Supplementary Material for: Frailty Indices in Patients Undergoing Functional Neurosurgical Procedures: A Systematic Review

Introduction: Functional neurosurgery covers a wide array of neurological disorders with an equally vast array of treatment modalities, including neuromodulation, decompressive, & ablative therapies for disparate pathologies such as pain, neuromodulation, disconnection, and refractory epilepsy. One of the most common functional treatments is deep brain stimulation for movement disorders and select psychiatric diseases. Functional neurosurgery treats patients with reduced quality of life from pathological neuronal pathways. Optimal patient selection by preoperatively identifying high risk patients is critical for avoiding as many operative complications as possible, in addition to managing complications better once they occur. Frailty indices have demonstrated superior discrimination in predicting adverse postoperative outcomes across the spectrum of neurosurgical subspecialties when compared to increasing patient age. This systematic review describes multiple different frailty indices utilized by patients undergoing functional neurosurgery procedures.
Methods: A systematic review of literature was performed using PubMed. The Newcastle Ottawa Scale (NOS) was used to assess for risk of bias and studies with NOS > 6 were considered high quality. An initial search identified 541 articles through our search strategy and, after screening and review, five met criteria for inclusion The 5-factor modified frailty index (mFI-5) and Risk Analysis Index (RAI) were most frequently utilized (n = 5). One study utilized single-hospital databases in contrast to the nationwide databases utilized by the other four studies.
Results: RAI was found to have superior predictive ability as frailty metric when compared to the mFI-5. All five studies were considered high-quality based on the NOS. Frailty indices have demonstrated the ability to predict adverse outcomes in patients undergoing procedures from across the spectrum of neurosurgical subspecialties.
Conclusion: Our review identified articles that utilized frailty indices in predicting outcomes among patients undergoing functional neurosurgery procedures.