Trunk and head tremor as isolated manifestations of dystonia

Dystonic Tremor: Time to Change

BACKGROUND

The term dystonic tremor is being increasingly used in neurological publications despite uncertainties about its meaning. We provide here a historical reconstruction from its original introduction in 1984 to help distinguish dystonia from essential tremor.

METHODS

A comprehensive Pubmed search of MeSH terms "dystonia", "tremor", and "essential tremor" provided the information base for reconstructing historical usage of the term "dystonic tremor".

RESULTS

Over the years, this expression was enriched of additional meanings and sided by companion descriptors, such as tremor associated with dystonia. Dystonic tremor has been considered characteristically coarse, jerky, irregular, directional and asymmetrical. These characteristics, however, are not included in the most recent definitions of tremor. The relationship between tremor and dystonia is not easy to untangle, as the two phenomena are often recognized in association. Tremor and dystonia experts have developed different visions of dystonic tremor that have been variably implemented. There are currently two independent consensus definitions, which are not coincident and imply different pathophysiological interpretations.

CONCLUSIONS

This historical reappraisal highlights that usage of the expression dystonic tremor has evolved over time to lose its original meaning. Notwithstanding inconsistencies of current definitions, its usage has steadily increased and it is time now to agree on an updated terminology.

Essential and dystonic head tremor: More similarities than differences

INTRODUCTION

Head tremor is a common symptom of essential tremor (ET) and cervical dystonia (CD). In clinical practice, it is often difficult to distinguish between these two conditions, especially in cases where head tremor predominates.

OBJECTIVES

To investigate which clinical and instrumental methods best differentiate ET and CD in patients with head tremor.

METHODS

65 patients were included, of which 23 were diagnosed with ET and head tremor (HT+), 21 with ET without head tremor (HT-) and 21 with CD and dystonic head tremor. 22 healthy volunteers served as controls. All patients were examined using the rating scales for ET (TETRAS), cervical dystonia (TWSTRS), and ataxia (SARA). The Somatosensory Temporal Discrimination Threshold (STDT) was defined as the shortest interval in which an individual recognizes two tactile stimuli as temporally separated.

RESULTS

TETRAS and SARA scores were higher in the HT+ group compared with HT- and CD, with no significant difference between mild head tremor subscores in HT+ and CD. In most HT+ and CD patients, head tremor disappeared supine. The STDT values were significantly higher in the HT+ group compared with controls.

CONCLUSION

While TWSTRS contributed to assess dystonia severity, the scales of tremor and ataxia were not helpful in differentiating head tremor syndromes. The cessation of head tremor in the supine position could be related to the overall mild head tremor scores in both groups. Increased SARA scores and STDT values in HT+ patients suggest a possible role of cerebellar involvement and altered somatosensory timing that merit further verification.

Isolated Cervical Dystonia: Diagnosis and Classification

This document presents a consensus on the diagnosis and classification of isolated cervical dystonia (iCD) with a review of proposed terminology. The International Parkinson and Movement Disorder Society Dystonia Study Group convened a panel of experts to review the main clinical and diagnostic issues related to iCD and to arrive at a consensus on diagnostic criteria and classification. These criteria are intended for use in clinical research, but also may be used to guide clinical practice. The benchmark is expert clinical observation and evaluation. The criteria aim to systematize the use of terminology as well as the diagnostic process, to make it reproducible across centers and applicable by expert and non-expert clinicians. Although motor abnormalities remain central, increasing recognition has been given to nonmotor manifestations, which are incorporated into the current criteria. Three iCD presentations are described in some detail: idiopathic (focal or segmental) iCD, genetic iCD, and acquired iCD. The relationship between iCD and isolated head tremor is also reviewed. Recognition of idiopathic iCD has two levels of certainty, definite or probable, supported by specific diagnostic criteria. Although a probable diagnosis is appropriate for clinical practice, a higher diagnostic level may be required for specific research studies. The consensus retains elements proven valuable in previous criteria and omits aspects that are no longer justified, thereby encapsulating diagnosis according to current knowledge. As understanding of iCD expands, these criteria will need continuous revision to accommodate new advances. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

The Molecular Neuroimaging of Tremor

Purpose of Review

Tremor is a hyperkinetic movement disorder most commonly encountered in essential tremor (ET) and Parkinson’s disease (PD). The purpose of this review is to summarize molecular neuroimaging studies with major implications on pathophysiological and clinical features of tremor.

Recent Findings

Oscillatory brain activity responsible for tremor manifestation is thought to originate in a cerebello-thalamo-cortical network. Molecular neuroimaging has helped clarify metabolic aspects and neurotransmitter influences on the main tremor network. In ET, recent positron emission tomography (PET) studies are built on previous knowledge and highlighted the possibility of investigating metabolic brain changes after treatments, in the attempt to establish therapeutic biomarkers. In PD, molecular neuroimaging has advanced the knowledge of non-dopaminergic determinants of tremor, providing insights into serotonergic and noradrenergic contributions.

Summary

Recent advances have greatly extended the knowledge of tremor pathophysiology and it is now necessary to translate such knowledge in more efficacious treatments for this symptom.

