Follow-up study on F-wave in patients with lumbosacral radiculopathy. Comparison between before and after surgery

The aim of this study is to explore the clinical value of follow-up examinations of F-wave in patients with lumbosacral radiculopathy. Postoperative changes in the initial abnormalities and their relationship with improvement in clinical findings were examined. Results from conventional motor nerve conduction study at knee-ankle segment are also discussed. The subjects were 30 patients with unilateral lumbosacral radiculopathy caused by herniated disc. F-waves were obtained from abductor hallucis and extensor digitorum brevis by supramaximal stimulation to tibial and peroneal nerves, respectively, at the ankle. Minimal latency (Fmin), maximal latency (Fmax), chronodispersion (Fdif) and duration (Fdur) were used as the parameters. No subject had abnormal motor nerve conduction velocity (MCV) throughout the course of this study, and there was no significant difference between preoperative and postoperative levels. Peroneal Fmin, Fmax, Fdif and tibial Fdur all showed significant (p < 0.05 in Wicoxon signed-rank test) improvement after surgery. Moreover, these overall improvements significantly (p < 0.05 in chi 2 test) correlated with recovery in muscle weakness. However, normalization of F-wave was not always associated with full recovery in muscle weakness at that time. These findings suggested that follow-up examination of F-wave was of value for objective assessment after operation.