Thalamic tremor: case reports and implications of the tremor-generating mechanism

White Matter Hyperintensities Are Associated With Severity of Essential Tremor in the Elderly

Background: Essential tremor (ET) occurs with steeply increasing prevalence in the elderly, and apart from disease duration, age is independently associated with an increase of tremor amplitude and a decrease of frequency. White matter hyperintensities (WMHs) are a common finding in the elderly, and their role in the pathophysiology of ET is unknown. The aims of this study were to examine whether ET patients differ in their total or region-specific WMH volumes from healthy controls and to determine the impact of WMH on tremor characteristics. Methods: A total of 47 elderly ET patients with a mean age of 72 years and 39 age-matched healthy controls underwent a thorough clinical assessment and 3T MRI. Total WMH volumes were derived from T2-weighted fluid-attenuated inversion recovery (FLAIR) MR images. Additionally, region of interest-based WMH volumes for the Johns Hopkins University (JHU) white matter tracts and labels were calculated, and WMHs were assessed semiquantitatively using the Fazekas scale. Results: Essential tremor patients and healthy controls did not differ in their total or tract-specific WMH volumes or Fazekas scores. However, WMH volume was significantly positively correlated with tremor severity on the TETRAS scale, and there was a significant negative correlation with the mean accelerometric tremor frequency. In a multiple linear regression model including disease duration, age, and age-adjusted total WMH volume, only the WMH volume significantly predicted tremor severity, while age and disease duration were not significant. Conclusion: We found evidence for a direct association between WMH volume and tremor severity. If confirmed by larger studies, our findings could explain the well-known relation between age and tremor severity.

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.

Thalamic versus midbrain tremor; two distinct types of Holmes' Tremor: a review of 17 cases

INTRODUCTION

Holmes Tremor (HT) is a unique and debilitating movement disorder. It usually results from lesions of the midbrain and its connection but can also result from posterior thalamic injury. Clinical examination can help lesion localization between these two areas. We studied the clinical features and their radiological correlations to distinguish midbrain HT (HT-m) from thalamic HT (HT-t).

METHODS

Retrospective review of 17 patients with a HT-type presentation was conducted. Tremor characteristics, associated clinical signs and radiological findings were studied.

RESULTS

Eleven patients had a myorythmic rest tremor, large amplitude proximal tremor with goal-directed worsening, with or without mild distal dystonic posturing, representing HT-m. Six patients had slow, large amplitude proximal tremors and distal choreathetoid movements, significant proximal/distal dystonic posturing, associated with proprioceptive sensory loss, representing HT-t. Haemorrhagic lesions were the predominant cause of HT-m; whereas, ischaemia was more commonly associated with HT-t.

CONCLUSION

When assessing patients with HT, attentiveness to the presence of associated signs in the affected limb, such as a proprioceptive sensory deficits and additional movement disorders, can aid lesion localisation, which can have implications for management.

Holmes Tremor Partially Responsive to Topiramate: A Case Report

Background

Holmes tremor is a rare symptomatic movement disorder, characterized by a combination of resting, postural, and intention tremor. It is usually caused by lesions in the brainstem, thalamus, and cerebellum. Despite pharmacological advances, its treatment remains a challenge; many medications have been used with various degrees of effectiveness. Stereotactic thalamotomy and deep brain stimulation in the ventralis intermedius nucleus have been effective surgical procedures in cases refractory to medical treatment.

Case Report

Here we report a young woman with topiramate-responsive Holmes tremor secondary to a brainstem cavernoma.

Discussion

Herein we report a Holmes tremor responsive to Topiramate.

Post-Thalamic Stroke Movement Disorders: A Systematic Review

BACKGROUND

After a stroke, movement disorders are rare manifestations mainly affecting the deep structures of the brain like the basal ganglia (44%) and thalamus (37%), although there have been case studies of movement disorders in strokes affecting the cerebral cortex also.

