Interval appearance of glioblastomas not evident in previous CT examinations.

: This communication presents our experience with eight patients who were initially evaluated as having normal cerebral computed tomographic (CT) scans. Follow-up scans ranging from 2 to 9 months later showed interval appearance of large contrast enhancing mass producing lesions. All eight of these patients turned out to have glioblastoma multiforme. This phenomenon of "false-negative" CT does not seem to be dependent on the type of equipment used or the age of the patient. Negative CT should not dissuade radiologists and clinicians from believing that a patient with appropriate symptoms and signs does indeed harbor a brain tumor.