Extensive high T2 FLAIR signal with multiple scattered peripherally contrast-enhancing lesions which demonstrate no diffusion restriction of the central non-enhancing component. Some of these lesions involve the splenium, body and genu of the corpus callosum and extend to the walls of the lateral ventricle. No leptomeningeal enhancement.
Conclusion: In the setting of solid organ transplantation, these lesions are thought to represent primary CNS post-transplant lymphoproliferative disorder (PCNS-PTLD). The alternative diagnosis is that of metastases, although involvement of the corpus callosum and periventricular white matter make this less likely, especially in the absence of known malignancy.