Materiały źródłowe

• #1 Myoclonus – Wikipedia

  https://en.wikipedia.org/wiki/Myoclonus

  Myoclonus is a brief, involuntary, irregular (lacking rhythm) twitching of a muscle, a joint, or a group of muscles, different from clonus, which is rhythmic or regular. […] The specific mechanisms underlying myoclonus are not yet fully understood. Scientists believe that some types of stimulus-sensitive myoclonus may involve overexcitability of the parts of the brain that control movement. […] Key elements of this communication are chemicals known as neurotransmitters, which carry messages from one nerve cell, or neuron, to another. […] Some researchers speculate that abnormalities or deficiencies in the receptors for certain neurotransmitters may contribute to some forms of myoclonus. […] Receptors that appear to be related to myoclonus include those for two important inhibitory neurotransmitters: serotonin, which constricts blood vessels and brings on sleep, and gamma-aminobutyric acid (GABA), which helps the brain maintain muscle control. […] More research is needed to determine how these receptor abnormalities cause or contribute to myoclonus.

• #2

  https://journals.lww.com/annalsofian/fulltext/2021/24030/myoclonus__a_review.5.aspx

  Myoclonus is a hyperkinetic movement disorder characterized by a sudden, brief, involuntary jerk. Positive myoclonus is caused by abrupt muscle contractions, while negative myoclonus by sudden cessation of ongoing muscular contractions. […] The neurophysiological classification of myoclonus by means of electrophysiological tests is helpful in guiding the best therapeutic strategy. […] The neurophysiological classification of myoclonus focuses on the pathophysiologic generator of myoclonus, and the mechanisms of propagation, regardless of its clinical presentation. […] A single disease can have myoclonus caused by different mechanisms. […] Identifying the physiological category also guides in deciding the most effective treatment, as drugs that are effective in cortical myoclonus may not be effective in other types of myoclonus.

• #3 Myoclonus – StatPearls – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/sites/books/NBK537015/

  Myoclonus features diverse causes, anatomic diagnoses, and neurophysiologic presentations, all of which are nonspecific concerning their neuroanatomical source and pathogenesis. […] The specific etiologic mechanisms underlying myoclonus remain poorly understood. At present, researchers theorize that myoclonus may emerge as a consequence of motor strip hyperexcitability, abnormalities or deficiencies in neurotransmitter receptors, imbalances between neurotransmitters, or underlying network abnormalities that have yet to be elucidated. […] One of the chief classification schemes for the evaluation of myoclonus rests upon identifying the neuroanatomic generator of the myoclonus. Myoclonus can arise from loci in the cortex, cortico-subcortical regions (eg, brain stem), subcortical non-segmental overlap, segmental (brain stem or spinal cord), and the peripheral nerves.

• #4 Classification and evaluation of myoclonus – UpToDate

  https://www.uptodate.com/contents/classification-and-evaluation-of-myoclonus

  Myoclonus is a clinical sign that is characterized by brief, shock-like, involuntary movements caused by muscular contractions or inhibitions. Muscular contractions produce positive myoclonus, whereas muscular inhibitions produce negative myoclonus (ie, asterixis). Patients will usually describe myoclonus as consisting of „jerks,” „shakes,” or „spasms.” […] Myoclonic movements have many possible etiologies, anatomic sources, and pathophysiologic features. Myoclonus may be classified by clinical presentation, examination findings, clinical neurophysiology testing, and etiology. […] In addition to the clinical and etiologic classification discussed below, myoclonus can be classified by the localization of the physiologic mechanism that generates it. The categories are cortical, cortical-subcortical, subcortical-nonsegmental, segmental, and peripheral. […] This classification paradigm can help with localization of the underlying lesion, aid in the diagnosis of certain disorders that have a characteristic myoclonus physiology, and guide treatment options that may be useful for some physiologic types of myoclonus but not others.

• #5 Electrophysiologic Assessments of Involuntary Movements: Tremor and Myoclonus

  https://www.e-jmd.org/journal/view.php?doi=10.14802/jmd.09004

  Myoclonus is a quick, involuntary movement. […] Electrophysiological studies may helpful in the evaluation of myoclonus, not only for confirming the clinical diagnosis but also for understanding the underlying physiological mechanisms. […] Myoclonus can be classified in various ways, depending on which aspect is focused on but it is usually classified with the underlying physiologic mechanism or the causation. According to the pathophysiologic mechanisms, myoclonus is classified into three main categories; cortical, subcortical, and spinal. […] Cortical myoclonus is the most common form of myoclonus observed clinically. […] The physiologic characteristics of cortical myoclonus are 1) an associated EMG discharge of very short duration (usually less than 50 ms) 2) synchronous antagonists activity 3) EEG correlate 4) an EEG spike preceding the myoclonus by a short interval (20 ms in case of hand myoclonus) and localized the area of the contralateral central region corresponding to the involved muscle (around C3 and C4 in case of hand myoclonus) detected by back averaging technique, and 5) pathologic enlargement of early component of somatosensory evoked potentials (SEP), often accompanied by enhanced long-latency, long loop EMG discharge (C-reflex).

• #6 Myoclonus – Neurologic Disorders – Merck Manual Professional Edition

  https://www.merckmanuals.com/professional/neurologic-disorders/movement-and-cerebellar-disorders/myoclonus

  Myoclonus may be classified as physiologic (benign) or pathologic (1). […] Pathologic myoclonus can result from various disorders and medications (see table Some Causes of Myoclonus). The most common causes are Hypoxia, Medication toxicity, Metabolic disturbances. […] Other causes of pathologic myoclonus include degenerative disorders affecting the basal ganglia and some dementias. […] Myoclonus classified by site of origin is as follows: Cortical myoclonus is associated with cerebral cortex damage or epilepsy. […] Subcortical myoclonus is associated with disorders that affect the basal ganglia or other subcortical structures. […] The category of subcortical myoclonus includes essential myoclonus, myoclonus-dystonia (DYT11; associated with the SGCE gene), reticular reflex myoclonus, startle syndromes, Creutzfeldt-Jakob disease, and subacute sclerosing panencephalitis (1).

• #7 Classification and evaluation of myoclonus – UpToDate

  https://www.uptodate.com/contents/classification-and-evaluation-of-myoclonus

  Myoclonus is a clinical sign that is characterized by brief, shock-like, involuntary movements caused by muscular contractions or inhibitions. Muscular contractions produce positive myoclonus, whereas muscular inhibitions produce negative myoclonus (ie, asterixis). Patients will usually describe myoclonus as consisting of „jerks,” „shakes,” or „spasms.” […] Myoclonic movements have many possible etiologies, anatomic sources, and pathophysiologic features. Myoclonus may be classified by clinical presentation, examination findings, clinical neurophysiology testing, and etiology. […] In addition to the clinical and etiologic classification discussed below, myoclonus can be classified by the localization of the physiologic mechanism that generates it. The categories are cortical, cortical-subcortical, subcortical-nonsegmental, segmental, and peripheral. […] This classification paradigm can help with localization of the underlying lesion, aid in the diagnosis of certain disorders that have a characteristic myoclonus physiology, and guide treatment options that may be useful for some physiologic types of myoclonus but not others.

