A Review of Primary Writing Tremor

Approach to Tremor Disorders

Tremor disorders are diverse and complex. Historical clues and examination features play a major role in diagnosing these disorders, but diagnosis can be challenging due to phenotypic overlap. Ancillary testing, such as neuroimaging or laboratory testing, is driven by the history and examination, and should be performed particularly when there are other neurological or systemic manifestations. The pathophysiology of tremor is not entirely understood, but likely involves multiple networks along with the cerebello-thalamo-cortical pathways. Treatment options include medications, botulinum toxin, surgery, and nonpharmacologic interventions utilizing physical and occupational therapies and assistive devices. Further work is needed in developing accurate diagnostic tests and better treatment options for tremor disorders.

Primary Writing Tremor: Current Concepts

Primary Writing Tremor (PWT) is a type of task specific tremor which happens only while writing (Type A PWT) or assuming a writing position of the hand (Type B PWT). There is a considerable overlap of clinical features between PWT and writer's cramp which creates difficulty in diagnosing this condition in the clinic. PWT usually affects the dominant hand and is typically 5-7hz in frequency, worsened by anxiety, temporarily relieved by alcohol and associated with reduced writing speeds. There are a variety of hypotheses about the phenomenology of PWT (regarding whether it is a variant of essential tremor, focal dystonia or an independent entity). Unlike writer's cramp, PWT shows normal reciprocal inhibition of H reflex, does not exhibit excessive EMG activity in proximal muscles, and on fMRI shows underactivation of cingulum and overactivation of primary motor and supplementary areas. There are no randomised controlled trials currently for the treatment of PWT. Treatment modalities available are: medical treatment, botulinum toxin, surgical management (including DBS) as well as adaptive strategies and occupational therapy.

Tremor

PURPOSE OF REVIEW

Tremor may be defined as an involuntary movement that is rhythmic (ie, regularly recurrent) and oscillatory (ie, rotating around a central plane) and may manifest in a variety of ways; accordingly, tremor has a rich clinical phenomenology. Consequently, the diagnosis of tremor disorders can be challenging, and misdiagnoses are common. The goal of this article is to provide the reader with straightforward approaches to the diagnosis and treatment of tremors.

RECENT FINDINGS

Focused ultrasound thalamotomy of the ventral intermediate nucleus of the thalamus is an emerging and promising therapy for the treatment of essential tremor.

SUMMARY

The evaluation should start with a detailed tremor history followed by a focused neurologic examination, which should attend to the many subtleties of tremor phenomenology. Among other things, the history and examination are used to establish whether the primary tremor is an action tremor (ie, postural, kinetic, or intention tremor) or a resting tremor. The clinician should then formulate two sets of diagnoses: disorders in which action tremor is the predominant tremor versus those in which resting tremor is the predominant tremor. Among the most common of the former type are essential tremor, enhanced physiologic tremor, drug-induced tremor, dystonic tremor, primary writing tremor, orthostatic tremor, and cerebellar tremor. Parkinson disease is the most common disorder of resting tremor. This article details the clinical features of each of these disorders, as well as those of additional tremor disorders.

Treatment of a Patient With Task-Specific Writing Tremor Using Magnetic Resonance-Guided Focused Ultrasound

Task-specific dystonia is characterized by abnormal repetitive movements or postures in a specific body part that is triggered and ends with a task, such as writing. Failing medications, surgery, specifically disruption of key nuclei in the thalamus, can provide excellent symptomatic relief. Transcranial magnetic resonance (MR)-guided focused ultrasound is an emerging incision-less thermoablation technique. We describe MR-guided focused ultrasound tandem ablation of the ventral intermediate and ventralis oralis posterior nuclei in a 60-year-old patient with writer's cramp. The clinical improvement was immediate with incremental benefit from the latter lesion, which was sustained at 6 months follow-up.

Diagnosis and Management of Tremor

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Altered brain network measures in patients with primary writing tremor

PURPOSE

Primary writing tremor (PWT) is a rare task-specific tremor, which occurs only while writing or while adopting the hand in the writing position. The basic pathophysiology of PWT has not been fully understood. The objective of this study is to explore the alterations in the resting state functional brain connectivity, if any, in patients with PWT using graph theory-based analysis.

METHODS

This prospective case-control study included 10 patients with PWT and 10 age and gender matched healthy controls. All subjects underwent MRI in a 3-Tesla scanner. Several parameters of small-world functional connectivity were compared between patients and healthy controls by using graph theory-based analysis.

