“Paediatric dysphagia” refers to any disturbance of the normal swallow sequence in infants and children, as difficulties in transporting a bolus from the oral cavity to the back of the tongue or moving food into the oesophagus, compromising safety and adequacy of nutritional intake^{[1][2][3][4][5][6]}.

Dsyphagia resulting from a neurological cause Paediatric swallowing disorders can have several causes, from prematurity and congenital anomalies to gastro-oesophageal reflux and infective or inflammatory pathologies of the upper digestive tract.

In neonates, the swallowing process is reflexive and involuntary. Later in infancy, the oral phase comes under voluntary control, while the pharyngeal phase and oesophageal phases remain involuntary. Swallowing difficulties can severely compromise pulmonary health and nutritional intake of paediatric patients.

Feeding and swallowing are developmental phenomena involving highly complex interactions that begin in embryologic and foetal periods and continue throughout infancy and early childhood^[7][8].

Videofluoroscopic Swallow Study

(VFSS) is a radiographic procedure that provides a dynamic view of the swallowing process and is frequently considered to be definitive evaluation for objective assessment of dysphagia in paediatric patients.

Pre- and post-natal development of swallowing mechanisms Through understanding of the development of feeding and swallowing skills, it is possible to shed light on how and why infants may demonstrate signs of oropharyngeal dysphagia. During embryologic life, between the 4th and the 7th weeks of gestation, many processes relevant to swallowing development take place. After the incorporation of the endoderm of the yolk sac into the embryo to form the primordial gut and rupture G. Lo Re et al. 280 of pharyngeal membrane to form primitive choanae, separation of oesophagus and trachea from the primitive foregut is essential to avoid liquid aspiration during their passage through oesophagus 11. Thereafter, the foetal period (from the 9th week of gestation to birth) is characterised by continuous differentiation of tissues and organs 11 and by a dramatic development of swallowing, sucking and oral sensorimotor function; this latter depends from brainstem and cerebral system development and is the fundamental system for correct functioning of the former 5 12. Sensory cranial nerve input to the brain stem swallowing centre depends on the V, VII, IX and X cranial nerves while primary motor cranial nerve output is provided primarily by the V, VII, IX, X and XII nerves and by the cervical C1-C3 nerves 5 . Correct development of cranial nerves is mandatory for adequate swallowing. Myelinisation of the roots of some cranial nerves is seen during the 20th-24th weeks of gestation, and during the 35th-38th weeks the nervous system matures sufficiently to carry out integrative functions as nipple feeding 13. Moreover, other cerebral regions are implicated in sensory and motor system development such as the nucleus tractus solitarius, nucleus ambiguous, dorsal motor nucleus, hypoglossal nucleus and cerebral cortex 14. Foetal swallowing is important to regulate amniotic fluid volume and composition, as well as maturation of the foetal gastrointestinal tract and renal foetal system 5 15. Oral motor skills also develop within a system that changes during post-natal life both in structural growth and neurological control: the successful use of the suckle reflex masters suckling and its coordination with breathing, the child’s motor function (mostly involving his/her tongue) masters the stabilisation of the jaw 16 17. The swallowing anatomic components of infants are different from adult ones. In the infant, the oral cavity is smaller and teeth have not erupted. We can also typically find a smoother tongue and harder palate. The larynx and hyoid bone are higher in the neck to the oral cavity, while in adults the larynx goes down to a lower area in the neck. The epiglottis is almost attached to the soft palate so that the larynx is open to the nasopharynx 18. The proper integration of the respiratory and feeding functions is mandatory because during feeding the time left for safe air exchange is reduced, minute ventilation is decreased, exhalation is prolonged and inhalation shortened. Thus, proper maturation and practice of the above functions during the first years of life enhances oral motor patterns, and this latter influences feeding performance 16. Swallowing requires both voluntary and involuntary actions and can be summed up into four phases (oral, triggering of swallowing reflex, pharyngeal and oesophageal) that involve structures and muscles of the nose, mouth, throat, chest, abdomen and digestive tract 19. The oral phase consists of both preparatory and transit phases. During the preparatory phase, food and/or liquid are prepared in the oral cavity by suckling or mastications in order to form a bolus that, in the transit phase, is moved posteriorly through the oral cavity. During the pharyngeal phase, bolus is transported through the pharynx, and then through the cervical and thoracic oesophagus into the stomach during the oesophageal phase 11 20. In neonates, the swallowing process is reflexive and involuntary and each of the abovementioned phases may mature at different times and/or rates. Later in infancy, the oral phase is voluntary and triggering of the swallow reflex is generally an involuntary activity, but it can be commanded voluntarily, while the pharyngeal and oesophageal phases remain involuntary 6 11. A child affected by chronic dysphagia will likely show delayed progression of normal feeding skills, recurrent respiratory disease and, consequently, growth deficiency. Aspiration is one of the abnormalities that may be encountered as an anomaly in the development during post-natal life and consists of passage of ingested material, refluxed contents, or oral secretions through the vocal folds into the lower respiratory tract. Recurrent or chronic aspiration is a serious risk factor in the paediatric population, resulting in infection, chronic lung disease and even death. The physiological avoidance of aspiration depends not only on anatomical separation of respiratory and digestive tracts in embryologic life, but also on central neural processing. Fluids contacting the laryngeal mucosa evoke laryngeal chemoreflexes 21 resulting in many possible responses such as rapid swallowing, apnoea, laryngeal constriction, hypertension and bradycardia, or cough; as the infant matures the formers reflexes (rapid swallowing and apnoea) become less probable, while cough and laryngeal constriction become more prominent 22. However, sex-related differences have been demonstrated between early oral, tongue, pharyngeal and laryngeal motor activities: oral and upper airway skills emerge earlier in females and the latter (pharyngeal and laryngeal movements) are less rhythmic and complete in males throughout the second semester 23. Paediatric swallowing disorders: aetiology An altered swallow sequence may compromise safety, efficiency, or adequacy of nutritional intake. Because

Children with dysphagia or respiratory problems possibly due to dysphagia, should be seen first by an ear, nose, and throat surgeon or gastroenterologist to exclude structural disorders of the neck, mouth, pharynx, larynx, and oesophagus.

If a structural lesion is excluded and there are no obvious features of neurological disease further enquiry is needed.