Reversible Visual Loss Caused by Fibrous Dysplasia

Reversible Visual Loss Caused by Fibrous Dysplasia Joseph S. Weisman, M.D., Major, U.S.A.F., M.C., Robert S. Hepler, M.D., and Harry V. Vinters, M.D.

Fibrous dysplasia is a developmental anomaly of bone, often affecting the facial bones. We treated a patient who had fibrous dysplasia involving the right maxillary and sphenoid bones. The patient had a sudden loss of visual acuity to R.E.: counting fingers. Visual fields demonstrated a central scotoma, and retrobulbar neuritis was diagnosed. When vision failed to improve spontaneously, however, radiologic studies were performed. These showed compromise of the optic canal by bony proliferation and an apparent mucocele at the orbital apex. Surgical exploration disclosed fibrous dysplastic bone and a cystic structure overlying the optic nerve. Successful surgical excision of the cyst and debulking of the fibrous dysplasia resulted in visual acuity returning to R.E.: 20/25. is an abnormal development of bony tissue, which results in fibrous tissue proliferation and imperfect osteogenesis. This may produce facial deformity and asymmetry. Rarely, the abnormal bony proliferation may cause compression of adjacent structures with compromise of normal function. We treated a patient in whom fibrous dysplasia involving the sphenoid bone with a secondary mucocele resulted in compressive atrophy of the optic nerve at the orbital apex, which produced visual loss. FIBROUS DYSPLASIA

Accepted for publication June 6, 1990. From the Departments of Ophthalmology, Jules Stein Eye Institute, UCLA School of Medicine (Drs. Weisman and Hepler), and Pathology, UCLA Medical Center (Dr. Vinters), Los Angeles, California. The opinions expressed herein are those of the authors and do not purport to express the opinions of the United States Air Force or the Department of Defense. Reprint requests to Robert S. Hepler, M.D., Jules Stein Eye Institute, 800 Westwood Plaza, Los Angeles, CA 90024.

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Case Report A 29-year-old woman had right-sided fibrous dysplasia, which caused marked facial asymmetry. In 1982 the patient underwent removal of the floor of the right orbit as part of a procedure intended to improve cosmesis. Visual acuity remained R.E.: 20/20 after the operation. In March 1985, the patient had a sudden, severe, right-sided headache, retrobulbar in location. There was pain on versions to the right and decrease in visual acuity to R.E.: counting fingers. A moderate relative afferent pupillary defect was noted on the affected side with a normal disk appearance. Goldmann visual field testing showed a dense central scotoma involving the central 20 degrees of vision in the right eye, with a normal field of vision in the left eye. A computed tomographic scan of the orbits showed extensive changes of fibrous dysplasia involving the right maxillary, ethmoid, and sphenoid bones. Asymmetry in the orbits with a 2-mm proptosis of the right globe was seen. No bony encroachment of the optic nerve was demonstrated. Retrobulbar neuritis was diagnosed, and the patient was given prednisone. Two months later, visual acuity had returned to R.E.: 20/20, with resolution of the afferent pupillary defect. Over the ensuing two years, the patient did well without any other focal neurologic signs or symptoms. In June 1987, the patient again had an aching pain over the right temporal fossa associated with pain upon horizontal ductions of the right eye. One day after the onset of symptoms, she noted dimming of central vision in her right eye associated with poor color perception. Visual acuity deteriorated rapidly over the next 24 hours, so that the patient could only distinguish shapes but no detail or color with the right eye. Visual acuity was R.E.: counting fingers associated with an afferent pupillary defect. Generalized enlargement of the right side of the face was noted with propto-

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Fig. 2 (Weisman, Hepler, and Vinters). Axial computed tomographic scan of head showing fibrous dysplastic bone obliterating the right optic canal and a cystic lesion in the area of the right orbital apex. Fig. 1 (Weisman, Hepler, and Vinters). Preoperative visual field of the right eye demonstrating large central scotoma.

