Retrograde crossed cerebellar atrophy.

Retrograde crossed cerebellar atrophy was present in 4 autopsied cases of severe unilateral destruction of the frontal lobe and thalamus. The thalamus, including the ventrolateral and ventromedial nuclei, had been severely damaged. Degeneration of thalamic afferent fibres with neuronal loss in the ipsilateral red nucleus, atrophy of the contralateral superior cerebellar peduncle and neuronal loss and atrophy of the contralateral dentate nucleus are described. These pathological changes are interpreted as the result of retrograde transsynaptic degeneration within the cerebellorubrothalamic tract following the unilateral thalamic and frontal cerebral, or thalamic lesions.