SlideShare ist ein Scribd-Unternehmen logo
1 von 37
Downloaden Sie, um offline zu lesen
EVOKED
POTENTIALS DR. PREET MEHTA
INTRODUCTION
• Evoked potentials (EPs) are the electrical signals produced by the
nervous system in response to an external stimulus.
• The term EPs was originally used to refer to the responses to sensory
stimulation.
• Sensory EPs can be recorded following stimulation in any sensory
modality, but visual EPs (VEPs), auditory EPs (AEPs), and
somatosensory EPs (SEPs) are most often used for clinical diagnosis
and testing, intraoperative monitoring (IOM), and neurophysiological
research.
TYPES OF EVOKED POTENTIALS
• Brainstem auditory evoked potential
• Visual evoked potentials.
• Somatosensory evoked potentials
• Motor evoked potentials
• Cognitive evoked potentials
• Blink reflex
• Masseter reflex
BRAINSTEM AUDITORY EVOKED
POTENTIAL
• BAEP are the potentials recorded from the ear and vertex in
response to a brief auditory stimulation to assess the
conduction through auditory pathway up to mid-brain.
• Auditory brainstem response (ABR)
• Brainstem auditory evoked response (BAER)
• Brainstem evoked response audiometry (BERA)
Evoked potentials.pptx
METHOD
• Surface electrodes preferred- 1cm disc
electrode
• 2 channels : Ipsilateral (Ai) and
contralateral (Ac) referred to Cz.
• Channel 1: Ai-Cz
• Channel 2: Ac-Cz
• Ground: Fz
• 2000 trials are averaged.
Stimulation
• Square wave pulse 0.1
ms duration.
• Click rate 11-31 Hz
• Stimulus intensity : 70dB
• White noise of 30-40 dB
contralat.
Response
• 5-8 vertex positive peaks
• Trough and peaks denoted by roman
numbers.
Evoked potentials.pptx
1) Absolute latency and amplitude
2) Inter peak latencies
3) Amplitude ratio of wave V/I or
IV-V
4) Inter ear peak differences.
What we are
supposed to see
???
Clinical uses and positive findings
I-V IPL
- conduction from proximal
VIII nerve through pons to
midbrain.
- normal I-V IPL is 4.5 ms.
- Prolonged in Focal damage,
tumors, hypoxic brain
damage.
I-III IPL
• VIII nerve across subarachnoid space into the
core of lower pons.
• cerebellopontine angle tumors can cause a
delay at this juncture. Infarction can also
result in prolongation
• CP angle tumor (71% sen.
74%spe.)
• 1. Unrecordable BAEP
• 2. Only wave-I recordable
• 3. Prolongation of wave III and V
latency
• 4. Prolonged I-III and I-V IPL
• 5. Right to left asymmetry in wave
V latency >0.5 ms
Multiple Sclerosis
1. Amplitude reduction and absence of
wave V
2. Prolongation of III-V IPL
3. Prolongation of I-V IPL
4. Reduction of V/I ratio
5. Absence of wave III
• COMA
• Prognostic predictor
• Better predicting outcome
of severe head injury
compared to GCS , motor
signs and pupillary
reflexes.
VISUAL
EVOKED
POTENTIAL
• Visual evoked potentials
are electrical potential
differences recorded from
scalp in response to visual
stimuli.
• Visual evoked potentials
are very useful in
evaluating visual function.
METHOD
• PRETEST EVALUATION
• Explain the test to ensure full cooperation
• Avoid hair spray or oil.
• The usual glasses if any should be put on
• visual acuity, pupillary diameter, and field charts should be reviewed
before starting the test.
• Avoid any miotic or mydriatic drugs 12h before the test.
• Standard disc
electrodes are used.
• The recording
electrode at Oz
• The reference is
placed at the FpZ or
12cm above the
nasion.
• The ground electrode
Evoked potentials.pptx
• NORMAL VEP
• Represent a mass response
of cortical and possibly the
subcortical areas.
• Consist of a series of
waveform of opposite
polarity.
• The negative waveform is
denoted as N and positive
deflection as P, which is
followed by the approximate
latency in ms.
• Most common N70,
P100,N135
VEP ABNORMALITIES
• The unilateral VEP abnormality therefore, obtained by full field monocular
stimulation is likely to be due to prechiasmal lesion.
• The commonest cause of prolonged P100 latency is demyelination in the
optic pathways where the amplitude of P100 remains normal.
• DEMYELINATING
• plaque of 10 mm size would result in VEP delay of 25 ms.
(Multiple sclerosis)
• Optic Neuritis – monocular loss of vision – 20-50 age
• Nutritional and toxic neuropathy
• COMPRESSIVE :
• Extrinsic compression of anterior visual path ways results in loss
of amplitude, distortion of waveform, and prolongation of P100
latency.
Evoked potentials.pptx
SOMATOSENSORY EVOKED POTENTIALS
• SEPs are the electrical potentials generated mainly by the large
diameter sensory fibers in the peripheral and central portion of
the nervous system.
• The short latency potentials, which lie within 50 ms after the
stimulus are of clinical interest.
• The major advantage of SEP lies in evaluating the relatively long
sensory pathway from peripheral nerve to spinal cord and
cerebral cortex.
Evoked potentials.pptx
METHOD
• Patient supine
• Mild hypnotics may be used
• Sensory signs/symptoms and peripheral n. injury should
be obtained first.
• Procedure should be explained
• Recorded by stimulating any large nerve : Median and
posterior tibial
Median SsEP
• 1 cm disc electrodes
• recording electrodes - the
Erb's point (2-3 cm above
the mid clavicular point),
spinous process of c5 and 2
cm posterior to C3 or C4 .
• Left and right Erb's point
electrodes are des ignated as
EP1 and EP2, respectively,
• The spinal electrode is
designated as C5S or C5Sp.
• The scalp electrodes are
named as C2 C4
• The Fz, electrode is used as
• 200 micro.v square pulse
• Current – 5 to 15 mA
• Analysis time – 50-60ms
• Stimulation at wrist – cathode 2cm proximal to wrist crese.
• Rate of stimulation 3-8 Hz.s
• 1000-2000 averaged.
NORMAL MEDIAN SSEP
TIBIAL SSEP
• Posterior tibial nerve at the ankle.
• Recording electrodes at the popliteal fossa
(PF) 4-6 cm -between semitendinosus and
biceps femoris.
• Reference electrode is placed on the medial
surface of knee (K).
• Spinal recording electrodes - L1 referred to
third lumbar L3 and T 10 referred to T 12
• The scalp-recording electrode is placed 2
cm posterior to Cz referred to Fz
Evoked potentials.pptx
Evoked potentials.pptx
Evoked potentials.pptx
• Multiple sclerosis – silent lesisons can be detected.
• Trauma – SCI, root avulsion and plexopathies as SNAP are taken but
after 4-5 days while this can be taken in acute stage too.
• Vascular lesions - Hemorrhage.
• Cervical myelopathy
• Spinal cord tumor.
Evoked potentials.pptx
Evoked potentials.pptx
Evoked potentials.pptx
REFERENCES
• Clinical electrophysiology , K. Mishra 2nd edition
• ORIGINAL CONTRIBUTION soleus h-reflex modulation after motor
incomplete spinal cord injury: effects of body position and walking
speed, chetan P. Phadke et.Al , 2009
• ISCEV standard for clinical visual evoked potentials: (2016 update) J.
Vernon odom (2016)
• The electrophysiological assessment of visual function in Multiple
Sclerosis Joshua L. Barton et al. , 2019.
Evoked potentials.pptx

