Brainstem posterior reversible encephalopathy syndrome in a case with Guillain–Barré syndrome

Background Posterior reversible encephalopathy syndrome (PRES) is characterized by reversible vasogenic brain edema on magnetic resonance imaging. PRES is frequently associated with blood pressure (BP) fluctuation. Although Guillain–Barré syndrome (GBS) is often complicated by BP fluctuation, PRES is rarely reported. Here, we describe the first reported case of GBS in a patient who developed PRES mainly affecting the brainstem. Case presentation A 43‐year‐old man presented with impaired consciousness and was hospitalized after a diagnosis of infectious meningoencephalitis. His consciousness was improved by treatment; however, he presented with polyneuropathy and BP fluctuation. We diagnosed him with GBS and started intravenous immunoglobulin therapy (IVIg); however, his consciousness became impaired again after IVIg. Brain magnetic resonance imaging showed hyperintense areas of the pons, cerebellar peduncle, midbrain and basal ganglia in the apparent diffusion coefficient image and the fluid‐attenuated inversion recovery image. Diffusion‐weighted imaging showed that hyperintense and hypointense lesions were present within the same regions. We diagnosed brainstem PRES complicated with GBS. Achievement of BP control improved his consciousness and hyperintense lesions on the diffusion‐weighted imaging and apparent diffusion coefficient image map. Conclusions BP fluctuation and IVIg might have caused PRES in the present case. Neurologists should consider PRES as a differential diagnosis when consciousness is impaired in GBS, especially at the time of IVIg therapy or BP fluctuation.