In the paper by Davie et al in this issue (pp710–715),1 proton magnetic resonance spectroscopy and magnetisation transfer imaging were combined in a study of 18 patients with multiple sclerosis to determine whether the axonal loss in lesions of multiple sclerosis is correlated with the extent of demyelination.

Axonal damage is now often discussed as a likely cause of chronic disability in multiple sclerosis.2 3 But what is the cause of the axonal damage itself? It is tempting to speculate that it arises from injury secondary to a primary inflammatory response against myelin, but axonal injury in primary progressive multiple sclerosis …