SUMMARY

This review aims to delineate the various movement disorders seen in association with thalamic strokes and tries to identify the location of the nuclei affected in each of the described movement disorders. Cases were identified through a search of PubMed database using different search terms related to post-thalamic stroke movement disorders and a secondary search of references of identified articles. We reviewed 2,520 research articles and only 86 papers met the inclusion criteria. Cases were included if they met criteria for post-thalamic stroke movement disorders. Case-cohort studies were also reviewed and will be discussed further. Key Messages: The most common post-stroke abnormal movement disorder reported in our review was dystonia followed by hemiataxia. There was a higher association between ischaemic stroke and movement disorder. Acute onset movement disorders were more common than delayed. The posterolateral thalamus was most commonly involved in post-thalamic stroke movement disorders.

Tremor Secondary to a Thalamic Glioma: A Case Report

BACKGROUND AND IMPORTANCE

Tremor is the most prevalent movement disorder. While the exact pathophysiology remains to be elucidated, the importance of the thalamus in tremor circuitry is well recognized. Thalamic lesions from demyelination, trauma, ischemia, or neoplasm rarely cause isolated tremor. We report the case of a patient presenting with a tremor secondary to a thalamic grade II astrocytoma that improved with treatment.

CLINICAL PRESENTATION

A 50-yr-old male presented with a 1-yr history of right-hand tremor. The presence of long tract signs prompted imaging that revealed a lesion within the left thalamus. Stereotactic biopsy revealed a World Health Organization grade II astrocytoma. Prior to biopsy, the patient's tremor was graded using the Clinical Rating Scale for Tremor. Immediately postoperatively the patient remained at his neurological baseline without improvement in his tremor. Subsequent fractionated radiotherapy with concomitant temozolomide followed by adjuvant temozolomide led to radiographic response as well as clinical improvement. The patient reported less tremor, which was confirmed objectively with improved Clinical Rating Scale for Tremor scores at 6 and 12 mo postoperatively.

CONCLUSION

This case of a thalamic glioma presenting with isolated contralateral tremor highlights the role of the thalamus in the development of tremor. Moreover, this particular case contrasts with other published reports on the lack of additional symptoms and tremor response to chemoradiation.

Post-stroke Movement Disorders: The Clinical, Neuroanatomic, and Demographic Portrait of 284 Published Cases

PURPOSE

Abnormal movements are a relatively uncommon complication of strokes. Besides the known correlation between stroke location and certain movement disorders, there remain uncertainties about the collective effects of age and stroke mechanism on phenomenology, onset latency, and outcome of abnormal movements.

MATERIALS AND METHODS

We systematically reviewed all published cases and case series with adequate clinical-imaging correlations. A total of 284 cases were analyzed to evaluate the distribution of different movement disorders and their association with important cofactors.

RESULTS

Posterolateral thalamus was the most common region affected (22.5%) and dystonia the most commonly reported movement disorder (23.2%). The most common disorders were parkinsonism (17.4%) and chorea (17.4%) after ischemic strokes and dystonia (45.5%) and tremor (19.7%) after hemorrhagic strokes. Strokes in the caudate and putamen were complicated by dystonia in one third of the cases; strokes in the globus pallidus were followed by parkinsonism in nearly 40%. Chorea was the earliest poststroke movement disorder, appearing within hours, whereas dystonia and tremor manifested several months after stroke. Hemorrhagic strokes were responsible for most delayed-onset movement disorders (>6 months) and were particularly overrepresented among younger individuals affected by dystonia.

CONCLUSIONS

This evidence-mapping portrait of poststroke movement disorders will require validation or correction based on a prospective epidemiologic study. We hypothesize that selective network vulnerability and resilience may explain the differences observed in movement phenomenology and outcomes after stroke.

Tremors: Essential Tremor and Beyond

Tremor is a fairly common movement disorder presenting to an outpatient pediatric neurology practice. Tremors can be primary or secondary to underlying neurologic or systemic diseases. When assessing a child with tremor, it is paramount to evaluate the phenomenology of the tremor, determine the presence or absence of other neurologic signs and symptoms, and the possible modifying influence of medications. Proper classification is essential for specific diagnosis and prompt adequate management. Treatment considerations should take into account objective assessment of tremor severity and the degree of disability or impairment experienced by the child. Overall effectiveness of pharmacologic treatments of tremor is unfortunately disappointing. In this article we review the clinical examination, classification, and diagnosis of tremor. The pathophysiology of the different forms of tremor is outlined, and treatment options are discussed.

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.

