The distribution of oligodendroglial inclusions in multiple system atrophy and its relevance to clinical symptomatology.

In this study a semiquantitative mapping of oligodendroglial cytoplasmic inclusions (GCIs), a feature of oligodendroglial degeneration in multiple system atrophy (MSA), was undertaken by means of a sensitive silver technique in 14 brains and 11 spinal cords of patients with various combinations of striatonigral degeneration, olivopontocerebellar atrophy and autonomic failure. The results show a system-bound extensive degeneration of interfascicular, perineuronal and perivascular oligodendrocytes. Oligodendroglial cytoplasmic inclusion-rich structures occur in the supra-segmental motor systems (primary motor and higher motor areas of cerebral cortex, 'pyramidal', 'extrapyramidal' and cortico-cerebellar systems), in the supraspinal autonomic systems and in their targets. In contrast, the visual and auditory pathways, olfactory structures, somatosensory systems, association and limbic cortical areas and subcortical limbic structures contain no or only a few GCIs. Comparison of the severity of oligodendroglial degeneration (GCI-density) with that of the neuronal alterations (neuronal cytoplasmic and nuclear inclusions, degenerated neuronal processes and loss of nerve cells) indicates a striking preponderance of oligodendroglial degeneration and that degeneration neither of axons, nor of neuronal cell bodies is a prerequisite of the development of GCIs. It also suggests that inclusion-bearing oligodendroglial degeneration may cause or contribute to the manifestation of clinical symptomatology in structures with GCI accumulation but without convincing neuronal alterations, i.e. cerebral motor cortical areas and reticular formation of the lower brainstem, both previously thought to be spared in MSA.