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Updated: May 4, 2026
Screening of Axonal Degeneration in Carpal Tunnel Syndrome Using Ultrasonography and Nerve Conduction Studies
Published on: January 11, 2019
A study of interpolation method in diagnosis of carpal tunnel syndrome
Alireza Ashraf1, Abbas Daghaghzadeh, Mahshid Naseri
1Department of Physical Medicine and Rehabilitation, Shiraz University of Medical Sciences, Shiraz, Iran ; Burn Research Center, Shiraz University of Medical Sciences, Shiraz, Iran.
Context:
The low correlation between the patients' signs and symptoms of carpal tunnel syndrome (CTS) and results of electrodiagnostic tests makes the diagnosis challenging in mild cases. Interpolation is a mathematical method for finding median nerve conduction velocity (NCV) exactly at carpal tunnel site. Therefore, it may be helpful in diagnosis of CTS in patients with equivocal test results.
Aim:
The aim of this study is to evaluate interpolation method as a CTS diagnostic test.
Settings And Design:
Patients with two or more clinical symptoms and signs of CTS in a median nerve territory with 3.5 ms ≤ distal median sensory latency <4.6 ms from those who came to our electrodiagnostic clinics and also, age matched healthy control subjects were recruited in the study.
Materials And Methods:
Median compound motor action potential and median sensory nerve action potential latencies were measured by a MEDLEC SYNERGY VIASIS electromyography and conduction velocities were calculated by both routine method and interpolation technique.
Statistical Analysis Used:
Chi-square and Student's t-test were used for comparing group differences. Cut-off points were calculated using receiver operating characteristic curve.
Results:
A sensitivity of 88%, specificity of 67%, positive predictive value (PPV) and negative predictive value (NPV) of 70.8% and 84.7% were obtained for median motor NCV and a sensitivity of 98.3%, specificity of 91.7%, PPV and NPV of 91.9% and 98.2% were obtained for median sensory NCV with interpolation technique.
Conclusions:
Median motor interpolation method is a good technique, but it has less sensitivity and specificity than median sensory interpolation method.
