Journal of Neuro-Ophthalmology, December 2014, Volume 34, Issue 4

Lateral Geniculate Lesions Causing Reversible Blindness in a Pre-eclamptic Patient With a Variant of Posterior Reversible Encephalopathy Syndrome

Lateral Geniculate Lesions Causing Reversible Blindness in a Pre-eclamptic Patient With a Variant of Posterior Reversible Encephalopathy Syndrome Maxwell S. Stem, MD, Abigail Fahim, MD, PhD, Jonathan D. Trobe, MD, Hemant A. Parmar, MD, Mohannad Ibrahim, MD Abstract: Bilateral lateral geniculate nucleus (LGN) injury is a rare cause of vision loss. We describe a patient with pre-eclampsia who developed profound but reversible bilateral vision loss, bilateral serous retinal detachments, and magnetic resonance imaging signs of a variant of posterior reversible encephalopathy syndrome (PRES) that affected both LGNs and spared the retrogeniculate path-ways. We provide evidence that the visual loss was not from the chorioretinal lesions but from the LGN lesions. The concurrence of PRES and lesions attributed to choroidal hypoperfusion provides support for the notion that vasoconstriction also underlies the pathogenesis of PRES. Journal of Neuro-Ophthalmology 2014;34:372-376 doi: 10.1097/WNO.0000000000000120 © 2014 by North American Neuro-Ophthalmology Society Systemic hypertension and proteinuria during pregnancy define pre-eclampsia. This disorder may impair vision by inducing vasoconstriction in pre-choriocapillaris arterio-les, leading to choroidal ischemia, breakdown of the blood- retinal barrier, and extravasation of fluid into the subretinal space (1,2). Pre-eclampsia also may affect vision by causing posterior reversible encephalopathy syndrome (PRES) (3), which normally produces vasogenic edema in the parieto- occipital lobes visible as high signal on T2 and fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) sequences (4). Finally, vision loss in pre-eclampsia may result from cerebral infarction, presumably due to excessive vasoconstriction (5). Bilateral lateral geniculate nucleus (LGN) injury is an extremely rare cause of diminished vision under any circumstances (6), and there has only been 1 report of a patient with pre-eclampsia (7). The mechanism of injury in that case was believed to be infarction from microangi-opathy. PRES has often been implicated as a cause of vision loss in patients with pre-eclampsia (3), but those cases have always contained imaging abnormalities in the occipital lobes. We present a unique patient with pre-eclampsia who developed reversible visual failure and MRI abnormal-ities suggestive of PRES in the region of the LGN bilaterally but not in any other part of the retrogeniculate visual pathways. CASE REPORT A 31-year-old primigravida with history of migraine with typical visual aura presented to her local hospital for rupture of amniotic membranes at 38 weeks gestation. For several days, she had noted impairment of vision in both eyes and headache, which she ascribed to migraine. Blood pressure on admission was as high as 174/117 mm Hg. She had proteinuria of 6,489 mg per 24 hours (normal: less than 10 mg per 24 hours), elevated aspartate aminotransferase of 100 IU/L (normal: 5-40 IU/L), thrombocytopenia of 90,000/mL (normal:150,000-400,000/mL), but normal electrolytes. Diagnosed with pre-eclampsia and hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome, the patient was treated with intravenous antihypertensive med-ication, including magnesium sulfate, and multiple platelet transfusions. She had a cesarean section with delivery of a healthy baby. Despite postpartum normalization of blood pressure, liver enzymes, and platelet count, the patient continued to Kellogg Eye, Department of Ophthalmology and Visual Sciences (MSS, AF, JDT), Department of Neurology (JDT), Department of Radiology (Neuroradiology) (HAP, MI), University of Michigan Medical School, Ann Arbor, Michigan. The authors report no conflicts of interest. Address correspondence to Jonathan D. Trobe, MD, W. K. Kellogg Eye Center, 1000 Wall Street, Ann Arbor, MI 48105; E-mail: jdtrobe@ med.umich.edu 372 Stem et al: J Neuro-Ophthalmol 2014; 34: 372-376 Clinical Observation Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. report poor vision. Visual acuity was count fingers in both eyes with normal fundus examination. One day later, brain MRI revealed bilateral and slightly asymmetric T2 and FLAIR hyperintensities in the basal ganglia, thalami, lateral geniculate nuclei, midbrain, pons, and deep cerebral white matter without restricted diffusion or contrast enhance-ment. Gradient echo imaging was negative for blood products. The retrogeniculate visual pathways appeared normal (Fig. 1). MRI was interpreted as consistent with the "central variant" of PRES sparing the posterior cerebral hemispheres. On arrival at our institution, blood pressure, platelets, and liver enzymes were normal. Visual acuity remained at count fingers in both eyes with intact pupillary reactions. Ophthalmoscopy disclosed subretinal fluid in the maculas, peripheral bullous retinal detachments, several intraretinal hemorrhages, and multiple subretinal white