Abstract
As the development of the brain is unique and continuing process throughout the gestation and after birth, it is expected that there is also continuity of fetal and neonatal movements which are the best functional indicator of developmental processes of the brain. Understanding the relation between fetal and infant behavior and developmental processes of the brain in different periods of gestation may make achievable the distinction between normal and abnormal brain development. Epidemiological studies revealed that many neurologically impaired infants belong to low risk population, which means that they seemed to be developmentally normal as fetuses and as infants, while later childhood neurological disability was diagnosed. Which methods of neurological assessment are available for that purpose? Prenatally we have not many possibilities for neurological assessment, while postnatally the repertoire of diagnostic possibilities is increasing. Among the postnatally available methods for neurological assessment, the most important are: clinical neurological assessment, neuroimaging methods, assessment of general movements (GMs) and combinations. Postnatal neurological assessment is probably easier to perform than prenatal, by using a simple and suitable for everyday work screening clinical test with good reliability, specificity and sensitivity.
There is a possibility for the early and simple neurological assessment of the term and preterm newborns with the aim to detect associated risks and anticipate long-term outcome of the infant, and to establish a possible causative link between pregnancy course and neurodevelopmental outcome. The evaluation of infant's developmental optimality should be assessed in order to investigate whether the infant is neurologically normal or damaged. Neurological assessment at term by Amiel-Tison (ATNAT) is taking into account neurological maturation exploring so called lower subcortical system developing earlier from the reticular formation, vestibular nuclei and tectum, and upper cortical system developing from the corticospinal pathways.
Conventional acquisition neuroimaging techniques together with modern diffusion neuroimaging techniques can identify typical patterns of brain injury, even in the early course of the disease. However, even though highly suggestive, these patterns cannot be considered as pathognomonic. Nevertheless neuroimaging methods alone are not sufficient to predict the neurological outcome in neonates from highrisk population.
Prechtl stated that spontaneous motility, as the expression of spontaneous neural activity, is a marker of brain proper or disturbed function. The observation of unstimulated fetus or infant which is the result of spontaneous behavior without sensory stimulation is the best method to assess its central nervous system capacity. All endogenously generated movement patterns from un-stimulated central nervous system could be observed as early as from the 7-8 weeks of postmenstrual age, with developing a reach repertoire of movements within the next two or three weeks, continuing to be present for 5 to 6 months postnatally. This remarkable fact of the continuity of endogenously generated activity from prenatal to postnatal life is the great opportunity to find out those high-risk fetuses and infants in whom development of neurological impairment is emerging. The most important among those movements are GMs involving the whole body in a variable sequence of arm, leg, neck and trunk movements, with gradual beginning and the end. They wax and wane in intensity, force and speed being fluent and elegant with the impression of complexity and variability. Assessment of GMs in high-risk newborns has significantly higher predictive value for later neurological development than neurological examination. Kurjak and co-workers conducted a study by 4D ultrasound and confirmed earlier findings made by 2D ultrasonography, that there is behavioral pattern continuity from prenatal to postnatal life. Assessment of neonatal behavior is a better method for early detection of cerebral palsy than neurological examination alone.
Are we approaching the era when there will be applicable neurological test for fetus and assessment of neonate will be just the continuation? This is still not easy question to answer, because even postnatally there are several neurological methods of evaluation, while in utero we are dealing with more complicated situation and less mature brain. Could neonatal assessment of neurologically impaired fetuses bring some new insights into their prenatal neurological status is still unclear and to be investigated. New scoring system for prenatal neurological assessment of the fetus proposed by Kurjak et al will give some new possibilities to detect fetuses at high neurological risk, although it is obvious that dynamic and complicated process of functional CNS development is not easy to investigate.
The aim of this review is to present continuity of the functional central nervous system assessment from prenatal to postnatal life.
The Tenets of Teneurin: Conserved Mechanisms Regulate Diverse Developmental Processes in the Drosophila Nervous System
