Abstract

BackgroundFunctional magnetic resonance imaging (fMRI) in neonates has been introduced as a non-invasive method for studying sensorimotor processing in the developing brain. However, previous neonatal studies have delivered conflicting results regarding localization, lateralization, and directionality of blood oxygenation level dependent (BOLD) responses in sensorimotor cortex (SMC). Amongst the confounding factors in interpreting neonatal fMRI studies include the use of standard adult MR-coils providing insufficient signal to noise, and liberal statistical thresholds, compromising clinical interpretation at the single subject level.Patients / methodsHere, we employed a custom-designed neonatal MR-coil adapted and optimized to the head size of a newborn in order to improve robustness, reliability and validity of neonatal sensorimotor fMRI.Thirteen preterm infants with a median gestational age of 26 weeks were scanned at term-corrected age using a prototype 8-channel neonatal head coil at 3T (Achieva, Philips, Best, NL). Sensorimotor stimulation was elicited by passive extension/flexion of the elbow at 1 Hz in a block design. Analysis of temporal signal to noise ratio (tSNR) was performed on the whole brain and the SMC, and was compared to data acquired with an ‘adult’ 8 channel head coil published previously. Task-evoked activation was determined by single-subject SPM8 analyses, thresholded at p < 0.05, whole-brain FWE-corrected.ResultsUsing a custom-designed neonatal MR-coil, we found significant positive BOLD responses in contralateral SMC after unilateral passive sensorimotor stimulation in all neonates (analyses restricted to artifact-free data sets = 8/13). Improved imaging characteristics of the neonatal MR-coil were evidenced by additional phantom and in vivo tSNR measurements: phantom studies revealed a 240% global increase in tSNR; in vivo studies revealed a 73% global and a 55% local (SMC) increase in tSNR, as compared to the ‘adult’ MR-coil.ConclusionsOur findings strengthen the importance of using optimized coil settings for neonatal fMRI, yielding robust and reproducible SMC activation at the single subject level. We conclude that functional lateralization of SMC activation, as found in children and adults, is already present in the newborn period.

Highlights

  • Previous studies have demonstrated that the development of subcortico-cortical connections is disrupted following preterm birth [1], in turn causing adverse neurodevelopmental outcomes across multiple cognitive domains [2,3,4,5,6]

  • Using a custom-designed neonatal MR-coil, we found significant positive blood oxygenation level dependent (BOLD) responses in contralateral sensorimotor cortex (SMC) after unilateral passive sensorimotor stimulation in all neonates

  • Improved imaging characteristics of the neonatal MR-coil were evidenced by additional phantom and in vivo tSNR measurements: phantom studies revealed a 240% global increase in tSNR; in vivo studies revealed a 73% global and a 55% local (SMC) increase in tSNR, as compared to the ‘adult’ MR-coil

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Summary

Introduction

Previous studies have demonstrated that the development of subcortico-cortical connections is disrupted following preterm birth [1], in turn causing adverse neurodevelopmental outcomes across multiple cognitive domains [2,3,4,5,6]. Methods that allow early prediction of adverse motor outcome have fundamental clinical impact Both cranial ultrasound (cUS) and magnetic resonance imaging (MRI) have value in predicting motor outcomes. MRI outperforms cUS in detecting subtle white matter injury at term-equivalent age (TEA) [10], with higher predictive value associated with detection of parenchymal lesions than abnormalities of delayed myelination [11]. Direct comparisons of the two methods in very low birth weight (VLBW) preterm infants revealed that MRI outperforms cUS in the specificity of predicting neuromotor outcomes tested until 18 months of corrected age [11]. Functional magnetic resonance imaging (fMRI) in neonates has been introduced as a noninvasive method for studying sensorimotor processing in the developing brain. Task-evoked activation was determined by single-subject SPM8 analyses, thresholded at p < 0.05, whole-brain FWE-corrected

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