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Surface EMG during voluntary gentle muscle contraction in case 1 (A) and case 2 (B). (A) Note repetitive EMG discharges in the FCU during and after flexion of the right elbow. (B) Note frequent high amplitude discharges in all muscles during flexion of the left elbow. In the FCU, ECR and BB, those discharges are superimposed on the continuous discharges associated with voluntary muscle contraction. Abbreviations are the same as for Fig. 1. Lt: left.
Source publication
Objective
Patients with motor neuron disease rarely present with fasciculation which is large enough to be clinically recognized as myoclonus. This study is aimed at elucidating the features of large fasciculation manifesting as myoclonus by using surface electromyography (surface EMG) and dynamic echomyography (dynamic Echo).
Methods
Four patient...
Context in source publication
Context 1
... dis- charges corresponding to fasciculation were superimposed on the discharges related to voluntary muscle contraction in the contract- ing muscle. In other muscles of the same extremity, repetitive dis- charges corresponding to fasciculation and/or myoclonus appeared and remained for a few seconds after the voluntary contraction was stopped (Fig. ...
Similar publications
Muscle fasciculations, resulting from the spontaneous activation of motor neurons, may be associated with neurological disorders, and are often assessed with intramuscular electromyography (EMG). Recently, however, both ultrasound (US) imaging and multichannel surface EMG have been shown to be more sensitive to fasciculations. In this study we comb...
Citations
... However, in later stages with significant muscle atrophy, denervation-reinnervation with axonal sprouting and the formation of unstable motor units, ectopic activity of peripheral motor axonal generators is primarily responsible for complex fasciculation. Studies by Inoue et al. 7 and Bhat et al. 8 have both shown that fasciculation in motor neuron disease (MND) can give rise to small-amplitude, jerky "twitches" in the fingers (especially with the hands outstretched and fingers extended), a phenomenon known as 'minipolymyoclonus, ' or it can present with large amplitude "shock-like" movements mimicking spinal myoclonus. 7 ...
‘Minipolymyoclonus’ or ‘polyminimyoclonus’ is a hyperkinetic movement disorder phenomenology characterized by intermittent, low-amplitude, arrhythmic movements of the hands, commonly of several fingers, with “amplitudes just sufficient to produce visible and palpable movements of the joints.” It is mostly noticed while the individual is maintaining a posture (commonly outstretched hands) or during action (especially the initial phase of movement). The term “minipolymyoclonus” was first used by Dennis Giblin and then described by Alfred J. Spiro in the context of differentiating a neuropathic from a myopathic disorder in 1970.The pathophysiology of this entity is confusing because its presence has been described in different neurological disorders such as anterior horn cell (AHC) disease and peripheral nerve hyperexcitability disorders as well as central neurodegenerative and epileptic disorders. In the field of movement disorders, the use of the term ‘minipolymyoclonus’ is currently a matter of debate. From this viewpoint, we have critically analyzed the term ‘minipolymyoclonus’ from a pathophysiological perspective
... 58 It has also been shown to facilitate differentiation of large fasciculations from myoclonus. 59,60 However, it is inferior to EMG for defining the complexity of fasciculations, and fibrillations are better identified by needle EMG. 61 Nevertheless, quantitative fasciculation analysis allowed differentiation from mimics with high sensitivity and specificity. ...
Amyotrophic lateral sclerosis is a devastating neurodegenerative condition with few effective treatments. Current research is gathering momentum into the underlying pathology of this condition and how components of these pathological mechanisms affect individuals differently, leading to the broad manifestations encountered in clinical practice. We are moving away from considering this condition as merely an anterior horn cell disorder into a framework of a multisystem neurodegenerative condition in which early cortical hyperexcitability is key. The deposition of TAR DNA-binding protein 43 is also a relevant finding given the overlap with frontotemporal dysfunction. New techniques have been developed to provide a more accurate diagnosis, earlier in the disease course. This goes beyond the traditional nerve conduction studies and needle electromyography, to cortical excitability studies using transcranial magnetic stimulation, and the use of ultrasound. These ancillary tests are proposed for consideration of future diagnostic paradigms. As we learn more about this disease, future treatments need to ensure efficacy, safety, and a suitable target population to improve outcomes for these patients. In this time of active research into this condition, this paper highlights some of the areas of controversy to induce discussion surrounding these topics.
