"Grumose degeneration" of the dentate nucleus. A light and electron microscopic study in progressive supranuclear palsy and dentatorubropallidoluysial atrophy.

So-called "grumose degeneration" (GD) of the dentate nucleus (DN) which is a unique alteration in progressive supranuclear palsy and dentatorubropallidoluysial atrophy was studied by light and electron microscope. Light microscopically, the presence of a large amount of eosinophilic granular and/or amorphous material around the neurons is the most conspicuous feature of GD. In addition, the number of neurons is decreased and some of them are swollen as with central chromatolysis. Electron microscopically, the granular and/or amorphous material mainly consists of the altered axon terminals of the Purkinje cells (Pax), which are relatively electron-dense and characteristically contain varying numbers of deformed lamellar bodies, highly electron-dense mitochondria and many vacuoles which are adherent to the astrocytic processes. GD is a unique histological change of both the chromatolytic DN neurons and the grumose appearance of the altered Pax. Possible mechanisms are discussed.