Weitere ähnliche Inhalte

Was ist angesagt?

Visual evoked potential and BAER
Visual evoked potential and BAERVisual evoked potential and BAER
Visual evoked potential and BAERManideep Malaka
 
Brainstem auditory evoked potentials (baep)
Brainstem auditory evoked potentials (baep)Brainstem auditory evoked potentials (baep)
Brainstem auditory evoked potentials (baep)NeurologyKota
 
Somato Sensory Evoked Potentials (SSEP) By: Murtaza Syed
Somato Sensory Evoked Potentials (SSEP) By: Murtaza SyedSomato Sensory Evoked Potentials (SSEP) By: Murtaza Syed
Somato Sensory Evoked Potentials (SSEP) By: Murtaza SyedMurtaza Syed
 
Vep and its practical importance
Vep and its practical importanceVep and its practical importance
Vep and its practical importancenikhilzandu
 
Upper Extremity Somatosensory Evoked Potential (Upper SSEP)
Upper Extremity Somatosensory Evoked Potential (Upper SSEP)Upper Extremity Somatosensory Evoked Potential (Upper SSEP)
Upper Extremity Somatosensory Evoked Potential (Upper SSEP)Anurag Tewari MD
 
Somatosensory evoked potential
Somatosensory evoked potentialSomatosensory evoked potential
Somatosensory evoked potentialdahmed hamed
 
Repetitive Nerve Stimulation
Repetitive Nerve Stimulation Repetitive Nerve Stimulation
Repetitive Nerve Stimulation Mohit Patel
 
Evoked potential - An overview
Evoked potential - An overviewEvoked potential - An overview
Evoked potential - An overviewAnbarasi rajkumar
 
Intraoperative Evoked Potential Monitoring
Intraoperative Evoked Potential MonitoringIntraoperative Evoked Potential Monitoring
Intraoperative Evoked Potential MonitoringPramod Krishnan
 
