Not a benign motor neuron disease: longitudinal imaging captures relentless motor connectome disintegration in Primary Lateral Sclerosis.

PLS is associated with relentlessly progressive motor connectome degeneration. Clinical disability in PLS is likely to stem from a combination of intra- and inter-hemispheric connectivity decline, primary-, pre-, and supplementary motor cortex degeneration. Simple "bedside" clinical tools, such as tapping rates, are excellent proxies of the integrity of the relevant fibres of the contralateral corticospinal tract.