Page 63 - Read Online

Topic: The Role of Inflammation in Cerebral Aneurysm

Cerebral aneurysms and inflammation

Toshihiro Yokoi, Makoto Saito, Yayoi Yoshimura, Keiichi Tsuji, Kazuhiko Nozaki
Department of Neurosurgery, Shiga University of Medical Science, Shiga 520‑2192, Japan.

ABSTRA CT
Multiple inflammatory factors, playing a crucial role in cerebral aneurysm formation, have been identified. Tumor necrosis
factor‑alpha (TNF‑α) has been revealed to have a close connection with several risk factors that affect aneurysm formation. Remarkable
expression in aneurysm walls of mRNA for TNF‑α has been observed in humans. Possible therapeutic interventions to reduce the
formation of cerebral aneurysms may include the inhibition of mediators of inflammation.
Key words: Cerebral aneurysm, inflammation, molecular biology

INTRODUCTION size categories. In one study, the annual rupture
rate of unruptured cerebral aneurysms in a Japanese
Most unruptured aneurysms, which are detected cohort was 0.95%. In another, the average annual
[2]
incidentally show stable clinical courses, exhibit risk of rupture associated with small unruptured
fewer inflammatory or degenerative changes in the aneurysms was 0.54% overall, 0.34% for single
walls of affected blood vessels, and have a low risk aneurysms and 0.95% for multiple aneurysms. The
[3]
of rupture. However, some unruptured aneurysms molecular mechanisms leading to the occurrence,
show significant changes in size and shape, and the development, and rupture of cerebral aneurysms
rupture risk seems to be high. These aneurysms may have been experimentally investigated. Ruptured
rupture in the early phase of development or enlarge aneurysms manifest significant endothelial damage,
in a short time due to thinning of vessel walls resulting structural changes in vessel walls, and inflammatory
from the advancement of degenerative changes. It is of cell invasion compared to unruptured aneurysms.
[4]
clinical relevance to accurately estimate the rupture The walls of ruptured aneurysms are fragile, possibly
risk of cerebral aneurysms, but no definitive methods because macrophage infiltration into the aneurysm
exist to distinguish rupture‑prone aneurysms from wall results in the loss of smooth muscle cells and
rupture‑resistant ones. Recently, the rupture risk of degeneration of matrix proteins. In this manuscript,
unruptured cerebral aneurysms was reported. The we discuss the molecular mechanisms of cerebral
5‑year cumulative rupture rates for aneurysms located aneurysm development, focusing on inflammatory
in the internal carotid artery, anterior communicating processes.
artery, anterior cerebral artery, or middle cerebral
artery in patients without a history of subarachnoid INFLAMMATION AND ABDOMINAL AORTIC
hemorrhage were 0%, 2.6%, 14.5%, and 40% for ANEURYSMS
aneurysms < 7 mm, 7‑12 mm, 13‑24 mm, and 25 mm
or greater, respectively. By comparison, the rupture The crucial role of inflammatory reactions can be seen
[1]
rates of aneurysms involving the posterior circulation in the formation of abdominal aortic aneurysms (AAAs).
and the posterior communicating artery were 2.5%, Important histological features of vessel walls with
14.5%, 18.4%, and 50%, respectively, for the same AAAs include chronic inflammatory cell infiltration
of the adventitia and media, elastin fragmentation,
Access this article online degeneration, and attenuation of the media. Collagen
Quick Response Code: in the media and adventitia provides tensile strength
Website: to the aortic wall. Collagen synthesis increases during
www.nnjournal.net
the early stages of aneurysm formation, suggesting a
[5]
DOI: repair process. Inflammation‑related mediators in
10.4103/2347-8659.153977 aneurysm growth include matrix‑degrading proteinases,
proinflammatory cytokines, and chemokines. In later
[6]
Corresponding Author: Dr. Toshihiro Yokoi, Department of Neurosurgery, Shiga University of Medical Science,
Seta Tsukinowa‑cho, Otsu, Shiga 520‑2192, Japan. E‑mail: tyokoi@belle.shiga‑med.ac.jp

Neuroimmunol Neuroinflammation | Volume 2 | Issue 2 | April 15, 2015 55