• #8

  https://journals.lww.com/annalsofian/fulltext/2021/24030/myoclonus__a_review.5.aspx

  The neurophysiological hallmark of cortical myoclonus is abnormal hyperexcitability of the sensorimotor cortex. […] Numerous other abnormalities including aberrations in serotoninergic and other neurotransmitter pathways and abnormal cerebello-thalamocortical activity (possibly due to Purkinje cell damage) have been proposed in the genesis of cortical myoclonus. […] It refers to myoclonus arising from paroxysmal abnormal excessive oscillation in reciprocal connections between cortical and subcortical sites, particularly the thalamus. […] The clinical and neurophysiological features of this subtype are more variable than those of cortical and cortical-subcortical subtypes due to multiple possible subcortical sites (between cortex and spinal cord), nuclei, and neuronal circuits from which a burst of excessive activity can originate and be transmitted through descending motor pathways.

• #9 Electrophysiologic Assessments of Involuntary Movements: Tremor and Myoclonus

  https://www.e-jmd.org/journal/view.php?doi=10.14802/jmd.09004

  Myoclonus is a quick, involuntary movement. […] Electrophysiological studies may helpful in the evaluation of myoclonus, not only for confirming the clinical diagnosis but also for understanding the underlying physiological mechanisms. […] Myoclonus can be classified in various ways, depending on which aspect is focused on but it is usually classified with the underlying physiologic mechanism or the causation. According to the pathophysiologic mechanisms, myoclonus is classified into three main categories; cortical, subcortical, and spinal. […] Cortical myoclonus is the most common form of myoclonus observed clinically. […] The physiologic characteristics of cortical myoclonus are 1) an associated EMG discharge of very short duration (usually less than 50 ms) 2) synchronous antagonists activity 3) EEG correlate 4) an EEG spike preceding the myoclonus by a short interval (20 ms in case of hand myoclonus) and localized the area of the contralateral central region corresponding to the involved muscle (around C3 and C4 in case of hand myoclonus) detected by back averaging technique, and 5) pathologic enlargement of early component of somatosensory evoked potentials (SEP), often accompanied by enhanced long-latency, long loop EMG discharge (C-reflex).

• #10 Electrophysiologic Assessments of Involuntary Movements: Tremor and Myoclonus

  https://www.e-jmd.org/journal/view.php?doi=10.14802/jmd.09004

  Myoclonus is a quick, involuntary movement. […] Electrophysiological studies may helpful in the evaluation of myoclonus, not only for confirming the clinical diagnosis but also for understanding the underlying physiological mechanisms. […] Myoclonus can be classified in various ways, depending on which aspect is focused on but it is usually classified with the underlying physiologic mechanism or the causation. According to the pathophysiologic mechanisms, myoclonus is classified into three main categories; cortical, subcortical, and spinal. […] Cortical myoclonus is the most common form of myoclonus observed clinically. […] The physiologic characteristics of cortical myoclonus are 1) an associated EMG discharge of very short duration (usually less than 50 ms) 2) synchronous antagonists activity 3) EEG correlate 4) an EEG spike preceding the myoclonus by a short interval (20 ms in case of hand myoclonus) and localized the area of the contralateral central region corresponding to the involved muscle (around C3 and C4 in case of hand myoclonus) detected by back averaging technique, and 5) pathologic enlargement of early component of somatosensory evoked potentials (SEP), often accompanied by enhanced long-latency, long loop EMG discharge (C-reflex).

• #11 Electrophysiologic Assessments of Involuntary Movements: Tremor and Myoclonus

  https://www.e-jmd.org/journal/view.php?number=93

  Myoclonus is a quick, involuntary movement. […] Electrophysiological studies may helpful in the evaluation of myoclonus, not only for confirming the clinical diagnosis but also for understanding the underlying physiological mechanisms. […] Myoclonus can be classified in various ways, depending on which aspect is focused on but it is usually classified with the underlying physiologic mechanism or the causation. According to the pathophysiologic mechanisms, myoclonus is classified into three main categories; cortical, subcortical, and spinal. […] Cortical myoclonus is the most common form of myoclonus observed clinically. […] The physiologic characteristics of cortical myoclonus are 1) an associated EMG discharge of very short duration (usually less than 50 ms) 2) synchronous antagonists activity 3) EEG correlate 4) an EEG spike preceding the myoclonus by a short interval (20 ms in case of hand myoclonus) and localized the area of the contralateral central region corresponding to the involved muscle (around C3 and C4 in case of hand myoclonus) detected by back averaging technique, and 5) pathologic enlargement of early component of somatosensory evoked potentials (SEP), often accompanied by enhanced long-latency, long loop EMG discharge (C-reflex).

• #12 Electrophysiologic Assessments of Involuntary Movements: Tremor and Myoclonus

  https://www.e-jmd.org/journal/view.php?doi=10.14802/jmd.09004

  Cortical myoclonus is often stimulus sensitive, with muscle stretch often being the critical stimulus. […] The anatomical origin of the myoclonus sometimes provides good hints as to the treatment. […] Segmental myoclonus is usually indicative of a focal structural lesion and its clinical features are rather distinctive. […] The electrophysiologic assessment of involuntary movements is not as widely used as traditional EMG tests. However, it can give some contributions to clinician to make a proper diagnosis and optimal management of involuntary movements.

• #13 Afferent mechanism of cortical myoclonus studied by proprioception-related SEPs

  https://www.periodicos.capes.gov.br/index.php/acervo/buscador.html?task=detalhes&id=W1964377266

  Proprioception-related somatosensory evoked potentials (SEPs) to passive flexion movement of the middle finger at proximal interphalangeal joint were recorded in 7 patients with myoclonus of cortical origin who demonstrated enlarged electrical SEPs (giant SEPs). […] Therefore, it is concluded that hyperexcitability of the sensorimotor cortex in cortical myoclonus is modality-specific. Cortical excitability is exaggerated to both cutaneous and deep receptor inputs in some patients, but only to cutaneous input in others.

• #14 Myoclonus – StatPearls – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/books/NBK537015/

  Myoclonus features diverse causes, anatomic diagnoses, and neurophysiologic presentations, all of which are nonspecific concerning their neuroanatomical source and pathogenesis. […] The specific etiologic mechanisms underlying myoclonus remain poorly understood. At present, researchers theorize that myoclonus may emerge as a consequence of motor strip hyperexcitability, abnormalities or deficiencies in neurotransmitter receptors, imbalances between neurotransmitters, or underlying network abnormalities that have yet to be elucidated. […] One of the chief classification schemes for the evaluation of myoclonus rests upon identifying the neuroanatomic generator of the myoclonus. Myoclonus can arise from loci in the cortex, cortico-subcortical regions (eg, brain stem), subcortical non-segmental overlap, segmental (brain stem or spinal cord), and the peripheral nerves. […] Researchers theorize that myoclonus may emerge due to motor strip hyperexcitability, abnormalities or deficiencies in neurotransmitter receptors, imbalances among neurotransmitters, or underlying network abnormalities that have yet to be elucidated.

• #15 Myoclonus – StatPearls – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/sites/books/NBK537015/

  Myoclonus can arise anywhere along the neuraxis, from the cerebral cortex to the peripheral nerves. Researchers theorize that myoclonus may emerge due to motor strip hyperexcitability, abnormalities or deficiencies in neurotransmitter receptors, imbalances among neurotransmitters, or underlying network abnormalities that have yet to be elucidated.

