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Show Journal of Clinical Neuro-ophthalmology 13(1): 35-37, 1993. Transient Cortical Blindness Due to Hypertensive Encephalopathy Magnetic Resonance Imaging Correlation Thomas R. Marra, M.D., Meenaxi Shah, M.D., and Mary Ann Mikus, D. O. © 1993 Raven Press, Ltd., New York Striking reversible signal intense magnetic resonance imaging (MRl) lesions were observed in the occipital cortex of a 16-year-old girl who presented with an attack of transient cortical blindness as the initial manifestation of hypertensive encephalopathy (HTE). The lesions were seen to best advantage on T2-weighted imaging and were not visible on computed tomography (CT). It is proposed that such occipital lobe MRI lesions likely reflect extravasation of fluid and proteins across the blood brain barrier, damaged as a consequence of cerebral autoregulation failure. Key Words: Hypertensive encephalopathy-Magnetic resonance imaging-Cortical blindness. From the Department of Neurology, SinaiSamaritan Medical Center, 950 North 12th Street, Milwaukee, Wisconsin 53223, U.S.A. The authors wish to acknowledge the generous support of the SinaiSamaritan Medical Imaging Department. Address correspondence and reprint requests to Dr. Thomas R. Marra, Neurology Department, Newtowne ~edical Group, 1575 N. River Center Drive, Milwaukee, Wisconsin 53212, U.S.A. 35 Hypertensive encephalopathy (HTE) is an acute medical emergency. Failure to promptly recognize and treat this disorder may have serious consequences and lead to end organ injury of brain, heart, kidney, and eye (1). The cardinal features include severe hypertension, headache, nausea, vomiting, convulsions, visual changes, confusion, stupor, and coma (2-4). Visual signs and symptoms may be prominent and papilledema, retinal hemorrhages, and exudative lesions are commonly encountered. Transient visual obscuration progressing to frank cortical blindness with frightening rapidity may be the initial manifestation of a hypertensive crisis. It is the purpose of this brief communication to present a case of HTE whose syndrome was heralded by an attack of transient cortical blindness associated with reversible magnetic resonance imaging (MRI) focal signal intensity in the occipital visual cortex. REPORT OF A CASE A 16-year-old Native American girl with a history of chronic renal failure due to biopsy-proven mesangial proliferative glomerulonephritis developed an episode of sudden total loss of vision lasting for several minutes while walking between classes in a school corridor. This was followed by a generalized tonic-clonic seizure. Upon presentation in the emergency department, the patient was noted to be confused, agitated, and combative, but without focal visual, motor, or sensory abnormalities noted. Blood pressure ranged from 224/122 to 230/152. Her pulse was 120 and regular. Respirations were 20 per minute. She received a bolus of intravenous diazepam and phenytoin 15 mg/kg was administered. A nitroprusside drip was started and she was admitted to a monitored bed. A comprehensive bedside neurologic examination was performed the following day. At this time, the 36 R. MARRA ET At. patient was alert, oriented, cUl>pL'rativ2, dnd without visual complaint. Blood pressure was 160/110. There was normal cranial contour and the neck was supple without evidence of nuchal rigidity. The pupils were equal in size and measured 6-7 mm in diameter. They reacted briskly to light and accommodation. No afferent pupillary defect was noted. Visual acuity as measured by Snellen card was 20125-2 (00) and 20/20 (OS). Visual fields were full to confrontation testing employing red and green test stimuli. The funduscopic examination revealed 1+ diopter of papilledema in the right eye and an indistinct temporal disc margin in the left eye. Arteriolar narrowing but no retinal hemorrhage or exudate was noted. Ocular motility and saccadic eye movements were normal. The remaining cranial nerves were normal. The deep tendon reflexes were symmetrically brisk (3 +13 +) with some reduplication in both upper and lower extremities, but there was no Babinski sign. There was no focal motor, sensory, or cerebellar deficit. Gait, station, and Romberg testing were normal. Laboratory results were remarkable for a hemoglobin of 10.7 g/d!; hematocrit, 31 %; sodium, 143 mmollL; potassium, 3.5 mmollL; chloride, 103 mmollL; bicarbonate, 27 mmollL; BUN, 86 mg/dl; and creatinine, 7.7 mg/dl. The serum renin level was elevated at 28.6 ng/mllh. The urinalysis revealed microscopic hematuria and proteinuria (>300 mg/dl). Because the authenticity of the patient's seizure was initially questioned by emergency room personnel, a serum prolactin level was obtained within 1 hour of the episode and this was significantly elevated, 79.6 nglml. I ,_an performed the day of admission in the ..cquisition mode on a GE 9800 scanner was nOlo ,,31. An electroencephalogram was obtained the fOllowing day and revealed no definite focal, diffuse, or paroxysmal disturbance of cerebral function. A renal ultrasound demonstrated diffuse increase in the