February 2012
Vercruysse S, Spildooren J, Heremans E,
Vandenbossche J, Levin O, Wenderoth N, Swinnen SP, Janssens L, Vandenberghe W,
Nieuwboer A
Freezing of gait (FOG) is an incapacitating problem in Parkinson's
disease that is difficult to manage therapeutically. We tested the
hypothesis that impaired rhythm and amplitude control is a common
mechanism of freezing which is also present during other rhythmic tasks.
Therefore, we compared the occurrence and spatiotemporal profiles of
freezing episodes during upper limb motion, lower limb motion, and FOG.
Eleven freezers, 12 non-freezers, and 11 controls performed a rhythmic
bilateral finger movement task. The triggering effect of movement speed,
amplitude, and coordination pattern was evaluated. Regression slopes
and spectral analysis addressed the spatial and temporal kinematic
changes inherent to freezing episodes.
The FOG Questionnaire score
significantly predicted severity of upper limb freezing, present in 9
freezers, and of foot freezing, present in 8 freezers. Similar to gait,
small-amplitude movements tended to trigger upper limb freezing, which
was preceded by hastened movement and a strong amplitude breakdown.
Upper limb freezing power spectra were broadband, including increased
energy in the “freeze band” (3–8 Hz). Contrary to FOG, unilateral upper
limb freezing was common and occurred mainly on the disease-dominant
side.
The findings emphasize that a core motor problem underlies
freezing which can affect various movement effectors. This deficit may
originate on the disease-dominant body side and interfere with amplitude
and timing regulation during repetitive limb movements. These results
may shift current thinking on the origins of freezing as being not
exclusively a gait failure.
