| OCR Text |
Show Journal of NeunhOphlhalmology 15( 4): 222- 213, 1395. © 1995 Lippincott- Raven Publishers, Philadelphia Rapid Growth of an Intracranial Aneurysm Causing Apparent Retrobulbar Optic Neuritis Neil R. Miller, M. D., Peter J. Savino, M. D., and Timothy Schneider, M. D. We describe a 31- year- old man who developed sudden painful loss of vision in the right eye and was found to have a retrobulbar optic neuropathy. Magnetic resonance ( MR) imaging gave normal results, and a diagnosis of retrobulbar optic neuritis was made. The patient was treated with oral prednisone, but he continued to lose vision in the right eye and then began to lose vision in the left eye. Repeat MR imaging performed eight weeks after the initial study showed a giant intracranial aneurysm compressing the right and left optic nerves. Cerebral angiography revealed that the aneurysm arose from the origin of the right ophthalmic artery. Treatment of the aneurysm by a trapping procedure resulted in improvement in vision in the left eye but no change in vision in the right eye. This report emphasizes the difficulty in imaging intracranial aneurysms of various sizes, the rapidity with which intracranial aneurysms can enlarge, and the importance of continued follow- up examinations in patients thought to have idiopathic optic neuritis. Key Words: Optic neuritis- Aneurysm- Acute optic neuropathy- Magnetic resonance imaging. The development of acute painful unilateral loss of vision in a young adult in whom signs of an optic neuropathy are present generally suggests a diagnosis of optic neuritis. Although a similar clinical picture can be caused by mass lesions that compress the optic nerve, such lesions are rare ( 1). Nevertheless, some authors have recommended that neuroimaging studies be performed either in all patients with presumed optic neuritis or in patients with optic neuritis in whom the initial presentation or subsequent course is atypical, in order to exclude a mimicking lesion ( 2). We describe a patient who developed presumed optic neuritis in whom MR imaging initially showed no intracranial lesion but who, in fact, had a rapidly expanding intracranial aneurysm. This report emphasizes the difficulty in imaging intracranial aneurysms of various sizes, the rapidity with which intracranial aneurysms can enlarge, and the importance of continued follow- up examinations in patients thought to have idiopathic optic neuritis. CASE REPORT Manuscript received March 1, 1995. From the Neuro- Ophthalmology Unit ( N. R. M,, T. S.), the Johns Hopkins Medical Institutions, Baltimore, Maryland; and the Neuro- Ophthalmology Service ( P. J. S.), the Wills Eye Hospital, Thomas Jefferson University, Philadelphia, Pennsylvania, U. S. A. Address correspondence and reprint requests to Dr. Neil R. Miller, Maumenee B- 109, the Johns Hopkins Hospital, 600 N. Wolfe St., Baltimore, MD 21287, U. S. A. A 31- year- old man presented to the N e u r ophthalmology Service of the Wills Eye Hospital because of a two- week history of headache, blurred vision in the right eye, and pain in the base of the neck, radiating into the right eye and temple. Neuro- ophthalmologic examination at this time revealed visual acuity of counting fingers at 6 ft OD and 20/ 20 OS. Color vision testing using Hardy- Rand- Ritler ( HRR) pseudoisochromatic plates was 0/ 15 OD and 14/ 15 OS. There was a marked right relative afferent pupillary defect, and the right visual field showed a superior altitudinal defect ( Fig. 1). Ophthalmoscopy revealed normal appearing optic discs. 212 GIANT ANEURYSM MIMICKING OPTIC NEURITIS 213 i « i i 4 i. flg o a 0,4ft 4 < 0.43 Z d OJO 1 a 1.0Q Q aioC " O 0 ^ H 1 4 ~ n " V Ml' 4 IV It V, « 4 *, s:? S"--!