Dystonia-plus Syndromes
Experts established the "dystonia-plus syndrome" etiologic classification to help differentiate dystonic disorders that are distinct from primary (idiopathic) dystonias; secondary (symptomatic) dystonias; and neurodegenerative, usually hereditary (heredodegenerative) disorders in which other neurologic signs are typically present. In contrast, the dystonia-plus syndromes include nondegenerative, neurochemical disorders characterized by dystonia as well as additional neurologic features, such as myoclonus or parkinsonism. Myoclonus is characterized by sudden, involuntary, "shock-like" muscle contractions. In addition, these brief, jerk-like movements are often accompanied by periodic interruptions in voluntary muscle contraction (muscle inhibition), leading to lapses of sustained posture. Signs of parkinsonism include slowness of movement (bradykinesia), rigidity, postural instability, and tremor at rest. Dystonia-plus syndromes currently include the following:
- Dopa-responsive dystonia (DRD) or Segawa syndrome
- Rapid-onset dystonia-parkinsonism (RDP)
- Myoclonus-dystonia