Tremor Syndromes: An Updated Review

Tremor is the most commonly encountered movement disorder in clinical practice. A wide range of pathologies may manifest with tremor either as a presenting or predominant symptom. Considering the marked etiological and phenomenological heterogeneity, it would be desirable to develop a classification of tremors that reflects their underlying pathophysiology. The tremor task force of the International Parkinson Disease and Movement Disorders Society has worked toward this goal and proposed a new classification system. This system has remained a prime topic of scientific communications on tremor in recent times. The new classification is based on two axes: 1. based on the clinical features, history, and tremor characteristics and 2. based on the etiology of tremor. In this article, we discuss the key aspects of the new classification, review various tremor syndromes, highlight some of the controversies in the field of tremor, and share the potential future perspectives.

The Prevalence of Dystonic Tremor and Tremor Associated with Dystonia in Patients with Cervical Dystonia

The link between dystonia and tremor has been known for decades, but the question of whether they are two separate illnesses or just different manifestations of one disease with the same pathophysiological background remains unanswered. We distinguish two types of tremor in dystonia: dystonic tremor (DT), which appears on the body part affected by dystonia, and tremor associated with dystonia (TAWD), which appears in locations where the dystonia does not occur. In this study, the frequency of occurrence of different forms of tremor was determined by clinical examination in a group of adult-onset isolated cervical dystonia (CD) patients treated with regular local injections of botulinum toxin A in our department. In total, 120 patients were included in the study, of which 70 (58.3%) had DT of the head. TAWD was, in all 14 cases (11.7%), observed on the upper limbs, in the form of static or intentional tremor. The aim of this study was to point out the presence of TAWD as one of the clinical signs of CD. DT occurred in more than half of the patients and appears to be a relatively common part of the clinical picture in patients with CD.

The prevalence of essential tremor in Edirne and its counties accompanied comorbid conditions

Objective: We aimed to determine the prevalence and risk factors of Essential Tremor (ET) in Edirne and its districts, located in Western Thrace, which is the most western part of Turkey. Methods: In this study, 3008 individuals who could communicate and agreed to participate in the study were evaluated. To obtain the data from the applicants in 30 Family Health Centres in Edirne and its districts, a face-to-face questionnaire that consisted of 37 questions was prepared by the researchers. The questionnaire included general information, questions to evaluate potential concomitant comorbid conditions and questions regarding the symptomatology used in ET diagnosis, as well as questions to evaluate ET severity, was examined with the spiral test. Patients were classified by using the Washington Heights-Inwood Genetic Study of Essential Tremor (WHIGET) diagnostic and clinical evaluation scale. According to the diagnostic criteria for ET (used in participants who were examined and in those whose medical records were reviewed) were similar to those used in astudy conducted in Turkey. Results: Of 3008 individuals, 173 were diagnosed with ET according to the questionnaire results from Edirne and its districts, and the prevalence of ET was 5.8%. Approximately, 43.4% of the patients with ET were male, and 56.6% were female, which was not significantly different (p > 0.05). Participants with tremor related to alcohol withdrawal, hyperthyroidism, anxiety, depression other known causes of tremor were not considered to have ET. Thyroid disease was identified in 0.0% of the cases, and the control group was detected in 1.4%, which was not significantly different (p = 0.170). Psychiatric disease was identified in 0.0% of the cases, and the control group was detected in 1.3%, which was not significantly different (p = 0.271). Conclusions: ET prevalence studies will increase the awareness of the community and provide early diagnosis and treatment, as well as serve as a basis to reduce morbidity and improve the quality of life.

Head tremor at disease onset: an ataxic phenotype of cervical dystonia

BACKGROUND

Cervical dystonia (CD) can present with head tremor. It is unclear whether ataxic features are differentially associated with this phenotype at onset of CD.

OBJECTIVES

We sought to evaluate: (1) the demographic features of CD patients with (Tr-CD) and without head tremor (nTr-CD) at onset, and (2) the differential ataxic features between these CD subtypes.

METHODS

For the first objective, we compared demographic data in Tr-CD versus nTr-CD subtypes in the entire cohort of CD subjects enrolled in the Dystonia Coalition Natural History and Biorepository studies (n = 1608). For the second objective, we rated the standardized videos from consecutively enrolled Tr-CD subjects (n = 50) and age-, gender-, and disease duration-matched nTr-CD subjects (n = 50) for ataxia severity scoring using the Scale for the Assessment and Rating of Ataxia (SARA) and the International Cooperative Ataxia Rating Scale (ICARS); and for dystonia severity using the Toronto Western Spasmodic Torticollis Rating Scale section-I (TWSTRS) and the Global Dystonia Rating Scale (GDRS).

RESULTS

Of 1,608 subjects, 18.1% (n = 291) were classified as Tr-CD and 81.9% (n = 1317) as nTr-CD. The Tr-CD cohort was older, predominantly female, and had longer disease duration than the nTr-CD cohort (p = 0.01). Compared to nTr-CD, Tr-CD subjects had worse generalized ataxia, speech, and gait and posture scores. High ataxia severity with low dystonia severity distinguished Tr-CD from nTr-CD with high accuracy (area under the curve, 0.91 (95% CI 0.85-0.97).

