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
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
12. Epilepsy syndromes with myoclonic
seizures
• West syndrome
• Lennox-Gastaut syndrome
• Myoclonic astatic epilepsy (Doose syndrome)
• Severe myoclonic epilepsy of infancy (Dravet
syndrome)
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. 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. 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. 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. 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. 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. 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. 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.
Notes de l'éditeur
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.
