The natural history of 51 idiopathic torsion dystonia cases identified
in a nationwide survey in Israel was studied. In order to take advant
age of all data regarding the evolution of the disease, independently
of the length of follow-up, we have used a life table method of analys
is. An estimate of the mean degree of generalization of the disease at
different times from onset was calculated and a curve of the estimate
d temporal evolution was drawn. This analysis confirmed the heterogene
ity of the disease course. The most rapid deterioration occurred in pa
tients with juvenile onset in the lower limbs, particularly in the fir
st 2 years following the onset. The rate of evolution was not influenc
ed by gender or familiality. The course of the disease seemed more del
eterious in non-Ashken-azic Jews. The present statistical method of es
timating the evolution in different patient groups should be useful es
pecially for the evaluation of therapeutic interventions.