Abstract
RATIONALE: One-and-a-half syndrome (OAAH) is characterized as the combination of ipsilateral horizontal gaze palsy and internuclear ophthalmoplegia. OAAH syndrome accompanied with 7th and 8th cranial nerve palsy is called 16-and-a-half syndrome. We aimed to report the case of 16-and-a-half syndrome with metastatic pons tumor. PATIENT CONCERNS: A 57-year-old male diagnosed with nonsmall-cell lung cancer (NSCLC) with brain metastasis occurring 15 months ago was referred to our clinic with the chief complaint of horizontal diplopia and right gaze palsy. DIAGNOSIS: According to the patient symptom, ocular examination, and radiographic findings, he was diagnosed as 16-and-a-half syndrome which was caused by brain tumor metastasis from NSCLC. INTERVENTIONS: We referred him to hemato-oncology department and he was treated with radiation and supportive therapy. OUTCOMES: Unfortunately, the patient passed away 1 month later without improvement of ophthalmoplegia. LESSONS: The clinical findings of our case indicate 16-and-a-half syndrome caused by brain tumor metastasis from NSCLC, which to our knowledge has not been previously reported. The case highlights a rare cause of OAAH spectrum disease and the importance of a systemic work-up including associated neurologic symptoms and brain imaging in patients with horizontal gaze palsy.