Visual evoked potential
Visual evoked potentialVisual evoked potential
Visual evoked potentialSSSIHMS-PG
 
Nerves conduction study
Nerves conduction studyNerves conduction study
Nerves conduction studyAhmad Shahir
 
Evoked potentials (1)
Evoked potentials (1)Evoked potentials (1)
Evoked potentials (1)Maithrikk
 
Lower Extremity Somatosensory Evoked Potentials (lower SSEP)
Lower Extremity Somatosensory Evoked Potentials (lower SSEP)Lower Extremity Somatosensory Evoked Potentials (lower SSEP)
Lower Extremity Somatosensory Evoked Potentials (lower SSEP)Anurag Tewari MD
 
Cranial Nerve Monitoring
Cranial Nerve MonitoringCranial Nerve Monitoring
Cranial Nerve Monitoringbowenseeg
 
Nerves conduction study
Nerves conduction study Nerves conduction study
Nerves conduction study Sachin Adukia
 

Was ist angesagt? (20)

Evoked potentials
Evoked potentialsEvoked potentials
Evoked potentials
 
Visual evoked potential and BAER
Visual evoked potential and BAERVisual evoked potential and BAER
Visual evoked potential and BAER
 
Brainstem auditory evoked potentials (baep)
Brainstem auditory evoked potentials (baep)Brainstem auditory evoked potentials (baep)
Brainstem auditory evoked potentials (baep)
 
Somato Sensory Evoked Potentials (SSEP) By: Murtaza Syed
Somato Sensory Evoked Potentials (SSEP) By: Murtaza SyedSomato Sensory Evoked Potentials (SSEP) By: Murtaza Syed
Somato Sensory Evoked Potentials (SSEP) By: Murtaza Syed
 
Vep and its practical importance
Vep and its practical importanceVep and its practical importance
Vep and its practical importance
 
Upper Extremity Somatosensory Evoked Potential (Upper SSEP)
Upper Extremity Somatosensory Evoked Potential (Upper SSEP)Upper Extremity Somatosensory Evoked Potential (Upper SSEP)
Upper Extremity Somatosensory Evoked Potential (Upper SSEP)
 
Somatosensory evoked potential
Somatosensory evoked potentialSomatosensory evoked potential
Somatosensory evoked potential
 
Repetitive Nerve Stimulation
Repetitive Nerve Stimulation Repetitive Nerve Stimulation
Repetitive Nerve Stimulation
 
repetitive nerve stimulation
repetitive nerve stimulationrepetitive nerve stimulation
repetitive nerve stimulation
 
Evoked potential - An overview
Evoked potential - An overviewEvoked potential - An overview
Evoked potential - An overview
 
Blink reflex
Blink reflex Blink reflex
Blink reflex
 
Intraoperative Evoked Potential Monitoring
Intraoperative Evoked Potential MonitoringIntraoperative Evoked Potential Monitoring
Intraoperative Evoked Potential Monitoring
 
EEG Generators
EEG GeneratorsEEG Generators
EEG Generators
 
Visual evoked potential
Visual evoked potentialVisual evoked potential
Visual evoked potential
 
Generator of vep
Generator of vepGenerator of vep
Generator of vep
 
Nerves conduction study
Nerves conduction studyNerves conduction study
Nerves conduction study
 
Evoked potentials (1)
Evoked potentials (1)Evoked potentials (1)
Evoked potentials (1)
 
Lower Extremity Somatosensory Evoked Potentials (lower SSEP)
Lower Extremity Somatosensory Evoked Potentials (lower SSEP)Lower Extremity Somatosensory Evoked Potentials (lower SSEP)
Lower Extremity Somatosensory Evoked Potentials (lower SSEP)
 
Cranial Nerve Monitoring
Cranial Nerve MonitoringCranial Nerve Monitoring
Cranial Nerve Monitoring
 
Nerves conduction study
Nerves conduction study Nerves conduction study
Nerves conduction study
 

Ähnlich wie Evoked potentials.pptx

Somatosensory and motor evoked potentials by neelothpala
Somatosensory and motor evoked potentials by neelothpalaSomatosensory and motor evoked potentials by neelothpala
Somatosensory and motor evoked potentials by neelothpalavrkv2007
 
Intraoperative Neurophysiological Monitoring Brain
Intraoperative Neurophysiological Monitoring BrainIntraoperative Neurophysiological Monitoring Brain
Intraoperative Neurophysiological Monitoring BrainFarrukh Javeed
 
Evoked Potential ppt.pptx
Evoked Potential ppt.pptxEvoked Potential ppt.pptx
Evoked Potential ppt.pptxAshik Dhakal
 
