Osteopetrosis with Chiari I malformation: presentation and surgical management.

Osteopetrosis is a heterogeneous group of rare, inherited disorders of the skeleton that results in neurological manifestations due to restriction of growth of cranial foramina and calvarial thickening. A 25-year-old woman with a history of autosomal dominant osteopetrosis presented to the authors' institution with headache worsened by exertion and radiating from the occipital region forward with episodes of choking/coughing when eating and a loss of gag reflex on physical examination. On MR imaging, she was found to have severe posterior fossa calvarial thickening resulting in a small posterior fossa and tonsillar ectopia of 9 mm and compression and deformation of the brainstem. She underwent posterior fossa craniectomy, foramen magnum decompression, and partial C-1 laminectomy with external durotomy. The patient did well postoperatively with resolution of symptoms. This case describes a new neurological manifestation of autosomal dominant osteopetrosis. To the authors' knowledge, this report represents the first described case of extreme posterior fossa calvarial thickening from autosomal dominant osteopetrosis with associated Chiari I malformation (CM-I) requiring posterior fossa decompression and extradural decompression. Given previously published MR imaging data that demonstrate the association of osteopetrosis and CM may be more common than in this case alone, the authors discuss the need for further investigation of the incidence of CM-I in patients with autosomal dominant osteopetrosis. Additionally, they review osteopetrosis and other diagnoses of calvarial hyperostosis presenting as CM-I.