Paraneoplastic Opsoclonus-Myoclonus Syndrome as a Rare Presentation of Small-Cell Lung Cancer.

Opsoclonus-myoclonus syndrome (OMS), also known as Kinsbourne syndrome or dancing eyes syndrome, is an extremely rare neurological condition that comprises a heterogenous constellation of symptoms including opsoclonus along with diffuse or focal body myoclonus. It is usually referred to as a paraneoplastic entity, but it may also be associated to an infectious, metabolic, or idiopathic cause. Small-cell carcinoma of the lung is the most commonly reported malignancy associated with OMS. The authors describe a case of a 69-year-old male that presented with ataxic gait, phono- and photophobia, vertigo, dizziness, lethargy, nausea, and vomiting. During examination, rapid, multidirectional eye movements; slight dysarthria; and facial myoclonus were noted. He was admitted to the hospital, and after a thorough study, a diagnosis of OMS was established. Intravenous corticosteroids were started, alongside physiotherapy, and a slight improvement of his symptoms was noted. Imaging revealed a suspicious lesion in the left lung, along with lymphadenopathies and bone metastases. Histology confirmed the diagnosis of stage IV small-cell lung cancer (SCLC). Chemotherapy (ChT) with carboplatin and etoposide was started, and a gradual improvement of his neurological complaints was noted. After six cycles, the disease progressed, and second-line ChT with topotecan was started. After two cycles, the patient experienced significant clinical deterioration and eventually died. In conclusion, OMS is a poorly understood condition with uncertain neurological prognosis. The treatment of the primary neoplasm may improve neurological symptoms. The recognition of paraneoplastic syndromes is of utmost importance since early diagnosis of a malignancy relates to better outcomes.