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.