Objective: To report two cases of SCA3 who presented with cervical dystonia as a prominent feature or sole manifestation for many years prior to development of ataxia.

Background: Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease (MJD), is the most common form of SCAs in the world, which is characterized by cerebellar ataxia, pyramidal signs, and peripheral neuropathy. Dystonia was mostly present in the form of focal limb dystonia or generalized dystonia in SCA3. Cervical dystonia was rarely seen as the prominent or early manifestation in SCA3 patients.

Methods: Case 1 was a 39-year-old woman who presented with left rotation of her neck and intermittent head tremor for six months. Detailed medical history was taken and examination of cranial nerves, motor and sensory system was normal without any evidence of dysarthria and nystagmus. Alternating hand movements and tandem gait showed slightly disturbance. A positive family history was suspected that her father developed progressive unstable walking and dysarthria after age of fifty. Case 2 was a 67-year-old woman who was suffering from slowly progressive instability of stance and gait since one year ago. Neurological examination found her slurred speech, horizontal nystagmus, slow saccadic eye movement and trunk and limb ataxia. Resting tremor of the lower right limb was observed. What’s more, a mild tilt of her head to the right side with some inconspicuous head tremor was observed and which did her husband notice since twelve years ago. Her father and one elder sister developed gait disturbance at their seventies.

Results: Both cases undertook a battery of laboratory examinations, and the results of routine laboratory tests, including full blood count, liver and kidney function test, immunological tests, thyroid hormone levels and antibody, serum iron and ceruloplasmin concentrations were all normal. The brain magnetic resonance imaging (MRI) revealed both cases had cerebellar atrophy. Genetic tests of SCA were performed, and case 1 had a pathologic allele of 73 CAG repeats and case 2 had 66 CAG repeats within the ATXN3 gene.

Conclusions: These two cases reports suggest: 1) Cervical dystonia can be the predominant feature combined with mild ataxia in SCA3 patients. 2) Focal cervical dystonia might be the first symptom for many years prior to development of ataxia in SCA3 patients. 3) Untypical family history was usually neglected due to phenotypic variability among patients of the same family.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/cervical-dystonia-priori-to-ataxia-in-spinocerebellar-ataxia-type-3-patients/