A 32-year-old man started building a wooden desk atop Mount Fuji at an altitude of 3,776 m. Over the course of the second day, he developed lassitude and cough and experienced a headache that night; however, he continued to work. He was transported to our hospital with an altered level of consciousness. On arrival, chest radiography revealed increased opacities in both lungs, and magnetic resonance imaging (MRI) revealed a high-intensity signal in the splenium on diffusion-weighted imaging. He received mechanical ventilation following tracheal intubation. His respiratory function improved, and he was extubated on the fourth hospital day. Physical examination showed no motor weakness, and although he responded to verbal commands, he was unable to speak and was unresponsive to visual stimulation. On the seventh hospital day, head MRI showed improvement in the lesion in the splenium, although other signal changes were observed in the body of the corpus callosum. His verbal responsiveness and voice volume improved on a daily basis. Two months after the incident, he continued to experience mild recent memory disturbance. The patient described in this case report showed delayed signal changes in the body of the corpus callosum, possibly secondary to the onset of microbleed-induced edema.