Natural history and syndromic associations of orthostatic tremor: a review of 41 patients

TMS of the left primary motor cortex improves tremor intensity and postural control in primary orthostatic tremor

A ponto-cerebello-thalamo-cortical network is the pathophysiological correlate of primary orthostatic tremor. Affected patients often do not respond satisfactorily to pharmacological treatment. Consequently, the objective of the current study was to examine the effects of a non-invasive neuromodulation by theta burst repetitive transcranial magnetic stimulation (rTMS) of the left primary motor cortex (M1) and dorsal medial frontal cortex (dMFC) on tremor frequency, intensity, sway path and subjective postural stability in primary orthostatic tremor. In a cross-over design, eight patients (mean age 70.2 ± 5.4 years, 4 female) with a primary orthostatic tremor received either rTMS of the left M1 leg area or the dMFC at the first study session, followed by the other condition (dMFC or M1 respectively) at the second study session 30 days later. Tremor frequency and intensity were quantified by surface electromyography of lower leg muscles and total sway path by posturography (foam rubber with eyes open) before and after each rTMS session. Patients subjectively rated postural stability on the posturography platform following each rTMS treatment. We found that tremor frequency did not change significantly with M1- or dMFC-stimulation. However, tremor intensity was lower after M1- but not dMFC-stimulation (p = 0.033/ p = 0.339). The sway path decreased markedly after M1-stimulation (p = 0.0005) and dMFC-stimulation (p = 0.023) compared to baseline. Accordingly, patients indicated a better subjective feeling of postural stability both with M1-rTMS (p = 0.007) and dMFC-rTMS (p = 0.01). In conclusion, non-invasive neuromodulation particularly of the M1 area can improve postural control and tremor intensity in primary orthostatic tremor by interference with the tremor network.

Levodopa-induced dyskinesia: interplay between the N-methyl-D-aspartic acid receptor and neuroinflammation

Parkinson's disease (PD) is a common neurodegenerative disorder of middle-aged and elderly people, clinically characterized by resting tremor, myotonia, reduced movement, and impaired postural balance. Clinically, patients with PD are often administered levodopa (L-DOPA) to improve their symptoms. However, after years of L-DOPA treatment, most patients experience complications of varying severity, including the "on-off phenomenon", decreased efficacy, and levodopa-induced dyskinesia (LID). The development of LID can seriously affect the quality of life of patients, but its pathogenesis is unclear and effective treatments are lacking. Glutamic acid (Glu)-mediated changes in synaptic plasticity play a major role in LID. The N-methyl-D-aspartic acid receptor (NMDAR), an ionotropic glutamate receptor, is closely associated with synaptic plasticity, and neuroinflammation can modulate NMDAR activation or expression; in addition, neuroinflammation may be involved in the development of LID. However, it is not clear whether NMDA receptors are co-regulated with neuroinflammation during LID formation. Here we review how neuroinflammation mediates the development of LID through the regulation of NMDA receptors, and assess whether common anti-inflammatory drugs and NMDA receptor antagonists may be able to mitigate the development of LID through the regulation of central neuroinflammation, thereby providing a new theoretical basis for finding new therapeutic targets for LID.

Deep brain stimulation and spinal cord stimulation for orthostatic tremor: A systematic review

BACKGROUND

Orthostatic tremor is a rare and debilitating movement disorder. Its first-line treatment is pharmacological. For pharmaco-refractory patients, surgical treatment options such as deep brain stimulation (DBS) and spinal cord stimulation (SCS) have been investigated recently.

OBJECTIVES

We conducted a systematic review of all published outcome and safety data on DBS and SCS for orthostatic tremor patients.

METHODS

We searched Pubmed and Embase for studies describing orthostatic tremor patients treated with DBS or SCS. We collected all available outcome and safety data and our primary endpoint was the change in unsupported stance duration 1 year postoperatively (±6 months).

RESULTS

We included 15 studies, reporting on 32 orthostatic tremor patients who underwent DBS, 4 patients SCS and 2 both. The ventral intermediate nucleus and the zona incerta were targeted in 25/34 and 9/34 DBS cases, respectively. The median stance time at 1 year follow-up was 240 s compared to 30 s pre-operatively (p < 0.001). Stimulation-induced side effects occurred in the majority of patients, but were often transient. Bilateral stimulation appeared more effective than unilateral and stimulation settings were comparable to thalamic DBS for essential tremor. There were insufficient data available to draw meaningful conclusions on the long-term effects of DBS. Due to insufficient data, no conclusions could be drawn on the effects of SCS on orthostatic tremor.

CONCLUSION

DBS may be effective to increase stance time in orthostatic tremor patients in the first year, but further research is necessary to evaluate the long-term effects and the role of spinal cord stimulation.

Movement disorders of the mouth: a review of the common phenomenologies

Movement disorders of the mouth encompass a spectrum of hyperactive movements involving the muscles of the orofacial complex. They are rare conditions and are described in the literature primarily in case reports originating from neurologists, psychiatrists, and the dental community. The focus of this review is to provide a phenomenological description of different oral motor disorders including oromandibular dystonia, orofacial dyskinesia and orolingual tremor, and to offer management strategies for optimal treatment based on the current literature. A literature search of full text studies using PubMed/Medline and Cochrane library combined with a manual search of the reference lists was conducted until June 2021. Results from this search included meta-analyses, systematic reviews, reviews, clinical studies, case series, and case reports published by neurologists, psychiatrists, dentists and oral and maxillofacial surgeons. Data garnered from these sources were used to provide an overview of most commonly encountered movement disorders of the mouth, aiding physicians in recognizing these rare conditions and in initiating appropriate therapy.

