SCA 8 mimicking MSA-C

Excerpt

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.

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