Objective and importance: A unique case of a large intradiploic arachnoid cyst involving craniofacial osseous structures is reported.
Clinical presentation: The patient presented with a hard mass in the right frontal region, proptosis, and inferior globe displacement. Computed tomography revealed an intraosseous cyst of cerebrospinal fluid intensity with extension from the anterior cranial fossa to the infratemporal fossa.
Intervention: After resection of the cyst wall and closure of two small round dural defects, the involved craniofacial region was reconstructed.
Conclusion: The medical history of the patient and the intraoperative observations support the contention that the cyst in the reported case was congenital in origin. The features concerned with diagnosis and pathogenesis of this rare entity are discussed.