A sensitive new median-ulnar technique for diagnosing mild Carpal Tunnel Syndrome

Carpal Tunnel Syndrome (CTS) is easily the most common focal peripheral nerve compression. The primary diagnostic tool is electrodiagnosis, although 13-27% of patients with symptoms and signs of CTS have normal electrodiagnostic results. The goal of this study was to create a more sensitive and specific latency difference criteria without any additional testing beyond the minimum. Statistical theory indicates that this would occur by comparing the latency most sensitive to CTS to the least sensitive latency. Data was evaluated from 68 normal hands, 23 hands of patients with symptoms and signs of CTS but normal standard results, and 88 hands of patients with CTS symptoms and signs of CTS with the diagnosis confirmed with standard criteria. The Median Sensory latency was the most sensitive parameter, while the Ulnar Motor Latency varied least in the presence of CTS, making the (Median Sensory-Ulnar Motor) latency difference the criteria of choice. Setting a cutoff value of 0.8 msecs for this difference correctly classified all normals, and all hands with CTS by standard criteria, and classified as abnormal 19/23 (82%) of hands with symptoms and signs of CTS but negative results by standard criteria. Overall the (Median Sensory-Ulnar Motor) Latency difference is a simple, easy, sensitive and specific test for CTS.