title: The significance of delayed long-loop responses to ankle displacement for the diagnosis of multiple sclerosis.
abstract: The present study compares the results of sensory evoked potentials after stimulation of the tibial nerve with measurements of short (M1), medium (M2) and long-loop latency (M3) responses of leg muscles in 42 patients suffering from multiple sclerosis. EMG responses were elicited by a movable platform which was tilted in pitch toe-up around the subject's ankle joint. The short latency response of the triceps surae muscle was nearly always normal in latency. The M2 response was lacking in about 30% of the patients and 10% of normals. The long latency response (M3) in the antagonistic anterior tibial muscle was significantly delayed (beyond 162 msec = AM + 2.5 S) in 69% of the patients. The delayed M3 response was found to indicate demyelination as reliably as the delayed somatosensory evoked potential (66% of the patients). The frequency of coincident results in the entire group was 86%. Additional information is gained in cases where SEPs are normal, but M3 is delayed (7%). Furthermore, patients lacking P40 of the SEP still exhibit M3 responses, the latency of which may be measured (24%). The results favour the assumption that M3 is mediated by a supraspinal pathway.
mesh_terms: D000842:Ankle; D001921:Brain / Q000503:physiopathology; D004576:Electromyography; D005073:Evoked Potentials, Somatosensory; D006801:Humans; D009068:Movement; D009103:Multiple Sclerosis / Q000175:diagnosis* / Q000503:physiopathology; D009132:Muscles / Q000503:physiopathology*; D009434:Neural Pathways; D011930:Reaction Time; D012026:Reflex, Stretch; D013977:Tibia