CONCLUSIONS

Head tremor at disease onset represents a clinically distinguishable subtype of cervical dystonia affecting predominantly older women, with worse ataxia and milder dystonia than the non-tremulous dystonic phenotype.

Differential effects of propranolol on head and upper limb tremor in patients with essential tremor and dystonia

Propranolol is used as the first-line treatment in essential tremor and it has also been proposed as a treatment for tremor in dystonia. However, several issues remain uncertain. For example, it is still not clear whether propranolol exerts a beneficial effect on head tremor. Moreover, no studies have investigated whether the effect of propranolol on head and upper limb tremor in essential tremor differs from that in dystonia. We aimed to assess the effects of propranolol on tremor in different body parts in essential tremor and in patients with tremor and dystonia. Twenty-nine patients with head and upper limb tremor were enrolled in the study, 14 with essential tremor, and 15 with dystonia. Participants underwent a clinical and kinematic analysis of tremor in two sessions, i.e., without (baseline) and 'on therapy' with propranolol. We found that head tremor was more severe in patients with dystonia, while upper limb tremor was more evident in patients with essential tremor (P < 0.05). Propranolol had no effect on head tremor in either group (all Ps > 0.05), but it did reduce upper limb tremor in patients with essential tremor. The present study demonstrates differential effects of propranolol on head and upper limb tremor in patients with essential tremor. The lack of effect on head and upper limb tremor in patients with dystonia suggests that the pathophysiological mechanisms underlying tremor in these two conditions and in different body parts may be distinct.

Transient, Isolated Head Tremor in "Unaffected" Individuals: Is Essential Tremor an Even More Prevalent Disease Than We Suppose?

Background: Mild and transient head tremor may sometimes be observed in otherwise tremor-free relatives of essential tremor (ET) cases, although its prevalence is unclear. A diagnostic question is whether this transient, isolated head tremor, often observed as no more than a wobble, is an early manifestation of ET or whether it is a normal finding. A direct comparison with controls is needed.

Methods: Two hundred and forty-one first-degree relatives of ET cases (FD-ET) and 77 spousal controls (Co) were enrolled in a study of ET. Each underwent a detailed evaluation that included a tremor history and videotaped neurological examination. None of the enrollees reported tremor, had a prior diagnosis of ET, or had significant tremor on screening spirals. All videotaped examinations were initially reviewed by a movement disorder neurologist blinded to subject type, and among those with head tremor on examination, co-reviewed by two additional movement disorders neurologists.

Results: Twenty-six (10.8, 95% Confidence interval [CI] = 7.5–15.3%) of 241 FD-ET vs. 2 (2.6, 95% CI = 0.7–9.0%) of 77 Co had isolated, transient head tremor (odds ratio = 4.54, 95% CI = 1.05–19.57, p = 0.04). No enrollee had significant upper extremity tremor and none met inclusion criteria for ET based on the presence of upper extremity tremor. With one exception, head tremor occurred during or after phonation. It was always transient (generally a single back and forth wobble) and rare (observed briefly on one or two occasions during the videotaped examination) and had a faster frequency, lower amplitude and a different quality than voluntary head shaking.

Conclusion: The basis for the observed isolated head tremor is unknown, but it could be an early feature of ET in ET families.Indeed, one-in-ten otherwise unaffected first-degree relatives of ET cases exhibited such tremor. To a far lesser extent it was also observed in “unaffected” controls. In both, it is likely a sign of early, emerging, undiagnosed ET, although follow-up studies are needed to confirm this. If it were ET, it would indicate that the prevalence of ET may be considerably higher than previously suspected.

Head Tremor in Cervical Dystonia

Objective:

To compare the clinical characteristics, natural history, and therapeutic outcome of patients with cervical dystonia (CD) with head tremor (HT+) and without head tremor (HT-).

Methods:

We prospectively evaluated 114 consecutive patients of CD over a 9-month period with a detailed questionnaire. Chi-square and t-tests were employed for statistical analysis.

Results:

Seventy-eight (68.4%) patients had head tremor and 27 of them (34.6%) had tremor as one of the first symptoms. Age at onset of symptoms were similar in HT+ and HT- groups; however there was a higher prevalence in women in the former group (66.7% vs. 41.7%; p=0.01). HT+ patients had more frequent positive family history of essential-like hand/head tremor (21.8% vs. 5.5%; p<0.05), associated neck pain (92.3% vs. 77.8%; p<0.05), and essential-like hand tremor (40% vs. 8.3%; p<0.001). They also appeared to have more frequent history of preceding head/neck trauma (14.1% vs. 8.3%), frequent head rotation (88.5% vs. 69.4%) and antecollis (12.8% vs. 5.5%) but less often head tilt (37.2% vs. 47.2%) and gestes antagonistes (60.2% vs. 75%) than the HT- patients; however these differences were not statistically significant. The frequency of prior psychiatric illnesses, the incidence of dystonias in other parts of the body, frequency of retrocollis and shoulder elevation, and spontaneous remission were similar in the two groups.

