Objective: To determine the source of an abnormal pattern of latency shifts leading to falsely high jitters in single fibre electromyography (SFEMG). Methods: We observed a sudden shortening of the latency to an indiv...Objective: To determine the source of an abnormal pattern of latency shifts leading to falsely high jitters in single fibre electromyography (SFEMG). Methods: We observed a sudden shortening of the latency to an individual single fibre spike component followed by a gradual return to baseline values during stimulation single fibre electromyography (SFEMG) of the facial muscle. The pattern could be reproduced in healthy controls. Results: The sudden decrease in latency proved to follow an additional discharge of the muscle fibre, not due to the external stimulus. This additional discharge was identified as an F-response. Conclusions: The mechanism is thought to be a higher muscle fibre conduction velocity resulting from a temporary increase in stimulus frequency, in the form of an extra impulse along the muscle fibre represented by the F-response. Significance: The typical abnormal pattern should be recognised because it can falsely increase the mean jitter. We advice to increase the time base to 50 ms if this pattern is observed and to exclude the affected potentials from jitter measurements.展开更多
The neurophysiological mechanisms for persisting impairment of motor function after Guillain-Barr syndrome (GBS) were assessed in 37 unselected patients 1- 13 years after diagnosis. For evaluation of reinnervation a...The neurophysiological mechanisms for persisting impairment of motor function after Guillain-Barr syndrome (GBS) were assessed in 37 unselected patients 1- 13 years after diagnosis. For evaluation of reinnervation and axonal loss, macroelectromyography (macro-EMG) including measurement of fiber density (FD) was performed. Data from neuropathy symptom score, neuropathy disability score, nerve conduction studies, and quantitative sensory examination were ranked and s ummed to a neuropathy rank sum score (NRSS). The isokinetic muscle strength at t he ankle was measured. Signs of axonal loss with increase of either macro motor unit potential (macro-MUP) amplitude or FD occurred in 76% of patients. The macro-MUP amplitude correlated with muscle strength and with NRSS. Patients wi th evidence of residual neuropathy had increased macro-MUP amplitude and FD as well as decreased muscle strength compared to patients without evidence of res idual neuropathy. We conclude that axonal loss takes place in a substantial numb er of GBS patients and is associated with permanent muscle weakness caused by in sufficient reinnervation. Possible patterns of pathology are discussed in relati on to the macro-EMG findings.展开更多
文摘Objective: To determine the source of an abnormal pattern of latency shifts leading to falsely high jitters in single fibre electromyography (SFEMG). Methods: We observed a sudden shortening of the latency to an individual single fibre spike component followed by a gradual return to baseline values during stimulation single fibre electromyography (SFEMG) of the facial muscle. The pattern could be reproduced in healthy controls. Results: The sudden decrease in latency proved to follow an additional discharge of the muscle fibre, not due to the external stimulus. This additional discharge was identified as an F-response. Conclusions: The mechanism is thought to be a higher muscle fibre conduction velocity resulting from a temporary increase in stimulus frequency, in the form of an extra impulse along the muscle fibre represented by the F-response. Significance: The typical abnormal pattern should be recognised because it can falsely increase the mean jitter. We advice to increase the time base to 50 ms if this pattern is observed and to exclude the affected potentials from jitter measurements.
文摘The neurophysiological mechanisms for persisting impairment of motor function after Guillain-Barr syndrome (GBS) were assessed in 37 unselected patients 1- 13 years after diagnosis. For evaluation of reinnervation and axonal loss, macroelectromyography (macro-EMG) including measurement of fiber density (FD) was performed. Data from neuropathy symptom score, neuropathy disability score, nerve conduction studies, and quantitative sensory examination were ranked and s ummed to a neuropathy rank sum score (NRSS). The isokinetic muscle strength at t he ankle was measured. Signs of axonal loss with increase of either macro motor unit potential (macro-MUP) amplitude or FD occurred in 76% of patients. The macro-MUP amplitude correlated with muscle strength and with NRSS. Patients wi th evidence of residual neuropathy had increased macro-MUP amplitude and FD as well as decreased muscle strength compared to patients without evidence of res idual neuropathy. We conclude that axonal loss takes place in a substantial numb er of GBS patients and is associated with permanent muscle weakness caused by in sufficient reinnervation. Possible patterns of pathology are discussed in relati on to the macro-EMG findings.
