Different subregional metabolism patterns in patients with cerebellar ataxia by 18F-fluorodeoxyglucose positron emission tomography

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.

Fig 1. Volume of Interest (VOI) template on the cerebellum of a normal sagittal ¹⁸F-FDG PET image includes 13 VOIs in bilateral anterior cortex, superior/mid/inferior posterior cortex, dentate nuclei (A), anterior vermis, and superior/inferior posterior vermis (B).

Fig 2. Representative images of spatially normalized ratios using study-specific templates of normal controls (A) and patients with crossed cerebellar diaschisis (B), multiple system atrophy of the cerebellar type (C), Spinocerebellar Ataxia (SCA) type 2 (D), and SCA type 6 (E).

Fig 3. Subregional metabolic ratios in normal controls and disease groups.

Metabolic ratios of anterior cortex (A), anterior vermis (B), right posterior cortex (C), left posterior cortex (D), posterior vermis (E), and dentate nuclei (F) were decreased in patients with multiple system atrophy of the cerebellar type (MSA-C) and spinocerebellar ataxia (SCA) type 2 and 6, compared to normal controls and those with crossed cerebellar diaschisis.

Fig 4. Coronal, sagittal, and transverse statistical parametric mapping images in patients with ataxia compared to normal controls (p < 0.001, FWE).

Patients with multiple system atrophy of the cerebellar type (MSA-C, A) and spinocerebellar ataxia (SCA) type 2 (B) show decreased metabolism of the entire cerebellum. Patients with SCA type 6 (C) show decreased metabolism mainly in the anterior and superior posterior lobes of the cerebellum.