Oral motor patterns in feeding

Biomechanical stages of tongue movement

Successful practise of the suckle reflex, even non-nutritive sucking, before it fades at four months of age, enables an infants to successfully initiate nutritive sucking (i.e., nipple feeding). This then propels oral-motor skill development to the most advanced skill, rotary chewing (Manno et al 2005).

Oral-motor skill development is integrally linked with increasingly complex tongue movements. In the typical pattern of development, the infant learns to stabilise their jaw as to work the tongue off a stable base so it moves (Manno et al 2005):

• Firstly in an anterior/posterior (in/out) pattern (i.e., suckling) to move liquids through a nipple. This requires very little stability of the jaw as the jaw and tongue move together.

• Secondly in a superior/inferior (up/down) pattern (i.e., sucking) to move liquids and pureed foods. This requires more stability of the jaw so the jaw so the tongue can move independent of the jaw.

• Lastly in a lateral (side to side) pattern to move chewable foods over the molar surfaces and back to the centre, splitting and separating the food until it is ground down enough and recollected to swallow. Again this movement relies on stability of the jaw so the tongue can move independently of the jaw.

 A failure to develop stability of the jaw means the tongue movement fails to develop efficiently beyond moving in and out in in an anterior-posterior direction (Manno et al 2005).

This TMJ stability is transmitted to the tongue by the floor of the mouth fascia. The floor of the mouth fascia attaches from inner arc of the mandible, spanning the floor of the mouth, to attach on to the underside of the tongue (lingual frenulum). From this stabilised position created from the floor of the mouth fascia, the tongue can move in a coordinated manner. The laxity in the floor of mouth fascia allows for a wide range of tongue movements before the fascia is brought under tension, potentially influencing the ‘end point’ in range of tongue motion. Ankyloglossia (‘tongue tie’) can perhaps be considered an imbalance of the fascial roles, where its provision of tongue stability impacts on tongue mobility. This has potential significance in some infants, where division of the lingual frenulum (to improve tongue mobility) has the potential to compromise resting tongue position and stability (Mills et al 2019).

Factors Influencing Oral-Motor Skills

Structural Alignment

In a forward head position the tongue and jaw muscles help stabilise a child’s neck. This depresses the jaw so food and liquid are often lost during meals compared to when the head is in a neutral position. Proper biomechanical alignment is associated with improved swallowing, feeding and speech functioning (Manno et al 2005).

Muscles of the neck function in respiration, swallowing and posture. These muscles learn to work together, but when life sustaining activities, such as breathing, become more difficult muscles will be recruited from other functions. For example, ineffective breathing patterns result in the recruitment of other muscles to help respiration impacting head alignment and swallowing. Therefore, less efficient or ‘compensatory’ motor patterns develop, which, when they persist, effect the development of oral-motor patterns (Manno et al 2005).

Sensory Motor Input

Integrated sensory information is essential for developing motor planning skills that incorporate both motor control and motor learning. Working in a coordinated way this sensory input, and the information derived from the motor responses to this sensory input, determines the feedback that lays the blueprint for oral motor and swallowing skill development (Manno et al 2005).

Muscle Tone & Oral-Motor Patterns

Low muscle tone in the facial muscles results in an open mouth posture. Because jaw stability allows the tongue to dissociate movement patterns within the mouth (refer ‘biomechanical satges of tongue movement’), this open lax jaw precludes dissociation resulting in an immature anterior/posterior pattern in which the tongue and jaw move together. Also, wide, gross, jaw excursions decrease the ability to manipulate food within the mouth. This can result in food falling out of the mouth and a failure to chew smaller pieces of food due to the inability to grade movement (Manno et al 2005).

A lack of fine motor control over the jaw, and a tongue stuck moving in an anterior/posterior pattern of movement, means the child can’t elicit the oral-motor patterns that would enable them to adequately chew foods. Such an oral motor pattern would require their lips and cheeks to work together to provide enough tension within the mouth to contain and provide enough negative pressure to begin the swallowing process (Manno et al 2005).

If the lips and cheek muscles become shortened through compensatory motor movements and/or lack of practice, they will not be able to attain full muscle length required for lip closure. Therefore, tonal and muscle imbalance of these structures can leave the lips in an open position (Manno et al 2005).

This can result in losing food anteriorly or the inability to contain the food while manipulating it. The resulting pattern appears as though the child is pushing food out the front of the mouth, such as the oral-motor pattern that is typical of many children with Down Syndrome (Manno et al 2005).

Medical Influence on Oral-Motor Patterns

The two most common medical issues that interfere with feeding are respiratory and gastrointestinal. Sensory inputs from the respiratory and gastrointestinal tracts directly influence oral motor patterns through the swallowing centre in the brainstem (Manno et al 2005).

