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VEPs 1

Visual evoked potentials 1

QuestionAnswer
Two types of VEP flash, pattern reversal
Type of VEP used to evaluate retinal dysfunction Flash
Lesions in this region cause loss or slowing of the evoked potential generated by stimulating the affected eye optic nerve
Lesions at or near this region are not purely monocular and may affect incongruous portions of the visual fields of both eyes, creating confusing VEPs that are challenging to localize optic chiasm
Lesions of this region produce abnormalities of the VEP elicited from one visual hemifield optic tract
Lesions of this region of the brain produce abnormalities in the VEP, but these changes are complex; the VEP typically is not used to diagnose abnormalities in this region occipital cortex
When performing VEPs, separate normal controls are needed for subjects up to age __ and over age __ 5, 60
Visual acuity for VEPs should be better than 20/__ for squares of 1 degree or less 200
Visual acuity of 20/200 should allow patients to see VEP patterns of __ degree or less 1
The rate of pattern reversal for VEPs is __ - __ per second 1, 2
Check size should be __ - ___ ' for full field stimulation from the central retina and __ - __ ' for hemifield stimulation of the peripheral retina 28, 31, 50, 90
The field side should be over __ degrees for full field stimulation and __ - __ degrees for hemifield stimulation 8, 10, 16
The three channels used for a standard full field stimulation (without ERG) RO-MF, MO-MF, LO-MF
Midline occipital electrode is __ cm above the inion 5
In VEPs, __ refers to the midline occipital electrode MO
In VEPs, __ refers to the left occipital electrode LO
In VEPs, __ refers to the left occipital electrode RO
In VEPs, __ refers to the left temporal electrode LT
In VEPs, __ refers to the right temporal electrode RT
In VEPs, LO is __ cm lateral to MO 5
In VEPs, RO is __ cm lateral to MO 5
In VEPs, LT is __ cm lateral to MO 10
In VEPs, RT is __ cm lateral to MO 10
In VEPs, midline frontal is represented by __ MF
In VEPs, MF is __ cm behind the inion 12
The ground electrode for VEPs is usually placed at the __ of the head vertex
Channel one for standard VEPs with full field stimulation RO-MF
Channel two for standard VEPs with full field stimulation MO-MF
Channel three for standard VEPs with full field stimulation LO-MF
If channel four is used with VEPs with full field stimulation, it usually represents __ with __ and __ electrodes ERG, infraorbital, lateral orbital
For right hemifield VEPs, typical channel one RO-MF
For right hemifield VEPs, typical channel two MO-MF
For right hemifield VEPs, typical channel three LO-MF
For right hemifield VEPs, typical channel four LT-MF
For left hemifield VEPs, typical channel one RT-MF
For left hemifield VEPs, typical channel two RO-MF
For left hemifield VEPs, typical channel three MO-MF
For left hemifield VEPs, typical channel four LO-MF
Typical low frequency filter for VEP is from __ - __Hz 0.2, 1
Typical high frequency filter for VEP is from __ - __ Hz 200, 300
The typical number of responses averaged for a full field VEP is between __ and __ 100, 200
The typical number of responses averaged for a hemifield VEP is __ 200
The sweep length for most VEPs is __ msec, but can be up to __ msec for infants and greatly delayed VEPs 250, 500
The typical full field normal VEP peaks N75, P100, N145
The typical ipsilateral hemifield VEP peaks N75, P100, N145
The typical contralateral hemifield VEP peaks N75, P105, P135
The three criteria for abnormal full field VEPs absence of peaks, abnormal long latency p100, abnormal long p100 interocular latency
The criteria for abnormal hemifield VEPs Absence of any peaks ipsilateral and contralateral to the stimulated hemifield
Higher checkerboard reversal rates > 4 / second lead to this change in the test Increased latency
Slower checkerboard reversal rates < 2 / second led to this change in the test Slower testing
The two important components to checks: __ between checks and __ of check borders contrast, sharpness
At low contrast levels between checks, there is a __ (increase/decrease) of the VEP latency and a __(increase/decrease) in amplitude increase, decrease
Contrast is a function of __ luminance
Contrast = ____ / ___ Lmax - Lmin / Lmax + Lmin
Bandwidth for VEPs is usually __ - __ Hz 1, 100
Visual field size is < than __ degrees with a check size of __ minutes 10, 30
The P100 is an __ (upgoing / downgoing) wave upgoing
The __ wave of the VEP is thought to be generated by projections of the optic radiations to the visual cortex with contribution of the visual cortex itself P100
This wave __ of the VEP may be due to the lateral geniculate activity N75
This wave __ of the VEP may be due to activity of visual association cortex N145
THe normal latency of the P100 is between __ and __ seconds 90, 110
The P100 is also known as __ P1
The N145 is also known as __ N2
The type of VEP used in young children flash VEP
The VEP reaches adult values by the end of age __ for large checks (50-60') and by age __ for small checks (12-15') 1, 5
Amplitude of VEPs increases until age ~ __ 40
P100 latency remains stable during adulthood but increases after age __ 60
__ (women/men) have shorter P100s women
With loss of visual acuity below 20/200, the VEP latency is __ (increased/decreased) and the amplitude is __ (increased/decreased) increased, decreased
The maximal latency of the P100 with pattern reversal stimulation in msec 117
The maximal latency of the P100 with flash stimulation in msec 132
The maximal interocular latency difference the P100 with pattern reversal stimulation in msec 6
The maximal interocular latency difference of the P100 with flash stimulationstimulation in msec 6
The maximal interocular amplitude difference of the P100 with pattern reversal stimulation in microvolts 5.5
Created by: schmittse