--that is correct; when cell bodies die, they die.

Not all non-length dependent neuropathies are necessarily dorsal root ganglia attacks, though. This is somewhat controversial theoretically--there was a lively debate about it going on at Johns Hopkins, particularly, among the research faculty for some years (see papers by Drs. Moghekar, Cornbluth, McArthur, etc., especially as regards efficacy of skin biopsy to determine these conditions)--but it is thought that is some autoimmune, nutritional, and toxic conditions the biochemical reaction may occur at any point on the axon, not necessarily at the tips--but this is hard to distinguish from the idea that, all other things being equal, the nerve tips farthest from the seat of circulation would be more vulnerable to metabolic disruptions, simply because oxygen/nutrients have to travel more to get there, and more effort is needed to get rid of waste buildup.

Among the conditions in which there may be non-length dependent, non dorsal root ganglia involvement, besides the ones mentioned, are the ANA-associated autoimmunities (such as Lupus or Bechet's), ciguatera toxin, leprosy, (not common, fortunately), and celiac.

Also, of course, localized nerve compression or injuries can result in non-length depedent damage, such as in a brachial plexopathy or thoracic outlet syndrome. These are usually fairly evident if the right diagnostics are applied, though.