Movement Disorders Following Cerebrovascular Lesion in the Basal Ganglia Circuit

Movement disorders are primarily associated with the basal ganglia and the thalamus; therefore, movement disorders are more frequently manifest after stroke compared with neurological injuries associated with other structures of the brain. Overall clinical features, such as types of movement disorder, the time of onset and prognosis, are similar with movement disorders after stroke in other structures. Dystonia and chorea are commonly occurring post-stroke movement disorders in basal ganglia circuit, and these disorders rarely present with tremor. Rarer movement disorders, including tic, restless leg syndrome, and blepharospasm, can also develop following a stroke. Although the precise mechanisms underlying the pathogenesis of these conditions have not been fully characterized, disruptions in the crosstalk between the inhibitory and excitatory circuits resulting from vascular insult are proposed to be the underlying cause. The GABA (gamma-aminobutyric acid)ergic and dopaminergic systems play key roles in post-stroke movement disorders. This review summarizes movement disorders induced by basal ganglia and thalamic stroke according to the anatomical regions in which they manifest.

A rare case of movement disorder in Intensive Care Unit

Hemichorea-hemiballismus syndrome (HCHB represents a peculiar form of hyperkinetic movement disorder with varying degrees of chorea and/or ballistic movements on one side of body. The patients are conscious of their environment but unable to control the movements. HCHB is a rare occurrence in acute stroke patients. Patients with sub-cortical strokes are more prone to develop movement disorders than with cortical stroke. We report one such interesting case here posing difficulties in management and intensive care of the patient. The patient remained refractory to all the drugs described in literature, and adequate control of the hyperkinetic movements could be achieved only with continuous intravenous sedation.

Movement disorders in cerebrovascular disease

Movement disorders can occur as primary (idiopathic) or genetic disease, as a manifestation of an underlying neurodegenerative disorder, or secondary to a wide range of neurological or systemic diseases. Cerebrovascular diseases represent up to 22% of secondary movement disorders, and involuntary movements develop after 1-4% of strokes. Post-stroke movement disorders can manifest in parkinsonism or a wide range of hyperkinetic movement disorders including chorea, ballism, athetosis, dystonia, tremor, myoclonus, stereotypies, and akathisia. Some of these disorders occur immediately after acute stroke, whereas others can develop later, and yet others represent delayed-onset progressive movement disorders. These movement disorders have been encountered in patients with ischaemic and haemorrhagic strokes, subarachnoid haemorrhage, cerebrovascular malformations, and dural arteriovenous fistula affecting the basal ganglia, their connections, or both.

Dystonia and tremor secondary to a pediatric thalamic stroke

A previously healthy 10-year-old girl developed a right hemiparesis with sensory loss secondary to a posterolateral thalamic infarct. Despite improvement in strength, three weeks later a 4 Hz kinetic tremor appeared in the right hand accompanied by dystonia in the right upper and lower limbs. Basal ganglia vascular lesions are rare in childhood and movement disorders secondary to such lesions even more so. A thorough work-up failed to disclose the etiology. Our patient illustrates that dystonia and tremor secondary to posterolateral thalamic infarctions are also apt to occur in children and, unlike the adult picture, abnormal movements may develop very soon after the insult.

Post-stroke Movement Disorders: Clinical Manifestations and Pharmacological Management

Involuntary abnormal movements have been reported after ischaemic and haemorrhagic stroke. Post stroke movement disorders can appear as acute or delayed sequel. At the moment, for many of these disorders the knowledge of pharmacological treatment is still inadequate. Dopaminergic and GABAergic systems may be mainly involved in post-stroke movement disorders. This article provides a review on drugs commonly used in post-stroke movement disorders, given that some post-stroke movement disorders have shown a partial benefit with pharmacological approach.

Milestones in tremor research

Tremor is one of the most frequent movement disorders and covers a wide spectrum of entities summarized in the 1998 consensus statement of the Movement Disorder Society. Essential tremor and Parkinson tremor are most common and are also the most thoroughly studied. Major progress has occurred in the clinical semiology, neuroimaging, epidemiology, and pathophysiology of tremors. Pathology and genetic research are rapidly growing fields of study. Recently described tremor entities include orthostatic tremor, dystonic tremor, cortical tremor, and thalamic tremor. Treatment research methodology has improved substantially, but few double-blind controlled trials have been published. Deep brain stimulation is the most effective treatment for most tremors but is reserved for advanced cases.

