Reduced cardiac 123I-metaiodobenzylguanidine uptake in patients with spinocerebellar ataxia type 2: a comparative study with Parkinson’s disease

Abstract

Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant neurodegenerative disorder characterized by cerebellar ataxia, supranuclear ophthalmoplegia, and peripheral neuropathy. Autonomic nervous system dysfunction is often present. This study evaluated the cardiac sympathetic function in patients with SCA2 using (123)I-metaiodobenzylguanidine (MIBG) in comparison with patients with Parkinson's disease (PD) and control subjects. Nine patients with SCA2, nine patients with PD, and nine control subjects underwent (123)I-MIBG imaging studies from which early and late heart-to-mediastinum (H/M) ratios and myocardial washout rates were calculated. Early (F = 12.3, p < 0.0001) and late (F = 16.8, p < 0.0001) H/M ratios were significantly different among groups. In controls, early and late H/M ratios (2.2 ± 0.12 and 2.1 ± 0.20) were significantly higher than in patients with SCA2 (1.9 ± 0.23 and 1.8 ± 0.20, both p < 0.05) and with patients with PD (1.7 ± 0.29 and 1.4 ± 0.35, both p < 0.001). There was also a significant difference in washout rates among groups (F = 11.7, p < 0.0001). In controls the washout rate (19.9 ± 9.6%) was significantly lower (p < 0.005) than in patients with PD (51.0 ± 23.7%), but not different from that in SCA2 patients (19.5 ± 9.4%). In SCA2 patients, in a multivariable linear regression analysis only the Scale for the Assessment and Rating of Ataxia score was independently associated with early H/M ratio (β = -0.12, p < 0.05). (123)I-MIBG myocardial scintigraphy demonstrated an impairment of cardiac sympathetic function in patients with SCA2, which was less marked than in PD patients. These results suggest that (123)I-MIBG cardiac imaging could become a useful tool for analysing the pathophysiology of SCA2.