Foramen Magnum Decompression in Craniosynostosis

Foramen magnum decompression is performed in some selected cases of craniosynostosis associated with Chiari Deformation Type I (CMI). This condition may be seen in syndromic and multisutural craniosynostosis being rare in single monosutural forms. There is a prevalent involvement of the lambdoid suture that is predictive of tonsillar herniation (TH). The pathophysiology of CMI involves a reduced posterior fossa volume, blocking of the venous outflow through the jugular foramen and changes in and around the foramen magnum, among other. Hydrocephalus is frequently associated with craniofaciostenosis and is usually multifactorial. Chiari I malformation is asymptomatic in many cases, in which the diagnosis is established by MRI. There is a wide range regarding the number of patients that become symptomatic. The incidence may reach 82% in Pfeiffer’s, 70% in Crouzon’s, and 100% in Kleeblattschädel’s, being very low in Apert and Sahtre-Schotzen syndromes. Occipital decompression with in-continuity enlargement of the posterior FM region is widely accepted and posterior vault distraction is also an option to address these conditions. Foramen magnum decompression alone has a limited role in the treatment of CMI in the setting of craniosynostosis and is preferable in situations, like syringomyelia, or when the correction of the supratentorial deformity and treatment of hydrocephalus were ineffective. The authors stress that individuals with syndromic craniosynostosis especially Crouzon-Pfeiffer should undergo preoperative CT or MRI venography to identify venous anomalies and avoid excessive bleeding and catastrophic results during posterior fossa decompression.