Tremor in Spinocerebellar Ataxia: A Scoping Review

Case

A 48-year-old male patient presented with a gradually progressive unsteadiness of gait and tremor of both upper limbs for the past 5 years. His tremor progressed to the extent that he had to take support with both hands while writing or drinking. He belonged to the Agarwal community, and his mother, maternal uncle and grandfather had similar history of tremulousness and gait unsteadiness. Video 1 shows ataxia with impaired tandem gait, and tremor in both upper limbs with postural and intentional components.

Comment

This patient, belonging to the Agarwal community, showed prominent tremor with ataxia, and a positive family history. This clinical presentation was suggestive of SCA12, and genetic study confirmed a CAG repeat expansion mutation in the PPP2R2B gene responsible for SCA12. Along with the ataxic gait, tremor was a significant and troubling symptom.

Spinocerebellar ataxia type 12 (SCA12) is common in certain ethnic populations such as the Agarwal community in India

Tremor is the key clinical feature, present almost universally, and is often the initial manifestation

Most common form of tremor is postural (action) tremor in the upper limbs

Ataxia may not be prominent initially, hence misdiagnosed as essential tremor

Tremor may start unilaterally, and remain asymmetric

Rest tremor (with or without bradykinesia) is frequently present (associated postural tremor is usually not re-emergent)

Other forms of tremor include head tremor, and less frequently voice, jaw, lingual, and orofacial tremors, and truncal titubation

Dystonia is commonly associated, including dystonic tremor of the limbs and head

Neuroimaging shows prominent cortical and cerebellar atrophy

Lingual, Lip

Truncal

Lingual, Lip, Perioral

Palatal

Orthostatic

Levodopa responsiveness present in patients with typical parkinsonian features

Rate of ataxia progression faster in SCA2 with postural tremor

Truncal

Tremor on orthostatism

Levodopa responsiveness present in the ‘slow’ tremor

Association present between tremor and dystonia

Myoclonus may accompany action tremor

Ocular and palatal myoclonus (tremor)

Lingual

Combination of tremor and myoclonus

Presentation with parkinsonian phenotypes– PD, PSP, CBS, MSA–C

Voice

Lingual, jaw

Orofacial

Truncal

Tremor may be the initial symptom

Tremor is often asymmetric

Dystonia may be present– dystonic tremor, spasmodic dysphonia, cervical dystonia

Truncal

Dystonic tremor, cervical dystonia

Myoclonus– upper limbs, trunk, and head

Truncal

Tremor associated with dystonia or parkinsonism

Palatal

Single case report of isolated palatal tremor

Palatal

Lip

Palatal tremor is frequently present

Tremor may be the initial symptom

Postural tremor frequently noted in FGF14– related episodic ataxia

Postural tremor present in 16% of patients with FGF14 GAA–LOCA

Although allelic disorder to SCA15, head tremor is not commonly reported

Voice

Dystonic limb tremor, cervical dystonia

Voice

Cervical dystonia with dystonic head tremor is reported

Lingual

Myoclonus associated with tremor