Median nerve F-wave study derived by flexor carpi radialis.

F-responses are produced by the antidromic activation of a limited number of motoneurones and its study can be used as a diagnostic criteria in cervical radiculopathies. Usually ulnar nerve stimulation (hypothenar derivation) and median nerve stimulation (thenar derivation) is used, so providing information mainly about 8th cervical root and 1st thoracic root. The authors describe a method for studying F-wave by median nerve stimulation and flexor carpi radialis derivation to evaluate C6-C7 roots. F-waves were clearly individuated in 47 normal subjects (94 nerves) aged from 21 to 59. Latency range was 18.0-24.0 msec, mean 21.4 +/- 1.48 (2 SD). The results of the test applied on 6 paradigmatic cases of C6-C7 radiculopathy are reported.