The Phenomenology of Primary Orthostatic Tremor

Background

Objectives

Methods

Results

Conclusions

Parkinsonism and tremor syndromes

Tremor, the most common movement disorder, may occur in isolation or may co-exist with a variety of other neurologic and movement disorders including parkinsonism, dystonia, and ataxia. When associated with Parkinson's disease, tremor may be present at rest or as an action tremor overlapping in phenomenology with essential tremor. Essential tremor may be associated not only with parkinsonism but other neurological disorders, suggesting the possibility of essential tremor subtypes. Besides Parkinson's disease, tremor can be an important feature of other parkinsonian disorders, such as atypical parkinsonism and drug-induced parkinsonism. In addition, tremor can be a prominent feature in patients with other movement disorders such as fragile X-associated tremor/ataxia syndrome, and Wilson's disease in which parkinsonian features may be present. This article is part of the Special Issue "Parkinsonism across the spectrum of movement disorders and beyond" edited by Joseph Jankovic, Daniel D. Truong and Matteo Bologna.

Transcranial Magnetic Stimulation in Tremor Syndromes: Pathophysiologic Insights and Therapeutic Role

Transcranial magnetic stimulation (TMS) is a painless, non-invasive, and established brain stimulation technique to investigate human brain function. Over the last three decades, TMS has shed insight into the pathophysiology of many neurological disorders. Tremor is an involuntary, rhythmic oscillatory movement disorder commonly related to pathological oscillations propagated via the cerebello-thalamo-cortical pathway. Although tremor is the most common movement disorder and recent imaging studies have enhanced our understanding of the critical pathogenic networks, the underlying pathophysiology of different tremor syndromes is complex and still not fully understood. TMS has been used as a tool to further our understanding of tremor pathophysiology. In addition, repetitive TMS (rTMS) that can modulate brain functions through plasticity effects has been targeted to the tremor network to gain potential therapeutic benefits. However, evidence is available for only a few studies that included small patient samples with limited clinical follow-up. This review aims to discuss the role of TMS in advancing the pathophysiological understanding as well as emerging applications of rTMS for treating individual tremor syndromes. The review will focus on essential tremor, Parkinson's disease tremor, dystonic tremor syndrome, orthostatic tremor, and functional tremor.

New developments for spinal cord stimulation

Spinal cord stimulation (SCS) is a well-established therapy for the treatment of chronic neuropathic pain. Newer SCS waveforms have improved patient outcomes, leading to its increased utilization among many pain conditions. More recently, SCS has been used to treat some symptoms in several movement disorders because of its good profile tolerability and capacity to stimulate local and distant areas of the central nervous system. After the original experimental findings in animal models of Parkinson's disease (PD) in the late 2000s, several studies have reported the beneficial clinical effects of SCS stimulation on gait in PD patients. Additionally, the spinal cord has emerged as a potential therapeutic target to treat essential and orthostatic tremor, some forms of ataxia, and atypical parkinsonisms. In this chapter, we describe the most recent advances in SCS for pain and the rationale and potential mechanism of action of stimulating the spinal cord for treating movement disorders, focusing on its network modulation. We also summarize the main clinical studies performed to date as well as their limitations and future perspectives.

Post-stroke Movement Disorders: Clinical Spectrum, Pathogenesis, and Management

Involuntary movements develop after 1-4% of strokes and they have been reported in patients with ischemic and hemorrhagic strokes affecting the basal ganglia, thalamus, and/or their connections. Hemichorea-hemiballism is the most common movement disorder following a stroke in adults while dystonia is most common in children. Tremor, myoclonus, asterixis, stereotypies, and vascular parkinsonism are other movement disorders seen following stroke. Some of them occur immediately after acute stroke, some can develop later, and others may have delayed onset progressive course. Proposed pathophysiological mechanisms include neuronal plasticity, functional diaschisis, and age-related differences in brain metabolism. There are no guidelines regarding the management of post-stroke movement disorders, mainly because of their heterogeneity.

Electroencephalography in Orthostatic Tremor: A Prospective Study of 30 Patients

Background

Orthostatic tremor (OT) is characterized by a sensation of instability while standing, associated with high frequency (1318 Hz) tremor in the legs. Small retrospective series have reported electroencephalography (EEG) findings in OT with discordant results.

Methods

We prospectively enrolled 30 OT subjects. Mean age = 68.3 (range 5487) with mean disease duration 16.3 years (range 444). A modified 1020 system EEG recording with additional midline electrodes was obtained. EMG electrodes were placed on quadricep muscles. EEG recording was performed at rest, during sleep and while standing unassisted.

Results

In all subjects, EEG showed normal background, normal drowsiness and/or stage 2 sleep, and normal responses to hyperventilation and photic stimulation. These normal results persisted during stance. EEG abnormalities were found in 3 subjects (anterior-mid temporal slow activity), but were not position-dependent and were judged unlikely to be related to OT. Tremor artifact while standing was noted in all subjects, however it was measurable in 26 with frequency in the OT range in 25. When compared with EMG, the average difference in frequency was small at 1.2 Hz (range 0.52.5, p 0.46). Visual EEG analysis in OT patients did not reveal electrographic abnormalities even upon standing unassisted.

Discussion

EEG was normal on this prospective, relatively large OT series. Clinicians interpreting video-EEGs should be aware of the OT artifact that can be seen in EEG and EKG leads mostly while standing.

What Shall We Do for the Patients with Shaky Leg Syndrome? A Review of 23 Patients

Orthostatic tremor (OT) is not an uncommon symptom in various neurodegenerative diseases. However, the nature and pathophysiology of OT involve a complex network of tremors and dopaminergic pathways. We assessed patients who complained of prominent leg tremors described as "shaky leg." We analyzed their characteristics and evaluated them with neuroimaging and electrophysiological tools. A total of 23 patients who experienced an uncomfortable symptom of leg tremor were retrospectively enrolled from April 2014 to October 2019. Previous medical history, brain MRI, and surface electromyography (EMG) data were analyzed. The [18F]-FP-CIT brain positron emission tomography (PET) and the Unified Parkinson's Disease Rating Scale (UPDRS) were assessed for patients who showed parkinsonism. The causes of OT varied: parkinsonism (n = 5), idiopathic causes (n = 4), secondary causes (n = 3, trauma, brain lesion, arteriovenous malformation), drug reactions (n = 3, valproate, perphenazine, haloperidol), other neurological disorders (n = 5, essential tremor, dystonia, restless leg syndrome, REM sleep behavior disorder, dementia), alcohol withdrawal (n = 1), functional movement disorder (n = 1), and an unknown cause (n = 1). The frequency range varied (2.6-15 Hz) and according to the new consensus statement on the classification of OT, 4 patients had primary OT, 2 had "primary OT plus," 12 had slow OT, and 5 had orthostatic myoclonus. The prognosis associated with the use of medication was generally poor; however, clonazepam and levodopa were the most effective drugs. In conclusion, we found that different types of OT and orthostatic myoclonus were diagnosed by electrophysiological evaluation and neuroimaging tools even if they showed the same symptoms as "shaky leg." In addition, it is possible to roughly estimate the response to medication according to the type of OT and the cause. To clarify the pathophysiology of OT, a large number of longitudinal cohort studies and detailed neuroimaging and electrophysiological evaluations are needed.

