97 Distribution of Microglia (MG) in the Immature Brain with Isolated Germinal Matrix/Intraventricular Haemorrhage (GMH/IVH): A Combined Mri and Histological Approach

Background: GMH/IVH remains a prevalent form of injury to immature brain. In the absence of overt complications, haemorrhage may result in mild ventriculomegaly and poor developmental outcome. The imaging appearances are suggestive of periventicular injury with subsequent tissue atrophy. Although essential for normal brain development, presence of resident MG may exacerbate the injury. We have shown increased activated MG in normally appearing PVWM compared with less susceptible regions. A rabbit model of GMH/IVH demonstrated an increase in activated MG in the adjacent PVWM, which may cause or exacerbate WM injury. Aim: To use post mortem (PM) brain MRI and immunohistochemistry to investigate MG distributions in the immature brain in the presence of GMH/IVH and to compare to controls with normally appearing brain. Methods: Preterm (< 30 wk GA) PM cases were recruited with parental consent and ethics approval. Images were acquired at 3T with T1 and T2 weighted sequences. Iba1 and CD45 MG were counted in the anterior and posterior PVWM areas, centrum semiovale, germinal matrix (GM), subplate and cortex. Results: 6 brains showed isolated GMH/IVH and 6 showed normal appearances. Total number of MG in the GM (Iba1=14.21±1.39 p< 0.05; CD45=11±4.70) and PVWM (Iba1=12.30±0.91 p< 0.05; CD45=4.8±1.52) were higher than other regions in the GMH/IVH group. GMH/IVH PVWM MG numbers were higher than in the normal group (p=0.005). In the presence of IVH/GMH there was a marked increase in PVWM MG as seen in experimental models of IVH/GMH. These may be responsible for initiating or exacerbating an injurious process.