The functional neuroanatomy of dystonia

Dystonia is a neurological disorder characterized by involuntary twisting movements and postures. There are many different clinical manifestations, and many different causes. The neuroanatomical substrates for dystonia are only partly understood. Although the traditional view localizes dystonia to basal ganglia circuits, there is increasing recognition that this view is inadequate for accommodating a substantial portion of available clinical and experimental evidence. A model in which several brain regions play a role in a network better accommodates the evidence. This network model accommodates neuropathological and neuroimaging evidence that dystonia may be associated with abnormalities in multiple different brain regions. It also accommodates animal studies showing that dystonic movements arise with manipulations of different brain regions. It is consistent with neurophysiological evidence suggesting defects in neural inhibitory processes, sensorimotor integration, and maladaptive plasticity. Finally, it may explain neurosurgical experience showing that targeting the basal ganglia is effective only for certain subpopulations of dystonia. Most importantly, the network model provides many new and testable hypotheses with direct relevance for new treatment strategies that go beyond the basal ganglia. This article is part of a Special Issue entitled "Advances in dystonia".

Electrophysiological evaluation of tremors secondary to space occupying lesions and trauma: correlation with nature and sites of lesions

BACKGROUND

Electrophysiological evaluation of tremor secondary to intracranial space occupying lesions (SOL) and cranial trauma may provide information regarding pathophysiology of tremors.

OBJECTIVES

To compare the electrophysiological characteristics of tremor secondary to SOL and trauma and to correlate tremor characteristics with sites of lesion, and types of SOL.

METHODS

Multi-channel tremor recording and MRI were performed in 18 patients with predominantly tremor secondary to SOL (F: M = 5:6; age +/- SD: 26.6 +/- 15.0 years) and following trauma (7 men; age: 27.3 +/- 11.0 years).

RESULTS

In both groups, there was a wide range in the frequency of tremor (2.5-7.5 Hz in the SOL group and 2-7.5 Hz in the post-trauma group) and a strong inverse correlation of the frequency with the duration of EMG bursts (SOL group: r = 0.8, p = 0.004; post-trauma group: r = 0.9, p = 0.02). While all the patients with SOL had regular EMG bursts (synchronous - 54.6%, alternating - 27.3%, mixed - 18.2%), 85.7% of post-trauma patients had irregular EMG bursts (synchronous - 42.9%, alternating - 14.3%, mixed - 42.9%). In SOL group, those with predominantly intrinsic destructive lesions of brainstem, thalamus, or basal ganglia (n = 7) had a statistically significant lower mean frequency of tremor than those (n = 4) with either extrinsic or intrinsic compressive lesions (3.5 +/- 0.9 Hz vs 6.7 +/- 0.6 Hz; p = 0.0001). In the post-trauma group, the patients with additional lesions in thalamus or striatum, apart from white and grey matter lesions had lower mean tremor frequency (3.7 +/- 1.0 Hz vs 6.1 +/- 1.5 Hz; p = 0.05).

CONCLUSIONS

The electrophysiological characteristics of tremor secondary to SOL and trauma differ and correlate with the nature and sites of lesions. This information, which need to be validated in larger cohort of patients, may be useful in understanding the pathogenesis of tremor.

(99m)Tc-TRODAT-1 SPECT study in evaluation of Holmes tremor after thalamic hemorrhage

Holmes tremor is also known as rubral or midbrain tremor. The tremor usually involves lesions near the red nucleus and the nerve fiber tracts originating in the cerebellum and the substantia nigra. We report a case of a 62-year-old woman who presented with Holmes tremor 5 months after a left thalamic hemorrhage, with a partial recovery 3 years later. Sequential technetium-(99m)TRODAT-1 single-photon emission computed tomography (SPECT) of the patient's brain revealed partially improved tracer uptake reduction in the striatums, particularly on the left side. We propose that involvement of both the nigrostriatal and the dentate-rubro-thalamic pathways are essential in the pathogenesis of Holmes tremor after a thalamic lesion, and regeneration of the nigrostriatal system is possible in this type of tremor after the initial degeneration. The (99m)Tc-TRODAT-1 SPECT study is a useful and convenient tool for evaluating the nigrostriatal dopamine function in patients with Holmes tremor.

