Dystonia as a patterned motor malflow.

The definition of dystonia has been renewed repeatedly but always within the context of overactive muscle contractions. In dystonia the muscles unnecessary for a motion fail to be adequately suppressed because of the loss of central motor control, resulting in inappropriate movements or abnormal postures ("overflow phenomenon"). This represents, however, only one side of the disrupted motor control. Some patients complain of the inability to activate muscles necessary for the intended task despite the lack of motor paresis, as best exemplified by the apraxia of eyelid opening. The author has ever coined the term "negative dystonia" for this phenomenon, which occurs hypothetically as a result of failed central motor flow and is often co-existent with overflow. Negative dystonia has a fixed pattern and sensory trick may be effective to ameliorate the symptom just as in the case of conventional dystonia. Hence we can speculate that the overflow and flow failure are the two sides of the same coin, both being caused by the loss of motor control. The current hypothesis is that dystonia is a representation of the patterned motor malflow (malicious flow) due to the loss of motor control.