Vagal ischemia induced lung immune component infarct following subarachnoid hemorrhage: An experimental study

Abstract

Aim: Neurogenic pulmonary edema (NPE) is the most serious complication of subarachnoid hemorrhage (SAH). As vagal nerves have vital roles in lung functions, vagal ischemia may have a causative role in the pathogenesis of NPE. We examined whether there was a relationship between vagal complex ischemia and lung immune complexes occupying the lymph node infarct in SAH. Material and Methods: Thirty-two rabbits were divided into three groups: Control (n=5), SHAM (n=5) and SAH group (n=22). SAH was created by autologous blood injection into the cisterna magna and followed-up for 3 weeks. Vasospasm index (VSI) was defined as the ratio of the lung lymph node arteries (LLNA) wall section (wall ring) surface to the lumen surface. Degenerated axon numbers of vagal nerves, neuron densities of the nodose ganglion (NG) and VSIs of LLNA were compared for all groups. Results: The mean degenerated vagal nerve axon density, neuron density of NG, and VSI of LLNA were 26±8/mm2, 30±5/mm3, and 0.777±0.048 in the control group; 1300±100/mm2, 720±90/mm3, and 1.148±0.090 in the animals with slight vasospasm (n=12); and 7300±530/mm2, 5610±810/mm3, and 1.500±0.120 in the animals with severe vasospasm (n=10), respectively. Conclusion: Degenerated vagal axon and NG neuron density may be a causative factor in the development of LLNA vasospasm induced lymph node infarct in SAH. Lung lymph node infarct may be an important factor in the prognosis of NPE.