• #16 Myoclonus pathophysiology – wikidoc

  https://www.wikidoc.org/index.php/Myoclonus_pathophysiology

  Although some cases of myoclonus are caused by an injury to the peripheral nerves, most myoclonus is caused by a disturbance of the central nervous system. Studies suggest that several locations in the brain are involved in myoclonus. One such location, for example, is in the brainstem close to structures that are responsible for the startle response, an automatic reaction to an unexpected stimulus involving rapid muscle contraction. […] The specific mechanisms underlying myoclonus are not yet fully understood. Scientists believe that some types of stimulus-sensitive myoclonus may involve overexcitability of the parts of the brain that control movement. These parts are interconnected in a series of feedback loops called motor pathways. These pathways facilitate and modulate communication between the brain and muscles. Key elements of this communication are chemicals known as neurotransmitters, which carry messages from one nerve cell, or neuron, to another. Neurotransmitters are released by neurons and attach themselves to receptors on parts of neighboring cells. Some neurotransmitters may make the receiving cell more sensitive, while others tend to make the receiving cell less sensitive. Laboratory studies suggest that an imbalance between these chemicals may underlie myoclonus.

• #17 Myoclonus pathophysiology – wikidoc

  https://www.wikidoc.org/index.php/Myoclonus_pathophysiology

  Some researchers speculate that abnormalities or deficiencies in the receptors for certain neurotransmitters may contribute to some forms of myoclonus. Receptors that appear to be related to myoclonus include those for two important inhibitory neurotransmitters: serotonin, which constricts blood vessels and brings on sleep, and gamma-aminobutyric acid (GABA), which helps the brain maintain muscle control. Other receptors with links to myoclonus include those for opiates, drugs that induce sleep, and for glycine, an inhibitory neurotransmitter that is important for the control of motor and sensory functions in the spinal cord. More research is needed to determine how these receptor abnormalities cause or contribute to myoclonus.

• #18 Myoclonus | Baylor Medicine

  https://www.bcm.edu/healthcare/specialties/neurology/parkinsons-disease-and-movement-disorders/myoclonus

  Myoclonus is the medical term for sudden, rapid, brief, involuntary jerking movement of a body part or the entire body. […] These types of myoclonus may indicate that an underlying condition of the brain or nerves is causing the myoclonus. […] The specific mechanisms underlying myoclonus are not yet fully understood. Scientists believe that some types of stimulus-sensitive myoclonus may involve over excitability of the parts of the brain that control movement. […] Key elements of this communication are chemicals known as neurotransmitters, which carry messages from one nerve cell, or neuron, to another by binding to a receptor. Laboratory studies suggest that an imbalance between these chemicals may underlie myoclonus. Receptors that appear to be related to myoclonus include those for two important inhibitory neurotransmitters: serotonin, which constricts blood vessels and promotes sleep, and gamma-aminobutyric acid (GABA), which helps the brain maintain muscle control.

• #19 The Importance of Identifying Myoclonus in the Setting of Mental Status Abnormalities: Differential Diagnosis and Treatment

  https://www.psychiatrist.com/pcc/myoclonus-and-mental-status-abnormalities/

  The etiology of drug-induced myoclonus is poorly understood. However, it has been postulated that increased levels of serotonin may be etiologically responsible. […] The 2 neurotransmitter systems most frequently implicated in the pathophysiology of myoclonus are the serotonergic and -aminobutyric acid (GABA)-ergic systems.

• #20 Drug-Induced Myoclonus: A Systematic Review

  https://www.mdpi.com/1648-9144/61/1/131

  Myoclonus is already associated with a wide variety of drugs and systemic conditions. […] The neurotransmitters likely involved in DIM are serotonin, dopamine, gamma-aminobutyric acid (GABA), and glutamate. […] Based on the main clinical constellation of symptoms and pathophysiological mechanisms found in this study, DIM can be categorized into three types: type 1 (serotonin syndrome), type 2 (non-serotonin syndrome), and type 3 (unknown). […] The myoclonus caused by most medications cannot be hypothesized because the reports did not include electrodiagnostic studies. […] Increased serotonergic transmission may be the most commonly proposed pathophysiological mechanism for developing myoclonus. […] The neurotransmitters likely associated with DIM are serotonin, dopamine, GABA, and glutamate at various levels of the neuraxis.

• #21 Mechanism of Opsoclonus-Myoclonus Syndrome | Pediatric Neurology Briefs

  https://pediatricneurologybriefs.com/articles/10.15844/pedneurbriefs-9-3-5

  Cerebrospinal fluid measurements of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) and the dopamine metabolite homovanillic acid (HVA) in samples from 27 children with opsoclonus-myoclonus syndrome and 47 controls are reported from the National Pediatric Myoclonus Center, Childrens Research Institute, Washington, DC, and other centers. […] The etiology was paraneoplastic (46%) or infectious. EEGs were not epileptiform. Concentrations of 5-HIAA and HVA were 30-40% lower in patients compared to controls. Biochemical heterogeneity was evident since low CSF levels of 5-HIAA were not found in all patients with opsoclonus. […] Opsoclonus and myoclonus have been induced by various neurotransmitters and chemicals that alter serotonergic or noradrenergic mechanisms, eg. tricyclic antidepressants, and the chlorinated insecticides, chlordecone and DDT. Low CSF 5-HIAA levels have also been reported in patients with progressive myoclonus epilepsy of the Unverricht-Lundborg type, and other myoclonic disorders.

• #22

  https://journals.lww.com/co-neurology/fulltext/2018/08000/myoclonus_dystonia__classification,_phenomenology,.18.aspx

  The present study will highlight recent advances in the field of myoclonus-dystonia with a focus on clinical aspects, pathogenesis, and treatment. […] Accumulating evidence suggests that an alteration in cerebello-thalamic pathway function may play a prominent role and that this is possibly related to a GABAergic deficit reflecting Purkinje cell dysfunction. […] Impaired striatal plasticity and disturbed serotonin homeostasis may also be implicated. […] Newly available cellular and rodent models may further assist in investigating the pathogenesis of this disorder.

• #23 Familial Cortical Myoclonic Tremor and Epilepsy, an Enigmatic Disorder: From Phenotypes to Pathophysiology and Genetics. A Systematic Review | Tremor and Other Hyperkinetic Movements

  https://tremorjournal.org/articles/10.5334/tohm.434

  Cortical hyperexcitability can be considered the hallmark of FCMTE. […] Electrophysiological findings in FCMTE point to cortical hyperactivity and a cortical origin of the tremulous myoclonic movements. […] Transcranial magnetic stimulation (TMS) in European pedigrees revealed a reduction in short interval cortical inhibition compared with healthy controls, reflecting hyperexcitability of the cortex. […] In Japanese FCMTE patients the giant SEP was enhanced, lacking the long-term depression effect seen in healthy controls after quadripulse TMS over the primary motor cortex. […] However, post-mortem pathology studies in three Dutch cases revealed limited involvement of the sensorimotor cortex. […] Evidence for cerebellar involvement differs between FCMTE types. […] In FCMTE2 a proton magnetic resonance spectroscopy (MRS) study indicated cerebellar dysfunction.

