'Axogenic' and 'somagenic' neurodegenerative diseases: definitions and therapeutic implications

Neurodegenerative diseases are characterized by a relentless loss of specif ic groups of neuronal subtypes. Many of these diseases share similar molecu lar mechanisms and extracellular mediators of neuronal loss. We now suggest that neurodegeneration originating in the neuronal cell bodies (e.g. in Al zheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis) s hould be distinguished from that originating in the axons (e.g. in glaucoma , certain peripheral neuropathies and spinal stenosis). We propose that the former group of diseases be defined as "somagenic" and the latter as 'axog enic'. Although axogenic disorders may share common symptoms and mediators of toxicity with somagenic disorders, they have distinct temporal, subcellu lar and signal-transduction features. We further suggest that, by adopting this classification of disorders based on pathophysiological processes, we will come go recognize additional diseases (in particular, those defined as axogenic) as being neurodegenerative and therefore possibly amenable to ne uroprotective therapy.