Utility of the provisional clinical diagnosis as a basis for selection of computed tomographic or radionuclide brain scan.

Based on provisional clinical diagnosis, the choice of computed cranial tomography (CCT) or radionuclide brain scan (RBS) was retrospectively evaluated. In 1,333 selected cases, 551 had CCT only, 560 had RBS only, and 222 had both. CCT was the clinician's preference in cases of dementia, hydrocephalus, hemorrhage, aneurysm, arteriovenous malformation (AVM), primary tumor, visual abnormality, coma, and multiple sclerosis. RBS was preferred in headache, syncope, seizure, transient ischemic attack (TIA), metastatic disease, and encephalitis. Neither procedure appeared preferable in cases of psychosis, psychiatric disease, cerebral vascular accident (CVA), and abscess. Thirty-eight percent of CCTs yielded abnormal findings, not necessarily correlated with the provisional diagnosis. Thirty percent of RBS showed positive findings, mostly related to vascular abnormalities. On the basis of the provisional clinical diagnosis, CCT was more frequently requested for probable structural changes and RBS for probable perfusion abnormalities.