ABR master ppt.pptx
ABR master ppt.pptxABR master ppt.pptx
ABR master ppt.pptxEmanZayed17
 
Advances in neuro anesthesia monitoring
Advances in neuro anesthesia monitoringAdvances in neuro anesthesia monitoring
Advances in neuro anesthesia monitoringWesam Mousa
 
13- Electrodiagnosis in pedriatrics (DPT-9).pptx
13- Electrodiagnosis in pedriatrics (DPT-9).pptx13- Electrodiagnosis in pedriatrics (DPT-9).pptx
13- Electrodiagnosis in pedriatrics (DPT-9).pptxcutefairy5
 
Intra operative neurophysiological monitoring
Intra operative neurophysiological monitoringIntra operative neurophysiological monitoring
Intra operative neurophysiological monitoringKode Sashanka
 
Fundamentals of Nerve conduction studies and its Interpretations
Fundamentals of Nerve conduction studies and its InterpretationsFundamentals of Nerve conduction studies and its Interpretations
Fundamentals of Nerve conduction studies and its InterpretationsDr.suresh kumar MPT(Neuro)PhD
 
Visual evoked potential by arfa sultana
Visual evoked potential by arfa sultanaVisual evoked potential by arfa sultana
Visual evoked potential by arfa sultanavrkv2007
 
Electrocorticography
ElectrocorticographyElectrocorticography
ElectrocorticographyLalit Bansal
 
Neuromonitoring in anesthesia
Neuromonitoring in anesthesiaNeuromonitoring in anesthesia
Neuromonitoring in anesthesiaAntara Banerji
 
neuromonitoringinanesthesia-150217064704-conversion-gate02.pdf
neuromonitoringinanesthesia-150217064704-conversion-gate02.pdfneuromonitoringinanesthesia-150217064704-conversion-gate02.pdf
neuromonitoringinanesthesia-150217064704-conversion-gate02.pdfSaumya Singh
 
AUDITORY VISUAL EVOKED POTENTIAL.pptx
AUDITORY VISUAL EVOKED POTENTIAL.pptxAUDITORY VISUAL EVOKED POTENTIAL.pptx
AUDITORY VISUAL EVOKED POTENTIAL.pptxDr .Priyanka Verma
 
SUMSEM-2021-22_ECE6007_ETH_VL2021220701295_Reference_Material_I_04-07-2022_EE...
SUMSEM-2021-22_ECE6007_ETH_VL2021220701295_Reference_Material_I_04-07-2022_EE...SUMSEM-2021-22_ECE6007_ETH_VL2021220701295_Reference_Material_I_04-07-2022_EE...
SUMSEM-2021-22_ECE6007_ETH_VL2021220701295_Reference_Material_I_04-07-2022_EE...BharathSrinivasG
 
Visual Evoked Potentials
Visual Evoked PotentialsVisual Evoked Potentials
Visual Evoked PotentialsRahul Jain
 
Nerve conduction study
Nerve conduction studyNerve conduction study
Nerve conduction studyGaraka Rabel
 

Ähnlich wie Evoked potentials.pptx (20)

Somatosensory and motor evoked potentials by neelothpala
Somatosensory and motor evoked potentials by neelothpalaSomatosensory and motor evoked potentials by neelothpala
Somatosensory and motor evoked potentials by neelothpala
 
Intraoperative Neurophysiological Monitoring Brain
Intraoperative Neurophysiological Monitoring BrainIntraoperative Neurophysiological Monitoring Brain
Intraoperative Neurophysiological Monitoring Brain
 
Evoked Potential ppt.pptx
Evoked Potential ppt.pptxEvoked Potential ppt.pptx
Evoked Potential ppt.pptx
 
ABR master ppt.pptx
ABR master ppt.pptxABR master ppt.pptx
ABR master ppt.pptx
 
Advances in neuro anesthesia monitoring
Advances in neuro anesthesia monitoringAdvances in neuro anesthesia monitoring
Advances in neuro anesthesia monitoring
 
EEG INTERPRETATION
EEG INTERPRETATIONEEG INTERPRETATION
EEG INTERPRETATION
 
Chapter 7
Chapter 7Chapter 7
Chapter 7
 
13- Electrodiagnosis in pedriatrics (DPT-9).pptx
13- Electrodiagnosis in pedriatrics (DPT-9).pptx13- Electrodiagnosis in pedriatrics (DPT-9).pptx
13- Electrodiagnosis in pedriatrics (DPT-9).pptx
 
Intra operative neurophysiological monitoring
Intra operative neurophysiological monitoringIntra operative neurophysiological monitoring
Intra operative neurophysiological monitoring
 
