Pilot Study, Aimed at Describing in Myography, the Collapse of the Muscular Response Visualized in the Scratch Collapse Test, in Carpal Tunnel Syndrome

The Scratch Collapse Test (SCT) is a neurocutaneous reflex used to detect peripheral nerve compression in nerve tunnel syndromes. It first involves applying a sensory stimulus to the skin over the suspected nerve compression point, then bilaterally testing the strength of a specific muscle in the patient. Compression is then manifested by a transient loss of strength in the muscle on the affected side, while it is preserved on the healthy side. This loss of strength is transient and disappears after a few seconds. This test can be performed during a patient's clinical examination, with the physician assessing strength or, conversely, muscle collapse. However, while several articles have described the relevance of this test, as well as its sensitivity and specificity, no study has specifically investigated and measured this observed loss of eccentric muscle tone and its unilateral and transient nature, even though the phenomenon of CSP (cutaneous silent period) has been described.

We therefore propose to analyze the myographic tracing obtained in patients diagnosed with unilateral carpal tunnel syndrome. A transient loss of muscle tone is expected by selective needle myography on the pathological side after cutaneous sensory stimulation of the wrist, while cutaneous sensory stimulation on the healthy side does not alter the tracings obtained by myography.