A new rating instrument to assess festination and freezing gait in Parkinsonian patients.

Festination and freezing of gait (FOG) are sudden episodic inabilities to initiate or sustain locomotion mostly experienced during the later stages of Parkinson's disease (PD) or other higher-level gait disorders. The aim of this study was to develop a clinical rating instrument for short-interval rating of festination and FOG. Foot movements of 33 patients were video taped and rated during 12 episodes in a standardized course on a four-level interval scale according to severity. Motor blocks were provoked in four situations and by three levels of dual-tasking (tasks). Addition of the item scores produced a FOG score. The assessment requires less than 15 min. The inter-rater and re-test reliability of the FOG score is high (Kendall kappa = 0.85-0.92, P < 0.0001). Variability of the item scale due to situations and tasks can be attributed to unidimensional group factors (Cronbach's alpha 0.84 and 0.94). Group comparisons and a logistic regression model show significant effects for both situations and tasks on the item scale (Friedman test: "situation": P < 0.0001, "task": P < 0.0001). Six patients with PD have significantly different scores during mobile (practical ON; 6.2 +/- 3.9) and immobile (practical OFF; 15.8 +/- 4.6) medication states (P < 0.05). The FOG score correlates with the 10 m number of steps (rho = 0.58; P = 0.001) and with the self-evaluation of FOG (rho = 0.51; P < 0.01). Our results encourage the further use of the FOG score to evaluate festination and FOG. (c) 2010 Movement Disorder Society.