Definitive diagnosis of MSA requires autopsy, but clinical criteria for diagnosis of SND and OPCA subtypes have been developed. The diagnosis of possible MSA, SND subtype may be made in any patient with parkinsonism and a poor response to levodopa therapy. The diagnosis of possible MSA, OPCA subtype may be made in any patient with a sporadic, adult-onset cerebellar syndrome associated with parkinsonism. Neuroimaging is generally unrevealing and used primarily to eliminate other causes for parkinsonism. In rare cases of OPCA significant brainstem and cerebellar atrophy may be seen.
Definitive evidence requires pathological confirmation at the time of autopsy.
In MSA, SND subtype one sees atrophy and discoloration in the putamina and depigmentation of the substantia nigra. Microscopically, there is severe neuronal loss and gliosis in the putamina, substantia nigra, globus pallidus, caudate, and subthalamic nucleus. Lewy bodies may rarely be found. In MSA, OPCA subtype one sees degeneration of the inferior olives, ventral pontine nuclei, and cerebellar cortex. And in MSA, SDS subtype the major pathologic lesion is found in the thoracic and upper lumbar intermediolateral gray column of the spinal cord, where sympathetic preganglionic neurons lie.