Figure 1.

Methylene blue-stained sections from supinator nerves. Supinator nerves showed morphologic abnormalities in two patients. Normal nerves showed fascicles containing large myelinated axons of relatively uniform size, myelin thickness and orientation (a); an abnormal nerve (b) with one fascicle mostly occupied by axons surrounded by markedly thickened; split or folded myelin (c) and one fascicle less affected (d). A severely affected nerve has a reduced large myelinated axon density (e,f) in addition to thickened, folded, distended myelin (f,g). Note the groups of small unmyelinated axons (arrowheads), small thinly myelinated axons (*), thinned myelin (#), intravascular mononuclear cells (+), blood vessels (B), adipose cells (A), perineurium (P), folded myelin (dashed arrows) split myelin (arrows). White boxes highlight regions of higher magnification bar = 200 μm (a,b,e), 20 μm (c,d,f–h).