Mobile Spasm

MOBILE SPASM (mobile spasm), changes in the intensity of muscle tone, expressed by alternating tonic tension and relaxation of muscles, reaching abnormal flaccidity and leading to the disappearance of plastic tone. Thus, in the same muscles, either significant hypertonia or sharp hypotonia occurs. Due to fluctuations between opposite states, this spasm is also called fluctuating spasm. The indicated changes in tone are most often observed in the distal parts of the extremities (fingers of hands and feet) and can affect individual muscles, both agonists and antagonists, as well as muscles not involved in movement. Often both agonists and antagonists are affected simultaneously. Atrophy is sometimes observed in the affected muscles. Changes in the intensity of tone lead to both characteristic involuntary slow movements and fixation in characteristic positions that suddenly disappear as soon as the spasm ends. For example, a finger, after extending, remains fixed in this position for some time, then a flexion spasm occurs, etc. (see Athetosis). Mobile spasm, however, in some cases can exist without athetoid movements or at least be more pronounced than the latter. Spasms often occur only with voluntary movements or with psychological excitement, as well as with various sensory irritations. With a decrease in external irritations, spasms decrease, usually disappearing during sleep. In severe cases, however, they may be continuous. Patho-anatomically, mobile spasm is most often associated with diseases of the basal ganglia. Since changes in tone associated with diseases of the basal ganglia are designated as rigor, Spatz proposes to call this symptom mobile rigor.