Neuroanatomic and functional profile of fatigue in multiple sclerosis: an integrated morphofunctional study

Objectives: 1. to test the hypothesis of central and peripheral sensorymotor pathway involvement in MS fatigue; 2. to indentify novel neurophysiological variables suitable for objective fatigue evaluation. Methods: 20 MS patients equally distributed between fatigued and non-fatigued (cut-off score = 16 at the physical items of Modified Fatigue Impact Scale MFISphys) underwent: (1) clinical examination inclusive of the rating of Expanded Disability Status Scale, the 9-hole peg test and Beck Depression Inventory; (2) electro- and magnetoencephalographic recordings, with simultaneous electromyography tests; (3) brain MRI (collected within a comprehensive study funded by FISMGrant 2009/R/23). Results: Structural data indicated a major involvement of parietal areas in MS fatigue. Neurophysiological investigation indicated that the unbalance between somatosensory and motor areas activities increased with fatigue levels. Fatigue also correlated with corticomuscular coherence (CMC), a functional index of cortico-spinal coupling crucial for motor control. Conclusions: Our findings strengthen the hypothesis of sensory-motor pathway involvement in MS fatigue. Interestingly, somatosensory parietal regions seem to play a major role in sensorimotor communication distortion. Moreover, cortico-muscular coherence during a simple isometric gripping task emerges as a promising neurophysiological index sensitive to fatigue.