Gait in SWEDDs patients: comparison with Parkinson's disease patients and healthy controls.

Patients diagnosed with Parkinson's disease on clinical grounds who subsequently turn out to have normal dopamine transporter imaging have been referred to as SWEDDs (scans without evidence of dopaminergic deficits). Despite having clinical features similar to those of Parkinson's disease, these patients seem to have different pathophysiology, prognosis, and treatment requirements. In this study we determined the similarities and differences in the gaits of SWEDDs and Parkinson's disease patients to investigate whether walking patterns can distinguish these entities. We used 3-D motion capture to analyze the gaits of 11 SWEDDs patients (who had unilateral or asymmetric upper limb tremor with a rest component), 12 tremor-dominant Parkinson's disease patients, and 13 healthy control participants. In common with Parkinson's disease patients, SWEDDs patients had a slow gait mainly because of a small stride length, as well as a reduced arm swing. However, several abnormal features of posture and gait in Parkinson's disease were normal in SWEDDs. Thus, SWEDDs patients had normal trunk and elbow posture, normal stride length variability, and normal bilateral step-phase coordination, all of which were abnormal in Parkinson's disease patients. We also searched for signs of ataxic movements during normal and tandem walking, but found no evidence that ataxic gait was a general feature in SWEDDs. These findings could aid the clinician in identification of potential tremulous SWEDDs cases. © 2011 Movement Disorder Society.