Figure 1
Study selection flowchart for the literature review of dystonia in Spinocerebellar ataxia.
Figure 2
Dystonia phenotype distribution in the Spinocerebellar ataxia subtypes.
Table 1
Salient features of dystonia in different Spinocerebellar ataxia types.
| SCA SUBTYPE | SALIENT FEATURES |
|---|---|
| SCA1 | • Focal (common- cervical) >generalised>segmental • Task specific writer’s cramp • Generalised dystonic crises • Good response to botulinum toxin |
| SCA2 | • Cervical dystonia -most common • Lower cranial dystonia • Dystonia-parkinsonism • Levodopa responsive dystonia • Task specific writer’s cramp • Neonatal dystonia • Spasmodic dysphonia |
| SCA3 | • Younger age of onset • Lower face dystonia-common • Facial grimacing • Task specific writer’s cramp • Levodopa responsive dystonia • Severe truncal dystonia • Early onset tongue dystonia |
| SCA5 | • Unspecified |
| SCA6 | • Focal dystonia-common • Levodopa responsive dystonia • Tongue dystonia • Disabling dystonia • Task specific writer’s cramp |
| SCA7 | • Craniocervical-common |
| SCA8 | • Focal dystonia • Oromandibular dystonia • Limb dystonia |
| SCA10 | • Cervical dystonia |
| SCA11 | • Cervical dystonia |
| SCA12 | • Dystonic tremor • Spasmodic dysphonia • Focal hand dystonia • Feeding dystonia • Early childhood onset also reported |
| SCA13 | • Segmental dystonia |
| SCA14 | • Task specific writer’s cramp • Dystonic tremor • Dystonia-myoclonus • Dystonic trunk tremor |
| SCA17 | • Dystonia-chorea • Dystonia-parkinsonism • Focal dystonia-common |
| SCA19/22 | • Limb dystonia • Oromandibular dystonia • Dystonic tremor • Dystonia-myoclonus |
| SCA21 | • Dystonic tremor • Focal hand dystonia • Task specific writer’s cramp • Myoclonus-dystonia • Levodopa responsive dystonia |
| SCA28 | • Generalised dystonia • Spasmodic dysphonia |
| SCA29 | • Cervical dystonia • Segmental dystonia |
| SCA34 | • Segmental dystonia |
| SCA35 | • Dystonic tremor • Cervical dystonia • Good response to botulinum toxin |
| SCA36 | • Dystonic tremor • Cervical dystonia • Oromandibular dystonia |
| SCA44 | • Segmental dystonia |
| SCA48 | • Chorea-dystonia • Jaw-opening oromandibular dystonia • Cervical dystonia |
| SCA49 | • Cervical dystonia |
| SCA50 | • Appendicular dystonia |
[i] SCA- Spinocerebellar Ataxia, DBS- Deep Brain Stimulation, GPi- Globus Pallidus internus.
Figure 3
Heatmap showing the frequency of body region involvement in the Spinocerebellar ataxia subtypes (Green- minimum involvement, Red- involvement in increasing order).
Figure 4
Networks involved in the pathophysiology of dystonia in Spinocerebellar ataxia. DN- Dentate nucleus, GPe- Globus pallidus externus, GPi- Globus pallidus internus, ILM- Intralaminar nuclei, PN- Pontine nuclei, SNc – Substantia nigra pars compacta, SNr – Substantia nigra pars reticulata, Vim – Ventral intermediate nucleus, Vo – Ventral oral nucleus.
Figure 5
Treatment of dystonia in Spinocerebellar ataxia.
Table 2
Deep brain stimulation for dystonia in Spinocerebellar ataxia.
| STUDY (AUTHOR AND YEAR) | SCA TYPE | PATIENT CHARACTERISTICS | DBS TARGET | OUTCOME |
|---|---|---|---|---|
| Copeland BJ et al., 2014 [12] | SCA1 | • Craniocervical dystonia that was responsive to botulinum toxin injection • Progressed to the upper limbs and trunk involved • Baclofen, clonazepam not useful | Bilateral GPi | • Improvement of the dystonia • Right GPi- contacts 11–, 10+ with amplitude 2.2 V, pulse width 270 msec, and frequency 160 Hz • Left GPi- contacts 3–, 1+ with amplitude 2.0 V, pulse width 270 msec, and frequency 160 Hz • Amplitude increased over the first few month • Displayed some residual dystonia of the trapezius muscles and shoulders bilaterally that responded to botulinum toxin injection |
| Cheng N et al., 2018 [29] | SCA2 | • Initial symptom was difficulty writing with the right hand • Writer’s dystonia progressed to other activity of right hand | Left GPi | • Significant improvement in the dystonia • Monopolar device achieved optimal settings at- lead C + 0–, frequency of 165 Hz, voltage of 2.4 V and pulse width of 450 μs |
| Freund HJ et al., 2007 [131] | SCA2 | • Tremor of the arms, head and trunk • Torticollis | Subthalamic-thalamic (Vim, Vop, zona incerta and cerebello-thalamic projection) | • Stimulation was turned on at the third postoperative day • Tremor and torticollis significantly improved |
| Cui Z et al., 2023 [119] | SCA3 | • Cerebellar ataxia and dystonia • Slight bilateral hand tremor, balance disorder, and gait abnormality • Neck stiffness and facial dystonia | GPi, dentate nucleus | • Improvement was 42% in SARA, 30% in BFMDRS movement, and 12.5% in BFMDRS disability score • Patient was not satisfied with the improved symptoms or their quality of life. This eventually led to the patient’s request to remove the leads and abandon the implantation of the pulse generator |
