F3-Electrophysiological Examinations.ppt

EMG/NCS
Electroencephalography (EEG)
Evoked potentials/ Event Related Potentials

1. Electrophysiological
Examinations
A.EMG/NCS
B.Electroencephalography (EEG)
C.Evoked potentials/ Event Related
Potentials

2. A-EMG/NCS
Electromyography
Nerve Conduction Studies

3. .
Electromyography (EMG)
•The pattern of electrical activity in muscle
both at rest and during activity
–recorded from a needle electrode inserted
into the muscle.
–Evaluates individual motor units by
inserting electrode into muscle

4. .
1.Insertional activity: Brief burst of AP following
insertion into resting muscle.
2. Spontaneous activity: Normal resting muscle
has no spontaneous activity
a. Configuration - duration, amplitude, phases
b. Recruitment: Effort recruits additional motor
units.
c. Fibrillations: Spikes, positive sharp waves.
d. Fasciculations: Discharge of an entire Motor Unit.
e. Myotonia, myokymia: repetitive discharges.

5. .
Nerve conduction studies (NCS)
Measure electrical conduction along a nerve
1. Motor NCS: Stimulate motor nerve and
record muscle CMAP (compound muscle
action potential
a. Amplitude
b. Distal latency, Conduction velocity
2. Sensory NCS: Stimulate a nerve and record
its sensory nerve action potential (SNAP)
3. Late responses:
F-wave, H-reflex:
4. Repetitive stimulation: Abnormalities are
hallmark of NMJ disease- decrement of
CMAP-Myasthenia, Botulism

6. Medical Physiology Principles for Clinical Medicine.chw

7. B-Electroencephalography
(EEG)
..

8. EEG
A.What is EEG/Electroencephalography?"
B.What does the EEG tell us?
1.General health of the brain
2.Epilepsy

9. .
A. What is EEG/ Electroencephalography?"
•Measuring of brain waves
•The electrical activity of the brain is easily
recorded from electrodes placed on the
scalp.
•The potential difference between pairs of
electrodes on the scalp (bipolar derivation)
or between individual scalp electrodes and
a relatively inactive common reference
point (referential derivation)

10. EEG cont'd
Electrodes are put on the scalp
Measure the difference in potentials
between two points on the scalp.
oGenerally 21 electrodes and two
references on ears applied according to
proscribed system
oPen deflections represent differences in
electrical potentials between the two
electrodes involved in a given channel

11. EEG cont,d

12. From Wyllie
EEG cont,d

13. EEG cont,d

14. EEG cont,d
Types of waves
Alpha
Beta
Theta
Delta
Normal variations
Age,
Sleep,
Epileptiform
discharges
Sharp waves
Spikes
Spike-wave
complexes

15. Beta: >13 Hz;usually diffuse low
Voltage:increase with sedatives,
Light sleep
Alpha: 8-12 Hz; the posterior basic rhythm;
At age 3 reaching 8 Hz; at age 10, 10 Hz
Abnormal if amplitude asymm. >50%
Theta: 4-7 Hz; small amts. nl; increases
With drowsiness, hyperventilation
Delta: 0-3 Hz; posterior slow waves of youth
Nl; normal in sleep; focal delta=local abnl.
? At grey/white junction; post-ictal
The Frequencies

16. EEG cont,d
B. What does the EEG tell us?
1- General health of the brain
–“Vital signs”
–Encephalopathy
–Focal pathology
2- Epilepsy -are there seizure activity?
–Ictal activity
–Interictal activity
•With or without specific provocation

17. EEG cont,d
1. General health of the brain
1a. “Vital signs”
–Posterior basic rhythm
–Background fast activity
–Background slow activity
–Sleep activity
•Signs from various sleep stages
•Arousals from sleep
–Nearly all have age-appropriate norms

18. normal
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19. FP1-F7
F7-T3
T3-T5
T5-O1
FP2-F8
F8-T4
T4-T6
T6-O2
FP1-F3
F3-C3
C3-P3
P3-O1
FP2-F4
F4-C4
C4-P4
P4-O2
1 sec 100 µV
Rhythmic temporal theta bursts of drowsiness

20. Spindles

21. POSTS

22. EEG cont,d
1. Encephalopathy
–Metabolic (e.g., triphasic waves)
–Infectious (e.g., meningitis)
–Toxic (e.g., drug overdose)
–Anoxia/hypoxia
EEG: usually generalized findings (e.g.,
diffuse loss of normal background
activity)

23. EEG cont,d
2. Focal pathology – e.g.
–Tumor, Stroke, Bleeds, fluid collections,
certain infections,Brain injury,
degenerative disorders
EEG: focal slowing or loss of fast activity;
may see focal spikes or sharp waves
3. Epilepsy- seizure disorders
Ictal activity- Generalized vs. focal seizure
patterns
Interictal activity- Spikes, sharp waves,
hypsarrhythmia

25. EEG demonstrating a couplet of left anterior temporal spike-
and-slow waves.

27. POLYSPIKE WAVE

28. C- Evoked potentials/ Event
Related Potentials
.

29. .
1-Evoked potentials
•measured using electroencephalography
•Evoked potentials reflect the processing of
the physical stimulus
•Conducting many trials (100 or more) and
averaging the results together is
necessary

30. .
EPs reflect neurophysiological processing along the
pathways from sensation to primary sensory
cortex - visual, auditory, or somatosensory
•Brainstem auditory evoked responses (BAERs)
–Early waves after an auditory stimulus
–Reflect the intactness of the pathways they
traverse
•Visual Evoked Potentials(VEP)
–Potentials after an visual stimulus
–Shows the intactness of the visual pathway
•From retina to occipital cortex
•Somatosensory EP- the patient experiences an
electrical stimulation to an extremity.

33. .
2- Event-related brain potentials (Cognitive
Evoked Potentials)
Are caused by the "higher" processes, that
might involve memory, expectation,
attention, or changes in the mental state
A non-invasive method of measuring brain
activity during cognitive processing
ERPs reflect the information processing in
the cortex in real time
Are recorded from the human scalp
Are “Electrical Potentials associated with
specific sensory, perceptual, cognitive, or
motor events”

34. .
Single Trial: 100ms visual
stimulus
Average of 200 trials to
same stimulus
ERP derived from EEG

36. A wave showing several ERP components,
including the N100 and P300