• » "';- i-^ 1 ™ . - - * ^ ' ^ ! » « « » ," + 0.5QAGE ^ fc* **•** foe J oo apuo * r< I I I i ^^ Atfrartta FIG. 1. Results of kinetic perimetry at presentation. Visual acuity was counting fingers at 6 ft OD and 20/ 20 OS. A: There is complete loss of the visual field of the right eye. The defect includes the central 5- 10°, accounting for the decreased visual acuity. B: The visual field of the left eye is full. / Neuro- Ophthalmol, Vol. 15, No. 4, 1995 214 N. R. MILLER ET AL. The patient was thought to have optic neuritis and was enrolled in the Optic Neuritis Treatment Trial ( ONTT), a controlled clinical trial supported by the National Eye Institute of the National Institutes of Health ( 1,3). As part of the study, he underwent MR imaging of the brain and orbits. The study was of excellent quality and showed no abnormalities. Specifically, no mass was detected in the region of the intracranial portion of the right optic nerve ( Fig. 2). The patient was randomized to the oral arm of the trial, which consisted of treatment with either placebo or prednisone at a dosage of 1 mg/ kg/ day. Over the next 10 days, the patient experienced some reduction in pain but no improvement in vision. Treatment was continued for two weeks and then stopped, as mandated by the ONTT protocol ( 3). After stopping the oral medication, the patient developed worsening pain. Visual acuity in the right eye became further reduced, and vision in the left eye began to decrease. Repeat MR imaging was performed two months after the onset of visual loss and now revealed a 25 x 18 x 15- mm mass, consistent with a giant and substantially clotted aneurysm, in the suprasellar and right paracavernous regions ( Fig. 3). A cerebral angiogram confirmed that the lesion was an aneurysm, and the patient was transferred to the John Hopkins Hospital. On examination in the Neuro- Ophthalmology Unit of the Johns Hopkins Hospital, the patient had visual acuity of no light perception OD and 20/ 30 OS. He could identify only eight and one half of ten HRR plates slowly with the left eye, and visual field testing of the left eye using kinetic perimetry disclosed an incomplete temporal hemi-anopia that was denser superiorly than inferiorly ( Fig, 4). The right pupil was nonreactive to direct light but did react consensually. The left pupil was briskly reactive to light and near stimulation. There was a marked relative right afferent pupillary defect. Extraocular movements were full, and the eyes were straight by Hirschberg measurement. Corneal and facial sensation were normal and symmetric bilaterally. Ophthalmoscopy revealed pallor of the right optic disc. The rest of the right ocular fundus appeared normal. The left optic disc, macula, and vessels appeared normal. The patient underwent a repeat four- vessel cerebral angiogram that confirmed the presence of a giant, mostly clotted, aneurysm arising from the right internal carotid artery at the origin of the ophthalmic artery ( Fig. 5). Shortly thereafter, he underwent a right temporal craniotomy, at which time the aneurysm was found to have a broad neck that prevented placement of an aneurysm clip across it. Accordingly, the right internal carotid artery was ligated in the neck, and a clip was placed on the supraclinoid portion of the artery, distal to the origin of the ophthalmic artery. Postoperatively, the patient noted immediate improvement in vision in the left eye but no change in vision in the right eye. Neuro-ophthalmologic examination three days after surgery revealed no light perception in the right eye; however, visual acuity in the left eye was 20/ 25, and the patient was now able to identify all ten of the HRR plates correctly. Visual field testing of the left eye using kinetic perimetry now showed only a relative superotemporal defect ( Fig. 6). The rest of the examination was unchanged. A, B, C FIG. 2. MR imaging at time of visual loss in the right eye. A: Unenhanced proton density- weighted axial image at level of carotid bifurcation shows no evidence of mass. B: Unenhanced proton density- weighted axial image at slightly higher level aiso shows no evidence of a mass. C: Unenhanced T1- weighted sagittal image shows no evidence of a mass in the region of the intracranial portion of the right optic nerve. / Neuro- OphiMmol, Vol. 15, No. 4, 1995 GIANT ANEURYSM MIMICKING OPTIC NEURITIS 215 FIG. 3. MR imaging two months after onset of visual loss in the right eye. A: Unenhanced proton density- weighted axial image in same plane as Fig. 2A now shows a large mass consistent with a giant aneurysm in the right basal frontal region. B: Unenhanced T1- welghted sagittal