Nandakumar Nagaraja, MD
Whether the cytotoxic edema (CE) exists surrounding the hematoma in patients with intracerebral hemorrhage is still a controversy and the clinical significance of CE in the perihematomal region is unknown. In a recent article by Li et al., 21 patients with primary ICH were prospectively evaluated with MRI at 24hrs, 3 days and 7 days for the presence and temporal pattern of CE.
Areas of increased DWI with corresponding reduced ADC value by more than 10% compared to mirror ROI were interpreted as CE. CE was seen on day 1 in 45% of patients, persisted till day 3 and significantly reversed by day 7. Presence of CE on day 1 was associated with higher NIHSS and larger perihematomal edema (PHE). Patients with CE had faster PHE growth within the first 24hours but had significantly attenuated PHE volume growth during the first week compared to those without CE.
The authors suggest that the presence of CE indicates secondary brain injury in patients with ICH and determines prognosis. Unfavorable outcome defined as mRS 4-6 at 90days was associated with larger PHE volume on day 3, and a trend was noticed in patients with CE on day 3 but not with baseline hematoma volume.
The authors state that the CE is a reversible step if the compensatory mechanisms such as ATP pump activity are still effective. The concept of reversal of CE is exciting. There are several reports of reversal of restricted diffusion after thrombolysis in acute ischemic stroke patients. However, whether it represents the same pathophysiological process in patients with ICH or if it is pseudonormalization of ADC remains to be determined.