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Progressive Visual Field Defects in Patients With Intracranial Arteriovenous Malformations
Progressive Visual Field Defects in Patients With Intracranial Arteriovenous Malformations Satoshi Kashii, M.D., Sherry K. Solomon, M.D., Franklin G. Moser, M.D., Jean Tostanowski, M.D., and Ronald M. Burde, M.D.
Two men, aged 59 and 36 years, had large, intracranial arteriovenous malformations. Both patients developed severe, bilateral visual loss secondary to unrecognized chronic papilledema. Lumbar puncture disclosed increased intracranial pressure. Neuroimaging disclosed only vascular malformations. The patients were treated by embolization of the vascular malformations and ventriculoperitoneal shunting procedures. The malformation of one patient was excised.
T HE LACK of consistent correlation between the clinical features and the size, location, and vascular patterns of intracranial arteriovenous malformations is well known.' This lack of correlation has been related to the congenital nature of the malformation and to the mechanisms by which symptoms may be produced, such as hemorrhage or mass effect."! Visual field loss in arteriovenous malformations is a well-known sequela of increased intracranial pressure secondary to hemorrhage, hematoma, or obstructive hydrocephalus.l-' We treated two patients who had severe visual field loss secondary to chronic papilledema attributable to increased intracranial pressure.
Accepted for publication Feb. 27, 1990. From the Departments of Ophthalmology (Drs. Kashii, Solomon, Tostanowski, and Burde), Radiology (Dr. Moser), and Neurological Surgery (Drs. Moser and Burde), Albert Einstein College of Medicine, Bronx, New York. This study was supported in part by an unrestricted grant to the Department of Ophthalmology, Albert Einstein College of Medicine, from Research to Prevent Blindness, Inc., New York, New York. Reprint requests to Ronald M. Burde, M.D., Department of Ophthalmology, Albert Einstein College of Medicine, Montefiore Medical Center, 111 E. 210th St., Bronx, NY 10467.
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Case Reports Case 1 A 59-year-old right-handed man complained of severe visual loss in March 1988. In January 1976, he had a syncopal episode associated with nausea, vomiting, and general malaise. A brain scan performed at that time reportedly showed increased uptake in the right posterior temporal lobe area. Cerebral angiography showed a dural and tentorial arteriovenous malformation with deep extension. Results of neurologic evaluation were normal. The optic disks were normal. No definitive treatment was recommended. The patient was lost to follow-up until May 1980, at which time the patient had a generalized tonic-clonic seizure associated with a oneto two-minute episode of loss of consciousness. A diagnosis of temporal lobe seizures secondary to the arteriovenous malformation was made. The presence and size of the arteriovenous malformation were confirmed again by cerebral angiography. The patient was treated with phenytoin (400 mgj'day) to control the seizure activity. The patient did not seek further medical attention until August 1985 when he complained of difficulty seeing. Neurologic evaluation disclosed blurring of the nasal margins of the optic disk in the right eye and elevation of the disk margin 360 degrees in the left eye. The results of the remainder of the neurologic evaluation were noncontributory. A computed tomographic scan performed in March 1986 disclosed a large arteriovenous malformation that involved much of the right temporal, parietal, and occipitallobes. The patient was first examined by an ophthalmologist in February 1989 for decreased vision in his right eye of several months' duration. Pertinent findings on examination included a
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visual acuity of R.E.: counting fingers at two feet and L.E.: 20/50. Both pupils reacted to light, although the reaction of the right pupil was sluggish. A relative afferent pupillary defect was present on the right side. Ophthalmoscopic examination of the right eye disclosed optic atrophy with blurring of the disk margin nasally, sheathing of vessels at the 5:00 o'clock meridian with arteriolar narrowing, and absence of spontaneous venous pulsations. The margins of the left disk were blurred for 360 degrees, and a small refractile body was present at the disk border at the 6:00 o'clock meridian. There were no spontaneous venous pulsations. Kinetic visual fields performed with a Goldmann perimeter disclosed a temporal island in the right eye only and large superior and temporal defects in the left eye (Fig. 1). The patient was admitted to our institution for further examination and treatment. A fourvessel angiogram confirmed the presence of a large arteriovenous malformation along the edge of the tentorium predominantly on the right side (Fig. 2). The main arterial supply came from branches of the external carotid artery, including the middle meningeal artery, the internal maxillary artery, and the suboccipital artery. Some branches from the vertebral
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artery and middle cerebral artery also supplied blood to the malformation. Venous drainage occurred through the straight sinus and the sigmoid sinus by means of multiple collateral vessels. Embolization of the malformation was performed by using both the right external carotid and the right middle meningeal arteries. On the basis of the presence of chronic disk edema with significant visual field loss, the neuro-ophthalmological service requested that the patient undergo a lumbar puncture. The neurosurgical service was uncertain about the indications for this procedure, but acquiesced, and a lumbar puncture was performed. The opening pressure was 480 mm H 20 . A ventriculoperitoneal shunting procedure was then performed to decompress the patient's optic nerves. The patient's visual function test results remained unchanged after surgery, but ophthalmoscopic examination showed decreased papilledema in his left eye and spontaneous venous pulsations. The patient was seen again in May 1988, at which time there was minimal further loss of temporal field in the right eye and constriction of the inferior nasal field in the left eye. Repeat lumbar puncture was recommended but refused.
