Diagnostic tests in carpal tunnel syndrome

In a first series 100 patients underwent surgical treatment for carpal tunnel syndrome (CTS) after being tested by provocative tests for sensory disturbances preoperatively. In addition to the well-established tests like passive wrist flexion (Phalen's test) or wrist extension, active movement tests of the patient against resistance were investigated. Tests of active movement were introduced because of the high values of intraoperatively measured pressure at the median nerve, similar to those recorded with passive movements. All investigated provocative tests for sensory disturbances related to CTS, investigated by active and passive movements, were positive in 72% to 84% of patients. Average delay times for reaction of these provocative tests ranged between 15.7 and 19.5 s. Furthermore Tinel's sign showed a sensitivity of 64% and the flick sign one of 69%. The specificity of tests and signs for the CTS was assessed on a group of 50 surgically treated patients with cervical nerve root entrapment at the C5-C8 level. In this group and a second CTS group the most sensitive of each test in the first series (active and passive provocational movement), Tinel's sign and flick sign were investigated. By forming subgroups in both diseases we showed that the results of the total groups were not influenced by a possible double crush. We could demonstrate high sensitivities in cervical nerve root entrapment for Phalen's sign with 74% and for active thumb abduction with 68% and a medium sensitivity for Tinel's sign with 40%--thus implying low specificity for CTS. Only the flick sign turned out to be relatively specific for CTS--its sensitivity in cervical nerve root entrapment was around 26%--indicating its potential to function as a valid criterion for the differential diagnosis of CTS and cervical nerve root entrapment syndrome.