frequencies of a signal:
Filter
Which of the following insturmentation setting change may result in the elimination of cortical spikes?
Change the HFF from 70 Hz to 15 Hz
Voltage Resolution
Analog-to-digital converter
2016 ACNS Guidelines recommends a minimum horizontal resolution of:
16 bits
Which of the following medications would be expected to increase beta frequency activity?
Xanax (alprazolam)
What is the most common cause of genralized beta?
medications
Which of the following drugs exhibits the most observable effect on the electroencephalogram?
Benzodiazepines
A 25 year old female admitted with new onset psychosis was given 3 mg of Ativan prior to EEG recording. How would this medication affect the EEG?
Increased beta activity
Excessive beta frequency activity may be the result of which of the following?
Drug effect
At the therapeutic levels, phenytoin causes what kind of EEG findings?
No Change
Phenobarbital
Beta Activity
ORDA is commonly seen in children with
Absence Seizures
Bilateral anterior beta activity is MOST likely to occur with
Diazepam
Triphasic waves and/or periodic discharges can be present on an EEG due to the toxic effects of which of the following medication?
Lithium
What is the most prominent clinical feature of Dilantin toxicity?
Ataxia