Fig. 1 (Kashii and associates). Patient 1. Kinetic visual fields performed on a Goldmann perimeter show the superior temporal field defect in the left eye associated with a significant visual field defect in the right eye, which fits the definition of "junctional scotoma."
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Fig. 2 (Kashii and associates). Patient 1. Left, Selective angiogram shows dural arteriovenous malformation developing from right meningeal artery. Right, Left vertebral angiogram shows emissary artery feeding dural arteriovenous malformation from muscular branches of left vertebral artery.
Case 2 A 36-year-old right-handed man with a known intracranial arteriovenous malformation that was diagnosed in 1981 was examined in March 1988 for a progressive visual field loss in both eyes. In 1981, the patient began to have generalized tonic-clonic seizures. At that time, examination included an electroencephalogram, a computed tomographic scan, and an angiogram, which showed the presence of a large, right parietal arteriovenous malformation. The patient first noted a problem with his vision in 1985, at which time he complained of decreased vision in his left eye. The only afferent visual system finding was bilateral papilledema. No visual field testing was performed. A computed tomographic scan again confirmed the presence of a right parietotemporal arteriovenous malformation with large feeding channels, and it was presumed that the chronic disk edema was caused by a mass effect. The patient was lost to follow-up until February 1986, at which time neuro-ophthalmologic examination disclosed a visual acuity of R.E.: 20/30 and L.E.: hand motions. Ophthalmoscopic examination showed evidence of severe optic atrophy without disk elevation. The patient was lost to follow-up again until March 1988, at which time he returned because of severe visual difficulties. Complete ophthalmic
examination at that time disclosed a visual acuity of R.E.: 20/25 and L.E.: light perception superonasally. The pupils were 4 mm and 5 mm on the right and left, respectively, and reacted sluggishly to direct light stimulation at 3 mm and 4 mm, respectively. There was a markedly positive relative afferent pupillary defect on the left side. On ophthalmoscopic examination, the optic disks were pale and flat with sharp margins. There was no evidence of edema, hemorrhage, or infarction. Kinetic visual fields done both on a tangent screen at 1, 2, and 3 m and on a Goldmann perimeter disclosed a small, centrally skewed island of vision (Fig. 3). On the basis of optic atrophy and history of papilledema, lumbar puncture was recommended. The neurosurgical service acquiesced again, and the opening pressure was 310 mm H20 . A computed tomographic scan did not differ significantly from the one done in 1985. A cerebral angiogram showed slow filling of a large, right frontoparietal arteriovenous malformation through feeders mainly from the right middle cerebral artery and, to a lesser degree, from the right posterior cerebral artery and the right anterior cerebral artery. The malformation was drained by two large, superficial, cortical veins that emptied into the superior sagittal sinus. A ventriculoperitoneal shunt procedure was performed (Fig. 4). Embolization therapy was
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Fig. 3 (Kashii and associates). Patient 2. Kinetic visual field performed on a Goldmann perimeter shows a small, S-degree central island slightly skewed temporally. The visual acuity of the left eye is light perception. subsequently initiated, followed by a craniotomy with partial removal of the arteriovenous malformation. The visual field remained unchanged. In June 1986/ the patient underwent removal of the residual tumor.
Immediately after surgery, the patient complained of loss of vision in his right eye. A computed tomographic scan showed a large, hypodense, extra-axial collection under the right craniotomy flap with ventricular efface-
Fig. 4 (Kashii and associates). Patient 2. Left, A frontal view and right, a lateral view of the right internal carotid arteriogram show the large arteriovenous malformation located mainly in the parietal region. The malformation is fed from the right middle cerebral artery. The ventriculoperitoneal shunt cannula can be seen in the right lateral ventricle.
