Ring Finger Sensory Latency Difference in the Diagnosis and Treatment of Carpal Tunnel Syndrome

Abstract Objective: To explore the evaluation value of the sensitivity of the median/ulnar nerve sensory latency difference in the diagnosis of carpal tunnel syndrome and the evaluation value of severity.Methods: 122 patients with CTS and 42 normal controls were collected from the department of Neurology in Renmin Hospital of Wuhan University from July 2019 to January 2021. Electrophysiological tests were performed on the CTS patients group and the control group. The distal latency of the sensory nerve action potential (SNAP) of the median nerve and the ulnar nerve of the two groups was recorded. According to electrophysiological results，the patients were divided into three grades: mild, moderate and severe, the sensitivity of the nerve sensory action potential distal latency (SDL) to the diagnosis of CTS patients were analyzed, and the relationship with the severity of CTS was analyzed.Results: ①There were significant differences between the median nerve sensory action potential distal latency (MSDL) of 179 affected hands and the control group; And median and ulnar sensory latency difference to ring finger (MUD) was significantly different from the control group; But ulnar nerve sensory action potential distal latency （USDL） was not significantly different from the control group (P=0.182). When the cutoff value of MSDL is 2.465ms, the sensitivity is 85.5% and the specificity is 90.4%; when the cutoff value of MUD is 0.38ms, the sensitivity is 100% and the specificity is 100%. ②In the mild, moderate, severe and control group, there was no significant difference in USDL between all the groups (P=0.56)a; between the control group and the mild group, moderate group, and severe group, and between the mild and moderate, significant differences were found in the MSDL and MUD. No significant difference between mild and severe (P=0.66), moderate and severe (P=1.00). ③ MSDL and MUD are correlated with the severity of CTS. There is no correlation between USDL and CTS severity.Conclusion: The ulnar nerve is not damaged in CTS; a smaller MSDL can reflect median nerve damage, which is beneficial to the early diagnosis of CTS; MUD is more sensitive than MSDL in diagnosing CTS; MUD is correlated with severity, which is beneficial to pain for patients who are more sensitive and cannot tolerate electrical stimulation, perhaps only measuring MUD can reflect the severity, relieve the patient's pain, and can be used to evaluate the therapeutic effect.