Conclusions:

Head tremor is common in CD and is more commonly associated with hand tremor and family history of tremor or other movement disorders. This supports a possible genetic association between CD and essential tremor (ET). Linkage studies are required to evaluate the genetic association between CD and ET.

Tremor entities and their classification: an update

PURPOSE OF REVIEW

This review focuses on important new findings in the field of tremor and illustrates the consequences for the current definition and classification of tremor.

RECENT FINDINGS

Since 1998 when the consensus criteria for tremor were proposed, new variants of tremors and new diagnostic methods were discovered that have changed particularly the concepts of essential tremor and dystonic tremor. Accumulating evidence exists that essential tremor is not a single entity rather different conditions that share the common symptom action tremor without other major abnormalities. Tremor is a common feature in patients with adult-onset focal dystonia and may involve several different body parts and forms of tremor. Recent advances, in particular, in the field of genetics, suggest that dystonic tremor may even be present without overt dystonia. Monosymptomatic asymmetric rest and postural tremor has been further delineated, and apart from tremor-dominant Parkinson's disease, there are several rare conditions including rest and action tremor with normal dopamine transporter imaging (scans without evidence of dopaminergic deficit) and essential tremor with tremor at rest.

SUMMARY

Increasing knowledge in the last decades changed the view on tremors and highlights several caveats in the current tremor classification. Given the ambiguous assignment between tremor phenomenology and tremor etiology, a more cautious definition of tremors on the basis of clinical assessment data is needed.

Dystonia and Tremor: The Clinical Syndromes with Isolated Tremor

BACKGROUND

Dystonia and tremor share many commonalities. Isolated tremor is part of the phenomenological spectrum of isolated dystonia and of essential tremor. The occurrence of subtle features of dystonia may allow one to differentiate dystonic tremor from essential tremor. Diagnostic uncertainty is enhanced when no features of dystonia are found in patients with a tremor syndrome, raising the question whether the observed phenomenology is an incomplete form of dystonia.

METHODS

Known forms of syndromes with isolated tremor are reviewed. Diagnostic uncertainties between tremor and dystonia are put into perspective.

RESULTS

The following isolated tremor syndromes are reviewed: essential tremor, head tremor, voice tremor, jaw tremor, and upper-limb tremor. Their varied phenomenology is analyzed and appraised in the light of a possible relationship with dystonia.

DISCUSSION

Clinicians making a diagnosis of isolated tremor should remain vigilant for the detection of features of dystonia. This is in keeping with the recent view that isolated tremor may be an incomplete phenomenology of dystonia.

Head tremor in essential tremor: "Yes-yes", "no-no", or "round and round"?

INTRODUCTION

Essential tremor (ET) is a common yet frequently misdiagnosed movement disorder. One contributing factor may be the dearth of studies that focus on the nuances of clinical phenomenology. A clinical feature that has received relatively little attention is head tremor. Indeed, there is no consensus regarding the predominant direction of head tremor in ET, and no study has examined the clinical correlates of directionality.

METHODS

We identified 51 ET cases with head tremor enrolled in a clinical-epidemiological study of ET at Columbia University. Each had a videotaped neurological examination. Videotapes were viewed and coded by a movement disorders neurologist for head tremor direction ("no-no", "yes-yes", or mixed) and continuity (continuous, intermittent, or rare). Direction was correlated with a wide range of clinical features.

RESULTS

Fourteen cases (27.5%) had "no-no" tremor, 9 (17.6%) had "yes-yes" tremor, and 28 (54.9%) had a mixed tremor. Mixed and "yes-yes" cases were older (p = 0.004) and had a longer tremor duration (p = 0.018) than "no-no" cases. Tremor severity (arms) was higher for mixed cases than for "yes-yes" and "no-no" cases (p = 0.04). More mixed cases had continuously present tremor while more "no-no" cases had rare head tremor (p < 0.001).

CONCLUSIONS

Head tremor in ET seems to start as an infrequent tremor in one direction (esp. "no-no") and becomes more frequent while acquiring additional directionality and a mixed phenotype as the disease progresses. These findings add to our understanding of the clinical spectrum of ET.

Oscillatory head movements in cervical dystonia: Dystonia, tremor, or both?

Cervical dystonia is characterized by abnormal posturing of the head, often combined with tremor-like oscillatory head movements. The nature and source of these oscillatory head movements is controversial, so they were quantified to delineate their characteristics and develop a hypothetical model for their genesis. A magnetic search coil system was used to measure head movements in 14 subjects with cervical dystonia. Two distinct types of oscillatory head movements were detected for most subjects, even when they were not clinically evident. One type had a relatively large amplitude and jerky irregular pattern, and the other had smaller amplitude with a more regular and sinusoidal pattern. The kinematic properties of these two types of oscillatory head movements were distinct, although both were often combined in the same subject. Both had features suggestive of a defect in a central neural integrator. The combination of different types of oscillatory head movements in cervical dystonia helps to clarify some of the current debates regarding whether they should be considered as manifestations of dystonia or tremor and provides novel insights into their potential pathogenesis.

Are patients with limb and head tremor a clinically distinct subtype of essential tremor?

