Incomplete Unilateral Horner's Syndrome Due to Superior Vena Cava Compression Syndrome Caused by Small Cell Lung Carcinoma.

Incomplete unilateral Horner's syndrome due to central small cell lung cancer (SCLC) with consecutive compression of the superior vena cava has not been reported before. A 56-year-old woman with stage T4,N3(cerv),M1a metastatic central SCLC treated with carboplatin and etoposide developed incomplete Horner's syndrome before receiving the first cycle of chemotherapy. Investigation for ptosis ruled out myasthenic syndrome, myasthenia, primary myopathy, facial palsy, and mitochondrial disorders. After congestion developed in the upper inflow area and compression of the superior vena cava was noted, Horner's syndrome was attributed to superior vena cava compression syndrome (SVCCS). Stenting of the stenosis did not result in a complete resolution of Horner's syndrome. In summary, SVCCS can lead to congestion of the jugular veins and subsequent impairment of the centripetal sympathetic fibers that run along the carotid artery. Compression of the sympathetic fibers can lead to incomplete Horner's syndrome with non-fluctuating and non-exercise-induced ptosis. Clinicians should be aware that Horner's syndrome associated with SCLC may be due not only to a myasthenic syndrome but also, in rare cases, to a focal affection of sympathetic fibers.