Spinocerebellar degeneration: Discrepancies between clinical and pathological diagnoses

To improve the diagnostic accuracy of sporadic spinocerebellar degeneration (SCD), we assessed the clinical and pathological data of 1494 consecutive autopsy cases. The number of patients who received a diagnosis of sporadic SCD (including multiple system atrophy) either clinically or pathologically was 19 (1.3%). We identified six cases with clinical misdiagnoses of SCD that were confirmed pathologically as progressive supranuclear palsy (PSP, four cases), basilar artery thrombosis (one case) and unclassified tauopathy (one case). The total number of patients who received a clinical diagnosis of sporadic SCD was 93 and the positive predictive value was 93.5%. We also identified 13 autopsy cases that were pathologically confirmed as SCD, but had been clinically misdiagnosed as having other disorders. Their clinical diagnoses comprised progressive supranuclear palsy (five cases) and Parkinson's disease (PD, four cases), as well as parkinsonism with dementia, amyotrophic lateral sclerosis, paraneoplastic syndrome and multiple cerebral infarction (one case each). The results indicate that it is often difficult to distinguish PSP and PD from SCD, because of the atypical combination of symptoms or atypical timing of the appearance of symptoms, such as severe autonomic failure, cognitive impairment, poor L-dopa responsiveness, early cerebellar signs and obvious vertical gaze palsy.