RESULTS

There were no significant differences in age, handedness (all right handed), gender distribution (all were males), and MMSE scores between the patients and controls. The mean age at presentation of tremor in the patient group was 51.7 ± 8.6 years, and the mean duration of tremor was 3.5 ± 1.9 years. Graph theory-based analysis revealed that patients with PWT had significantly lower clustering coefficient and higher path length compared to healthy controls suggesting alterations in small-world architecture of the brain. The clustering coefficients were lower in PWT patients in left and right medial cerebellum, right dorsolateral prefrontal cortex (DLPFC), and left posterior parietal cortex (PPC).

CONCLUSION

Patients with PWT have significantly altered small-world brain connectivity in bilateral medial cerebellum, right DLPFC, and left PPC. Further studies with larger sample size are required to confirm our results.

A preliminary study of the neuroanatomical correlates of primary writing tremor: role of cerebellum

INTRODUCTION

To explore the neuroanatomical correlates of primary writing tremor (PWT) and the role of cerebellum, using advanced structural neuroimaging. Till date, there are no studies exploring the gray and white matter changes using voxel-based morphometry (VBM) and diffusion tensor imaging (DTI) in PWT.

METHODS

Ten male patients with PWT were evaluated clinically and with magnetic resonance imaging. VBM and DTI images of patients were compared with that of 10 healthy male subjects. Spatially unbiased infra-tentorial template (SUIT) analysis was done to investigate the alterations of cerebellar gray matter. Region-of-interest analysis was performed on regions observed to be significantly different on DTI analysis.

RESULTS

The mean duration of illness and mean age of the patients were 3.5 ± 1.9 and 51.7 ± 8.6 years, respectively. On VBM analysis, the cluster of gray matter atrophy was found in bilateral cerebellar areas of culmen and left declive, right superior and medial frontal gyrus, bilateral middle frontal gyrus, bilateral anterior cingulate gyrus, and bilateral parahippocampal gyrus. DTI showed significantly reduced fractional anisotrophy of the anterior thalamic radiation, cingulum, and inferior fronto-occipital fasciculus in PWT patients compared to controls. The axial diffusivity, mean diffusivity, and radial diffusivity maps did not reveal any significant differences. On SUIT analysis, significant atrophy was found in right uvula and semilunar lobule in patients with PWT compared to controls.

CONCLUSIONS

Our study found that patients with PWT had predominant gray matter atrophy in parts of cerebellum and frontal lobe along with white matter changes of the cingulum and frontal lobe connections.

Improvement of Primary Writing Tremor in Parkinson's Disease with Carbidopa/Levodopa

Background

Primary writing tremor is a task-specific phenomenon that has been described as variants of essential tremor or dystonia.

Phenomenology Shown

We describe the case of a 63-year-old female who initially had primary writing tremor, later developed Parkinson’s disease, and once initiated on carbidopa/levodopa had improvement in her parkinsonism and her writing tremor.

Educational Value

As neither essential tremor nor typical brachial dystonia respond to carbidopa/levodopa, our case documents that at least some cases of primary writing tremor are not variants of either dystonia or essential tremor.

Dynamic decomposition of motion in essential and parkinsonian tremor

BACKGROUND

Treatment options for essential (ET) and Parkinson disease (PD) tremor are suboptimal, with significant side effects. Botulinum toxin type A (BoNT A) is successfully used in management of various focal movement disorders but is not widely used for tremor.

METHOD

This study examines complexity of wrist tremor in terms of involvement of its three anatomical degrees of freedom (DOF) in two common situations of rest and posture. The study examines tremor in 11 ET and 17 PD participants by kinematic decomposition of motion in 3-DOF.

RESULTS

Tremor decomposition showed the motion involved more than one DOF (<70% contribution in one DOF) in most ET (rest: 100%, posture: 64%) and PD (rest: 77%, posture: 77%) patients. Task variation resulted in change in both amplitude and composition in ET, but not in PD. Amplitude significantly increased from rest to posture in ET. Directional bias was observed at the wrist for ET (pronation), and PD (extension, ulnar deviation, pronation). Average agreement between clinical visual and kinematic selection of muscles was 55% across all subjects.

CONCLUSION

This study shows the complexity of tremor and the difficulty in visual judgment of tremor, which may be key to the success of targeted focal treatments such as BoNT A.