Traumatic Brain Injury Severity in a Network Perspective: A Diffusion MRI Based Connectome Study

Reut Raizman,Ido Tavor,Galia Tsarfaty,Lucian Tatsa-Laur,Chen Hoffmann,Sagi Harnof,Mark Weiser,Eyal Fruchter,Anat Biegon,Abigail Livny

doi:10.1038/s41598-020-65948-4

Abstract

Traumatic brain injury (TBI) is often characterized by alterations in brain connectivity. We explored connectivity alterations from a network perspective, using graph theory, and examined whether injury severity affected structural connectivity and modulated the association between brain connectivity and cognitive deficits post-TBI. We performed diffusion imaging network analysis on chronic TBI patients, with different injury severities and healthy subjects. From both global and local perspectives, we found an effect of injury severity on network strength. In addition, regions which were considered as hubs differed between groups. Further exploration of graph measures in the determined hub regions showed that efficiency of six regions differed between groups. An association between reduced efficiency in the precuneus and nonverbal abstract reasoning deficits (calculated using actual pre-injury scores) was found in the controls but was lost in TBI patients. Our results suggest that disconnection of network hubs led to a less efficient network, which in turn may have contributed to the cognitive impairments manifested in TBI patients. We conclude that injury severity modulates the disruption of network organization, reflecting a “dose response” relationship and emphasize the role of efficiency as an important diagnostic tool to detect subtle brain injury specifically in mild TBI patients.

Highlights

Traumatic brain injury (TBI) produces disconnection in large-scale brain networks
Our study examined the injury severity effect on structural networks connectivity post-TBI, and the association between structural connectivity and cognitive deficits in chronic TBI patients across all TBI severities
Our findings provide initial evidence that injury severity modulates the network organization, which in turn could be responsible for the observed cognitive changes in non-verbal abstract reasoning

Summary

Introduction

Traumatic brain injury (TBI) produces disconnection in large-scale brain networks. One of the most common pathologies associated with TBI is diffuse axonal injury (DAI), which is defined as damage to white matter connections[1]. Fargholm et al showed that graph theory properties such as betweenness and eigenvector centralities were significantly associated with information processing speed, executive function and associative memory in TBI patients[22] Both Caeyenberghs et al and Kim et al found that reduced global network efficiency corresponded with reduced performance in executive functions in TBI patients[20,23]. These previous studies examined only patients with moderate to severe TBI and did not include a group of patients with mild brain injury. The effects of injury severity on white matter connectivity and its association with cognition may further our understanding of TBI outcome

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