Characteristics of late responses in S1 radiculopathy

Abstract

Electrophysiological research methods, in particular late nerve conduction responses, play an important role n the diagnosis of a number of neurogenic disorders and, in particular in lumbosacral radiculopathy. Late responses include the F-wave, H-reflex, and A-wave.The purpose of this study was to determine the diagnostic value of late responses to tibial nerve stimulation in patients with isolated S1 radiculopathy in comparison with clinical findings. We examined 32 patients with isolated S1 radiculopathy (16 women, 16 men), their average age was 43.5 ± 9.3 years.An electroneuromyographic study of the tibial nerve on the injured side revealed the presence of an A-wave in 20 patients (62.5 %, p < 0.001). It was significantly more often combined with tests for spinal root irritation, and its localization before the F-wave was a characteristic feature of this pathology. The analysis of the F-wave parameters showed an increase in its duration (p = 0.001) compared to the uninjured side, and compared to the control group there was a prolongation of both duration and latency (p < 0.001). Patients with the presence of an A-wave had more pronounced changes in the duration and latency of the F-wave on the injured and uninjured sides. When analyzing the H-reflex, it was found to be absent in 14 (43.8 %) and decreased in amplitude in 9 (28.1 %) patients on the injured side. The absence of the H-reflex was significantly more often detected in patients with the absence of the Achilles reflex (p < 0.05). The number of patients with the presence of an A-wave did not differ from that of patients with an increased duration of the F-wave or a decrease in the amplitude of the H-reflex (p > 0.05).