Diagnostic value of extensor digitorum brevis F-wave in L5 root compression.

The sensibility of F-wave in detecting lumbosacral radicular compression has been found to range from 65% to 18%. The present study was performed on 24 patients suffering from unilateral L5 compressive radiculopathy. The aim was to verify the reliability of extensor digitorum brevis (EDB) F-wave in the diagnosis of L5 root impairment, by using different parameters such as minimal, mean, maximal latency and the difference of these parameters between the affected and unaffected sides. In all patients conventional needle EMG was also performed bilaterally. While the needle EMG showed abnormalities in L5 innervated muscles of all patients, at least one of the different EDB F-wave parameters was found to be abnormal in only 7 patients (29.2%). Moreover no significant relation was observed between the severity of EMG and F-wave abnormalities. We conclude that conventional needle EMG appears to be the most useful electrophysiological technique in the diagnosis of L5 compressive radiculopathy, while EDB F-wave does not provide additional information.