Neuroimaging Features Of Post-traumatic Stress Disorder Following Motor Vehicle Accidents:A Cohort Study

Backgrouds and ObjectiveMotor vehicle accidents(MVA)not only do harm to victims’ physical health,but only damage their mental health.Some of vicims would develop mental illness following MVA,of which PTSD is the most common and harmful one.As a common traumatic event,quite a lot of vicims get injured every day.It’s becoming a big issue on how to identify victims with high risk for PTSD.In addition,MVA victims often suffer TBI of different severities,of which mTBI gets the highest prevelance.Most importantly,several symptoms overlaps exist between PTSD and mTBI,it’s hard for clinicians to distinguish the two conditions only by clinical symptoms.Our study was carried out to figure out the neuro-imaging features of PTSD acquired in 48 hours and 24 weeks apart from the accident,by recruiting MVA victims from emergency rooms from comprehensive hospitals.Further,our study tries to figure the possible relations between PTSD and mTBI by analyzing neuroimaging data.MethodsSubjects at baseline were categoried as PTSD group or trauma control group according to the clinical assessment with clinican administered PTSD scale(CAPS).This research could be splitted into two separate parts,focusing on different interests.The first part focused on gray matter and white matter features which would make victims more susceptible to PTSD and try to locate the brain structural injury in relation with the progression of PTSD.At baseline,29 PTSD subjects and 41 trauma control subjects with qualified structural T1 data were included in the final analysis.While 24 PTSD subjects and 37 trauma controls were qualified for the baseline DTI analysis.The cortex regions and white matter fibers specific for PTSD were found by comparing eigenvalue whold cortex wide,with Freesurfer and TBSS.Correlation analysis was performed on the eigenvalues extracted from the abnormal cortex and white matter fibers specific for PTSD and CAPS dimentional scores to see the prediction power of these eigenvalues.15 subjects with PTSD and 14 subjects without PTSD were scanned by structural T1 sequence for second time at 24 weeks apart from the accidents,while only 12 PTSD and 9 trauma control completed the follow-up DTI scan.Group differences in cortex and DTI eigenvalue changing were checked by protocol provided by longitudinal analysis protocol,which could give us some hints on how PTSD itself influence cortex and white matter microstructural integrity.The second part tries to figure out the relationship between PTSD and mTBI,two medical condition following MVA.By conducting four subgroup analysis((1)pure PTSD group vs.pure trauma control group;(2)pure mTBI groups vs.pure trauma control group;(3)PTSD subjects who met diagnosis of mTBI at baseline vs.PTSD subjects not met diagnosis of mTBI at baseline;(4)mTBI subjects who converted to PTSD vs.mTBI subjects who not converted to PTSD at follow ups),we try to figure out the correlation between PTSD and mTBI.ResultsThe first part found that volume of bilateral insula cortex and subgenual anteriror cingulate cortex were smaller in PTSD group than in trauma control group.These results could be corrected by FDR(P < 0.05).Value extracted from the abnormal cortex correlate significantly with CAPS scores.In addition,Volumes of CA3 and DG were smaller in PTSD group than in trauma control group at baseline,which indicated that deficient volume in CA3/DG would make subjects more vulnerable to develop PTSD.Voxelwise longitudinal analysis showed that no significant differences were observed with regards to cortical thickness changing rate.Further our result showed that lower FA value was observed in cingulum,corpus callosum,superior longitudinal fasciculus in PTSD group at baseline,FA vaule extracted from these regions correlated significantly with CAPS dimentional scores at follow ups.The second part showed that no thicker cortex were found in PTSD group in acute phase of MVA,while several areas with thicker gray matter were detected in mTBI group at acute phase of MVA.By conducting ROI analysis,we found decreased vmPFC volume at baseline in mTBI subjects who converted to PTSD was observed.Conclusion(1)abnormal gray/white matter structure within emotion regulation circuit would make subjects who just go into MVA more susceptible to PTSD;(2)PTSD and mTBI are two independent diseases that followed MVA.