Letter to the Editor Regarding the Manuscript of “The Longest Angiographic and Clinical Follow-Up of Microsurgically Treated Giant Intracranial Aneurysms: Experience with 70 Cases”

Abstract

Posterior cerebral blood flow is regulated by the basilar arteries (BAs). Vasospasm of BAs can occur after subarachnoid hemorrhage (SAH). Superior cervical sympathetic ganglia (SCG) fibers have a vasoconstrictor effect on the BA. We aimed to investigate the relationship between the degenerated neuron density of the SCG and the severity of BA vasospasm after experimental SAH.Twenty-four rabbits were used. Five were used as the control group, and 5 were used as the sham group. Experimental SAHs were performed in the remaining 14 animals (study group) by injecting homologous blood into the cisterna magna. After 3 weeks of injection, neuron densities of SCG and the severity of BA vasospasm index values (VSI) were examined histopathologically and compared statistically.The mean VSI was 0.669 ± 0.1129 in the control group, 0.981 ± 0.159 in the sham group, and 1.512 ± 0.298 in the study group. The mean degenerated neuronal density of SCG was 436 ± 79/mm3 in severe vasospasm (n = 3), 841 ± 101/mm3 in moderate vasospasm (n = 4), and 1.921 ± 849/mm3 in the less vasospasm detected animals (n = 6).This study shows an inverse relationship between the degenerated neuronal density in the SCG and VSI values. This finding indicates a diminished sympathetic input from the SCG, resulting in a beneficial effect (the felix culpa) by dilating the lumen diameter of the BA, so SCG degeneration after SAH protects the BA spasm.