Approach myoclonus

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  • myoclonic (rapid shocklike contractions, usually <50 msec in duration, that may be isolated or may repeat but usually are not rhythmic)
  • 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."
  • Partial myoclonic jerks are usually multifocal and occur in distal musclesMassive myoclonic jerks are generalized and affect trunk and proximal musclesPeriodic movements of sleep (nocturnal myoclonus) consist of stereotyped repetitive dorsiflexion of the toes and feet, sometimes with flexion of the knees and hips . The same types of movements occur in the restless legs syndrome and can disrupt sleep . Some authors maintain that nocturnal myoclonus is too slow and prolonged to be classified as myoclonus, and that periodic movements of sleep is the preferred term
  • Hereditary essential myoclonus — Hereditary essential myoclonus has the following clinical characteristics :Onset typically before age 20 yearsAutosomal dominant inheritance with variable expressivityA benign course compatible with an active life and normal lifespanAbsence of cerebellar ataxia, spasticity, dementia, and seizures
  • Ohtahara syndrome usually presents within the first 10 days of life but may present as late as 3 months. The seizures are typically numerous brief tonic spasms (and not clonic or fragmentary myoclonic). In contrast to the metabolic causes of NME, the causes of Ohtahara syndrome tend to be structural, with most being dysgenetic or, occasionally, destructive, such as hypoxic-ischemic injury.
  • hypsarrhythmia is a high-voltage, slow, chaotic background with multifocal spikes.
  • The initial ACTH dose in one high-dose protocol is 150 IU/m2/day of ACTH gel intramuscularly in 2 divided doses for 1 wk. During the 2nd wk, the dose is 75 IU/m2/day in 1 daily dose for 1 wk. For the 3rd wk, the dose is 75 IU/m2 every other day for 1 wk. ACTH is gradually tapered over the next 9 wk. Cryptogenic cases have a better chance for a response.
  • Approach myoclonus

    1. 1. Approach to Myoclonic seizures in Childhood
    2. 2. Myoclonus • Myoclonus is a brief, involuntary muscle contraction (jerk) that may represent • (1) a seizure manifestation, as in infantile spasms; • (2) a physiological response to startle or to falling asleep; or • (3) an involuntary movement either alone or in combination with tonic-clonic seizures
    3. 3. CLINICAL AND ETIOLOGIC CLASSIFICATION • Marsden and colleagues • Physiologic • Essential • Epileptic • Secondary (symptomatic)
    4. 4. Physiologic myoclonus (normal subjects) • A. Sleep jerks (eg, hypnic jerks) • B. Anxiety-induced • C. Exercise-induced • D. Hiccough (singultus) • E. Benign infantile myoclonus with feeding
    5. 5. Essential myoclonus (primary symptom, nonprogressive history) • A. Hereditary (autosomal dominant) • B. Sporadic
    6. 6. Epileptic myoclonus • Fragments of epilepsy • Myoclonic epilepsy syndromes • Familial cortical myoclonic tremor with epilepsy
    7. 7. Fragments of epilepsy • Isolated epileptic myoclonic jerks • Epilepsia partialis continua (focal status epilepticus) • Idiopathic stimulus-sensitive myoclonus • Photosensitive myoclonus • Absences with a minor myoclonic component • Epilepsy with myoclonic absences
    8. 8. Myoclonic epilepsy syndromes • Infantile spasms (West syndrome) • Severe myoclonic epilepsy of infancy (Dravet syndrome) • Benign myoclonic epilepsy of infancy • Lennox-Gastaut syndrome • Myoclonic astatic epilepsy (Doose syndrome) • Cryptogenic myoclonus epilepsy (Aicardi) • Juvenile myoclonic epilepsy (Janz syndrome) • Familial cortical myoclonic tremor with epilepsy
    9. 9. Familial cortical myoclonic tremor with epilepsy • Autosomal dominant inheritance • Adult onset • Distal action tremor and myoclonus • Infrequent, secondarily generalized tonic- clonic seizures • Relatively benign course, typically with normal cognition • Responsiveness to anticonvulsants.
    10. 10. Symptomatic (secondary) myoclonus • Post–central nervous system injury • Basal ganglia degenerations • Drug-induced • Storage disorders • Viral encephalitis
    11. 11. Early infantile epileptic encephalopathies • Early myoclonic infantile encephalopathy • Early epileptic infantile encephalopathy (Ohtahara syndrome)
    12. 12. Epilepsy syndromes with myoclonic seizures • West syndrome • Lennox-Gastaut syndrome • Myoclonic astatic epilepsy (Doose syndrome) • Severe myoclonic epilepsy of infancy (Dravet syndrome)
    13. 13. West syndrome • Starts between the ages of 2 and 12 months • Triad of infantile spasms that usually occur in clusters (particularly in drowsiness or upon arousal), developmental regression, and a typical EEG picture – hypsarrhythmia. • Either cryptogenic or symptomatic • ARX gene (ambiguous genitalia) • Medical emergency (critical period of 3 weeks)
    14. 14. Lennox-Gastaut syndrome • Between the age of 2 and 10 years • Triad of developmental delay, multiple seizure types and 1-2 Hz spike–and-slow waves, polyspike bursts in sleep, and a slow background in wakefulness.
    15. 15. Myoclonic astatic epilepsy (Doose syndrome) • Onset of seizures is between the ages of 2 and 5 years • Similar to but milder than Lennox-Gastaut syndrome • Does not have tonic seizures or polyspike bursts in sleep • Prognosis is more favorable
    16. 16. Dravet syndrome • Most severe of the phenotypic spectrum of febrile seizures plus • Onset is in the 1st year of life, characterized by febrile and afebrile unilateral clonic seizures recurring every 1 or 2 months.
    17. 17. Progressive myoclonic epilepsies • Progressive dementia and worsening myoclonic and other seizures. • Type I or Unvericht Lundborg disease is more slowly progressive than the other types and usually starts in adolescence. • Type II or Lafora body disease can have an early childhood onset but usually starts in adolescence, is more quickly progressive, and is usually fatal.
    18. 18. Treatment - General • Patients with benign forms of myoclonic epilepsy often respond well to valproic acid or clonazepam. • The duration of treatment is usually approximately 5 years. • Second-line medications include ethosuximide, zonisamide, and topiramate.
    19. 19. Treatment - Specific • West syndrome is best treated with ACTH. • Vigabatrin - approved by the FDA for use in children with infantile spasms. • Treatment of seizures in Lennox-Gastaut syndrome varies according to the preponderant seizure type.
    20. 20. Treatment - Specific • Dravet syndrome is usually treated with valproate and benzodiazepines such as clonazepam. • Lamotrigine has been reported to exacerbate seizures in Dravet syndrome and other myoclonic epilepsies • Stiripentol and ketogenic diet may have a niche role in treating Dravet syndrome.

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