1. Introduction
1.1. The importance of speech pathologist neurodiagnosis
The need to carry out actions in the field of early intervention in newborns and infants is a need born of an ever-increasing number of "risk" children and the ongoing progress in neonatology and early rehabilitation, including early diagnosis and speech and language therapy interventions.
These actions are directed to patients with, among others, difficulties in oral food intake. Disturbances and other deeper problems often accompany feeding problems development. However, sometimes, they occur in isolation without being coupled with damage, constituting only the result of minor anatomical abnormalities, lowering the realization of the primitive neonatal oral reflex base or incorrect feeding position.
Feeding, swallowing and breathing are prototypical activities necessary for newborns and babies' survival and proper development. These activities cross in the upper respiratory tract and represent the most complex neuromuscular process in the human body. Their disorder is often the first sign of future ones of the neurological condition of the newborn [1].
One of the many causes of these difficulties is a disorder or immature reflex oral reactions, classified as primitive neonatal reactions (PNR). Primitive neonatal reflexes is a collective name given to a group of inborn, unconditioned reflex responses, spontaneous behaviours and reactions to endogenous or environmental stimuli [1, 2, 3, 4, 5, 6, 7, 8, 9, 10].
Research reports also use unconditional neonatal reactions and physiological reflex reactions. The author acknowledges the phrases: "oral reflex responses", "oral PNRs", "physiological reflex responses", and "unconditional responses" as synonymous. Described and standardized, they became the basis for assessing neurological status, including diagnosing feeding skills based on oral reflexes. There are various divisions of reflex reactions: defensive and facilitating food intake, endogenous, motor, sequential, antigravitational and rhythmic [11].
In recent years, manometric analyses of sucking and swallowing, video fluoroscopy, ultrasonography and flexible endoscopic testing have been introduced. Endoscopic swallowing testing contributed to understanding the importance of orderly and sequential development of food intake based on normative oral reflexes. The assessment of oral-sensorimotor functions of newborns and infants is included in the following scales:
-NOMAS Newborn Oral-Motor Assessment Scale (Palmer et al. from 1993),
-Systematic Assessment of the Newborn at the Breast (SAIB) (Association of Women's Health, Obstetric and Neonatal Nurses, 1990),
-Assessment of Breastfeeding (Tobin, 1996),
-Evaluation of Infant Feeding (Swigert, 1998),
-Schedule for Oral-Motor Assessment (SOMA from 2000),
-Sensory Motor Speech Evaluation Test (SMSE, Müller from 1991).
In Poland, one of the newest tools is the Breast Sucking Skills Assessment Protocol by M. Machoś, 2015 and Assessment of Orofacial Reflexes and Speech Development Skills by M. Machoś, 2011.
Oral reflex reactions can be divided into protective and defensive: the reflex reaction of regurgitation and the reflex reaction of biting, as well as those that enable and facilitate food intake: the rooting reflex and the reflex of sucking and swallowing [9].
In the diagnostics, other reflex reactions are additionally assessed: labial (mouth opening, lip protrusion), tongue protrusion (E. Stecko identifies licking and tongue thrusting), and mandibular reflex. These reflexes' maturity and synergistic effect, correlated with the proper respiratory tract and the correct anatomical structure of the oral cavity, enable food intake. Further evolution of reflexes and their maturation according to the calendar development enables the acquisition of new skills and improvement of the digestive functions of the oral apparatus as well as preparation for the complex process of phoneme articulation. PNR disruptions are reported to be the first signals of immaturity or future disorders related to the maturation of the structures of the CNS (central nervous system) [12, 13, 14, 15].
When a newborn or infant has disorders or lacks proper reflex oral reactions, preventing its food intake orally, therapeutic procedures are often introduced to stimulate, activate, and rebuild the reflex or eliminate pathological, undesirable oral behaviour. This action should be based on a reliable diagnosis conducted by a speech and language pathologist. Moreover, the selected stimulation should be adequate for each patient's developmental possibilities and needs individually [16, 17]. Only such a procedure can counteract oral pathologies, which are not subjected to stimulation - they become the cause of such problems as:
-difficult maturation of food skills following the food calendar (drinking from a cup, biting, chewing),
-pathologies in swallowing activities (dysphagic disorders),
-development of a non-normative way of breathing (respiratory dysfunction),
-dysfunctional, atypical development of the oral phase of swallowing (persistent infantile swallowing pattern, reverse type swallowing dysfunctions),
-disorders in the formation of the stomatognathic system (malocclusion),
-disorders of the prototypical acquisition of the articulation system (articulatory disorders: dyslalia, speech distortions including increased nasalization).