areas with indistinct margins. Over the next 2 days, the patient maintained normal blood pressure and electrolytes. The visual acuity improved to 20/25 in both eyes. Dilated fundus examination revealed reduced subretinal fluid in the retina with faint subretinal white areas (Fig. 2A, B). Optical coherence tomography confirmed the presence of subretinal fluid in both eyes (Fig. 2C, D). Four days after initial brain MRI, a repeat study showed dramatic lessening of the T2/FLAIR hyperintensities (Fig. 3). Two weeks later, the visual acuity was 20/20 bilaterally with complete resolution of the serous retinal detachments. FIG. 1. Axial fluid-attenuated inversion recovery magnetic resonance imaging demonstrates hyperintensities in the pons (A), left midbrain (B), basal ganglia and thalami, including regions of the lateral geniculate nuclei (arrows) (C), and in deep cerebral white matter (D). There was no restricted diffusion or abnormal enhancement in these involved areas (not shown). Stem et al: J Neuro-Ophthalmol 2014; 34: 372-376 373 Clinical Observation Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Automated visual fields showed mean deviations of 27.96 dB in the right eye and 210.24 dB in the left eye with scattered high threshold points not in a localizing distribu-tion. Five weeks later, visual fields showed mean deviations of 23.96 dB in the right eye, 24.55 dB in the left eye, and there were still faint white dots beneath the retina in both eyes. DISCUSSION We are unaware of previous reports of PRES causing bilateral LGN lesions with severe vision loss. There is compelling evidence that involvement of the LGNs was the cause of vision impairment in our patient. The retinal abnormalities were not observed when visual acuity of counting fingers was documented. The patient's vision improved to 20/25 even as the retinal abnormalities re-mained. The symmetric vision loss and normal pupillary reactions militate against optic nerve or chiasmal involve-ment. There were no MRI signal changes in the retrogeni-culate visual pathways, but there were signal abnormalities consistent with vasogenic edema in the region of both LGNs. Several reports have documented varied manifestations of PRES, including cases with signal abnormalities confined to the brainstem, spinal cord, and diencephalon (8-10). This "central variant" of PRES has previously been called "hypertensive brainstem encephalopathy" (8), "reversible pontine edema" (9) and "reversible brainstem hypertensive encephalopathy" (10). It is found in approximately 4% of patients with PRES and typically involves the thalami, pos-terior limbs of internal capsule, cerebellum, brainstem, and periventricular white matter (11). Predisposing conditions for this variant include systemic hypertension, pre-eclampsia/ eclampsia, and cyclosporine therapy (11). Awareness of this variant of PRES is important to avoid diagnosing conditions with similar imaging features, including acute disseminated encephalomyelitis, extra-pontine myelinolysis, and viral encephalitis. This case adds to a short roster of reports in which manifestations of breakdown of the retinal pigment epithe-lial barrier and blood-brain barrier have occurred together (12). It may offer insight into the pathogenesis of PRES. The ophthalmoscopic manifestations of pre-eclampsia and other acute hypertensive states have been linked to hypo-perfusion in choroidal vessels (1,2), but there is debate as to whether the vasogenic edema of PRES results from vasodi-latation or vasoconstriction. One theory posits that loss of cerebral autoregulation, whereby arterioles constrict in response to the rising systemic blood pressure to maintain a steady flow of blood to the brain, fails in patients with acute hypertension, including pre-eclampsia. This failure of autoregulation is said to lead to vasodilation with subse-quent breakdown of the blood-brain barrier and extravasa-tion of fluid into brain parenchyma (13). An alternate theory is that arteriolar vasoconstriction and resultant ische-mia account for the disruption of the blood-brain barrier. Support for this alternate theory comes from neuroimaging studies of patients with PRES that demonstrate decreased cerebral blood flow in the affected areas of the brain (14). Finally, some investigators believe that placental hypoperfu-sion in pre-eclampsia leads to the upregulation of cytokines that promote endothelial dysfunction, which could result in vasogenic cerebral edema and PRES (15). FIG. 2. Fundus abnormalities 5 days after symptom onset. Submacular fluid and deep white retinal lesions are visible in the right (A) and left (B) eyes. Subretinal fluid is confirmed on optical coherence tomography (C, right eye; D, left eye). 374 Stem et al: J Neuro-Ophthalmol 2014; 34: 372-376 Clinical Observation Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. In our patient, the finding of retinal abnormalities known to be caused by choroidal hypoperfusion supports the notion that vasoconstriction within the brain paren-chyma is the pathophysiologic basis of PRES (12). 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