Fundamentals of Nerve conduction studies and its Interpretations
Fundamentals of Nerve conduction studies and its InterpretationsFundamentals of Nerve conduction studies and its Interpretations
Fundamentals of Nerve conduction studies and its Interpretations
 
Visual evoked potential by arfa sultana
Visual evoked potential by arfa sultanaVisual evoked potential by arfa sultana
Visual evoked potential by arfa sultana
 
Evoked Potentials.pptx
Evoked Potentials.pptxEvoked Potentials.pptx
Evoked Potentials.pptx
 
Electrocorticography
ElectrocorticographyElectrocorticography
Electrocorticography
 
Neuromonitoring in anesthesia
Neuromonitoring in anesthesiaNeuromonitoring in anesthesia
Neuromonitoring in anesthesia
 
neuromonitoringinanesthesia-150217064704-conversion-gate02.pdf
neuromonitoringinanesthesia-150217064704-conversion-gate02.pdfneuromonitoringinanesthesia-150217064704-conversion-gate02.pdf
neuromonitoringinanesthesia-150217064704-conversion-gate02.pdf
 
Cranial nerves
Cranial nervesCranial nerves
Cranial nerves
 
AUDITORY VISUAL EVOKED POTENTIAL.pptx
AUDITORY VISUAL EVOKED POTENTIAL.pptxAUDITORY VISUAL EVOKED POTENTIAL.pptx
AUDITORY VISUAL EVOKED POTENTIAL.pptx
 
SUMSEM-2021-22_ECE6007_ETH_VL2021220701295_Reference_Material_I_04-07-2022_EE...
SUMSEM-2021-22_ECE6007_ETH_VL2021220701295_Reference_Material_I_04-07-2022_EE...SUMSEM-2021-22_ECE6007_ETH_VL2021220701295_Reference_Material_I_04-07-2022_EE...
SUMSEM-2021-22_ECE6007_ETH_VL2021220701295_Reference_Material_I_04-07-2022_EE...
 
Visual Evoked Potentials
Visual Evoked PotentialsVisual Evoked Potentials
Visual Evoked Potentials
 
Nerve conduction study
Nerve conduction studyNerve conduction study
Nerve conduction study
 

Kürzlich hochgeladen

FDMA FLAP - The first dorsal metacarpal artery (FDMA) flap is used mainly for...
FDMA FLAP - The first dorsal metacarpal artery (FDMA) flap is used mainly for...FDMA FLAP - The first dorsal metacarpal artery (FDMA) flap is used mainly for...
FDMA FLAP - The first dorsal metacarpal artery (FDMA) flap is used mainly for...Shubhanshu Gaurav
 
AORTIC DISSECTION and management of aortic dissection
AORTIC DISSECTION and management of aortic dissectionAORTIC DISSECTION and management of aortic dissection
AORTIC DISSECTION and management of aortic dissectiondrhanifmohdali
 
historyofpsychiatryinindia. Senthil Thirusangu
historyofpsychiatryinindia. Senthil Thirusanguhistoryofpsychiatryinindia. Senthil Thirusangu
historyofpsychiatryinindia. Senthil Thirusangu Medical University
 
"Radical excision of DIE in subferile women with deep infiltrating endometrio...
"Radical excision of DIE in subferile women with deep infiltrating endometrio..."Radical excision of DIE in subferile women with deep infiltrating endometrio...
"Radical excision of DIE in subferile women with deep infiltrating endometrio...Sujoy Dasgupta
 
blood bank management system project report
blood bank management system project reportblood bank management system project report
blood bank management system project reportNARMADAPETROLEUMGAS
 
Using Data Visualization in Public Health Communications
Using Data Visualization in Public Health CommunicationsUsing Data Visualization in Public Health Communications
Using Data Visualization in Public Health Communicationskatiequigley33
 
Neurological history taking (2024) .
Neurological  history  taking  (2024)  .Neurological  history  taking  (2024)  .
Neurological history taking (2024) .Mohamed Rizk Khodair
 
Breast cancer -ONCO IN MEDICAL AND SURGICAL NURSING.pptx
Breast cancer -ONCO IN MEDICAL AND SURGICAL NURSING.pptxBreast cancer -ONCO IN MEDICAL AND SURGICAL NURSING.pptx
Breast cancer -ONCO IN MEDICAL AND SURGICAL NURSING.pptxNaveenkumar267201
 
AUTONOMIC NERVOUS SYSTEM organization and functions
AUTONOMIC NERVOUS SYSTEM organization and functionsAUTONOMIC NERVOUS SYSTEM organization and functions
AUTONOMIC NERVOUS SYSTEM organization and functionsMedicoseAcademics
 
MedMatch: Your Health, Our Mission. Pitch deck.
MedMatch: Your Health, Our Mission. Pitch deck.MedMatch: Your Health, Our Mission. Pitch deck.
MedMatch: Your Health, Our Mission. Pitch deck.whalesdesign
 