• #24

  https://journals.lww.com/co-neurology/fulltext/2018/08000/myoclonus_dystonia__classification,_phenomenology,.18.aspx

  The present study will highlight recent advances in the field of myoclonus-dystonia with a focus on clinical aspects, pathogenesis, and treatment. […] Accumulating evidence suggests that an alteration in cerebello-thalamic pathway function may play a prominent role and that this is possibly related to a GABAergic deficit reflecting Purkinje cell dysfunction. […] Impaired striatal plasticity and disturbed serotonin homeostasis may also be implicated. […] Newly available cellular and rodent models may further assist in investigating the pathogenesis of this disorder.

• #25 Medical management of myoclonus-dystonia and implications for underlying pathophysiology -ORCA

  https://orca.cardiff.ac.uk/id/eprint/132633/

  Myoclonus-dystonia is an early onset genetic disorder characterised by subcortical myoclonus and less prominent dystonia. Its primary causative gene is the epsilonsarcoglycan gene but the syndrome of myoclonic dystonia has been shown to be a heterogeneous group of genetic disorders. The underlying pathophysiology of myoclonus-dystonia is incompletely understood, although it may relate to dysfunction of striatal monoamine neurotransmission or disruption of cerebellothalamic networks (possibly via a GABAergic deficit of Purkinje cells). […] We review the current evidence for pharmacological therapies in myoclonus-dystonia, discuss implications for underlying pathogenesis of the condition and propose a treatment algorithm for these patients.

• #26 Familial Cortical Myoclonic Tremor and Epilepsy, an Enigmatic Disorder: From Phenotypes to Pathophysiology and Genetics. A Systematic Review | Tremor and Other Hyperkinetic Movements

  https://tremorjournal.org/articles/10.5334/tohm.434

  Cortical hyperexcitability can be considered the hallmark of FCMTE. […] Electrophysiological findings in FCMTE point to cortical hyperactivity and a cortical origin of the tremulous myoclonic movements. […] Transcranial magnetic stimulation (TMS) in European pedigrees revealed a reduction in short interval cortical inhibition compared with healthy controls, reflecting hyperexcitability of the cortex. […] In Japanese FCMTE patients the giant SEP was enhanced, lacking the long-term depression effect seen in healthy controls after quadripulse TMS over the primary motor cortex. […] However, post-mortem pathology studies in three Dutch cases revealed limited involvement of the sensorimotor cortex. […] Evidence for cerebellar involvement differs between FCMTE types. […] In FCMTE2 a proton magnetic resonance spectroscopy (MRS) study indicated cerebellar dysfunction.

• #27 Familial Cortical Myoclonic Tremor and Epilepsy, an Enigmatic Disorder: From Phenotypes to Pathophysiology and Genetics. A Systematic Review | Tremor and Other Hyperkinetic Movements

  https://tremorjournal.org/articles/10.5334/tohm.434

  In the Dutch FCMTE3 pedigree, with a CTNND2 gene mutation several findings point to cerebellar changes. […] These include, in certain family members, a downbeat nystagmus upon hyperventilation and in three deceased cases there was Purkinje cell loss in the cerebellar cortex and abnormal morphology of Purkinje cells during pathological examination. […] In family members of these deceased Dutch patients a mutation was found in the CTNND2 gene that led to abnormal neuronal sprouting in mice neurons, resembling cerebellar pathology findings in the same Dutch pedigree. […] Pathology findings in three Dutch patients and one South African patient report severe loss of Purkinje cells with dendritic sprouts, neuronal loss in the dentate nucleus and microglia activation with limited changes in the sensorimotor cortex.

• #28 Familial Cortical Myoclonic Tremor and Epilepsy, an Enigmatic Disorder: From Phenotypes to Pathophysiology and Genetics. A Systematic Review | Tremor and Other Hyperkinetic Movements

  https://tremorjournal.org/articles/10.5334/tohm.434

  The cerebellar changes might lead to reduced cortical inhibition. […] Deficient stimulation of the dentate nucleus by Purkinje cells in the cerebellum may lead to increased cortical facilitation via the cerebello-thalamo-cortical loop, a hypothesis already raised for cortical myoclonus and epilepsy.

• #29

  https://journals.lww.com/annalsofian/fulltext/2021/24030/myoclonus__a_review.5.aspx

  The neurophysiological hallmark of cortical myoclonus is abnormal hyperexcitability of the sensorimotor cortex. […] Numerous other abnormalities including aberrations in serotoninergic and other neurotransmitter pathways and abnormal cerebello-thalamocortical activity (possibly due to Purkinje cell damage) have been proposed in the genesis of cortical myoclonus. […] It refers to myoclonus arising from paroxysmal abnormal excessive oscillation in reciprocal connections between cortical and subcortical sites, particularly the thalamus. […] The clinical and neurophysiological features of this subtype are more variable than those of cortical and cortical-subcortical subtypes due to multiple possible subcortical sites (between cortex and spinal cord), nuclei, and neuronal circuits from which a burst of excessive activity can originate and be transmitted through descending motor pathways.

• #30

  https://journals.lww.com/annalsofian/fulltext/2021/24030/myoclonus__a_review.5.aspx

  Brainstem reticular myoclonus is generated from the lower brainstem reticular formation in the medulla. […] The most striking clinical feature is sensitivity to multisensory stimuli, particularly auditory. […] The drug of choice for this subtype is valproic acid, particularly in juvenile myoclonic epilepsy. […] Standard antiepileptic drugs used in cortical myoclonus are not helpful in most types of subcortical-nonsegmental myoclonus. […] Both underlying etiology and the presumed physiology helps in establishing the best treatment strategy. […] More research is required into the mechanism of myoclonus generation, and this may lead to better pharmacological options.

• #31 :: JCN :: Journal of Clinical Neurology

  https://www.thejcn.com/DOIx.php?id=10.3988/jcn.2017.13.3.293

  Propriospinal myoclonus (PSM) is characterized by jerks arising in axial muscles that spread to more caudal and rostral segments along propriospinal pathways. […] Previous case reports have focused on the etiology and mechanism of PSM, but have not evaluated treatment responses objectively. […] Clonazepam enhances GABAergic neurotransmission by modulating benzodiazepine receptors and is most commonly used in patients with spinal myoclonus. […] Levetiracetam is mostly used to control cortical myoclonus, but it has also been reported to be effective in several patients with segmental spinal myoclonus. […] Its mechanism of action is thought to be related to modulation of glycine inhibitory neurotransmitters. […] In addition, levetiracetam may reduce excitation of the spinal generator by modulating Ca and K currents. […] The present case is the first to suggest that a combination of clonazepam and levetiracetam exerts synergistic effects in treating PSM at sleep onset.

• #32 Mechanism suppressing glycogen synthesis in neurons and its demise in progressive myoclonus epilepsy | Nature Neuroscience

  https://www.nature.com/articles/nn1998

  Glycogen synthesis is normally absent in neurons. However, inclusion bodies resembling abnormal glycogen accumulate in several neurological diseases, particularly in progressive myoclonus epilepsy or Lafora disease. […] This suppression was further ensured by a complex of laforin and malin, which are the two proteins whose mutations cause Lafora disease. […] Therefore, the malin-laforin complex ensures a blockade of neuronal glycogen synthesis even under intense glycogenic conditions. […] Here we explain the formation of polyglucosan inclusions in Lafora disease by demonstrating a crucial role for laforin and malin in glycogen synthesis.