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ment and compression. After drainage by means of a twist drill, the patien t' s vision returned to its preoperative state.
Discussion Both of our patients lost visual function because of the unrecognized consequences of chronic papilledema secondary to raised intracranial pressure. Evidence of chronic papilledema was present in Patient 1, whereas Patient 2 had advanced optic atrophy with a history of papilledema and a lumbar puncture that confirmed the presence of increased intracranial pressure. Papilledema and raised intracranial pressure are unusual signs of a cerebral arteriovenous malformation in the absence of severe secondary intracranial hemorrhage or hematoma, unless the arteriovenous malformation is huge. In 110 patients with cerebral arteriovenous malformation, Paterson and Mckissock" found only one patient who had papilledema without a specific cause. Intracranial arteriovenous malformations have been classified angiographically on the basis of their arterial supply as purely dural, mixed dural and pial, and purely pial.' Pure dural malformations are limited to the dura and receive only meningeal arterial blood. Mixed dural and pial malformations receive their blood supply not only from meningeal vessels but also from cerebral or cerebellar arteries. Purely pial malformations are intracranial lesions that are supplied only by cerebral or cerebellar arteries, without meningeal contribution. Dural arteriovenous malformations are generally rare. They comprise 6% to 12% of intracranial arteriovenous malformations-" and occur predominantly in women over 40 years of age." Dural malformations in the posterior fossa are far more common than are those above the tentorium. Of the supratentorial arteriovenous malformations in one study, only 6% were dural, but of the infratentorial malformations, 35% were dural.' The malformation of Patient 1 is classified as mixed dural-pial because of its arterial supply. It is, however, more predominantly of the dural type, because most of its blood supply is derived from dural vessels. As early as 1968, dural arteriovenous malformations that developed in the posterior fossa were regarded as a distinct entity because of their frequent association with pseudo tumor-
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like symptoms.v" In two studies, 14% to 24% of patients with dural malformations involving the transverse sinus were reported to have papilledema.P:" but the authors included patients in whom hydrocephalus or subarachnoid hemorrhage also existed. Recently, Houser and assocrates" reported that five of 14 of their patients with dural arteriovenous malformations that affected the transverse sinus had increased intracranial pressure and no history of subarachnoid hemorrhage or hydrocephalus. The investigators postulated that dural sinus occlusion precedes the development of dural arteriovenous malformations in the transverse sinus. Most posterior fossa dural malformations develop within or in direct proximity to a major venous sinus. These malformations raise the venous pressure by direct shunting of arterial blood,":" and this is believed to be the primary cause of papilledema in dural arteriovenous malformations in the posterior fossa .14-16 Pial arteriovenous malformations are the most common intracranial arteriovenous malformations (72%).5 They affect men slightly more often than they affect women. 17,18 They are associated with the triad of hemorrhage, seizures, and recurrent headaches." Chronic increased intracranial pressure without a history of either intracranial hemorrhage or hydrocephalus, however, is rare in pial malformations. 2 ,20-23 The difference in inducing raised intracranial pressure between dural and pial malformations appears to be attributable to the direct drainage of the enlarged dural arteries into involved sinuses. This produces a rise in venous pressure in dural malformations, whereas pial malformations rarely shunt directly into the dural sinuses": rather they increase venous pressure because of the massive runoff from large shunting vessels, which produces increased cerebral blood volume and decreased cerebrospinal fluid absorption. 14,2o,22,23,25,26 Both of our patients had pial malformations functionally. The malformation of Patient 1 could, on the basis of the origin of its blood supply, be classified as a dural malformation, but it did not directly shunt blood into the venous sinuses. Thus, the finding of increased intracranial pressure suggests that the malformation is acting as though it were pial. Increased intracranial pressure has been long known to cause bilateral papilledema. Only rarely has it been recognized that asymmetric papilledema may occasionally be seen in patients with pseudotumor cerebri, especially at initial examination.F:" Based on the presence of
