The Melanoneurons of the Human Cerebellum (Nucleus Pigmentosus Cerebellaris) and Homologues in the Monkey

Home , Cerebellum, Nucleus (neuroanatomy)

DAVID COWEN, M.D.

Abstract. Little has been written about the cells here termed cerebellar melanoneu Downloaded from https://academic.oup.com/jnen/article/45/3/205/2613680 by guest on 01 October 2021 rons. This paper describes and illustrates their cytologic features and topographic relationsh ips. In the human brain these large pigmented neurons are scattered in a narrow layer near the lateral wall, dorsal angle and roofofthe fourth ventricle. They form an inconspicuous part (group A4) of the system of catecholamine, neuromelanin containing cells well known in the brain stem. Rostrally, a few of them provide a tenuous continuity with the locus ceruleus but topographically the two nuclei are independent. With ordinary stains the cerebellar cells can be seen as early as the 26th week of gestation (the earliest period examined). Brown neuromelanin granules do not appear until two and a half years ofage but argentaffin granules, foreshadowing the production of pigment, are found in increasing numbers in the fetal and postnatal period. Homologues of the human cerebellar cells are reported in two species of monkey, Macaca nemestrina and Lagothrix sp. Neuromelanin, not previously ob served in non-human cerebellar cells, occurs in M. mil/alta and M. nemestrina. The proximity ofthe cerebellar melanoneurons to the ventricle raises the possibility that they are related to functions of the ependyma, or that they influence, or are affected by, constituents of the cerebrospinal fluid. The pathologic changes they undergo in Parkinson's disease and other disorders are to be described elsewhere.

Key Words: Catecholamine cells, group A4; Cerebellum, human; Cerebellum, mon key; Locus ceruleus; Melanoneurons; Neuromelanin; Nucleus pigmentosus cerebel laris.

INTRODUCTION The pigment-bearing nerve cells here termed cerebellar melanoneurons have re ceived little notice in neuroanatomical publications and virtually none in the field ofneuropathology. No substantial account of them has appeared since early in this century (I). This disregard is, perhaps, partly explained by the location of the cells in a site not regularly sampled in postmortem examinations, namely the roof and lateral wall of the fourth ventricle, and by the wide scattering of the cells, which minimizes the chance of encountering them in a casual thin section. In observing the cerebellar melanoneurons over a period of decades I have found that in Parkin son's disease some degenerate and disappear, and that Lewy bodies may appear in them. The cytopathologic changes occurring in Parkinson's disease and in some other circumstances, will be described in another report. Meynert made note of the cells as early as 1872 (2). Remarking on the locus ceruleus (his, and earlier writers', substantia ferrugineai, he stated that "black cells are also found . .. scattered in the roof of the fourth ventricle to the inner side of the superior cerebellar peduncle" (translation). He referred to them parenthetically

From the Division ofNeuropathology, Department of Pathology, College of Physicians and Surgeons, Columbia University, New York, New York. Correspondence to: David Cowen, M.D., Division of Neuropathology, Department ofPathology, Co lumbia University College of Physicians and Surgeons, 630 West 168th Street, New York, NY 10032. Supported in part by the Cremona Fund, Inc.

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