Pathophysiology of microwave-induced traumatic brain injury

Microwave technology has been widely used in numerous applications; however, excessive microwave exposure causes adverse effects, particularly in the brain. The present study aimed to evaluate the change in the number of neural cells and presence of apoptotic cells in rats for one month after exposure to excessive microwave radiation. The rats were exposed to 3.0 kW of microwaves for 0.1 sec and were sacrificed after 24 h (n=3), or 3 (n=3), 7 (n=3), 14 (n=3) or 28 days (n=4) of exposure. The neural cells were counted in the motor cortex and hippocampus [cornu ammonis 1 (CA1) and CA2] and the percentage of positive cells stained with terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) were also measured, which detected apoptotic cell death in the choroid plexus in the lateral ventricle, motor cortex and hippocampus. In the CA1, the number of neural cells decreased significantly by day 28 compared with that in the control (60.7 vs. 50.6, P=0.0358), but did not decrease before day 28. There were no significant differences on any day in the CA2 and the motor cortex. The number of cells showed a significant increase on day 7 compared to the control in the choroid plexus (2.1±1.1 vs. 21.8±19.1%, P=0.0318). There were no significant differences from the controls in the percentage of TUNEL-positive cells in the motor cortex and hippocampus. The effects of microwave exposure on the brain remain unclear; however, microwave-induced neurotrauma shows the same pathological changes as blast traumatic brain injury.