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a relative afferent pupillary defect, one study of a large series of patients with pseudotumor cerebri estimated that asymmetric visual field defects were seen in 16 of 59 (28%) patients.F In our Patient 1, the left eye had a superotemporal field defect that respected the vertical meridian, whereas only a temporal island of vision remained in the right eye. Although the loss of the left homonymous field in both eyes is explained on the basis of the location and size of the arteriovenous malformation, the remainder of loss of visual function is most likely attributable to field loss associated with the optic atrophy of chronic disk edema. Decreased vision in one eye with a superotemporal field defect in the fellow eye suggests a junctional scotoma. There is no visible mass effect, however, in the region of the right prechiasmal optic nerve as reaffirmed by multiple neuroradiologic examinations, including mag-
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netic resonance imaging (Fig. 5). It is possible that the asymmetry seen may be attributable to a steal phenomenon from the ophthalmic artery to the arteriovenous malformation. In Patient 2, the observation of bilateral papilledema early in the course of the process, which is documented in his old record, leads us to postulate that there must have been intermittent increases in intracranial pressure that eventually produced almost total loss ofaxons. This loss ofaxons precluded the development of disk elevation even with a substantiated increase in intracranial pressure at the time of our observation. The clinician should be aware of this infrequent cause of papilledema. Intracranial arteriovenous malformations, whether dural or pial in type, can produce an asymptomatic chronic increase of intracranial pressure. Treatment should be aimed primarily at the underlying arteriovenous malformation. The associated development of chronic papilledema can produce progressive visual loss; patients with papilledema, like those with pseudotumor cerebri, must have sequential visual field testing on a regular basis. If progressive loss of visual field is documented over one to four weeks, a shunting procedure or an optic nerve sheath fenestration should be performed.
References 1. Troost, B. T., and Newton, T. H.: Occipital lobe arteriovenous malformations. Arch. Ophthalmol.
93:250, 1975.
Fig. 5 (Kashii and associates). Patient 1. Magnetic resonance image, T2-weighted, shows a large, brighter (hyperdense) area that corresponds to the parietotemporal arteriovenous malformation. There is no visible mass in the right prechiasmal region. (Left is the patient's right, and right is the patient's left.)
2. Paterson, J. H., and McKissock, W.: A clinical survey of intracranial angiomas with special reference to their mode of progression and surgical treatment. A report of 110 cases. Brain 79:233, 1956. 3. Sibony, P. A., Lessel, 5., and Wray, 5.: Chiasmal syndrome caused by arteriovenous malformations. Arch. Ophthalmol. 100:438, 1982. 4. Enoksson, P., and Bynke,H.: Visual fielddefects in arteriovenous aneurysms of the brain. Acta Ophthalmol. 36:586, 1958. 5. Newton, T. H., and Cronqvist, 5.: Involvement of dural arteries in intracranial arteriovenous malformations. Radiology 93:1071,1969. 6. Fults, D., and KelIy, D. L., [r.: Natural history of arteriovenous malformations of the brain. A clinical study. Neurosurgery 15:658, 1984. 7. Houser, O. W., Baker, H. L., Jr., Rhoton, A. L., [r., and Okazaki, H.: Intracranial dural arteriovenous malformations. Radiology 105:55, 1972. 8. Newton, T. H., Weidner, W., and Greitz, T.: Dural arteriovenous malformation in the posterior fossa. Radiology 90:27, 1968.
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9. Nicola, G. c.. and Nizzoli, V.: Dural arteriovenous malformations of the posterior fossa. J. Neurol. Neurosurg. Psychiatry 31:514, 1968. 10. Kuhner, A., Krastel, A., and Stoll, W.: Arteriovenous malformations of the transverse dural sinus. J. Neurosurg. 45:12,1976. 11. Obrador, S., Soto, M., and Silvela, J.: Clinical syndromes of arteriovenous malformations of the transverse-sigmoid sinus. J. Neurol. Neurosurg. Psychiatry 38:436, 1975. 12. Houser, O. W., Campbell, J. K., Campbell, R. J., and Sundt, T. M., Ir.: Arteriovenous malformation affecting the transverse dural venous sinus. An acquired lesion. Mayo Clin. Proc. 54:651, 1979. 