Associated co-morbidities in a retrospective cohort of orthostatic tremor

BACKGROUND

Orthostatic tremor (OT) is characterized by tremor in orthostatism. Primary OT is characterized by a high-frequency tremor at surface EMG recording and assumed to be idiopathic, whereas slow-frequency OT is classically associated with neurological pathologies. We report here a retrospective monocentric cohort study of primary (fast OT) and pseudo-OT (slow OT) patients to describe associated neurological and non-neurological co-morbidities.

METHODS

Between November 2014 and October 2019, 27 patients with OT were selected from the EMG database of the Department of Clinical Physiology in Lariboisière' s hospital. Patients were classified in primary OT if tremor frequency was ≥ 13 Hz and in pseudo-OT if tremor frequency was < 13 Hz.

RESULTS

Leg tremor on standing represented 10.2% of all tremor recordings. Ten patients were included in the primary and 17 in the pseudo-OT group. Females were predominant (62.9%) (p = 0.04). Mean age at diagnosis was 64.8 ± 1.1 years. At the first visit, a movement disorder was associated with 30% of primary OT, among them one CADASIL patient, whereas extrapyramidal or cerebellar disorders were reported in 100% of pseudo-OT, among them three Wilson's disease patients. These pathologies all preceded primary OT and occurred concomitantly with pseudo-OT. Frequency remained unchanged during evolution, except pseudo-OT in two patients that completely resolved following the introduction of antiParkinsonian drugs. Treatment of primary OT was partially effective in 28% and in 50% of pseudo-OT patients.

CONCLUSION

In this monocentric study, movement disorders were present in 30% of primary OT patients. This result questions the term "idiopathic" or "primary" OT, but the small number of patients does not allow answering this issue.

A Chinese case of fragile X-associated tremor/ataxia syndrome (FXTAS) with orthostatic tremor:case report and literature review on tremor in FXTAS

BACKGROUND

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late onset, X-linked genetic, neurodegenerative disorder caused by a "premutation (PM)" in the fragile X mental retardation 1 (FMR1) gene. Here we report a case of FXTAS from mainland of China who presented with rare orthostatic tremor. A review of tremor of FXTAS in the literature is also included.

CASE PRESENTATION

A 67-year-old right-handed farmer started with tremor of both legs 8 years ago which was present while standing but absent when sitting or lying and progressed with unsteady gait one and a half years ago. The brain MRI showed high intensity signal in the bilateral middle cerebellar peduncles (MCP) in T2-weighted and fluid-attenuated inversion recovery (FLAIR) images and gene test for premutation for FMR1 was positive with 101 CGG repeats. The patient met the the diagnosis of definite FXTAS. Clonazepam and topiramate were administered to control tremor. We reviewed the literature and identified 64 cases with detailed clinical and genetic information. Orthostatic tremor associated with FXTAS is very rare. We found 85.2% patients reported tremor,42.6% with intention tremor,36.1% with kinetic tremor,32.8% with rest tremor and 29.5% with posture tremor. 37.7% of patients who have tremor showed at least two types of tremor. There were 6 patients with isolated rest tremor. There was 2 patient with voice tremor and 6 with head tremor. We also found that 74.6% FXTAS patients had family history of FMR1 gene associated diseases including Fragile X syndrome (FXS), FXTAS or fragile X-associated primary ovarian insufficiency (FXPOI).

CONCLUSIONS

Adding our data to the available literature suggests that orthostatic tremor could be a rare initial manifestation of FXTAS and the review will increasing our understanding the phenotype of tremor in FXTAS. Family history of FMR1 gene associated diseases might be an important clue to the diagnosis.

Levodopa-Responsive Primary Slow Orthostatic Tremor: A Premotor Sign of Parkinson's Disease?

We present a case of primary orthostatic tremor (OT) responsive to dopaminergic medication. The patient was a 62-year-old woman, who had leg tremor on standing for 2 years. No parkinsonian or other neurological signs were observed. Surface electromyography of the quadriceps muscles showed regular 5–6 Hz muscle discharges. [¹²³I]-FP-CIT DAT-SPECT imaging revealed decreased specific binding ratio values in the striatum compared with age-matched controls. Her leg tremor almost completely disappeared following administration of levodopa 200 mg and pramipexole 0.75 mg. Since her OT with low-frequency discharge was responsive to dopaminergic medication, we speculate that it may be a premotor sign of Parkinson's disease.

Slow Orthostatic Tremor: Review of the Current Evidence

Background

Orthostatic tremor (OT) is defined as tremor in the legs and trunk evoked during standing. While the classical description is tremor of ≥13 Hz, slower frequencies are recognized. There is disagreement as to whether the latter represents a slow variant of classical OT, or different tremor disorder(s) given frequent coexistent neurological disease.

Methods

A systematic literature search of PubMed was performed in February 2019 for “slow orthostatic tremor” and related terms which generated 573 abstracts, of which 61 were included.

Results

Between 1970 and 2019, there were 70 cases of electrophysiologically confirmed slow OT. Two-thirds were female, of mean age 60 years (range 26–86), and mean disease duration 6 years (range 0–32). One-third of cases were isolated, and two-thirds had a coexistent disorder(s), including parkinsonism (30%), ataxia (12%), and dystonia (10%). Postural arm tremor was present in 34%. Median tremor frequency was 6–7 Hz (range 3–12). Tremor bursts ranged from 50 to 150 ms duration, and were alternating or synchronous in antagonistic and/or analogous muscles. Low and high coherences were reported. Five cases (7%) had coexistent classical OT. Clonazepam was the most effective medication across all frequencies, and levodopa was effective for 4–7 Hz OT with coexistent parkinsonism. Two cases resolved with the treatment of Graves’ disease. Electrophysiology and imaging predominantly support a central tremor generator.

