Ferric ion-ferrocyanide staining in ganglioside storage disease establishes that meganeurites are of axon hillock origin and distinct from axonal spheroids.

Ferric ion-ferrocyanide staining and safranin-0-counterstaining of neocortical tissue from cats with GM1 gangliosidosis have established that pyramidal neuron meganeurites occur proximal to axonal initial segments and that they are distinct from axonal spheroids. The latter, which were found to be widely distributed throughout cerebral cortex, were located distal to axonal initial segments and could be differentiated from meganeurites at both light and electron microscopic levels. This report confirms an earlier electron microscopic study which suggested that meganeurites are of axon hillock origin, and illustrates the striking distinction between abnormalities in the soma-dendritic and axonal domains of neurons in a lysosomal storage disease.