Can PRES Still Be Seen on MRI After Blood Pressure Correction and Mental Status Improvement?
Yes, MRI abnormalities in PRES can persist temporarily even after blood pressure is controlled and mental status improves, though the lesions typically resolve completely over days to weeks with appropriate treatment.
Temporal Evolution of MRI Findings in PRES
The radiological abnormalities in PRES do not disappear immediately upon clinical improvement. The characteristic T2-weighted and FLAIR hyperintensities in the posterior white matter regions follow a predictable resolution pattern:
- MRI lesions typically lag behind clinical recovery, with imaging abnormalities persisting for several days after neurological symptoms resolve 1, 2, 3
- Complete radiological resolution occurs within days to weeks after appropriate blood pressure management and removal of precipitating factors, with mean clinical recovery occurring around 5.7 days but imaging changes taking longer 2, 3
- Follow-up MRI demonstrates complete disappearance of the T2-weighted lesions in patients who achieve full clinical recovery, confirming the "reversible" nature of the syndrome 3, 4, 5
Clinical-Radiological Dissociation
There is an important temporal mismatch between clinical improvement and imaging normalization:
- Patients may show significant neurological improvement while MRI still demonstrates vasogenic edema, as the blood-brain barrier disruption and endothelial injury require time to heal even after blood pressure normalization 1, 6
- Serial MRI imaging may show initial worsening or new lesions even as mental status begins to improve, particularly within the first 24-48 hours after presentation 4
- The vasogenic edema pattern on MRI (hyperintense on T2/FLAIR, hyperintense on ADC maps) confirms the reversible nature and distinguishes PRES from cytotoxic edema seen in infarction 2, 5
Diagnostic Utility of MRI During Recovery
MRI remains the gold standard for confirming PRES diagnosis and monitoring resolution:
- MRI with T2-weighted and FLAIR sequences shows the characteristic increased signal intensity in posterior brain regions that defines PRES, and these findings persist beyond initial clinical improvement 7, 1, 8
- Diffusion-weighted imaging (DWI) with ADC mapping helps confirm vasogenic rather than cytotoxic edema, with most PRES cases showing hypo- or isointensity on DWI and hyperintensity on ADC maps 2, 5
- Follow-up MRI is recommended to document complete resolution of the lesions, which provides prognostic information and confirms the diagnosis retrospectively 3, 5
Common Pitfalls to Avoid
- Do not assume PRES is excluded if initial symptoms improve rapidly—the MRI abnormalities will still be present and diagnostic imaging should not be delayed 1, 2
- Avoid misinterpreting persistent MRI changes as treatment failure—radiological resolution naturally lags behind clinical improvement by days to weeks 3, 4
- Do not mistake atypical locations (basal ganglia, brainstem, cerebellum) for alternative diagnoses—PRES can involve these regions in addition to the classic parieto-occipital distribution 2, 5
- Ensure follow-up imaging is obtained to confirm complete resolution, as this validates the diagnosis and rules out alternative pathology that may require different management 1, 3, 5
Monitoring Recommendations
Obtain baseline MRI promptly when PRES is suspected, even if blood pressure has already been controlled and symptoms are improving, as the diagnostic findings will still be present 7, 1, 8. Perform follow-up MRI after clinical recovery (typically 1-2 weeks) to document complete resolution of the vasogenic edema, which confirms the diagnosis and ensures no permanent structural damage has occurred 3, 5.