• #33 Psychiatric phenotype in neurodevelopmental myoclonus-dystonia is underpinned by abnormality of cerebellar modulation on the cerebral cortex | Scientific Reports

  https://www.nature.com/articles/s41598-024-73386-9

  However, the SGCE protein is broadly expressed within the brain suggesting that, in addition to the motor networks, networks related to various non-motor functions may be affected in myoclonus-dystonia. […] Yet, through its connections with non-motor networks, the cerebellum is also involved in cognition and emotion regulation. […] The cerebellum serves as a convergence hub for these networks and influences the excitatory-inhibitory balance within the cortex, which is crucial for optimal processing of the neuronal information. […] Disruption of the posterior cerebellum can lead to cognitive and emotional impairment, together forming the cognitive and affective cerebellar syndrome. […] We hypothesized that connectivity within and among non-motor networks would be impaired in myoclonus-dystonia, potentially contributing to its non-motor phenotype, and that the cerebellum is involved in the reorganization of non-motor networks in myoclonus-dystonia.

• #34 The Importance of Identifying Myoclonus in the Setting of Mental Status Abnormalities: Differential Diagnosis and Treatment

  https://www.psychiatrist.com/pcc/myoclonus-and-mental-status-abnormalities/

  The etiology of drug-induced myoclonus is poorly understood. However, it has been postulated that increased levels of serotonin may be etiologically responsible. […] The 2 neurotransmitter systems most frequently implicated in the pathophysiology of myoclonus are the serotonergic and -aminobutyric acid (GABA)-ergic systems.

• #35 The Importance of Identifying Myoclonus in the Setting of Mental Status Abnormalities: Differential Diagnosis and Treatment

  https://www.psychiatrist.com/pcc/myoclonus-and-mental-status-abnormalities/

  Cortical-subcortical myoclonus refers to an abnormal bidirectional electrical oscillation between cortical and subcortical areas. […] Subcortical-supraspinal (nonsegmental) myoclonus is due to a discharge arising from a subcortical focus that can spread to pyramidal or extrapyramidal tracts. […] Spinal (segmental) myoclonus can refer to myoclonus that originates from the brain stem or the spinal cord. […] Peripheral myoclonus is also associated with a normal EEG; the EMG reveals variable burst duration. […] Several drugs (eg, antibiotics [quinolones, penicillins, and cephalosporins], antidepressants [particularly cyclic antidepressants, selective serotonin reuptake inhibitors, monoamine oxidase inhibitors, and lithium], benzodiazepines [eg, with benzodiazepine withdrawal], opiates, and dopamine agonists and dopamine blockers [neuroleptics], as well as cholinesterase inhibitors, antiepileptics, bismuth salts, general anesthetics, antiarrhythmics, calcium channel blockers, and others) have been associated with the onset of myoclonus.

• #36 Drug-Induced Myoclonus: A Systematic Review

  https://www.mdpi.com/1648-9144/61/1/131

  Myoclonus is already associated with a wide variety of drugs and systemic conditions. […] The neurotransmitters likely involved in DIM are serotonin, dopamine, gamma-aminobutyric acid (GABA), and glutamate. […] Based on the main clinical constellation of symptoms and pathophysiological mechanisms found in this study, DIM can be categorized into three types: type 1 (serotonin syndrome), type 2 (non-serotonin syndrome), and type 3 (unknown). […] The myoclonus caused by most medications cannot be hypothesized because the reports did not include electrodiagnostic studies. […] Increased serotonergic transmission may be the most commonly proposed pathophysiological mechanism for developing myoclonus. […] The neurotransmitters likely associated with DIM are serotonin, dopamine, GABA, and glutamate at various levels of the neuraxis.

• #37 Myoclonic Epilepsy Beginning in Infancy or Early Childhood: Background, Pathophysiology, Etiology

  https://emedicine.medscape.com/article/1176055-overview

  Myoclonic seizures are generally the product of hypersynchronous, generalized cortical discharges. These discharges arise from hyperexcitable neuronal networks. […] Across subtypes of childhood myoclonic epilepsy, many patients have an underlying genetic cause for their seizures. In some cases, myoclonic seizures may be a prominent feature of a syndrome with wider central nervous system and systemic manifestations, such as is seen in mitochondrial diseases (ie, MERRF or Alper syndrome [POLG1 mutations]). However, despite advances in identifying causes of epilepsy, for most cases of infantile and early childhood myoclonic epilepsy, no clear etiology will be found despite an appropriate workup.

• #38 Electrophysiologic Assessments of Involuntary Movements: Tremor and Myoclonus

  https://www.e-jmd.org/journal/view.php?number=93

  Cortical myoclonus can be considered as a fragment of focal epilepsy. […] Electrophysiologic assessment of involuntary movements is not as widely used as traditional EMG tests. However, it can give some contributions to clinician to make a proper diagnosis and optimal management of involuntary movements.

• #39 Myoclonic Epilepsy Beginning in Infancy or Early Childhood: Background, Pathophysiology, Etiology

  https://emedicine.medscape.com/article/1176055-overview

  Myoclonic seizures are generally the product of hypersynchronous, generalized cortical discharges. These discharges arise from hyperexcitable neuronal networks. […] Across subtypes of childhood myoclonic epilepsy, many patients have an underlying genetic cause for their seizures. In some cases, myoclonic seizures may be a prominent feature of a syndrome with wider central nervous system and systemic manifestations, such as is seen in mitochondrial diseases (ie, MERRF or Alper syndrome [POLG1 mutations]). However, despite advances in identifying causes of epilepsy, for most cases of infantile and early childhood myoclonic epilepsy, no clear etiology will be found despite an appropriate workup.

• #40 Electrophysiologic Assessments of Involuntary Movements: Tremor and Myoclonus

  https://www.e-jmd.org/journal/view.php?doi=10.14802/jmd.09004

  Myoclonus is a quick, involuntary movement. […] Electrophysiological studies may helpful in the evaluation of myoclonus, not only for confirming the clinical diagnosis but also for understanding the underlying physiological mechanisms. […] Myoclonus can be classified in various ways, depending on which aspect is focused on but it is usually classified with the underlying physiologic mechanism or the causation. According to the pathophysiologic mechanisms, myoclonus is classified into three main categories; cortical, subcortical, and spinal. […] Cortical myoclonus is the most common form of myoclonus observed clinically. […] The physiologic characteristics of cortical myoclonus are 1) an associated EMG discharge of very short duration (usually less than 50 ms) 2) synchronous antagonists activity 3) EEG correlate 4) an EEG spike preceding the myoclonus by a short interval (20 ms in case of hand myoclonus) and localized the area of the contralateral central region corresponding to the involved muscle (around C3 and C4 in case of hand myoclonus) detected by back averaging technique, and 5) pathologic enlargement of early component of somatosensory evoked potentials (SEP), often accompanied by enhanced long-latency, long loop EMG discharge (C-reflex).

