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Median and ulnar palm-wrist studies
H W Sander1, C Quinto, P B Saadeh
1Department of Neurology, Saint Vincents Hospital of New York, NY 10011, USA.
Summary
This study establishes normative electrodiagnostic values for carpal tunnel syndrome, recommending an abnormal palmar latency difference (PLD) cut-off of 0.5 ms to improve diagnostic accuracy and reduce false positives in nerve conduction studies.
Area of Science:
- Neurology
- Electrophysiology
Background:
- Carpal tunnel electrodiagnosis commonly uses median (MPW) and ulnar (UPW) palm-wrist mixed nerve conduction latency.
- Normative values for palmar latency difference (PLD) and UPW, and the utility of onset latency (OL) versus peak latency (PL) are debated.
Purpose of the Study:
- To determine normative values for MPW, UPW, and PLD in electrodiagnostic testing.
- To compare the clinical utility of onset latency (OL) and peak latency (PL) measurements.
Main Methods:
- Performed unilateral MPW and UPW studies on 33 healthy controls.
- Calculated PLD using both OL and PL, determining mean, range, standard deviation, and upper limits of normal.
- Analyzed 74 hands from 50 patients with confirmed median neuropathy.
Main Results:
- Abnormal cut-offs for MPW and UPW were 1.8 ms (OL) and 2.3 ms (PL).
- Abnormal cut-offs for PLD were 0.5 ms for both OL and PL.
- PLD and UPW parameters showed consistency between controls and carpal tunnel syndrome patients regardless of OL or PL measurement.
Conclusions:
- Recommends an abnormal PLD cut-off of 0.5 ms to minimize false positives.
- This value is slightly higher than previous recommendations, enhancing diagnostic specificity.
- Onset latency and peak latency measurements appear to have similar clinical utility for these parameters.