BACKGROUND

Essential tremor (ET) is the most common tremor disorder in adults. In addition to upper limbs, the tremor in ET may also involve head, jaw, voice, tongue, and trunk. Though head tremor (HT) is commonly present in patients with ET, large comparative studies of ET patients with HT (HT+) and without HT (HT-) are few.

METHODS

To determine whether ET with HT is a distinct clinical subtype by comparing ET patients with and without HT, a chart review of 234 consecutive patients with ET attending the neurology clinics of the National Institute of Mental Health and Neurosciences, India, was done. A movement disorder specialist confirmed the diagnosis of ET in all patients using the National Institutes of Health collaborative genetic criteria.

RESULTS

HT was present in 44.4% of the patients. Comparison between HT+ and HT- showed that the HT+ group patients: (1) were older, (2) had later onset of tremor, (3) had unimodal distribution of age at onset with a single peak in the fifth decade, (4) had more frequent voice tremor, and (5) were more likely to have mild cervical dystonia. HT was part of presenting symptoms in nearly two thirds of the ET patients and in the rest it was detected during clinical examination.

CONCLUSIONS

Several demographic and clinical variables suggest that ET patients with HT have a distinct clinical phenotype.

The treatment of dystonic tremor: a systematic review

Tremor is one of the clinical manifestations of dystonia; however, there are no specific therapeutic trials evaluating the efficacy of treatments for dystonic tremor (DT), tremor associated with dystonia or primary writing tremor (PWT). We systematically reviewed the literature available up to July 2013 on the treatment of these tremors and retrieved the data of 487 patients published in 43 papers detailing the effects of given interventions on tremor severity. Treatment outcome was highly variable, depending on the specific type of intervention and tremor distribution. No specifically designed studies were available for the treatment of tremor associated with dystonia. As for the other tremors, drug efficacy was generally disappointing and a moderate effect was only found with anticholinergics, tetrabenazine, clonazepam, β-blockers and primidone; levodopa was only efficacious on tremor due to dopa-responsive dystonia. The largest amount of data was available for botulinum toxin injections, which provided a marked improvement, particularly for the management of axial tremors (head or vocal cords). In refractory DTs, deep brain stimulation of several targets was attempted. Deep brain stimulation of globus pallidus internus, thalamus or subthalamic area led to a marked improvement of dystonic axial or appendicular tremors in most cases refractory to other treatments. Few other non-invasive treatments, for example, orthotic device in PWT, have been used with anecdotal success. In conclusion, considering the lack of good-quality studies, future randomised controlled trials are needed. In absence of evidence-based guidelines, we propose an algorithm for the treatment of DT based on currently available data.

What is essential tremor?

Classic essential tremor is a clinical syndrome of action tremor in the upper limbs (at least 95 % of patients) and less commonly the head, face/jaw, voice, tongue, trunk, and lower limbs, in the absence of other neurologic signs. However, the longstanding notion that essential tremor is a monosymptomatic tremor disorder is being challenged by a growing literature describing associated disturbances of tandem walking, personality, mood, hearing, and cognition. There is also epidemiologic, pathologic, and genetic evidence that essential tremor is pathophysiologically heterogeneous. Misdiagnosis of essential tremor is common because clinicians frequently overlook other neurologic signs and because action tremor in the hands is caused by many conditions, including dystonia, Parkinson disease, and drug-induced tremor. Thus, essential tremor is nothing more than a syndrome of idiopathic tremulousness, and the challenge for researchers and clinicians is to find specific etiologies of this syndrome.

Tremor associated with focal and segmental dystonia

BACKGROUND AND PURPOSE

Tremor occurs in 10-85% of patients with focal dystonia as so-called dystonic tremor or tremor associated with dystonia. The aim of this study was to assess the incidence and to characterize parameters of tremor accompanying focal and segmental dystonia.

MATERIAL AND METHODS

One hundred and twenty-three patients with diagnosis of focal and segmental dystonia together with 51 healthy controls were included in the study. For each participant, clinical examination and objective assessment (accelerometer, electromyography, graphic tablet) of hand tremor was performed. Frequency and severity of tremor were assessed in three positions: at rest (rest tremor); with hands extended (postural tremor); during 'finger-to-nose' test and during Archimedes spiral drawing (kinetic tremor). Based on the mass load test, type of tremor was determined as essential tremor type or enhanced physiological type.

RESULTS

The incidence of tremor was significantly higher in dystonic patients as compared to controls (p = 0.0001). In clinical examination, tremor was found in 50% of dystonic patients, and in instrumental assessment in an additional 10-20%. The most frequent type of tremor was postural and kinetic tremor with 7 Hz frequency and featured essential tremor type. In the control group, tremor was detected in about 10% of subjects as 9-Hz postural tremor of enhanced physiological tremor type. No differences were found between patients with different types of dystonia with respect to the tremor incidence, type and parameters (frequency and severity). No correlations between tremor severity and dystonia severity were found either.