• #41

  https://journals.lww.com/annalsofian/fulltext/2021/24030/myoclonus__a_review.5.aspx

  Myoclonus is a hyperkinetic movement disorder characterized by a sudden, brief, involuntary jerk. Positive myoclonus is caused by abrupt muscle contractions, while negative myoclonus by sudden cessation of ongoing muscular contractions. […] The neurophysiological classification of myoclonus by means of electrophysiological tests is helpful in guiding the best therapeutic strategy. […] The neurophysiological classification of myoclonus focuses on the pathophysiologic generator of myoclonus, and the mechanisms of propagation, regardless of its clinical presentation. […] A single disease can have myoclonus caused by different mechanisms. […] Identifying the physiological category also guides in deciding the most effective treatment, as drugs that are effective in cortical myoclonus may not be effective in other types of myoclonus.

• #42 Electrophysiological characteristics and anatomical differentiation of epileptic and non-epileptic myoclonus | The Egyptian Journal of Neurology, Psychiatry and Neurosurgery | Full Text

  https://ejnpn.springeropen.com/articles/10.1186/s41983-021-00374-5

  Electrophysiological techniques have been used for discriminating myoclonus from other hyperkinetic movement disorders and for classifying the myoclonus subtype. […] This study included 50 cases with myoclonus of different causes with mean age of 39.315.7 and consisted of 23 males and 27 females. […] There was a significant difference regarding the presence of EEG findings in epileptic myoclonic and non-epileptic myoclonic groups (P=0.005). […] Somatosensory evoked potential and electroencephalography are important for the diagnosis and anatomical sub-classification of myoclonus and so may help in decision-making regarding to the subsequent management. […] Myoclonus can be subdivided according to etiology into primary or secondary. […] Moreover, myoclonus can arise from several levels in the nervous system and can be subdivided by the anatomical origin into the following: cortical, subcortical, spinal, and peripheral myoclonus.

• #43 Electrophysiological characteristics and anatomical differentiation of epileptic and non-epileptic myoclonus | The Egyptian Journal of Neurology, Psychiatry and Neurosurgery | Full Text

  https://ejnpn.springeropen.com/articles/10.1186/s41983-021-00374-5

  The differentiation of myoclonic jerks from other hyperkinetic movement disorders sometimes may be difficult. […] Neurophysiologic studies aid in the confirmation and classification of clinical diagnoses as well as the understanding of underlying physiological mechanisms. […] Based on electro-diagnostic research, the anatomical categorization has been revised in recent years. […] Cortical myoclonus is the most common cause of positive electro-diagnostic criteria. […] Thus, a large somatosensory evoked response preceding the jerks may indicate a cortical myoclonus generator, whereas subcortical myoclonus lacks these traits. […] The aim of this study is to identify the electrophysiological characteristics and the anatomical classification of myoclonus of different causes. […] Our study showed statistically significant difference in SSEPs findings in different myoclonus subtypes according to anatomical classification and the control group regarding right and left amplitude of P24, N33, P24N33 peak-to-peak complex, all 3 subtypes showed enhancement of right and left amplitudes of P24, N33, P24N33 complex in comparison to control group where cortical myoclonus showed marked enhancement followed by subcortical myoclonus followed by corticalsubcortical myoclonus. […] This study demonstrated the importance of somatosensory evoked potential and electroencephalography in the diagnosis and anatomical sub-classification of myoclonus and so may be of great value for the decision-making regarding the subsequent management.

• #44 Electrophysiological characteristics and anatomical differentiation of epileptic and non-epileptic myoclonus | The Egyptian Journal of Neurology, Psychiatry and Neurosurgery | Full Text

  https://ejnpn.springeropen.com/articles/10.1186/s41983-021-00374-5

  The differentiation of myoclonic jerks from other hyperkinetic movement disorders sometimes may be difficult. […] Neurophysiologic studies aid in the confirmation and classification of clinical diagnoses as well as the understanding of underlying physiological mechanisms. […] Based on electro-diagnostic research, the anatomical categorization has been revised in recent years. […] Cortical myoclonus is the most common cause of positive electro-diagnostic criteria. […] Thus, a large somatosensory evoked response preceding the jerks may indicate a cortical myoclonus generator, whereas subcortical myoclonus lacks these traits. […] The aim of this study is to identify the electrophysiological characteristics and the anatomical classification of myoclonus of different causes. […] Our study showed statistically significant difference in SSEPs findings in different myoclonus subtypes according to anatomical classification and the control group regarding right and left amplitude of P24, N33, P24N33 peak-to-peak complex, all 3 subtypes showed enhancement of right and left amplitudes of P24, N33, P24N33 complex in comparison to control group where cortical myoclonus showed marked enhancement followed by subcortical myoclonus followed by corticalsubcortical myoclonus. […] This study demonstrated the importance of somatosensory evoked potential and electroencephalography in the diagnosis and anatomical sub-classification of myoclonus and so may be of great value for the decision-making regarding the subsequent management.

• #45 Electrophysiological characteristics and anatomical differentiation of epileptic and non-epileptic myoclonus | The Egyptian Journal of Neurology, Psychiatry and Neurosurgery | Full Text

  https://ejnpn.springeropen.com/articles/10.1186/s41983-021-00374-5

  The differentiation of myoclonic jerks from other hyperkinetic movement disorders sometimes may be difficult. […] Neurophysiologic studies aid in the confirmation and classification of clinical diagnoses as well as the understanding of underlying physiological mechanisms. […] Based on electro-diagnostic research, the anatomical categorization has been revised in recent years. […] Cortical myoclonus is the most common cause of positive electro-diagnostic criteria. […] Thus, a large somatosensory evoked response preceding the jerks may indicate a cortical myoclonus generator, whereas subcortical myoclonus lacks these traits. […] The aim of this study is to identify the electrophysiological characteristics and the anatomical classification of myoclonus of different causes. […] Our study showed statistically significant difference in SSEPs findings in different myoclonus subtypes according to anatomical classification and the control group regarding right and left amplitude of P24, N33, P24N33 peak-to-peak complex, all 3 subtypes showed enhancement of right and left amplitudes of P24, N33, P24N33 complex in comparison to control group where cortical myoclonus showed marked enhancement followed by subcortical myoclonus followed by corticalsubcortical myoclonus. […] This study demonstrated the importance of somatosensory evoked potential and electroencephalography in the diagnosis and anatomical sub-classification of myoclonus and so may be of great value for the decision-making regarding the subsequent management.

• #46 Treatment of myoclonus – UpToDate

  https://www.uptodate.com/contents/treatment-of-myoclonus

  Myoclonus is a sudden, involuntary, shock-like movement caused by sudden muscular contraction (positive myoclonus) or inhibition (negative myoclonus). Among movement disorder phenotypes, myoclonus is the most transient: it is essentially the quickest abnormal movement with a given body part. […] Myoclonic movements have many possible etiologies, and treatment is generally guided by the anatomic/physiologic type of myoclonus. Although there are some treatable underlying etiologies, myoclonus management is primarily symptomatic, and medications often have limited benefits. […] The clinical sign of myoclonus is uniform, but different distributions occur, and there are myriad etiologies and multiple anatomic/physiologic types. Both elements of classification help to guide therapy. […] Treat the underlying disorder — When the etiology of myoclonus is treatable or reversible, treatment of the underlying condition may partially or completely relieve the myoclonus. Examples include myoclonus caused by an acquired abnormal metabolic state (eg, hepatic failure), a removable medication or toxin (eg, selective serotonin reuptake inhibitors, opioids), an excisable lesion (eg, thoracic meningioma for spinal myoclonus), or functional jerks due to functional neurological symptom disorder (conversion disorder).