Discussion

While multiple lines of evidence separate slow OT from classical OT, clinical and electrophysiological overlap may occur. Primary and secondary causes are identified, similar to classical OT. Further exploration to clarify these slow OT subtypes, clinically and neurophysiologically, is proposed.

A data mining approach for classification of orthostatic and essential tremor based on MRI-derived brain volume and cortical thickness

Objective

Orthostatic tremor (OT) is an extremely rare, misdiagnosed, and underdiagnosed disorder affecting adults in midlife. There is debate as to whether it is a different condition or a variant of essential tremor (ET), or even, if both conditions coexist. Our objective was to use data mining classification methods, using magnetic resonance imaging (MRI)‐derived brain volume and cortical thickness data, to identify morphometric measures that help to discriminate OT patients from those with ET.

Methods

MRI‐derived brain volume and cortical thickness were obtained from 14 OT patients and 15 age‐, sex‐, and education‐matched ET patients. Feature selection and machine learning methods were subsequently applied.

Results

Four MRI features alone distinguished the two, OT from ET, with 100% diagnostic accuracy. More specifically, left thalamus proper volume (normalized by the total intracranial volume), right superior parietal volume, right superior parietal thickness, and right inferior parietal roughness (i.e., the standard deviation of cortical thickness) were shown to play a key role in OT and ET characterization. Finally, the left caudal anterior cingulate thickness and the left caudal middle frontal roughness allowed us to separate with 100% diagnostic accuracy subgroups of OT patients (primary and those with mild parkinsonian signs).

Conclusions

A data mining approach applied to MRI‐derived brain volume and cortical thickness data may differentiate between these two types of tremor with an accuracy of 100%. Our results suggest that OT and ET are distinct conditions.

Fast Orthostatic Tremor in Parkinson's Disease: Case Report and Comprehensive Review of Literature

Background

Orthostatic tremor (OT) is a rare symmetric tremor disorder occasionally observed in association with other movement disorders.

Case report

We report the presence of a fast OT in a case of Parkinson’s disease (PD), and provide a comprehensive review of the literature.

Discussion

A fast OT presenting as unsteadiness may be a presenting symptom of PD. This symptom may be nonresponsive to levodopa, and benzodiazepines should be prescribed to adequately control the OT and reduce disability.

The Top 50 Most-Cited Articles in Orthostatic Tremor: A Bibliometric Review

Background

Article-level citation count is a hallmark indicating scientific impact. We aimed to pinpoint and evaluate the top 50 most-cited articles in orthostatic tremor (OT).

Methods

The ISI Web of Knowledge database and 2017 Journal Citation Report Science Edition were used to retrieve the 50 top-cited OT articles published from 1984 to April 2019. Information was collected by the Analyze Tool on the Web of Science, including number of citations, publication title, journal name, publication year, and country and institution of origin. Supplementary analyses were undertaken to clarify authorship, study design, level of evidence, and category.

Results

Up to 66% of manuscripts were recovered from five journals: Movement Disorders (n = 18), Brain (n = 4), Journal of Clinical Neurophysiology (n = 4), Neurology (n = 4), and Clinical Neurophysiology (n = 3). Articles were published between 1984 and 2018, with expert opinion as the predominant design (n = 22) and review as category (n = 17). Most articles had level 5 evidence (n = 26). According to their countries of origin, 34% of articles belonged to the United States (n = 17) leading the list, followed by United Kingdom (n = 15). University College London yielded the greater number of articles (n = 12), followed by the University of Kiel (n = 9). Most popular authors were G. Deuschl (n = 10), C.D. Marsden (n = 6), J. Jankovic (n = 5), P.D. Thompson (n = 5), J.C. Rothwell (n = 5), L.J. Findley (n = 4), and P. Brown (n = 4), who together accounted for 48% of them. All papers were in English.

Discussion

Publishing high-cited OT articles could be facilitated by source journal, study design, category, publication language, and country and institution of origin.

Anxiety spectrum disorders are common in patients with orthostatic tremor

Background

Orthostatic Tremor (OT) is a rare movement disorder characterized by a sensation of unsteadiness while standing and associated with high frequency tremors. Patients with OT commonly report a fear of falling and significant limitations in everyday activities. The prevalence of psychiatric comorbidities in OT patients has not been well-studied.

Methods

Subjects were evaluated by trained psychiatry researchers using the Mini International Neuropsychiatric Interview (M.I.N.I.). The M.I.N.I is a validated screening tool for psychiatric disorders. A standardized history covering previous psychiatric symptoms and illnesses was also obtained.

Results

29 OT subjects were evaluated. The mean age was 67.7 years with female preponderance (89.3%). The average disease symptom duration was 18.2 years. 58.6% of the subjects had seen a mental health professional during the course of their OT illness. 24.1% of the subjects had a past history of depression, and 10.3% reported a family history of any psychiatric condition. 37.9% of the subjects screened positive for agoraphobia. Two of 29 subjects (6.9%) were classified as having a current major depressive episode and one subject (3.4%) was at risk for suicide.

Conclusions

Psychiatric comorbidities are highly prevalent in OT patients, especially anxiety-spectrum disorders. Further studies are needed to understand if psychiatric disorders appear as a secondary response to the patient's symptoms, or are a primary non-motor manifestation of OT.

Health-Related Quality of Life Is Severely Affected in Primary Orthostatic Tremor

Background

Primary orthostatic tremor (POT) is a movement disorder characterized by unsteadiness upon standing still due to a tremor affecting the legs. It is a gradually progressive condition with limited treatment options. Impairments in health-related quality of life (HQoL) seem to far exceed the physical disability associated with the condition.