13. Malik, G. M., Pearce, J. E., Ausman, J. I., and Mehta, B.: Dural arteriovenous malformations and intracranial hemorrhage. Neurosurgery 15:332, 1984. 14. Lamas, E., Lobato, R. D., Esparza, J., and Escudero, L.: Dural posterior fossa AVM producing raised sagittal sinus pressure. J. Neurosurg. 46:804, 1977. 15. Lasjaunias, P., Chiu, M., Brugge, K. T., Tolia, A., Hurth, M., and Bernstein, M.: Neurological manifestations of intracranial dural arteriovenous malformations. J. Neurosurg. 64:724, 1986. 16. Vinuela, F., Fox, A. J., Pelz, D. M., and Drake, c.G.: Unusual clinical manifestations of dural arteriovenous malformations. J. Neurosurg. 64:554, 1986. 17. Guidetti, B., and Delitala, A.: Intracranial arteriovenous malformations. Conservative and surgical treatment. J. Neurosurg. 53:149, 1980. 18. Houser, O. W., Baker, H. L., Svien, H. J., and Okazaki, H.: Arteriovenous malformations of the parenchyma of the brain. Radiology 109:83, 1973. 19. Stein, B. M., and Wolpert, S. M.: Arteriovenous malformations of the brain. Arch. Neurol. 37:1, 1980. 20. Barrow, D. L.: Unruptured cerebral arteriove-
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nous malformations presenting with intracranial hypertension. Neurosurgery 23:484, 1988. 21. Schiffer, J., Bibi, c., and Avidan, D.: Cerebral arteriovenous malformation. Papilledema as a presenting sign. Surg. Neurol. 22:524, 1984. 22. Vassilouthis, J.: Cerebral arteriovenous malformation with intracranial hypertension. Surg. Neurol. 11:402, 1979. 23. Weisberg, L. A., Pierce, J. F., and [abbari, B.: Intracranial hypertension resulting from a cerebrovascular malformation. South. Med. J. 70:624, 1977. 24. Brown, R. D., Jr., Wiebers, D.O., Forbes, G., O'Fallon, W. M., Piepgras, D. G., Marsh, W. R., and Maciunas, R. J.: The natural history of unruptured intracranial arteriovenous malformations. J. Neurosurg. 68:352, 1988. 25. Gelwan, M. J., Choi, I. S., Berenstein, A., PileSpellman, J. M. D., and Kupersmith, M. J.: Dural arteriovenous malformations and papilledema. Neurosurgery 22:1079,1988. 26. Van den Bergh, R., Dralands, G., and Crolla, D., and van den Bergh, P.: Pseudotumor cerebri due to intracranial arteriovenous malformation. Clin. Neurol. Neurosurg. 82:119, 1980. 27. Corbett, J. J., Savino, P. J., Thompson, H. S., Kansu, T., Schatz, N. J., Orr, L. S., and Hopson, D.: Visual loss in pseudotumor cerebri. Follow-up of 57 patients from five to 41 years and a profile of 14 patients with permanent severe visual loss. Arch. Neurol. 39:461,1982. 28. Kirkham, T. H., Sanders, M. D., and Sapp, G. A.: Unilateral papilledema in benign intracranial hypertension. Can. J. Ophthalmol. 8:533, 1973. 29. Maxner, C. E., Freedman, M. I., and Corbett, J. J.: Asymmetric papilledema and visual loss in pseudotumor cerebri. Can. J. Neurol. Sci. 14:593, 1987. 30. Sedwick, L. A., and Burde, R. M.: Unilateral and asymmetric optic disk swelling with intracranial abnormalities. Am. J. Ophthalmol. 96:484, 1983.
Two men, aged 59 and 36 years, had large, intracranial arteriovenous malformations. Both patients developed severe, bilateral visual loss secondary to unrecognized chronic papilledema. Lumbar puncture disclosed increased intracranial pressure. Neuroimaging disclosed only vascular malformations. The patients were treated by embolization of the vascular malformations and ventriculoperitoneal shunting procedures. The malformation of one patient was excised.
T HE LACK of consistent correlation between the clinical features and the size, location, and vascular patterns of intracranial arteriovenous malformations is well known.' This lack of correlation has been related to the congenital nature of the malformation and to the mechanisms by which symptoms may be produced, such as hemorrhage or mass effect."! Visual field loss in arteriovenous malformations is a well-known sequela of increased intracranial pressure secondary to hemorrhage, hematoma, or obstructive hydrocephalus.l-' We treated two patients who had severe visual field loss secondary to chronic papilledema attributable to increased intracranial pressure.
Accepted for publication Feb. 27, 1990. From the Departments of Ophthalmology (Drs. Kashii, Solomon, Tostanowski, and Burde), Radiology (Dr. Moser), and Neurological Surgery (Drs. Moser and Burde), Albert Einstein College of Medicine, Bronx, New York. This study was supported in part by an unrestricted grant to the Department of Ophthalmology, Albert Einstein College of Medicine, from Research to Prevent Blindness, Inc., New York, New York. Reprint requests to Ronald M. Burde, M.D., Department of Ophthalmology, Albert Einstein College of Medicine, Montefiore Medical Center, 111 E. 210th St., Bronx, NY 10467.
