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*For medical professionals only
Brain evoked potentials (EP) refer to the bioelectrical activity
produced by the central nervous system during the perception of internal or external stimuli.
Stimulation of the sensory organs or peripheral nerves provokes responses
in the corresponding cortical region as well as in the subcortical relay station.
Evoked potentials can assist doctors in diagnosing and differentiating related diseases, and play an important role
in clinical aspects.
Therefore, the author summarizes the specific classification of brain evoked potentials for the reference
of peers.
of the occipital cortex recorded by the scalp in response to visual stimuli.
VEP can be divided into mode light VEP, diffuse light VEP and other types of VEP according to the nature of the stimulus
.
The most commonly used in clinical practice are checkerboard flip VEP (PRVEP) and flash stimulation VEP (FVEP), the former waveform is simple and easy to analyze, high positive rate and good repeatability; The latter has large waveform and latency changes and low positivity rate, but is suitable for infantile coma patients and other people who
cannot cooperate.
Examinations are usually carried out in low-light conditions and should be preceded by a rough visual acuity measurement and correction
.
The stimulation form is generally a black-and-white checkerboard flip stimulation, the recording electrode is placed on 01, Oz and 02, and the reference electrode is usually placed on Cz
.
The frequency of stimulation is 1 time for 1 second, the analysis time is 500ms, and the number of superpositions is 100-200 times
.
At the time of the test, the subject was 75-10 em away from the stimulator, looked at the center point of the screen, tested with both eyes separately, and repeated the measurement twice on
each side.
PRVEP is a three-phase composite wave composed of NPN, named N75, P100, and N145
according to their average latency.
where P100 is considered to be an action potential
from the first viewport (17 regions) or central region.
P100 has the most stable incubation period and highest volatility, and is the only reliable component of
PRVEP.
The normal range of P100 latency is usually within
the mean of 3SD.
The criteria for anomalies are extended incubation period of P100> mean soil 3SD, latency difference between the two eyes > more than 10ms, amplitude < 3uV or waveform loss, etc<b21>.
Figure 1 (from literature [1]).
of auditory stimuli.
Alternating 1000-2000 clicks on one ear, the signal is recorded through the scalp electrode and amplified
by a computer.
5-7 waves
are recorded on the scalp within 10 ms after each stimulation.
According to the existing research results, the first 5 waves have stable incubation period, clear waveforms, and specific neurogenic sources in the brainstem auditory system, so they have definite clinical significance
.
In particular, the occurrence rate of I, III, and V waves is 100%, which is more valuable; The origin of the latter two waves is unknown
.
BAEP is particularly useful for examining cranial nerves (acoustic neuromas and other tumors of pontine cerebellar foot) and brainstem auditory pathways.
BAEP is abnormal in half of patients with confirmed multiple sclerosis (MS), and less than half of patients with a possible diagnosis of MS have abnormal BAEP testing (usually the reaction time between I and III waves and the prolonged reaction time between dish waves and V waves), patients may not even have clinical signs or symptoms
of brainstem damage.
It is also used to evaluate the hearing
of infants and children who have taken neurotoxic drugs for audio, and those with hysteria.
The criteria for BAEP anomalies are mainly based on waveform, wave absolute latency (PL), interpeak latency (IPL), binaural wave latency difference (IDL), and amplitude
。 There are a few points to note:
at different levels of the sensory transmission pathway and at the corresponding projection sites of the scalp.
Painless transcutaneous electrical stimulation acts on the median nerve, peroneal nerve, tibial nerve, and then records evoked potentials at Erb's point on the clavicle, the C2 spine, and the contralateral parietal cortex
, or in the lumbar and contralateral parietal cortex.
The main potentials recorded at the contralateral vertex of median nerve stimulation are P14, N20, P25, and N35; The main potentials recorded at the contralateral frontal point are P14, N18, and N30
.
The surrounding potentials are Erb's(N9) and C7
.
