Abstract
Cerebellar and brain stem atrophy are important features in SCA3, whereas SCA6 has been regarded as a "pure" cerebellar disease. However, recent neuropathologic studies have described additional brain stem involvement in SCA6. We, therefore, aimed to investigate the occurrence and impact of regional infratentorial brain volume differences in patients with SCA3 and SCA6. Thirty-four patients with genetically proved SCA (SCA3, n = 17; SCA6, n = 17) and age-matched healthy control subjects (n = 51) were included. In all subjects, high-resolution T1-weighted images were acquired with a 1.5T MR imaging scanner. Individual brain stem and cerebellar volumes were calculated by using semiautomated volumetry approaches. For all patients with SCA, clinical dysfunction was scored according to the ICARS. Multiple regression analysis was used to identify the contribution of regional volumes to explain the variance in clinical dysfunction in each SCA genotype. Cerebellar volumes were lower in patients with SCA6 compared with controls and with those with SCA3. In contrast to controls, brain stem volume loss was observed in patients with SCA3 (P < .001) and, to a lesser extent, in those with SCA6 (P = .027). Significant linear dependencies were found between ICARS and cerebellum volume (SCA3: R(2) = 0.29, P = .02; SCA6: R(2) = 0.29, P = .03) and between ICARS and brain stem volume (SCA3: R(2) = 0.49, P = .002; SCA6: R(2) = 0.39, P < .01) in both subtypes. Both cerebellar and brain stem atrophy contributed independently to the variance in clinical dysfunction in SCA6, while in SCA3, only brain stem atrophy was of relevance. Our current findings in accordance with recent neuroradiologic and pathoanatomic studies suggest brain stem and cerebellar volume loss as attractive surrogate markers of disease severity in SCA3 and SCA6.
Highlights
AND PURPOSE: Cerebellar and brain stem atrophy are important features in SCA3, whereas SCA6 has been regarded as a “pure” cerebellar disease
Cerebellar volumes were lower in patients with SCA6 compared with controls and with those with SCA3
Both cerebellar and brain stem atrophy contributed independently to the variance in clinical dysfunction in SCA6, while in SCA3, only brain stem atrophy was of relevance
Summary
Thirty-four patients with genetically proved SCA (SCA3, n ϭ 17; SCA6, n ϭ 17) and age-matched healthy control subjects (n ϭ 51) were included. For all patients with SCA, clinical dysfunction was scored according to the ICARS. The following clinical parameters were surveyed for all patients: Degree of disability was scored according to the ICARS, which consists of the 4 subscales: I) posture and gait disturbances, II) kinetic functions, III) speech disorders, and IV) oculomotor disorders.[14]. MR Imaging Brain MR imaging was performed by using a 1.5T scanner (Magnetom Symphony; Siemens, Erlangen, Germany) to obtain sagittal highresolution T1-weighted (magnetization-prepared rapid acquisition of gradient echo) scans of the whole brain, with the following parameters: TE, 3.93 ms; TR, 1900 ms; TI, 1100 ms; flip angle, 15°; number of excitations, 1; resolution, 1 ϫ 1 ϫ 1.5 mm; matrix, 256 ϫ 256, 128 sagittal sections
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