Movement disorders after stroke

Many different types of hyperkinetic and hypokinetic movement disorders have been reported after ischaemic and haemorrhagic stroke. We searched the Medline database from 1966 to February 2008, retrieving 2942 articles from which 156 relevant case reports, case series and review articles were identified. The papers were then further reviewed and filtered and secondary references found. Here we review the different types of abnormal movements reported with anatomical correlation, epidemiology, treatment and prognosis. Post stroke movement disorders can present acutely or as a delayed sequel. They can be hyperkinetic (most commonly hemichorea-hemiballism) or hypokinetic (most commonly vascular parkinsonism). Most are caused by lesions in the basal ganglia or thalamus but can occur with strokes at many different locations in the motor circuit. Many are self limiting but treatment may be required for symptom control.

Clinical differential diagnosis of parkinsonism

Several clinical diagnostic criteria are available for differentiating Parkinson’s disease from the various forms of parkinsonism, but most clinical features have inadequate sensitivity and positive predictive value in the differential diagnosis of these conditions. Although a diagnosis of Parkinson’s disease can be a simple clinical exercise in typical patients with a positive response to dopaminergic treatment, the differential diagnosis versus other parkinsonian disorders can be challenging in some cases, particularly early in the disease. In this paper we have reviewed the motor and nonmotor clinical features that are helpful in the differential diagnosis of the most common forms of parkinsonism. A correct diagnosis in a parkinsonian patient is not simply an academic exercise, but it is crucial for planning any possible therapeutical intervention.

Ventral intermediate thalamic stimulation in complex tremor syndromes

BACKGROUND/AIMS

We report on deep brain stimulation (DBS) in the ventral intermediate part of the thalamus in 4 patients with complex tremor syndromes, 2 classified as Holmes tremor (HT) and 2 as thalamic tremor (TT).

RESULTS

Three out of 4 patients showed intraoperative improvement and underwent DBS implantation. One patient with TT without intraoperative improvement was not provided with an implant. A sustained beneficial effect was present after a follow-up ranging from 20 months to 7 years, although there was partial persistence of the intentional tremor and of proximal myoclonic-dystonic movements. The mean global clinical impression score was 2. In 1 HT patient the benefit persisted after battery failure.

CONCLUSION

The study confirms that ventral intermediate thalamic DBS can provide long-term efficacy for HT and TT. While the patients experienced considerable and lasting functional improvement, the effect was incomplete and not all elements of their complex movement disorders were equally suppressed.

Vascular parkinsonism--an update

Vascular parkinsonism (VP) is a heterogeneous clinical entity. The idea of a relationship between cerebral vascular disease and parkinsonism may be traced back to the 1920s, when the diagnostic unit called "arteriosclerotic parkinsonism", a predecessor of VP, was established. This review is concerned with historical and contemporary views regarding the possible vascular genesis of parkinsonism. Confusion persists as a result of vaguely defined diagnostic criteria. The following types of simultaneous occurrence of parkinsonism and cerebral vascular disease (CVD) may be recognised: 1. gait disorders of the lower body parkinsonism type are caused mostly by white matter lesions in the frontal lobes; such disorders may require a diagnosis of vascular origin. We suggest replacing the term "lower body parkinsonism" with a more appropriate term not including the word "parkinsonism": an alternative term could be "cerebrovascular gait disorder"; 2. if the signs and symptoms are typical for idiopathic Parkinson's disease (IPD), the coincidence of IPD and CVD should be considered; 3. if the symptoms of parkinsonism are neither typical for IPD nor for VP, and there are clinical or MR signs of CVD, VP should be regarded as possible when alternative causes are excluded; 4. if the symptoms of parkinsonism and clinical and MR signs are typical for VP, VP should be regarded as probable; 5. if a stroke affecting the contralateral basal ganglia is followed by the occurrence of hemiparkinsonism, the diagnosis of VP is unambiguous. Vascular parkinsonism (VP) is probably one of the most frequently erroneous neurological diagnoses. The reason for this misdiagnosis is that both cerebral vascular disease (CVD) and parkinsonism usually occur at the same age. Due to the high incidence of CVD, it is possible for CVD and idiopathic Parkinson's disease (IPD) to coincide in some cases. Another reason for the misdiagnosis is that the concept of VP lacks clarity. This review aims to contribute to an improved understanding of VP in clinical practice. In this context, the term "CVD" is understood in the broad sense of a brain impairment caused by cerebral vessel pathology. It covers various concepts, as some authors use the term CVD to mean a manifestation of vascular lesions in pathologico-anatomical material or in the imaging techniques; others mean the history and clinical manifestation of cerebral ischaemia, or, more rarely, haemorrhage. The term CVD may cover large vessel disease as well as small vessel disease. This means that territorial and lacunar infarcts and white matter lesions (WML) are all considered as CVD.

