In this report, we described the sequential occurrence of eclampsia-associated PRES and RESLES in a young woman. To the best of our knowledge, this phenomenon has not been previously reported. The case presented special MRI findings wherein vasogenic edema (PRES) disappeared and cytotoxic edema (RESLES) developed because of reasons unknown. In retrospect, we speculate that the long-term intravenous mannitol treatment may have been a cause.
PRES and ATL have been described by McKinney et al., and have overlapping etiologies [5, 7]. The etiologies of RESLES may overlap with PRES and ATL, it also likely involves a component of endothelial injury and perhaps toxic demyelination [8, 9], which has been suggested as both a cause of PRES and ATL, based on histopathology. They also envisioned that RESLES is a variant of ATL (or a subtype), and endothelial injury may be a reason for the concomitant PRES- RESLES(MRES). As Mannitol can reduce brain edema, it may have ameliorated the injury, although in higher amounts it has been described to induce endothelial injury as well. However, we feel it is still imperfection in using the mechanism of endothelial injury alone to explain the case.
Previous studies of RESLES evaluated by diffusion tensor imaging (DTI) showed that the fractional anisotropy value for the lesion in SCC did not exhibit a significant decrease; this suggested that the lesions are located inside or beneath myelin . However, Dan et al. reported cases of neonatal RESLES ; this contradicts the myelin sheath theory because neonates exhibited the disease even though their myelin sheaths are not yet developed. Accordingly, we speculate that the pathological changes seen in RESLES actually occur in astrocytes and are not associated with myelin sheaths . This is also suggested by the study of Starkey et al. . Aquaporins (AQPs) are an evolutionary conserved family of membrane transporter proteins that regulate the flow of water and, in some cases, glycerol and other small molecules across cellular membranes . AQP4 is the most abundant water channel found in all brain structures in contact with the cerebral vascular compartment, participating in the water balance of the central nervous system . A high concentration of AQP4 is found in the end-feet of astrocytes in contact with all blood vessels, and the AQP4 distribution in astrocytes differs significantly within brain structures such as the hippocampus, brainstem, and, in particular, corpus callosum [14, 15]. Early hypothesis suggests that severe hypertension exceeds the autoregulatory limits of the cerebral vasculature and leads to breakthrough of the blood–brain barrier, fluid leakage, and vasogenic edema. Endothelial injury is now considered a more common pathway of injury for most PRES patients . Animal experiments showed that hyperosmotic stress induced by mannitol solution increased AQP4 expression in cultured rat astrocytes . Because AQP4 expression in astrocytes was shown to be induced by hyperosmotic mannitol solution, which is commonly used to reduce brain edema, it has been suggested that AQP4 plays an important role in the treatment of brain edema. Interestingly, many previous studies [17, 18] have also suggested a dual role for AQP4 in the edema process: deleterious during cytotoxic edema formation and beneficial during the angiogenic edema resolution phase. On the basis of all these findings, we believe that the vasogenic edema in PRES was reduced with mannitol treatment, which increased the hyperosmotic stress and opened the blood–brain barrier; meanwhile, upregulation of AQP4 expression secondary to the increased osmotic pressure resulted in cytotoxic edema in the astrocytes in SCC (RESLES). In addition, the upregulation of AQP4 expression may have contributed to the regression of vasogenic edema in PRES. In most cases, the clinical and imaging abnormalities of RESLES are reversible. However, in some cases (such as in patients with severe hypoglycemia), if it is not treated in time, marked central nervous system damage may occur (can be seen permanently on T2 weighted imagines). Based on our hypothesis about the mechanism of RESLES, the upregulation of AQP4 is temporary and slight in most cases, so the clinical and imaging manifestations of most patients are reversible after the etiology is controlled or proper treated. To the best of our knowledge, this pathogenesis for RESLES has never been proposed.