Objectives
Accumulating experimental evidences suggest that acute spontaneous intracerebral hemorrhage (SICH) is surrounded by a zone of perihematomal brain edema. However, data coming from human studies based on the assessment of perihemorrhagic regional Apparent Diffusion Coefficient (rADC) changes by using Diffusion-Weighted Imaging (DWI) are still controversial. Thus, in this study we sought to quantify rADC values around SICH in order to clarify the effective presence of perilesional edema.
Patients and Methods
DWI was performed on a 1-Tesla Magnetic Resonance Imaging (MRI) unit equipped for isotropic DWI. Axial images covering the whole brain were obtained by single-shot echo-planar spin-echo sequences in 45 patients (22 male and 23 female; mean age = 64.1 ± 10.4) with supratentorial acute SICH at admission CT scans and having a Glasgow Coma Scale at entry ranging from 9 to 15. Mean hematoma volume was 18.3 ± 12.7 cm3. ADC maps were generated for each patient by using an imaging workstation. rADC values were measured in four different regions of interest (ROI) drawn freehand on the T2-weighted images at b 0 mm2/s on every section in which hematoma was visible and including: 1) the perihematomal hyperintense area; 2) 1 cm of normal appearing brain tissue surrounding the perilesional hyperintense rim; 3) an area mirrored the region including the clot and perihematomal hyperintense area placed in the contralateral hemisphere. rADC values within the hemorrhagic core were not evaluated due to the well-known presence of susceptibility artifacts. rADC levels were expressed in mm2/s. rADC values lower than 70 × 10−5 and higher than 80 × 10−5 mm2/s were considered as suggestive of cytotoxic and vasogenic edema, respectively. All DWI studies were obtained within 48 hours after symptom onset. Statistical analysis was performed by Mann-Whitney U test and Spearman rank correlation coefficient test.
Results
rADC mean values were higher in perihematomal hyperintense and in contralateral than in normal appearing areas (p < 0. 001). The analysis of absolute values revealed that rADC mean levels were increased in perihematomal hyperintense (111.6 ± 36.7 × 10−5), in normal appearing (93.1 ± 11.1 × 10−5) and in contralateral areas (105.9 ± 20.1 × 10−5). No definite correlations were observed between perihematomal rADC mean levels and hematoma volume.
Conclusions
rADC values reflecting vasogenic edema were found in perihematomal area and in normal appearing brain tissue located both ipsilaterally and contralaterally to hematoma, with less pronounced values in non-injured area located around the periclot T2 hyperintense rim. In addition, the edema formation in perilesional T2 high signal area seems to be independent from hematoma size. These findings suggest that acute SICH is associated to both local and global edematous brain responses and indicate that DWI with analysis of rADC values represents a powerful tool for the evaluation of early edema development occurring around an acute hemorrhagic focal lesion.