Dementia-peripheral neuropathy during combined deficiency of vitamin B12 and folate. Light microscopy and ultrastructural study of sural nerve.

We present a case of a 56 year old woman who, in consequence of repeated surgical resections of the small bowel, developed a slowly progressive and mainly motor polyneuropathy affecting the lower limbs. The polyneuropathy due to a combined deficiency of vitamin B12 and folate, was associated with intellectual deterioration, involving especially the mnesic functions. Light microscopy and ultrastructural study of sural nerve revealed: marked reduction of every order of myelinated fibers: aspects of wallerian-like myelin degeneration; various stages of myelin leaflet delamination into the cytoplasm of Schwann cells and/or macrophages; lack of alterations attributable to a primary axonal degeneration. The morphological results suggest a primary demyelination, followed secondarily by either axonal changes or some aspects of wallerian-like degeneration.