sis and exophthalmometry readings of R.E.: 21.5 and L.E.: 19.5. The appearance of both optic disks was normal. Visual fields documented a central scotoma in the right eye involving the central 20 degrees with a markedly reduced sensitivity of all surrounding isopters (Fig. 1). We believed that this represented a recurrence of the retrobulbar neuritis, and the patient was treated with prednisone, 60 mg per day. Over the ensuing three weeks, however, visual acuity did not improve. A repeat computed tomographic scan showed extension of the fibrous dysplasia involving the sphenoid bone. This dysplastic bone appeared to fill the right optic canal, and a cystic structure originating from the sphenoid sinus, which probably represented a mucocele, was noted at the orbital apex (Fig. 2). A magnetic resonance image confirmed the extensive compromise of the right optic canal. Because of these findings, neurosurgical consultation was obtained. Computed tomography and magnetic resonance imaging findings were considered highly suggestive of compression of the right optic nerve within the optic canal, most likely caused by involvement of the lesser wing of the sphenoid bone by fibrous dysplasia. The patient elected to undergo neurosurgical exploration. In July 1987, a right frontotemporal craniotomy was performed. Bone was significantly overgrown in the temporal region, particularly in

the right sphenoid wing. A rongeur was used to remove this bony overgrowth. Material sent for permanent sections confirmed the diagnosis of fibrous dysplasia (Figs. 3 and 4). Dissection was extended medially toward the right orbital apex, where a cystic space was found to overlie the right optic nerve and replace the right anterior clinoid process. The dura mater overlying the right optic nerve was incised. This maneuver resulted in direct entry into the cystic cavity. The contents of the cystic area consisted of a shaggy, brown-green material. The operating surgeon believed that this cystic structure represented a mucocele. The cystic contents were excised completely, and the dural incision extended anteriorly along the course of the optic nerve. Soft fibrous dysplastic bone pressed upon the nerve medially. Abnormal bone was removed with a curette to achieve decompression of the nerve throughout its orbital course to the point of its entry into the dura mater. The lateral and superior borders of the right optic nerve were then inspected thoroughly, and no evidence of additional compression was found. At the end of the procedure, the right optic nerve was believed to be decompressed completely. The patient tolerated the procedure well without complications. On the fourth postoperative day, the patient noted that her vision had improved, compared with her preoperative status. Best-corrected visual acuity was R.E.: 20/300. The afferent pupillary defect persisted. The ophthalmoscopic appearance was unchanged. The patient continued to do well and was discharged on the sixth postoperative day.

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Fig. 3 (Weisman, Hepler, and Vinters). Sections of the surgically resected material photographed at low (top) and high (bottom) magnification show large amounts of fibrous connective tissue separating islands of woven bone (arrows). Cells within the fibrous component show uniform nuclei without mitotic figures (bottom). The bone shows prominent osteocytes but scant osteoblast or osteoclast activity (hematoxylin and eosin; top, x 76; bottom, x 190).

Re-examination six weeks postoperatively demonstrated improvement of visual acuity to R.E.: 20/25+ 2 • A trace afferent pupillary defect persisted, and mild temporal pallor was seen in the optic nerve head. Repeat visual fields demonstrated complete resolution of the central scotoma (Fig. 5). In June 1990, the patient had sudden right periorbital pain and visual loss. Computed tomographic scans demonstrated recurrence of mucocele compressing the right optic nerve. An emergency craniotomy confirmed the scan

findings, and the mucocele was evacuated. The patient noted immediate restoration of nearly all of her vision one day after the craniotomy.

Discussion Fibrous dysplasia is a developmental abnormality of bone in which normal bone is replaced gradually by fibrous tissue. This process occurs primarily during childhood, although

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Fig. 4 (Weisman, Hepler, and Vinters). Sections of surgical specimen viewed under polarized light show disorganized nature of the coarse woven bone (top), compared with the organized pattern identified in an adjacent normal fragment of bone (bottom) (hematoxylin and eosin, X 76).

progression may continue into adulthood. Chen and Fairholm' reported that fibrous dysplasia may progress during adult life, and that optic nerve function may be impaired if the orbital sphenoid bone is involved. In 1984, Sevel and associates" reported a case in which sudden enlargement of an area of fibrous dysplasia caused by a hemorrhage in its substance

resulted in compression of the optic nerve and consequent reduction of visual acuity to light perception. In their patient, surgical removal of the tumor mass enabled return of visual acuity to 20/20-3. Donoso, Magargal, and Eiferman" described a 13-year-old girl in whom constriction of the optic canal caused by fibrous dysplasia of the lesser wing of the sphenoid accounted

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Fig. 5 (Weisman, Hepler, and Vinters). Visual field of the right eye six weeks postoperatively showing resolution of the central scotoma.

