Tamiladu & Pondicherry Chapter of Indian Radiological and Imaging Association
Promoting the study and practice of Diagnostic Radiological Imaging Modalities in the states of Tamilnadu and Pondicherry
Answer to Quiz No. 55 dated 27 March 2016
Posterior reversible encephalopathy syndrome
Findings
Diffusely symmetrical T2 FLAIR hyper intense signal is seen involving the cortical and sub cortical white matter of the bilateral parietooccipital regions, posterior temporal lobes and bilateral posterior thalamus. Mild restricted diffusion is seen. MR Angiography is normal. No haemorrhage seen.
Discussion
Reversible posterior leukoencephalopathy syndrome is a clinicoradiologic entity characterized by headaches, altered mental status, seizures, and visual loss and is associated with white matter vasogenic edema predominantly affecting the posterior occipital and parietal lobes of the brain. Most cases of PRES occur with hypertension or immunosuppression, but it can occur with many diverse clinical entities.The pathophysiology of PRES is related to disordered cerebral autoregulation. Two pathophysiologic mechanisms have been proposed regarding cerebral autoregulation—cerebral vasospasm, which results in cytotoxic edema, and vasodilatation, which results in vasogenic edema.The pathophysiology of PRES also implicates endothelial dysfunction, especially in cases without severe hypertension, such as pre-eclampsia or cytotoxic therapies. The most characteristic imaging pattern in PRES is the presence of edema involving the white matter of the posterior portions of both cerebral hemispheres, especially the parieto-occipital regions, in a relatively symmetric pattern that spares the calcarine and paramedian parts of the occipital lobes.However, other structures (such as the brain stem, cerebellum, and frontal and temporal lobes) may also be involved, and although the abnormality primarily affects the subcortical white matter, the cortex and the basal ganglia may also be involved.studies with diffusion-weighted sequences and diffusion-tensor sequences have shown increased apparent diffusion coefficients (ADCs) in the involved regions accompanied by anisotropy loss, which suggests reversible vasogenic edema as an underlying pathophysiology. Therefore, early diagnosis and treatment is essential for the patients' prognosis.
References
Hyo jeong lee MD. posterior reversible encephalopathy syndrome. Applied radiology. 2007;36(5):42-43
Findings
Diffusely symmetrical T2 FLAIR hyper intense signal is seen involving the cortical and sub cortical white matter of the bilateral parietooccipital regions, posterior temporal lobes and bilateral posterior thalamus. Mild restricted diffusion is seen. MR Angiography is normal. No haemorrhage seen.
Discussion
Reversible posterior leukoencephalopathy syndrome is a clinicoradiologic entity characterized by headaches, altered mental status, seizures, and visual loss and is associated with white matter vasogenic edema predominantly affecting the posterior occipital and parietal lobes of the brain. Most cases of PRES occur with hypertension or immunosuppression, but it can occur with many diverse clinical entities.The pathophysiology of PRES is related to disordered cerebral autoregulation. Two pathophysiologic mechanisms have been proposed regarding cerebral autoregulation—cerebral vasospasm, which results in cytotoxic edema, and vasodilatation, which results in vasogenic edema.The pathophysiology of PRES also implicates endothelial dysfunction, especially in cases without severe hypertension, such as pre-eclampsia or cytotoxic therapies. The most characteristic imaging pattern in PRES is the presence of edema involving the white matter of the posterior portions of both cerebral hemispheres, especially the parieto-occipital regions, in a relatively symmetric pattern that spares the calcarine and paramedian parts of the occipital lobes.However, other structures (such as the brain stem, cerebellum, and frontal and temporal lobes) may also be involved, and although the abnormality primarily affects the subcortical white matter, the cortex and the basal ganglia may also be involved.studies with diffusion-weighted sequences and diffusion-tensor sequences have shown increased apparent diffusion coefficients (ADCs) in the involved regions accompanied by anisotropy loss, which suggests reversible vasogenic edema as an underlying pathophysiology. Therefore, early diagnosis and treatment is essential for the patients' prognosis.
References
Hyo jeong lee MD. posterior reversible encephalopathy syndrome. Applied radiology. 2007;36(5):42-43
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