Turning and unilateral cueing in Parkinson's disease patients with and without freezing of gait

BACKGROUND Freezing of gait (FOG) is one of the most disabling symptoms in Parkinson's disease (PD), and cueing has been reported to improve FOG during straight-line walking. Studies on how cueing affects FOG during turning are lacking. Given the asymmetrical nature of turning and the asymmetrical disease expression, we aimed to gain a new perspective on how unilateral cueing may alleviate FOG. OBJECTIVE To explore disease dominance and turning side as contributing factors to turning problems and FOG and to investigate the effect of unilateral cueing. METHODS In the first study, 13 PD patients with FOG (freezers) and 13 without FOG (nonfreezers) turned toward their disease-dominant and nondominant side (off medication). During the second study, 16 freezers and 14 nonfreezers turned with and without a unilateral auditory cue at -10% of preferred cadence. Total number of steps, turn duration, cadence, and FOG episodes were measured using VICON. RESULTS Cadence, but not FOG frequency, was higher when turning toward the disease-dominant side. FOG started more frequently (64.9%) on the inner side of the turning cycle. Unilateral cueing seemed to prevent FOG in most patients, irrespective of the side at which the cue was offered. A carryover effect was found for cadence during turning, but the effect on FOG disappeared when the cue was removed. CONCLUSIONS The occurrence of FOG is not influenced by turning toward the disease-dominant or nondominant side, which is confirmed by the fact that it does not make a difference at which side unilateral cueing is applied. Cueing reduces FOG during turning, but these effects disappear dramatically after cue removal. This raises further questions as to the influence of training on cue dependency and on the feasibility of either continuous application of cues or using cognitive strategies as an alternative.