The clinical spectrum of freezing of gait in Parkinson's disease.

Freezing of gait (FOG) is a common and very disabling symptom in Parkinson's disease (PD). It is usually observed in the advanced stage of the disease, although a mild form can be seen in the early stage. Although some studies have suggested that longer duration of dopaminergic treatment is associated with FOG, the disease progression alone may be responsible for the development of FOG. FOG can be experienced on turning, in narrow spaces, while reaching a destination, and in stressful situations. In PD, FOG is strongly associated with motor fluctuation. FOG is commonly observed in the "off" state and is observed less frequently in the "on" state. Dual tasking (cognitive load) aggravates FOG. Visual or auditory cues often resolve FOG. Analysis of gait revealed that the stepping rhythm suddenly jumps into high frequency (4-5 Hz) in FOG (hastening), and that floor reaction forces are disregulated. Since the hastening phenomenon was also reported in patients with lesions in the striatum and/or the frontal lobe, fronto-basal ganglia projections are considered essential for FOG. Careful observation and gait pattern analysis may lead to a successful management of individual PD patients with FOG. (c) 2008 Movement Disorder Society.