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Show ]. Clin. Neuro-ophthalmol. 4: 91-95, 1984. Optic Atrophy and the WyburnMason Syndrome RONALD DANIS, M.D. RICHARD E. APPEN, M.D. Abstract A 14-year-old girl developed impaired vision and optic atrophy of the left eye as a manifestation of an orbital and parachiasmal arteriovenous malformaton. Despite the lack of a retinal arteriovenous malformation, this condition appears to be a variant of the Wyburn-Mason syndrome, representing a vascular dysgenesis of the orbit and midbrain resulting in focal arteriovenous communications without interposed capillaries. The Wyburn-Mason syndrome consists of a unilateral arteriovenous malfonnation affecting the visual pathways and the midbrain, and occasionally subcutaneous facial structures.] The disorder stems from a vascular dysgenesis in an early embryonic period, and the extensiveness of the lesion varies widely. Because of the frequent involvement of the visual pathways by this vascular malformation, it is important for ophthalmologists to understand the diversity of manifestations which can occur. The purpose of this report is to describe a patient who sustained unilateral loss of vision as the manifestation of this lesion, and to review the pathogenesis and nomenclature of such arteriovenous malfonnations. Case Report In March 1978, a 14-year-old white girl had experienced blurred vision of the left eye for 4 months, with mild left temporal headache and vague discomfort about the left orbit. She had no history of congenital cutaneus lesions, although her father and a maternal aunt reportedly had "birthmarks: The physical examination revealed an alert, healthy-appearing adolescent girl. Aside from visual abnonnalities, the neurological examination revealed normal findings except for question- From the Department of Ophthalmology, University of Wisconsin Center for Health Sciences, Madison, Wisconsin. June 1984 able weakness of the right trapezius muscle. There were no cutaneous lesions. Visual acuity of the right eye was 20/15, and of the left, 20/100. There was no exophthalmos, and the ocular motility was nonnal. The pupils were equal, but there was a marked relative afferent pupil defect of the left eye. The visual field of the right eye was nonnal, while that of the left showed only a nasal island of vision remaining. The anterior segments and intraocular pressure were normal. The right optic disc was nonnal, but there was marked atrophy of the left (Fig. 1). The peripheral retina was bilaterally nonnal with indirect ophthalmoscopy. No bruits were audible. Laboratory evaluation disclosed nonnal hematologic values and blood chemistry screening panel results. Skull roentgenograms showed a normal sella turcica without calcification. The right optic foramen was nonnal, but the left was enlarged (Fig. 2). Computed tomography demonstrated enlargement of the intraorbital portion of the left optic nerve, and a contrast-enhancing left-sided mass in the suprasellar cistern. Pneumoencephalography confirmed this finding. There was effacement of the optic and infundibular recesses of the anterior third ventricle. The cerebrospinal fluid was normal. With the expectation that the patient had an optic nerve and chiasm glioma, a left frontal craniotomy was performed and disclosed an arteriovenous malformation involving the left optic nerve, chiasm, and hypothalamic area. Subsequent arteriography showed the vascular malformation extending from the posterior third of the orbit along the course of the left optic nerve to involve the optic chiasm and midbrain (Fig. 3). The remainder of the cerebral vasculature was nonnal. In July 1978, the orbital and parachiasmal portions of the lesion were resected through a frontal craniotomy. The specimen excised was 1.5 X 1.0 cm mass of bluish, coiled, dilated vessels. Histopathologic evaluation demonstrated findings characteristic of an arteriovenous malfonnation (Fig. 4). There were various-sized blood-containing channels with walls of varying thickness. Many of the vascular elements contained elastic 91 Wyburn-Mason Syndrome Figure 1. Optic discs of right (A) and left (8) eyes in March 1978, depicting atrophy of the left optic disc. Figure 2. Radiographic views of optic foramen of right (A) and left (8) orbits, demonstrating smooth enlargement of the left. tissue and smooth muscle, indicating their arterial nature. Other components had venous characteristics. No capillaries were present. There was no evidence of thrombosis in the lesion. The vessels were loosely bound together in fibrous tissue. 