Because the upper respiratory tracts use the same structures as the upper digestive tracts (i.e., back of the mouth, and throat), breathing is neurologically programmed to supersede feeding. Any respiratory illness that makes breathing more difficult will negatively impact feeding and swallowing. For example, a child with asthma whose rate of breathing is increased may drool and refuse to swallow because the increased respiratory rate does not allow enough time for swallowing between breaths (Manno et al 2005). 

Frequent nausea, fullness from constipation, delayed emptying, or discomfort from gastroesophageal reflux or other irritants reduce the child’s interest in eating as well as impacting the timing and degree of contraction of the muscle pattern required to complete the swallowing process. As a result, the child becomes more protective of the airway and mouth by, for example, pulling the tongue up or back to minimise entry into the mouth, and restrict tongue movement. These changes may result in the use of more immature tongue movement patterns, less efficient tongue transport, and increased residual after swallowing. This can result in a preference for purees and foods that do not require increased tongue manipulation (Manno et al 2005).

Oral muscles used in effective feeding patterns

 Labial elevator muscles: levator labii superior, levator anguli oris and risorius

When the child’s upper lip is in retraction, so they show their top teeth, there is tension throughout the face. In this position the child will not be able to use their upper lip to latch on, (i.e. to a nipple or spoon), or place the tongue behind the teeth to receive the food. When the labial elevator muscles are stretched downward throughout the entire muscle, the upper lip can become more active (Manno et al 2005).

Orbicularis oris (“the kissing muscle”)

 The orbicularis oris improves flexion of the lips for mouth closure and puckering. Active use of this muscle assists in food containment, straw drinking and closure to provide the negative pressure necessary for transporting food through the oral cavity and swallowing. Active closure of the lips is needed to attain a single bolus swallow as opposed to a sequential swallow (i.e., multiple swallows in a row on a single bolus). Sequential swallowing is typical in children who are not transitioning to higher textured foods or who transport their food to the back of the mouth to swallow. This existing oral-motor pattern may be functional (i.e., the child successfully gets the food into the oesophagus), however, prolonged practice with this type of pattern limits the child’s ability to advance to more mature oral-motor patterns (Manno et al 2005).

Lingual muscles

When a child presents with a midline pattern (i.e. the tongue moves anterior-posteriorly with little side to side motion) they will not be able to efficiently chew and swallow a variety of foods (refer ‘biomechanical stages of tongue movement’). Unable to move the food laterally to the molars to grind down the food in preparation for swallowing will lead to the child learning to swallow foods whole or partially chewed. If the tongue movements are not altered, the child will continue to practice this less efficient movement and will not be able to advance to higher textured foods (Manno et al 2005).

The use of pressure on the middle of the tongue or the lateral sides of the tongue can facilitate the intrinsic and extrinsic lingual muscles to widen, thin out, narrow, elongate and flatten. Pressure on the lateral borders of the tongue can thin out the muscle and the tongue will move to that side. Stimulation to the anterior part of the tongue will facilitate a tongue tip. This serves to facilitate movement, increase acceptance of tactile sensation and acceptance of implements in the mouth (Manno et al 2005).

The anatomy of Ankyloglossia (‘tongue tie’)

Ankyloglossia (‘tongue tie’) is diagnosed when the lingual frenulum is thought to restrict tongue mobility (Miller et al 2019).  

The lingual frenulum is not a discrete midline connective tissue band or cord in the floor of mouth. It is formed by a layer of fascia that inserts around the inner arc of the mandible, spanning the floor of the mouth, and then inserts on to the under surface of the tongue. Tongue movement creates tension in the floor of the mouth fascia, dynamically raising the fascia and the overlying oral mucosa into a midline fold, recognisable as the lingual frenulum (Miller et al 2019).

The height of fascial insertion is slightly elevated in the midline when compared with the height of attachment of the fascia either side of the midline, giving a more visually prominent anterior aspect of the frenulum.  It is thickest in the anterior floor of mouth and becomes thinner and more transparent as it continues posterolaterally toward the piriform fossae (Miller et al 2019).  

The genioglossus is suspended beneath the floor of mouth fascia by a vertical mid-sagittal sheet of connective tissue. The tissues forming this ‘suspension’ appear to be a layer of transparent connective tissue continuous with the myofascia surrounding the genioglossus (Miller et al 2019).

The range in lingual frenulum morphology is created by variability (on a spectrum) of a number of factors (Miller et al 2019):

• The height of midline attachments of the fascia both anteriorly to the mandible and posteriorly to the under surface of the tongue.

• The length between these attachments.

• The relative gliding of the layers forming the frenulum fold (mucosa, floor of the mouth fascia and the fascial layer suspending the genioglossus).

  References

  Manno C, Fox C, Eicher P & Kerwin M (2005). Early Oral-Motor Interventions for Pediatric Feeding Problems: What, When and How

  Mills N, Keough N, Geddes DT, Pransky SM, Mirjalili SA. (2019). Defining the anatomy of the neonatal lingual frenulum.