Paraneoplastic brainstem encephalitis and subacute sensory neuropathy presenting various neurological symptoms associated with small cell lung cancer

Background. Paraneoplastic brainstem encephalitis and subacute sensory neuropathy are included in paraneoplastic neurological syndrome (PNS) and are rarely accompanied by small cell lung cancer. PNS is often difficult to diagnose or to treat them. Case. A 71 year-old man presented with syncope, diplopia, blepharoptosis and dysphagia and was admitted to our hospital. Brain MRI was normal. Chest CT showed mediastinal lymphadenopathy. The lymph node biopsy yielded a diagnosis of small cell lung cancer (cT4N2M0, stage IIIB). And as for the neurological symptoms, the presence of a serum anti-Hu antibody supported the diagnosis of paraneoplastic brainstem encephalitis and subacute sensory neuropathy. Platinum-based chemotherapy resulted in partial response but the neurological symptoms deteriorated. Conclusion. We reported a case of paraneoplastic brainstem encephalitis and subacute sensory neuropathy accompanied by small cell lung cancer. There are vari-ous types of paraneoplastic neurological syndrome, and further studies for the treatment of each neurological symptom are required.