echogenicity of the kidneys consistent with depressed renal function. An MRI scan was obtained on the second hospital day at a time when the patient's mental status had cleared and she had no visual complaints. Spin density and T2-weighted axial images demonstrated multiple focal areas of increased cortical signal intensity with disproportionate involvement of the occipital lobes (Fig. 1). The patient's blood pressure was brought under control with an oral calcium channel blocking agent and an angiotensin-converting enzyme inhibitor. An interval MRI scan performed 9 months later showed complete resolution of the previously noted areas of increased cortical signal intensity (Fig. 2). DISCUSSION Our patient satisfies the accepted clinical criteria for the diagnosis of hypertensive encephalopathy (4) and this was likely of renal vascular origin. HTE is a medical emergency characterized by abrupt severe elevation of blood pressure. The symptoms of HTE include headache, nausea, vomiting, visual disturbance, confusion, and focal or generalized weakness. Signs include disorientation, obtundation, focal neurologic deficits, generalized or focal FIG. .1. T2-W13igh ad (SE 2000/80j magnetic resonance images obtained 24 hours after admission demonstrate mUltiple areas of Increased signal intensity with disproportionate involvement of the occipital cortex. A noncontrast computed tomographic scan obtained at the time of admission had been normal (not pictured). J Clin Neuro-ophthalmol, Vol. 13, No. I, 1993 TRANSIENT CORTICAL BLINDNESS IN HTE 37 FIG. 2. Interval MRI scan obtained 9 months later demonstrating complete resolution of the previously noted areas of increased signal intensity (SE 2.000/80). seizures, retinopathy, and papilledema. The syndrome is reversible, usually within a few hours of blood pressure reduction. HTE is considered a diagnosis of exclusion and care must be exercised to exclude stroke, subarachnoid hemorrhage, intracranial mass lesions, seizure disorder, cerebral vasculitis, and encephalitis. HTE is thought to be due to a failure of cerebral autoregulation triggered by a sudden rise in systemic blood pressure causing fibrinoid necrosis of arterioles and capillaries leading to extravasation of fluid and protein across the blood-brain barrier into the surrounding brain parenchyma (3,4). The CT scan may show reversible white matter hypodensity as an indication of this process (5). Hauser and colleagues (6) recently reported reversible MRI abnormalities characterized by focal, symmetric increased signal intensity involving both gray and white matter in three cases. They postulated that the high-intensity lesions seen on MRI reflect this process of fluid and protein extravasation. Similarly, resolution of the lesions would reflect their reabsorption. The MRI of our patient whose hypertensive crisis was ushered in by an attack of cortical blindness revealed striking focal high signal intensity lesions in the occipital lobes. These changes were seen to best advantage on T2-weighted (SE 2,000/ 80) imaging and were not associated with any significant mass effect or cortical effacement. At the time the MRI was obtained, the patient was neurologically normal and free of visual complaints, leading us to conclude that persistence of vasogenic edema rather than cerebral infarction was the likely pathologic substrate. An interval MRI scan obtained 9 months later, indeed, showed complete resolution of the high signal intensity lesions and no sign of occipital lobe infarction. Since our patient, and the three patients presented by Hauser and coworkers all showed similar MRI T2 signal intense lesions disproportionately involving the occipital regions, and each of these patients had prominent, but evanescent, visual manifestations, it is suggested that these MRI lesions may represent the pathologic substrate of the transient cortical blindness of HTE. These changes are likely due to extravasation of fluid and protein across the blood-brain barrier. Why vasogenic edema per se would cause transient cortical blindness is unclear. We speculate that it may not be the cause but rather is an epiphenomenon of occipital lobe ischemia, the result of intense cerebral vasospasm triggered by malignant systemic hypertension. REFERENCES Calhoun CA, Oparil S. Treatment of hypertensive crisis. N E/iSI ! Med 1990;323:1078-83. 2 Adams RD, Victor M. Pri/lciples af 'tellrolasy, New York: McGraw-Hill, 1981 :582. 3. Chester EM, Agamanolis Dr, Banker BQ, et a1. Hypertensive encephalopathy: a clinicopathologic study of 20 cases. Neuroiosy 1978;28:928-39. 4. Healton EB, Brust Jc. Feinfeld DA, et a1. Hypertensive encephalopathy and the neurologic manifestations of malignant hypertension. Neurology 1982;32: 127-32. 5. Fisher M, Maister B, Jacobs R Hypertensive encephalopathy: diffuse reversible white matter CT abnormalities. A/ln Neural 1985;18:268-70. 6. Hauser RA, Lacey OM. Knight MR. Hypertensive encephalopathy, magnetic resonance imaging demonstration of reversible cortical and white matter lesions. Arch Nellrol 1988;45:1078-83. I eli" NClIrO-ophtlllll"/(11, Vol. 13, No. 1. 1993 |