| Ikezawa J et al., 2023 [124] | SCA3 | • Dystonia of the left lower limb • Dysarthria, oculomotor disturbances, and ataxia of the limbs and trunk additionally appeared, and had difficulty walking • Tizanidine, clonazepam, and botulinum toxin treatments were attempted but were ineffective | Right Vo, bilateral GPi | • DBS was performed on the right thalamic Vo nucleus for dystonia in the left upper and lower limbs • Upper and lower limbs markedly improved adequately to allow fine movement, such as holding a teacup • The pain greatly diminished as the dystonia symptoms improved • However, cerebellar ataxia remained unchanged • Stimulation effect did not persist in the long term. From the second year after surgery, dystonia in the left upper and lower limbs and cerebellar symptoms gradually worsened, and the pain, which had subsided, became more severe • Bilateral GPi DBS was added • 50-Hz frequency was the best to improve dystonia symptoms and it was well tolerated • 6 months later, painful dystonia in the left hand recurred, which did not improve despite various stimulation adjustments |
| • Painful dystonia in the left lower limb, progressed to painful dystonia in the right and left upper limbs • Levodopa, diazepam and other medications without success | Bilateral GPi | • No significant changes, except for a slight improvement in pain in the upper and lower limbs, were observed | ||
| • Left leg began to turn inwards only while walking • Painful dystonia was evident not only in the lower extremities but also in both the upper extremities | Bilateral GPi | • Patient was able to stand with assistance 1-month post-surgery owing to improvement in the apical foot position • 2 years postoperatively, painful dystonia in the left leg began to appear, which did not significantly improve despite stimulation adjustments | ||
| Muglan JA et al., 2016 [42] | SCA3 | • Pronounced anterocollis associated with right tilt and twist and minimal sagittal and lateral shift and intermittent dystonic tremor • There was fixed and painful dystonia with no change with posture | GPi | • Did not improve the condition |
| Aupy J et al., 2018 [130] | SCA3 | • Presented with cervical dystonia • Progressed to generalized dystonia involving the four limbs, the trunk and the face | Bilateral GPi | • Right lead, contacts 5 and 6, pulse width 210 μs, frequency 130 Hz, amplitude 2 V • Left lead, contacts 1 and 2, pulse width 210 μs, frequency 130 Hz, and amplitude 2.6 V • Patient was able to stand up without help and his swallowing improved • Cerebellar ataxia did not improve • Painful generalized dystonia progressively reccurred despite changes to the stimulation settings |
| Beaulieu-Boire I et al., 2016 [28] | SCA2 | • Generalised dystonia (predominantly axial and right upper limb) • Inadequate response to baclofen, benzodiazepine, BoNT, levodopa, tetrabenazine, trihexyphenidyl | Bilateral STN, GPi | • No significant improvement |
| SCA3 | • Segmental dystonia (predominantly cervical) | Bilateral GPi | • Some improvement | |
| Riso V et al., 2020 [129] | SCA14 | • Trunk and limb tremor • Dystonic tremor with marked axial involvement | GPi | • Partially effective on tremor |
| Wagle Shukla A et al., 2023 [128] | SCA17 | • Generalized dystonia and focal arm tremor | Bilateral GPi | • After surgery frequency 130 Hz, then reduced to 60 Hz • Improvement in dystonia, tremor • At 13 years of follow-up, although the ataxia has continued to worsen, DBS therapy has led to persistent improvements in dystonia, tremor |
| Oyama G et al., 2014 [138] | SCA17 | • Generalized dystonia, with a severe inversion of his left foot • Progressed to include a twisting of his neck and shoulders | Bilateral GPi | • Improvement of his upper extremity dystonic tremor • No improvement noted in his lower extremity dystonia • Dystonia scales continued to worsen at his 12-month follow-up and multiple DBS settings were attempted without dystonia and ataxia benefit |
| Keller Sarmiento IJ et al., 2025 [135] | SCA27A | • 58-year-old right-handed female patient • At age 3 years a hand tremor was noticed. Her gait became unstable at around the age of 33 years • At age 42 years she underwent bilateral STN-DBS | Bilateral STN | • Significant improvement in tremor • Over time, she developed right-hand dystonia, which was treated with botulinum toxin injection |
| Fasano A et al., 2017 [105] | SCA35 | • Dystonic hand tremor • Disabling action tremor of both upper extremities | Right Vim | • Initial improvement of tremor was not sustained |
[i] BFMDRS- Burke-Fahn-Marsden Dystonia Rating Scale, DBS- Deep Brain Stimulation, GPi- Globus Pallidus internus, SARA- Scale for the Assessment and Rating of Ataxia, SCA- Spinocerebellar Ataxia, STN- Subthalamic Nucleus, Vim- Ventral intermediate nucleus of thalamus, Vo- Ventral oral nucleus of thalamus.