Serous Retinal Detachment in Hypertensive Posterior Reversible Encephalopathy Syndrome

SUMMARY: In accelerated hypertension, vasogenic brain edema associated with PRES may represent either autoregulatory breakthrough leading to vasodilation or excessive autoregulation leading to vasoconstriction. We describe 2 patients with PRES in accelerated hypertension who had serous retinal detachments, a vasoconstrictive phenomenon. The concurrence of serous retinal detachment and PRES offers intriguing support for the idea that vasoconstriction rather than vasodilation is the mechanism of vasogenic edema in PRES.

P RES is manifested clinically by headache, seizures, altered mental status, and retrogeniculate visual loss, with scattered foci of high T2/FLAIR signal intensity without restricted diffusion, reflecting vasogenic edema. 1 In the setting of accelerated hypertension, there are 2 competing hypotheses to explain the vasogenic edema: 1) autoregulatory breakthrough leading to the dilation of cerebral arterial vessels, hyperperfusion injury to the capillary bed, and secondary cerebral edema 2,3 ; and 2) autoregulatory excess leading to constriction of cerebral arterial vessels, ischemia of vascular endothelial cells, and vascular leakage. 4,5 The choroidopathy of hypertension is attributed to vasoconstriction of choroidal arterioles, 6 which causes RPE necrosis and overlying serous detachment of the retina. Although commonly reported in acute hypertension, choroidopathy has been described in only 1 case of hypertensive encephalopathy 7 and never in PRES.
We describe 2 patients with serous retinal detachment and PRES in the setting of accelerated hypertension. The occurrence of choroidopathy in PRES offers anecdotal support for vasoconstriction as the mechanism underlying the vasogenic edema of PRES in accelerated hypertension.

Case Reports
Case 1. A 22-year-old woman with angioimmunoblastic lymphoma, treated with cyclophosphamide, hydroxydaunorubicin, vincristine, prednisolone, and gemcitabine, developed renal failure, severe hypertension (182/96 mm Hg), generalized seizures, and depressed consciousness. Ophthalmoscopy revealed bilateral peripapillary serous retinal detachment (Fig 1). After she returned to full consciousness, a complete right homonymous hemianopia was elicitable. MR imaging demonstrated high T2/FLAIR signal intensity in the posterior parietal and occipital lobes without restricted diffu-sion (Fig 2), a finding compatible with PRES. The serous retinal detachments disappeared within weeks, but the right homonymous hemianopia persisted. Repeat brain MR imaging showed disappearance of the signal-intensity abnormality in the right occipital lobe and development of restricted diffusion in the left occipital lobe, implying conversion to infarction (not shown).

Case 2.
A 15-year-old boy presented with a seizure in the setting of severe hypertension (250/140 mm Hg) secondary to crescentic glomerulonephritis. Ophthalmoscopy showed serous retinal detachment, optic disc swelling, hard exudates, and peripapillary flameshaped hemorrhages bilaterally (Fig 3). MR imaging demonstrated occipital T2/FLAIR hyperintensities without restricted diffusion, consistent with PRES (Fig 4). After the patient returned to full consciousness, visual acuity was 20/200 in both eyes and Humphrey visual fields showed enlarged blind spots. During the next 6 weeks, visual acuity gradually recovered to 20/20 bilaterally. In view of the recovery of vision, brain MR imaging was not repeated. Six months later, visual acuity remained 20/20 in both eyes, but he had tiny scotomas, corresponding to infarcts of the RPE (not shown).

Discussion
We have described 2 patients who developed binocular serous retinal detachments in the setting of accelerated hypertension and PRES. Considering that clinical, pathologic, and experimental evidence indicates choroidal vasoconstriction as the underlying cause of serous retinal detachments, we believe that these cases fortify the concept that vasoconstriction rather than vasodilation underlies the development of PRES.
Ample evidence supports a link between systemic hypertension and vasoconstrictive choroidopathy. Histopathologic studies of postmortem specimens drawn from the acute ischemic phase of hypertension show constriction of choroidal arterioles with obliteration of their lumina. 6 Patchy filling of the choriocapillaris on fluorescein angiography has been documented in patients with hypertension 8 ; and fibrinoid necrosis of choroidal arteries and arterioles with occlusion of the choriocapillaris has been noted on histopathogic studies of human eyes with accelerated hypertension. 9 Primate models of renovascular hypertension have shown serous retinal detachment and RPE lesions associated with delayed or patchy choroidal filling. 6 The vasodilation mechanism of PRES in accelerated hypertension is supported by studies showing increased perfusion in the edematous portions of the brain in patients with hypertensive encephalopathy. 3 However, emerging evidence suggests that vasoconstriction is a better explanation for the PRES of accelerated hypertension. In patients with acute hypertension, Brubaker et al 4 found significant posterior brain hypoperfusion, reduced cerebral blood volume, reduced cerebral blood flow, and a heterogeneous pattern of mean transit time on perfusion MR imaging. Other MR perfusion studies 10,11 of PRES have revealed that relative cerebral blood volume is reduced in high-signal-intensity areas of the cerebral cortex and white matter compared with normal-signal-intensity areas.
In a retrospective study of patients with PRES by using CCA and MRA, Bartynski and Boardman 12 observed that 87% of patients showed diffuse vasoconstriction, focal vasculopathy, or vessel pruning of the PCA. Vasospasm on CCA and MRA and watershed hypoperfusion on technetium-Tc99mhexamethylpropyleneamine oxime single-photon emission tomography have also been demonstrated in women with toxemia of pregnancy, a condition with clinical features similar to PRES and hypertensive encephalopathy. 13 The development of infarction is further evidence for vasoconstriction as a common mechanism of choroidopathy and PRES in our patients. In our case 1, the visual cortex on 1 side became infarcted. In our case 2, there were residual  A, Axial FLAIR study shows high signal intensity within the parieto-occipital regions bilaterally in a distribution typical for PRES more on the left side (black arrow ) than the right side (white arrow ). B and C, Axial DWI study (B ) shows high signal intensity, but an apparent diffusion coefficient study (C ) does not show corresponding low signal intensity, findings indicative of vasogenic edema. Elschnig spots in both eyes, reflecting multifocal RPE infarctions. Infarction has been previously reported in PRES, 4 a phenomenon less likely to occur if vasodilation was the mechanism.
If serous retinal detachment and PRES share the same mechanism, why has serous detachment not been reported before in PRES? We speculate that this retinal abnormality has been overlooked because it may present asymptomatically. A, Axial FLAIR study shows high signal intensity within the occipital regions bilaterally (white arrows ) in a distribution typical for PRES. B and C, Axial DWI (B ) shows moderately high signal intensity in the occipital regions bilaterally (white arrows ), but an apparent diffusion coefficient study (C ) did not show corresponding low-signal-intensity findings indicative of vasogenic edema.