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Show Journal of C/ illiCilI Nruro- ophthalmology 9( 1): 15- 19, 1989. © 1989 Raven Press, Ltd., New York Hematoma of Optic Nerve Glioma- A Cause for Sudden Proptosis Magnetic Resonance Imaging Findings Laura J. Applegate, M. D., and Henry F. W. Pribram, M. D. Optic nerve glioma in patients with neurofibromatosis is a relatively benign neoplasm. It is slow growing and considered by some to be a hamartoma. Clinical presentation usually includes loss of vision and gradual, painless proptosis. We report a case in which abrupt proptosis of the right eye was shown on magnetic resonance imaging to be due to a hemorrhage into the tumor. Key Words: Optic nerve glioma- Hematoma. From the Department of Radiological Sciences, University of California, Irvine Medical Center, Orange California, U. S. A. Address correspondence and reprint requests to Dr. H. F. W. Pribam at Department of Radiological Sciences, University of California, Irvine Medical Center, Orange, CA 92668, U. S. A. 15 In patients with neurofibromatosis, optic nerve glioma is a relatively benign slow- growing neoplasm, considered by some to be a hamartoma. We present a case with abrupt protopsis of the right eye, Magnetic resonance imaging showed a hemorrhage into the tumor. Only three cases of hematoma within chiasmal optic nerve gliomas ( 1) and two cases within an intraoccular optic nerve glioma have been reported ( 2,3), CASE REPORT A 16- year- old white girl with neurofibromatosis and bilateral optic nerve gliomas for 10 years presented with acute proptosis of the right eye that had progressed during a I- week period. She had an occasional mild headache, but no nausea, vomiting, or fever. She was blind, small for her age with a severe thoracic kyphosis, and six cafeau- lait spots on her trunk. The right eye was grossly proptotic with inferolateral deviation. The pupils were sluggishly reactive to light. There was no evidence of corneal injection, inflammation, or discharge from the eye. The optic nerves were atrophic and the disk margins were clear. The past medical history revealed that she had a left optic nerve glioma and a craniotomy with subtotal resection of the tumor in 1982. Pathological examination revealed a pilocystic astrocytoma. She had a course of radiation therapy and in 1984 another craniotomy, biopsy, and interstitial implants of iodine- 12S seeds in the tumor bed. Several months later a computed tomography ( CT) scan showed bilateral thickened optic nerves, By October of 1985 the patient was totally blind. She was treated with chemotherapy until August 1987. The patient underwent serial magnetic resonance ( MR) 16 L. J. APPLEGATE ET AL. imaging scans that demonstrated no interval change for 18 months ( Fig. 1A and B). On the present admission, a CT scan of the head was performed that included the orbits, but thin sections were not obtained. The examination demonstrated a right optic nerve mass with a streak of increased density coursing across the mass in a linear fashion, thought to be streak artifact from the bony orbit. An MR imaging examination was performed 3 days later on a General Electric Superconductive Magnet operating at 1.5 T using a 5- in general purpose surface coil. Three- millimeter slices were obtained using Tl- weighted sagittal and coronal images and T2- weighted axial images. The left optic nerve demonstrated no change in comparison to previous MR imaging examinations. The optic chiasm appeared bulky but was poorly evaluated due to the use of a surface coil. The right globe was displaced anterolaterally by a large retrobulbar mass. On sagittal and coronal views the mass arose eccentrically from the optic nerve, as had the optic nerve glioma. The entire mass demonstrated a predominately high intensity periphery on Tl- and T2- weighted images. The center of the mass was relatively isointense on T1weighted images and hypointense on T2- weighted images when compared with normal brain. A fine black rim surrounded the mass ( Figs. 1B, 2A and B). The findings were interpreted as representing a subacute hematoma within the right optic nerve glioma. The MR