Abstract: Objective: To investigate the pathological course in the intracranial aneurysms. Methods: One case normal intracranial artery(from cortex fistulization), 11 cases ruptured aneurysms, two cases unruptured aneurysms were obtained from neurosurgical excision. Routine HE stain was used to observe histological characteristics, immunohistochemistry was used to observe the expression of monocyte chemoattractant protein-1(MCP-1)and macrocyte inflammation protein-1α(MIP-1α)in the walls of the normal artery and aneurysms(unruptured and ruptured). Result: By the HE strain the wall of the ruptured aneurysms(10 cases)and unruptured ones(2 cases)consisted of incrassated intima and connectivum extima. The fibroblast in the intima was arrayed in the disorder. Monocyte-like cells could be seen in the whole aneurysm wall. In one case of aneurysm wall(ruptured)glass-like fiber structure was left over, and few cells could be seen. Nine cases of mural thrombus could be found. The thrombus represented with organization. Immunohistochemistry: MCP-1 and MIP-1α were not detectable in the normal artery; the immunohistochemistry signal of MCP-1 and MIP-1α could be observed upregulated in the ruptured aneurysms(10 cases)and unruptured ones(2 cases), often in the intima. MCP-1 and MIP-1α appeared to be expressed by Fibroblast cell in its cytoplasm. Monocyte-like cells had little cytoplasm, the signal was seldom seen. The immunohistochemistry signal was discontinuous in the intima, MCP-1 and MIP-1α expressed where fibroblast and monocyte-like cells assembled. One case of ruptured aneurysms had no signal because there were no cells, only glass-like fiber. Mural thrombus had upregulated signal of MCP-1 and MIP-1α in the cytoplasm of fibroblasts and endotheliocytes of its micrangium. Conclusion: the pathological representation of the ruptured and unruptured aneurysms and the upregulated expression of MCP-1 and MIP-α in the aneurysm wall suggest that the development of the aneurysm may be a course of the chronic inflammation whose main inflammatory cells are monocyte-like cells.

Key words: intracranial aneurysms, monocyte chemoattractant protein-1, macrocyte inflammation protein-1α, immunohistochemistry, chronic inflammation