Evaluation of imatinib mesylate efficacy in an index patient with a plexiform neurofibroma. Coronal magnetic resonance imaging scans (T1-weighted images with gadolinium contrast and fat saturation) of the head and oropharynx of a patient with NF1 patient with a plexiform neurofibroma before (A) and 3 months after (B) treatment with imatinib mesylate. The region of the tumor in the respective images is indicated. Reprinted from Yang et al²³  with permission from Elsevier.