According to the American Association of Neurological Surgeons, the prevalence of Chiari malformations (CMs) in the general population is slightly less than 1 in 1000 [1]. Chiari malformation type I (CM-I) is the most common Chiari malformation subtype - occurring in approximately 0.5–3.5 % of the general population and predominantly in females [2]. Standard of care for CM focuses on symptom relief and prevention of the progression of associated symptoms. However, outcomes vary widely among patients, and understanding predictive factors remains a challenge.

The most common surgical intervention in CM-1 is Chiari Decompression surgery, most often a posterior fossa decompression (PFD). The PFD can occur in conjunction with a duraplasty (PFDD). Although surgical intervention generally leads to positive outcomes for patients with CM, potential postoperative complications include pseudomeningocele, cerebrospinal fluid (CSF) leakage, and hydrocephalus [3]. A recent randomized control trial consisting of 162 patients with CM-I and syringomyelia found similar complication rates between PFD and PFDD, however, PFDD patients were less likely to undergo a second operation [4]. This stands in contrast to a 2018 study in which PFD with comparable radiologic and clinical outcomes was associated with fewer complications [5].

For patients undergoing CM-1 decompressive surgery, CSF flow, tonsillar descent, syringomyelia, and the posterior base-C2 line (pB-C2, also known as the Grabb-Oakes line) have been identified as individual surgical predictors of postoperative outcomes [6], [7], [8], [9]. Despite the relative widespread use of these metrics, their prognostic significance remains a topic of debate. This systematic review and meta-analysis seeks to investigate radiographic findings and interpret their impact on postoperative outcomes in patients with CM-1.