Posterior reversible encephalopathy syndrome (PRES) and CT perfusion changes

Posterior reversible encephalopathy syndrome (PRES), as the name suggests, is a constellation of symptoms caused by reversible ischemia most commonly of the posterior cerebral vasculature, thus affecting the parietal-occipital region. Still other vascular territories can be affected in PRES (see Table 1).Various terminologies have been used to describe this condition, including "reversible posterior leukoencephalopathy syndrome" and "reversible posterior cerebral edema syndrome" among others [1]. Hypertension (HTN) is the most commonly identified cause of PRES, followed by medications, eclampsia and systemic factors. The pathophysiology of HTN related PRES is due to a failure of cerebrovascular autoregulation, which in turn results in vasogenic edema. Non-hypertensive PRES may be due to an autoimmune or immune response to various stimuli [2]. The pathology usually affects the posterior brain hemisphere (parietal-occipital region), which may be a consequence of reduced sympathetic innervation in this area. Usually it is a reversible phenomenon, as indicated by the name, but if not recognized early and treated appropriately, permanent brain injury may ensue.A 70-year-old white female presented to the emergency room with symptoms of a cerebrovascular accident. She had a history of multiple myeloma status post-autologous bone marrow transplant (BMT) with a conditioning regimen of high-dose melphalan 2 weeks prior to presentation. She woke up the morning of presentation and was found to be confused for a few minutes, followed by a gradual improvement in mental status. About an hour later, she started to experience a severe headache associated with blurry vision, and shortly thereafter she became disoriented again. Paramedics identified agitation, right-side neglect, left gaze deviation and right side weakness. On arrival in the emergency department, the patient's headache had resolved, but the patient was still agitated and disoriented. The patient's altered mental statu