Stroke-like lesions with diffusion restriction can also result from bevacizumab administration to glioblastoma and metastases (Figs. 16.2 and 16.3). In addition, there is commensurate suppression of abnormal enhancement and normalization of perfusion in the areas of restricted diffusion. These lesions can manifest as early as 4 weeks after initiation of therapy and can persist for at least up to 80 weeks. The histopathology of such lesions consists of atypical necrosis and nuclear hypoxia-inducible factor 1-alpha upregulation, but no tumor recurrence. The cause of these alterations is still uncertain, but may entail atypical necrosis and chronic hypoxia. Other possible neuroimaging findings related to bevacizumab administration include nasal septal perforation and posterior reversible encephalopathy syndrome (Fig. 16.4). Although tumor hemorrhage has been reported with bevacizumab use, bevacizumab may not necessarily carry an increased risk for this complication since many tumors have a propensity to hemorrhage spontaneously.