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Across-tarsal-tunnel motor-nerve conduction technique
G Felsenthal1, D H Butler, M S Shear
1Department of Rehabilitation Medicine of Sinai Hospital, Baltimore, MD.
Archives of Physical Medicine and Rehabilitation
|January 1, 1992
Summary
This study introduces a new method to measure nerve conduction across the tarsal tunnel, improving diagnosis of tibial nerve compression. This technique differentiates proximal from distal nerve compression, aiding in accurate tarsal tunnel syndrome diagnosis.
Area of Science:
- Neurology
- Neurophysiology
- Orthopedic Surgery
Background:
- Tarsal tunnel syndrome involves tibial nerve compression behind the medial malleolus.
- Current nerve conduction studies struggle to differentiate proximal versus distal tibial nerve compression.
- Measuring onset and peak latencies for motor-evoked potentials is challenging.
Observation:
- This study measured across-tarsal-tunnel latencies and amplitude decrements for medial and lateral plantar nerves.
- Specific electrode placements were used over the flexor pollicis brevis.
- Onset and peak latencies, along with amplitude decrements, were recorded for both nerve divisions.
Findings:
- Mean + 2SD across-tunnel onset latency for the medial plantar nerve is 3.2msec (peak 2.9msec), with a 29.3% amplitude decrement.
- Mean + 2SD across-tunnel onset latency for the lateral plantar nerve is 3.2msec (peak 2.9msec), with a 27.2% amplitude decrement.
- Distal latencies were 5.9msec onset / 9.5msec peak for medial and 5.9msec onset / 9.7msec peak for lateral plantar nerves.
Implications:
- This method allows differentiation between proximal and distal tibial nerve compression within the tarsal tunnel.
- Accurate measurement of across-tarsal-tunnel latencies and amplitude decrements enhances diagnostic precision.
- The findings provide normative data for across-tarsal-tunnel nerve conduction studies, aiding clinical diagnosis and research.