Histopathological Alterations in Ciliary Ganglions in Meningitis: An Experimental Study

Abstract

Although it is well known that meningitis frequently results in optic nerve (ON) and oculomotor nerve (OMN) dysfunctions, the effects of meningitis on the ciliary ganglion (CG) have not been studied. It is expected that the CG may be affected due to the involvement of these cranial nerves in meningitis. In this study, we aimed to investigate the effect of meningitis on the CG. This study was conducted on thirteen rabbits. Experimental meningitis has been achieved with Streptococcus pneumonias inoculation into the cisterna magna of the animals. After follow-up of two months, all animals were sacrificed. CGs of all animals were examined histopathologically. Neuron numbers and morphological changes of the CGs were examined. Arachnoiditis and axonal degeneration at the cisternal segments of both oculomotor and optic nerves were observed. Neuronal irregularity, cellular angulation, shrinkage, nuclear irregularity and cytoplasmic condensation were observed in neurons of the CG. The mean number of live neurons in a CG was 3200 in healthy rabbits, whereas it was 2800 in animals with meningitis. Cisternal segments of the ON and OMN have a meningeal sleeve and a rich vascular supply. Meningitis may cause vasculitis or vasospasm at these arteries and may result in infectious neuropathy of the OMN and ON, and also afferent and efferent loops of the light reflex were structurally interrupted. Consequently, parasympathetic preganglionic denervation of the CG may occur and may result in degeneration in the neurons of the CG.