Clinical indications for optimal use of the radionuclide brain scan.

427 radionuclide brain scans, performed in 1981 at Guy's Hospital Nuclear Medicine Department, were reviewed retrospectively to define clinical circumstances in which the study provided useful information. It was concluded that the radionuclide brain scan was the appropriate first line investigation in patients with known non-cerebral malignancy, in whom the possibility of cerebral metastases exists; and in patients with a low to moderate probability of subdural haematoma. The radionuclide brain scan can provide a valuable alternative to computed tomography studies:--(1) in patients without known underlying disease who develop localising signs; (2) in patients with focal fits; (3) in patients with underlying vascular disease and gradual onset of localising signs; and (4) in patients with suspected inflammatory conditions of the central nervous system. Outside these groups, the radionuclide brain scan rarely provided useful information.