image in same plane as Fig. 2C shows a heterogeneous mass with high signal intensity compared with brain, obliterating the right side of the suprasellar cistern. Note that the intracranial portion of the optic nerve cannot be seen. DISCUSSION This case is of significance for several reasons. First, it emphasizes that aneurysms that are large enough to produce loss of vision by compression of the intracranial portion of the optic nerve may nevertheless be too small to be detected by MR imaging, The patient described in this report underwent MR imaging at the time of initial loss of vision in the right eye. A retrospective review of all available films by both the original neuroradiologist and two independent neuroradiologists failed to identify the aneurysm that eventually was found to have caused the optic neuropathy. Day reviewed 80 cases of carotid- ophthalmic aneurysms and concluded that unruptured aneurysms smaller than 10 mm do not produce visual symptoms ( 4); Satoh and Kadoya studied 32 angio-graphically or surgically proven intracranial aneurysms using both computed tomographic ( CT) scanning and MR imaging and found that MR imaging detected only four of six aneurysms ( 67%) whose diameter was larger than 9 mm ( 5). In addition, neuroimaging detected only nine of 18 aneurysms ( 50%) whose diameter was 5- 9 mm and no aneurysm whose diameter was less than 4 mm. Other authors have reported similar findings ( 6). Thus, even if it is true that a carotid- ophthalmic aneurysm must be at least 10 mm in diameter before it causes visual symptoms, such an aneurysm nevertheless may not be detected by MR imaging, and if aneurysms less than 10 mm can, in fact, cause visual symptoms, there is an even greater probability that such an aneurysm would be undetected by MR imaging. Cerebral angiography remains the most sensitive method of detecting an intracranial aneurysm. A second issue raised by this case is the rapidity with which an intracranial aneurysm apparently expanded to a considerable size. It is generally believed that the formation of a giant intracranial aneurysm may take years ( 7- 9). In our case, however, there was rapid enlargement of an untreated aneurysm that initially was probably 10 mm in size or less to a size of 25 mm over eight weeks. Other authors have also documented rapid enlargement of intracranial aneurysms, some to giant size. Bull described a 51- year- old man with a four-year history of difficulty with speech and recent episodes of drowsiness and syncope, who was found to have a ' Very large" aneurysm arising near the bifurcation of the left internal carotid artery ( 10). The patient underwent ligation of the left common carotid artery; however, he developed worsening neurologic symptoms and signs over the next six months, and repeat neuroimaging studies showed what was interpreted as further enlargement of the lesion. A craniotomy was per- / Neuro- Ophthalmol, Vei 25, No. 4, 1995 216 N. R. MILLER ET AL. FIG. 4. Visual field of left eye at time of presentation to the Johns Hopkins Hospital. Kinetic perimetry shows an incomplete temporal hemianopia that Is denser superiorly than interiorly. Visual acuity in the eye is 20/ 30. The right eye is blind. formed, and the aneurysm was excised. It measured 52 x 42 x 38 mm and was filled with laminated thrombus. Fried and Yballe reported the case of a 46- year-old man who developed severe headache, nausea, vomiting, and nuchal rigidity ( 11). A large lumbar puncture demonstrated grossly bloody cerebrospinal fluid, and cerebral angiography disclosed a 13 x 15- mm aneurysm arising from the left anterior cerebral artery. The patient deteriorated rapidly and then became comatose. A repeat angiogram one week later showed enlargement of the aneurysm associated with an intracerebral hematoma. The patient underwent craniotomy, evacuation of the hematoma, and clipping of the aneurysm; however, he never recovered from surgery and died ten weeks later. Postmortem examination revealed a giant aneurysm arising at the junction of the anterior communicating and left anterior cerebral arteries. The aneurysm measured 50 x 70 x 70 mm. Finally, Weir and Drake reported the