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Case Reports Case 1 A 59-year-old right-handed man complained of severe visual loss in March 1988. In January 1976, he had a syncopal episode associated with nausea, vomiting, and general malaise. A brain scan performed at that time reportedly showed increased uptake in the right posterior temporal lobe area. Cerebral angiography showed a dural and tentorial arteriovenous malformation with deep extension. Results of neurologic evaluation were normal. The optic disks were normal. No definitive treatment was recommended. The patient was lost to follow-up until May 1980, at which time the patient had a generalized tonic-clonic seizure associated with a oneto two-minute episode of loss of consciousness. A diagnosis of temporal lobe seizures secondary to the arteriovenous malformation was made. The presence and size of the arteriovenous malformation were confirmed again by cerebral angiography. The patient was treated with phenytoin (400 mgj'day) to control the seizure activity. The patient did not seek further medical attention until August 1985 when he complained of difficulty seeing. Neurologic evaluation disclosed blurring of the nasal margins of the optic disk in the right eye and elevation of the disk margin 360 degrees in the left eye. The results of the remainder of the neurologic evaluation were noncontributory. A computed tomographic scan performed in March 1986 disclosed a large arteriovenous malformation that involved much of the right temporal, parietal, and occipitallobes. The patient was first examined by an ophthalmologist in February 1989 for decreased vision in his right eye of several months' duration. Pertinent findings on examination included a
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visual acuity of R.E.: counting fingers at two feet and L.E.: 20/50. Both pupils reacted to light, although the reaction of the right pupil was sluggish. A relative afferent pupillary defect was present on the right side. Ophthalmoscopic examination of the right eye disclosed optic atrophy with blurring of the disk margin nasally, sheathing of vessels at the 5:00 o'clock meridian with arteriolar narrowing, and absence of spontaneous venous pulsations. The margins of the left disk were blurred for 360 degrees, and a small refractile body was present at the disk border at the 6:00 o'clock meridian. There were no spontaneous venous pulsations. Kinetic visual fields performed with a Goldmann perimeter disclosed a temporal island in the right eye only and large superior and temporal defects in the left eye (Fig. 1). The patient was admitted to our institution for further examination and treatment. A fourvessel angiogram confirmed the presence of a large arteriovenous malformation along the edge of the tentorium predominantly on the right side (Fig. 2). The main arterial supply came from branches of the external carotid artery, including the middle meningeal artery, the internal maxillary artery, and the suboccipital artery. Some branches from the vertebral
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artery and middle cerebral artery also supplied blood to the malformation. Venous drainage occurred through the straight sinus and the sigmoid sinus by means of multiple collateral vessels. Embolization of the malformation was performed by using both the right external carotid and the right middle meningeal arteries. On the basis of the presence of chronic disk edema with significant visual field loss, the neuro-ophthalmological service requested that the patient undergo a lumbar puncture. The neurosurgical service was uncertain about the indications for this procedure, but acquiesced, and a lumbar puncture was performed. The opening pressure was 480 mm H 20 . A ventriculoperitoneal shunting procedure was then performed to decompress the patient's optic nerves. The patient's visual function test results remained unchanged after surgery, but ophthalmoscopic examination showed decreased papilledema in his left eye and spontaneous venous pulsations. The patient was seen again in May 1988, at which time there was minimal further loss of temporal field in the right eye and constriction of the inferior nasal field in the left eye. Repeat lumbar puncture was recommended but refused.
Fig. 1 (Kashii and associates). Patient 1. Kinetic visual fields performed on a Goldmann perimeter show the superior temporal field defect in the left eye associated with a significant visual field defect in the right eye, which fits the definition of "junctional scotoma."
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Fig. 2 (Kashii and associates). Patient 1. Left, Selective angiogram shows dural arteriovenous malformation developing from right meningeal artery. Right, Left vertebral angiogram shows emissary artery feeding dural arteriovenous malformation from muscular branches of left vertebral artery.
