Susceptibility weighted imaging and its relationship to outcome after pediatric traumatic brain injury

Abstract

Introduction

Traumatic brain injury (TBI) sustained during childhood can cause difficulties in a wide range of physical, neurological, cognitive, social and functional domains. However, the ability of health professionals and researchers to accurately predict the outcome of pediatric TBI remains limited. The advent of advanced neuroimaging techniques shows some promise in improving outcome prediction, as they contribute to greater sensitivity in characterizing intracranial lesions underlying many cognitive and functional deficits. In this study, the relationship between lesions identified on susceptibility weighted imaging (SWI) and cognitive and functional outcomes was investigated following childhood TBI.

Method

Participants between 5 and 14 years of age with varying levels of TBI severity (mild, mild complicated, moderate, severe, n = 106) underwent susceptibility weighted scanning on average 1-month post-injury and completed an assessment of intellectual functioning, processing speed, and behavioral and adaptive skills 6-month post-injury.

Results

More severe TBI was generally associated with poorer intellectual functioning, greater behavioral problems and lower adaptive functioning. Number and volume of SWI lesions were significantly correlated with clinical outcome variables including Glasgow Coma Score (GCS), surgical intervention, length of hospital stay and length of intubation, as well as with intellectual functioning. Together, SWI and GCS accounted for a significant, though small, proportion of the variance in intellectual quotient (IQ).

Conclusions

SWI is a sensitive technique for detecting brain lesions at all TBI severity levels and shows promise in contributing to prediction of cognitive outcomes in the initial stages post-injury.

Introduction

Traumatic brain injury (TBI) sustained during childhood is a common cause of disruption to development and can cause physical, neurological, cognitive and social problems (Anderson et al., 2004). In the search for better assessment and management of childhood TBI, recent efforts have focused on lesion detection and description (Saatman et al., 2008). Computed tomography (CT) is the most commonly employed neuroimaging technique in acute TBI management despite conventional magnetic resonance imaging (MRI) providing greater sensitivity, better links to functional outcomes (Chastain et al., 2009; Haacke et al., 2011; Sigmund et al., 2007), and less risk of radiation exposure (Kuppermann, 2008; Suskauer and Huisman, 2009). Nonetheless, neither CT nor conventional MRI consistently contributes to outcome prediction after childhood TBI (Anderson et al., 2006). More advanced MRI methods, for example susceptibility weighted imaging (SWI), have the potential to offer increased sensitivity to detect and characterize lesions (Tong et al., 2003).

SWI is a high-resolution structural MRI technique that exploits the magnetic susceptibility differences between tissues by using a sequence that is sensitive to iron and blood products in the brain, making it particularly useful for detecting TBI-related hemorrhage (Haacke et al., 2004; Reichenbach et al., 1997; Tong et al., 2008). Studies in childhood TBI have reported its value in detecting lesions characteristic of axonal injury (Sigmund et al., 2007; Tong et al., 2004, 2003), however its association with clinical and functional outcomes remains unclear.

Significant correlations have been found between number and volume of SWI lesions, global clinical outcomes [e.g., Pediatric Cerebral Performance Category (PCPC), Fiser et al., 2000] and cognitive variables (e.g., intellectual function) in children (Babikian et al., 2005; Colbert et al., 2010; Tong et al., 2004). However, studies to date have often focused on children with severe TBI, leaving open the question of whether SWI findings can be extrapolated to less severe injuries (Cassidy et al., 2004). Previously, we demonstrated that SWI was more sensitive than CT or conventional MRI for lesion detection after TBI of all severity ranges (Beauchamp et al., 2011b). This study aimed to evaluate the relationship between SWI lesion number and volume and both clinical and cognitive/functional outcomes. Greater lesion number and size were expected to be associated with poorer outcomes, establishing the clinical utility of SWI as a prognostic indicator for outcome from childhood TBI.