case of a 34- year- old woman in the 20th week of pregnancy who experienced sudden dizziness, diplopia, and headache ( 12). Cerebral angiography showed an 8 x 5 x 7- mm aneurysm in the region of the right superior cerebellar artery. The patient underwent craniotomy and attempted clipping of the aneurysm; however, the neck of the aneurysm could not be delineated, and the aneurysm was therefore not clipped. Postoperatively, MR imaging disclosed a 13 x 13 x 10- mm partially thrombosed aneurysm. One week later, a second craniotomy was performed, at which time the aneurysm was partially clipped. After the second operation, the patient seemed well; however, 16 weeks later, she experienced acute headache, drowsiness, confusion, and a left oculomotor nerve paresis. Repeat angiography now showed that the aneurysm had enlarged in size, and the filling portion now measured 32 x 12 x 12 mm. Balloon embolization of the aneurysm was attempted but was unsuccessful. Accordingly, a third craniotomy was performed, and the basilar artery was occluded with an aneurysm clip just below the origin of the superior cerebellar artery. A number of mechanisms seem to contribute to the growth of an unruptured intracranial aneurysm. Initially, a preexisting gap in the tunica media at the bifurcation of a cerebral artery can no longer resist the impact of the bloodstream. A sacculation is thus formed, which extends to form a small aneurysm with a thin dome and a thin neck ( 13,14). Because of turbulent blood flow in a relatively inelastic sac, endothelial damage occurs, leading to mural thrombosis. After a period of thrombogenesis, further growth follows, with organization of the thrombus and proliferation of tis- 7 Neuro- Oplithalmt, Vol. 15, No. 4, 1995 GIANT ANEURYSM MIMICKING OPTIC NEURITIS 217 FIG. 5. Right internal carotid arteriogram, lateral ( A) and oblique ( B) views, performed at time of presentation to Johns Hopkins Hospital, shows marked narrowing and stretching of the supraclinotd portion of the right internal carotid artery ( large arrowhead), consistent with a significantly clotted aneurysm arising from the right Internal carotid artery near the origin of the ophthalmic artery. Note the slight blush that represents flow within the aneurysm on the oblique view ( small arrowhead). sue in the intima caused by mechanical stimulation from the bloodstream ( 14,15). Stasis within the sac and mural thrombosis eventually cause ischemia in the wall of the aneurysm; the dome and neck of the aneurysm then thicken; and the sac enlarges ( 11). In addition, however, it has been postulated that central clotting with preservation of peripheral blood flow within an aneurysm causes persis- FIG. 6. Visual field of left eye after ligation of the right internal carotid artery in the neck and placement of a clip across the supraclinoid portion of the artery, distal to the origin of the ophthalmic artery. Kinetic perimetry reveals relative superotempo-ral defect. Visual acuity in the eye has improved to 20/ 25. The right eye is still blind. J Neuro- Ophthalmvl, Vol, 15, No. i, 1995 218 N. R. MILLER ET AL. tent hemodynamic injury to the wall, leading to scar formation and enlargement of the aneurysm ( 16). After rupture of an intracranial aneurysm, further growth may occur not only from the mechanisms described above but also from expansion of the wall of the aneurysm at the site of rupture, where there is only a thin protective layer of fibrin and other blood products, and from recurrent hemorrhage from capillaries that develop within the new wall and weaken it ( 11). Although these processes generally occur slowly over several years ( 11), the process may be rapidly progressive, with marked enlargement of the aneurysm over a few months, as evidenced by our case and those of others ( 7,10,12). A final issue raised by this case is the importance of close follow- up in any patient with a clinical diagnosis of optic neuritis, regardless of the results of neuroimaging. This patient's history and clinical findings met the criteria for him to be included in the ONTT, which had stringent requirements for entry. Despite the clinical diagnosis of optic neuritis