Middle cerebellar peduncles: Magnetic resonance imaging and pathophysiologic correlate

Figure 4 Immune reconstitution inflammatory syndrome and progressive multifocal leukoencephalopathy. HIV + JC virus, irregular antiretroviral therapy, with confusion and right sided weakness. Axial FLAIR (A) and axial post contrast (B) show abnormal signal in the bilateral MCP, greater on the right with associated enhancement; Axial post contrast (C) 2 mo after treatment with steroids and antiretroviral therapy show significant improvement of abnormal enhancement. IRIS might or might not be associated with an infectious process, in this case the abnormal enhancement in a patient with positive JC virus lead to the suspicious of a superimposed neoplastic process (lymphoma), other fungal or bacterial infection. Ultimately, the response to steroid gives the diagnosis of IRIS. IRIS: Immune reconstitution inflammatory syndrome; MCP: Middle cerebellar peduncles; HIV: Human immunodeficiency virus.