The criteria for abnormalities are the loss or low flatness of the waveform, the prolongation of the latency and interval of each wave, and the obvious increase of the latency difference between the two sides
.
Somatosensory evoked potential testing can confirm damage
to the somatosensory system.
The site
of damage is determined by recording impulse signals from peripheral nerves, spinal nerve roots, spinal cord, thin tract nuclei and wedge tract nuclei of the medulla oblongata, medial thalamus to the contralateral thalamus, and parietal cortical center, and averaging them by computer.
If the delay occurs at the point of receiving stimulation and Erb's point or between the lumbar vertebral vertebral tract, it indicates peripheral nerve damage; if it occurs at the Erb's point or between the lumbar spine and C2, it indicates that it is a lesion of the corresponding nerve root, and posterior spinal horn lesions are common; If the sensoricortical central pathway from the medial thalamus to the contralateral thalamus and parietal lobe is impaired, a wave delay
from the parietal cortex can be detected.
This examination is extremely helpful
in determining the damage to spinal nerve roots, posterior horns, brainstem and other structures in diseases such as Guillain-Barré syndrome, cervical and lumbar disc damage, multiple sclerosis, and cervical and lumbar joint stiffness.
Figure 2 (from literature [1]) Figure
3 (from literature [1]).
.
Generally, non-invasive electrical stimulation or magnetic circle stimulation is used, stimulating the scalp is equivalent to the motor projection area, which can induce the electrical activity response of the contralateral limb, and then increase the stimulation at the C7 spinous process and Erb's point, and also record the potential of the upper limb and hand, thereby measuring the central motor conduction time
from the motor cortex to the upper end of the cervical medulla.
The lower limb stimulation sites are the cerebral cortex motor area, T12 and L1 and the rougeal fossa, etc.
, and the recording sites are mostly breflexed hallux brevis and tibialis anterior muscle
.
It is clinically used for pathology of motor pathways and for detecting the rehabilitation status
of paralyzed limbs.
associated with cognitive processes.
ERP mainly studies the neuroelectrophysiological changes of the brain in cognitive processes, that is, explores the trajectory
of brain thinking.
P300 is the most widely used ERP, its stimulation forms include sound, vision, somatosensory, etc.
, and sound stimulation is more
used.
The P300 measurement mainly reflects the cognitive function of the cerebral cortex and is a sensitive indicator to
determine the degree of dementia and intelligence.
It also has a definite diagnostic value for schizophrenia and pseudodementia, and can also be used for polygraph and other research
.
Compared with EEG, the most characteristic feature of evoked potential testing is that it is not affected by
anesthesia, sedative drugs, or even damage to the cerebral hemispheres.
Therefore, it can be used to detect brain function
when an EEG is not available.
Although diagnostic criteria have been established, it is recommended that each laboratory establish its own criteria
.
Questionnaire survey
All kinds of brain evoked potentials, all dry goods!
Brain evoked potentials (EP) refer to the bioelectrical activity
produced by the central nervous system during the perception of internal or external stimuli.
Stimulation of the sensory organs or peripheral nerves provokes responses
in the corresponding cortical region as well as in the subcortical relay station.
Evoked potentials can assist doctors in diagnosing and differentiating related diseases, and play an important role
in clinical aspects.
Therefore, the author summarizes the specific classification of brain evoked potentials for the reference
of peers.
Visual evoked potentials
of the occipital cortex recorded by the scalp in response to visual stimuli.
VEP can be divided into mode light VEP, diffuse light VEP and other types of VEP according to the nature of the stimulus
.
The most commonly used in clinical practice are checkerboard flip VEP (PRVEP) and flash stimulation VEP (FVEP), the former waveform is simple and easy to analyze, high positive rate and good repeatability; The latter has large waveform and latency changes and low positivity rate, but is suitable for infantile coma patients and other people who
cannot cooperate.
Examinations are usually carried out in low-light conditions and should be preceded by a rough visual acuity measurement and correction
.
