Diagnostic value of F-response in the localization of the level of the lesion of peripheral motor neuron

Abstract

F-wave is a secondary muscle response, which occurs by antidromic activation of the limited number of alphamotoneurons. Based on M- and F-response and the nerve length, the conduction time, conduction velocity, and the ratio of F-response can be determined. These parameters help in assessing the data about functional condition of peripheral motor neurons along the most proximal segment in relatively simple and non-invasive way. In routine practical work, minimal latency of F-wave is measured, while F-wave conduction time, F-wave conduction velocity and F-ratio are not measured. The aim of this research was to examine the importance of F-wave latency, F-wave conducution time, F-wave conduction velocity, and F-ratio in the localization of level of lesion of peripheral motor neurons. Electromyoneurography examination included 50 patients with radiculopathies of lumbosacral part of spinal cord, 50 patients with neuropathy, and 25 healthy persons. Minimal latency of F-wave for tibial nerve and peroneal nerve was determined after 10 stimulations. F-wave latency, F-wave conduction time, F-wave conduction velocity, and F-ratio were determined in accordance with the formulas defined by Kimura. The results of our test have shown that F-wave latency, F wave conducution time, F-wave conduction velocity, were important electrophysiological parameters, while F-ratio was found to be highly sensitive, which made it the most valid electro-physiological parameter in the differentiation of proximal and distal lesion of peripheral motor neuron.