CPR.nursingoutlook.pdf , Bsc nursing student
CPR.nursingoutlook.pdf , Bsc nursing studentCPR.nursingoutlook.pdf , Bsc nursing student
CPR.nursingoutlook.pdf , Bsc nursing studentsaileshpanda05
 
CONNECTIVE TISSUE (ANATOMY AND PHYSIOLOGY).pdf
CONNECTIVE TISSUE (ANATOMY AND PHYSIOLOGY).pdfCONNECTIVE TISSUE (ANATOMY AND PHYSIOLOGY).pdf
CONNECTIVE TISSUE (ANATOMY AND PHYSIOLOGY).pdfDolisha Warbi
 
Trustworthiness of AI based predictions Aachen 2024
Trustworthiness of AI based predictions Aachen 2024Trustworthiness of AI based predictions Aachen 2024
Trustworthiness of AI based predictions Aachen 2024EwoutSteyerberg1
 
Basic structure of hair and hair growth cycle.pptx
Basic structure of hair and hair growth cycle.pptxBasic structure of hair and hair growth cycle.pptx
Basic structure of hair and hair growth cycle.pptxkomalt2001
 
Female Reproductive Physiology Before Pregnancy
Female Reproductive Physiology Before PregnancyFemale Reproductive Physiology Before Pregnancy
Female Reproductive Physiology Before PregnancyMedicoseAcademics
 
Different drug regularity bodies in different countries.
Different drug regularity bodies in different countries.Different drug regularity bodies in different countries.
Different drug regularity bodies in different countries.kishan singh tomar
 
Red Blood Cells_anemia & polycythemia.pdf
Red Blood Cells_anemia & polycythemia.pdfRed Blood Cells_anemia & polycythemia.pdf
Red Blood Cells_anemia & polycythemia.pdfMedicoseAcademics
 
Physiology of Smooth Muscles -Mechanics of contraction and relaxation
Physiology of Smooth Muscles -Mechanics of contraction and relaxationPhysiology of Smooth Muscles -Mechanics of contraction and relaxation
Physiology of Smooth Muscles -Mechanics of contraction and relaxationMedicoseAcademics
 

Kürzlich hochgeladen (20)

FDMA FLAP - The first dorsal metacarpal artery (FDMA) flap is used mainly for...
FDMA FLAP - The first dorsal metacarpal artery (FDMA) flap is used mainly for...FDMA FLAP - The first dorsal metacarpal artery (FDMA) flap is used mainly for...
FDMA FLAP - The first dorsal metacarpal artery (FDMA) flap is used mainly for...
 
AORTIC DISSECTION and management of aortic dissection
AORTIC DISSECTION and management of aortic dissectionAORTIC DISSECTION and management of aortic dissection
AORTIC DISSECTION and management of aortic dissection
 
historyofpsychiatryinindia. Senthil Thirusangu
historyofpsychiatryinindia. Senthil Thirusanguhistoryofpsychiatryinindia. Senthil Thirusangu
historyofpsychiatryinindia. Senthil Thirusangu
 
"Radical excision of DIE in subferile women with deep infiltrating endometrio...
"Radical excision of DIE in subferile women with deep infiltrating endometrio..."Radical excision of DIE in subferile women with deep infiltrating endometrio...
"Radical excision of DIE in subferile women with deep infiltrating endometrio...
 
blood bank management system project report
blood bank management system project reportblood bank management system project report
blood bank management system project report
 
Immune labs basics part 1 acute phase reactants ESR, CRP Ahmed Yehia Ismaeel,...
Immune labs basics part 1 acute phase reactants ESR, CRP Ahmed Yehia Ismaeel,...Immune labs basics part 1 acute phase reactants ESR, CRP Ahmed Yehia Ismaeel,...
Immune labs basics part 1 acute phase reactants ESR, CRP Ahmed Yehia Ismaeel,...
 
Using Data Visualization in Public Health Communications
Using Data Visualization in Public Health CommunicationsUsing Data Visualization in Public Health Communications
Using Data Visualization in Public Health Communications
 
Neurological history taking (2024) .
Neurological  history  taking  (2024)  .Neurological  history  taking  (2024)  .
Neurological history taking (2024) .
 
Breast cancer -ONCO IN MEDICAL AND SURGICAL NURSING.pptx
Breast cancer -ONCO IN MEDICAL AND SURGICAL NURSING.pptxBreast cancer -ONCO IN MEDICAL AND SURGICAL NURSING.pptx
Breast cancer -ONCO IN MEDICAL AND SURGICAL NURSING.pptx
 
AUTONOMIC NERVOUS SYSTEM organization and functions
AUTONOMIC NERVOUS SYSTEM organization and functionsAUTONOMIC NERVOUS SYSTEM organization and functions
AUTONOMIC NERVOUS SYSTEM organization and functions
 
MedMatch: Your Health, Our Mission. Pitch deck.
MedMatch: Your Health, Our Mission. Pitch deck.MedMatch: Your Health, Our Mission. Pitch deck.
MedMatch: Your Health, Our Mission. Pitch deck.
 
