BACKGROUND AND PURPOSE:Most DTI studies in ALS have been limited to the assessment of the CST damage. In this study, we used DTI tractography to investigate whether microstructural abnormalities occur in the major motor and extramotor WM tracts in mildly disabled patients with ALS.

BACKGROUND AND PURPOSE:Reliable markers to monitor PPMS are still needed. We investigated whether conventional and DTI measures of thalamic damage are predictive of long-term disability accumulation in PPMS.

We investigated whether conventional and diffusion tensor (DT) magnetic resonance imaging (MRI) features of the corticospinal tract (CST) contribute to the prediction of the long-term clinical evolution in patients with amyotrophic lateral sclerosis (ALS). Brain conventional and DT MRI were obtained from 18 healthy subjects and 24 patients with sporadic ALS. Mean diffusivity (MD) and fractional anisotropy (FA) of the CST were obtained. Patients were scanned at baseline, then entered a longitudinal clinical follow-up. The ALS Functional Rating scale (ALSFRS) progression rate during follow-up was estimated. Patients were followed up prospectively for a median period of 3.4 years. Two patients were lost at follow-up and eight died during the observation period. The mean ALSFRS progression rate was 0.7/month (range = 0.0–2.0/month). At baseline, ALS patients showed significantly increased MD and decreased FA of the CST compared with controls. CST FA was associated with ALSFRS progression rate. ALSFRS deterioration rate and CST FA were independent predictors of survival in ALS patients. Survival at year 3 was 42% in patients with CST FA ≤ 0.56 compared with 90% in patients with CST FA > 0.56. This study shows that more severe CST DT MRI abnormalities predict a poorer long-term clinical outcome in ALS patients. DT MRI of the brain has the potential to offer in vivo markers of disease severity.

Leber's hereditary optic neuropathy (LHON) is a mitochondrial disease characterized by retinal ganglion cell degeneration and optic nerve atrophy, leading to a loss of central vision. The aim of this study was to explore the topographical pattern of damage to the brain white matter (WM) tracts from patients with chronic LHON using diffusion tensor (DT) MRI and tract-based spatial statistics (TBSS). Brain dual-echo and DT MRI scans were acquired from 13 patients with chronic LHON and 25 matched controls using a 3.0 T scanner. TBSS analysis was performed using the FMRIB's Diffusion Toolbox. A complete neuro-ophthalmologic examination, including standardized automated Humphrey perimetry as well as average and temporal peripapillary retinal nerve fiber layer thickness (PRNFL) measurements, was obtained in all patients. Mean average and temporal PRNFL thicknesses were decreased significantly in LHON patients. Compared to controls, TBSS analysis revealed significant diffusivity abnormalities in these patients, which were characterized by a decreased fractional anisotropy (FA) and an increased mean diffusivity and radial diffusivity, affecting exclusively the optic tracts and optic radiations (OR). In patients, a significant correlation was found between optic tract average FA and mean visual acuity (r = 0.57, p = 0.04). In LHON patients, DT MRI reveals a microstructural alteration of the WM along the entire visual pathways, with a sparing of the other main WM tracts of the brain. Damage to the OR may be secondary either to trans-synaptic degeneration, which in turn is due to neuroaxonal loss in the retina and optic nerve, or to local mitochondrial dysfunction.

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