Brain white matter tracts degeneration in Friedreich ataxia. An in vivo MRI study using tract-based spatial statistics and voxel-based morphometry.
OBJECTIVE
Neuropathological examination in Friedreich ataxia (FRDA) reveals neuronal loss in the gray matter (GM) nuclei and degeneration of the white matter (WM) tracts in the spinal cord, brainstem and cerebellum, while the cerebral hemispheres are substantially spared. Tract-based spatial statistics (TBSS) enables an unbiased whole-brain quantitative analysis of the fractional anisotropy (FA) and mean diffusivity (MD) of the brain WM tracts in vivo.


METHODS
We assessed with TBSS 14 patients with genetically confirmed FRDA and 14 age- and sex-matched healthy controls who were also examined with voxel-based morphometry (VBM) to assess regional atrophy of the GM and WM.


RESULTS
TBSS revealed decreased FA in the inferior and superior cerebellar peduncles and the corticospinal tracts in the medullary pyramis, in WM tracts of the right cerebellar hemisphere and in the right occipito-frontal and inferior longitudinal fasciculi. Increased MD was observed in the superior cerebellar peduncles, deep cerebellar WM, posterior limbs of the internal capsule and retrolenticular area, bilaterally, and in the WM underlying the left central sulcus. Decreased FA in the left superior cerebellar peduncle correlated with clinical severity. VBM showed small symmetric areas of loss of bulk of the peridentate WM which also correlated with clinical severity.


CONCLUSIONS
TBSS enables in vivo demonstration of degeneration of the brainstem and cerebellar WM tracts which neuropathological examination indicates to be specifically affected in FRDA. TBSS complements VBM and might be a more sensitive tool to detect WM structural changes in degenerative diseases of the CNS.
Della Nave
Riccardo
R
Radiodiagnostic Section, Department of Clinical Physiopathology, University of Florence, Viale Morgagni 85, Florence, Italy.
Ginestroni
Andrea
A
Tessa
Carlo
C
Salvatore
Elena
E
Bartolomei
Ilaria
I
Salvi
Fabrizio
F
Dotti
Maria Teresa
MT
De Michele
Giuseppe
G
Piacentini
Silvia
S
Mascalchi
Mario
M
D000328:Adult; D001284:Atrophy; D001921:Brain / Q000473:pathology*; D001933:Brain Stem / Q000473:pathology; D005260:Female; D005621:Friedreich Ataxia / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009410:Nerve Degeneration / Q000473:pathology*; D011712:Pyramidal Tracts / Q000473:pathology*; D020824:Spinocerebellar Tracts / Q000473:pathology*