Fast orthostatic tremor in Parkinson's disease mimicking primary orthostatic tremor.

Leg tremor during standing is a rare feature in idiopathic Parkinson's disease (PD). Tremor during standing usually has a low frequency (range, 4-6 Hz), similar to PD rest tremor frequency, and is improved by levodopa. We describe three cases of fast orthostatic tremor (FoT) of legs and trunk mimicking primary orthostatic tremor (OT) in patients treated with levodopa for PD. Asymmetrical akinetorigid syndrome was accompanied by a rest tremor in two cases. We obtained electrophysiological parameters by electromyographic (EMG) polygraphic recording after 16 hours withdrawal of antiparkinsonian treatment and at the maximal effect of levodopa in order to investigate the effect of dopaminergic stimulation upon such cases of orthostatic tremor in PD. Electrophysiological parameters of orthostatic tremor, especially frequency (range 14-18 Hz), were similar to that seen in POT. Severity of tremor was independent of seriousness and duration of PD. Levodopa had no effect either on the handicap due to OT or on the amplitude and frequency of the EMG OT activity. In contrast, mild improvement of OT was obtained with benzodiazepines in two cases and parkinsonian syndrome was levodopa-sensitive. These findings suggest that FoT in PD would not be directly controlled by the dopaminergic system. However, increased rhythmicities in basal ganglia or in cerebello-thalamic loops at the rapid frequencies range seen in PD could favor the emergence of a primary orthostatic tremor-like tremor in PD patients.     

Successful thalamic deep brain stimulation for orthostatic tremor

We report a patient with severe orthostatic tremor (OT) unresponsive to pharmacological treatments that was successfully controlled with thalamic (Vim, ventralis intermedius nucleus) deep brain stimulation (DBS) over a 4‐year period. Cortical activity associated with the OT revealed by EEG back‐averaging and fluoro‐deoxi‐glucose PET were also suppressed in parallel with tremor arrest. This case suggests that Vim‐DBS may be a useful therapeutic approach for patients highly disabled by OT. © 2008 Movement Disorder Society     

Chronic spinal cord stimulation in medically intractable orthostatic tremor

Background

Orthostatic tremor with its sense of unsteadiness when standing may have a devastating effect on affected persons. Currently, there are no other treatment options in those who do not respond or who do not tolerate medical treatment.

Objectives

To report on a pilot study on spinal cord stimulation in medically intractable orthostatic tremor.

Methods

Chronic spinal cord stimulation (SCS) was performed in two patients with medically‐intractable orthostatic tremor via quadripolar plate electrodes implanted at the lower thoracic spine. The electrodes were connected to implantable pulse generators.

Results

Subjective and objective improvement of unsteadiness was achieved within a frequency range of 50 to 150 Hz, and occurred in the presence of stimulation‐induced paraesthesia. With optimized stimulation settings polygraphic electromyelogram (EMG) recordings continued to show the typical 14–16 Hz EMG activity. The beneficial effect of SCS was maintained at long‐term follow‐up.

Conclusions

The results of this pilot study indicate that SCS may be an option in patients with otherwise intractable orthostatic tremor.Orthostatic tremor is a rare condition that was first described by Heilman¹ in 1984. It is characterised by an intense and disabling sensation of unsteadiness when standing quiet, accompanied by a 13–18‐Hz tremor of the lower limbs.^2,3 The tremor and the feeling of unsteadiness are relieved by walking, sitting or lying down. The ability to stand still without help may range between a few seconds and a few minutes depending on the severity of the condition. Although patients rarely fall down, the sensation of unsteadiness may have a devastating effect interfering markedly with quality of life.⁴ Electromyelogram (EMG) recordings show a typical burst activation pattern with a high coherence between unilateral and contralateral muscles. The tremor can occur also in the upper limbs with sustained isometric contraction and in muscles of the trunk. It is thought that orthostatic tremor is driven by a central oscillator, but the pathophysiological mechanisms have not been definitely clarified.^5,6 Medical treatment with a variety of drugs such as clonazepam, levodopa and primidone is considered to be the treatment of choice. A recent study,³ however, has shown that the overall response to medical treatment is poor. Thus far, there are no other therapeutical options in those patients with orthostatic tremor who do not benefit from medical treatment or who have side effects.In the past few years, chronic neurostimulation techniques have proved to be beneficial in a variety of movement disorders.^7,8,9 Current targets for deep‐brain stimulation include the thalamus, subthalamic nucleus and pallidum. Spinal cord stimulation (SCS) is mainly used nowadays for the treatment of medically refractory pain,^10,11,12 but it has been thought to be of interest for the treatment of tremors also.¹³ Here, we report on a pilot study on the use of SCS in otherwise intractable orthostatic tremor.     

