Silent infarction of the brain. Incidental finding demonstrated by SPECT

Bone imaging of the body is often requested to rule out metastatic disease. A patient with suspected breast carcinoma underwent bone imaging which revealed a focal area of uptake that appeared to be localized in the right posterior calvarium. The initial interpretation was possible solitary metastatic breast carcinoma to the skull. Skull radiographs and head computed tomography (CT) were suggested for follow-up evaluation. The skull series was performed immediately after bone imaging and was negative. Further clinical information revealed that the patient recently had undergone total right internal carotid artery ligation for treatment of a large, surgically inaccessible right cavernous aneurysm. SPECT imaging of the head localized the region of abnormal uptake adjacent to the calvarium, which suggested the uptake was due to a recent brain infarction or metastatic disease to the brain. A CT scan performed 4 days later demonstrated generalized cerebral atrophy, but was otherwise normal, ruling out metastatic breast carcinoma. This case emphasizes the importance of SPECT imaging when a solitary skull lesion is found on bone imaging. SPECT can localize the lesion to be within the brain and/or skull and can aid in further investigative management. A lesion located at the periphery of the brain may be due to an occult stroke. This finding is of particular consideration in the elderly in whom there is a relatively high incidence of coexisting cancer and silent brain infarction.