A 63-year-old man developed a transient episode 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 hypertension and dyslipidemia. Which of the following is the most likely cause for symptoms?

Posterior circulation TIA is suggested by the transient episodes. 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.