Familial orthostatic tremor and essential tremor in two young brothers: A rare entity

Orthostatic Tremor and Orthostatic Myoclonus: Weight-bearing Hyperkinetic Disorders: A Systematic Review, New Insights, and Unresolved Questions

BACKGROUND

Orthostatic tremor (OT) and orthostatic myoclonus (OM) are weight-bearing hyperkinetic movement disorders most commonly affecting older people that induce "shaky legs" upon standing. OT is divided into "classical" and "slow" forms based on tremor frequency. In this paper, the first joint review of OT and OM, we review the literature and compare and contrast their demographic, clinical, electrophysiological, neuroimaging, pathophysiological, and treatment characteristics.

METHODS

A PubMed search up to July 2016 using the phrases "orthostatic tremor," "orthostatic myoclonus," "shaky legs," and "shaky legs syndrome" was performed.

RESULTS

OT and OM should be suspected in older patients reporting unsteadiness with prolonged standing and/or who exhibit cautious, wide-based gaits. Surface electromyography (SEMG) is necessary to verify the diagnoses. Functional neuroimaging and electrophysiology suggest the generator of classical OT lies within the cerebellothalamocortical network. For OM, and possibly slow OT, the frontal, subcortical cerebrum is the most likely origin. Clonazepam is the most useful medication for classical OT, and levetiracetam for OM, although results are often disappointing. Deep brain stimulation appears promising for classical OT. Rolling walkers reliably improve gait affected by these disorders, as both OT and OM attenuate when weight is transferred from the legs to the arms.

DISCUSSION

Orthostatic hyperkinesias are likely underdiagnosed, as SEMG is often unavailable in clinical practice, and thus may be more frequent than currently recognized. The shared weight-bearing induction of OT and OM may indicate a common pathophysiology. Further research, including use of animal models, is necessary to better define the prevalence and pathophysiology of OT and OM, in order to improve their treatment, and provide additional insights into basic balance and gait mechanisms.

Orthostatic Tremor: An Update on a Rare Entity

Background

Orthostatic tremor (OT) remains among the most intriguing and poorly understood of movement disorders. Compared to Parkinson’s disease or even essential tremor, there are very few articles addressing more basic science issues. In this review, we will discuss the findings of main case series on OT, including data on etiology, pathophysiology, diagnostic approach, treatment strategies, and outcome.

Methods

Data for this review were identified by searching PUBMED (January 1966 to August 2016) for the terms “orthostatic tremor” or “shaky leg syndrome,” which yielded 219 entries. We did not exclude papers on the basis of language, country, or publication date. The electronic database searches were supplemented by articles in the authors’ files that pertained to this topic.

Results

Owing to its rarity, the current understanding of OT is limited and is mostly based on small case series or case reports. Despite this, a growing body of evidence indicates that OT might be a progressive condition that is clinically heterogeneous (primary vs. secondary cases) with a broader spectrum of clinical features, mainly cerebellar signs, and possible cognitive impairment and personality disturbances. Along with this, advanced neuroimaging techniques are now demonstrating distinct anatomical and functional changes, some of which are consistent with neuronal loss.

Discussion

OT might be a family of diseases, unified by the presence of leg tremor, but further characterized by etiological and clinical heterogeneity. More work is needed to understand the pathogenesis of this condition.

Orthostatic tremor: current challenges and future prospects

This review provides an outlook of orthostatic tremor (OT), a rare adult-onset tremor characterized by subjective unsteadiness during standing that is relieved by sitting or walking. Recent case series with a long-time follow-up have shown that the disease is slowly progressive, spatially spreads to the upper limbs, and other neurological disorders may develop in about one-third of the patients. The diagnosis of OT hinges on the typical history of unsteadiness during standing, which is confirmed by electromyographic findings of a 13–18 Hz tremor that is typically absent during tonic activation while the patient is sitting and lying. Although the tremor is generated by a central oscillator, cerebellar and/or basal ganglia dysfunction are needed for its manifestation (double lesion hypothesis). However, functional neuroimaging findings have not consistently implicated the dopaminergic system in its pathogenesis. Drug treatments have been largely disappointing with no sustained benefits, although thalamic deep brain stimulation has helped some patients. Large-scale follow-up studies, more drug trials, and novel therapies are urgently needed.