Case 2 A 36-year-old right-handed man with a known intracranial arteriovenous malformation that was diagnosed in 1981 was examined in March 1988 for a progressive visual field loss in both eyes. In 1981, the patient began to have generalized tonic-clonic seizures. At that time, examination included an electroencephalogram, a computed tomographic scan, and an angiogram, which showed the presence of a large, right parietal arteriovenous malformation. The patient first noted a problem with his vision in 1985, at which time he complained of decreased vision in his left eye. The only afferent visual system finding was bilateral papilledema. No visual field testing was performed. A computed tomographic scan again confirmed the presence of a right parietotemporal arteriovenous malformation with large feeding channels, and it was presumed that the chronic disk edema was caused by a mass effect. The patient was lost to follow-up until February 1986, at which time neuro-ophthalmologic examination disclosed a visual acuity of R.E.: 20/30 and L.E.: hand motions. Ophthalmoscopic examination showed evidence of severe optic atrophy without disk elevation. The patient was lost to follow-up again until March 1988, at which time he returned because of severe visual difficulties. Complete ophthalmic
examination at that time disclosed a visual acuity of R.E.: 20/25 and L.E.: light perception superonasally. The pupils were 4 mm and 5 mm on the right and left, respectively, and reacted sluggishly to direct light stimulation at 3 mm and 4 mm, respectively. There was a markedly positive relative afferent pupillary defect on the left side. On ophthalmoscopic examination, the optic disks were pale and flat with sharp margins. There was no evidence of edema, hemorrhage, or infarction. Kinetic visual fields done both on a tangent screen at 1, 2, and 3 m and on a Goldmann perimeter disclosed a small, centrally skewed island of vision (Fig. 3). On the basis of optic atrophy and history of papilledema, lumbar puncture was recommended. The neurosurgical service acquiesced again, and the opening pressure was 310 mm H20 . A computed tomographic scan did not differ significantly from the one done in 1985. A cerebral angiogram showed slow filling of a large, right frontoparietal arteriovenous malformation through feeders mainly from the right middle cerebral artery and, to a lesser degree, from the right posterior cerebral artery and the right anterior cerebral artery. The malformation was drained by two large, superficial, cortical veins that emptied into the superior sagittal sinus. A ventriculoperitoneal shunt procedure was performed (Fig. 4). Embolization therapy was
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Fig. 3 (Kashii and associates). Patient 2. Kinetic visual field performed on a Goldmann perimeter shows a small, S-degree central island slightly skewed temporally. The visual acuity of the left eye is light perception. subsequently initiated, followed by a craniotomy with partial removal of the arteriovenous malformation. The visual field remained unchanged. In June 1986/ the patient underwent removal of the residual tumor.
Immediately after surgery, the patient complained of loss of vision in his right eye. A computed tomographic scan showed a large, hypodense, extra-axial collection under the right craniotomy flap with ventricular efface-
Fig. 4 (Kashii and associates). Patient 2. Left, A frontal view and right, a lateral view of the right internal carotid arteriogram show the large arteriovenous malformation located mainly in the parietal region. The malformation is fed from the right middle cerebral artery. The ventriculoperitoneal shunt cannula can be seen in the right lateral ventricle.
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ment and compression. After drainage by means of a twist drill, the patien t' s vision returned to its preoperative state.
Discussion Both of our patients lost visual function because of the unrecognized consequences of chronic papilledema secondary to raised intracranial pressure. Evidence of chronic papilledema was present in Patient 1, whereas Patient 2 had advanced optic atrophy with a history of papilledema and a lumbar puncture that confirmed the presence of increased intracranial pressure. Papilledema and raised intracranial pressure are unusual signs of a cerebral arteriovenous malformation in the absence of severe secondary intracranial hemorrhage or hematoma, unless the arteriovenous malformation is huge. In 110 patients with cerebral arteriovenous malformation, Paterson and Mckissock" found only one patient who had papilledema without a specific cause. Intracranial arteriovenous malformations have been classified angiographically on the basis of their arterial supply as purely dural, mixed dural and pial, and purely pial.' Pure dural malformations are limited to the dura and receive only meningeal arterial blood. Mixed dural and pial malformations receive their blood supply not only from meningeal vessels but also from cerebral or cerebellar arteries. Purely pial malformations are intracranial lesions that are supplied only by cerebral or cerebellar arteries, without meningeal contribution. Dural arteriovenous malformations are generally rare. They comprise 6% to 12% of intracranial arteriovenous malformations-" and occur predominantly in women over 40 years of age." Dural malformations in the posterior fossa are far more common than are those above the tentorium. Of the supratentorial arteriovenous malformations in one study, only 6% were dural, but of the infratentorial malformations, 35% were dural.' The malformation of Patient 1 is classified as mixed dural-pial because of its arterial supply. It is, however, more predominantly of the dural type, because most of its blood supply is derived from dural vessels. As early as 1968, dural arteriovenous malformations that developed in the posterior fossa were regarded as a distinct entity because of their frequent association with pseudo tumor-
