SCA 8 mimicking MSA-C

Abstract

It is known that SCA-8 and the cerebellar form of Multisystem Atrophy (MSA-C) share several common clinical features. We present a 46-year-old woman with a 3-year history of gait instability, tremor and lack of coordination. Medical history was unremarkable. She complained of urinary urgency, had intermittent blue discoloration of the extremities and light-headedness when standing up, suggestive of orthostatic hypotension. Family history was relevant for a father with early onset tremor and a brother of her father diagnosed with Parkinson’s disease. Clinical examination revealed a moderate hypokinetic and hypophonic dysarthria, diffuse hyperreflexia, incoordination of limb movements and an asymmetrical Parkinsonism with bradykinesia and rigidity predominantly of the right arm. We also noted a systolic blood pressure decrease of 20 mmHg within 3 min of standing. Brain MRI demonstrated significant cerebellar atrophy, Fig. 1. Extensive laboratory analysis for ataxia, including paraneoplastic panel was negative. EMG/NCS was negative for polyneuropathy and motor neuron disease. CIT SPECT demonstrated a bilateral reduction of presynaptic dopaminergic transmission of the putamen, more pronounced on the right side, Fig. 2. An initial diagnosis of probable MSA-C was made. There was a poor and unsustained response to chronic levodopa therapy. Because of a possible positive family history molecular genetic analysis for SCA was performed and showed a combined 18/156 triplet CTA/ CTG repeat expansion at the SCA 8 locus. The clinical presentation of SCA8 is quite variable [1]. To our knowledge, three previous studies analysed the SCA 8 allele in patients with MSA-C. There was the patient group of Sobrido et al. where 13 of the 153 patients with familial and sporadic forms of ataxia were diagnosed with MSA-C [2], and the study group of Schöls et al. where 20 patients of the 124 fulfilled the criteria for probable MSA-C [3]. Neither study group found any molecular abnormalities in their MSA-C subgroup. In 2009, the study group of Munhoz et al. investigated the presence of expanded SCA 8 alleles in 10 sporadic patients with probable MSA-C and found one patient who presented with 22/76 repeats [4]. The pathogenicity of this triple repeat expansion was questioned since most studies suggest a repeat length above 80 to be in the abnormal range ([1], Table 1). However an ‘‘abnormal’’ repeat length is difficult

DOI: 10.1007/s13760-015-0523-z

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Cite this paper

@article{Smetcoren2015SCA8M, title={SCA 8 mimicking MSA-C}, author={Charlotte Smetcoren and Dorien Weckhuysen}, journal={Acta Neurologica Belgica}, year={2015}, volume={116}, pages={221-222} }