Primary orthostatic tremor

This is a rare condition which has occasionally been misdiagnosed as a psychiatric disorder. Patients have a sense of unsteadiness or fear of falling which is relieved upon sitting, leaning on an object or walking (1)

The characteristic clinical features are:

• unsteadiness when standing still which is relieved on walking
• falls are uncommon
• leg muscles ripple palpably on standing

Surface electromyography reveals rhythmic activation of lower limb muscles at a frequency of 13-18 Hz

• although cases of slower orthostatic tremor have been reported and tremor is not always visible (1)

The cause of the condition is unknown although there seem to be abnormalities in the brain stem and cerebellum.

Orthostatic tremor has been found to respond to clonazepam and gabapentin most often, but when in the setting of parkinsonism, dopaminergic medications such as levodopa or pramipexole can be helpful (1)

• primidone was also thought to be helpful

Reference:

• Frei K, Truong DD. Medications used to treat tremors. J Neurol Sci. 2022 Apr 15;435:120194. doi: 10.1016/j.jns.2022.120194. Epub 2022 Feb 19. PMID: 35279634.