Abstract
We evaluated cerebellar subregional metabolic alterations in patients with cerebellar ataxia, a representative disease involving the spinocerebellum. We retrospectively analyzed 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) images in 44 patients with multiple system atrophy of the cerebellar type (MSA-C), 9 patients with spinocerebellar ataxia (SCA) type 2, and 14 patients with SCA type 6 and compared with 15 patients with crossed cerebellar diaschisis (CCD) and 89 normal controls. Cerebellar subregional metabolism was assessed using 13 cerebellar subregions (bilateral anterior lobes [ANT], superior/mid/inferior posterior lobes [SUPP/MIDP/INFP], dentate nucleus [DN], anterior vermis [ANTV], and superior/inferior posterior vermis [SUPV/INFV]) to determine FDG uptake ratios. MSA-C and SCA type 2 showed severely decreased metabolic ratios in all cerebellar subregions compared to normal controls (ANT, 0.58 ± 0.08 and 0.50 ± 0.06 vs. 0.82 ± 0.07, respectively, p < 0.001). SCA type 6 showed lower metabolic ratios in almost all cerebellar subregions (ANT, 0.57 ± 0.06, p < 0.001) except INFV. Anterior-posterior lobe ratio measurements revealed that SCA type 2 (Right, 0.81 ± 0.05 vs. 0.88 ± 0.04, p < 0.001; Left, 0.83 ± 0.05 vs. 0.88 ± 0.04, p = 0.003) and SCA type 6 (Right, 0.72 ± 0.05 vs. 0.88 ± 0.04, p < 0.001; Left, 0.72 ± 0.05 vs. 0.88 ± 0.04, p < 0.001) showed preferential hypometabolism in the anterior lobe compared to normal controls, which was not observed in CCD and MSA-C. Asymmetric indices were higher in CCD and MSA-C than in normal controls (p < 0.001), whereas such differences were not found in SCA types 2 and 6. In summary, quantitative analysis of cerebellar subregional metabolism ratios revealed preferential involvement of the anterior lobe, corresponding to the spinocerebellum, in patients with cerebellar ataxia, whereas patients with CCD and MSA-C exhibited more asymmetric hypometabolism in the posterior lobe.
Highlights
Cerebellar ataxia is clinically defined as a class of neurodegenerative disorders characterized by progressive degeneration of cerebellum and is often accompanied by a variety of neurological and systemic symptoms
Metabolic ratios of cerebellar subregions using occipital cortex as a reference for count normalization did not change with age (r = 0.141, p = 0.060 for anterior cortices (ANT); r = −0.033, p = 0.665 for SUPP)
Anterior-posterior lobe uptake ratios showed variable degrees of negative correlation with disease progression in patients with multiple system atrophy of the cerebellar type (MSA-C) and spinocerebellar ataxia (SCA) type 2, which revealed the preferential involvement of anterior lobe, whereas asymmetry in none of the patient groups were affected by disease duration
Summary
Cerebellar ataxia is clinically defined as a class of neurodegenerative disorders characterized by progressive degeneration of cerebellum and is often accompanied by a variety of neurological and systemic symptoms. Cases with later onset of a pure cerebellar syndrome due to a mutation in SCA6 may lack an obvious family history [1]. Kim et al reported that the ratio of patients with SCA mutations was high among those that met the diagnostic criteria for MSA based on clinical features, especially cerebellar dysfunctions [6]. Up to 20% of patients with sporadic adult-onset ataxia harbor a causative gene mutation, including a de novo mutation, despite a negative family history. Due to their heterogeneity, accurate diagnosis of cerebellar ataxias remains a clinical challenge [7, 8]
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