Myoclonus: Difference between revisions
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== Clinically Relevant Anatomy | == Clinically Relevant Anatomy == | ||
Myoclonus is sudden, brief, jerky, shock-like, involuntary movements arising from the central nervous system and involving extremities, face, and trunk. <ref>Fahn S, Marsden CD, Van Woert MH. Definition and classification of myoclonus. Adv Neurol. 1986;43:1–5.</ref> | |||
= | According to the pathophysiologic mechanisms, myoclonus is classified into three main categories; cortical, subcortical, and spinal. Among these three categories, cortical myoclonus is most commonly encountered. <ref name=":0">Park HD, Kim HT. Electrophysiologic assessments of involuntary movements: tremor and myoclonus. ''J Mov Disord''. 2009;2(1):14–17. doi:10.14802/jmd.09004</ref> | ||
==== Cortical myoclonus ==== | |||
Cortical myoclonus arises from a hyperexcitable focus within the sensory-motor cortex. It typically involves an arm, leg or the face and is triggered by action of intention. | |||
==== Negative (Asterixis) myoclonus ==== | |||
Negative or asterixis myoclonus occurs when a muscle contraction is suddenly interrupted and can be seen in either cortical or subcortical lesions. It is usually associated with metabolic or toxic encephalopathy,<ref>Shibasaki H. Pathophysiology of negative myoclonus and asterixis. Adv Neurol. 1995;67:199–209.</ref> but unilateral asterixis myoclonus can be seen in patients with ischemic or hemorrhagic disorders, especially those involving the thalamus.<ref>Río J, Montalbán J, Pujadas F, Alvarez-Sabín J, Rovira A, Codina A. Asterixis associated with anatomic cerebral lesions: a study of 45 cases. Acta Neurol Scand. 1995;91:377–381</ref> | |||
<br> | |||
== Mechanism of Injury / Pathological Process == | |||
Cortical myoclonus is not disease-specific. It is most commonly seen in a group of diseases such as progressive myoclonic epilepsy (PME), and also seen in other diseases, including juvenile myoclonic epilepsy, postanoxic myoclonus,<ref>Obeso JA, Rothwell JC, Marsden CD. The spectrum of cortical myoclonus. From focal reflex jerks to spontaneous motor epilepsy. Brain. 1985;108:193–224.</ref> corticobasal degeneration,<ref>Brunt ER, van Weerden TW, Pruim J, Lakke JW. Unique myoclonic pattern in corticobasal degeneration. Mov Disord. 1995;10:132–142.</ref> Alzheimer’s disease,<ref>Wilkins DE, Hallett M, Berardelli A, Walshe T, Alvarez N. Physiologic analysis of the myoclonus of Alzheimer’s disease. Neurology. 1984;34:898–903</ref> olivopontocerebellar atrophy, advanced Creuzfeldt-Jakob disease, metabolic encephalopathy, Rett syndrome,<ref>Guerrini R, Bonanni P, Parmeggiani L, Santucci M, Parmeggiani A, Sartucci F. Cortical reflex myoclonus in Rett syndrome. Ann Neurol. 1998;43:472–479.</ref> and celiac disease. <ref name=":0" /><br> | |||
== Clinical Presentation == | == Clinical Presentation == | ||
Myoclonus can be described as action myoclonus (activated by voluntary movement), reflex myoclonus (activated by sensory stimulation). <ref name=":0" /> | |||
Rhythmic segmental myoclonus and brainstem (palatal) myoclonus persisted during sleep. Myoclonic jerks usually represent brief muscle contractions (positive myoclonus) but may also be produced by equally brief lapses of muscle contraction (negative myoclonus or asterixis). In other words, positive myoclonus jerks originate from rapid, active contractions of a muscle or group of muscles. <ref name=":0" /> | |||
The physiologic characteristics of cortical myoclonus are: | |||
1) an associated EMG discharge of very short duration (usually less than 50 ms) | |||
2) an EEG spike preceding the myoclonus. A short interval (20 ms in case of hand myoclonus) and localised to 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. <ref>Shibasaki H, Kuroiwa Y. Electroencephalographic correlates of myoclonus. Electroencephalogr Clin Neurophysiol. 1975;39:455–463.</ref> | |||
== Diagnostic Procedures == | == Diagnostic Procedures == | ||
Myoclonus is distinguished from tics because the latter can be controlled by an effort of will, at least temporarily, whereas myoclonus cannot.<ref name=":0" /> | |||
== Outcome Measures == | == Outcome Measures == | ||
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add links to outcome measures here (see [[Outcome Measures|Outcome Measures Database]]) | add links to outcome measures here (see [[Outcome Measures|Outcome Measures Database]]) | ||
== Management / Interventions | == Management / Interventions == | ||
add text here relating to management approaches to the condition<br> | add text here relating to management approaches to the condition<br> | ||
== Differential Diagnosis | == Differential Diagnosis == | ||
Rhythmic myoclonus may be confused with tremor. Its frequency is often slower than the commonly observed tremors, it is present at rest, is not modified significantly by voluntary movements and often persists during sleep. <ref name=":0" /> | |||
= | Myoclonus may also be confused with chorea, especially if multifocal and asynchronous, but in chorea the movements continue in a constant flow, randomly distributed over the body and randomly distributed in time. <ref name=":0" /><br> | ||
== Resources == | |||
== References == | == References == | ||
<references /> | <references /> | ||
Revision as of 22:47, 12 February 2020
Original Editor - Your name will be added here if you created the original content for this page.
