Cerebellar ataxia associated with neuroendocrine thymic carcinoma and GAD antibodies

Cerebellar ataxia may arise as a consequence of autoimmune damage of the cerebellum. Adult patients with autoimmunity against the cerebellum often have an underlying neoplasm (paraneoplastic cerebellar degeneration). These patients commonly develop rapidly evolving severe ataxia and harbour serum and CSF onconeuronal antibodies (mainly anti-Hu, Yo, Ri, Tr). By contrast, antibodies to neuronal glutamic acid decarboxylase (GAD-Abs) have been reported in patients with a less severe form of non-paraneoplastic cerebellar ataxia.1 The finding of GAD-Abs in patients with paraneoplastic neurological symptoms associated with malignant tumours is very rare. Here we report a patient with thymic neuroendocrine carcinoma who developed progressive cerebellar ataxia with GAD-Abs. A 55-year-old man came to our attention in May 2007 because of gait instability. He smoked 40 cigarettes a day. There was no family history of neurological or autoimmune disorders. In December 2006 he started noticing imbalance that slowly progressed over months and prompted him to use a cane to walk. On examination he had mild scanning dysarthria, horizontal gaze evoked nystagmus and mild limb dysmetria and dysdiadochokinesia. His gait was …