• #47 Myoclonus – Neurologic Disorders – Merck Manual Professional Edition

  https://www.merckmanuals.com/professional/neurologic-disorders/movement-and-cerebellar-disorders/myoclonus

  Classifying myoclonus based on site of origin is thought to be the most helpful when choosing the most effective treatment. […] Etiology of myoclonus may be essential (primary), acquired (most common), or idiopathic. […] Acquired myoclonus has multiple causes, including many metabolic disorders (see table Some Causes of Myoclonus). Most cases of myoclonus are acquired. […] Myoclonus may have a trigger or not: Myoclonus is triggered by a stimulus (eg, sudden noise, movement, light, visual threat), as can occur when a person is suddenly startled (startle response). […] Site of origin for myoclonus helps guide symptomatic treatment. For example, valproate, levetiracetam, and piracetam tend to be effective in cortical myoclonus but ineffective in other types of myoclonus. […] In the past, many types of myoclonus seemed to respond to the serotonin precursor 5-hydroxytryptophan, which was used with the oral decarboxylase inhibitor carbidopa, but 5-hydroxytryptophan is not used anymore because better medications are now available.

• #48

  https://journals.lww.com/annalsofian/fulltext/2021/24030/myoclonus__a_review.5.aspx

  Brainstem reticular myoclonus is generated from the lower brainstem reticular formation in the medulla. […] The most striking clinical feature is sensitivity to multisensory stimuli, particularly auditory. […] The drug of choice for this subtype is valproic acid, particularly in juvenile myoclonic epilepsy. […] Standard antiepileptic drugs used in cortical myoclonus are not helpful in most types of subcortical-nonsegmental myoclonus. […] Both underlying etiology and the presumed physiology helps in establishing the best treatment strategy. […] More research is required into the mechanism of myoclonus generation, and this may lead to better pharmacological options.

• #49 Myoclonus – Neurologic Disorders – Merck Manual Professional Edition

  https://www.merckmanuals.com/professional/neurologic-disorders/movement-and-cerebellar-disorders/myoclonus

  Classifying myoclonus based on site of origin is thought to be the most helpful when choosing the most effective treatment. […] Etiology of myoclonus may be essential (primary), acquired (most common), or idiopathic. […] Acquired myoclonus has multiple causes, including many metabolic disorders (see table Some Causes of Myoclonus). Most cases of myoclonus are acquired. […] Myoclonus may have a trigger or not: Myoclonus is triggered by a stimulus (eg, sudden noise, movement, light, visual threat), as can occur when a person is suddenly startled (startle response). […] Site of origin for myoclonus helps guide symptomatic treatment. For example, valproate, levetiracetam, and piracetam tend to be effective in cortical myoclonus but ineffective in other types of myoclonus. […] In the past, many types of myoclonus seemed to respond to the serotonin precursor 5-hydroxytryptophan, which was used with the oral decarboxylase inhibitor carbidopa, but 5-hydroxytryptophan is not used anymore because better medications are now available.

• #50 Myoclonus – Neurologic Disorders – Merck Manual Professional Edition

  https://www.merckmanuals.com/professional/neurologic-disorders/movement-and-cerebellar-disorders/myoclonus

  Classifying myoclonus based on site of origin is thought to be the most helpful when choosing the most effective treatment. […] Etiology of myoclonus may be essential (primary), acquired (most common), or idiopathic. […] Acquired myoclonus has multiple causes, including many metabolic disorders (see table Some Causes of Myoclonus). Most cases of myoclonus are acquired. […] Myoclonus may have a trigger or not: Myoclonus is triggered by a stimulus (eg, sudden noise, movement, light, visual threat), as can occur when a person is suddenly startled (startle response). […] Site of origin for myoclonus helps guide symptomatic treatment. For example, valproate, levetiracetam, and piracetam tend to be effective in cortical myoclonus but ineffective in other types of myoclonus. […] In the past, many types of myoclonus seemed to respond to the serotonin precursor 5-hydroxytryptophan, which was used with the oral decarboxylase inhibitor carbidopa, but 5-hydroxytryptophan is not used anymore because better medications are now available.

• #51 Treatment of myoclonus – UpToDate

  https://www.uptodate.com/contents/treatment-of-myoclonus

  Myoclonus is a sudden, involuntary, shock-like movement caused by sudden muscular contraction (positive myoclonus) or inhibition (negative myoclonus). Among movement disorder phenotypes, myoclonus is the most transient: it is essentially the quickest abnormal movement with a given body part. […] Myoclonic movements have many possible etiologies, and treatment is generally guided by the anatomic/physiologic type of myoclonus. Although there are some treatable underlying etiologies, myoclonus management is primarily symptomatic, and medications often have limited benefits. […] The clinical sign of myoclonus is uniform, but different distributions occur, and there are myriad etiologies and multiple anatomic/physiologic types. Both elements of classification help to guide therapy. […] Treat the underlying disorder — When the etiology of myoclonus is treatable or reversible, treatment of the underlying condition may partially or completely relieve the myoclonus. Examples include myoclonus caused by an acquired abnormal metabolic state (eg, hepatic failure), a removable medication or toxin (eg, selective serotonin reuptake inhibitors, opioids), an excisable lesion (eg, thoracic meningioma for spinal myoclonus), or functional jerks due to functional neurological symptom disorder (conversion disorder).

• #52 :: JCN :: Journal of Clinical Neurology

  https://www.thejcn.com/DOIx.php?id=10.3988/jcn.2017.13.3.293

  Propriospinal myoclonus (PSM) is characterized by jerks arising in axial muscles that spread to more caudal and rostral segments along propriospinal pathways. […] Previous case reports have focused on the etiology and mechanism of PSM, but have not evaluated treatment responses objectively. […] Clonazepam enhances GABAergic neurotransmission by modulating benzodiazepine receptors and is most commonly used in patients with spinal myoclonus. […] Levetiracetam is mostly used to control cortical myoclonus, but it has also been reported to be effective in several patients with segmental spinal myoclonus. […] Its mechanism of action is thought to be related to modulation of glycine inhibitory neurotransmitters. […] In addition, levetiracetam may reduce excitation of the spinal generator by modulating Ca and K currents. […] The present case is the first to suggest that a combination of clonazepam and levetiracetam exerts synergistic effects in treating PSM at sleep onset.