and normal MR imaging, the patient's subsequent clinical course and neuroimaging findings ultimately showed that his loss of vision had been caused by compression of the optic nerve by an intracranial aneurysm and not by demyelination. Several authors have reported similar cases in which an intracranial aneurysm has caused an optic neuropathy with features that mimic an acute retrobulbar optic neuritis, including sudden loss of vision in one eye, retrobulbar pain, a central visual field defect, an ipsilateral relative afferent pupillary defect, and a normal- appearing optic disc ( 17- 19). Although the percentage of patients with signs and symptoms suggesting acute optic neuritis who actually have an intracranial mass lesion as the cause of their optic neuropathy is less than 0.5% ( 1), the possibility of such a lesion must nevertheless be considered in every patient, particularly if he or she presents atypically or has an atypical course, and the physician caring for such a patient must even be prepared to repeat diagnostic studies in such cases. REFERENCES 1, Optic Neuritis Study Group. The clinical profile of optic neuritis. Experience of the Optic Neuritis Treatment Trial. Arch Ophthalmol 1991; 109: 1673- 8. 2. Miller NR. Optic neuritis. In: Feldmann E, ed. Current diagnosis in neurology. St. Louis: CV Mosby, 1994: 167- 9. 3. Beck RW, Cleary PA, Anderson MM Jr, Keltner JL, Shults WT, Kaufman DI, Buckley EG, Corbett JJ, Kupersmith MJ, Miller NR, Savino PJ, Guy JR, Trobe JD, McCrary JA III, Smith CH, Chrousos GA, Thompson HS, Katz BJ, Brodsky MC, Goodwin JA, Atwell CW, the Optic Neuritis Study Group. A randomized, controlled trial of corticosteroids in the treatment of acute optic neuritis. N Engl J Med 1992; 326: 581- 8. 4. Day AL. Aneurysms of the ophthalmic segment. A clinical and anatomical analysis. / Neurosurg 1990; 72: 677- 91. 5. Satoh S, Kadoya S. Magnetic resonance imaging of subarachnoid hemorrhage. Neuroradiology 1988; 30: 361- 6. 6. Yamugami T, Higashi H, Tashiro Y, Hashimoto K, Ninami-kawa J, Akiyama Y, Hashimoto N, Kikuchi H. Magnetic resonance imaging of subarachnoid hemorrhage due to ruptured intracranial aneurysms. No To Shinkei 1990; 42: 583- 90. 7. Cuatico W, Cook AW, Tyshchenko V, Khaub R. Massive enlargement of intracranial aneurysms following carotid ligation. Arch Neurol 1967; 17: 609- 13. 8. Morley TP, Barr HWK. Giant intracranial aneurysms: diagnosis, course, and management. Clin Neurosurg 1968; 16: 73- 94. 9. Artmann H, Vonofakos D, Muller H, Grau H. Neuroradiology and neuropathology findings with growing giant intracranial aneurysm. Review of the literature. Surg Neurol 1984; 21: 391^ 01. 10. Bull JWD. Contribution of radiology to the study of intracranial aneurysms. Br Med J 1962; 2: 1702- 8. 11. Fried LC, Yballe A. Rapid formation of giant aneurysm: case report. / Neurol Neurosurg Psychiatry 1972; 35: 527- 30. 12. WeirBKA, Drake CG. Rapid growth of residual aneurysmal neck during pregnancy. Case report. / Neurosurg 1991; 75: 780- 2. 13. Ferguson GG. Physical factors in the initiation, growth, and rupture of human intracranial saccular aneurysms. / Nieii-rosurg 1972; 37: 666- 77. 14. Suzuki J, Ohara H. Clinicopathological study of cerebral aneurysms; origin, rupture, repair, and growth. / Neurosurg 1978; 48: 505- 14. 15. Thauvoy C, Vandresse JH, Stroobandt G, Brucher JM. Ac-croissement progressif et thrombose d'un anevrysme de la communicante anterieure. Etude clinique, radiologique et histologique. Neurochirurgie 1978; 24: 423- 7. 16. Jones JN, Schwartz HJ. Two cases of giant intracerebral aneurysm simulating neoplasm on CT scan; one with coexistent chronic subdural hematoma. / Neurol 1977; 215: 49- 57. 17. Ringel RA, Brick JF. Carotid- ophthalmic artery aneurysm masquerading as optic neuritis, j Neurol Neurosurg Psychiatry 1986; 49: 460. 18. Kuzniecky R, Melmed C, Schipper H. Carotid- ophthalmic aneurysm: an uncommon cause of acute monocular blindness. Can Med Assoc / 1987; 136: 727- 8. 19. Misra M, Mohanty AB, Rath S. Giant aneurysm of internal carotid artery presenting features of retrobulbar neuritis. Indian } Ophthalmol 1991; 39: 28- 9. / Neuro- Ophthalmol, Vol. 15, Wo. 4, 1995 |