92 Postoperatively, the patient was blind in the left eye. The visual acuity in the right was 20/20 despite a small scotoma in the nasal field. Four years later, the patient was generally well and had experienced no change in her vision. Journal of Clinical Neuro-ophthalmology Danis, Appen Figure 3. Lateral view of left carotid angiogram shows the arteriovenous malformation extending from the posterior orbit. [Note choroidal blush (C) indicating location of eyeball] to the area above sella turcica (5). Figure 4. Microscopic section of lesion resected at craniotomy, revealing the 'abnormal arteries and veins without capillaries. Variable amount of elastic tissue indicates the anomalous character of the arteries. (Van Giesen stain, original magnification XSO.) June 1984 93 Wyburn-Mason Syndrome Discussion In 1937, Bonnet, Dechaume, and Blanc first reported the association of retinal vascular malformations with ipsilateral cerebral arteriovenous malformations and facial nevi. 2 In 1943, the first description in the English literature was reported by Wyburn-Mason, whose name generally provides the eponym for this syndrome. Subsequently, this disorder, classified by some as one of the phakomatoses, has been recognized to have a spectrum of severity of involvement. An arteriovenous malformation results from abnormal persistence of the embryonic vascular stage which exists before the differentiation of arteries, veins, and capillaries occurring during the second month of gestation.1,3 During that embryonic stage, the primitive vascular mesoderm is arranged in a plexus shared by the optic cup and the anterior portion of the neural tube.4 This anterior plexus eventually differentiates into the hyaloid vascular system of the eye, and the vascular supply of the midbrain. If this developing mesoderm fails to develop normally, anomalous vessels may result that consist of inappropriately arranged arteries and veins not separated by a capillary bed. This vascular anomaly in which there exists a direct communication between an arterial and a venous system via multiple vessels, without interposed capillaries, is termed an arteriovenous malformation. Because of the close approximation of the primitive mesoderm of the optic cup and the anterior neural tube prior to closure of the optic cup at about 7 weeks' gestation,4 a disturbance of the developing vascular tissue easily damages the vessels destined to involve both the eye and the midbrain. 1 If the insult to the embryonic tissue occurs after 7 weeks' gestation, it would be much less likely that both portions of the tissue would be damaged, and one might observe such an arteriovenous malformation of either the eye or the midbrain. The Wyburn-Mason syndrome, then, represents the more widespread unilateral dysgenesis of this anterior plexus. Grossly, an arteriovenous malformation appears as a nest of tortuous, irregularly dilated vessels in which it is often impossible to distinguish between the arteries and veins. Microscopically, an arteriovenous malformation represents a direct end-to-end anastomosis of the arterial to the venous system. However, the histology of the vessels is frequently abnormal. The arterial internal elastic lamina may be distorted or absent. The media may be irregular and thinned and is susceptible to aneurysm formation. Veins may be thickened due to collagenous hyalinization. Other degenerative changes such as fibrosis and atheromatous plaques with calcification can occur. There may be thrombosis with varying stages of 94 organization.s These degenerative changes of an arteriovenous malformation can result in an intracranial hemorrhage, which occasionally is fatal. It is evident that an arteriovenous malformation is a high-flow vascular anomaly that has a potential for decompensation. Manifestations of the Wyburn-Mason syndrome can be cerebral or ocular. Headaches, seizures, or subarachnoid hemorrhage are the usual indicators of involvement of the central nervous system, although the specific symptoms and signs will vary depending on the location and extent of the arteriovenous malformation. The arterial blood supply is more often from the internal carotid system than from the vertebral-basilar or external carotid system.S-7 Venous drainage is primarily via the cavernous sinus or vein of Galen. Since involvement of the visual pathways is common, corresponding visual field defects frequently occur. However, the presence of an intracranial arteriovenous malformation does not invariably indicate that neurologic sequelae will occur, as many arteriovenous malformations probably remain asrmptomatic throughout the life of an individual. It is not clear whether the mechanism of damage to structures adjacent to an AVM is due to compression from expansion of the vascular malformation, due to hemorrhage into the adjacent structure, or due to ischemia from impairment of the perfusion of the adjacent structure. Perhaps in our patient, the vision loss was caused by compression of the optic nerve in the optic canal where changes in the size of the AVM would have been likely to result in compression of the optic nerve where the bone of the surrounding optic canal restricted any change in volume of the lesion. Of interest is the fact that the AVM was adjacent to the optic chiasm in our patient, without causing damage to the chiasmal crossing nasal fibers from the right eye, as indicated by the normal visual field of the right eye. Ocular manifestations are usually an important