Posterior Reversible Encephalopathy Syndrome

A 34-year-old woman at 32 weeks gestation presents with severe occipital headache, blurred vision, photophobia, and one generalized convulsion. BP is 198/118 mmHg with 3+ proteinuria. Brain MRI shows bilateral parieto-occipital T2/FLAIR hyperintensities with vasogenic edema. An EEG is performed due to persistent altered mental status and cortical blindness. The pattern marked **A** in the diagram—posterior dominant slow-wave and epileptiform activity—is observed maximal over bilateral parieto-occipital regions with superimposed sharp waves and spike-and-slow-wave complexes. Which of the following best describes the clinical significance of this EEG finding in the context of her presentation?