Adult Onset Sporadic Cerebellar Ataxia in Singapore: Diagnostic Outcomes of Paraneoplastic Antibody Testing and Early Clinical Features of Paraneoplastic Cerebellar Degeneration.

Dear Editor, The initial presentation of cerebellar ataxia remains a diagnostic challenge due to its multiple etiologies, one of which is paraneoplastic cerebellar degeneration (PCD), a rare neurological disease. Although paraneoplastic antibody testing may be helpful, seronegative PCD may account for up to 50% of PCD cases.1 The causes of ataxia in the Asian population differ from that of the Western population – the proportion of multiple system atrophy of the cerebellar type (MSA-C) relative to MSA with predominant parkinsonism (MSA-P) is higher2 and Friedrich’s ataxia is rare.3 MSA-C can be difficult to diagnose at onset. In patients whose etiology cannot be determined, a diagnostic label of either idiopathic adult onset cerebellar ataxia (AOCA) or idiopathic late onset cerebellar ataxia (ILOCA) is usually applied. However, it is not uncommon for the etiology to remain unknown despite extensive investigations.4 This study aimed to determine the diagnostic outcomes in adult patients presenting with a subacute or chronic cerebellar ataxia for which the diagnosis was not readily apparent, thus, requiring paraneoplastic antibodies to be performed. We also investigated clinical features at onset that would allow us to distinguish PCD from sporadic degenerative ataxias.