... Most recently, SPiQE's automated algorithm was employed to detect a median FP frequency of 65/min from biceps and gastrocnemius (Bashford et al., 2019). In some cases, large amplitude fasciculations may manifest clinically as myoclonus (Inoue et al., 2017). ...
Objective:
Amyotrophic lateral sclerosis (ALS) is an adult-onset neurodegenerative disease that leads to inexorable motor decline and a median survival of three years from symptom onset. Surface EMG represents a major technological advance that has been harnessed in the development of novel neurophysiological biomarkers. We have systematically reviewed the current application of surface EMG techniques in ALS.
Methods:
We searched PubMed to identify 42 studies focusing on surface EMG and its associated analytical methods in the diagnosis, prognosis and monitoring of ALS patients.
Results:
A wide variety of analytical techniques were identified, involving motor unit decomposition from high-density grids, motor unit number estimation and measurements of neuronal hyperexcitability or neuromuscular architecture. Some studies have proposed specific diagnostic and prognostic criteria however clinical calibration in large ALS cohorts is currently lacking. The most validated method to monitor disease is the motor unit number index (MUNIX), which has been implemented as an outcome measure in two ALS clinical trials.
Conclusion:
Surface EMG offers significant practical and analytical flexibility compared to invasive techniques. To capitalise on this fully, emphasis must be placed upon the multi-disciplinary collaboration of clinicians, bioengineers, mathematicians and biostatisticians.
Significance:
Surface EMG techniques can enrich effective biomarker development in ALS.
... In this issue of Clinical Neurophysiology Practice, Inoue and colleagues report on the ultrasound and surface electromyography (EMG) findings of four patients with motor neuron disease (MND) with abnormal involuntary limb movements (Inoue et al., 2017). In two patients, the movements were ''twitches" affecting the fingers of both hands and in the other two patients larger ''shock-like" movements, which clinically resembled myoclonus. ...
Objective
Our goal was to identify the frequency and types of involuntary movements in immune mediated and hereditary polyneuropathies.
Methods
In this prospective study, we included all consecutive patients with immune mediated or hereditary polyneuropathy between January 2017 and November 2019. The presence and type of the involuntary movements were determined by the clinical examination and multichannel surface electromyography.
Results
We identified 23 (48.9%) patients with involuntary movements among 47 patients with immune mediated or hereditary polyneuropathy in the study period. All patients with an involuntary movement had postural tremor with accompanying action and/or rest tremor. Short duration and high-amplitude myoclonus was accompanying in 18 (38.3%) patients. The demographic and clinical characteristics and features of nerve conduction studies were similar between patients with and without involuntary movements.
Discussion
Tremor and myoclonus were frequent in our cohort. Postural tremor was the most frequent subtype. There was no significant relationship between myoclonus or tremor and clinical/electrophysiological features.
Conclusion
For assessing movement disorders in polyneuropathies not only clinical examination, but also electrophysiological studies such as multichannel surface electromyography should be used.
Background:
Information regarding involuntary movements in chronic inflammatory polyneuropathy (CIDP) is gradually increasing. Our goal is to identify the types of involuntary movements in CIDP.
Methods:
All patients who were followed with the diagnosis of CIDP were invited for clinical and electrophysiological evaluations. Demographic and clinical findings (age, gender, duration of illness, diagnosis, treatments) were noted. Clinical examination and multichannel surface electromyography were done. We also performed routine upper and lower extremity peripheral nerve conduction studies, F-waves, long latency reflexes, blink reflex, mixed nerve silent period and cutaneous silent period in all patients.
Results:
Twenty-two patients accepted the invitation. Eleven patients with CIDP had involuntary movements. Ten (45.5%) patients with CIDP had tremor and seven (31.8%) had short-duration and high-amplitude myoclonus. Regarding demographic, clinical and electrophysiological features, there was no significant difference between patients with and without tremor. The latencies of R1, R2 and R2c components of BR were longer among CIDP patients without tremor compared to CIDP patients with tremor. Presence of myoclonus (p = 0.007) and delayed F-waves (p = 0.008) were associated with the presence of tremor.
Conclusion:
Tremor and myoclonus were frequent in CIDP. The fact that myoclonus was detected in the majority of patients only by multichannel surface EMG who were clinically evaluated as pure tremor suggests that a more detailed electrophysiological evaluation is required. There was no difference in the medications used or other clinical features between patients with and without tremor.
