F-waves of peroneal and tibial nerves in the differential diagnosis and follow-up evaluation of L5 and S1 radiculopathies

Chaojun Zheng, Jingjuan Liang, Cong Nie, Yu Zhu, Feizhou Lu, Jianyuan Jiang

To investigate F-wave as a method to identify a specific root lesion of L5 or S1 and to quantitatively evaluate the severity and progression of motor root lesions in lumbosacral radiculopathies (LR). Both peroneal and tibial F-waves were performed bilaterally in 142 patients with unilateral L5 or S1 radiculopathies and 37 controls along with Medical Research Council (MRC) evaluation, and soleus H-reflexes were tested bilaterally in 78 of these 142 cases. Both F-wave and MRC were re-evaluated approximately 1 year after initial examination in 65 patients. Abnormal peroneal F-waves were found in 34 patients with L5 radiculopathy (34/67, 50.7%) along with normal tibial F-waves and soleus H-reflexes in all tested cases. By contrast, 27 patients with S1 radiculopathy presented abnormal tibial F-waves (27/76, 36.0%) along with normal peroneal F-waves in all 76 cases and abnormal soleus H-reflexes in 38 of 47 (80.9%) cases. There were significant differences in involved side F-duration among different MRC scales in both radiculopathy groups (P < 0.05). Follow-up analysis demonstrated slow progression of both F-wave abnormalities and muscle weakness in patients undergoing conservative treatment (P < 0.05). Comparisons of F-waves between the same nerve on both sides and between peroneal and tibial nerves in the same leg may clearly increase the validity of F-waves for evaluating a specific motor root lesion of L5 or S1. Furthermore, a quantitative comparison of F-waves may provide additional information on the severity of individual root lesions and their progression even in the early stages of disease. These slides can be retrieved under Electronic Supplementary Material.