We report a case of a 63-year-old man who experienced his first manic episode, and then, one year later, experienced a second episode which was associated with a significant loss of brain parenchyma. Two computed tomography (CT) brain scans were performed at each manic episode to observe brain structure. Significant loss of brain parenchyma was shown using CT scans. A Mini-mental State Examination (MMSE) score of 29 was observed after the first manic episode and a score of 23 was obtained after the second manic episode. This case report supports the idea that an increased risk of developing dementia exists in patients with major affective disorders.