for optic atrophy with visual acuity of 20/80. In this patient, decompression failed to improve vision; however, marked pallor of the nerve had been noted preoperatively. In 1985, Moore, Buncic, and Munro! reported 16 cases of orbitocranial fibrous dysplasia in children, Five of these children had radiologic evidence of narrowing of the optic canal; within this group, two developed optic atrophy and visual loss. There are two types of fibrous dysplasia: monostotic, which involves primarily a single bone or contiguous bones; and polyostotic, which involves multiple bones at different sites." Most patients with disease involving the orbit have the monostotic form. If the sphenoid bone is involved, compromise of the optic canal with compressive optic atrophy may result. In our patient, fibrous dysplasia involving the sphenoid bone led to the development of a sphenoidal mucocele. The fibrous dysplasia and secondary cyst caused marked narrowing of the optic canal with subsequent optic atrophy and visual loss, Successful surgical decompression led to excellent recovery of vision. The radiologic features of fibrous dysplasia involving the orbit have been reported.' On plain films, the lesions may be lytic, sclerotic, or both, A ground glass appearance has been described in affected areas, These lesions may be mistaken for other entities such as en plaque

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meningioma, Paget's disease, or bone cyst. Computed tomography and magnetic resonance imaging may be used to differentiate these entities and to define more precisely the boundaries and extent of involvement of the lesion, On histopathologic examination, the major change is fibrous tissue replacement of the medullary centers of bone. Cells sometimes arrange concentrically around a zone of developing cartilage, Small islands of poorly calcified bone, as well as irregular trabeculae of bone with attached fibrous tissue, may be found." The term, "immature woven bone," has been used widely by ophthalmologists to describe the overall microscopic appearance of these specimens. The fibro-osseous proliferative tissue is highly vascular and causes extensive, dispersed, low-flow bleeding when surgically excised. The inner surface of bone cortex surrounding these areas of fibrous proliferation may become eroded as the disease progresses, but the outer surface of the cortex remains intact.! In our patient, two classic histologic characteristics of fibrous dysplasia were seen, First, there were many fibroblasts with accompanying fibrovascular proliferation between the bony lamellae. Additionally there were multiple pockets of immature, woven bone. Several ocular complications have been reported in association with fibrous dysplasia. These include proptosis and secondary exposure keratitis, restriction of motility with resultant diplopia, blepharoptosis, epiphora, and visual field loss.4,5 When the orbital maxilla is involved, the globe is pushed upward; if the orbital roof is involved, as in our patient, hypoglobus occurs. If the eye has been displaced for many years, a dull aching pain may occur around the orbit." Involvement of the sphenoid bone with fibrous dysplasia may lead to compromise of the optic canal. This process may lead physicians to conclude erroneously that a meningioma is present; however, the degree of facial asymmetry seen with fibrous dysplasia is rarely seen with meningiomas. When visual loss occurs from compression of the optic nerve, surgical decompression should be undertaken promptly, as some of the atrophic changes may be reversible in their early stages. The origin of this disease is not clearly understood. Possibly, it involves a defect in the boneforming mesenchyme." The disease is usually most active during the second and third decades, when growth maturation occurs. No cases

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of malignant transformation of orbital fibrous dysplasia have been reported."

References 1. Chen, Y. R., and Fairholm, D.: Fronto-orbitosphenoidal fibrous dysplasia. Ann. Plast. Surg. 15:190, 1985. 2. Sevel, D., James, H. E., Burns, R., and Jones,

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K. L.: McCune-Albright syndrome (fibrous dysplasia) associated with an orbital tumor. Ann. Ophthalmol. 16:283, 1984. 3. Donoso, I. A., Magargal, L. E., and Eiferman, R. A.: Fibrous dysplasia of the orbit with optic nerve decompression. Ann. Ophthalmol. 14:80, 1982. 4. Moore, A. T., Buncic, J. R., and Munro, J. R.: Fibrous dysplasia of the orbit in childhood. Ophthalmology 92:12, 1985. 5. Henderson, J. W.: Orbital Tumors, ed. 2. New York, Brian C. Decker, 1980, p. 70.

OPHTHALMIC MINIATURE

If there ever was a justification for the Bastille, it was the Marquis de Sade. But if the crimes which put him there were unusually disgusting (by the standards of any century), his living conditions were not. He received visits from his long-suffering wife almost weekly and when his eyes deteriorated from both reading and writing, oculists came to see him on a regular basis. Like others in the "Liberty" tower, he could walk in the walled garden courtyard and on the towers. Only when he abused that right by shouting cheerful or indignant obscenities to passersby (which he did with increasing frequency in 1789) was it curtailed. Simon Schama, Citizens New York, Alfred Knopf, 1989, pp. 391-392