Anti-hu paraneoplastic syndrome presenting as bilateral sixth cranial nerve palsies

A 62-year-old woman presented with diplopia caused by bilateral sixth cranial nerve palsies. Two weeks later, she had bulbar weakness and ataxia. Brain magnetic resonance imaging showed non-specific abnormalities and spinal fluid was acellular but contained an elevated protein and oligoclonal bands. A paraneoplastic screen showed anti-Hu antibodies. Her clinical condition improved with immunoglobulin and systemic corticosteroid treatment. Breast cancer was diagnosed 21 months later by mammography but there were no metastases detected. Four and half years after the onset of her diplopia, she died of diffuse metastatic breast cancer. This is the first reported case of anti-Hu paraneoplastic brain stem encephalitis presenting with sixth cranial nerve palsies.