Related Experiment Video
Updated: Jul 16, 2026

Screening of Axonal Degeneration in Carpal Tunnel Syndrome Using Ultrasonography and Nerve Conduction Studies
Published on: January 11, 2019
The median palmar cutaneous nerve in normal subjects and CTS
Rahul Rathakrishnan1, Aravinda Kannan Therimadasamy, Y H Chan
1Neurology, National University Hospital, Singapore.
Objective:
The neurophysiological confirmation of carpal tunnel syndrome (CTS) relies on detecting abnormal median nerve transcarpal conduction in the presence of unaffected comparator nerves. We compare the palmar cutaneous median branch (PCBm) with the ulnar sensory nerve conduction to digit 5 (US(5)) as comparator nerves for diagnosing CTS.
Methods:
In a prospective case control study of patients with clinically defined carpal tunnel syndrome and normal subjects, we determined and compared the PCBm and US(5) conduction velocity.
Results:
We examined 57 hands with clinically defined CTS and 59 control hands. Comparison showed highly significantly slowed PCBm conduction (p<0.0001) but not for US(5) conduction (p=0.488). Using a 3 percentile cut-off for abnormality derived from controls, PCBm conduction velocity was abnormal in 46% of CTS hands.
Conclusions:
The high frequency of PCBm nerve conduction abnormality in CTS suggests that this nerve should not be used as a comparator nerve for the neurophysiological diagnosis of CTS. This finding may help explain some of the extension of sensory symptoms outside the median nerve distribution in CTS.
Significance:
In CTS frequent abnormality of PCBm conduction makes this a poor comparator nerve and may explain extension of sensory symptoms beyond the median nerve.
Related Concept Videos
Spinal Nerves: Plexus I
The Cervical Plexus
The cervical plexus, formed by the anterior rami of the first four...
Muscles of the Forearm that Move the Hand and Fingers
Anterior Compartment
The anterior compartment muscles originate from the humerus. They primarily function as flexors and are also known as flexor muscles. They typically insert on the carpals, metacarpals, and phalanges. The superficial layer includes the flexor carpi radialis,...
Major Somatic Sensory Pathways
Local Anesthetics: Differential Sensitivity of Nerve Fibers
Somatosensation
Arteries of the Upper Limbs