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SFEMG Signal Atlas - Highlights - Stimulated - FWaves, Extra Discharges
- 1. ©2024 J.A. Kouyoumdjian, D.B. Sanders, E.V. Stålberg Stimulation Effects of F-waves and Extra-discharges
- 2. ©2024 J.A. Kouyoumdjian, D.B. Sanders, E.V. Stålberg F-response to the first spike Percutaneous stimulation Frontalis - 100 µV / 3 ms Frontalis - 100 µV / 3 ms 100 ms 10 ms 90 ms F After an F-wave. the response latency is shortened at the next stimulation For facial muscles this reduction is approximately 10ms shorter, and for limb muscles around 20 ms
- 3. ©2024 J.A. Kouyoumdjian, D.B. Sanders, E.V. Stålberg Effect of F-response. In this figure, the F-responses are not seen due to slow sweep speed Percutaneous stimulation Frontalis - 0.5 mV / 3 ms Frontalis - 0.2 mV / 1.5 ms F-response or extradischarge (not shown). Note a disturbance with latency shortening on the next spike after the spurious late response. Latency (µs) v Response nr
- 4. ©2024 J.A. Kouyoumdjian, D.B. Sanders, E.V. Stålberg Complicated recording. The first latency shift may be due to F-response or extradischarge (1). The second latency shift may reflect recording after an impulse blocking (2). Latency jumps with different causes: F-response gives shortened latency (1) due to extra VRF effect Blocking gives prolonged latency (2) due to lack of cumulated VRF effect Percutaneous stimulation Frontalis - 0.2 mV / 3 ms impulse blocking 1 2 Latency (µs) v Response nr
- 5. ©2024 J.A. Kouyoumdjian, D.B. Sanders, E.V. Stålberg F-response or extradischarge (latency shortening) and response after impulse blocking (latency lengthening) affect the next spike due to the velocity recovery function effect. shortening latency lenghtening latency Frontalis - 0.2 mV / 3 ms shortening latency lenghtening latency impulse blocking after an F-response Latency jumps with different causes: F-response gives shortened latency (1) due to extra VRF effect Blocking gives prolonged latency (2) due to lack of cumulated VRF effect Percutaneous stimulation Latency (µs) v Response nr
- 6. ©2024 J.A. Kouyoumdjian, D.B. Sanders, E.V. Stålberg Frontalis - 0.2 mV / 3 ms Frontalis - 0.5 mV / 3 ms Effect of an extra-discharge. Note the latency shortening of the next spike after the spurious extra- discharge Percutaneous stimulation extra discharge (identical shape as preceding response), judged from latency Latency (µs) v Response no
- 7. ©2024 J.A. Kouyoumdjian, D.B. Sanders, E.V. Stålberg F-response Percutaneous Stimulation Frontalis - 0.1 mV / 3 ms axon 1 axon 2 F-response to the axon 1
- 8. ©2024 J.A. Kouyoumdjian, D.B. Sanders, E.V. Stålberg Note how a single F-response or extra discharge (not shown) spike disrupts latency to all recorded spikes, indicating they are from fibers of the same motor unit. Percutaneous stimulation Frontalis - 0.5 mV / 1.5 ms Frontalis - 0.5 mV / 1.5 ms Latency (µs) v Response nr Latency (µs) v Response nr
- 9. ©2024 J.A. Kouyoumdjian, D.B. Sanders, E.V. Stålberg Extradischarge shortens the latency at the next stimulation Percutaneous stimulation Frontalis – 500 µV / 8 ms 9.268 ms 9.209 ms * MCD = 16 µs Latency (µs) v Response nr
- 10. ©2024 J.A. Kouyoumdjian, D.B. Sanders, E.V. Stålberg Frontalis – 2 mV / 1 ms Extradischarges shorten the latency on the next spike Percutaneous stimulation
- 11. ©2024 J.A. Kouyoumdjian, D.B. Sanders, E.V. Stålberg Frontalis – 2 mV / 1 ms Two extradischarges shorten the latency on the stimulations Percutaneous stimulation Frontalis – 0.2 mV / 1.5 ms
- 12. ©2024 J.A. Kouyoumdjian, D.B. Sanders, E.V. Stålberg Effect of F-response Percutaneous stimulation Note the shortening of the latency immediately after an F- response or extradischarge (not shown). Five discharges (arrow above) were removed, corresponding to the dots (arrows below). Frontalis - 0.1 mV / 0.5 ms Frontalis - 0.1 mV / 0.5 ms MCD = 48 µs MCD = 38 µs Latency (µs) v Response no