• #53 :: JCN :: Journal of Clinical Neurology

  https://www.thejcn.com/DOIx.php?id=10.3988/jcn.2017.13.3.293

  Propriospinal myoclonus (PSM) is characterized by jerks arising in axial muscles that spread to more caudal and rostral segments along propriospinal pathways. […] Previous case reports have focused on the etiology and mechanism of PSM, but have not evaluated treatment responses objectively. […] Clonazepam enhances GABAergic neurotransmission by modulating benzodiazepine receptors and is most commonly used in patients with spinal myoclonus. […] Levetiracetam is mostly used to control cortical myoclonus, but it has also been reported to be effective in several patients with segmental spinal myoclonus. […] Its mechanism of action is thought to be related to modulation of glycine inhibitory neurotransmitters. […] In addition, levetiracetam may reduce excitation of the spinal generator by modulating Ca and K currents. […] The present case is the first to suggest that a combination of clonazepam and levetiracetam exerts synergistic effects in treating PSM at sleep onset.

• #54 Myoclonus – StatPearls – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/books/NBK537015/

  Myoclonus features diverse causes, anatomic diagnoses, and neurophysiologic presentations, all of which are nonspecific concerning their neuroanatomical source and pathogenesis. […] The specific etiologic mechanisms underlying myoclonus remain poorly understood. At present, researchers theorize that myoclonus may emerge as a consequence of motor strip hyperexcitability, abnormalities or deficiencies in neurotransmitter receptors, imbalances between neurotransmitters, or underlying network abnormalities that have yet to be elucidated. […] One of the chief classification schemes for the evaluation of myoclonus rests upon identifying the neuroanatomic generator of the myoclonus. Myoclonus can arise from loci in the cortex, cortico-subcortical regions (eg, brain stem), subcortical non-segmental overlap, segmental (brain stem or spinal cord), and the peripheral nerves. […] Researchers theorize that myoclonus may emerge due to motor strip hyperexcitability, abnormalities or deficiencies in neurotransmitter receptors, imbalances among neurotransmitters, or underlying network abnormalities that have yet to be elucidated.

• #55 Myoclonus pathophysiology – wikidoc

  https://www.wikidoc.org/index.php/Myoclonus_pathophysiology

  Although some cases of myoclonus are caused by an injury to the peripheral nerves, most myoclonus is caused by a disturbance of the central nervous system. Studies suggest that several locations in the brain are involved in myoclonus. One such location, for example, is in the brainstem close to structures that are responsible for the startle response, an automatic reaction to an unexpected stimulus involving rapid muscle contraction. […] The specific mechanisms underlying myoclonus are not yet fully understood. Scientists believe that some types of stimulus-sensitive myoclonus may involve overexcitability of the parts of the brain that control movement. These parts are interconnected in a series of feedback loops called motor pathways. These pathways facilitate and modulate communication between the brain and muscles. Key elements of this communication are chemicals known as neurotransmitters, which carry messages from one nerve cell, or neuron, to another. Neurotransmitters are released by neurons and attach themselves to receptors on parts of neighboring cells. Some neurotransmitters may make the receiving cell more sensitive, while others tend to make the receiving cell less sensitive. Laboratory studies suggest that an imbalance between these chemicals may underlie myoclonus.

• #56 Electrophysiologic Assessments of Involuntary Movements: Tremor and Myoclonus

  https://www.e-jmd.org/journal/view.php?doi=10.14802/jmd.09004

  Myoclonus is a quick, involuntary movement. […] Electrophysiological studies may helpful in the evaluation of myoclonus, not only for confirming the clinical diagnosis but also for understanding the underlying physiological mechanisms. […] Myoclonus can be classified in various ways, depending on which aspect is focused on but it is usually classified with the underlying physiologic mechanism or the causation. According to the pathophysiologic mechanisms, myoclonus is classified into three main categories; cortical, subcortical, and spinal. […] Cortical myoclonus is the most common form of myoclonus observed clinically. […] The physiologic characteristics of cortical myoclonus are 1) an associated EMG discharge of very short duration (usually less than 50 ms) 2) synchronous antagonists activity 3) EEG correlate 4) an EEG spike preceding the myoclonus by a short interval (20 ms in case of hand myoclonus) and localized the area of the contralateral central region corresponding to the involved muscle (around C3 and C4 in case of hand myoclonus) detected by back averaging technique, and 5) pathologic enlargement of early component of somatosensory evoked potentials (SEP), often accompanied by enhanced long-latency, long loop EMG discharge (C-reflex).

• #57 Electrophysiologic Assessments of Involuntary Movements: Tremor and Myoclonus

  https://www.e-jmd.org/journal/view.php?number=93

  Myoclonus is a quick, involuntary movement. […] Electrophysiological studies may helpful in the evaluation of myoclonus, not only for confirming the clinical diagnosis but also for understanding the underlying physiological mechanisms. […] Myoclonus can be classified in various ways, depending on which aspect is focused on but it is usually classified with the underlying physiologic mechanism or the causation. According to the pathophysiologic mechanisms, myoclonus is classified into three main categories; cortical, subcortical, and spinal. […] Cortical myoclonus is the most common form of myoclonus observed clinically. […] The physiologic characteristics of cortical myoclonus are 1) an associated EMG discharge of very short duration (usually less than 50 ms) 2) synchronous antagonists activity 3) EEG correlate 4) an EEG spike preceding the myoclonus by a short interval (20 ms in case of hand myoclonus) and localized the area of the contralateral central region corresponding to the involved muscle (around C3 and C4 in case of hand myoclonus) detected by back averaging technique, and 5) pathologic enlargement of early component of somatosensory evoked potentials (SEP), often accompanied by enhanced long-latency, long loop EMG discharge (C-reflex).

• #58

  https://journals.lww.com/co-neurology/fulltext/2018/08000/myoclonus_dystonia__classification,_phenomenology,.18.aspx

  The present study will highlight recent advances in the field of myoclonus-dystonia with a focus on clinical aspects, pathogenesis, and treatment. […] Accumulating evidence suggests that an alteration in cerebello-thalamic pathway function may play a prominent role and that this is possibly related to a GABAergic deficit reflecting Purkinje cell dysfunction. […] Impaired striatal plasticity and disturbed serotonin homeostasis may also be implicated. […] Newly available cellular and rodent models may further assist in investigating the pathogenesis of this disorder.

• #59

  https://journals.lww.com/annalsofian/fulltext/2021/24030/myoclonus__a_review.5.aspx

  Brainstem reticular myoclonus is generated from the lower brainstem reticular formation in the medulla. […] The most striking clinical feature is sensitivity to multisensory stimuli, particularly auditory. […] The drug of choice for this subtype is valproic acid, particularly in juvenile myoclonic epilepsy. […] Standard antiepileptic drugs used in cortical myoclonus are not helpful in most types of subcortical-nonsegmental myoclonus. […] Both underlying etiology and the presumed physiology helps in establishing the best treatment strategy. […] More research is required into the mechanism of myoclonus generation, and this may lead to better pharmacological options.

• #60

  https://journals.lww.com/annalsofian/fulltext/2021/24030/myoclonus__a_review.5.aspx

  Brainstem reticular myoclonus is generated from the lower brainstem reticular formation in the medulla. […] The most striking clinical feature is sensitivity to multisensory stimuli, particularly auditory. […] The drug of choice for this subtype is valproic acid, particularly in juvenile myoclonic epilepsy. […] Standard antiepileptic drugs used in cortical myoclonus are not helpful in most types of subcortical-nonsegmental myoclonus. […] Both underlying etiology and the presumed physiology helps in establishing the best treatment strategy. […] More research is required into the mechanism of myoclonus generation, and this may lead to better pharmacological options.

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