1.2. Development of reflexive oral responses in the prenatal period
All primary neonatal reflexes, including oral ones, develop during fetal life, and their development depends on genetic, pre- and perinatal determinants [12, 18, 19, 20].
The structures responsible for the reflex motor and physiological base begin to form and gradually mature at an early stage of embryogenesis. The development of the central nervous system begins around the thirteenth day of gestation: the brain and spinal cord buds are formed [21]. Around the fortieth day of gestation, cerebral vesicles are formed. In the seventh week, the coordination of the functions of some organs is noticeable.
Observation of fetal oral behaviour documented the early development of the swallowing reflex and oral-motor skills [22, 23]. This early-forming ability is of great importance for regulating the volume and composition of the amniotic fluid, recirculating substances dissolved in it, and for the maturation of the fetal digestive tract [22]. The first swallowing (pharyngeal) movements were observed between the tenth and fourteenth week of gestation [24, 25]. In 14.-15 weeks of gestation, the coordination of swallowing and expulsion of amniotic fluid also begins (further refinement of the movements needed for breathing, sucking and phonation). The swallowing process develops in most fetuses by the fifteenth week of gestation, and a developed, fixed reaction of this reflex is observed after 22-24 weeks of gestation [23].
The reflex of protruding the tongue beyond the lips develops by the twenty-first week of gestation, and the ability to create a hollow on the tongue - in the twenty-eighth week. Anterior-posterior (sucking) movements develop between the eighteenth and twenty-eighth week.
Sucking and swallowing at this stage of fetal life are usually preceded by oral-facial self-stimulation [23]. The formation of the oral area: the oral sinus, the separation of the nasal cavity from the oral cavity, and the formation of the primary and secondary palate occur between the fourth and twelfth week of gestation [26].
The formation of the lung buds and the bronchial tree is the sixth week of fetal life. The upper lip, mandibular and maxillary areas are sensitized in the tenth week. In the twelfth week, the cooperation of the muscles that will be needed after birth for breathing, phonation and sucking begins: chest movements, relaxation of the diaphragm and abdominal muscles [21], opening and closing of the mouth in response to touch, spontaneous movements of pulling up, lifting upper lip, which is the initial stage of labial reflexes and preparation for the sucking reflex [27]. From the 17th week, the baby can bulge and protrude the lips forward, and sucking movements of the lips with a precise drawing of the amniotic fluid are observed. During ultrasound research, particular oral movements are visible:
-sticking out the tongue, licking: forward movements of the tongue, crossing the lips - the tongue may come into contact with the fetal fingers, uterine wall, placenta or umbilical cord [28];
-"cupping": the crown of the tongue rises, the mediodorsal part of the tongue is lowered - this movement and its precision seem to be particularly important for food intake; it precedes swallowing [28];
-yawning.
At the end of the third month, the phonatory organ is well-developed - vocal cords, and the baby can produce sounds (cries). In the thirty-second week of gestation, the specific triad sucking - swallowing - breathing is fully formed and matured. A surfactant is necessary for normative, mature breathing after birth, produced in the child's lungs from the twenty-fourth week of fetal life. It lines the inside of the alveoli and regulates the surface tension, preventing them from collapsing and overstretching.
The reflex reaction of biting, lateral and vomiting - are present in the oral behaviour of the fetus from the twenty-sixth to the twenty-eighth week, the rooting reflex around 32-40 weeks, and the tongue protrusion reflex - from 38 weeks.
The rhythm of sucking and swallowing is formed at the thirty-second week of gestation. It does not change by the fortieth week when it achieves final stabilization [29], and the coordination of sucking and swallowing matures.
