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Show f. Clin. Neuro-ophthalmol. 5: 213-215, 1985 © 1985 Raven Press, New York Neuroradiological Clinical Pathological Correlations Bitemporal Hemianopsia and Bilateral Nasal Quadranopsia with Macular Sparing MAURICIO CASTILLO, M.D. ROBERT QUENCER, M.D. Case History A 57-year-old man presented with a 3-month history of bilateral poor vision and scotomas in the right eye. There was a history of l~ngstanding diabetes mellitus and hypertensIOn. One year prior to the present evalu.atton ~e suffered sharp pain and decreased visual field In the right eye. Computed tomography (CT) was done and interpreted as normal (Fig. 1). T~e patient was discharged on a low-dose aspmn regimen and the symptoms gradually resolved. The patient presented 6 months later. !he physical evaluation revealed an a~ert patI~nt with mild hypertension (130/90). V~sual aC~l1ty was 20130 in the left eye and 20/50 In the nght eye. There was bitemporal hemianopsia and bilateral inferior nasal quadranopsla. Corneal opacities were said to prevent fundoscopic evaluation. The pupillary reflexes and extra~cular muscle movements were intact. The remainder of the neurological and physical examinations was normal. Laboratory values were unremarkable. Pre- and post-contrast-enhanced CT scans were done (Figs. 2 and 3). Discussion The initial contrast-enhanced CT scan (Fig. 1) showed mild dilatation of the ventricular From the Department of Diagnostic Radiology, University of Miami, Jackson Memorial Medical Center, MIami, Florida. Write for r~rmts to: M. Castillo, M.D., Department of Radiology, University of Miami, School of Medicine, Jackson Memorial Hospital Medical Center, P.O. Box 016880, Miami, FL 33101, U.S.A. September 1985 system and cortical sulci compatible with generalized atrophy. When analyzed retrospectively, a small area of low attenuation poste~ior to the occipital horn of the left lateral ventncle was seen. The contrast-enhanced CT (Fig. 2) obtained 6 months later showed areas of low attenuation in both occipital lobes. The lesion in the left. occipital lobe was larger than th~t on .the nght side. This lesion extended medIally, involVing the region adjacent to the calcarine fissure but sparing the posterior cortex..A lesser. ~egree of extension was noted in the nght oCCipItal lobe; there the lesion spared part of the medial cortex and the entire posterior cortex. At a more caudad level (Fig. 3), an area of decreased density to the right and posterior to the quadrig~mina! cistern was seen. Atrophy was agam noted. The possibilities to be considered in the radiographic differential diagnosis include lo~grade neoplasms, infectious processes, white matter diseases, posttraumatIc changes, and vascular occlusive disease. Gliomas are the most common primary brain tumor. 1 One-third of them are astrocytomas. Although low-grade gliomas may ~emonstrate little or no contrast enhancement,- the bilaterality of these areas of low attenuation and the lack of mass effect are strong arguments against neoplasms. In addition, multicentric gliomas account for only 2-5% of all gliomas3 and the majority of them will show ring en~ar:tcem~nt following intravenous contrast admlr:tlstratton: Cerebritis is characterized by Clrcumscnbed areas of low attenuation, with areas of high density that represent focal hemorrhage. Edema is 213 Bitemporal Hemianopsia/Bilateral Nasal Quadranopsia Figure 1. Initial CT scan obtained at the level of the lateral ventricles. The small area of low attenuation, posterior to the occipital horn (arrow) of the left lateral ventricle, which was originally considered to represent an extension of this ventricle, in retrospect may represent the early changes of an infarct. invariably present, and irregular enhancement is characteristic. 1 Encephalomyelitis is associated with generalized brain involvement and marked neurological impairment. Herpes virus infection can produce localized changes and frequently involves the frontal or temporal lobes. Mass effect and nonhomogeneous enhancement characterize this infection. 4 Fungal infections can cause similar CT findings, but they usually occur in immunocompromised patients. Demyelinating disorders are characterized by areas of low attenuation involving the white matter. Some of these entities, such as metachromatic leukodystrophy, adrenoleukodystrophy, Krabbe's disease, Alexander's disease, and Canavan's disease, appear early in life, while others appear later. Multiple sclerosis is the most common demyelinating disorder in adults. This disease is characterized by periventricular low-density areas. During the acute phase, these areas may show contrast enhancement. Necrotizing leukoencephalopathy is related to the intrathecal administration of methotrexate. Binswanger disease is evidenced by areas of low attenuation involving the regions of the centrum semiovale. Progressive multifocal leukoencephalopathy can be detected as focal lesions at early stages, but, as its name 214 Figure 2. The second CT scan, obtained 6 months after the initial study. shows bilateral occipital areas of low attenuation (arrow·s). greater on the left side. In both occipital lobes, there is sparing of the macular regions. Figure 