Oropharyngeal Lateral Wall Collapse on Drug-Induced Sleep Endoscopy as a Predictor of Hypoglossal Nerve Stimulation Response in Obstructive Sleep Apnoea—A Systematic Review

Background/Objectives: Hypoglossal nerve stimulation (HNS) is an established treatment for moderate-to-severe obstructive sleep apnoea (OSA) in patients intolerant of continuous positive airway pressure. Pre-operative drug-induced sleep endoscopy (DISE) is mandatory for HNS candidacy assessment, with complete concentric velopharyngeal collapse representing the only formally accepted contraindication. The prognostic significance of oropharyngeal lateral wall (OLW) collapse remains contested, with conflicting evidence and no consensus on its role in patient selection. We sought to systematically evaluate whether OLW collapse on pre-operative DISE predicts surgical response to HNS in adults with OSA. Methods: A systematic review was conducted in accordance with PRISMA 2020 guidelines (PROSPERO: CRD420261347436). MEDLINE, EMBASE, and Cochrane CENTRAL were searched in March 2026 with no date restrictions. Risk of bias was assessed using the QUIPS tool. Data were synthesised narratively due to heterogeneity in DISE protocols and outcome definitions. Results: Eight studies comprising 1051 patients were included. Complete OLW collapse was associated with significantly lower HNS response rates in four of six studies directly testing this association (57.8–66.7% versus 74.2–84.8%; p = 0.024–0.042). On multivariate analysis in the largest study (n = 343), the association was attenuated to non-significance (OR 0.57, 95% CI 0.26–1.22), with BMI effect modification observed. One study reported a null finding and one paradoxically identified partial rather than complete OLW collapse as the failure-associated pattern (p = 0.04). All studies were rated as having a moderate or high risk of bias. Conclusions: Complete OLW collapse was associated with poorer HNS outcomes in several studies, but attenuation on multivariate analysis precludes its designation as a formal contraindication. Prospective validation and standardised DISE reporting are required before OLW collapse can inform HNS candidacy criteria.