Systemic diseases that cause movement disorders

The present review is aimed at providing practical assistance to the clinical neurologist in reaching a diagnosis, understanding the pathogenic mechanisms of movement disorders associated with systemic diseases, and determining appropriate therapy. Infectious disease by direct effect or as an acquired autoimmune neurological disease, stroke, hypoxia-ischemia, paraneoplastic syndromes, collagen disorders, endocrine, liver and kidney diseases that may cause hypokinetic or hyperkinetic abnormal movement are considered separately. The type and evolution of abnormal movement caused by systemic disease vary with age and underlying pathology. Therapy for abnormal movements should include a primary treatment for the systemic disease.

Post-stroke movement disorders: report of 56 patients

BACKGROUND

Although movement disorders that occur following a stroke have long been recognised in short series of patients, their frequency and clinical and imaging features have not been reported in large series of patients with stroke.

METHODS

We reviewed consecutive patients with involuntary abnormal movements (IAMs) following a stroke who were included in the Eugenio Espejo Hospital Stroke Registry and they were followed up for at least one year after the onset of the IAM. We determined the clinical features, topographical correlations, and pathophysiological implications of the IAMs.

RESULTS

Of 1500 patients with stroke 56 developed movement disorders up to one year after the stroke. Patients with chorea were older and the patients with dystonia were younger than the patients with other IAMs. In patients with isolated vascular lesions without IAMs, surface lesions prevailed but patients with deep vascular lesions showed a higher probability of developing abnormal movements. One year after onset of the IAMs, 12 patients (21.4%) completely improved their abnormal movements, 38 patients (67.8%) partially improved, four did not improve (7.1%), and two patients with chorea died. In the nested case-control analysis, the patients with IAMs displayed a higher frequency of deep lesions (63% v 33%; OR 3.38, 95% CI 1.64 to 6.99, p<0.001). Patients with deep haemorrhagic lesions showed a higher probability of developing IAMs (OR 4.8, 95% CI 0.8 to 36.6).

CONCLUSIONS

Chorea is the commonest movement disorder following stroke and appears in older patients. Involuntary movements tend to persist despite the functional recovery of motor deficit. Deep vascular lesions are more frequent in patients with movement disorders.

Deep brain stimulation of the nucleus ventralis intermedius for Holmes (rubral) tremor and associated dystonia caused by upper brainstem lesions

✓Holmes tremor is caused by structural lesions in the perirubral area of the midbrain. Patients often present with associated symptoms such as dystonia and paresis, which are usually refractory to medical therapy. Here, the authors describe two patients in whom both tremor and associated dystonia improved markedly following unilateral stimulation of the thalamic nucleus ventralis intermedius.

Approche chirurgicale d’un tremblement de Holmes associé à un tremblement synchrone de haute fréquence

INTRODUCTION

The effectiveness of thalamic stimulation is now clearly demonstrated for essential tremor, but remains to be demonstrated for other types of tremor.

OBSERVATION

A young woman presented Holmes' tremor resulting from a pontine tegmental hemorrhage related to an arteriovenous malformation. A surgical approach was considered when major functional impairment persisted at 2-year follow-up despite drug therapy. The patient underwent unilateral thalamic deep brain stimulation (Vim); major improvement persisted at eighteen months follow-up.

CONCLUSION

This observation is in line with previous reports suggesting that thalamic surgery can be one of the best options for treating medically intractable Holmes' tremor. The mechanism underlying the tremor, implying dentate-rubro-thalamic pathways is discussed. Moreover, the patient exhibited short periods of 16Hz tremor when her arms were maintained outstretched. Thalamic stimulation also appears to be effective for these high-frequency synchronous cerebellar bursts.

