Axonal lesions in multiple sclerosis: an old story revisited

The paper by Lovas et al. (2000) published in this issue of Brain is the latest in a series of studies dealing with axonal pathology in multiple sclerosis lesions. The recent re-emergence of interest by researchers in this aspect of multiple sclerosis pathology may at first seem to be at odds with the concept that defines multiple sclerosis as an inflammatory demyelinating disease of the central nervous system with (relatively) spared axons. The recognition that axonal damage occurs in multiple sclerosis lesions is, however, not new, as several of the classical studies documented axonal degeneration, described the presence of Wallerian degeneration and even attempted to quantitate axonal loss.The recent renaissance of interest in the axonal aspect of multiple sclerosis pathology has been chiefly initiated by a series of MRI, MR-spectroscopy and magnetization transfer imaging studies, which for the first time have provided non-invasive probes of pathology (McDonald, 1994; Davie et al. , 1995; Losseff et al. , 1996; Davie et al. , 1999). Several such studies have raised the possibility that (i) axonal pathology may be an early feature of multiple sclerosis, (ii) axon loss is likely to be a major cause of patients' permanent disability, and (iii) axonal pathology can be the major determinant of the development of the secondary …