CPR.nursingoutlook.pdf , Bsc nursing student
CPR.nursingoutlook.pdf , Bsc nursing studentCPR.nursingoutlook.pdf , Bsc nursing student
CPR.nursingoutlook.pdf , Bsc nursing student
 
How to master Steroid (glucocorticoids) prescription, different scenarios, ca...
How to master Steroid (glucocorticoids) prescription, different scenarios, ca...How to master Steroid (glucocorticoids) prescription, different scenarios, ca...
How to master Steroid (glucocorticoids) prescription, different scenarios, ca...
 
CONNECTIVE TISSUE (ANATOMY AND PHYSIOLOGY).pdf
CONNECTIVE TISSUE (ANATOMY AND PHYSIOLOGY).pdfCONNECTIVE TISSUE (ANATOMY AND PHYSIOLOGY).pdf
CONNECTIVE TISSUE (ANATOMY AND PHYSIOLOGY).pdf
 
Trustworthiness of AI based predictions Aachen 2024
Trustworthiness of AI based predictions Aachen 2024Trustworthiness of AI based predictions Aachen 2024
Trustworthiness of AI based predictions Aachen 2024
 
Basic structure of hair and hair growth cycle.pptx
Basic structure of hair and hair growth cycle.pptxBasic structure of hair and hair growth cycle.pptx
Basic structure of hair and hair growth cycle.pptx
 
Female Reproductive Physiology Before Pregnancy
Female Reproductive Physiology Before PregnancyFemale Reproductive Physiology Before Pregnancy
Female Reproductive Physiology Before Pregnancy
 
Different drug regularity bodies in different countries.
Different drug regularity bodies in different countries.Different drug regularity bodies in different countries.
Different drug regularity bodies in different countries.
 
Red Blood Cells_anemia & polycythemia.pdf
Red Blood Cells_anemia & polycythemia.pdfRed Blood Cells_anemia & polycythemia.pdf
Red Blood Cells_anemia & polycythemia.pdf
 
Physiology of Smooth Muscles -Mechanics of contraction and relaxation
Physiology of Smooth Muscles -Mechanics of contraction and relaxationPhysiology of Smooth Muscles -Mechanics of contraction and relaxation
Physiology of Smooth Muscles -Mechanics of contraction and relaxation
 

