Significant Injury Of The Mammillothalamic Tract Without Injury Of The Corticospinal Tract After Aneurysmal Subarachnoid Hemorrhage

Object:Little is known about the pathophysiological mechanisms of white matter injury after aneurysmal subarachnoid hemorrhage(aSAH).The purpose of this study is to investigate whether mammillothalamic tract(MTT)or corticospinal tract(CST)is more affected by aneurysmal subarachnoid hemorrhage in the same patient with good outcome(Grade 5 on Glasgow Outcome Scale(GOS)at 3 months)using diffusion tensor imaging(DTI).Methods:Between June 2013 to September 2016,21 good outcome patients with aneurysmal subarachnoid hemorrhage and 21 sex and age matched normal healthy control participants were recruited.Diffusion tensor imaging was obtained at 8.92±2.4 weeks after onset.Moreover,reconstruction of the corticospinal tract and the mammillothalamic tract was completed using the diffusion tensor imaging studio software.Apparent diffusion coefficient(ADC)and fractional anisotropy(FA)values were measured.In addition,the motricity index(MI)and mini mental state examination scores(MMSE)were obtained.Results:1.There was no statistically significant difference detected in apparent diffusion coefficient(ADC)and fractional anisotropy(FA)values of the corticospinal tract(CST)between the patient and control groups(p>0.05).2.On the contrary,there was a statistically significant difference in apparent diffusion coefficient(ADC)and fractional anisotropy(FA)values of the mammillothalamic tract between the patient and control groups(p<0.05).3.Additionally,in the patient group,no correlation(p>0.05)was observed between motricity index(MI)scores and diffusion tensor imaging parameters(ADC and FA)of the corticospinal tract(CST).4.While the MMSE showed a positive correlation with fractional anisotropy(FA)values of the mammillothalamic tract(r=0.591,p=0.029)without correlation to apparent diffusion coefficient(ADC)values of the mammillothalamic tract(r=0.142,p=0.628).Conclusion:1.Patients with good outcomes(Grade 5 on Glasgow Outcome Scale at 3 months)after aneurysmal subarachnoid hemorrhage appeared to suffer an injury of the mammillothalamic tract without associated injury of the corticospinal tract compared with the control group.2.This injury showed a correlation with cognitive dysfunction.3.Although aneurysmal subarachnoid hemorrhage patients with good outcomes may not show motor deficits,they still may experience and complain about long-term cognitive dysfunction.4.In addition,these patients are often neglected by physicians and not completely treated because their outcome is satisfactory.Looking forward,we feel there is a big opportunity to improve the quality of cognitive recovery in these patients,and we hope that in the future researchers and clinicians will move toward developing more comprehensive rehabilitation strategies for cognitive dysfunction in these types of patients.