Normal or non-diagnostic neuroimaging studies prior to the detection of malignant primary brain tumors.

We aimed to describe a single institution experience of neuroimaging failure to demonstrate malignant primary brain tumors. We retrospectively reviewed case histories for all newly diagnosed adult patients with malignant primary brain tumors treated at a single institution between 1 July 2006 and 30 June 2008. We specifically looked at patients in whom neuroimaging was normal or non-diagnostic at initial presentation. Among 193 patients with malignant primary brain tumors, there were 102 with World Health Organization (WHO) grade IV gliomas (glioblastoma multiforme, GBM), 54 with anaplastic gliomas, 18 with low grade gliomas, and 19 with primary central nervous system lymphomas (PCNSL). Initial imaging was normal in nine patients and abnormal but non-diagnostic in an additional eight patients with primary brain cancer. Normal or non-diagnostic neuroimaging was not uncommon among patients with GBM. Dramatic, rapid tumor growth is possible. Close interval clinical and radiographic follow-up can be important especially in the management of elderly patients presenting with seizures and non-diagnostic neuroimaging studies.