Lead Editors
Clinically Relevant Anatomy[edit | edit source]
Myoclonus is sudden, brief, jerky, shock-like, involuntary movements arising from the central nervous system and involving extremities, face, and trunk. [1]
According to the pathophysiologic mechanisms, myoclonus is classified into three main categories; cortical, subcortical, and spinal. Among these three categories, cortical myoclonus is most commonly encountered. [2]
Cortical myoclonus[edit | edit source]
Cortical myoclonus arises from a hyperexcitable focus within the sensory-motor cortex. It typically involves an arm, leg or the face and is triggered by action of intention.
Negative (Asterixis) myoclonus[edit | edit source]
Negative or asterixis myoclonus occurs when a muscle contraction is suddenly interrupted and can be seen in either cortical or subcortical lesions. It is usually associated with metabolic or toxic encephalopathy,[3] but unilateral asterixis myoclonus can be seen in patients with ischemic or hemorrhagic disorders, especially those involving the thalamus.[4]
Mechanism of Injury / Pathological Process[edit | edit source]
Cortical myoclonus is not disease-specific. It is most commonly seen in a group of diseases such as progressive myoclonic epilepsy (PME), and also seen in other diseases, including juvenile myoclonic epilepsy, postanoxic myoclonus,[5] corticobasal degeneration,[6] Alzheimer’s disease,[7] olivopontocerebellar atrophy, advanced Creuzfeldt-Jakob disease, metabolic encephalopathy, Rett syndrome,[8] and celiac disease. [2]
Clinical Presentation[edit | edit source]
Myoclonus can be described as action myoclonus (activated by voluntary movement), reflex myoclonus (activated by sensory stimulation). [2]
Rhythmic segmental myoclonus and brainstem (palatal) myoclonus persisted during sleep. Myoclonic jerks usually represent brief muscle contractions (positive myoclonus) but may also be produced by equally brief lapses of muscle contraction (negative myoclonus or asterixis). In other words, positive myoclonus jerks originate from rapid, active contractions of a muscle or group of muscles. [2]
The physiologic characteristics of cortical myoclonus are:
1) an associated EMG discharge of very short duration (usually less than 50 ms)
2) an EEG spike preceding the myoclonus. A short interval (20 ms in case of hand myoclonus) and localised to 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. [9]
Diagnostic Procedures[edit | edit source]
Myoclonus is distinguished from tics because the latter can be controlled by an effort of will, at least temporarily, whereas myoclonus cannot.[2]
Outcome Measures[edit | edit source]
add links to outcome measures here (see Outcome Measures Database)
Management / Interventions[edit | edit source]
add text here relating to management approaches to the condition
Differential Diagnosis[edit | edit source]
Rhythmic myoclonus may be confused with tremor. Its frequency is often slower than the commonly observed tremors, it is present at rest, is not modified significantly by voluntary movements and often persists during sleep. [2]
Myoclonus may also be confused with chorea, especially if multifocal and asynchronous, but in chorea the movements continue in a constant flow, randomly distributed over the body and randomly distributed in time. [2]
Resources[edit | edit source]
References[edit | edit source]
- ↑ Fahn S, Marsden CD, Van Woert MH. Definition and classification of myoclonus. Adv Neurol. 1986;43:1–5.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Park HD, Kim HT. Electrophysiologic assessments of involuntary movements: tremor and myoclonus. J Mov Disord. 2009;2(1):14–17. doi:10.14802/jmd.09004
- ↑ Shibasaki H. Pathophysiology of negative myoclonus and asterixis. Adv Neurol. 1995;67:199–209.
- ↑ Río J, Montalbán J, Pujadas F, Alvarez-Sabín J, Rovira A, Codina A. Asterixis associated with anatomic cerebral lesions: a study of 45 cases. Acta Neurol Scand. 1995;91:377–381
- ↑ Obeso JA, Rothwell JC, Marsden CD. The spectrum of cortical myoclonus. From focal reflex jerks to spontaneous motor epilepsy. Brain. 1985;108:193–224.
- ↑ Brunt ER, van Weerden TW, Pruim J, Lakke JW. Unique myoclonic pattern in corticobasal degeneration. Mov Disord. 1995;10:132–142.
- ↑ Wilkins DE, Hallett M, Berardelli A, Walshe T, Alvarez N. Physiologic analysis of the myoclonus of Alzheimer’s disease. Neurology. 1984;34:898–903
- ↑ Guerrini R, Bonanni P, Parmeggiani L, Santucci M, Parmeggiani A, Sartucci F. Cortical reflex myoclonus in Rett syndrome. Ann Neurol. 1998;43:472–479.
- ↑ Shibasaki H, Kuroiwa Y. Electroencephalographic correlates of myoclonus. Electroencephalogr Clin Neurophysiol. 1975;39:455–463.
