TENS is harmful in primary writing tremor

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.

Peripheral electrical stimulation to reduce pathological tremor: a review

Interventions to reduce tremor in essential tremor (ET) and Parkinson’s disease (PD) clinical populations often utilize pharmacological or surgical therapies. However, there can be significant side effects, decline in effectiveness over time, or clinical contraindications for these interventions. Therefore, alternative approaches must be considered and developed. Some non-pharmacological strategies include assistive devices, orthoses and mechanical loading of the tremorgenic limb, while others propose peripheral electrical stimulation. Specifically, peripheral electrical stimulation encompasses strategies that activate motor and sensory pathways to evoke muscle contractions and impact sensorimotor function. Numerous studies report the efficacy of peripheral electrical stimulation to alter tremor generation, thereby opening new perspectives for both short- and long-term tremor reduction. Therefore, it is timely to explore this promising modality in a comprehensive review. In this review, we analyzed 27 studies that reported the use of peripheral electrical stimulation to reduce tremor and discuss various considerations regarding peripheral electrical stimulation: the stimulation strategies and parameters, electrodes, experimental designs, results, and mechanisms hypothesized to reduce tremor. From our review, we identified a high degree of disparity across studies with regard to stimulation patterns, experimental designs and methods of assessing tremor. Having standardized experimental methodology is a critical step in the field and is needed in order to accurately compare results across studies. With this review, we explore peripheral electrical stimulation as an intervention for tremor reduction, identify the limitations and benefits of the current state-of-the-art studies, and provide ideas to guide the development of novel approaches based on the neural circuitries and mechanical properties implied in tremor generation.

Update on current and emerging therapies for dystonia

Treatment strategies for dystonia depend on the focal, segmental or generalized distribution of symptoms. Chemodenervation with botulinum toxin remains the treatment of choice for focal- or select-body regions in generalized and segmental dystonia. A potentially longer acting formulation of botulinum toxin is being investigated besides the currently available formulations. Electromyography increases toxin injection accuracy and may reduce injection number, frequency, side effects and costs by identifying dystonic muscle activity. Oral anticholinergics, baclofen and clonazepam are used off-label, but novel drugs in development include sodium oxybate, zonisamide and perampanel. Characterizing dystonia as a sensorimotor circuit disorder has prompted the use of noninvasive neuromodulation procedures. These techniques need further study but simultaneous rehabilitation techniques appear to also improve outcomes. Pallidal deep-brain stimulation is beneficial for medication-refractory primary generalized and possibly focal dystonia such as cervical dystonia. Certain genetic conditions are amenable to specific therapies and future gene-targeted therapies could benefit selected dystonia patients.

Research Priorities in Limb and Task-Specific Dystonias

Dystonia, which causes intermittent or sustained abnormal postures and movements, can present in a focal or a generalized manner. In the limbs, focal dystonia can occur in either the upper or lower limbs and may be task-specific causing abnormal motor performance for only a specific task, such as in writer’s cramp, runner’s dystonia, or musician’s dystonia. Focal limb dystonia can be non-task-specific and may, in some circumstances, be associated with parkinsonian disorders. The true prevalence of focal limb dystonia is not known and is likely currently underestimated, leaving a knowledge gap and an opportunity for future research. The pathophysiology of focal limb dystonia shares some commonalities with other dystonias with a loss of inhibition in the central nervous system and a loss of the normal regulation of plasticity, called homeostatic plasticity. Functional imaging studies revealed abnormalities in several anatomical networks that involve the cortex, basal ganglia, and cerebellum. Further studies should focus on distinguishing cause from effect in both physiology and imaging studies to permit focus on most relevant biological correlates of dystonia. There is no specific therapy for the treatment of limb dystonia given the variability in presentation, but off-label botulinum toxin therapy is often applied to focal limb and task-specific dystonia. Various rehabilitation techniques have been applied and rehabilitation interventions may improve outcomes, but small sample size and lack of direct comparisons between methods to evaluate comparative efficacy limit conclusions. Finally, non-invasive and invasive therapeutic modalities have been explored in small studies with design limitations that do not yet clearly provide direction for larger clinical trials that could support new clinical therapies. Given these gaps in our clinical, pathophysiologic, and therapeutic knowledge, we have identified priorities for future research including: the development of diagnostic criteria for limb dystonia, more precise phenotypic characterization and innovative clinical trial design that considers clinical heterogeneity, and limited available number of participants.