Defining dystonic tremor

A strong association between dystonia and tremor has been known for more than a century. Two forms of tremor in dystonia are currently recognized: 1) dystonic tremor, which is tremor produced by dystonic muscle contraction and 2) tremor associated with dystonia, which is tremor in a body part that is not dystonic, but there is dystonia elsewhere. Both forms of tremor in dystonia frequently resemble essential tremor or another pure tremor syndrome (e.g., isolated head and voice tremors and task-specific writing tremor), and relationships among these tremor disorders have long been debated. Misdiagnosis is common because mild dystonia is frequently overlooked in patients with tremor. It is now clear that essential tremor is a syndrome, not a specific disease, and the use of essential tremor as a specific clinical diagnosis is arguably an impediment to elucidating this and other pure tremor syndromes and their relationship to dystonia. A new classification, primary tremor, is proposed and would be used for any disorder in which tremor is the sole or principal abnormality with no identifiable etiology other than possible genetic inheritance. This classification scheme would facilitate tremor research by moving the focus from the narrow question "Is it essential tremor?" to a broader consideration of what genetic and environmental factors cause primary tremor disorders, and how do they relate to dystonia and other neurological disorders.

The focal dystonias: current views and challenges for future research

The most common forms of dystonia are those that develop in adults and affect a relatively isolated region of the body. Although these adult-onset focal dystonias are most prevalent, knowledge of their etiologies and pathogenesis has lagged behind some of the rarer generalized dystonias, in which the identification of genetic defects has facilitated both basic and clinical research. This summary provides a brief review of the clinical manifestations of the adult-onset focal dystonias, focusing attention on less well understood clinical manifestations that need further study. It also provides a simple conceptual model for the similarities and differences among the different adult-onset focal dystonias as a rationale for lumping them together as a class of disorders while at the same time splitting them into subtypes. The concluding section outlines some of the most important research questions for the future. Answers to these questions are critical for advancing our understanding of this group of disorders and for developing novel therapeutics.

Deep brain stimulation of the ventrolateral thalamic base and posterior subthalamic area in dystonic head tremor

Dystonic head tremor (DHT) is characterized by head tremor associated with cervical dystonia (CD). Deep brain stimulation (DBS) can be considered when local treatment with botulinum toxin or oral medication has failed. However, there is lack of data regarding the optimal target structure for surgery in DHT.DBS of the ventrolateral (VL) thalamus is an established treatment option for medically refractory tremor. Tremor suppression is described as being most effective when stimulating at the inferior thalamic base and within the posterior subthalamic area (PSA). Moreover, there is surgical evidence from the pre-DBS era that both lesions and high-frequency stimulation of the PSA improve CD. Based on these observations, we performed DBS in three patients with DHT, placing the proximal contacts of the electrodes into the inferior base of VL thalamic nuclei and the distal contacts into the adjacent PSA. Chronic stimulation improved not only head tremor but also CD. These findings suggest that DBS at the base of VL thalamus and the adjacent PSA should undergo further investigation as a potential target for patients with DHT.

Cognitive features of essential tremor: a review of the clinical aspects and possible mechanistic underpinnings

The classical concept of essential tremor (ET) as a monosymptomatic tremorogenic disorder has been questioned in the last decade as new evidence has been described. Clinical, neuroimaging, and pathological studies have described a probable structural basis (mainly in cerebellum) and evidence that ET is associated with subtle clinical cerebellar deficits and several non-motor clinical manifestations, such as cognitive and mood disorders. We performed literature searches in Medline, ISI Web of Knowledge, and PsycInfo databases. The aim of this review is to describe cognitive deficits associated with ET. First, we present a brief history of ET cognitive disorders presented. Second, we describe several clinical cross-sectional series demonstrating that ET is associated with mild cognitive deficits of attention, executive functions, several types of memory (working memory, immediate, short term, delayed, and possibly others) and, mood disorders (depression). Recent neuroimaging studies favor a cerebellar basis for these cognitive deficits. Population-based surveys confirm that mild cognitive dysfunction is not limited to severe ET cases, the entire ET group, including mild and undiagnosed cases, can be affected. Cohort studies indicated that ET cognitive deficits could be progressive and that ET patients had an increased risk of dementia. The mood and cognitive deficits in ET are in agreement with cognitive affective cerebellar syndrome described in patients with cerebellar disorders. New evidence, mainly from functional (neuroimaging) and prospective clinical studies would further bolster recent descriptions of ET clinical manifestations.

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.

Arm tremor in cervical dystonia--is it a manifestation of dystonia or essential tremor?

The classification of arm tremor in cervical dystonia is a controversial issue. There have been many, at times passionate disputes in the movement disorder community about whether it should be classified as a manifestation of dystonia or essential tremor associated with dystonia. There are arguments in favor of both views. Settling the issue might be relevant to the understanding of the etiological, presumably genetic, background because phenomenological grouping is the starting point for genetic analyses. From this point of view, we outline this tremor debate and add some new clinical data.

The diagnostic challenge of primary dystonia: evidence from misdiagnosis

Although the understanding of dystonia has improved in recent years, primary dystonia is still insufficiently recognized and patients may not receive the correct diagnosis, leading to transient or permanent misclassification of their symptoms. We reviewed cases of primary dystonia who were at first misdiagnosed and analyzed the reasons why the correct diagnosis was first missed and later retained. Primary dystonia is misdiagnosed mainly, but not exclusively, in favor of other movement disorders: Parkinson's disease (PD), essential tremor, myoclonus, tics, psychogenic movement disorder (PMD), and even headache or scoliosis. Accounts are more numerous for PD and PMD, where diagnostic tests, such as DAT scan and psychological assessment, support clinical orientation. The correct diagnosis was achieved in all cases following the recognition of inconsistencies in the first judgment and of distinctive clinical features of dystonia. These clues have been collected here and assembled into a diagnostic epitome.

