Displacement of oropharyngeal structures during suction-swallowing cycles

Suction ability plays an important role in supporting oral nutrition and needs special care following neurological disorders and tumor-associated defects. However, the details of suction are still poorly understood. The present study evaluates displacement of orofacial structures during suction and deglutition based on manometric controlled MRI. Nine healthy subjects were scanned wearing an intraoral mouthpiece for water intake by suction and subsequent swallowing. Suction-swallowing cycles were identified by intraoral negative pressure. Midsagittal MRI slices (3 T; temporal resolution 0.53 s) were analyzed at rest, suction and pharyngeal swallowing. The mandibular displacement was measured as the distance between the anterior nasal spine and the inferior point of the mandible. Following areas were defined: subpalatal compartment (SCA), retrolingual (RLA), epipharyngeal (EPA) and mouth floor area (MFA). During rest, an average distance of 7 cm was observed between the mandibular measurement points. The measured SCA was 3.67 cm², the RLA 6.98 cm², the EPA 9.00 cm² and the MFA 15.21 cm² (average values). At the end of suction, the mandibular distance reduces (to 6.88 cm), the SCA increases significantly (to 5.96 cm²; p = 0.0002), the RLA decreases (to 6.45 cm²), the EPA increases (to 10.59 cm²) and the MFA decreases (to 15.02 cm²). During deglutition, the mandible lifted significantly (to 6.81 cm; p = 0.0276), the SCA reduced to zero, the RLA was not measurable, the EPA reduces significantly (to 3.01 cm²; p < 0.0001) and the MFA increases (to 16.36 cm²). According to these observations, a combined displacement of the tongue in an anteroposterior direction with active tongue dorsum—velum contact appears to be the predominant activity during suction and responsible for the expansion of the subpalatal area.