Freezing of gait in parkinson’s disease: a perceptual cause for a motor impairment?

Abstract

Freezing of gait (FOG) has been long thought of as a motor impairment. However, anecdotal patient reports have implied that these difficulties occur more frequently in confined spaces, and hence it is important to determine how perception of space might contribute to FOG. In an attempt to determine whether FOG may be related to a perceptual impairment, the present study evaluated how doorway size influenced characteristics of gait that might be indicative of freezing. Changes in spatiotemporal aspects of gait were evaluated while walking through three different sized doorways (narrow, normal, and wide) in three separate groups: 15 individuals with PD confirmed to be experiencing FOG at the time of test; 16 non-FOG individuals with PD; and 16 healthy age-matched control participants. Results for step length indicated that the FOG group was most affected by the narrow doorway and was the only group whose step length was dependent on upcoming doorway size. Importantly, the FOG group also displayed increased within-trial variability of step length and step time, which was exaggerated as doorway size decreased. Base of support measures indicated that the non-FOG participants walked similar to the healthy group in the normal and wide doorway conditions, but acted similar to the FOG group in the narrow doorway condition only. These results support the notion that some occurrences of freezing may be the result of an underlying perceptual mechanism that interferes with online movement planning. Neither healthy individuals nor individuals with PD absent of FOG exhibited this same effect.