Occurrence of Writing Tremor in Patients With Scans Without Evidence of Dopaminergic Deficit

Asymmetric rest tremor is one of the main features of patients diagnosed with scans without evidence of dopaminergic deficit (SWEDD). Clinical and neurophysiological evidence suggests a dystonic origin of this tremor, although the underlying pathophysiology is still unclear. Dystonic tremor has a great tendency to vary with different postures or voluntary motor tasks. Here, we performed a phenomenological analysis of tremor in 14 patients with normal scans and in 14 tremor-dominant Parkinson's disease (PD) patients by assessing the presence of writing tremor. The Wilcoxon-Mann-Whitney's test revealed that patients with normal scans exhibit writing tremor more frequently, regardless of the side mostly affected by motor disturbances in handwriting (P < 0.01) and drawing (right hand: P = 0.01; left hand: P < 0.05). Our findings show that patients with asymmetric rest tremor and normal scans, contrarily to PD patients, present more commonly action tremor during writing tasks. This feature may thus be helpful to distinguish the two conditions.

Diagnosis and treatment of dystonia

The dystonias are a group of disorders characterized by excessive involuntary muscle contractions leading to abnormal postures and/or repetitive movements. A careful assessment of the clinical manifestations is helpful for identifying syndromic patterns that focus diagnostic testing on potential causes. If a cause is identified, specific etiology-based treatments may be available. In most cases, a specific cause cannot be identified, and treatments are based on symptoms. Treatment options include counseling, education, oral medications, botulinum toxin injections, and several surgical procedures. A substantial reduction in symptoms and improved quality of life is achieved in most patients by combining these options.

Epidemiology and treatment of 23 musicians with task specific tremor

BACKGROUND

Task specific tremors in musicians have been mainly described as primary bowing tremor in string instrumentalists in relatively small sample sizes. Our aim was to describe epidemiology, risk factors, phenomenology and treatment options of this disorder in 23 musicians of different instruments.

METHODS

We included 23 professional musicians (4 female, 19 male; mean age 51.5 ± 11.4 years) with a TSTM. During anamnesis, clinical examination, by mail or via telephone patients were asked for epidemiological, phenomenological information, risk factors and treatments. We then compared our findings to primary writing tremor, the most common task specific tremor.

RESULTS

Age at onset of the TST was 44.6 ± 13.6 years and tremor appeared 35.1 ± 13.5 years after beginning to play the instrument. The majority of patients were string instrumentalists, followed by woodwind instrumentalists. Other instrumentalists were a guitarist, pianist and percussionist respectively. In contrast to primary writing tremor, we also found proximal muscles of the upper extremity involved in tremor. A positive family history was found in Prior trauma was more common than in primary writing tremor. Treatment with a positive effect on tremor were in order of efficacy: Botulinumtoxin, Primidone, Propranolol, Trihexyphenidyl. No patient had undergone deep brain stimulation.

CONCLUSION

Task specific tremor in musicians is a heterogeneous disorder with a male gender predominance that shares many commonalities with PWT. The onset age as well as the time between starting to play the instrument and tremor onset has a wide range. Because previous trauma and overuse appear to be risk factors, preventive measures against playing related injuries are necessary. There appears to be a genetic predisposition for TST. No single beneficial medication exists and treatment of patients remains highly individual. It should be discussed, whether deep brain stimulation should be offered not only to patients that do not respond to any other medication but early in the course of the disease.

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.

The definition of dystonia: current concepts and controversies

The definition of dystonia has been a subject of much debate and controversy for the last century. In this paper, a practical definition of dystonia for the movement disorders expert is presented, based on a new algorithm. © 2013 Movement Disorder Society.

The non-motor syndrome of primary dystonia: clinical and pathophysiological implications

Dystonia is typically considered a movement disorder characterized by motor manifestations, primarily involuntary muscle contractions causing twisting movements and abnormal postures. However, growing evidence indicates an important non-motor component to primary dystonia, including abnormalities in sensory and perceptual functions, as well as neuropsychiatric, cognitive and sleep domains. Here, we review this evidence and discuss its clinical and pathophysiological implications.