Background: Fibrous dysplasia (FD) is most often a slowly progressive benign disease in which the normal bone structure is replaced by fibrous and osteoid tissue.
Case description: A 16-year-old adolescent, known with FD in the sphenoid bone, suffered an acute decreased visual acuity with papilledema on the left eye. The radiologic images were best compatible with cystic degeneration of the known FD with optic nerve compression in the optic canal. Decompression of the optic nerve was performed through an endoscopic exploration of the left sphenoid sinus. The visual acuity recovered completely.
Conclusions: In FD with cystic changes, leading to acute signs of optic nerve compression, early aggressive surgical decompression is strongly recommended. Cystic degeneration of the FD, although rare, should be considered.
Keywords: Cystic degeneration; Fibrous dysplasia; Optic nerve compression.
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