Dizziness, unsteadiness and swaying of the body may be due to inadequate blood supply to the vertebrobasilar system. Patients with inadequate blood supply to the vertebral basilar artery system show signs and symptoms of cerebellar and brainstem ischemia and hypoxia, and may experience dizziness, nausea, vomiting, balance disorders and ataxia, as well as nystagmus and diplopia, and some patients may exhibit explosive speech. Alternatively, there may be cerebellar and brainstem hemorrhage, or cerebellar and brainstem infarction due to cerebrovascular disease. Patients with cerebellar and brainstem hemorrhage usually have an active onset and a high-density lesion on cranial CT. Patients with cerebellar and brainstem infarction, most of whom have onset of disease in a quiet state or during sleep, have low-density lesions on cranial CT. Insufficient blood supply to the vertebrobasilar system can occur in young people or in middle-aged and elderly people. Most young people are caused by mental stress and sleep disorders; middle-aged and elderly people usually have a history of atherosclerosis, and most patients have hyperlipidemia and diabetes mellitus.