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Myoclonus

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Movement disorders

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Myoclonus

  1. 1. Myoclonus Dr. Sachin Adukia
  2. 2.  Myoclonus is a clinical sign that is characterized by brief, shocklike, involuntary movements caused by muscular contractions or inhibitions [1].  Muscular contractions produce positive myoclonus,  muscular inhibitions produce negative myoclonus (ie, asterixis).  Patients will usually describe myoclonus as consisting of "jerks," "shakes," or "spasms."
  3. 3. ANATOMIC AND PHYSIOLOGIC CLASSIFICATION  classified by the localization of the physiologic mechanism that generates it  Cortical  Cortical-subcortical  Subcortical-nonsegmental  Segmental  Peripheral
  4. 4. Cortical  focal discharge from the primary sensorimotor cortex causes myoclonic jerk  Occurs because of insufficient inhibition within neuronal circuits of the primary motor cortex, primary sensory cortex, or both  Rapid generalization - can produce myoclonic seizures in certain epileptic syndromes  may occur with  reflex sensory stimulation (cortical reflex myoclonus),  Muscle activation (cortical action myoclonus),  with rest (eg, focal motor seizure),  or any combination
  5. 5. Cortical-subcortical  involves abnormal, paroxysmal, and excessive oscillation in bidirectional connections between cortical and subcortical sites.  is the major mechanism for myoclonic seizures in primary generalized epileptic syndromes (JME) and others (eg, minipolymyoclonus).  Eg: in JME and absence epilepsy, thalamic networks abnormally couple with widespread cortical areas to produce excessive neuronal activity  The resulting myoclonic jerks are commonly generalized or bisynchronous.
  6. 6. Subcortical-nonsegmental  myoclonus is generated from a site that is subcortical, but myoclonus manifests far beyond segments that are near the originating site.  Eg. reticular-reflex myoclonus and propriospinal  abnormal activity begins in a focal area of neuraxis and then spreads in both rostral and caudal directions, producing generalized myoclonus
  7. 7. Segmental myoclonus  generated at a particular segment or contiguous segments of brainstem and/or spinal cord.  Freq. of motor oscillations < tremor.  manifests at, or close to, that particular segment or contiguous segments of the body  palatal myoclonus  spinal segmental myoclonus
  8. 8. Peripheral myoclonus  arises d/t peripheral nervous system lesion  produces hyperactive motor discharges to its muscle (eg, hemifacial spasm).
  9. 9. Anatomic and physiologic classification
  10. 10. CLINICAL AND ETIOLOGIC CLASSIFICATION  classification scheme of Marsden and colleagues ● Physiologic ● Essential ● Epileptic ● Secondary (symptomatic)
  11. 11. Physiological: Jerks associated with sleep  occur during sleep or sleep transitions  Partial myoclonic jerks – multifocal, s/i distal muscles  Massive myoclonic jerks – hypnic- gen., affect trunk and proximal muscles  Periodic movements of sleep (nocturnal myoclonus) are stereotyped repetitive dorsiflexion of toes and feet, sometimes with flexion of knees and hips
  12. 12. Essential myoclonus- divided into sporadic and hereditary  myoclonus is the most prominent or only clinical finding - ie, an "essential" phenomenon  Sporadic (or idiopathic) essential myoclonus - heterogeneous w.r.t. distribution, exacerbating factors, CNS findings  Palatal myoclonus  often 2o to brainstem and/or cerebellar lesion.  However, some patients have no apparent structural lesion - essential palatal myoclonus.  myoclonus is c/b contractions of the tensor veli palatini  secondary (symptomatic) c/b contractions of levator veli palatini.
  13. 13. Hereditary essential myoclonus  demonstrates a subcortical-nonsegmental physiology  Clinical features  Onset < 20 yrs  AD  benign course - active life and normal lifespan  Absence of cerebellar ataxia, spasticity, dementia, and seizures  occurs throughout arms & axial muscles.  exacerbated by muscle activation  markedly diminished with alcohol ingestion.
  14. 14. Epileptic myoclonus  Is myoclonus in the setting of epilepsy  cortical or cortical-subcortical physiology  Seizures dominate the clinical picture  idiopathic, genetic, or a static encephalopathy  Myoclonus can occur as  one of several components of a seizure  the only seizure manifestation - myoclonic seizure  one of multiple seizure types within an epileptic syndrome
  15. 15. Familial cortical myoclonic tremor with epilepsy  Autosomal dominant inheritance  Adult onset  Distal action tremor and myoclonus  Infrequent, 2o GTCS  Relatively benign course, typically normal cognition  Responsiveness to anticonvulsants
  16. 16. Symptomatic (secondary) myoclonus  occurs as a secondary symptom of neurologic or non- neurologic disorder
  17. 17. Part three
  18. 18. Treatment  to control myoclonus - treat the underlying disorder  may reverse certain myoclonus  myoclonus caused by an acquired abnormal metabolic state  medication or toxin  excisable lesion  psychogenic etiology  Evidence base for treatment is mainly of observational case series and case reports
  19. 19. Cortical myoclonus  Drug treatment – aim is to augment inhibitory processes within sensorimotor cortex  Levetiracetam, piracetam- initial drugs  clonazepam and valproic acid – add on’s  Gait disturbance - most resistant to treatment.  An unsteady gait with frequent falls may persist despite control of action and reflex myoclonus in UL  Also, there is no consistent evidence for benefit in negative myoclonus (asterixis).
  20. 20. Cortical-subcortical myoclonus  Includes the myoclonus in PGE  Treatment is that of epilepsy
  21. 21. Subcortical-nonsegmental myoclonus  Standard antiepileptic treatments- not helpful  In addition, increased risk of alcoholism in patients with essential myoclonus (including myoclonus-dystonia) because condition is ethanol-responsive.  initial treatment with clonazepam  Benztropine or trihexyphenidyl – alternatives for initial or add- on therapy in essential myoclonus, including myoclonus- dystonia  Zonisamide- propriospinal myoclonus.
  22. 22. Segmental myoclonus  Spinal Myoclonus  clonazepam (up to 6 mg daily)  However, benefit - limited.  Alternatives- levetiracetam, botulinum toxin injection, carbamazepine, diazepam, and tetrabenazine.  Palatal myoclonus –  botulinum toxin injections as initial treatment for debilitating palatal myoclonus  pharmacologic interventions- no benefit  possibly useful drugs :  clonazepam, piracetam, valproic acid, baclofen, carbamazepine, lamotrigine, phenytoin, sumatriptan, and tetrabenazine.
  23. 23. Peripheral myoclonus  botulinum toxin injection hemifacial spasm and other peripheral myoclonus  carbamazepine may have some effect.
  24. 24. Thank You

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