Comparison of Sensitivities between Median-Thumb Sensory Distal Latency and Conventional Nerve Conduction Studies in Electrodiagnosis of Carpal Tunnel Syndrome
Chinapat Gerawarapong MD*
Affiliation : * Department of Rehabilitation Medicine, Faculty of Medicine, Naresuan University, Phitsanulok, Thailand
Objective : Compare the sensitivities of median-thumb sensory distal latency (M-T sensory DL) with other standard nerve
conduction studies (NCSs) in patients with carpal tunnel syndrome (CTS).
Material and Method: Eighty-eight participants’ hands, obtained retrospectively between June 2012 and August 2013, were
included and divided into two groups, 48 CTS hands and 40 control hands, respectively. All clinical data, demographic
characteristics, and electrodiagnostic (EDX) findings of each test were compared and analyzed.
Results : M-T sensory DL had the highest sensitivity. It was 81.3% equal to wrist-palm sensory nerve conduction velocity
(W-P sensory NCV) and median-radial sensory distal latency difference (M-RSLD). Specificity of the M-T sensory DL was
95.0%, less than wrist-palm motor nerve conduction velocity (W-P motor NCV) (100.0%), wrist sensory DL (100.0%), and
median-thumb sensory nerve conduction velocity (M-T sensory NCV) (100.0%), respectively. Furthermore, using a
combination of the EDX tests, both M-T sensory and median sensory NCSs performed equally with higher diagnostic
predictive values than the median motor NCS.
Conclusion : The M-T sensory DL is a valuable NCS for the diagnosis of CTS. Overall, it performs with the highest sensitivity
and accuracy when used in a single EDX test or combined with M-T sensory NCV.
Keywords : Carpal tunnel syndrome, Median-thumb sensory distal latency, Electrodiagnosis, Nerve conduction study
