Acquired Chiari malformation secondary to hyperostosis of the skull: a case report and literature review.

Background: Most cases of generalized hyperostosis of the skull are associated with Camurati-Engelmann disease, craniodiaphyseal dysplasia, Worth-type endosteal hyperostosis, or sclerosteosis. Infrequently, a Chiari malformation may also be described. We present the case of a patient with acquired Chiari malformation secondary to hyperostotic skull formation whose findings did not fit into any of the 4 usual conditions. We review the literature on generalized hyperostosis of the skull and discuss the appropriate treatment based on our analysis of the literature and the patient's imaging results.

Case Description: A 26-year-old woman presented with headaches, vomiting, and visual loss. Imaging revealed hyperostosis of the skull and an acquired Chiari I malformation. Intracranial pressure was markedly increased. She underwent a reduction craniotomy with subtemporal decompression and had good clinical improvement.

Conclusion: Chiari malformation in association with hyperostosis of the skull is an unusual finding. Our patient could not be classified into any of the 4 main hyperostotic conditions. Careful attention to imaging identified the hyperostosis and deflected treatment from the standard for Chiari I malformation, suboccipital decompression, which could have proved fatal. Instead, a reduction craniotomy with subtemporal decompression relieved the source of the increased ICP and of the downward tonsilar displacement.