Increase of vibration threshold during wrist flexion in patients with carpal tunnel syndrome

The most prominent symptoms of carpal tunnel syndrome (CTS) are sensory, with intermittent numbness, paraesthesiae and pain in the fingers innervated by the median nerve. No consistent signs are found by neurological examination, however. Conventional sensibility tests are positive in only about 50% of the cases. This applies also to quantitative tests such as measurement of the perception threshold for vibration (VT). In an attempt to find a more reliable indication and improve the diagnostic value of sensory testing, determination of VT was combined with provocation by means of wrist flexion. In a patient group with neurophysiologically verified CTS, all patients exhibited an increase to at least twice the VT value in the fingers innervated by the median nerve. No increase was seen in the little finger or in a control group of patients with digital paraesthesiae but with normal neurophysiological findings. It is concluded that VT measurements during wrist flexion can be used as a supplementary or alternative diagnostic criterion to indicate that the nerve dysfunction is located in the carpal tunnel.