Background Childhood obstructive sleep apnoea (OSA) is a prevalent disease, and reported to affect around 5% of primary school-aged children. It is also clinically important as it can lead to neurocognitive, metabolic and cardiovascular complications. The tongue plays an important role in maintaining patency of the oropharynx. Lingual frenulum, a connective tissue between the floor of the mouth and the underside of the tongue, can affect the tongue position, its elevation and movements. Short lingual frenulum has been reported to be a risk factor for OSA. How frenulum length and its mobility affects craniofacial development and morphology remains to be defined.
Objectives In this study we aimed to prospectively evaluate the lingual frenulum length by free tongue measurement and tongue mobility in children suspected to have OSA. We hypothesized that OSA children would have shorter lingual frenulum than their non-OSA counterparts. Moreover, we explored the relationship between frenulum length and craniofacial profile using cephalometry. We hypothesized that cephalometric measurements would be different in children with and without short frenulum.
Methods Prepubertal Chinese children aged 5–12 years old, suspected to have OSA were recruited. Anthropometric measurements including weight, height, and circumferences of waist, hip and neck were taken on the day of admission. The lingual frenulum was evaluated based on tongue mobility and free tongue length. Tongue mobility obtained by a digital calliper was defined by Mpal/Mmax, which are the maximal distances between incisors during full mouth opening (Mmax) and when the tongue tip touched the palatal papilla (Mpal). The free tongue length was measured from the insertion of the lingual frenulum to the tongue tip using Quick Tongue-tie Assessment Tool (QTT). Normal tongue mobility was defined as mobility ≥50%, and normal free tongue length was defined as ≥16 mm. Cephalometric analysis was performed to evaluate the craniofacial profile. OSA was defined as obstructive apnoea hypopnoea index (OAHI) ≥1/h from overnight polysomnography.
Results In this study, 86 subjects (mean age: 8.36 ± 1.69 years) were recruited, and 50 were diagnosed to have OSA (OAHI≥1/h). There was no significant difference in anthropometric measurements between OSA and non-OSA groups. The medians of the free tongue length in OSA and non-OSA groups were 20 and 24 mm (p=0.321), respectively. The mean tongue mobility was 0.583 (± 0.189) in OSA group, and 0.680 (± 0.152) in non-OSA group (p=0.010). Free tongue length was significantly correlated with most of the anthropometric variables including age, weight, height, BMI, waist, and hip circumferences, but did not correlate with any of the PSG variables. Tongue mobility was not correlated with any anthropometric variables, but inversely correlated with OAHI (r=-0.234, p=0.030). In multivariate logistic regression, tongue mobility was independently associated with the presence of OSA after adjusted for age and gender. Tongue mobility was correlated with the cranial base angle (Ba-S-N), which can affect the relative position of the mandible.
Conclusions Reduced tongue mobility is associated with OSA in prepubertal children. Furthermore, tongue mobility may be an important factor in driving mandibular development.
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