signal characteristics of the hematoma indicated an age of ~ 2- 14 days. The neurosurgeons and ophthalmologists believed that decompression of the orbit was not necessary because the patient was blind. The patient was observed acutely for a few days to assure that there was no further hemorrhage and then she was sent home to be followed up in clinic. Over time her proptosis diminished and headaches disappeared. A repeat MR image of her orbits 6 months later again revealed the right optic nerve glioma. The predominantly high signal intensity within the glioma had reverted to the previous medium signal intensity comparable to brain parenchyma ( Fig. 3). Irregular ring- like low- signal- intensity areas FIG. 1. A: Axial T1 ( TE 20, TR ? OO)- weighted magnetic resonance image of the orbit 2.2 months before present admls~ lon demonstrates bilateral optic nerve enlargement, nght weater than left. The intensity of the optiC nerve glioma is similar to that of brain. B: SagIttal T1 ( TE 40, TR GOO)- weighted image of the orbit demonstrates eccentric enlargement of the right optic nerve ( arrow). Note artifact from intraventricular shunt catheter ( open arrow). 10/ 11 NCllro- pl", tlltl! mo!. Vol. 9. No. 1. 1989 MRI OF OPTIC NERVE GLIOMA HEMATOMA 17 FIG. 2. A: Axial T2 ( TE 80, TR 2,000)- weighted image of the orbits shows massive enlargement of the optic nerve glioma causing proptosis of the right globe. Characteristic intensity of a subacute hematoma is illustrated by the hypointensity center ( white arrow), the high- intensity periphery ( black arrow), and the very- low- intensity rim ( curved white arrow), which may represent hemosiderin deposition. B: T1 ( TE 20, TR 500)- weighted images. Sagittal image demonstrates relation of hematoma to portion of remaining optic nerve and tumor. within the tumor were believed to represent residual hemosiderin deposition. DISCUSSION Optic nerve gliomas are neoplasms arising from the anterior portion of the visual pathway composed of hyperplastic astrocytes, oligodendrocytes, and associated fibrillary processes. These are differentiated from gliomas elsewhere by the name optic nerve glioma ( 4). They are slowgrowing tumors. There are two characteristic patterns of tumor growth. They can grow in an expansile- intraneural pattern with proliferation of astrocytes intraaxilly, or more frequently as in neurofibromatosis, the tumor proliferates into the subarachnoid space around a ribbon of optic nerve in a circumferential perineural form ( 5). Grossly, they appear as smooth bulbous or spindle- shaped enlarged optic nerve ( 4,6- 8). The tumor enlarges by proliferation of tumor cells and florid invasion of the meninges, reactive hyperplasia of surrounding meninges termed arachnoid or collateral hyperplasia with possible formation of an arachnoid cyst, and accumulation of extracellular mucinous material produced by the tumor ( 4,6- 8). Most optic gliomas are considered benign astrocytomas, usually grades 1 or 2, although some consider them to be hamartomas ( 6). They rarely become malignant. Morbidity is usually the consequence of tumor enlargment ( 4,6- 8). Controversy exists concerning proper therapy. Surgical excision may sacrifice vision and mayor may not prolong life. Because they are slow- growing tumors, some advocate conservative therapy. Radiation may have considerable side effects ( 7). Hemorrhage in an optic nerve glioma is a rare occurrence more commonly involving the chiasm. When hemorrhage does occur within an optic nerve tumor it behaves as elsewhere in the brain parenchyma ( 9,10). On CT scan a very hyperdense lesion is noted in the region of hemorrhage that eventually fades within days to weeks. On MR images the peripheral hyperintensity seen on Tl- and T2- weighted images represents methemoglobin. The central isointensity or mild hypointensity seen on Tl- weighted images and marked hypointensity seen on T2- weighted images reflect deoxyhemoglobin in intact red blood cells. A fine, very low intensity rim around the hematoma especially noted on T2- weighted images may reflect early hemosiderin deposition. These findings are characteristic of a subacute