The Research Of DTI On The Secondary Degeneration Of Substantial Nigra After Striatum Infarct

Objective : To investigate the characteristic changes of diffusion and secondary degeneration of substantial nigra and caudate nucleus after Striatum infarct and its potential significance for the recovery of neurological functions with diffusion tensor imaging (DTI)prospectively.Materials and Methods:11 patients with unilateral Striatum infarct underwent magnetic resonance imaging (MRI)examinations and evaluations with the National Institutes of Health Stroke Scale(NIHSS), the Barthel index (BI) at the first week (W1), the end of the fourth week (W4) and the twelfth week (W12) respectively. 11 age and gender matched health volunteers as controls underwent DTI only once. MRI scanning sequences included axial T1 weighted imaging(T1WI),T2 weighted imaging(T2WI),T2 fluid-attenuated inversion recovery(T2FLAIR) and DTI. Following management of DTI, the fractional anisotropy (FA) and averaged diffusivity coefficient (ADC) values of Striatum , caudate nucleus and substantial nigra were calculated based on FA map and ADC map. t -test was employed for the group comparison. The analysis of variance used for Intra-group comparison of DTI statistics and neurological functions scale at different time-point as well as application of Person Correlation Analysis Method to them. All calculations were performed using SPSS software version 13.0.Results:(1)MRI findings: Primary foci of 9 patients showed long intensity signal on T1WI and T2WI as well as different mass effect at the first MRI scanning. At the second and third time we found gradual change of softening focus in the center and gyrus atrophy around it .Meanwhile sulcus and fissures broadened .But there were no significant changes in the remaining two patients. A lamellar and high intensity signal on T2WI/T2FLAIR was obtained in ipsilateral substantial nigra area in 9 of 11 patients. (Two of these cases happened at the first MRI examination on the third day). On the contrast , the remaining two patients were not detected lamellar and high intensity signal on T2WI/T2FLAIR in ipsilateral substantial nigra area.(2)The FA value of striatum which underwent infarct, ipsilateral caudate nucleus and substantial nigra reduced gradually at the first week (W1), the end of the fourth week (W4) and the twelfth week (W12) respectively. (striatum which uanderwent infarct, FA value : W1 0.199±0.031; W4 0.155±0.044; W12 0.136±0.046; caudate nucleus FA value : W1 0.188±0.007; W4 0.175±0.005; W12 0.136±0.046; substantial nigra FA value : W1 0.497±0.057; W4 0.431±0.053; W12 0.417±0.058.). ADC value of the underwent striatum changed increasely. (W1 0.660±0.135; W4 1.013±0.301; W12 1.393±0.505). When it turned to ipsilateral substantial nigra, ADC value reduced slightly at the first and fourth week. There was no statistic significance between them. At the twelve week ADC come back to normal and it had significant statistic deference(P<0.05) with comparison of the first week but not with fourth. But there was no significant statistic deference among the three time measurement of caudate nucleus(P>0.05).(3)During our observation, the absolute value of percent reduction of striatum FA value had the negative correlation to the absolute value of percent reduction of synchronous NIHSS and BI (P<0.05). It is similar with substantial nigra but no significant statistic deference(P>0.05). These three kind value have no correlation about caudate nucleus (P>0.5).Conclusion: After a striatum infarct, the secondary high intensity signal on routine T₂WI/T₂FLAIR was obtained in ipsilateral substantial nigra area on the third day. But DTI sequence can detcct it earlier than T₂WI/T₂FLAIR and can quantify it with FA value and ADC value. In addition, the secondary degeneration of ipsilateral substantial nigra will get worse with the time and postpone the recovery of neurological functions.