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. 2011 May;32(5):890-7.
doi: 10.3174/ajnr.A2387. Epub 2011 Mar 3.

Quantitative assessment of brain stem and cerebellar atrophy in spinocerebellar ataxia types 3 and 6: impact on clinical status

L Eichler  1 , B Bellenberg, H K Hahn, O Köster, L Schöls, C Lukas
Affiliations

Quantitative assessment of brain stem and cerebellar atrophy in spinocerebellar ataxia types 3 and 6: impact on clinical status

L Eichler et al. AJNR Am J Neuroradiol. 2011 May.

Abstract

Background and purpose: 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.

Materials and methods: 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.

Results: 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.

Conclusions: 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.

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Figures

Fig 1.
Fig 1.
Example of quantitative brain stem volumetry. Upper left: 3D segmentation of the brain stem. Lower left and middle: brain stem segmentation in orthogonal views. The borders of the brain stem are defined according to the method proposed by Luft et al. Right: midsagittal view showing anatomic landmarks.
Fig 2.
Fig 2.
Effect of the correction for natural aging on the cerebellum volume. Lines represent the linear regression within the control group and SCA subgroups of age. Cerebellar volumes before (A) and after (B) age correction; age dependence is fully compensated in the control group and reduced in the patient groups.
Fig 3.
Fig 3.
Sagittal T1-weighted images of the brain stem in patients with SCA and in a healthy control subject. Brain stem atrophy is clearly visible in SCA3 and to a lesser extent in SCA6. Note the marked atrophy of the cerebellum in SCA6.
Fig 4.
Fig 4.
Linear regression graphs illustrating the relationship between ICARS score and cerebellar (A) and brain stem (B) volume for both subtypes.
See this image and copyright information in PMC

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