The Phenomenology of Primary Orthostatic Tremor

Background The presence and prevalence of several neurological signs in patients with primary orthostatic tremor have not been systematically studied. Objectives To assess the prevalence of clinical features of primary orthostatic tremor. Methods Video-based assessment by four raters of standardized neurological examination of 11 patients with primary orthostatic tremor. Results On standing, bent knees (7/11), hem sign (6/10), and a broad base of support (6/11) were the three most prevalent signs. Examination of gait revealed abnormal tandem gait (9/11) and bent knees (6/11) as the most prevalent clinical signs. In the arms, none of the patients displayed bradykinesia, ataxia, or dystonia. In the legs, ataxia was absent in all patients and bradykinesia was present in only one patient. Conclusions Abnormal tandem gait, bent knees, hem sign, and broad base on standing are the most prevalent clinical signs in primary orthostatic tremor. We did not encounter clear extrapyramidal or unequivocal cerebellar signs.