Electromyographic analysis of the suprahyoid muscles in infants based on the lingual fraenulum attachment during breastfeeding

Introduction Muscle electrical activity analysis can aid in the identification of oral motor dysfunctions such as those resulting from altered lingual fraenulum which, in turn, impairs feeding. We aimed to analyse suprahyoid muscle electrical activity of infants based on lingual fraenulum attachment to the sublingual (ventral) aspect of the tongue and floor of the mouth, during breastfeeding. Methods and Results We studied full-term infants of both genders aged between 1–4 months. Lingual fraenulum evaluation and surface suprahyoid muscle electromyography was performed during breastfeeding. Mean muscle activities were recorded in microvolts and converted into percent values (normalisation) of the reference value. Associations between root mean square and independent variables were tested by one-way analysis of variance and Student’s t-test with significance level of 5% and test power of 95%. We evaluated 235 infants while breastfeeding. The lingual fraenulum was commonly attached to the tongue’s ventral aspect between middle third and apex, and on the mouth floor visible from the lower alveolar ridge. Lower muscle activity was observed with lingual fraenulum attached to apex/lower alveolar ridge, followed by attachment to middle third/lower alveolar ridge, and between middle third and apex/lower alveolar ridge. Highest activity observed in Infants with attachment to middle third/sublingual caruncles, had a thin lingual fraenulum, performed several sucks followed by short pauses, showed coordination between swallowing, sucking, and breathing, did not “bite” nipple, and showed no tongue snapping nor stress. Conclusion Greater suprahyoid muscle activity during breastfeeding was observed with lingual fraenulum attachment to middle third of the tongue/sublingual caruncles, showed coordination between swallowing, sucking, and breathing. Surface electromyography is effective in diagnosing lingual fraenulum alterations, whose attachment point raises doubts as restriction of tongue mobility. This technique identifies possible oral motor dysfunctions, enables direct therapeutic interventions and early intervention, and prevents feeding and communication alterations.

Breastfeeding is considered essential for the promotion and protection of 3 children's health due to the nutritional and immunological properties of breast 4 milk, which protect them from respiratory diseases, infectious [1], and diarrhea [2].

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In addition, breastfeeding is considered important for the adequate development of 6 the stomatognathic system, because the removal of breast milk involves intense 7 muscle activity [3].

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During sucking in the womb, the suprahyoid muscles (digastric, mylohyoid, 9 geniohyoid, and stylohyoid) that effectively participate in the movement and 10 stabilisation of the mandible and tongue movement [4,5].

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The correct movement of the tongue during breastfeeding promotes an adequate 12 fit between the infant's mouth and the mother's nipple, compressing the nipple 13 against the hard palate and favouring the removal of the milk due to the vacuum 14 created in the oral cavity by the raising and lowering movement of the tongue [6-9].

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In the inferior surface of the tongue is located the lingual fraenulum and is 16 considered a median fold of tunica mucosa that connects the tongue to the floor of 17 the mouth and allows the free movement of its anterior part [10].

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After apoptosis, the remaining residual embryonic tissue (lingual fraenulum) may 19 limit tongue movements to varying degrees. This congenital oral anomaly is referred 20 to as ankyloglossia [11] and may cause a reduced mouth opening, imprecision and 21 restriction of isolated tongue movements, heart-shaped tip or downward protrusion

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[12], tongue resting in the floor of the mouth, and difficulties in sucking, chewing,

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After attaching the electrodes to the skin of the infant, the clamp sensors were 160 placed following the same order as the electrode attachment [17,29]. After 161 completing this procedure, the configuration, channel enablement in the software,

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and subsequent calibration were performed. The three unused channels were 163 disabled.

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The mother was seated comfortably in a chair with back support with her baby 165 on her lap. Before the evaluation, she received the necessary guidelines on the 166 clinical examination, evaluation of nutritive sucking, and electromyographic 167 examination.

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The mother received instructions about her positioning: seated with feet on the 169 ground; and about the positioning of the infant: supported and aligned with the 170 head and the spine straight, belly facing the body of the mother, face towards the 171 mother's breast, and mouth towards the areola and nipple to catch the breast.

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Subsequently, the activity of the suprahyoid muscles during breastfeeding was 173 recorded for 3 minutes (Fig 1).
174 fraenulum. After scheduling a consultation with the paediatrician, the infant was 180 referred to the paediatric dentistry service for assessment and definition of conduct.

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The data collected in this study were archived in a confidential location and will 182 be incinerated after 5 years. electromyographic trace whose unit is expressed in microvolts (μV).

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In order to select the best signals, the best configurations that presented the least

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For the statistical analysis associating the dependant variable of muscular 259 electrical activity value with the other variables, were excluded the data referring to

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Considering the statistically significant differences found in the association 299 between the groups, as described in Table 3, the electrical activity of the muscle 312   (Table 6).
333 Table 6 -Comparison of the electrical activity in the suprahyoid muscles between groups 1 and 5 334 expressed in RMS of the infants according to thickness, lingual fraenulum attachment to the 335 tongue and floor of the mouth, and nutritive sucking pattern.