Other Forms of Myoclonus
Psychogenic myoclonus has a psychological rather than a physiologic basis. This disorder is more common in women than in men and is usually worsened with exposure to stress or anxiety. The typical movements are segmental or generalized but can be focal. The diagnosis of psychogenic myoclonus often requires electrophysiologic testing, including electromyography (EMG), electroencephalography (EEG), and back-averaging EEG-EMG to rule out physiologic causes.
In myoclonus dystonia, arm involvement is prominent, and the legs are usually unaffected.
- Onset in first or second decade
- Myoclonus in all; dystonia in half
- Males and females equally affected
- Relatively benign but variable course
- Autosomal-dominant mode of inheritance
- Other neurologic deficits absent
Opsoclonus-myoclonus, also known as Kinsbourne syndrome, is the dancing eyes syndrome or myoclonic encephalopathy of infants. The primary features of the disorder include rapid irregular eye movements (saccadic eye movements) and action myoclonus, which typically involves the face, limbs, fingers, and trunk. The age of symptom onset is usually less than 2 years in children and may be any age in adults.