Dystonic Tremor and Spasmodic Dysphonia in Spinocerebellar Ataxia Type 12

Tremor in Spinocerebellar Ataxia: A Scoping Review

Background

Spinocerebellar ataxia (SCA) denotes an expanding list of autosomal dominant cerebellar ataxias. Although tremor is an important aspect of the clinical spectrum of the SCAs, its prevalence, phenomenology, and pathophysiology are unknown.

Objectives

This review aims to describe the various types of tremors seen in the different SCAs, with a discussion on the pathophysiology of the tremors, and the possible treatment modalities.

Methods

The authors conducted a literature search on PubMed using search terms including tremor and the various SCAs. Relevant articles were included in the review after excluding duplicate publications.

Results

While action (postural and intention) tremors are most frequently associated with SCA, rest and other rare tremors have also been documented. The prevalence and types of tremors vary among the different SCAs. SCA12, common in certain ethnic populations, presents a unique situation, where the tremor is typically the principal manifestation. Clinical manifestations of SCAs may be confused with essential tremor or Parkinson's disease. The pathophysiology of tremors in SCAs predominantly involves the cerebellum and its networks, especially the cerebello-thalamo-cortical circuit. Additionally, connections with the basal ganglia, and striatal dopaminergic dysfunction may have a role. Medical management of tremor is usually guided by the phenomenology and associated clinical features. Deep brain stimulation surgery may be helpful in treatment-resistant tremors.

Conclusions

Tremor is an elemental component of SCAs, with diverse phenomenology, and emphasizes the role of the cerebellum in tremor. Further studies will be useful to delineate the clinical, pathophysiological, and therapeutic aspects of tremor in SCAs.

Oromandibular dystonia – A systematic review

Oromandibular dystonia (OMD) is a clinical problem which is commonly encountered in the practice of movement disorders. OMD results from a variety of genetic and acquired etiologies and can occur as an isolated manifestation, or as part of an isolated generalized or a combined dystonia syndrome. There are only very few systematic reviews on this condition which often causes significant disability. We review here the etiology, clinical features, diagnostic approach and management of OMD.

Rest tremor in dystonia: epidemiology, differential diagnosis, and pathophysiology

BACKGROUND

The most common type of tremor reported in dystonia patients is postural and kinetic. There is uncertainty regarding the prevalence of rest tremor in dystonia.

OBJECTIVE

This review focuses on the clinical and neurophysiological features of rest tremor in dystonia, its differential diagnosis, and methods to distinguish it from other rest tremor syndromes.

METHODS

A PubMed search was done, and the available literature identified. Bibliography of the available literature was reviewed for relevant references.

RESULTS

Rest tremor in dystonia has been reported with a variable frequency of 1.81-12.05%. The most common body distribution is arm, and it tends to be asymmetric. Most of the affected patients have multifocal and segmental dystonia. Rest tremor is a late-onset phenomenon associated with severe and spreading dystonia. Clinically, it is difficult to distinguish rest tremor in dystonia from other rest tremor syndromes based on tremor characteristics; however, other neurological signs can provide clues to differentiate these syndromes. Surface electromyography and other neurophysiological tests can help differentiate the various rest tremor syndromes.

CONCLUSION

Rest tremor in dystonia can be differentiated from other rest tremor syndromes based on neurophysiological techniques. There is some evidence to suggest that SWEDDs could be a form of dystonic tremor, but further studies are required to clarify this diagnostic dilemma. Data regarding the treatment of rest tremor in dystonia are virtually nonexistent, and there is an urgent need for prospective studies focusing its medical management and to know the surgical targets.

Spasmodic dysphonia as a presenting symptom of spinocerebellar ataxia type 12

Autosomal dominant spinocerebellar ataxia (SCA) type 12 is a rare SCA characterized by a heterogeneous phenotype. Action tremor of the upper limbs is the most common presenting sign and cerebellar signs can appear subsequently. In many cases, minor signs, like dystonia, can be predominant even at onset. Laryngeal dystonia (spasmodic dysphonia) has been observed only in one case of SCA12 and never reported at disease onset. We present a 61-year-old female who developed spasmodic dysphonia followed by dystonic tremor and subsequent ataxia diagnosed with SCA12. Thus, spasmodic dysphonia can be a presenting symptom of SCA12.

