Oral Communication

Volumetric alterations following severe traumatic brain injury even in the absence of focal lesions

Dr Alexis RUETa, Dr Françoise JOYEUXb, Dr Corinne JOKICb, Dr Shailendra SEGOBINc, Prof Béatrice DESGRANGESc, Prof Francis EUSTACHEc, Dr Anne-Lise PITELc

a Service de médecin physique et de réadaptation, CHU de Caen, France, b Service de médecin physique et de réadaptation, CH Louis LACAINE Donation LEROQUAIS, Aunay sur Odon, France, c Inserm, EPHE, Université de Caen/Basse-Normandie, Unité U1077, GIP Cyceron, CHU de Caen, France

Introduction: Traumatic brain injury (TBI) frequently leads to cognitive and behavioural disorders interfering with everyday life and work, despite the absence of focal lesions on clinical images acquired after injury.The aim of this study is to use magnetic resonance imaging (MRI) to examine whether volumetric alterations measured voxel by voxel in the whole brain could explain these cognitive and behavioural disorders.

Methods: Eight adults with severe TBI (GCS≤8) but without focal lesions on the CT scan were included. Patients had normal intellectual abilities (PM38) but abnormal behaviour (Lhermitte’s scale). These 8 patients and 17 age-matched controls performed an episodic memory task (RL-RI-16 items) as well as classical and ecological executive tasks. All participants also underwent a volumetric T1-weighted MRI at 1.5T. Grey and white matter volumes were compared between patients and controls using the Voxel Based Morphometry (VBM5) toolbox in the Statistical Parametric Mapping (SPM) software.

Results: Patients exhibited abnormal results on both the episodic memory and executive tasks. Regarding brain volume, between-group comparisons (p<0.001, uncorrected for multiple comparisons, k=200) showed significant gray matter atrophy in the cerebellum, thalami, caudate nuclei and in the right parahippocampal gyrus in patients compared with controls. White matter atrophy was found in the corpus callosum, corona radiata, fornix, midbrain and pons. The cerebral cortex was relatively spared, even in the frontal regions.

Discussion: Despite the absence of cerebral brain lesions on CT scans, TBI patients with behavioral disorders show episodic memory disorders and executive dysfunctions associated with gray and white matter atrophy in subcortical and cerebellar regions. Alterations of nodes and connections of the frontal-subcortical circuits (but not systematically of the frontal cortex) following severe TBI may thus explain subsequent behavioural dysexecutive disorders.

Keywords : Traumatic Brain Injury; Magnetic Resonance Imaging; Cognition Disorders/psychology