Methods

A multi-center, mixed-methodology study was undertaken to investigate 40 consecutive patients presenting with POT to four movement disorder centers in France. HQoL was investigated using eight quantitative scales and a qualitative study which employed semi-structured interviews. Qualitative data were analyzed with a combination of grounded-theory approach.

Results

Our results confirm that HQoL in POT is severely affected. Fear of falling was identified as the main predictor of HQoL. The qualitative arm of our study explored our initial results in greater depth and uncovered themes not identified by the quantitative approach.

Conclusion

Our results illustrate the huge potential of mixed methodology in identifying issues influencing HQoL in POT. Our work paves the way for enhanced patient care and improved HQoL in POT and is paradigmatic of this modern approach for investigating HQoL issues in chronic neurological disorders.

Diagnosis and Management of Tremor

PURPOSE OF REVIEW

Tremor, which is a rhythmic oscillation of a body part, is among the most common involuntary movements. Rhythmic oscillations may manifest in a variety of ways; as a result, a rich clinical phenomenology surrounds tremor. For this reason, diagnosing tremor disorders can be particularly challenging. The aim of this article is to provide the reader with a straightforward approach to the diagnosis and management of patients with tremor.

RECENT FINDINGS

Scientific understanding of the pathophysiologic basis of tremor disorders has grown considerably in recent years with the use of a broad range of neuroimaging approaches and rigorous, controlled postmortem studies. The basal ganglia and cerebellum are structures that seem to play a prominent role.

SUMMARY

The diagnosis of tremor disorders is challenging. The approach to tremor involves a history and a neurologic examination that is focused on the nuances of tremor phenomenology, of which there are many. The evaluation should begin with a tremor history and a focused neurologic examination. The examination should attend to the many subtleties of tremor phenomenology. Among other things, the history and examination are used to establish whether the main type of tremor is an action tremor (ie, postural, kinetic, or intention tremor) or a resting tremor. The clinician should then formulate two sets of differential diagnoses: disorders in which action tremor is the predominant tremor versus those in which resting tremor is the main tremor. Among the most common of the former type are essential tremor, enhanced physiologic tremor, drug-induced tremor, dystonic tremor, orthostatic tremor, and cerebellar tremor. Parkinson disease is the most common form of resting tremor, along with drug-induced resting tremor. This article details the clinical features of each of these as well as other tremor disorders.

Tremor

Tremor is a phenomenon observed in a broad spectrum of diseases with different pathophysiologies. While patients with tremor may not complain in the clinic of symptoms of imbalance, gait difficulties, or falls, laboratory research studies using quantitative analysis of gait and posture and neurophysiologic techniques have demonstrated impaired gait and balance across a variety of tremor etiologies. These findings have been supported by careful epidemiologic studies assessing symptoms of imbalance. Imaging and neurophysiologic studies have identified cerebellar networks as important mediators of tremor, and therefore a likely common site of dysfunction to explain the phenomenologic overlap between impaired postural and gait control with tremor. Further understanding of these mechanisms and networks is of crucial importance in the development of new treatments, particularly surgical or minimally invasive lesional therapies.

Pathogenesis of Primary Orthostatic Tremor: Current Concepts and Controversies

Background

Orthostatic tremor (OT), a rare and complex movement disorder, is characterized by rapid tremor of both legs and the trunk while standing. These disappear while the patient is either lying down or walking. OT may be idiopathic/primary or it may coexist with several neurological conditions (secondary OT/OT plus). Primary OT remains an enigmatic movement disorder and its pathogenesis and neural correlates are not fully understood.

Methods

A PubMed search was conducted in July 2017 to identify articles for this review.

Results

Structural and functional neuroimaging studies of OT suggest possible alterations in the cerebello-thalamo-cortical network. As with essential tremor, the presence of a central oscillator has been postulated for OT; however, the location of the oscillator within the tremor network remains elusive. Studies have speculated a possible dopaminergic deficit in the pathogenesis of primary OT; however, the evidence in favor of this concept is not particularly robust. There is also limited evidence favoring the concept that primary OT is a neurodegenerative disorder, as a magnetic resonance spectroscopic imaging study revealed significant reduction in cerebral and cerebellar N-acetyl aspartate (NAA) levels, a marker of neuronal compromise or loss.

Discussion

Based on the above, it is clear that the pathogenesis of primary OT still remains unclear. However, the available evidence most strongly favors the existence of a central oscillatory network, and involvement of the cerebellum and its connections.

Electrophysiological Investigations in Orthostatic Myoclonus: Preliminary Findings

We report the clinical and electrophysiological findings in seven patients with orthostatic myoclonus (OM) associated with gait initiation failure and falls. OM is one of the causes of unsteadiness of stance and gait, and it may develop as a symptom of neurodegenerative disorders. Both positive myoclonic bursts and negative myoclonus may be seen in electrophysiological recordings, and electrophysiological analysis suggests a subcortical origin for OM.

Smartphone Apps Provide a Simple, Accurate Bedside Screening Tool for Orthostatic Tremor

Background

Orthostatic Tremor (OT) is characterized by the presence of a sensation of instability while standing, associated with high frequency (13-18 Hz) lower extremity tremor. Diagnosis is confirmed with surface electromyography (EMG). An accurate screening tool that could be used in the routine clinical setting, without any specialized equipment, would be useful in earlier detection of OT and judicial use of additional testing.

Objective

The objective of this study was to evaluate OT diagnostic test characteristics at bedside using iPhone's built-in accelerometer and available applications for tremor recordings.

Methods

We obtained recordings using iPhones (Model 5, 5s, and 6) and free Applications ("LiftPulse" by LiftLabs [App1] and "iSeismometer" by ObjectGraph LLC [App2]) at default settings.

Results

24 EMG-confirmed OT subjects (mostly females, 22/24) and 15 age-matched controls (mostly males, 11/15) were evaluated. App1 detected OT range tremor in 22/24 patients and none of the controls. (Sensitivity = 92%, Specificity = 100%, NPV = 88%). App2 detected OT range tremor in 21/24 patients and in 1/13 controls (Sensitivity = 88%, Specificity = 92%, NPV = 80%). When combined, 24/24 patients and 1/13 controls had OT range tremor (Sensitivity = 100%, Specificity = 92%, NPV = 100%).