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like symptoms.v" In two studies, 14% to 24% of patients with dural malformations involving the transverse sinus were reported to have papilledema.P:" but the authors included patients in whom hydrocephalus or subarachnoid hemorrhage also existed. Recently, Houser and assocrates" reported that five of 14 of their patients with dural arteriovenous malformations that affected the transverse sinus had increased intracranial pressure and no history of subarachnoid hemorrhage or hydrocephalus. The investigators postulated that dural sinus occlusion precedes the development of dural arteriovenous malformations in the transverse sinus. Most posterior fossa dural malformations develop within or in direct proximity to a major venous sinus. These malformations raise the venous pressure by direct shunting of arterial blood,":" and this is believed to be the primary cause of papilledema in dural arteriovenous malformations in the posterior fossa .14-16 Pial arteriovenous malformations are the most common intracranial arteriovenous malformations (72%).5 They affect men slightly more often than they affect women. 17,18 They are associated with the triad of hemorrhage, seizures, and recurrent headaches." Chronic increased intracranial pressure without a history of either intracranial hemorrhage or hydrocephalus, however, is rare in pial malformations. 2 ,20-23 The difference in inducing raised intracranial pressure between dural and pial malformations appears to be attributable to the direct drainage of the enlarged dural arteries into involved sinuses. This produces a rise in venous pressure in dural malformations, whereas pial malformations rarely shunt directly into the dural sinuses": rather they increase venous pressure because of the massive runoff from large shunting vessels, which produces increased cerebral blood volume and decreased cerebrospinal fluid absorption. 14,2o,22,23,25,26 Both of our patients had pial malformations functionally. The malformation of Patient 1 could, on the basis of the origin of its blood supply, be classified as a dural malformation, but it did not directly shunt blood into the venous sinuses. Thus, the finding of increased intracranial pressure suggests that the malformation is acting as though it were pial. Increased intracranial pressure has been long known to cause bilateral papilledema. Only rarely has it been recognized that asymmetric papilledema may occasionally be seen in patients with pseudotumor cerebri, especially at initial examination.F:" Based on the presence of
Vol. 109, No.5
Intracranial Arteriovenous Malformations and Visual Field Defects
a relative afferent pupillary defect, one study of a large series of patients with pseudotumor cerebri estimated that asymmetric visual field defects were seen in 16 of 59 (28%) patients.F In our Patient 1, the left eye had a superotemporal field defect that respected the vertical meridian, whereas only a temporal island of vision remained in the right eye. Although the loss of the left homonymous field in both eyes is explained on the basis of the location and size of the arteriovenous malformation, the remainder of loss of visual function is most likely attributable to field loss associated with the optic atrophy of chronic disk edema. Decreased vision in one eye with a superotemporal field defect in the fellow eye suggests a junctional scotoma. There is no visible mass effect, however, in the region of the right prechiasmal optic nerve as reaffirmed by multiple neuroradiologic examinations, including mag-
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netic resonance imaging (Fig. 5). It is possible that the asymmetry seen may be attributable to a steal phenomenon from the ophthalmic artery to the arteriovenous malformation. In Patient 2, the observation of bilateral papilledema early in the course of the process, which is documented in his old record, leads us to postulate that there must have been intermittent increases in intracranial pressure that eventually produced almost total loss ofaxons. This loss ofaxons precluded the development of disk elevation even with a substantiated increase in intracranial pressure at the time of our observation. The clinician should be aware of this infrequent cause of papilledema. Intracranial arteriovenous malformations, whether dural or pial in type, can produce an asymptomatic chronic increase of intracranial pressure. Treatment should be aimed primarily at the underlying arteriovenous malformation. The associated development of chronic papilledema can produce progressive visual loss; patients with papilledema, like those with pseudotumor cerebri, must have sequential visual field testing on a regular basis. If progressive loss of visual field is documented over one to four weeks, a shunting procedure or an optic nerve sheath fenestration should be performed.
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Fig. 5 (Kashii and associates). Patient 1. Magnetic resonance image, T2-weighted, shows a large, brighter (hyperdense) area that corresponds to the parietotemporal arteriovenous malformation. There is no visible mass in the right prechiasmal region. (Left is the patient's right, and right is the patient's left.)
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