Ultrasonographic Tongue Base Motion Does Not Correlate With Hypoglossal Nerve Stimulation Outcomes

Abstract

Objective To evaluate whether tongue base motion patterns, assessed by submental ultrasonography during unilateral hypoglossal nerve stimulation (HNS), are associated with treatment response in obstructive sleep apnea patients.

Methods This cross-sectional study included 64 patients with unilateral HNS. Standardized submental B-mode ultrasound was performed to assess tongue-base motion under awake stimulation. Two independent, blinded raters evaluated the magnitude of anterior tongue base movement in the axial and sagittal planes. Further, the symmetry of bilateral tongue protrusion and tongue shape was classified. The primary endpoint was the correlation between apnea-hypopnea (AHI) reduction and ultrasonographic findings.

Results Ultrasonographic assessment showed substantial to excellent agreement between the two raters. No significant correlation was found between AHI reduction and anterior tongue displacement in either the axial (Spearman's ρ = 0.20, p = 0.12) or sagittal plane (ρ = -0.08, p = 0.64). Clinically meaningful bilateral activation was present in 33% of patients but was not associated with treatment outcome (ρ = 0.03, p = 0.84). Neither tongue shape was predictive of AHI improvement (buckling p = 0.13 and trough sign p = 0.79). Tongue movement patterns were not associated with stimulation voltage..

Conclusion Ultrasonographic assessment of tongue base motion under HNS does not correlate with treatment response. Neither symmetry, magnitude, nor qualitative shape was associated with AHI reduction. These findings suggest that visible tongue motion may not reliably reflect functional improvement in the airway. Future research should define the role of ultrasound in HNS evaluation and optimization

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