In the literature, hypertensive brainstem encephalopathy is considered on the spectrum of atypical PRES. While not entirely understood, the proposed mechanism is failure of cerebral autoregulation leading to hyperperfusion and vasogenic edema. Brainstem involvement in PRES is not unusual, and has been reported in 13% of patients with PRES. 

What makes this case atypical is the isolated brainstem involvement; however, there are several case reports showing similar findings. Given the isolated brainstem findings, initial differential on the CT included brainstem glioma, osmotic demyelination, and brainstem infarct. 

Clinically, 92% of patients with PRES have acutely elevated blood pressure (mean systolic greater than 200), which was encountered in our patient. A thought is that the increased blood pressure results in failure to autoregulate intracranial pressures, which results in vasogenic edema.

Demographically, females are affected more often than males, and the peak ages are between 20 and 40. Generally, this condition resolves with blood pressure normalization.

The patient in this was case was admitted to the neuro ICU where blood pressure was slowly decreased. The patient made a full clinical recovery and discharged shortly after.