Histopathologic changes in oculomotor nerve and ciliary ganglion in aneurysmatic compression injuries of oculomotor nerve

Abstract

Background: Bilateral common carotid artery ligation (BCCAL) increases vertebrobasilar blood flow and leads to increased luminal pressure, luminal enlargement, wall thinning, convolutions and sometimes aneurysm formation in posterior circulation arteries, especially the posterior communicating arteries (PcomA). PcomA aneurysms compress the oculomotor nerves. The principal aim of this investigation is to examine the histopathologic results of the compressive effect of PcomA aneurysms on the oculomotor nerves (OMN) and on ciliary ganglions (CG). Methods: When we observed the effects of BCCAL on the posterior circulation arteries of the brain in fifteen ligated rabbits after sacrifice, we noticed aneurysm formation on these arteries in three rabbits. These aneurysms developed on the PcomAs compressed the oculomotor nerves. These compressed nerves and normal oculomotor nerves together with their ciliary ganglions were examined histopathologically. Results: A PComA aneurysm developed in three rabbits from 15 ligated animals and these aneurysms compressed the oculomotor nerves on the same side. Partial peripheral necrosis and axonal loss were seen on the compressed oculomotor nerves. Concomitantly, cellular loss and necrosis were also observed on their ganglions. Conclusion: Bilateral common carotid artery ligation may lead to PcomAs and these aneurysms could compress the oculomotor nerves. Compression injuries of oculomotor nerve may cause cellular injury and necrosis on both oculomotor nerves and ciliary ganglions.