Clinical Characterization of Genetically Diagnosed Cases of Spinocerebellar Ataxia Type 12 from India

https://onlinelibrary.wiley.com/page/journal/23301619/homepage/mdc312551-sup-v001_1.htm.

BACKGROUND

Spinocerebellar ataxia type 12 (SCA12) is a rare form of an autosomal-dominant ataxic disorder associated with an expansion of CAG repeat length. Here, we present a large case series of patients with SCA12 and describe a wide range of typical and rare symptoms.

METHODS

Twenty-one consecutive patients with genetically proven SCA12 underwent detailed neurological examination. We assessed clinical characteristics using validated rating scales for evaluating motor features in SCA. Nonmotor symptoms and quality of life were assessed using appropriate, validated scales. Correlations of CAG repeat length with both severity score and age of onset were explored.

RESULTS

The mean age of onset was 51 years, and most patients were descendants of a single, endogamous Indian community (Agarwal). Tremor was the most common initial presenting symptom (90%). Hand dystonia was present in 14 of 21 patients, and most patients in the cohort presented with gait disturbance. Neuropsychiatric manifestations were common coexisting features. The CAG repeat length was significantly correlated (r = -0.760; P = 0.0001) with early age of onset, but not with disease severity. Tremor affected the quality of life in 18 of 21 patients, because they had difficulty in handling liquids.

CONCLUSIONS

Tremor was the most common, nonataxic symptom at initial presentation in patients with SCA12. Proximal upper limb tremor, typically with high amplitude and low frequency, can raise a strong diagnostic suspicion. Associated hand dystonia was a common coexisting motor feature. Various nonmotor features were also observed in several cases which require therapeutic attention.

The role of cerebellum in patients with late onset cervical/segmental dystonia?--evidence from the clinic

BACKGROUND

There is evidence from animal studies, post-mortem pathology, functional imaging and neurophysiological studies to suggest that the cerebellum may be involved in the pathophysiology of dystonia. We sought to explore further the association of clinical and radiological abnormalities of the cerebellum in patients with dystonia.

METHODS

We retrospectively reviewed patients from our movement disorders research database, with predominant cervical dystonia who have been seen within last 6 months and had available routine magnetic resonance imaging (MRI). The clinical details including presence of cerebellar signs, imaging findings and results of investigations were recorded on a proforma. The results were analysed using percentages and means with standard deviation.

RESULTS

Out of 188 patients included 26 had evidence of cerebellar abnormality on neuroimaging. 17 patients showed cerebellar atrophy and 10 of these had cerebellar signs on examination. These patients were tested negative for common inherited ataxias. 9 patients had cerebellar lesions on MRI, reported as low grade tumour (n = 2), cerebellar infarct (n = 3), cyst (n = 2), white matter hyperintensity (n = 1) and ectopia (n = 1) out of these 4 had cerebellar signs.

CONCLUSION

The findings from our study suggest that there may be overt clinical or radiological cerebellar involvement in 14% of cases with cervical/segmental dystonia. However, larger prospective studies are needed in this context.

SCA 6 with Writer's Cramp: The Phenotype Expanded

Spinocerebellar ataxia type 6 (SCA6) presents typically with a pure cerebellar syndrome. Only 1 SCA 6 patient with writer's cramp has been reported on and a family history of ataxia and writer's cramp has never been reported on. Two other SCA6 patients with a shoulder girdle/hand dystonia and unspecified upper-limb dystonia with a family history of ataxia have been reported on. We report on the largest family with SCA6 and writer's cramp. The proband developed dysarthria, ataxia, and writer's cramp by age 37. His father presented with ataxia at 55, followed by writer's cramp and dysarthria. The proband's brother developed ataxia at 41, followed by dysarthria and writer's cramp. A paternal uncle (deceased; not examined) and 58-yr-old brother both developed pure ataxia (genetic testing is pending). This large family with complex movement disorder demonstrates that it is important to consider SCA6 in a patient presenting with an ataxia and writer's cramp and supports cerebellum involvement in dystonia.