3. CT scan through the pons obtained at the same time as that in Fig. 2 demonstrates a low-attenuation lesion (arrow) in the right parahippocampal gyrus. This lesion involves the posterior optic pathway. Journal of Clinical Neuro-ophthalmology implies, when the diagnosis is reached, usually several areas of the brain are involved. Underlying malignancies are present in the majority of patients with this disorder. S Focal encephalomalacia can appear 3-6 months following trauma. These areas of low density are accompanied by localized partial dilatation of the adjacent ventricle or subarachnoid space. Since there was no history of trauma in our patient, this possibility is unlikely. The most common cause of cortical visual loss is infarction in the posterior cerebral artery territory. b Frequent causes of infarction include hypertension, arterial occlusive disease, and embolic phenomena. Although it was previously believed that infarcts could only be identified by CT after 48-72 h,7 state-of-the-art scanners make it possible to recognize changes within the first 24 h following the event. 8 Occlusion of the vessels that arise from the vertebrobasilar system can be readily detected by CT9 The last major branch arising from the basilar artery is the posterior cerebral artery, which supplies the corresponding occipital lobe with its medial occipitaL calcarine, and parieto-occipital branches. Depending on the branch or branches occluded, different clinical syndromes occur. Occlusion of both calcarine and parieto-occipital arteries leads to bilateral infarcts of the calcarine fissure region and complete blindness. 10 Unilateral infarction of this area produces homonymous hemianopsia of the contralateral visual fields. 10 Occlusion of different branches can lead to unusual visual hallucinations that include loss of visual association, distortion of visual outlines, prosopagnosia (inability to recognize familiar faces), teleopsia (near objects appear distant), and metamorphosia (distortion of shapes). 10 The center for macular or central vision is located in the posterior portion of the occipital cortex. When infarcts occur at this level, isolated scotomas are present clinically. When only the anterior portion of the occipital cortex is involved, central vision is preserved. J1 Macular region sparing is most commonly reported in bilateral occipital infarcts. 12 In this circumstance, central vision may represent partial recovery from total blindness. 12 Visual defects can also be secondary to infarction along the paraor peristriate fibers and the posterior optic radiations. The optic tract extends posteriorly and laterally between the uncus and the cerebral peduncle to reach the lateral geniculate body and the superior corpora quadrigemina. An infarct September 1985 Castillo, Quencer involving the posterior optic pathway, as seen in this patient (Fig. 3), can cause visual symptoms. This case meets the major radiographic criteria for the diagnosis of cerebral infarct13 : location along a known vascular territory (in this case the posterior cerebral artery), absence of radiographically recognizable edema, and absence of ring enhancement when the CT study is obtained after the acute phase. Based on these characteristics, the radiographic diagnosis of bilateral occipital infarcts with macular sparing can be made. References 1. Goldberg, H. I.: Stroke. In Cranial Computed Tomography, Lee, S. H., Rao, K. C. V. G., Eds. McGraw-Hili, New York, 1983, pp. 583-659. 2. Oi, S., and WetzeL N.: Gliomas in computerized axial tomography, correlation with tumor malignancy in 100 cases. Neurosurgery 7: 759-763, 1979. 3. Rao, K. C. V. G., Harvey, L., Itani, A., et al.: CT findings in multicentric glioblastoma: diagnosticpathologic correlation. C.T. 4: 187-192,1980. 4. Davis, J. M., et al.: CT of herpes simplex encephalitis with clinicopathological correlation. Radiology 129: 409-417, 1973. 5. Carroll, B. A., Lane, B., Norman, D., et al.: Diagnosis of progressive multi focal leukoencephalopathy by CT. Radiology 122: 137-141, 1977. 6. Mosely, I. F., and Sanders, M. D.: Visual loss. In Computerized Tomography in Nellro-ophthalmology, Mosely, I. F., Sanders, M. D., Eds. W.B. Saunders, Philadelphia. 1982, pp. 134-141. 7. Inove, Y., et al.: Sequential computed tomography scans in acute cerebral infarction. Radit1logy 135: 655-662, 1980. 8. Wall, S. D., Brant-Zowadzki, M., Jeffrey, R. B., and Barnes, B.: High frequency CT findings within 24 hours after cerebral infarction. A.f.R. 138: 307-311. 1982. 9. Vonofakos, D., Marco, H., Hacker, H.: CT diagnosis of basilar artery occlusion. A·I.N.R. 4: 525-528, 1983. 10. Hayman, L. A., Berman, S. A., Hinck, V. c.: Correlation of CT cerebral vascular territories with function: II. Posterior cerebral artery. A.f.N.R. 2: 219-225, 1981. 11. Spector, R. H., Glaser, J. S., David, N. J., Vining, D. Q.: Occipital lobe infarctions: perimetry and computed tomography. Ncurolt1gy 31: 1098-1106, 1981. 12. Benson, D. F., and Geschwind, N.: The alexias. In Hand/look of Clinical NClIn1logl/, vol. 4, Vinken, P. J., Bruyn, G. W., Eds. North Holland, Amsterdam, 1969, pp. 112-140. 13. Masdev, J.: Infarct versus neoplasm on CT: four helpful signs. A.f.N.R. 4: 522-524, 1983. 215 |