Deep brain stimulation of the nucleus ventralis intermedius for Holmes (rubral) tremor and associated dystonia caused by upper brainstem lesions. Report of two cases

Holmes tremor is caused by structural lesions in the perirubral area of the midbrain. Patients often present with associated symptoms such as dystonia and paresis, which are usually refractory to medical therapy. Here, the authors describe two patients in whom both tremor and associated dystonia improved markedly following unilateral stimulation of the thalamic nucleus ventralis intermedius.

Tremor--easily seen but difficult to describe and treat

Tremor is a common movement disorder yet many physicians struggle with its terminology as well as with its treatment. Attempts have been made to develop standard terminology and criteria for tremors but this process continues to evolve. In this review, a summary of the currently-proposed phenomenology and syndromic classification of all types of tremor is presented. The diagnosis and management of essential tremor is presented in more detail, as it is the most commonly encountered tremor.

Evolving spectrum of movement disorders in extrapontine and central pontine myelinolysis

Extrapontine (EPM) and central pontine myelinolysis (CPM) are rare and frequently related to rapid correction of hyponatremia. We describe a 60-year-old woman who developed an unusual evolving spectrum of movement disorders secondary to EPM and CPM following intravenous sodium replacement therapy for severe hyponatremia. She presented initially with confusion, generalized coarse postural limb tremor, myoclonic jerks and quadriparesis. Subsequently her mental state improved and her tremor and weakness resolved. Over the following months, she developed progressive painful dystonia of her facial musculature and lower limbs. This gradually became generalized and associated with choreoathethosis in her limbs. In addition, she had increasing bradykinesia and rigidity, which responded poorly to levodopa treatment. Our case illustrates that while the myelin destruction occurs during the initial insult of the osmotic demyelinating process, its delayed clinical effects resulting from ineffective reorganization of neuronal structures may be progressive, evolve with time, and difficult to treat.

Posttraumatic tremor without parkinsonism in a patient with complete contralateral loss of the nigrostriatal pathway

We present a patient with posttraumatic tremor who did not show any [(123)I]FP-CIT uptake in the contralateral putamen and caudate. The absence of hypokinesia and rigidity is surprising in the presence of a striatal dopaminergic denervation that is even more severe than in Parkinson's disease. An explanation, therefore, could be that the lesion in the subthalamic nucleus in our patient prevented the onset of a Parkinson syndrome.

Intracortical inhibition is reduced in a patient with a lesion in the posterolateral thalamus

We describe a patient who developed a complex movement disorder following an ischemic lesion in the right posterolateral thalamus. Transcranial magnetic stimulation showed a shortening of the cortical silent period and deficient cortico-cortical inhibition using paired magnetic pulses on the affected side, indicating reduced effectiveness of intracortical inhibitory mechanisms.

Reorganization of somatic sensory function in the human thalamus after stroke

A patient with thalamic stroke underwent microelectrode-guided stereotactic thalamic exploration during surgery for control of tremor. The results of somatic sensory mapping in this patient were compared with explorations carried out during stereotactic surgery for the control of essential tremor (70 patients). There was evidence both of somatotopic reorganization and of anatomic reorganization of the representation of deep structures in the principal somatic sensory nucleus of the thalamus and the nuclei located anterior to it. This case demonstrates that thalamic reorganization can occur after a thalamic stroke and may play a role in recovery from such a stroke.

Rubral tremor after thalamic infarction in childhood

The occurrence of tremor after thalamic lesions is well known. Delayed rubral tremor secondary to bilateral thalamic infarction is a rare finding and has not been reported previously in childhood. We present two children with a combined resting-postural-kinetic tremor caused by bithalamic infarction. The first child was a male 14 months of age, and the second was a male 9 years of age. These children come from unrelated families. On hospital admission of the first patient, generalized seizures and routine electroencephalogram (EEG) findings with diffuse spike-wave discharges predominantly over the left frontal area were clinically observed, leading to the initial diagnosis of epilepsia partialis continua. However, clinical observation and video-EEG monitoring of the movements revealed nonepileptiform accompaniments, favoring the diagnosis of rubral tremor. In the second patient, EEG revealed no paroxysmal activity and was within normal limits for age. In both patients, cranial magnetic resonance imaging revealed ischemic lesions in thalami bilaterally but failed to reveal any mesencephalic lesion. These patients demonstrate that thalamic infarction can cause rubral tremor in childhood.

