"On" freezing in Parkinson's disease: Resistance to visual cue walking devices

OBJECTIVE: To measure "on" freezing during unassisted walking (UW) and test if two devices, a modified inverted stick (MIS) and a visual laser beam st ick (LBS) improved walking speed and number of "on" freezing episodes in pa tients with Parkinson's disease (PD). BACKGROUND: Multiple visual cues can overcome "off" freezing episodes and c an be useful in improving gait function in parkinsonian patients. These dev ices have not been specifically tested in "on" freezing, which is unrespons ive to pharmacologic manipulations. METHODS: Patients with PD, motor fluctuations and freezing while "on," atte mpted walking on a 60-ft track with each of three walking conditions in a r andomized order: UW, MIS, and LBS. Total time to complete a trial, number o f freezes, and the ratio of walking time to the number of freezes were comp ared using Friedman's test. RESULTS: Twenty-eight patients with PD, mean age 67.81 years (standard devi ation [SD] 7.54), mean disease duration 13.04 years (SD 7.49), and mean mot or Unified Parkinson's Disease:Rating Scale score "on" 32.59 (SD 10.93), pa rticipated in the study. There was a statistically significant correlation of time needed to complete a trial and number of freezes for all three cond itions (Spearman correlations: UW 0.973, LBS 0.0.930, and MIS 0.842). The m edian number of freezes, median time to walk in each condition, and median walking time per freeze were not significantly different in pairwise compar isons of the three conditions (Friedman's test). Of the 28 subjects, six sh owed improvement with the MIS and six with the LBS in at least one outcome measure. CONCLUSION: Assisting devices, specifically based on visual cues, are not c onsistently beneficial in overcoming "on" freezing in most patients with PD . Because this is an otherwise untreatable clinical problem and because occ asional subjects do respond, cautious trials of such devices under the supe rvision of a health professional should be conducted to identify those pati ents who might benefit from their long-term use.