Disabling Head Tremor in a Patient with DYT1 Mutation

Dystonic head tremor is known to be a feature in some patients with DYT1 mutation. However, isolated tremor of the head without relevant cervical dystonia has rarely been described. We report here a patient with the three-bp GAG deletion in the DYT1 gene (904_906delGAG) who had severe head tremor in the frame of a generalized limb dystonia.

Cervical Dystonia

Cervical dystonia, which is the most common form of focal dystonia, presents with sustained neck spasms, abnormal head posture, head tremor, and pain. One of the interesting and unique features of cervical dystonia is the geste antagoniste. There is not a well-described pathophysiology for cervical dystonia, but several hypotheses report involvement at the central and peripheral level. Treatment options include: oral medical therapy, botulinum toxin injection, and surgery. Oral medical therapy has limited efficacy in control of the symptoms of cervical dystonia. Two types of botulinum toxin, types A and B, are being used for treatment of cervical dystonia, with equivalent benefit. Surgery is an option when other treatments fail or become ineffective. The surgical procedures are brain lesioning, brain stimulation, and peripheral surgical intervention. Several trials are currently ongoing in the United States and Europe to evaluate the efficacy of deep brain surgery in cervical dystonia.

Dystonia

Dystonia is a disorder of involuntary sustained muscle contractions. It is commonly classified by age of onset, distribution of involved body regions, and etiology. The pathophysiolgy of this condition is complex and imperfectly understood. This article reviews the epidemiology, genetics, clinical features, and approach to diagnosis and treatment of dystonia.

Report from a U.S. conference on essential tremor

Seventy researchers met in Washington, DC, on 20-21 October 2005 to identify and discuss the most pressing research issues in essential tremor (ET). The conference attendees concluded that the following six objectives are of immediate and overriding importance: (1) a collaborative network of research centers; (2) an international committee for developing a standard protocol for the diagnosis and quantification of ET; (3) the identification of one or more genes for ET; (4) a centralized repository of DNA and, ideally, immortalized cell lines from well-characterized ET families and healthy controls; (5) a reliable and efficient repository of optimally prepared and categorized brain samples for hypothesis-driven neuropathological examinations in well-characterized ET patients; and (6) animal models of ET for screening promising drugs. The conference attendees hope that this statement from the United States will engender international collaboration in finding a cure for ET.

Head tremor in dentatorubral-pallidoluysian atrophy

Dentatorubral-pallidoluysian atrophy (DRPLA) is a rare autosomal-dominant neurodegenerative disorder characterized by variable combination of clinical manifestations including ataxia, myoclonus, seizures, dementia, and choreic movements. Head tremor has been rarely reported. We report a 66-year-old-woman with genetically determined DRPLA who presented with head tremor. A "no-no" type head tremor was the initial and the most prominent symptom, and mild cerebellar signs and choreic movements were also observed later. Neither hand tremor nor dystonia was noted. The patient did not show dementia, myoclonus, or seizures. Surface electromyogram (EMG) revealed 3.5-4 Hz rhythmic EMG bursts in both sternocleidomastoid muscles. DNA analysis disclosed expanded trinucleotide repeats (n = 54) in the DRPLA gene. We suggest that isolated head tremor can be a clinical manifestation of DRPLA.

Pathophysiology of nonparkinsonian tremors

Patients with nonparkinsonian tremors are the second largest group treated with functional neurosurgery. We summarize the present pathophysiological knowledge of these conditions. Essential tremor (ET) may be due to oscillations within the olivocerebellar circuit. There is experimental evidence from animal models for such a mechanism, and clinical data indicate an abnormal function of the cerebellum in ET. Cerebellar tremor may be closely related to the tremor seen in advanced ET. The malfunction of the cerebellum causes a pathological feed-forward control. Additionally an oscillator within the cerebellum or its input/output pathways may cause cerebellar tremor. Almost nothing is known about the pathophysiology of dystonic tremor. Holmes tremor is based on a nigral and a cerebellar malfunction and presents clinically as the combination of tremor in Parkinson's disease and cerebellar tremor. Neuropathic tremor can be extremely disabling and is thought to be due to an abnormal interaction of the disturbances within the periphery and abnormal cerebellar feedback. Unlike the case of Parkinson's disease, functional neurosurgery of nonparkinsonian tremors is not yet based on a solid pathophysiological background.

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.

Nonparkinsonian tremors

Tremors other than those associated with Parkinson's disease are commonly encountered in clinical practice. The differentiation of tremor subtypes depends primarily on the presence of distinct clinical characteristics and is facilitated by the use of consistent nomenclature. Such differentiation can be helpful in determining the etiology of the tremor and assist in its management. In this review, the authors outline recently proposed changes to classification and review the clinical features, differential diagnosis, and current therapy for nonparkinsonian tremors.

