[A true aneurysm of the right internal mammary artery, accompanied by diminished grasping power of the right hand].

A 69-year-old man was admitted to our hospital after an abnormal shadow was found on a chest radiograph. The preoperative diagnosis was right subclavian aneurysm. Loss of grip in the right hand developed, and the patient underwent surgery. During surgery, the aneurysm was found to have originated from the right internal mammary artery. The root of the right internal mammary artery was tied and the right subclavian artery, which had been compressed and displaced by the aneurysm, was replaced. A chest radiograph obtained 6 months after surgery showed that the trachea was no longer displaced. However, the gripping force of the right hand had not recovered.