Diffusion tensor imaging of spinocerebellar ataxias types 1 and 2

Neuroimaging in dementia

Although dementia is a clinical diagnosis, neuroimaging often is crucial for proper assessment. Magnetic resonance imaging (MRI) and computed tomography (CT) may identify nondegenerative and potentially treatable causes of dementia. Recent neuroimaging advances, such as the Pittsburgh Compound-B (PIB) ligand for positron emission tomography imaging in Alzheimer's disease, will improve our ability to differentiate among the neurodegenerative dementias. High-resolution volumetric MRI has increased the capacity to identify the various forms of the frontotemporal lobar degeneration spectrum and some forms of parkinsonism or cerebellar neurodegenerative disorders, such as corticobasal degeneration, progressive supranuclear palsy, multiple system atrophy, and spinocerebellar ataxias. In many cases, the specific pattern of cortical and subcortical abnormalities on MRI has diagnostic utility. Finally, among the new MRI methods, diffusion-weighted MRI can help in the early diagnosis of Creutzfeldt-Jakob disease. Although only clinical assessment can lead to a diagnosis of dementia, neuroimaging is clearly an invaluable tool for the clinician in the differential diagnosis.

Brain white matter damage in SCA1 and SCA2. An in vivo study using voxel-based morphometry, histogram analysis of mean diffusivity and tract-based spatial statistics

BACKGROUND AND PURPOSE

Neurodegeneration in spinocerebellar ataxia type 1(SCA1) and 2(SCA2) is associated with white matter(WM) damage. Voxel-Based Morphometry(VBM), histogram analysis of mean diffusivity(MD) and Tract-Based Spatial Statistics(TBSS) enable an in vivo quantitative analysis of WM volume and structure. We assessed with these 3 techniques the whole brain WM damage in SCA1 and SCA2.

PATIENTS AND METHODS

Ten patients with SCA1, 10 patients with SCA2 and 10 controls underwent MRI with acquisition of T1-weighted and diffusion tensor images. The results were correlated with severity of clinical deficit.

RESULTS

VBM showed atrophy of the brainstem and cerebellar WM without significant differences between SCA1 and SCA2. Focal atrophy of the cerebral subcortical WM was also present. Histogram analysis revealed increased MD in the brainstem and cerebellum in patients with SCA1 and SCA2 which in SCA2 was more pronounced and combined with mild increase of the MD in the cerebral hemispheres in SCA2. In SCA1 and SCA2 TBSS revealed decreased fractional anisotropy(FA) in the inferior, middle and superior cerebellar peduncles, pontine transverse fibres, medial and lateral lemnisci, spinothalamic tracts, corticospinal tracts and corpus callosum. The extent of tract changes was greater in SCA2 patients who also showed decreased FA in the short intracerebellar tracts. In both diseases VBM, histogram and TBSS results correlated with clinical severity.

CONCLUSIONS

Brain WM damage featuring a pontocerebeellar atrophy is similar in SCA1 and SCA2 but more pronounced in SCA2. In both diseases it correlates with severity of the clinical deficit.