Conclusions

Smartphone apps that use the built-in accelerometer provide a simple, accurate and inexpensive bedside screening diagnostic tool for patients with OT.

Nonmotor Symptoms in Essential Tremor and Other Tremor Disorders

Tremor, like dystonia, is a term used at the phenomenological, syndromic, and aetiopathological level. Parkinsonian, essential, and dystonic tremor are the three most common tremor diagnoses encountered in clinical practice. Investigation of nonmotor symptoms in essential tremor and dystonic tremor syndromes is significantly hampered by the lack of clear clinical diagnostic criteria for these groups at a syndromic level, and the absence of biomarkers which allow definitive diagnosis at an aetiopathological level. Much work is needed in clarifying the motor features of these disorders in order to allow delineation of the nonmotor features of the most common tremor syndromes. With this limitation in mind, this chapter reviews what is known about nonmotor symptoms in these two tremor types. The final sections deal with nonmotor symptoms observed in patients with lesional tremor, thankfully a much more clearly defined albeit less common group of patients.

Pathological ponto-cerebello-thalamo-cortical activations in primary orthostatic tremor during lying and stance

Primary orthostatic tremor is a rare neurological disease characterized mainly by a high frequency tremor of the legs while standing. The aim of this study was to identify the common core structures of the oscillatory circuit in orthostatic tremor and how it is modulated by changes of body position. Ten patients with orthostatic tremor and 10 healthy age-matched control subjects underwent a standardized neurological and neuro-ophthalmological examination including electromyographic and posturographic recordings. Task-dependent changes of cerebral glucose metabolism during lying and standing were measured in all subjects by sequential ¹⁸F-fluorodeoxyglucose-positron emission tomography on separate days. Results were compared between groups and conditions. All the orthostatic tremor patients, but no control subject, showed the characteristic 13-18 Hz tremor in coherent muscles during standing, which ceased in the supine position. While lying, patients had a significantly increased regional cerebral glucose metabolism in the pontine tegmentum, the posterior cerebellum (including the dentate nuclei), the ventral intermediate and ventral posterolateral nucleus of the thalamus, and the primary motor cortex bilaterally compared to controls. Similar glucose metabolism changes occurred with clinical manifestation of the tremor during standing. The glucose metabolism was relatively decreased in mesiofrontal cortical areas (i.e. the medial prefrontal cortex, supplementary motor area and anterior cingulate cortex) and the bilateral anterior insula in orthostatic tremor patients while lying and standing. The mesiofrontal hypometabolism correlated with increased body sway in posturography. This study confirms and further elucidates ponto-cerebello-thalamo-primary motor cortical activations underlying primary orthostatic tremor, which presented consistently in a group of patients. Compared to other tremor disorders one characteristic feature in orthostatic tremor seems to be the involvement of the pontine tegmentum in the pathophysiology of tremor generation. High frequency oscillatory properties of pontine tegmental neurons have been reported in pathological oscillatory eye movements. It is remarkable that the characteristic activation and deactivation pattern in orthostatic tremor is already present in the supine position without tremor presentation. Multilevel changes of neuronal excitability during upright stance may trigger activation of the orthostatic tremor network. Based on the functional imaging data described in this study, it is hypothesized that a mesiofrontal deactivation is another characteristic feature of orthostatic tremor and plays a pivotal role in development of postural unsteadiness during prolonged standing.

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.

Lessons I have learned from my patients: everyday life with primary orthostatic tremor

Background

Primary orthostatic tremor is a rare disorder that is still under-diagnosed or misdiagnosed. Motor symptoms are fairly characteristics but the real impact on the patient’s every day life and quality of life is under-estimated. The ”how my patients taught me” format describes the impact on the patients’ every day life with their own words, which is rarely done.

Case presentation

A 46 year old lady was diagnosed primary orthostatic tremor (POT) based on the cardinal symptoms: feelings of instability, leg tremor and fear of falling in the standing position, improvement with walking and disappearance while sitting, frequency of Tremor in the 13–18Hz range, normal neurological examination. She gives illustrative examples of her disability in every day life activity (shower, public transportation, shopping). She reports how she felt stigmatized by her “invisible disorder”. As a consequence, she developed anxiety depression and social phobia. All these troubles are unknown or under recognized by doctors and family.

Conclusions

We review the clinical signs of POT that may help to increase the awareness of doctors and improve the diagnosis accuracy, based on the motor symptoms and description of the every day life disability, as reported by the patient. Non-motor symptoms (including somatic concerns, anxiety, depression, and social phobia) should be better considered in POT as they have a major impact on quality of life. Pharmacological treatments (clonazepam, gabapentin) may be helpful but have a limited effect over the years as the patients experience a worsening of their condition. On the long term follow-up, there are still unmet needs in POT, and new therapeutic avenues may be based on the pathophysiology by modulating the cerebello-thalamo-cortical network.

Electronic supplementary material

The online version of this article (doi:10.1186/s40734-016-0048-5) contains supplementary material, which is available to authorized users.

Thalamic-Caudal Zona Incerta Deep Brain Stimulation for Refractory Orthostatic Tremor: A Report of 3 Cases

Orthostatic tremor (OT) is a rare, disabling movement disorder characterized by the development of a high-frequency tremor of the lower limbs and feelings of unsteadiness upon standing, which compel the patient to sit down or walk. Medical therapy is often unsatisfactory. Previous reports suggest that deep brain stimulation of the ventral intermediate nucleus of the thalamus may improve clinical outcomes. The authors report 3 patients who had intractable orthostatic tremor treated with bilateral deep brain stimulation of the ventral intermediate nucleus of the thalamus-caudal zona incerta, resulting in improved and sustained clinical improvements in symptoms, although there were no apparent changes in the underlying tremor frequency or onset.

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.