hemorrhage in brain parenchyma ( 11). Some features of a resolving hematoma can persist for years. According to Gomori et aI., in describing hemorrhage by MR imaging, in an acute hemorrhage a clot forms within 12 h. Red blood cells accumulate centrally within the clot. Oxyhemoglobin is present acutely within the intact red blood cells and has no significant effect on relaxation time of the magnetized protons. Within the first 24 h the intact hypoxic red blood cells, now with a high J Clin Neuro- ophthalmol, Vol. 9, No. 1, 1989 18 L. J. APPLEGATE ET AL. FIG. 3. A: Axial 2- weighted ( TE 80, RT 2,500) image. Right intraorbital tumor with signal intensity comparable to gray matter. Residual low- intensity hemosiderin from the resolving hematoma ( arrow). B: Sagittal T1- weighted image ( TE 20, TR 5~ 0) de~ onstrates intratumor location of residual hemosiderin, which is also of low intensity on T1- weighted images ( arrow). concentration of deoxyhemoglobin, are responsible for the central hypointensity in acute hematomas, especially on T2- weighted images. Deoxyhemoglobin is paramagnetic and causes shortening of T2 relaxation times and thus decreased intensity ( 9). Breakdown of the clot occurs initially at the periphery within 5- 7 days. Deoxyhemoglobin is oxidized to methemoglobin, which occurs maximally at low oxygen tensions. Intracellular or extracellular methemoglobin causes a shortening of T1 relaxation, which increases the intensity on T1weighted images. Intracellular methemoglobin will cause a preferential T2 proton relaxation enhancement and thus low signal intensity. However, when the red blood cells lyse, extracellular methemoglobin causes a prolongation of T2 relaxation and thus an increase in intensity on T2weighted images. As the hematoma evolves, hemosiderin is deposited in the rim of the hematoma by 7 days to 3 weeks as macrophages engulf red blood cells and degrade hemoglobin to hemosiderin. Hemosiderin causes preferential T2 proton relaxation enhancement, and thus produces a low- intensity rim on T2- weighted images and to a lesser extent on Tlweighted images. This hemosiderin ring may persist for years. An artifact that may simulate a hemosiderin ring, in part, is chemical shift artifact. In MR imaging, according to Kelly ( 1987), a phenomenon I ( 1111 Nt'un>' 0l'htlldlmol, Vol. 9, No. 1, 1989 called chemical- shift artifact occurs in areas of the body where high water content structures and fat reside next to each other ( 12). This occurs in the orbit. This artifact is a spatial misrepresentation caused by a resonant proton frequency shift. There is a dramatic difference in resonant frequency of hydrogen protons within water molecules and those bound in lipids, due to two different magnetic environments. What is seen on the image is a misregistration of the image intensity at the interface of the two different substances. Displacement of the signal from fat is seen as an augmented signal of overlapped intensity on the opposite edge of where it should be. From where there is signal loss, due to location misregistration, is a diminution of signal. Therefore, one interface is artifactually black and the other is white ( 12). The chemical shift artifact is not believed, however, to playa role in the black ring surrounding the high- signal- intensity hematoma in our patient. No interface of increased signal intensity is present anteriorly surrounding the hematoma. It is possible that hemosiderin can begin to appear at 10 days. The hemosiderin deposition was definitely responsible for the findings on the follow- up scan at 6 months. Intraorbital hematoma is not common. The most common cause of intraorbital hematoma is trauma, either from a direct blow to the eye or from subperiosteal hemorrhage after blunt head trauma ( 13). Another cause of intraorbital hematoma can MRi OF OPTIC NERVE GLIOMA HEMATOMA 19 result from complications of ophthalmologic surgery ( 14). Spontaneous orbital hemorrhage can occur from orbital varices, orbital arterial aneurysms, severe hypertension, and a carotid cavernous fistula ( 15). Other conditions reported to be associated with intraorbital hemorrhage include