Perioperative Segmentation of the Posterior Fossa and the Keel of Goodrich in Surgical Outcomes of Chiari Malformations

Background: Chiari I malformation (CM-I) is defined as the extension of brain tissue into the spinal cord. This study aimed to refine the methodology for the acquisition of 3-dimensional measurements of the posterior fossa and introduce occipital keel size as a new marker and its impact in patients with CM. Methods: In this retrospective study, all patients who underwent Chiari decompression surgery at Montefiore Medical Center from April 2012 to April 2022 were included. Perioperative clinical information was obtained in addition to maximal keel thickness (KT), foramen magnum area, and preoperative and postoperative posterior fossa volumes for each patient and age-matched controls. Volumetric measurements were obtained using artificial intelligence-based semiautomated segmentation. Results: A total of 107 patients with CM including 37 males, and 70 females were studied with a mean age of 26.56 ± 17.31 compared with 103 controls without CM. The comparison between the CM and the general population groups demonstrated a significantly increased keel size in Chiari patients. Keel size had a significant relationship with dysphagia, paresthesia, and intraoperative blood loss, while posterior volume change had a significant relationship with sex and early symptomatic improvement. The Foramen magnum area was related to tonsillar descent and more prominent in patients with spina bifida. Conclusions: The Keel of Goodrich is a new anatomical factor that should be taken into consideration when evaluating preoperative symptoms, and intraoperative complications in patients with CM-I. Volumetric analyses demonstrated that posterior fossa volume change had a significant impact on early symptom improvement in patients with Chiari, as did the choice of operative approach. The routine use of semiautomated segmentation of the posterior fossa may help stratify Chiari patients in the future and should be implemented in routine clinical care.