Comparison of suboccipital craniectomy versus suboccipital cranioplasty in foramen magnum decompression for adult Chiari malformation

OBJECTIVE Foramen magnum decompression (FMD) by suboccipital craniectomy, which aims to restore CSF flow and alleviate symptoms, is the conventional treatment for symptomatic Chiari malformation (CM). However, suboccipital cranioplasty is considered to maintain cervical alignment, prevent headaches, improve cosmetic outcomes, and provide protection against trauma. The aim of this study was to compare two surgical techniques, suboccipital craniectomy and suboccipital cranioplasty, to evaluate clinical outcomes, radiological results, and medical costs. METHODS This retrospective analysis included 64 patients (mean age 37.6 ± 12.7 years) who underwent FMD for CM at a single tertiary referral center from January 2003 to March 2024. Patients were divided into two groups according to whether they underwent suboccipital craniectomy or suboccipital cranioplasty. Clinical data, radiological findings, surgical time, estimated blood loss (EBL), and medical costs were analyzed and compared between the groups. RESULTS Both surgical techniques significantly improved preoperative symptoms, and no significant differences were observed in surgical time or EBL between the groups. Radiologically, the suboccipital craniectomy group demonstrated a greater increase in subarachnoid space (mean 215.3 ± 113.6 mm 2 ) compared with the suboccipital cranioplasty group (mean 141.4 ± 97.3 mm 2 , p = 0.008), although the reduction in syrinx size was similar for both groups. The suboccipital cranioplasty group incurred higher daily medical costs (mean $1568.4 ± $455.5) compared with the suboccipital craniectomy group (mean $887.1 ± $340.5, p < 0.001), primarily due to the additional expenses related to bony reconstruction materials such as plates and screws (mean $343.3 ± $81.6). CONCLUSIONS Suboccipital craniectomy and cranioplasty both effectively improve symptoms for patients with CM. However, suboccipital cranioplasty involves additional costs, which should be discussed in the shared decision-making process.