A 33-year-old man presented with a lateral medullary infarction, vertigo, and nausea. At the time of hospital admission, he had Wallenberg syndrome. Although initial magnetic resonance imaging showed no abnormalities, subsequent diffusion-weighted magnetic resonance imaging showed a high-intensity area in the right lateral medulla oblongata. The right vertebral artery was shown to be dilated on basi-parallel anatomical scanning but to be stenosed on magnetic resonance angiography (MRA). Cerebral angiography 7 days after onset showed the "pearl and string sign" in the right vertebral artery. Follow-up MRA showed gradual improvement of the stenosis in the right vertebral artery. Multiple neuroimaging studies, such as MRA, basi-parallel anatomical scanning, 3-dimensional computed tomographic angiography, and cerebral angiography, should be performed soon after onset in suspected cases of cerebral artery dissection. In addition, serial imaging examinations increase diagnostic accuracy, and the medical history and neurological examination are important.