In vivo neurometabolic profiling in orthostatic tremor

The pathogenesis of orthostatic tremor (OT) remains unclear, although some evidence points to dysfunction in the brainstem or cerebellum. We used single voxel proton magnetic resonance spectroscopy (1H-MRS) (3 T) to investigate whether neurochemical changes underlie abnormal cerebellar or cortical function in OT. Fourteen OT patients and 14 healthy controls underwent 1H-MRS studies with voxels placed in midparietal gray matter and cerebellum (vermis and central white matter). Spectral analysis was analyzed using the software package LCModel (version 6.3). The absolute metabolite concentrations and ratios of total N-acetylaspartate + N-acetylaspartyl glutamate (NAA), choline-containing compounds, myoinositol, and glutamate + glutamine to creatine were calculated. In midparietal gray matter spectra, we found a significant decrease in the absolute concentration of NAA in OT patients versus healthy controls (7.76 ± 0.25 vs 8.11 ± 0.45, P = 0.017). A similar decrease in NAA was seen in the cerebellar vermis (7.33 ± 0.61 vs 8.55 ± 1.54, P = 0.014) and cerebellar white matter (8.54 ± 0.79 vs 9.95 ± 1.57, P = 0.010). No differences in the other metabolites or their ratios were observed. Reductions in both cerebral cortical and cerebellar NAA suggest that there is neuronal damage or loss in OT, raising the intriguing question as to whether OT is a neurodegenerative disease. Along with clinical history and electrophysio0logical examination, 1H-MRS could serve as a useful diagnostic aid for OT.

Long-term follow-up of chronic spinal cord stimulation for medically intractable orthostatic tremor

Orthostatic tremor (OT) is a rare form of tremor occurring in the legs when standing upright. Medical treatment frequently is unsatisfactory, thus in selected cases, surgical treatment, such as spinal cord stimulation (SCS) or thalamic deep brain stimulation has been proposed. We report the long-term results (follow-up (FU) 34-133 months) of SCS in four patients with medically intractable OT. Outcome was assessed by recording the time tolerated to stand still pre- and post-operatively and by a patient self-rating (PSR) scale (0 = poor to 6 = excellent). Furthermore, surface electromyography (EMG) recordings of different leg muscles were performed to estimate tremor activity with and without SCS post-operatively. With chronic SCS, all four patients showed an improvement of unsteadiness occurring in the presence of stimulation-induced paraesthesia of the legs. The mean standing time improved from 51 s (SD 47 s, range 4-120 s) pre-operatively to 220 s (SD 184 s, range 10-480 s) with SCS at last available FU. Tremor activity in the EMG of the anterior tibial muscle was reduced by 30-60 % with SCS compared with off SCS. PSR score was 4 or 5 in three patients and 3 in the other. In conclusion, SCS is an effective long-term treatment option in patients with otherwise intractable OT.

Resting state functional MRI reveals abnormal network connectivity in orthostatic tremor

Very little is known about the pathogenesis of orthostatic tremor (OT). We have observed that OT patients might have deficits in specific aspects of neuropsychological function, particularly those thought to rely on the integrity of the prefrontal cortex, which suggests a possible involvement of frontocerebellar circuits. We examined whether resting-state functional magnetic resonance imaging (fMRI) might provide further insights into the pathogenesis on OT. Resting-state fMRI data in 13 OT patients (11 women and 2 men) and 13 matched healthy controls were analyzed using independent component analysis, in combination with a "dual-regression" technique, to identify group differences in several resting-state networks (RSNs). All participants also underwent neuropsychological testing during the same session. Relative to healthy controls, OT patients showed increased connectivity in RSNs involved in cognitive processes (default mode network [DMN] and frontoparietal networks), and decreased connectivity in the cerebellum and sensorimotor networks. Changes in network integrity were associated not only with duration (DMN and medial visual network), but also with cognitive function. Moreover, in at least 2 networks (DMN and medial visual network), increased connectivity was associated with worse performance on different cognitive domains (attention, executive function, visuospatial ability, visual memory, and language). In this exploratory study, we observed selective impairments of RSNs in OT patients. This and other future resting-state fMRI studies might provide a novel method to understand the pathophysiological mechanisms of motor and nonmotor features of OT.

Orthostatic tremor: a cerebellar pathology?

SEE MUTHURAMAN ET AL DOI101093/AWW164 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: Primary orthostatic tremor is characterized by high frequency tremor affecting the legs and trunk during the standing position. Cerebellar defects were suggested in orthostatic tremor without direct evidence. We aimed to characterize the anatomo-functional defects of the cerebellar motor pathways in orthostatic tremor. We used multimodal neuroimaging to compare 17 patients with orthostatic tremor and 17 age- and gender-matched healthy volunteers. Nine of the patients with orthostatic tremor underwent repetitive transcranial stimulation applied over the cerebellum during five consecutive days. We quantified the duration of standing position and tremor severity through electromyographic recordings. Compared to healthy volunteers, grey matter volume in patients with orthostatic tremor was (i) increased in the cerebellar vermis and correlated positively with the duration of the standing position; and (ii) increased in the supplementary motor area and decreased in the lateral cerebellum, which both correlated with the disease duration. Functional connectivity between the lateral cerebellum and the supplementary motor area was abnormally increased in patients with orthostatic tremor, and correlated positively with tremor severity. After repetitive transcranial stimulation, tremor severity and functional connectivity between the lateral cerebellum and the supplementary motor area were reduced. We provide an explanation for orthostatic tremor pathophysiology, and demonstrate the functional relevance of cerebello-thalamo-cortical connections in tremor related to cerebellar defects.

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.

Bilateral Ventral Intermediate Nucleus Thalamic Deep Brain Stimulation in Orthostatic Tremor

BACKGROUND

Orthostatic tremor (OT) is characterized by high-frequency leg tremor when standing still, resulting in a sense of imbalance, with limited treatment options. Ventral intermediate (Vim) nucleus thalamic deep brain stimulation (DBS) has been reported as beneficial in a few cases.

OBJECTIVE

To report clinical outcomes, lead locations, and stimulation parameters in 2 patients with severe medication-refractory OT treated with Vim DBS.

METHODS

The patients underwent surface electromyography (EMG) to confirm the OT diagnosis. Outcomes were measured as change in tolerated standing time at the last follow-up. Lead locations were quantified using postoperative MRI.

