F- Electrophysiological Examinations.ppt - Examinations EMG\/NCS (EEG Evoked potentials Event Related Potentials EMG\/NCS Electromyography Nerve

F- Electrophysiological Examinations.ppt - Examinations...

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Electrophysiological ExaminationsEMG/NCSElectroencephalography (EEG)Evoked potentials/ Event Related Potentials
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EMG/NCSElectromyographyNerve Conduction Studies
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.Electromyography (EMG)The pattern of electrical activity in muscle both at rest and during activityrecorded from a needle electrode inserted into the muscle.Evaluates individual motor units by inserting electrode into muscle nature and pattern of abnormalities relate to disorders at different levels of the motor unit.
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.1.Insertional activity: Brief burst of AP following insertion into resting muscle. 2. Spontaneous activity: Normal resting muscle has no spontaneous activity except end-plate noise.a. Configuration = duration, amplitude, number of phases1) Duration: Long or Short2) Amplitude: High3) Polyphasic:
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.b. Recruitment: Effort recruits additional motor units. c. Fibrillations: Spikes, positive sharp waves. d. Fasciculations: Discharge of an entire Motor Unit. e. Myotonia, myokymia: Complex repetitive discharges.
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.Nerve conduction studies (NCS)Measure electrical conduction along a nerve1. Motor NCS: Stimulate motor nerve and record muscle CMAP (compound muscle action potential), i.e., the sum of all axons directed to the muscle. a. Amplitude: Reflects the number of conductive muscle fibers (therefore axons)b. Distal latency: Time between stimulus and recording, depends on conduction of axons (not NMJ or muscle). c. Conduction velocity: Divides the distal latency between two locations along the same nerve by the distance between them
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.2. Sensory NCS: Stimulate a nerve and record its sensory nerve action potential (SNAP) from purely sensory portion of the nerve. E.g sural nerve is purely sensory.3. Late responses:a.F-wave: Motor stimulus travels both ortho- and antidromically. Antidromic stimulus reflected through neuron and back; creates small F-wave seen after first (M) wave. F-wave delayb. H-reflex: CMAP from stimulation of sensory nerve, via monosy naptic reflex arc.
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.4. Repetitive stimulation: Abnormalities are hallmark of NMJ dz.
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  • Fall '19
  • Evoked potential, Electroencephalography, Event-related potential, Motor unit

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