A 62-year-old man with no relevant history presented to the emergency department with an occipital headache, and his blood pressure was 258/138. He had evidence of acute kidney injury and elevated troponin. On neurological examination, he was alert, diffusely hyperreflexic, and he had mild bilateral dysmetria and tremor. He had mild gait ataxia but could ambulate independently. MRI of the brain revealed bilateral white matter hyperintensities, characterized by vasogenic edema, involving the brainstem, cerebellum, basal ganglia and bilateral centrum semiovale, suggestive of central variant posterior reversible encephalopathy syndrome (PRES) (Figure 1). Susceptibility weighted imaging (SWI) also revealed multiple microbleeds, mostly affecting the brainstem and cerebellum. There was clear clinic radiological dissociation, with severe abnormalities on imaging but a mild brainstem–cerebellar syndrome. Blood pressure was aggressively controlled, and his symptoms resolved within a few days. Testing revealed fibromuscular dysplasia as a cause for his severe hypertension. He declined further workup or management and asked for a discharge 7 days after admission.

Figure 1.

T2 FLAIR (A, B) and T2 (C) images revealed vasogenic edema involving the brainstem, cerebellum and basal ganglia. Apparent Diffusion Coefficient (ADC) (D) revealed shine through hyperintensity, not associated with Diffusion-weighted imaging (DWI) signal change (not shown). Several microbleeds were apparent on susceptibility weighted imaging, particularly in the brainstem and cerebellum (E, F).

PRES is a Clinico-radiological syndrome characterized by acute onset of neurological symptoms associated with classic MRI findings of white matter vasogenic edema (T1, T2 hyperintense) that most frequently affects brain regions irrigated by the posterior vasculature. ^{Reference Camara-Lemarroy, Gonzalez-Moreno and Ortiz-Corona Jde1} Hypertension, uremia, systemic inflammation and chemotherapeutic drugs are common causes. Reversibility is common but not universal, and hemorrhagic lesions can be seen in SWI. ^{Reference Battal and Castillo2} The mechanisms are only partially understood, and it is thought that there is cerebrovascular dysregulation in the context of a “two-hit” phenomenon (i.e., hypertension plus inflammation). ^{Reference Camara-Lemarroy, Gonzalez-Moreno and Ortiz-Corona Jde1,Reference Battal and Castillo2} The prognosis is variable, and the mainstay of treatment is the management of the precipitant causes.

In PRES, isolated brainstem involvement or a “central variant,” affecting deep gray matter symmetrically, is rare. ^{Reference Chen, Wu and Ko3,Reference McKinney, Jagadeesan and Truwit4} Moreover, there is literature describing hypertensive brainstem encephalopathy (HBE) as a distinct entity. ^{Reference Karakis, Macdonald, Stefanidou and Kase5,Reference Thambisetty, Biousse and Newman6} However, there are several shared features between brainstem PRES and HBE, and they may simply represent a spectrum of disease. On the other hand, there may be factors that may be used to distinguish a phenotypic variant. First, microbleeds are relatively rare in HBE, while they are frequent in PRES. ^{Reference McKinney, Sarikaya, Gustafson and Truwit7,Reference Yakushiji8} Second, clinico-radiological dissociation seems to be frequently seen in hypertensive encephalopathy and rare in PRES. ^{Reference Karakis, Macdonald, Stefanidou and Kase5,Reference McKinney, Sarikaya, Gustafson and Truwit7} Finally, precipitating factors in PRES are much more varied, and usually, there is more than one factor identified, whereas HBE typically presents with isolated, but severe, elevations in blood pressure. ^{Reference Karakis, Macdonald, Stefanidou and Kase5,Reference Pascarella, Quattrone, Sabatini, Gambardella and Labate9} As a “clinico-radiological” syndrome, probably representing a spectrum of disease (which may include eclampsia and reversible vasoconstriction syndrome ^{Reference Battal and Castillo2,Reference Camara-Lemarroy, Escobedo-Zúñiga, Villarreal-Garza, García-Valadez, Góngora-Rivera and Villarreal-Velázquez10} ), these considerations may not be simply semantic, particularly since there are no specific disease-modifying therapies. More data will be needed to settle these debates.