Basic measurements of NCVs

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Basic measurements of NCVs : 

Basic measurements of NCVs Ahmed Meraj Syed Clinical Neurophysiology The AKUH

Nerve Conduction Studies : 

Nerve Conduction Studies Definition Recording and analysis of the electric waveforms of biologic origin elicited in response to electric or physiologic stimuli.

Cont; : 

Cont; Recording technique of NCS. Motor nerve conduction studies. Sensory nerve conduction studies. Factors affecting the nerve. conduction studies.

MNCS : 

MNCS Motor nerve is recorded by stimulating nerve and recording from the Belly of the muscle supplied by that nerve. Active recording electrode G1 Motor point or the belly of the muscle under investigation.

Cont; : 

Cont; Reference recording electrode G2 Placed over the tendon, relatively inactive area. Ground electrode In between recording and stimulating electrode.

Motor nerve conduction studies : 

Motor nerve conduction studies Cathod Placed on the nerve facing towards active recording electrode. Anode Placed 3-5 cm proximal to cathod. Stimulus intensity capable of producing an observable response is called threshold stimulation.

Cont; : 

Cont; Supra-maximal stimulation Maximal stimuli, which do not produce any further increase in the response and approximately 20-30% above maximal intensity is supra-maximal threshold.

Parameters measured in MNC : 

Parameters measured in MNC Onset latency The initial base line departure from the base line. In case of positive deflection, onset latency should be taken the initial base line departure in positive direction. Amplitude Base line to peak.

Cont; : 

Cont; Nerve conduction velocity For two side stimulation: CV = distance/ time (proximal latency – onset latency) For one side stimulation: CV = distance / proximal latency onset latency – 1.1 ms

Motor nerve conduction studies : 

Motor nerve conduction studies

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Duration The amount of the time between the CMAP onset latency and insertion with base line. Area It is the area under the negative spike of the CMAP. Duration

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Area Duration

SENSORY NERVE CONDUCTION STUDIES : 

SENSORY NERVE CONDUCTION STUDIES Active recording electrode Distal segment of the nerve. Reference recording electrode 3-5 cm distal to active recording electrode Ground electrode In between active recording electrode and cathod of stimulating electrode

SNCS : 

SNCS Cathod Placed on the nerve facing towards active recording electrode. Anode Placed 3-5 cm distal to cathod. Stimulus intensity Capable of producing an observable response is called threshold stimulation.

Cont; : 

Cont; Supra-maximal stimulation: Maximal stimuli, which do not produce any further increase in the response and approximately 20-30% above maximal intensity is supra-maximal threshold.

Parameters measured in SNC : 

Parameters measured in SNC latency measurement Peak latency amplitude Base line to peak Conduction velocity CV = distance between the stimulus and recording electrode / onset latency – 0.1ms (latency of activation)

Cont; : 

Cont; Compound muscle action potential (CMAP) Is the sum of all the action potentials occurring individually in the contracting muscle fibers.

Condition settings for NCS : 

Condition settings for NCS Sweep Time: 2-3ms /div Sensitivity: 500 ?V/div Stimulus duration: 0.2 ms Stimulus intensity: As required Stimulus type: Electric Stimulus mode: Single Stimulus rate: 1 Hz Filters: 2Hz – 10 KHz

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