Complex movement disorders following bilateral paramedian thalamic and bilateral cerebellar infarcts

Complex movement disorders (CMD; including tremor, dystonias, choreoatheosis, and myoclonus) following infarcts in the posterior and posterolateral thalamic nuclei have been reported. This case of a 59-year-old man who developed CMD following bilateral paramedian and bilateral cerebellar infarcts illustrates the lack of anatomic specificity and the diverse pathophysiology which may underlie CMD.

The pathophysiology of tremor

Tremor is defined as rhythmic oscillatory activity of body parts. Four physiological basic mechanisms for such oscillatory activity have been described: mechanical oscillations; oscillations based on reflexes; oscillations due to central neuronal pacemakers; and oscillations because of disturbed feedforward or feedback loops. New methodological approaches with animal models, positron emission tomography, and mathematical analysis of electromyographic and electroencephalographic signals have provided new insights into the mechanisms underlying specific forms of tremor. Physiological tremor is due to mechanical and central components. Psychogenic tremor is considered to depend on a clonus mechanism and is thus believed to be mediated by reflex mechanisms. Symptomatic palatal tremor is most likely due to rhythmic activity of the inferior olive, and there is much evidence that essential tremor is also generated within the olivocerebellar circuits. Orthostatic tremor is likely to originate in hitherto unidentified brainstem nuclei. Rest tremor of Parkinson's disease is probably generated in the basal ganglia loop, and dystonic tremor may also originate within the basal ganglia. Cerebellar tremor is at least in part caused by a disturbance of the cerebellar feedforward control of voluntary movements, and Holmes' tremor is due to the combination of the mechanisms producing parkinsonian and cerebellar tremor. Neuropathic tremor is believed to be caused by abnormally functioning reflex pathways and a wide variety of causes underlies toxic and drug-induced tremors. The understanding of the pathophysiology of tremor has made significant progress but many hypotheses are not yet based on sufficient data. Modern neurology needs to develop and test such hypotheses, because this is the only way to develop rational medical and surgical therapies.

Delayed onset mixed involuntary movements after thalamic stroke: clinical, radiological and pathophysiological findings

Although occurrence of involuntary movements after thalamic stroke has occasionally been reported, studies using a sufficiently large number of patients and a control population are not available. Between 1995 and 1999, the author prospectively identified 35 patients with post-thalamic stroke delayed-onset involuntary movements, which included all or some degree of dystonia-athetosis-chorea-action tremor, occasionally associated with jerky, myoclonic components. A control group included 58 patients examined by the author during the same period who had lateral thalamic stroke but no involuntary movements. Demography, clinical features and imaging study results were compared. There were no differences in gender, age, risk factors, side of the lesion and follow-up periods. During the acute stage of stroke, the patients who had involuntary movements significantly more often had severe (< or = III/V) hemiparesis (50 versus 20%, P < 0.05) and severe sensory loss (in all modalities, P < 0.01) than the control group. At the time of assessment of involuntary movements, the patients with involuntary movements significantly more often had severe sensory deficit (in all modalities, P < 0.01) and severe limb ataxia (60 versus 5%, P < 0.01) than the control patients, but neither more severe motor dysfunction (7 versus 0%) nor more painful sensory symptoms (57 versus 57%). The patients with involuntary movements had a higher frequency of haemorrhagic (versus ischaemic) stroke (63 versus 31%, P < 0.05). Further analysis showed that dystonia-athetosis-chorea was closely associated with position sensory loss, whereas the tremor/myoclonic movements were related to cerebellar ataxia. Recovery of severe limb weakness seemed to augment the instability of the involuntary movements. Persistent failure of the proprioceptive sensory and cerebellar inputs in addition to successful, but unbalanced, recovery of the motor dysfunction seemed to result in a pathological motor integrative system and consequent involuntary movements in patients with relatively severe lateral-posterior thalamic strokes simultaneously damaging the lemniscal sensory pathway, the cerebellar-rubrothalamic tract and, relatively less severely, the pyramidal tract.