hemophilia, scurvy, leukemia, and straining during labor ( 15). Extremely vascular tumors such as melanoma or lymphangioma may be prone to hemorrhage. The patient may clinically present with a painless proptosis over several months, or with the onset of acute symptoms of pain, vomiting, and proptosis with or without ecchymosis of the eyelid ( 15). Marked decrease in visual acuity may occur and in younger patients should be treated with immediate surgical drainage. Older patients, who frequently have injuries resulting from catastrophic arterial hemorrhage or occlusion, have a poor prognosis ( 15). Those who do not develop visual problems may be observed, because the hemorrhage usually resolves within months ( 15). Late sequelae from untreated orbital hemorrhage may include blindness, optic nerve atrophy, strabismus, or permanent exophthalmos from fibrosis formation ( 13). Hemorrhage, an unlikely cause of tumor enlargement, when associated with an optic nerve glioma, was well demonstrated by MR imaging. McLeod ( 1983), in reporting another intraoccular optic nerve glioma hematoma, questioned whether nonconservative therapy may have prevented the hemorrhage ( 2). In our case, the patient had received therapy in the form of radiation and chemotherapy with subtotal resection of the left optic nerve glioma. The cause of hemorrhage is uncertain. Hemorrhage into an optic nerve glioma is rare but should be considered in the differential diagnosis of acute proptosis in a patient with optic nerve glioma. Hemorrhage into the glioma of the optic nerve behaves as hemorrhage into other neural structures on MR images. MRI is very sensitive in detecting, as a well as dating, the hemorrhage. MRI should be the radiographic modality of choice to detect orbital hemorrhage and to follow its sequential course. REFERENCES 1. Maitland CG, Abiko 5, Hoyt WF, Wilson CB, Okamura T. ChiasmaI apoplexy. JNeurosurg 1982; 56: 118- 22. 2. McLeod AR. Acute blindness in childhood optic quoma caused by hematoma. J Pediatr Ophthalmol Strabismus 1983; 20: 31- 3. 3. Charles NC, Nelson L, Brookner AR, Lieberman M, Breinin GM. Pilocystic astrocytoma of the optic nerve with hemorrhage and extreme cystic degeneration. Am J Ophthalmol 1981; 92: 691- 5. 4. Henderson JW. Retinoblastoma and optic nerve glioma. In: Henderson JW, ed. Orbital Tumors. Philadelphia: WB Saunders, 1973: 508- 25. 5. Stern J, Jakobiec FA, Houspain EM. Architecture of optic nerve gliomas with and without neurofibromatosis. Arch OphthalmoI1980; 98: 505-- 11. 6. Anderson DR, Spencer WHo Ultrastructural and histochemical observations of optic nerve gliomas. Arch Ophthalmol 1970; 83: 324- 35. 7. Micholson DH, Green WR. Glioma of the anterior visual pathways. In: Micholson DH, Green WR, eds. Pediatric Ocular Tumors. New York: Masson, 1981: 281- 7. 8. Yanoff M, Davis RL, Zimmerman LE. Juvenile pilocystic astrocytoma of optic nerve. Clinicopathologic study of 63 cases. In: Jacobeic FA, ed. Ocular and Adnexal Tumors. Birmingham, Alabama: Aesculapius Publishing, 1978; 685-- 707. 9. Atlas SW, Bilaniuk LT, Zimmerman RA, Hackney DB, Goldberg HI, Grossman RI. Orbit: initial experience with surface coil- spine echo MR imaging at 1.5T. Radiology 1987; 164: 501- 9. 10. Kolodny NH, Gradgoudas ES, D'Amico DJ, Kohler SJ, Seddon JM, Murhy EJ. Proton and sodium- 23 magnetic resonance imaging of human occular tissues, a model study. Arch OpthalmoI1987; 103: 1532~. 11. Gomori JM, Grossman RI, Goldberg HI, Zimmerman RA, Bilaniuk LT. Intracranial hematomas: imaging by high field MR. Radiology 1985; 157: 87- 93. 12. Kelly WM. Image artifacts and technical limitations. In: Brant- Zawadzki M, Norman D, eds. Magnetic Resonance Imaging of the Central Nervous System. New York: Raven Press, 1987: 62- 4. 13. Seigel RS, Williams DG, Hutchison JW, Wolter R, Carlow T, Rogers D. Subpenosial hematomas of the orbit: angiographic and computed tomographic diagnosis. Radiology 1982; 143: 711- 3. 14. Iliff MT, ed. Complications of Ophthalmic Surgery. New York: Churchill Livingstone, 1983. 15. Kronel GB, Wright JE. Orbital hemorrhage. Am JOphthalmol 1979; 88: 254- 8. JGin Neuro- ophthalmol, Vol. 9, No. 1, 1989 |
