Abstract: Background: There have been no longitudinal studies of ADC values under different intracranial complications of neonatal purulent meningitis. Objective: To retrospectively summarize the cranial MR of neonatal purulent meningitis in different course of disease, and analyze the variation characteristics of ADC value in brain tissue with different course of disease and its relationship with myelination process under different intracranial complications. Design: A case-control study. Methods: Full-term neonates who had purulent meningitis and cranial MR were taken as the case group and divided into 4 case groups according to intracranial complications——case group 1 of cerebral parenchymal lesions (-) and hydrocephalus (-), case group 2 of cerebral parenchymal lesions (+) and hydrocephalus (-), case group 3 of cerebral parenchymal lesions (-) and hydrocephalus (+) and case group 4 of cerebral parenchymal lesions (+) and hydrocephalus (+) . According to the interval between onset time and MR, disease course was divided into 0-7 days, -28 days, -60 days and -120 days, which were named as group A to D respectively. According to the age at the time of taking MR, course A was divided into course A1 (0-14 days) and course A2 (-28 days), and course B was divided into course B1 (-28 days) and course B2 (-60 days), and 20 normal infants were included in each group as the control group. Main outcome measures: Trends of ADC value in brain parenchyma of patients with neonatal purulent meningitis evaluated by MR at the same age or course of disease. Results: Totally 173 cases of neonatal purulent meningitis met the inclusion criteria of the case group. The maximum age and course of this study was 120 days. Therefore, MR examinations in the case group were 302 times. The ADC values of 241 MR in course A~D were analyzed in different case groups. The ADC values of the control group and the case group decreased with the increase of age. In the comparison of results of different course of disease (with the same age), there was no statistical significance in the ADC values of cerebral cortex and deep white matter in different course of disease, except for part of the course of splenium of corpus callosum. During the course of 0-60 days, the ADC value of subcortical white matter in case 2 and 3 groups was significantly lower than that in control group, and the ADC value of subcortical white matter in case 3 group and part of the course of case 2 group was significantly lower than that in case 1 group. During the course of 61-120 days, the ADC values of subcortical white matter in case 2 and 3 groups were not significantly different from those in control group, while the ADC values of subcortical white matter (except parietal white matter) in case 1 group were significantly higher than those in control group. During the course of disease 0-30 days, the deep gray matter ADC value in case 1, 2 and 3 groups was significantly lower than that of the control group. During the course of disease 31-120 days, the deep gray matter ADC value in case 1, 2 and 3 groups was not significantly different from that of the control group. Conclusion: In patients with neonatal purulent meningitis, subcortical white matter showed decreased ADC values within 1-2 months of the course of disease, and normal or increased ADC values at 3-4 months of the course of the disease, which suggested that the process of myelination was affected. Deep gray matter showed decreased ADC values within 1 month, and normal ADC values at 2-4 months of the course of the disease. MR DWI quantitative ADC is helpful to evaluate the micro injury of neonatal meningitis without brain parenchymal structure injury.

Key words: Newborn, Purulent meningitis, Diffusion weighted imaging, Apparent diffusion coefficient