Introduction: Mild Traumatic Brian Injury (mTBI) is a significant cause of disability globally and in New Zealand is estimated to occur 749 in 10000 person-years(1) . In the majority of mTBI cases conventional radiological investigations (CT or MRI) are normal and there is a gap in identifying microstructural changes at an axonal level that could help understand development of chronic symptoms.

Methods: The study population of 138 patients includes: 31 patients with full recovery following mTBI, a group of 42 patients who have not recovered after 6 months, a group of 26 with no TBI history who have been selected from the Chronic Pain Clinic, and a group of 41 normal controls. The participants have been matched on age, gender, injury severity (GCS, PTA: injury severity scores), education and ethnicity. Each patient completed neurocognitive testing and structural and diffusion-weighted MRI scans. Voxel based morphometry was used to investigate differences in grey matter volumes between the groups, as well as to investigate correlations with neurocognitive outcomes. Cortical thickness was also calculated. Tract based spatial statistics (TBSS) were used to investigate differences and correlation with neurocognitive outcomes between diffusion metrics (fractional anisotropy, mean diffusivity).

Results: We identified no statistically significant differences between the non-recovered group and the recovered group. Neither of these groups differed significantly from controls in terms of grey matter volume, cortical thickness, or in the diffusion metrics (Fractional anisotropy and mean diffusivity).

Conclusions: Our findings lack significance between PCS and non-PCS groups. There are mixed findings in the literature on this topic. Perhaps more advanced imaging and sophisticated methods such as HARDI acquisitions or diffusion kurtosis imaging maybe needed to identify differences between the groups

Patient Care: Newer diffusion techniques have the potential to provide diagnostic information and could help tailor patient care accordingly. These new developments can further improve understanding of the brains plasticity and potentially new strategies to either help identify those experiencing PCS or those at risk of transition to PCS after mTBI.

Learning Objectives: By the conclusion of this session, participants should be able to; 1) Describe the differences in the definition of mTBI and its impact on research heterogeneity 2) Describe pathophysiology of mTBI 3) Describe advanced MRI techniques used in mTBI

References: (1)Feigin V et al, Incidence of traumatic brain injury in New Zealand a population based study. Lancet Neurol 2013;12:53-64