Background: Tongue motion patterns (TMP) can influence the outcome of upper airway stimulation (UAS) in the treatment of obstructive sleep apnea (OSA). As a postoperative control the cuff position of the stimulation lead is monitored via X‑ray imaging. A multidimensional X‑ray assessment system was established and the association between these positional assessments and TMP was investigated 1 year after implantation.
Material and methods: The study on TMP and the X‑ray assessments were carried out at a German ear nose and throat clinic as an implantation center. The TMPs were assessed under bipolar electrode configuration and were categorized according to the currently available literature as right-sided protrusion (RP), left-sided protrusion (LP), bilateral protrusion (BP) and mixed activation (MA). The X‑ray assessment was carried out in five dimensions: the position relative to the mandible and hyoid, cuff steepness in the lateral view of the neck, the cuff position based on the single electrode and the lead connection to the cuff in the anterior-posterior view. The analyses were performed by three raters with different medical backgrounds and knowledge regarding TMP.
Results: In approximately 60% of the patients the apnea-hypopnea index was reduced to below 15/h, 1 year after implantation. The most common TMPs were RP and BP (82.9%). The interrater variability of the X‑ray assessment was good except for one category. Furthermore, no relevant associations were found apart from the correlation between a favorable TMP and the cuff position with respect to the lateral position of the stimulation cable.
Conclusion: Despite good interrater variability and convenient usage of the suggested X‑ray assessment system, this approach did not enable the identification of any associations, by which a TM and therefore a possible straightforward or complicated treatment pathway could be predicted. Attention should possibly be paid to a rotation of the cuff during implantation with a lateral position of the stimulation lead.
Keywords: Hypoglossus nerve stimulation; Interrater variability; PAP failure; Rating system; Tongue protrusion.