Olivopontocerebellar atrophy: toward a better nosological definition.

Olivopontocerebellar atrophy (OPCA) is a pathological label implying not only olivopontocerebellar changes, but also cases with more widespread lesions involving the CNS. This polytopic pathological background accounts for clinical complexity, essentially defined as cerebellar-plus syndrome. The term "OPCA" is applicable to an increasing number of neurodegenerative syndromes, including autosomal dominant ataxia, complicated spastic paraplegia, multiple-system atrophy (MSA), and many cases of idiopathic late-onset cerebellar ataxia (ILOCA), some of whom also turn out to have MSA. OPCA may also be part of the pathological hallmark of other disorders, such as prion disorders, mitochondrial encephalomyopathies, and hereditary metabolic diseases. Sporadic OPCA and ILOCA with cerebellar-plus presentation and neuroimaging evidence of brainstem and cerebellar atrophy may represent interchangeable eponyms. Just a quarter of such cases evolve to MSA within 5 years of the onset of symptoms. Therefore, the assumption that MSA and sporadic OPCA necessarily are one and the same disease is no longer tenable. Our review suggests that the label "OPCA" is useful to designate a clinicopathological syndrome that has a variety of etiologies carrying a poor prognosis, particularly if associated with autonomic failure as occurs in MSA.