Voluntary suppressibility of
abnormal movements is helpful in the classification of
movement disorders because this ability appears to be a common component of
tics. However, there has been no systematic study of voluntary suppressibility in other
movement disorders. We have therefore assessed 146 patients with
tremors and dyskinetic disorders as to their ability to suppress movements by mental concentration. Patients were videotaped while trying to stop their movements, and the length of time they could suppress their
abnormal movements was recorded. One hundred percent (10 of 10) of patients with
tics could suppress movements for an average of 2.5 min. Two percent (1 of 50) of
essential tremor patients could suppress the
tremor, and the
tremor of 24% (12 of 50) was made worse by mental concentration. Eighty percent (4 of 5) of
neuroleptic-induced
tremor could be improved mentally. Seventy percent (35 of 50) of patients with parkinsonian
tremor could voluntarily diminish their
tremor for an average of 48 s. Fifty percent (8 of 16) of
chorea (
tardive dyskinesia,
Huntington's disease, postencephalitic) was reduced.
Dystonia was suppressible in 20% (3 of 15). It is concluded that
movement disorders besides
tics can be voluntarily suppressed and that suppressibility should not be used to classify
movement disorders.
Tics, however, are easier to suppress and can be suppressed for a longer time.