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OBJECTIVE: Oxyhemoglobin (OxyHb) is thought to be a critical trigger in the pathogenesis of cerebral vasospasm after aneurysmal subarachnoid hemorrhage. We investigated whether extraluminally applied OxyHb influenced vascular responses to intraluminally applied vasoactive agents in isolated, perfused, canine basilar arteries. METHODS: The steel cannula insertion method was used to examine vascular responses to intraluminally applied 5-hydroxytryptamine (5-HT) receptor agonists, i.e., 5-HT, 5-carboxamidotryptamine (selective for 5-HT 1 receptors), and a-methyl-5-hydroxytryptamine (selective for 5-HT 2 receptors), potassium chloride, and acetylcholine, before and after extraluminal treatment with OxyHb. RESULTS: Extraluminal application of 2.5 x 10 -5 mol/L OxyHb immediately induced a transient elevation of the basal perfusion pressure, which gradually decreased and then stabilized at a level slightly higher than the control level. Each 5-HT agonist induced dose-dependent vasoconstriction. The potencies of the agonists were not very different, but the efficacies varied, i.e., α-methyl-5-hydroxytryptamine > 5-HT > 5-carboxamidotryptamine. Each response was strongly inhibited by ketanserin (a selective 5-HT 2 receptor antagonist), indicating that each agonist induces vasoconstriction mediated by 5-HT 2 receptors. The vasoconstriction in response to each 5-HT receptor agonist was consistently potentiated by treatment with OxyHb (2.5 x 10 -5 mol/L). 5-HT receptor agonist-induced constrictions after OxyHb treatment were much more markedly inhibited by ketanserin, compared with those before OxyHb treatment. Acetylcholine-induced constrictions were enhanced by OxyHb, but KCI-induced constrictions were significantly decreased by OxyHb. CONCLUSION: It is suggested that OxyHb enhancement of constrictions in response to 5-HT receptor agonists may be mediated by increased sensitivity of 5-HT 2 receptors, in addition to actions in the endothelium, in canine basilar arteries. This potentiated vasoconstrictor mechanism may be partially implicated in cerebral vasospasm after subarachnoid hemorrhage.

OBJECTIVE This study was undertaken to define more accurately the feasibility and indications of the contralateral pterional approach to ophthalmic segment aneurysms of the internal carotid artery (ICA). METHODS Between 1995 and 1999, 46 patients with ophthalmic segment aneurysms of the ICA were surgically treated in our institution. Eleven of the 46 aneurysms were operated using the contralateral pterional approach. All aneurysms were successfully clipped without complications; three patients required bone resection around the aneurysm neck. We studied the 11 patients who were treated with the contralateral approach by defining six parameters to assess the feasibility of the approach and to predict the necessity for bone resection: 1) Parameter A, the distance between the anterior aspect of the optic chiasm and the limbus sphenoidale; 2) Parameter B, the distance between the bilateral optic nerves at the entrance to the optic canal; 3) Parameter C, the interrelation of the optic nerve and the ICA, expressed as a/b in which a is the length from the midline to the optic nerve and b is the length from the midline to the ICA; 4) Parameter D, the size of the aneurysm neck; 5) Parameter E, the direction of the aneurysm from the ICA wall on the anteroposterior angiogram; and 6) Parameter F, the distance from the medial side of the estimated distal dural ring to the proximal aneurysm neck on the lateral angiogram. RESULTS Parameters A to F were 8.8 mm (range, 5.4–11.1 mm), 14.5 mm (range, 10.4–22.2 mm), 0.9 mm (range, 0.6–1.3 mm), and 3.0 mm (range, 2.3–4.7 mm), 5 to 160 degrees, and 1.3 mm (range, 0.3–2.4 mm), respectively. All patients had excellent operative outcomes without visual dysfunction. Three patients required drilling of the bone around the optic canal on the craniotomy side; bone drilling was not required when Parameter E was between 30 and 160 degrees and Parameter F was more than 1 mm. CONCLUSION Parameters A to D are important for assessing the feasibility of the contralateral approach to ICA-ophthalmic segment aneurysms, and Parameters E and F are most useful for calculating the difficulty of this approach.