Intraoperative ultrasonography in the surgical management of Chiari I malformation: A systematic review and meta-analysis of outcomes and applications

Chiari malformation type I (CM-I) is a neurological disorder characterized by cerebellar tonsillar herniation and is often associated with syringomyelia. Posterior fossa decompression (PFD) is the primary treatment, although the optimal extent of decompression remains a topic of debate. Intraoperative ultrasonography (IOUS) offers real-time visualization to support informed surgical decision-making. This study aimed to assess the effectiveness and safety of IOUS-guided surgery in CM-I. This systematic review followed PRISMA guidelines and searched the literature up to July 5, 2025. Studies that utilized IOUS and reported related outcomes were included. A random-effects meta-analysis was employed to pool proportions, and a meta-regression analysis was conducted to explore heterogeneity. Twenty-one non-randomized observational studies, including 1,576 patients, 54.4% of whom were female, were included. The pooled clinical improvement rate was 88% (95% CI: 81%–93%), and the syrinx improvement/resolution rate was 87% (95% CI: 77%–95%). The pooled reoperation rate was 6% (95% CI: 3%–9%), and the complication rate was 6% (95% CI: 3%–8%). Meta-regression revealed that longer disease duration, motor/sensory deficits, and duraplasty were associated with improved syrinx outcomes. IOUS-guided surgery in CM-I is linked to positive clinical and radiological improvements and low complication rates. IOUS can serve as a helpful tool for customizing decompression during CM-I surgery. Larger, prospective, multi-center studies are needed to confirm these findings.