clue to the diagnosis of this syndrome. The retinal lesions, generally unilateral, range from ophthalmoscopically barely visible communications to large masses of tortuous and dilated vessels covering a substantial portion of the retina.8 The larger complexes usually cause cystic retinal degeneration between the dilated vessels and result in impaired vision. However, retinal involvement is not essential for the diagnosis of the Wyburn~ ason ~yndrome. Brown et al. reported two patIents With normal fundi, but other manifestations of the syndrome9 and six of Wybum-Mason's original series had no retinal abnormalities.1 Other orbital manifestations which can occur include optic atrophy,3,9.10 enlargement of the optic foramen,8, 9 and occasionally exophthalmos Journal of Clinical Neuro-ophthalmology which may be pulsatile. Orbital bruits are sometimes detected. Dermatologic lesions occur in a minority of reported cases.v A vacular nevus similar to that of the Sturge-Weber syndrome can occur. These lesions may be blatant or may be only faint erythematous discolorations of the skin in the trigeminal distribution, ipsilateral to the retinal or cerebral lesions. The deeper structures of the face, such as the frontal and maxillary sinuses and mandible, can be involved and severe epistaxis or gingival hemorrhage may resuIt. 7 . 9 Although arteriovenous malformations have little neoplastic potential and are considered a hamartoma, they are dynamic structures which change with time. Substantial remodeling of an arteriovenous malformation has been observed in the retina and is evident on pathologic evaluation of intracraniallesions.8 • 11 Atrophy of some vessels occurs concurrently with dilation and expansion of others within the same lesion. These changes are most likely directed by hemodynamic forces caused by spontaneous thrombosis in parts of the complex. Progression of neurologic signs may occur secondary to these changes. While arteriovenous malformations have been described in the medical literature for many decades, the vocabulary used to describe them has been inconsistent and misleading. Such terms as arteriovenous aneurysms, racemose aneurysms, or cirsoid aneurysms have been applied inappropriately since the lesion is fundamentally not an aneurysm.5. b Arteriovenous malformations have also been called hemangiomas, cavernous hemangiomas, and venous angiomas,S but the histopathologic charactristics of an arteriovenous malformation are distinct from these vascular hamartomas. Recent proponents for unifying the nomenclature have suggested the term 'arteriovenous communication· to describe the anatomic structure.b. 7 However, the term •arteriovenous malformation· seems more appropriate because it alludes to the underlying pathogenesis and the term is already in widespread usage. Theron et al. 7 have suggested the name 'unilateral retinocephalic vascular malformations· to describe this constellation because the cutaneous lesions are not prevalent, and the full Wyburn- June 1984 Danis, Appen Mason syndrome is, therefore, quite rare. However, the diagnosis of Wyburn-Mason syndrome has been applied to cases lacking retinal manifestations. Y Even localized midbrain lesions are etiologically related to the Wyburn-Mason syndrome and could be considered a forme fruste of the complete syndrome. The lack of consensus on appropriate terminology reflects the diverse nature of the disease. References 1. Wyburn-Mason, R: Arteriovenous aneurysm of mid-brain and retina, facial naevi and mental changes. Brain 66: 163-209,1943. 2. Lalonde, G., Duquette, P.. Laflamme, P., and Vezina, J.: Bonnet-Dechaume-Blanc syndrome. Can. I. Ophthalmol. 14: 47-50,1979. 3. Dibony, P., Lessell, 5., and Wray, 5.: Chiasmal syndrome created by arteriovenous malformations. Arch. Ophthalmol. 100: 438-442, 1982. 4. Langman, J.: Medical Embryology (3rd ed.). Williams & Wilkins, Baltimore, 1975, p. 368. 5. Russell, D., and Rubinstein, L.: Pathology of Tumors of the Nervous System (3rd ed.). Williams & Wilkins, Baltimore, 1971, p. 100. 6. Yanoff, M., and Fine, B.: Ocular Pathology, a Textbook and Atlas. Harper & Row, Hagerstown, 1975, p.37. 7. Theron, J., Newton, T., and Hoyt, W.: Unilateral retinocephalic vascular malformations. Neuroradiology 7: 185-196, 1974. 8. Archer, D., Deutman, A., Ernest, T., and Krill, A.: Arteriovenous communications of the retina. Am. I. Ophthalmol. 75: 224-241, 1973. 9. Brown, D., Hilal, 5., and Tenner, M.: WybumMason syndrome: Report of two cases without retinal involvement. Arch. Neural. 28: 67-68,1973. 10. Bard, R: Optic atrophy caused by an arteriovenous angioma. Arch. Neurol. Psychiatry 67: 655-660, 1952. 11. Augsberger, J., Goldberg, R., Shields, J., Mulberger, R, and Magargal, L.: Changing appearance of retinal arteriovenous malformation. Albrecht von Graefes Arch. Klin. Exp. Ophthalmol. 215: 65-70, 1980. Write for reprints to: Richard E. Appen, M.D., Department of Ophthalmology, University of Wisconsin Center for Health Sciences, 600 Highland Avenue, Madison, Wisconsin 53792. 95 |
