Extensive White Matter Alterations and Its Correlations with Ataxia Severity in SCA 2 Patients.
BACKGROUND
Previous studies of SCA2 have revealed significant degeneration of white matter tracts in cerebellar and cerebral regions. The motor deficit in these patients may be attributable to the degradation of projection fibers associated with the underlying neurodegenerative process. However, this relationship remains unclear. Statistical analysis of diffusion tensor imaging enables an unbiased whole-brain quantitative comparison of the diffusion proprieties of white matter tracts in vivo.


METHODS
Fourteen genetically confirmed SCA2 patients and aged-matched healthy controls participated in the study. Tract-based spatial statistics were performed to analyze structural white matter damage using two different measurements: fractional anisotropy (FA) and mean diffusivity (MD). Significant diffusion differences were correlated with the patient's ataxia impairment.


RESULTS
Our analysis revealed decreased FA mainly in the inferior/middle/superior cerebellar peduncles, the bilateral posterior limb of the internal capsule and the bilateral superior corona radiata. Increases in MD were found mainly in cerebellar white matter, medial lemniscus, and middle cerebellar peduncle, among other regions. Clinical impairment measured with the SARA score correlated with FA in superior parietal white matter and bilateral anterior corona radiata. Correlations with MD were found in cerebellar white matter and the middle cerebellar peduncle.


CONCLUSIONS
Our findings show significant correlations between diffusion measurements in key areas affected in SCA2 and measures of motor impairment, suggesting a disruption of information flow between motor and sensory-integration areas. These findings result in a more comprehensive view of the clinical impact of the white matter degeneration in SCA2.
Consejo Nacional de Ciencia y Tecnología-Cátedras-Instituto de Neuroetologia, Universidad Veracruzana, Mexico DF, Mexico.
Carlos R
CR
Hernandez-Castillo
Instituto de Neuroetologia, Universidad Veracruzana, Xalapa, Mexico.
Victor
V
Galvez
Cátedras Consejo Nacional de Ciencia y Tecnología, Área de Neurociencias, Departamento de Biología de la Reproducción, Universidad Autónoma Metropolitana, Mexico DF, Mexico.
Roberto
R
Mercadillo
Laboratorio de Neuropsicología, Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico DF, Mexico.
Rosalinda
R
Diaz
Unidad Periferica de Neurociencias, Facultad de Medicina Universidad Nacional Autonoma de Mexico/Instituto Nacional de Neurología y Neurocirugía, Mexico DF, Mexico.
Aurelio
A
Campos-Romo
Laboratorio de Neuropsicología, Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico DF, Mexico.
Juan
J
Fernandez-Ruiz
D000328:Adult; D001259:Ataxia / Q000175:diagnosis* / Q000473:pathology*; D016022:Case-Control Studies; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index; D066127:White Matter / Q000473:pathology*