Sixteen-and-a-half syndrome with metastatic pons tumor: A case report

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. 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. 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. We referred him to hemato-oncology department and he was treated with radiation and supportive therapy. Unfortunately, the patient passed away 1 month later without improvement of ophthalmoplegia. 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.