A Yorkshire family with adult-onset cranio-cervical primary torsion dystonia

Although a family history is described in approximately 20% of patients, large families with adult-onset craniocervical primary (idiopathic) torsion dystonia (PTD) are rare. We report a new British family with cranio-cervical dystonia. Seventeen members of the family were examined. Five cases were diagnosed as definite PTD and one as probable PTD. Mean age at onset was 29 years (range, 19-40 yrs). The phenotype was characterized by adult-onset cranio-cervical dystonia in all affected cases. A few cases had additional voice tremor and/or postural arm tremor. The GAG deletion in the DYT1 gene was excluded in the index case. Linkage analysis was performed between the disease and several marker loci spanning DYT6 and DYT7 regions, and haplotypes were reconstructed in all subjects. Although linkage analysis was not completely informative, reconstructed haplotypes excluded linkage between the disease and either DYT6 or DYT7. This report confirms that familial cranio-cervical dystonia is genetically heterogeneous, and further studies of other PTD families with similar clinical features are needed to identify other new genes.

Quantification of sensory trick impact on tremor amplitude and frequency in 60 patients with head tremor

Head tremor with an obvious head deviation is the typical clinical picture of tremulous cervical dystonia (TCD), whereas head tremor without any significant head deviation allows for the differential diagnosis of dystonic head tremor (DHT) as well as essential head tremor (EHT). Clinical and polyelectromyographic (poly-EMG) studies have shown a suppression of dystonic muscle activity in patients with TCD performing a maneuver called geste antagonistique. The effect of these trick maneuvers on head tremor has not been investigated in patients with DHT and EHT. We studied the impact of sensory trick maneuvers on head tremor amplitude and frequency clinically by using the tremor subscore of the Tsui scale and by means of computer-based accelerometry in 60 patients with head tremor as their major disorder. Based on clinical data (modified Tsui scale: rating of spontaneous head deviation [rotation + lateroflexion + ante-/retroflexion]), pharmacologic response of tremor (propranolol, primidone, or alcohol), family history (postural hand tremor in first-degree relatives), and poly-EMG findings (reciprocal inhibition in neck muscles during voluntary head rotation), 34 patients were diagnosed as having TCD, 14 were classified as having DHT, and 12 patients were diagnosed as having EHT. Using a clinical rating scale, head tremor amplitudes showed a significant decrease compared with baseline during the performance of sensory trick maneuvers in patients with TCD and DHT, but not in patients with EHT. This clinically observed effect was accompanied by a significant reduction in the mean peak power of the dominant frequency in patients with TCD (decrease by 83%, p = 0.0001) and DHT (decrease by 90%, p = 0.01), but not in patients with EHT (decrease by 6%, p = 0.6). Head tremor frequencies showed no significant changes in relation to the trick maneuvers. We conclude that a significant reduction of head tremor amplitude during a sensory trick maneuver is a useful quantitative criterion to distinguish TCD and DHT from EHT.

Pattern of premature degenerative changes of the cervical spine in patients with spasmodic torticollis and the impact on the outcome of selective peripheral denervation

OBJECTIVES

To characterise the pattern of and risk factors for degenerative changes of the cervical spine in patients with spasmodic torticollis and to assess whether these changes affect outcome after selective peripheral denervation.

METHODS

Preoperative CT of the upper cervical spine of 34 patients with spasmodic torticollis referred for surgery were reviewed by two radiologists blinded to the clinical findings. Degenerative changes were assessed for each joint separately and rated as absent, minimal, moderate, or severe. Patients were clinically assessed before surgery and 3 months postoperatively by an independent examiner using standardised clinical rating scales. For comparison of means a t test was carried out. To determine whether an association exists between the side of degenerative changes and type of spasmodic torticollis a chi(2) test was used. Changes in severity, disability, and pain before and after surgery were calculated using a Wilcoxon matched pairs signed ranks test.

RESULTS

Fourteen out of 34 patients had moderate or severe degenerative changes. They were predominantly found at the C2/C3 and C3/C4 level and were significantly more likely to occur on the side of the main direction of the spasmodic torticollis (p = 0.015). There was no significant difference in age, sex, duration of torticollis, overall severity, degree of disability, or pain between the group with either no or minimal changes and the group with moderate or severe changes. However, in the second group the duration of inadequate treatment was longer (10.1 v 4.8 years; p=0.009), head mobility was more restricted (p = 0.015), and head tremor was more severe (p = 0.01). At 3 months postoperatively, patients with n or minimal degenerative changes showed a significant improvement in pain and severity whereas no difference was found in those with moderate or severe changes.

CONCLUSIONS

Patients with spasmodic torticollis have an increased risk of developing premature degenerative changes of the upper cervical spine that tend to be on the side towards which the head is turned or tilted and compromise outcome after surgery. Effective early treatment of spasmodic torticollis with botulinum toxin seems to have a protective effect. Patients with spasmodic torticollis and restricted head mobility who do not adequately respond to treatment should undergo imaging of the upper cervical spine. Patients with imaging evidence of moderate or severe degenerative changes seem to respond poorly to selective peripheral denervation.