Nerve Conduction Studies – Questions for Exam Preparation-NCSExamPrepAnswers

NCSExamPrepAnswers

Pdf Summary

This document provides summaries of various questions and answers pertaining to electrophysiologic principles, primarily focusing on nerve conduction studies (NCS) and electromyography (EMG). Some key points from the summaries are as follows:<br /><br />1. **Wallerian Degeneration**: Post-crush injury, Wallerian degeneration hasn't occurred within the first 24 hours, leading to an expected normal motor response which completes in about 6-8 days. (Campbell WW et al.)<br /><br />2. **Nerve Conduction Velocities (NCV)**: Conduct faster at higher body temperatures, with proximal nerves being warmer due to their proximity to the body core. (Kimura J)<br /><br />3. **Stimulus Intensity for H-Waves**: H-waves require submaximal stimulus, and high currents can extinguish these waves. (Dumitru D)<br /><br />4. **Standard Setup Expectations**: A diphasic waveform with initial negativity is typical in normal recording setups. (Kimura J)<br /><br />5. **Sensory Studies**: Standard filter settings, with normal sural nerve amplitudes ranging from 10 to 50 µV. (Dumitru D)<br /><br />6. **Temperature Recommendations**: At least 30°C for lower limbs and 32°C for upper limbs, measured at distal portions during conduction studies. (Dumitru D)<br /><br />7. **Electrode Placement for SNAPs**: Active and reference electrodes must be appropriately distanced to allow accurate recording; improper placement reduces amplitudes and changes peak latency. (Dumitru D et al.)<br /><br />8. **Axon Reflexes**: These are distinctive late responses recorded during studies and indicate collateral sprouting; they differ from A waves and are best seen at moderate stimulus intensities. (Daube JR, Rubin DI)<br /><br />9. **Inter-relationship between Temperature and Amplitude**: Conduction velocity decreases with temperature drop, while amplitude increases, especially noted during NCSs. (Kimura J, Dumitru D)<br /><br />10. **Common Pitfalls**: Misplacing electrodes, excessive stimulus intensity, and limb temperature variations can significantly affect recording quality and accuracy of NCS and EMG results. (Dumitru D, Kimura J, Preston DC, Shapiro BE)<br /><br />These detailed explanations highlight various technical aspects and physiological principles critical for conducting and interpreting nerve conduction studies and electromyography effectively. The document emphasizes the importance of accurate electrode placement, maintaining appropriate body temperatures, and understanding the physiological responses under different test conditions to derive precise diagnostic conclusions in neurophysiological assessments.

Keywords

Wallerian Degeneration

Nerve Conduction Studies

ncs

Electromyography

Nerve Conduction Velocities

Stimulus Intensity

Temperature Recommendations

Electrode Placement

Axon Reflexes

Conduction Velocity

Recording Quality

nerve conduction studies

nerve conduction study

ncs

EMG