Objective: Describe an infrequently encountered phenotypical presentation of Spinocerebellar ataxia (SCA)

Background: SCAs are a group of genetically diverse neurodegenerative disorders marked by high clinical heterogeneity.  While usually presenting with progressive gait/limb ataxia, dysarthria, or tremor, SCAs show very diverse phenotypic variations.  Isolated spastic paraparesis is rarely reported as a presenting syndrome.

Method: Case report and literature review

Results: A 52 year old adopted women with history of diabetes and treated cauda equina syndrome presented with progressive gait difficulties for 1.5 years. She started tripping, had balance issues on uneven/slanted surfaces, and lost the ability to run due to stiffness and unsteadiness.   She fractured her right ankle 6 months previous from a fall, and had a subsequent second injurious fall with facial injury. She complains of leg tightness, painful spasms in leg muscle, and fasciculations. Baclofen helped muscle tightness but doses were limited by cognitive effects for her employment. She denied upper body symptoms, speech or vision changes, dysphagia, or major. She had partial information from her birth family: biological father recently died from Parkinson’s disease with dementia in his 90s, and one half-brother has multiple hereditary exotosis (MHE). She has three healthy children.  Exam revealed isolated lower body spasticity and hyperreflexia, more on the left leg, without upper body, oculomotor or speech abnormalities. She had a spastic gait pattern with impaired tandem and turning.  Extensive brain/spine imaging and laboratory workup for spastic paraparesis from previous neurologists was negative, including extensive immune workup.  She did not respond to a levodopa challenge.  Consultation with geneticist resulted in whole genome sequencing given the more uncertain family history and broad differential diagnosis.   A CAG expansion with approximately 37 repeats in the ATXN2 gene was detected, which is associated with SCA-2.

Conclusion: Presentation of SCA mutations with isolated spastic paraparesis is rare, with isolated case reports in SCA type 2, 3, 7, 8, 28, though many reported cases have other signs described. Diagnosis may be confused with hereditary spastic paraplegia syndromes and may mimic other disorders such as multiple sclerosis or secondary myelopathy.  Genetic workup for this presenting syndrome should include analysis for SCA.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/sca-2-presenting-as-isolated-progressive-spastic-paraparesis/