Eligible patients ( ie , those aged @-@ years , disease duration @ years , Toronto Western Spasmodic Torticollis Rating Scale -LSB- TWSTRS -RSB- severity score @ points ) were randomly assigned ( @:@ ) to receive active neurostimulation ( frequency @ Hz ; pulse width @ s ; amplitude @ V below adverse event threshold ) or sham stimulation ( amplitude @ V ) by computer-generated randomisation lists with randomly permuted block lengths stratified by centre .