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Magnetic stimulation: C-8 root standardization based on arm length and arm position
1Department of Physical Medicine and Rehabilitation, William Beaumont Hospital, Royal Oak, Michigan.
Muscle & Nerve
|August 1, 1993
Summary
Magnetic stimulation (Magstim) of the C-8 nerve root requires standardized normal values. This study derived a formula accounting for arm length and position to improve C-8 root distal latency accuracy.
Area of Science:
- Neuroscience
- Clinical Electrophysiology
- Biomedical Engineering
Background:
- Existing normal values for C-8 root distal latencies (DL) using magnetic stimulation (Magstim) lack standardization for arm length and position.
- This oversight leads to an artificial widening of the normal range due to elevated standard deviation.
Purpose of the Study:
- To investigate the influence of arm length and position on C-8 root DL measurements.
- To develop a formula for more accurate determination of normal C-8 root DL by Magstim.
Main Methods:
- Magstim of the C-8 nerve root was performed on 30 healthy volunteers.
- Recorded variables included gender, hand temperature, age, arm length, and DL with the arm in resting and abducted positions.
- Statistical analysis was conducted to identify correlations between variables and DL.
Main Results:
- Mean DL was 13.3 +/- 1.1 ms, with minimal side-to-side variation (0.3 +/- 0.3 ms).
- The difference in DL between arm positions was negligible (0.2 +/- 0.3 ms).
- A direct correlation was found between arm length and DL.
Conclusions:
- Arm length is a significant factor influencing C-8 root DL measurements.
- A derived formula can improve the accuracy of normal DL distribution by accounting for arm length.
- This refinement enhances the clinical utility of Magstim for C-8 root assessment.