Objective: To present a Spinocerebellar Ataxia (SCA) 13 case who presented with parkinsonism with positive DatScan and good response to Levodopa.

Background: Spinocerebellar ataxia (SCA) is a progressive, autosomal dominant neurodegenerative disorder, which affects the cerebellum and its connected structures. As ataxia as a main feature in most cases, SCA can present heterogeneous clinical phenotypes. Parkinsonism has been reported in several SCA subtypes, especially in SCA2, SCA3, and SCA17. SCA 13 is rare, only a few cases reported to date. Missense mutations in KCNC3 gene were most common mutations in those cases.

Method: Case report

Results: A 72-year-old female presented to Neurology clinic with a decade history of progressive, generalized involuntary movements and gait disturbance. She complained of worsening of her gait in the past 3 years. Initial neurological exam revealed choreiform movement of bilateral upper limbs,
, truncal ataxia, dysmetria on both sides,  ataxic gait, dysarthria and slow horizontal saccade. Patient had history of major depression with suicidal attempt in the past.  She denied family history of neurological disorders. Works up including thyroid function, ceruloplasmin and liver panel were all unremarkable.
Genetic test for Huntington’s disease is negative. Brain MRI showed old infarct on right precentral gyrus otherwise unremarkable. Comprehensive ataxia panel showed a frame shift mutation on KCNC3 gene which led to the diagnosis of SCA 13. Asymmetric bradykinesia and rigidity was found on left upper limb on the following visit. DatScan was ordered which showed bilateral decrease uptake on the tail of striatum, worse on right side. Her bradykinesia and rigidity improved significantly after levodopa treatment, however, her ataxia and dysmetria remained the same.

Conclusion: SCA 13 is a rare autosomal dominant cerebellar ataxia. To our knowledge, our case is the first case presented with asymmetric parkinsonism with positive DatScan and good response to Levodopa. Frameshift mutation in KCNC3 gene has not been reported in the past either. The case we presented here provides further information in clinical phenotype and genotype in SCA 13 patient.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-case-report-of-spinocerebellar-ataxia-13-with-parkinsonism/