The stimulation form is generally a black-and-white checkerboard flip stimulation, the recording electrode is placed on 01, Oz and 02, and the reference electrode is usually placed on Cz
.
The frequency of stimulation is 1 time for 1 second, the analysis time is 500ms, and the number of superpositions is 100-200 times
.
At the time of the test, the subject was 75-10 em away from the stimulator, looked at the center point of the screen, tested with both eyes separately, and repeated the measurement twice on
each side.
PRVEP is a three-phase composite wave composed of NPN, named N75, P100, and N145
according to their average latency.
where P100 is considered to be an action potential
from the first viewport (17 regions) or central region.
P100 has the most stable incubation period and highest volatility, and is the only reliable component of
PRVEP.
The normal range of P100 latency is usually within
the mean of 3SD.
The criteria for anomalies are extended incubation period of P100> mean soil 3SD, latency difference between the two eyes > more than 10ms, amplitude < 3uV or waveform loss, etc<b21>.
Figure 1 (from literature [1]).
Brainstem auditory evoked potentials
of auditory stimuli.
Alternating 1000-2000 clicks on one ear, the signal is recorded through the scalp electrode and amplified
by a computer.
5-7 waves
are recorded on the scalp within 10 ms after each stimulation.
According to the existing research results, the first 5 waves have stable incubation period, clear waveforms, and specific neurogenic sources in the brainstem auditory system, so they have definite clinical significance
.
In particular, the occurrence rate of I, III, and V waves is 100%, which is more valuable; The origin of the latter two waves is unknown
.
BAEP is particularly useful for examining cranial nerves (acoustic neuromas and other tumors of pontine cerebellar foot) and brainstem auditory pathways.
BAEP is abnormal in half of patients with confirmed multiple sclerosis (MS), and less than half of patients with a possible diagnosis of MS have abnormal BAEP testing (usually the reaction time between I and III waves and the prolonged reaction time between dish waves and V waves), patients may not even have clinical signs or symptoms
of brainstem damage.
It is also used to evaluate the hearing
of infants and children who have taken neurotoxic drugs for audio, and those with hysteria.
The criteria for BAEP anomalies are mainly based on waveform, wave absolute latency (PL), interpeak latency (IPL), binaural wave latency difference (IDL), and amplitude
。 There are a few points to note:
1.
All BAEP waves (V waves) disappear.
Under the condition of excluding technical factors, and using too high stimulation intensity and more average times, it is still abnormal to fail to guide BAEP
.
2.
Under the premise of excluding technical factors, it is abnormal
that each wave after wave I or II cannot be induced.
3.
PL and IPL abnormalities
.
The mean plus 3 standard deviations is the upper limit of the normal value, under the premise of
normal hearing.
However, when the wave cannot be detected, the PL recorded by the external ear canal needle electrode or the eardrum / silver ball electrode can be used instead of the wave IPL to measure the IPL, which is completely consistent with
the IPL measurement with the PL of the wave as the standard.
4.
There was no significant difference in the incubation time (LD) between PL and IPL in the left and right ears between normal subjects.
For adults with normal hearing, the maximum ILD for an individual does not exceed 0
.
2ms
。 According to clinical experience, if the ILD value of PL and IPL exceeds 0
under the premise that the hearing threshold of both ears or pure tone hearing is normal.
4ms has clinical significance
.
5.
The relative value of BAEP amplitude, the amplitude (Amp) ratio of wave V or wave IV and V composite wave and wave I is more commonly used in clinical practice, and the ratio is > 1
in normal people.
Somatosensory evoked potentials
at different levels of the sensory transmission pathway and at the corresponding projection sites of the scalp.
Painless transcutaneous electrical stimulation acts on the median nerve, peroneal nerve, tibial nerve, and then records evoked potentials at Erb's point on the clavicle, the C2 spine, and the contralateral parietal cortex
, or in the lumbar and contralateral parietal cortex.
