Prediction of developmental performance in preterm infants at two years of corrected age: Contribution of the neurological assessment at term age

Abstract

Background

The population of preterm infants is increasing and resources available for follow-up are limited. Early markers are needed to identify children who will show major as well as more subtle neurodevelopmental impairments. Such a challenge could be achieved with the Amiel-Tison Neurological Assessment at Term (ATNAT).

Aims

This study assesses the usefulness of the ATNAT in the prediction of developmental problems at two years of corrected age (CA) in infants born between 29 and 37 weeks of gestation.

Method

Inclusion criteria were: gestational age between 29^0/7 and 36^6/7 weeks inclusively, birth weight below 2500 g and minimal 24-hour stay in the Neonatal Intensive Care Unit of Sainte-Justine Hospital. A sample of 147 was prospectively recruited and assessed at two ages: at term with the ATNAT and at 24 months CA with Bayley Scales of Infant Development–II.

Results

No major impairment such as cerebral palsy and no neurosensory impairment were observed. Developmental delay defined by an index < 70 on the mental or psychomotor scale was reported respectively in 6.2% and 5.4% of the cohort. Significant differences in mental, psychomotor and behavioral performances were found according to neurological status. Neurological status was the only variable to enter the predictive model for psychomotor and behavioral indexes. Gender and neurological status remained in the predictive model for mental performance.

Conclusion

This study supports the inclusion of the ATNAT among the eligibility criteria for systematic neurodevelopmental surveillance as it allows early identification of infants at higher risk of low developmental performances at 24 months CA.

Introduction

Despite advances in perinatal medicine, prediction of the developmental outcome in infants at risk remains a challenge. The identification of valid early markers of neurodevelopmental disabilities becomes even more important as the population of infants surviving adverse perinatal events increases [1] and the financial and human resources insuring follow-up of these children are limited. Early markers should allow identification not only of infants with major handicaps including cerebral palsy (CP) and signficant intellectual/cognitive disability, but also those who will present more subtle dysfunctions leading to functional impairments and occurring in 50 to 70% of infants born preterm with an inverse birth weight (BW) gradient [2]. These high prevalence/low severity dysfunctions include visuomotor dysfunction, developmental coordination disorder, learning disabilities, borderline to low average IQ scores, attention-deficit hyperactivity disorder, specific neuropsychological deficits and behavioral problems.

The advent of new measures of brain structure and function has incontestably improved our ability to predict neurodevelopmental outcomes [3], [4]. However, their use in daily practice is significantly limited by their cost, their accessibility and the expertise they require. Clinical neurological assessment must therefore remain central to the neurodevelopmental follow-up and the early diagnosis process. Moreover, a clinical assessment that is short and easy to perform would be an asset in following up preterm infants especially with a gestational age (GA) between 29^0/7 to 36^6/7 weeks whose overrepresentation among the high-risk population prevents any systematic surveillance of the entire cohort [5]. The need for such surveillance has been reiterated in recent studies that demonstrated higher than expected short-term and long-term morbidities among these children [6], [7], [8], [9], [10], [11]. Valid early markers would allow to target infants who should be followed up because they are at higher risk of presenting developmental impairments requiring early intervention.

In light of this, the Amiel-Tison Neurological Assessment at Term (ATNAT) [12], [13], [14], [15] could be relevant. Recently revised [13], [14], [15], the ATNAT considers signs that depend on the integrity of the upper structures, such as axial tone and alertness, as well as cranial signs linked to the volume increase of the cerebral hemispheres. The signs depending on brainstem function, such as primitive reflexes and passive tone in limb flexor muscles, have been de-emphasized as they do not provide information during the neonatal period about the cerebral hemispheres and basal ganglia. Divided into six different sections, this assessment covers neurosensory aspects, growth parameters and cranial morphology, passive and active muscle tone, spontaneous motor activity and primary reflexes. The main goal of this study was to evaluate the usefulness of the ATNAT in the prediction of developmental problems at 2 years of age in a population of infants born with GA ranging from 29 to 36^6/7 weeks.