Myoclonus and other jerky movement disorders

Myoclonus and other jerky movements form a large heterogeneous group of disorders. Clinical neuro-physiology studies can have an important contribution to support diagnosis but also to gain insight in the pathophysiology of different kind of jerks. This review focuses on myoclonus, tics, startle disorders, restless legs syndrome, and periodic leg movements during sleep. Myoclonus is defined as brief, shock-like movements, and subtypes can be classified based the anatomical origin. Both the clinical phe-notype and the neurophysiological tests support this classification: cortical, cortical-subcortical, subcortical/non-segmental, segmental, peripheral, and functional jerks. The most important techniques used are polymyography and the combination of electromyography-electroencephalography focused on jerk-locked back-averaging, cortico-muscular coherence, and the Bereitschaftspotential. Clinically, the differential diagnosis of myoclonus includes tics, and this diagnosis is mainly based on the history with premonitory urges and the ability to suppress the tic. Electrophysiological tests are mainly applied in a research setting and include the Bereitschaftspotential, local field potentials, transcranial magnetic stimulation, and pre-pulse inhibition. Jerks due to a startling stimulus form the group of startle syn-dromes. This group includes disorders with an exaggerated startle reflex, such as hyperekplexia and stiff person syndrome, but also neuropsychiatric and stimulus-induced disorders. For these disorders polymyography combined with a startling stimulus can be useful to determine the pattern of muscle acti-vation and thus the diagnosis. Assessment of symptoms in restless legs syndrome and periodic leg move-ments during sleep can be performed with different validated scoring criteria with the help of electromyography. (c) 2022 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

This review focuses on myoclonus and other jerky movements, providing an overview of their classification, clinical features, and the contribution of clinical neuro-physiology studies in supporting diagnosis and understanding the underlying pathophysiology. The differential diagnosis of myoclonus, including tics, is mainly based on clinical history and the ability to suppress the movements. Electrophysiological tests play a significant role in researching startle syndromes and assessing symptoms in restless legs syndrome and periodic leg movements during sleep, using validated scoring criteria and techniques such as polymyography and electromyography-electroencephalography.