The main potentials recorded at the contralateral vertex of median nerve stimulation are P14, N20, P25, and N35; The main potentials recorded at the contralateral frontal point are P14, N18, and N30
.
The surrounding potentials are Erb's(N9) and C7
.
The criteria for abnormalities are the loss or low flatness of the waveform, the prolongation of the latency and interval of each wave, and the obvious increase of the latency difference between the two sides
.
Somatosensory evoked potential testing can confirm damage
to the somatosensory system.
The site
of damage is determined by recording impulse signals from peripheral nerves, spinal nerve roots, spinal cord, thin tract nuclei and wedge tract nuclei of the medulla oblongata, medial thalamus to the contralateral thalamus, and parietal cortical center, and averaging them by computer.
If the delay occurs at the point of receiving stimulation and Erb's point or between the lumbar vertebral vertebral tract, it indicates peripheral nerve damage; if it occurs at the Erb's point or between the lumbar spine and C2, it indicates that it is a lesion of the corresponding nerve root, and posterior spinal horn lesions are common; If the sensoricortical central pathway from the medial thalamus to the contralateral thalamus and parietal lobe is impaired, a wave delay
from the parietal cortex can be detected.
This examination is extremely helpful
in determining the damage to spinal nerve roots, posterior horns, brainstem and other structures in diseases such as Guillain-Barré syndrome, cervical and lumbar disc damage, multiple sclerosis, and cervical and lumbar joint stiffness.
Figure 2 (from literature [1]) Figure
3 (from literature [1]).
Motion evoked potentials
.
Generally, non-invasive electrical stimulation or magnetic circle stimulation is used, stimulating the scalp is equivalent to the motor projection area, which can induce the electrical activity response of the contralateral limb, and then increase the stimulation at the C7 spinous process and Erb's point, and also record the potential of the upper limb and hand, thereby measuring the central motor conduction time
from the motor cortex to the upper end of the cervical medulla.
The lower limb stimulation sites are the cerebral cortex motor area, T12 and L1 and the rougeal fossa, etc.
, and the recording sites are mostly breflexed hallux brevis and tibialis anterior muscle
.
It is clinically used for pathology of motor pathways and for detecting the rehabilitation status
of paralyzed limbs.
Event correlation potential
associated with cognitive processes.
ERP mainly studies the neuroelectrophysiological changes of the brain in cognitive processes, that is, explores the trajectory
of brain thinking.
P300 is the most widely used ERP, its stimulation forms include sound, vision, somatosensory, etc.
, and sound stimulation is more
used.
The P300 measurement mainly reflects the cognitive function of the cerebral cortex and is a sensitive indicator to
determine the degree of dementia and intelligence.
It also has a definite diagnostic value for schizophrenia and pseudodementia, and can also be used for polygraph and other research
.
Compared with EEG, the most characteristic feature of evoked potential testing is that it is not affected by
anesthesia, sedative drugs, or even damage to the cerebral hemispheres.
Therefore, it can be used to detect brain function
when an EEG is not available.
Although diagnostic criteria have been established, it is recommended that each laboratory establish its own criteria
.
Questionnaire survey
Stroke (commonly known as "stroke") has the characteristics of "four highs" with high morbidity, high disability rate, high mortality rate and high recurrence rate, acute onset, rapid progression and serious consequences, 1 in every 4 people in the world will have a stroke, 1 person will die of stroke every 6 seconds, and 1 person will be disabled due to stroke every 6 seconds, and the patient's family will suffer huge economic losses and physical and mental suffering
.
Reference sources:
[1] "Neurology" National Health and Family Planning Commission Standardized Training Planning Textbook for Resident Doctors.
[2] Jiang Tingting, Hu Yue
.
Research progress on
visual evoked potentials.
Electronic Journal
of Clinical Medical Literature.
2020，7（45）.
[3] Peng Chao, Tang Ying
.
New clinical progress in
somatosensory evoked potentials.
Chinese Journal of Clinicians (electronic version).
2013，7（22）.