RESULTS

Vim DBS was well tolerated and resulted in improvement in standing time (patient 1: 50 s at baseline to 15 min 16 months after surgery; patient 2: 34 s at baseline to 4.2 min 7 months after surgery). Postoperative surface EMG for patient 1 demonstrated a delayed onset of tremor, lower-amplitude tremor, and periods of quiescence, but an unchanged tremor frequency.

CONCLUSION

These cases provide further support for Vim DBS to improve standing time in severe medication-refractory OT. The location of the effective thalamic target for OT does not differ from the effective target for essential tremor.

Dystonia Associated with Idiopathic Slow Orthostatic Tremor

BACKGROUND

We aimed to characterize the clinical and electrophysiological features of patients with slow orthostatic tremor.

CASE REPORT

The clinical and neurophysiological data of patients referred for lower limb tremor on standing were reviewed. Patients with symptomatic or primary orthostatic tremor were excluded. Eight patients were identified with idiopathic slow 4-8 Hz orthostatic tremor, which was associated with tremor and dystonia in cervical and upper limb musculature. Coherence analysis in two patients showed findings different to those seen in primary orthostatic tremor.

DISCUSSION

Slow orthostatic tremor may be associated with dystonia and dystonic tremor.

Cognitive and neuropsychiatric features of orthostatic tremor: A case-control comparison

INTRODUCTION

Evidence suggests that the cerebellum could play a role in the pathophysiology of orthostatic tremor. The link between orthostatic tremor and the cerebellum is of interest, especially in light of the role the cerebellum plays in cognition, and it raises the possibility that orthostatic tremor patients could have cognitive deficits consistent with cerebellar dysfunction. Our aim was to examine whether orthostatic tremor patients had cognitive deficits and distinct personality profiles when compared with matched controls.

METHODS

Sixteen consecutive orthostatic tremor patients (65.7 ± 13.3 years) and 32 healthy matched controls underwent a neuropsychological battery and the Personality Assessment Inventory. In linear regression models, the dependent variable was each one of the neuropsychological test scores or the Personality Assessment Inventory subscales and the independent variable was orthostatic tremor vs.

RESULTS

Adjusted for age in years, sex, years of education, comorbidity index, current smoker, and depressive symptoms, diagnosis (orthostatic tremor vs. healthy control) was associated with poor performance on tests of executive function, visuospatial ability, verbal memory, visual memory, and language tests, and on a number of the Personality Assessment Inventory subscales (somatic concerns, anxiety related disorders, depression, and antisocial features). Older-onset OT (>60 years) patients had poorer scores on cognitive and personality testing compared with their younger-onset OT counterparts.

CONCLUSION

Orthostatic tremor patients have deficits in specific aspects of neuropsychological functioning, particularly those thought to rely on the integrity of the prefrontal cortex, which suggests involvement of frontocerebellar circuits. Cognitive impairment and personality disturbances could be disease-associated nonmotor manifestations of orthostatic tremor.

The long-term outcome of orthostatic tremor

OBJECTIVES

Orthostatic tremor is a rare condition characterised by high-frequency tremor that appears on standing. Although the essential clinical features of orthostatic tremor are well established, little is known about the natural progression of the disorder. We report the long-term outcome based on the largest multicentre cohort of patients with orthostatic tremor.

METHODS

Clinical information of 68 patients with clinical and electrophysiological diagnosis of orthostatic tremor and a minimum follow-up of 5 years is presented.

RESULTS

There was a clear female preponderance (76.5%) with a mean age of onset at 54 years. Median follow-up was 6 years (range 5-25). On diagnosis, 86.8% of patients presented with isolated orthostatic tremor and 13.2% had additional neurological features. At follow-up, seven patients who initially had isolated orthostatic tremor later developed further neurological signs. A total 79.4% of patients reported worsening of orthostatic tremor symptoms. These patients had significantly longer symptom duration than those without reported worsening (median 15.5 vs 10.5 years, respectively; p=0.005). There was no change in orthostatic tremor frequency over time. Structural imaging was largely unremarkable and dopaminergic neuroimaging (DaTSCAN) was normal in 18/19 cases. Pharmacological treatments were disappointing. Two patients were treated surgically and showed improvement.

CONCLUSIONS

Orthostatic tremor is a progressive disorder with increased disability although tremor frequency is unchanged over time. In most cases, orthostatic tremor represents an isolated syndrome. Drug treatments are unsatisfactory but surgery may hold promise.

Orthostatic tremor: Clinical, electrophysiologic, and treatment findings in 184 patients

OBJECTIVE

To evaluate the clinical, electrophysiologic, and treatment outcome features of orthostatic tremor (OT) in a large case series.

METHODS

We performed medical record review of 184 patients who met clinical and electrodiagnostic criteria for OT from 1976 to 2013 at the Mayo Clinic. Demographic, clinical, electrophysiologic, and treatment data were extracted.

RESULTS

The majority of OT cases were female (63.6%) and mean age at onset was 59.3 years (range 13-85 years). Diagnosis was delayed by a mean of 7.2 years (range 0-44 years). The average tremor frequency was 15.7 Hz (range 12.5-20 Hz), and transmitted to the arms on weight-bearing (95.5%). Patients reported a spectrum of progressive orthostatic leg symptoms, relieved by sitting or leaning. Falls were reported in 24.1%. Coexistent neurologic disorders included essential tremor (22.8%), other tremor (4.9%), and parkinsonism (8.7%). Family history of OT was noted in 4.9%. Of 46 medications trialed, 24 failed to provide any benefit. Benzodiazepines provided at least mild benefit in 55.9%, and moderate to marked benefit in 31.5%; β-blockers (31.0%) and anticonvulsants (25.0%) provided mild benefit, and the remainder were largely ineffective. Medication benefit waned over time. Deep brain stimulation (DBS) was effective in 2 cases.

CONCLUSION

OT predominantly affects female seniors, and the diagnosis should be considered with any orthostatic-induced leg symptoms, and confirmed by surface EMG. Benzodiazepines are the most efficacious treatment, followed by β-blockers and anticonvulsants. DBS should be further explored for treatment.