Spino-cerebellar fibers of the opossum Didelphis marsupialis virginiana

Abstract

Complete and partial spinal cord hemisections, one lesion per animal, were performed at cervical, thoracic, lumbar or sacral spinal cord levels in a series of 12 adult opossums. Following a survival time of 1–3 weeks, the brains and spinal cords were removed and stored in buffered formalin. The cerebella and brain stems were cut in the transverse, the sagittal or horizontal plane and subjected to either the Nauta-Gygax method or Fink-Heimer technique. In addition, the extent of each lesion was verified histologically. After cervical and thoracic hemisections, abundant fiber degeneration was present bilaterally in fairly distinct longitudinal rows within both the subcortical white matter and the adjacent granular layer of the anterior lobe. Also, degenerating fibers were present bilaterally within the granular layer of the posterior portion of the paramedian lobules and pyramis. The fibers which distributed to these areas were most abundant on the side of the lesion. Although lumbar and sacral lesions resulted in fiber degeneration within the same regions of the cerebellum, the fibers were fewer in number. This was particularly true in the pyramis and paramedian lobules. In all specimens degenerating fibers of fine diameter, judged to be collaterals from fibers passing into the granular layer, entered the nucleus fastigii, the nucleus interpositus and the medial portion of the nucleus dentatus. However, these were much more numerous after cervical and thoracic hemisections than after lumbar and sacral lesions.