FD is a benign lesion with a low rate of malignancy. Typical classification of FD includes three variants: monostotic, polyostotic, and McCune-Albright syndrome (associated with endocrinopathies and skin hyperpigmentation) [2, 6]. CFD usually starts in infancy. After a slow growth, typical symptoms will appear in childhood or adolescence. It will then enter a stable stage and finally stop processing during adulthood. However, in a small proportion of cases, the course of the disease can reach 70 years [7]. In this case, the 22-year-old patient suffered significant facial deformities. She had a long history of progression, but facial deformity, visual acuity, and visual field remained stable about ten years ago. Her disease course was typical.
For the diagnosis of FD, clinical, radiographic, and histopathological features are usually necessary. Besides, examinations, including visual acuity, visual field, color vision, and VEP tests are crucial for ophthalmologists. Pathologically, spindle cells surrounded by a fibrous matrix will replace the normal bone [8]. CT representation of FD consists of three varieties: pagetoid, or ground-glass pattern (56%), sclerotic lesions (23%) and cystic variety (21%) [9]. The characteristics of FD in CT include the expansion of the involved bone with a heterogeneous pattern of CT densities associated with scattered or confluent islands of bone formation. Specifically, almost all CT findings of CFD show the glass-like changes [10]. Hence, it is usually the first choice to choose CT for the examination of CFD. As for our patient, our CT results showed a homogenous, “ground-glass” lesion, with a left predominant expansion of the ethmoid and the temporal bone. CT images after the surgery presented our removal of the mass. Differential diagnosis should include nonossifying fibroma, fibrous dysplasia of bone, aneurysmal bone cysts, osteoma, giant cell tumor of bone, low osteosarcoma, low degree chondrosarcoma, and fracture healing. History, location, and biopsy are essential for the identification of certain diseases [1].
There are no standard treatments for FD currently, but it is recognized that tailored approaches according to the characteristics of the patient will be more appropriate. Surgical treatments will be required when symptoms occur and progress, especially when bothering one’s daily activities. If the optic nerve is involved, either therapeutic or prophylactic decompression should start as soon as possible. Prophylactic decompression is performed to avoid further progression of visual loss caused by compression of optic canal stenosis, but the loss of vision is still difficult to control. While the effect of therapeutic decompression remains controversial, some experts believe that if the thickness of the retinal nerve fiber layer is in normal status, visual function can recover after decompression. On the contrary, if the nerve fiber layer has thinned, decompression cannot reverse the process, and the decline in visual acuity will progress [2]. The aims for surgical treatment are not only for cosmetic purposes but also to restore the physiological function of the affected organ. Although FD is usually of the multi-bone type involves a wide range of bones without clear boundaries, the recurrence rate is low in adult patients. Orbital bones will be removed to expose the surgical area, but extensive resection can lead to severe secondary deformities and damage to facial function. Therefore, sufficient hemostasis and precise operation are necessary to prevent accidental injury to the optic nerve. Otherwise, visual acuity may be irreversibly damaged.
During our examination, VEP displayed a functional loss of visual pathway, while OCT proved the structural damage to the optic nerve. After the removal of an appropriate amount of orbital bone during surgery, her appearance considerably improved. Surprisingly, visual acuity was preserved, and we observed an overall improvement in her visual function. Besides, the central visual field area enlarged at one month after surgery. Other than emergent decompression to salvage one’s vision [11], our case indicated that even when the compression has damaged the optic nerve for a prolonged disease course, relieving the compression can still improve visual function partially. Possible explanation was that the central visual field might be recently affected, which was therefore reversible. However, overall or quadrant thickness of retinal nerve fiber, which was most commonly used to assess the structure of optic nerve, could not distinguish that. Such phenomenon further displayed the importance of early decompression surgery in order to salvage the potential function of vision.
The patient's eye position was still oblique after surgery, and the left eye was not able to turn inward, which was one of the limitations of our treatments. We believed that the extraocular muscle was damaged but functional exercise can accelerate her recovery. There is no definite information in the literature currently on how long it might take to restore the extraocular muscle movement to preoperative levels. This case is still being followed-up and we wish to determine whether the oblique position can recover and provide reference data for the treatment of future patients.