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Case 12
Published in Andrew Solomon, Julia Anstey, Liora Wittner, Priti Dutta, Clinical Cases, 2021
Andrew Solomon, Julia Anstey, Liora Wittner, Priti Dutta
Typical features of a demyelinating neuropathy are:Prolonged F-wave latencyProlonged distal motor latencyReduced motor neuron conduction velocityIncreased temporal dispersionFocal conduction blocks
Neurologic Diagnosis
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
The F-wave is a late motor response evoked by a supramaximal stimulus of a motor nerve (e.g. the median nerve at the wrist). Nerve stimulation produces a bidirectional action potential in the motor axons, traveling not only orthodromically to produce the initial direct CMAP (the M-wave) but also antidromically to activate some anterior horn cells that then produce a later CMAP (the F-wave). The F-wave is much smaller (1–5% of the M-wave) and more variable than the M-wave (Figure 1.47). The name derives from its first recordings from foot muscles by Magladery and McDougal in 1950.5 The F-wave latency is a measure of the motor conduction time from stimulation site to the anterior horn cell and then back again to the recording site, so it can test conduction in the proximal segments of nerves and spinal roots. F-waves may be delayed or lost with proximal disturbances of conduction, but they are rarely a diagnostic finding in isolation.
Bioelectric and Biomagnetic Signal Analysis
Published in Arvind Kumar Bansal, Javed Iqbal Khan, S. Kaisar Alam, Introduction to Computational Health Informatics, 2019
Arvind Kumar Bansal, Javed Iqbal Khan, S. Kaisar Alam
The waveform for atrial fibrillation is shown in Figure 7.12a. P-waves are mostly replaced by rapid low amplitude electrical activities called F-waves (Fibrillation waves). The peak of the F-wave is around 50 microvolts. The atrial excitation pattern is irregular. AF varies from 250 to 500 beats/minute. The RR-interval becomes irregular. Leads II and V1 have the largest ventricular and atrial waves' amplitudes and are used for the analysis of atrial fibrillation.
Spastic muscle stiffness evaluated using ultrasound elastography and evoked electromyogram in patients following severe traumatic brain injury: an observational study
Published in Brain Injury, 2022
Jun Matsumoto-Miyazaki, Shogo Sawamura, Yumiko Nishibu, Maki Okada, Yuka Ikegame, Yoshitaka Asano, Hirohito Yano, Jun Shinoda
Electrophysiological investigation, such as evoked electromyography (EMG) including F wave and H reflex, has been used to detect stretch reflex and hyperexcitability of the spinal motor neuron caused by upper motor neuron syndrome. The F wave, which is the compound action potential induced by the supramaximal antidromic stimulation of a motor neuron, is a useful noninvasive index for spinal motor neuron excitability (26). F wave parameters, including the F/M amplitude ratio (the ratio of the mean F-wave amplitude to direct M-wave potential recorded from the same muscle) and F-wave persistence, which have been used for evaluating spastic hypertonia, had been reported to be increased in patients with upper motor neuron syndrome (26,27). Further, the F wave has been used to evaluate the effects of various treatments for SMO (28–32).
Split-hand index in amyotrophic lateral sclerosis: an F-wave study
Published in Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration, 2019
Zhi-Li Wang, Mingsheng Liu, Qingyun Ding, Youfang Hu, Liying Cui
Clinically, although the CMAP amplitudes, MUNE/MUNIX, and F-wave test are useful parameters for evaluating the loss of LMNs (4–7), CMAP amplitudes lack sensitivity, and MUNE/MUNIX methods are time-consuming and affected by the CMAP amplitudes (4–6). In contrast, F-wave measurement, an electrophysiological method, can reflect subtle subclinical alterations in spinal motoneurons, and may be relatively sensitive for measuring the early processes involved in motor unit loss (8–10). Earlier studies demonstrated that the low value of the F-wave persistence (FP) indicates the loss of function of LMNs and decreased excitability of the motoneuron pool (7,11,12). Consequently, the aim of the present study was to investigate the split-hand phenomenon in patients with ALS by examining the FP of the APB, FDI, and ADM, and to propose a novel SI measure using FP (SIFP). We also studied the diagnostic accuracy of the SIFP for differentiating patients with ALS from HCs.
Myasthenia gravis and chronic inflammatory demyelinating polyneuropathy in the same patient – a case report
Published in International Journal of Neuroscience, 2018
Weiwei Quan, Junhui Xia, Qiuling Tong, Jie Lin, Xiaolu Zheng, Xuezhi Yang, Dewei Xie, Yiyun Weng, Xu Zhang
He was then admitted to our hospital. Neurological examination revealed bilateral ptosis, bilateral periphery facial paralysis, soft palate plegia and generalized areflexia. Muscle strength of limbs was proximally 4/5 and distally 4+/5. Vibration and position sensation were decreased in feet and bilateral gastrocnemius muscles were tender. Lumbar puncture showed normal pressure and color, with protein 2.113 g/L and leukocytes 0 cell/mm3. Nerve conduction study was showed in Table 1. Motor distal latency prolongation was equal or greater than 50% above upper limit of normal values in bilateral median, left ulnar, bilateral posterior tibial and bilateral peroneal nerves, and reduction of motor conduction velocity was equal or greater than 30% below lower limit of normal values in left posterior tibial and left peroneal nerves. F-wave was absent in posterior tibial nerves. He was diagnosed as definite CIDP referring to the diagnostic criteria of European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS), in which he met the standards of clinical diagnostic criteria and electrodiagnostic criteria [4]. Then he was treated with intravenous immunoglobulin (20 g daily for five days). Condition was not significantly improved.