Dynamic balance function in phasic cervical dystonia following botulinum toxin therapy

Previous research by our group revealed normal dynamic balance function in pure tonic cervical dystonia (CD) with impaired equilibrium in phasic CD pa tients investigated at least 3 months following Botulinum toxin (BtxA) trea tment. The current study was pet-formed to determine whether impaired dynam ic equilibrium in phasic CD is influenced by symptomatic treatment with Btx A. Dynamic balance was tested in 20 patients with phasic CD on a dynamic pl atform with a cylindrical curved base (stabilometer) 4 weeks following BtxA treatment. Balance was assessed by the linear displacement of the platform and the maximum amplitude of platform displacement with open and closed ey es and compared with pre-BtxA data. Despite a clinically significant BtxA-i nduced reduction of phasic head movements, none of the platform measures im proved significantly. In addition, there was no correlation between the Btx A-induced clinical improvement and changes in any of the dynamic balance me asures pre- vs. post-BtxA. In conclusion. the persistent dynamic balance im pairment after effective BtxA therapy may indicate that disequilibrium in p hasic CD does not simply reflect disturbed vestibular input from repetitive head oscillations, but argues in favour of different sensorimotor processi ng in tonic and phasic CD. (C) 2001 Movement Disorder Society.