Intraoperative neuromonitoring in Chiari I malformation surgery: a systematic review and meta-analysis

Chiari Malformation Type I (CMI) is a prevalent neurosurgical condition characterized by the descent of cerebellar tonsils below the foramen magnum. Surgery, aimed at reducing symptomatology and syrinx size, presents risks, making intraoperative neuromonitoring (IONM) a potentially vital tool. Despite its widespread use in cervical spine surgery, the utility of IONM in CMI surgery remains controversial, with concerns over increased operative time, cost, restricted anesthetic techniques and tongue lacerations. This systematic review and meta-analysis followed the Cochrane Group standards and PRISMA framework. It encompassed an extensive search through PubMed, Embase, and Web of Science up to December 2023, focusing on clinical and surgical outcomes of IONM in CMI surgery. Primary outcomes included the use of various IONM techniques, complication rates, clinical improvement, reoperation, and mortality. The review, registered at PROSPERO (CRD42024498996), included both prospective and retrospective studies, with rigorous selection and data extraction processes. Statistical analysis was conducted using R software. The review included 16 studies, comprising 1358 patients. It revealed that IONM techniques predominantly involved somatosensory evoked potentials (SSEPs), followed by motor evoked potentials (MEPs) and Brainstem auditory evoked potentials (BAEPs). The estimated risk of complications with IONM was 6% (95% CI: 2-11%; I² = 89%), lower than previously reported rates without IONM. Notably, the clinical improvement rate post-surgery was high at 99% (95% CI: 98-100%; I² = 56%). The analysis also showed lower reoperation rates in surgeries with IONM compared to those without. Interestingly, no mortality was observed in the included studies. This systematic review and meta-analysis indicate that intraoperative neuromonitoring in Chiari I malformation surgery is associated with favorable clinical outcomes, including lower complication and reoperation rates, and high rates of clinical improvement.