Central-variant posterior reversible encephalopathy syndrome mimicking tumor progression in a glioblastoma patient on bevacizumab: illustrative case.

backgroundBevacizumab (BEV) has been associated with posterior reversible encephalopathy syndrome (PRES). Central-variant PRES (cvPRES), involving the thalami and periventricular regions, can mimic glioblastoma (GBM) recurrence. Few reports have described this pattern assessed by serial quantitative apparent diffusion coefficient (ADC) measurement with BEV continuation. OBSERVATIONS: A 36-year-old woman with IDH-mutant GBM of the left frontal lobe, treated with resection, radiotherapy, temozolomide, and subsequently BEV at recurrence, presented 6 weeks after her ninth BEV cycle with impaired consciousness and gait disturbance. Family blood pressure (BP) records revealed systolic variability of 90-200 mm Hg with temporal correlation between systolic peaks and neurological worsening. MRI showed periventricular fluid-attenuated inversion recovery hyperintensity extending into the bilateral medial thalami, faint patchy enhancement, and elevated ADC. Symptoms improved within days of antihypertensive optimization; at 5 months, imaging nearly resolved and quantitative ADC measurement showed near-complete normalization (normalized ADC [nADC] 1.42 → 1.00). BEV was continued under strict BP management. LESSONS: In GBM patients on BEV, a lesion with 1) central/periventricular/thalamic distribution, 2) absent nodular/ring enhancement, 3) elevated ADC, 4) temporal correlation between BP fluctuation and symptoms, and 5) prompt reversibility with antihypertensive optimization should suggest cvPRES over recurrence. ADC normalization supports reversibility, and BEV continuation under strict BP control is reasonable in recurrent GBM. https://thejns.org/doi/10.3171/CASE26614.