Evoked potentials.pptx

  • 2. INTRODUCTION • Evoked potentials (EPs) are the electrical signals produced by the nervous system in response to an external stimulus. • The term EPs was originally used to refer to the responses to sensory stimulation. • Sensory EPs can be recorded following stimulation in any sensory modality, but visual EPs (VEPs), auditory EPs (AEPs), and somatosensory EPs (SEPs) are most often used for clinical diagnosis and testing, intraoperative monitoring (IOM), and neurophysiological research.
  • 3. TYPES OF EVOKED POTENTIALS • Brainstem auditory evoked potential • Visual evoked potentials. • Somatosensory evoked potentials • Motor evoked potentials • Cognitive evoked potentials • Blink reflex • Masseter reflex
  • 5. • BAEP are the potentials recorded from the ear and vertex in response to a brief auditory stimulation to assess the conduction through auditory pathway up to mid-brain. • Auditory brainstem response (ABR) • Brainstem auditory evoked response (BAER) • Brainstem evoked response audiometry (BERA)
  • 7. METHOD • Surface electrodes preferred- 1cm disc electrode • 2 channels : Ipsilateral (Ai) and contralateral (Ac) referred to Cz. • Channel 1: Ai-Cz • Channel 2: Ac-Cz • Ground: Fz • 2000 trials are averaged.
  • 8. Stimulation • Square wave pulse 0.1 ms duration. • Click rate 11-31 Hz • Stimulus intensity : 70dB • White noise of 30-40 dB contralat. Response • 5-8 vertex positive peaks • Trough and peaks denoted by roman numbers.
  • 10. 1) Absolute latency and amplitude 2) Inter peak latencies 3) Amplitude ratio of wave V/I or IV-V 4) Inter ear peak differences. What we are supposed to see ???
  • 11. Clinical uses and positive findings I-V IPL - conduction from proximal VIII nerve through pons to midbrain. - normal I-V IPL is 4.5 ms. - Prolonged in Focal damage, tumors, hypoxic brain damage. I-III IPL • VIII nerve across subarachnoid space into the core of lower pons. • cerebellopontine angle tumors can cause a delay at this juncture. Infarction can also result in prolongation
  • 12. • CP angle tumor (71% sen. 74%spe.) • 1. Unrecordable BAEP • 2. Only wave-I recordable • 3. Prolongation of wave III and V latency • 4. Prolonged I-III and I-V IPL • 5. Right to left asymmetry in wave V latency >0.5 ms Multiple Sclerosis 1. Amplitude reduction and absence of wave V 2. Prolongation of III-V IPL 3. Prolongation of I-V IPL 4. Reduction of V/I ratio 5. Absence of wave III • COMA • Prognostic predictor • Better predicting outcome of severe head injury compared to GCS , motor signs and pupillary reflexes.
  • 14. • Visual evoked potentials are electrical potential differences recorded from scalp in response to visual stimuli. • Visual evoked potentials are very useful in evaluating visual function.
  • 15. METHOD • PRETEST EVALUATION • Explain the test to ensure full cooperation • Avoid hair spray or oil. • The usual glasses if any should be put on • visual acuity, pupillary diameter, and field charts should be reviewed before starting the test. • Avoid any miotic or mydriatic drugs 12h before the test.
  • 16. • Standard disc electrodes are used. • The recording electrode at Oz • The reference is placed at the FpZ or 12cm above the nasion. • The ground electrode
  • 18. • NORMAL VEP • Represent a mass response of cortical and possibly the subcortical areas. • Consist of a series of waveform of opposite polarity. • The negative waveform is denoted as N and positive deflection as P, which is followed by the approximate latency in ms. • Most common N70, P100,N135
  • 19. VEP ABNORMALITIES • The unilateral VEP abnormality therefore, obtained by full field monocular stimulation is likely to be due to prechiasmal lesion. • The commonest cause of prolonged P100 latency is demyelination in the optic pathways where the amplitude of P100 remains normal. • DEMYELINATING • plaque of 10 mm size would result in VEP delay of 25 ms. (Multiple sclerosis) • Optic Neuritis – monocular loss of vision – 20-50 age • Nutritional and toxic neuropathy • COMPRESSIVE : • Extrinsic compression of anterior visual path ways results in loss of amplitude, distortion of waveform, and prolongation of P100 latency.
  • 22. • SEPs are the electrical potentials generated mainly by the large diameter sensory fibers in the peripheral and central portion of the nervous system. • The short latency potentials, which lie within 50 ms after the stimulus are of clinical interest. • The major advantage of SEP lies in evaluating the relatively long sensory pathway from peripheral nerve to spinal cord and cerebral cortex.
  • 24. METHOD • Patient supine • Mild hypnotics may be used • Sensory signs/symptoms and peripheral n. injury should be obtained first. • Procedure should be explained • Recorded by stimulating any large nerve : Median and posterior tibial
  • 25. Median SsEP • 1 cm disc electrodes • recording electrodes - the Erb's point (2-3 cm above the mid clavicular point), spinous process of c5 and 2 cm posterior to C3 or C4 . • Left and right Erb's point electrodes are des ignated as EP1 and EP2, respectively, • The spinal electrode is designated as C5S or C5Sp. • The scalp electrodes are named as C2 C4 • The Fz, electrode is used as
  • 26. • 200 micro.v square pulse • Current – 5 to 15 mA • Analysis time – 50-60ms • Stimulation at wrist – cathode 2cm proximal to wrist crese. • Rate of stimulation 3-8 Hz.s • 1000-2000 averaged.
  • 28. TIBIAL SSEP • Posterior tibial nerve at the ankle. • Recording electrodes at the popliteal fossa (PF) 4-6 cm -between semitendinosus and biceps femoris. • Reference electrode is placed on the medial surface of knee (K). • Spinal recording electrodes - L1 referred to third lumbar L3 and T 10 referred to T 12 • The scalp-recording electrode is placed 2 cm posterior to Cz referred to Fz
  • 32. • Multiple sclerosis – silent lesisons can be detected. • Trauma – SCI, root avulsion and plexopathies as SNAP are taken but after 4-5 days while this can be taken in acute stage too. • Vascular lesions - Hemorrhage. • Cervical myelopathy • Spinal cord tumor.
  • 36. REFERENCES • Clinical electrophysiology , K. Mishra 2nd edition • ORIGINAL CONTRIBUTION soleus h-reflex modulation after motor incomplete spinal cord injury: effects of body position and walking speed, chetan P. Phadke et.Al , 2009 • ISCEV standard for clinical visual evoked potentials: (2016 update) J. Vernon odom (2016) • The electrophysiological assessment of visual function in Multiple Sclerosis Joshua L. Barton et al. , 2019.