A 63-year-old man presents to the emergency department because of transient symptoms of vertigo, slurred speech, diplopia, and paresthesia. He is symptom-free now, and clinical examination is entirely normal. His past medical history is significant for osteoarthritis, hypertension, and dyslipidemia. Which of the following is the most likely cause for symptoms?

Posterior circulation TIA is suggested by the constellation of symptoms (vertigo, dysarthria, and diplopia and the transient episode of his symptoms. The basilar artery is formed by the two vertebral arteries and supplies the pons, the midbrain, and the cerebellum with vertebrobasilar TIAs, tinnitus, vertigo, diplopia, ataxia, hemiparesis, and bilateral visual impairment are common findings. This patient does not have occlusion of the middle cerebral artery since it results in cortical symptoms of motor and sensory loss on the contralateral side. This is also not hypertensive encephalopathy since it causes confusion, headache, nausea, vomiting, and focal neurologic signs.