Proprioceptive muscle tendon stimulation reduces symptoms in primary orthostatic tremor

Introduction

Primary orthostatic tremor (OT) is characterized by high-frequency lower limb muscle contractions and a disabling sense of unsteadiness while standing. To date, therapeutic options for OT are limited. Here, we examined the effects of proprioceptive leg muscle stimulation via muscle tendon vibration (MTV) on tremor and balance control in patients with primary OT.

Methods

Tremor in nine patients with primary OT was examined during four conditions: standing (1), standing with MTV on the bilateral soleus muscles (2), lying (3), and lying with MTV (4). Tremor characteristics were assessed by frequency domain analysis of surface EMG recordings from four leg muscles. Body sway was analyzed using posturographic recordings.

Results

During standing, all patients showed a coherent high-frequency tremor in leg muscles and body sway that was absent during lying (p?<?0.001). MTV during standing did not reset tremor frequency, but resulted in a decreased tremor intensity (p?<?0.001; mean reduction: 32.5?±?7.1%) and body sway (p?=?0.032; mean reduction: 37.2?±?6.8%). MTV did not affect muscle activity during lying. Four patients further reported a noticeable relief from unsteadiness during stimulation.

Conclusion

Proprioceptive stimulation did not reset tremor frequency consistent with the presumed central origin of OT. However, continuous MTV influenced the emergence of OT symptoms resulting in reduced tremor intensity, improved posture, and a relief from unsteadiness in half of the examined patients. These findings indicate that MTV either directly interferes with the peripheral manifestation of the central oscillatory pattern or prevents proprioceptive afferent feedback from becoming extensively synchronized at the tremor frequency.

     

Modulation of primary orthostatic tremor by magnetic stimulation over the motor cortex

OBJECTIVES—To study the role of corticomotorneuronal pathways in primary orthostatic tremor.
METHODS—Transcranial magnetic stimuli at anintensity 10% above the resting motor threshold were delivered overthe leg motor cortex in two patients with primary orthostatic tremorwhile standing still. Electromyographic responses in both tibialisanterior muscles were recorded after 20 stimuli given randomly atintervals of 120 to 180 seconds. Differences between predictedand actual times of occurrence of tremor bursts after the stimuli wereused to calculate a resetting index, with a value of 0 representing no resetting and a value of 1 representing complete resetting.
RESULTS—Transcranial magnetic stimulation evokedEMG responses in both tibialis anterior muscles, followed by transientsuppression of tremor before reappearance of rhythmic EMG activity.Analysis of the timing of tremor bursts from EMG recordings before and after the magnetic stimuli disclosed that the phase of orthostatic tremor could be reset by brain stimulation (mean resetting indices 0.93 and 0.82).
CONCLUSION—The results suggest that a centraloscillator, involving the motor cortex, has a crucial role in eitherthe generation or modulation of orthostatic tremor.

     

The physiology of orthostatic tremor

This article describes the physiological findings in a patient with orthostatic tremor. The tremor primarily affected the legs, was alternating between antagonist muscle groups, and had a remarkably rapid frequency of 16 Hz. It was present only during certain postures and appeared to be of central origin. A tremor of the same frequency was also recorded in the arms during particular movements, but was cocontracting. We suggest that orthostatic tremor may be generated by spontaneous oscillation in those central structures responsible for organizing the motor programs for standing.     

Resetting of orthostatic tremor associated with cerebellar cortical atrophy by transcranial magnetic stimulation

OBJECTIVES: To investigate the resetting effects of transcranial magnetic stimulation over motor cortex on orthostatic tremor, characterized by high-frequency electromyographic discharges in weight-bearing muscles, particularly orthostatic tremor (OT) associated with cerebellar cortical atrophy; and to compare our results with those obtained in primary OT, for which transcranial magnetic stimulation does not reset tremor. DESIGN: Study of 3 patients who clinically exhibited a sporadic pancerebellar syndrome associated with isolated cerebellar atrophy and features of OT. SETTING: Research hospital. MAIN OUTCOME MEASURES: Electromyograms and transcranial magnetic stimulation studies with a resetting index calculated on the basis of the timing of measured bursts and predicted bursts for a magnetic stimulus given at increasing delays. RESULTS: Surface electromyographic recordings in weight-bearing muscles showed tremor with a frequency of 14, 15, and 14 Hz in the 3 patients. Transcranial magnetic stimulus was able to reset OT. Resetting index was 0.72. CONCLUSIONS: Transcranial magnetic stimulus resets OT associated with cerebellar cortical atrophy, emphasizing the role of motor cortex in the genesis of OT associated with a cerebellar dysfunction. Our results argue in favor of a distinct pathophysiological mechanism of primary OT and OT associated with cerebellar cortical atrophy.     

