Evolution of sporadic olivopontocerebellar atrophy into multiple system atrophy

OBJECTIVE: To determine the percentage of sporadic olivopontocerebellar atrophy (sOPCA) patients who later develop multiple system atrophy (MSA). METHODS: Observations of the course of 51 sOPCA patients 20 years of age or older initially evaluated in an ataxia clinic over 14 years and followed at 3- to 6-month intervals for 3 months to 10 years (median 2.5 years, interquartile range 5 months to 4 years). RESULTS: Seventeen patients evolved to develop MSA, whereas the remaining 34 manifested only progressively worsening cerebellar ataxia. The features of the MSA cases included autonomic failure and parkinsonism in 10 patients, autonomic failure without parkinsonism in six, and parkinsonism without autonomic failure in one. Using survival analysis methods, the authors estimated that 24% of subjects in this population will evolve to MSA within 5 years of the onset of sOPCA symptoms (95% CI 10% to 36%). An older age at onset of symptoms and a shorter time from onset of symptoms to first presentation in a neurology specialty clinic were both highly predictive of evolution to MSA. Six of the 17 patients who evolved to MSA died 4 months to 5 years after they had met diagnostic criteria for MSA. The estimated median survival time from time of transition was 3.5 years. In contrast, death occurred in only one of the 34 patients with sOPCA who did not evolve to MSA. Autopsy examination of all six patients with MSA who died confirmed the diagnosis. CONCLUSIONS: Approximately one-fourth of sporadic olivopontocerebellar atrophy patients will evolve to multiple system atrophy within 5 years, and this transition carries a poor prognosis for survival. Older age at onset of ataxia and earlier presentation in a neurologic specialty clinic predicted transition to MSA.