Grumose degeneration in the cerebellar dentate nucleus

It’s hard to find a picture of grumose degeneration in a textbook or online. I did, however, find one in an article by Yamanouchi et al. entitled “An Autopsy case of ornithine transcarbamylase deficiency” [Brain & Development 24 (2002) 91-94]. Grumose degeneration appears as eosinophilic granular material around dentate neurons. Neuropathologists usually think of grumose degeneration of the cerebellar dentate as an autopsy finding in progressive supranuclear palsy (PSP). But the authors of this article describe the same finding in a case of ornithine transcarbamylase deficiency, the most common heritable urea cycle disorder. They point out that although grumose degeneration was first described in a patient with PSP, it has also been reported in certain other neurodegenerative disorders, such as dentatorubropallidoluysian atrophy, Ramsay-Hunt syndrome, and juvenile Alzheimer disease with myoclonus. Ultrastructural studies have revealed that this eosinophilic material corresponds to degenerate Purkinje cell axon terminals. By the way, the word ‘grumose’, which can also be spelled ‘grumous’, means granular and refers to something that resembles grume, which is (according to Webster’s online dictionary) a thick, viscid fluid or clot-like material.