Neuroimaging in pediatric traumatic brain injury: current and future predictors of functional outcome

Abstract

Although neuroimaging has long played a role in the acute management of pediatric traumatic brain injury (TBI), until recently, its use as a tool for understanding and predicting long-term brain-behavior relationships after TBI has been limited by the relatively poor sensitivity of routine clinical imaging for detecting diffuse axonal injury (DAI). Newer magnetic resonance-based imaging techniques demonstrate improved sensitivity to DAI. Early research suggests that these techniques hold promise for identifying imaging predictors and correlates of chronic function, both globally and within specific neuropsychological domains. In this review, we describe the principles of new, advanced imaging techniques including diffusion weighted and diffusion tensor imaging, susceptibility weighted imaging, and (1)H-magnetic resonance spectroscopy. In addition, we summarize current research demonstrating their early success in establishing relationships between imaging measures and functional outcomes after TBI. With the ongoing research, these imaging techniques may allow earlier identification of possible chronic sequelae of tissue injury for each child with TBI, thereby facilitating efficacy and efficiency in delivering successful rehabilitation services.

Fig. 1

Axial MR images from a 16-year-old female 8 days after severe TBI. T1- and T2-weighted images demonstrate bilateral hemorrhagic frontal lobe contusions. DWI and derived ADC image demonstrate vasogenic edema (hypointense on DWI and hyperintense on ADC map) in the region of the contusions as well as cytotoxic edema (hyperintense on DWI and hypointense on ADC map). Cytotoxic edema suggests ischemic and/or hypoxic injury extending beyond the region of injury identified on T1- and T2-weighted sequences.

Fig. 2

MRI images from a 16-year-old female 3 months after severe TBI. (A) T2-weighted axial MR image shows bilateral, left dominant hippocampal injury with significant tissue loss. No focal hemorrhages seen within the temporal lobes. Mild signal increase within the brainstem indicating Wallerian degeneration. SWI demonstrates many focal, petechial T2^★-hypointense hemorrhages, representing DAI. (B) T2-weighted image shows faintly demarcated injury of the periventricular white matter and splenium of the corpus callosum. SWI demonstrates extensive hemorrhagic injury of the corpus callosum.

Fig. 3

MR and MR Spectroscopy images and data from a twelve-year-old male with severe TBI at age 5 years. (A) Axial FLAIR images demonstrating hyperintensities in bilateral periatrial white matter and superior anterior left frontal lobe. (B) N-acetyl-aspartate (NAA) map, obtained using a multislice spin-echo sequence with two-dimensional phase-encoding and outer-volume saturation pulses for lipid suppression, from the axial level demonstrated in the adjacent T1-weighted image; decreased intensity in the NAA map is noted in the left hemisphere, consistent asymmetric localization of DAI in FLAIR images. (C) Spectra derived from voxels in right (thin arrow) and left (thick arrow) hemipshere gray matter; decreased concentration of NAA, choline (Cho), and creatine (Cr) are noted in the left hemisphere compared with the right hemipshere.