Orthostatic tremor is a unique tremor syndrome characterized by subjective feeling of unsteadiness during stance but only in severe cases during gait; patients rarely fall. None of the patients have problems when sitting and lying ( Deuschl G et al, 2010). The diagnosis is usually confirmed by EMG recordings of 13-18 Hz pattern (McManis PG et al, 1993). Clinically, tremor cannot be seen with the naked eye, but can be palpable and auscultable (‘Helicopter sign’ – auscultable noise similar to a distant helicopter( Brown P.1995). Orthostatic tremors (OT) are classified into three types – Primary orthostatic tremor, Orthostatic tremor plus and Symptomatic orthostatic tremor. Primary OT is an idiopathic condition, without any evidence of tremors in any other parts of the body. Orthostatic tremor plus is characterized by other primary neurological disorders such as restless legs syndrome, cerebellar ataxia, progressive supranuclear palsy and Parkinson’s disease. Symptomatic OT is noted in nontumoral aqueduct stenosis, after head trauma in vascular lesions and space occupying lesions ( Deuschl G et al, 2010).
Orthostatic tremor is rare and is most commonly noted in patients older than 40 years. It has been noted that OT is responsive to clonazepam and primidone. Others drugs which have been shown to have some effect include gabapentin, levodopa and valproate.