Zona incerta deep-brain stimulation in orthostatic tremor: efficacy and mechanism of improvement

Journal of Neurology - Orthostatic tremor is a rare hyperkinetic movement disorder that is characterized by a 13–18&nbsp;Hz tremor in both legs while standing. Deep-brain stimulation of...     

Effect of stimulation frequency on tremor suppression in essential tremor.

We sought to determine the effect of deep brain stimulation (DBS) frequency on tremor suppression in essential tremor (ET) patients with deep brain stimulators implanted in the ventral intermediate nucleus (VIM) of the thalamus. A uniaxial accelerometer was used to measure tremor in the right upper extremity of subjects with a diagnosis of ET who had DBS electrodes implanted in the left VIM. The root-mean-square acceleration was used as the index of tremor magnitude and normalized to the OFF DBS condition. There was a highly significant inverse sigmoidal relationship between stimulation frequency and normalized tremor acceleration (X(2)/DoF = 0.42, r(2) = 0.997). Tremor acceleration had a nearly linear response to stimulation frequencies between 45 and 100 Hz with little additional benefit above 100 Hz. These findings have two important implications. Clinically, frequency of thalamic stimulation is an important variable for optimal tremor control with maximal benefit achieved with 100 to 130 Hz in most patients. Second, thalamic DBS provides tremor benefit in a graded manner and is not an all-or-nothing phenomenon.     

A case of orthostatic tremor in parkinsonism

A 79-year-old woman presenting with orthostatic tremor (OT) was reported. In addition to OT, neurological examination showed mild dementia, bradykinesia, rigidity of the neck and the upper limbs and positive Babinski reflex on the left. These clinical signs and CT as well as MRI findings suggested vascular parkinsonism as its pathological background. Upon standing with her feet together, she rapidly developed rhythmic repetitive contraction of all leg muscles. The shaking disappeared by walking, sitting, or lying down. The EMG recording revealed 4-Hz tremor which consisted of alternating contraction of anti-gravity muscles and their antagonists. The EMG bursts associated with the tremor were synchronous in corresponding muscles of both legs. OT could be bilaterally reset by unilateral voluntary or passive movement of leg. In the supine position, the tremor was not evoked by voluntary contraction of leg muscles against resistance. As the tremor was aggravated by the administration of haloperidol was suppressed by L-DOPA, it was thought to have the pharmacological basis common to the resting tremor of parkinsonism. Furthermore, we postulated that the postural tonus-regulating system, which is thought to set and maintain the tonus of antigravity muscles for standing upright, might be involved in the generation of the rhythmic discharge pattern (reciprocal bursts in a given leg and synchronized bursts in both legs) of OT.     

The central oscillatory network of orthostatic tremor

Orthostatic tremor (OT) is a movement disorder of the legs and trunk that is present in the standing position but typically absent when sitting. The pathological central network involved in orthostatic tremor is still unknown. In this study we analyzed 15 patients with simultaneous high‐resolution electroencephalography and electromyography recording to assess corticomuscular coherence. In 1 patient we were able to simultaneously record the local field potential in the ventrolateral thalamus and electroencephalography. Dynamic imaging of coherent source analysis was used to find the sources in the brain that are coherent with the peripheral tremor signal. When standing, the network for the tremor frequency consisted of unilateral activation in the primary motor leg area, supplementary motor area, primary sensory cortex, two prefrontal/premotor sources, thalamus, and cerebellum for the whole 30‐second segment recorded. The source coherence dynamics for the primary leg area and the thalamic source signals with the tibialis anterior muscle showed that they were highly coherent for the whole 30 seconds for the contralateral side but markedly decreased after 15 seconds for the ipsilateral side. The source signal and the recorded thalamus signal followed the same time frequency dynamics of coherence in 1 patient. The corticomuscular interaction in OT follows a consistent pattern with an initially bilateral pattern and then a segregated unilateral pattern after 15 seconds. This may add to the feeling of unsteadiness. It also makes the thalamus unlikely as the main source of orthostatic tremor. © 2013 International Parkinson and Movement Disorder Society