Functional cortical changes of the sensorimotor network are associated with clinical recovery in multiple sclerosis

Is a preserved functional reserve a mechanism limiting clinical impairment in pediatric MS patients?

We evaluated the functional magnetic resonance imaging (fMRI) correlates of simple movement performance in patients with pediatric multiple sclerosis (MS) and their relation with the extent of T2 lesion volume (LV), to improve our understanding of the mechanisms leading to their short/medium term favorable clinical course. We obtained fMRI during repetitive flexion-extension of the last four fingers of the right hand and brain dual-echo scans from 17 right-handed patients with pediatric relapsing-remitting MS and 9 sex- and age-matched right-handed healthy controls. T2 LV was measured using a local thresholding segmentation technique. fMRI activations and functional connectivity analysis were performed using SPM2. Compared to controls, pediatric MS patients had an increased recruitment of the left (L) primary sensorimotor cortex (SMC). They also showed reduced functional connectivity between the L primary SMC and the L thalamus (P = 0.03), the L insula and the L secondary sensorimotor cortex (SII) (P = 0.02), the supplementary motor area and the L SII (P = 0.02), the L thalamus and the L insula (P = 0.01) and the L thalamus and the L SII (P = 0.003). In patients with pediatric MS, the activity of the L primary SMC was significantly correlated with brain T2 LV (r = 0.78). No correlation was found between coefficients of abnormal connectivity and structural MRI measures. The maintenance of a selective and strictly lateralized pattern of movement-associated brain activations and a modulation of its functional connections suggest a preserved functional reserve in patients with pediatric MS, which, in turn, might contribute to explain their favorable clinical evolution at short/medium term.

Brain atrophy evolution and lesion load accrual in multiple sclerosis: a 2-year follow-up study

Background

To investigate in a large cohort of patients with multiple sclerosis (MS), lesion load and atrophy evolution, and the relationship between clinical and magnetic resonance imaging (MRI) correlates of disease progression.

Methods

Two hundred and sixty-seven patients with MS were studied at baseline and two years later using the same MRI protocol. Abnormal white matter fraction, normal appearing white matter fraction, global white matter fraction, gray matter fraction and whole brain fraction, T2-hyperintense, and T1-hypointense lesions were measured at both time points.

Results

The majority of patients were clinically stable, whereas MRI-derived brain tissue fractions were significantly different after 2 years. The correlation between MRI data at baseline and their variation during the follow-up showed that lower basal gray matter atrophy was significantly related with higher progression of gray matter atrophy during follow-up. The correlation between MRI parameters and disease duration showed that gray matter atrophy rate decreased with increasing disease duration, whereas the rate of white matter atrophy had a constant pattern. Lower basal gray matter atrophy was associated with increased probability of developing gray matter atrophy at follow-up, whereas gray matter atrophy progression over 2 years and new T2 lesion load were risk factors for whole brain atrophy progression.

Conclusions

In MS, brain atrophy occurs even after a relatively short period of time and in patients with limited progression of disability. Short-term brain atrophy progression rates differ across tissue compartments, as gray matter atrophy results more pronounced than white matter atrophy and appears to be a early phenomenon in the MS-related disease progression.