Ruptured intracranial aneurysm following gamma knife surgery for acoustic neuroma.

A-63-year-old woman underwent gamma knife surgery (GKS) for acoustic neuroma. Six years later, she suffered sudden onset of severe headache followed by a disturbance of consciousness and subarachnoid haemorrhage due to a ruptured aneurysm originating from the distal anterior inferior cerebellar artery. The aneurysm was not located at a branching site and was included within the radiation field. The aneurysm was treated by endovascular embolization, and now, 15 months later, the patient has recovered satisfactorily. This is the first report of aneurysm formation following GKS for acoustic neuroma.

Radiation-induced cerebral aneurysm successfully treated with endovascular coil embolization.

In a 30-year-old male, multiple cerebral aneurysms developed 19 years after receiving 60 Gy of irradiation for craniophariginoma. Angiogram revealed right IC-PC and upper basilar trunk aneurysms in addition to atherosclerotic change. The right IC-PC aneurysm was wrapped and the basilar trunk aneurysm located between the origins of SCA and AICA was treated by endovascular coil embolization. The packing of the aneurysm was complete, but stenosis of the basilar artery appeared. The patient was discharged uneventfully and follow-up angiogram 6 months later demonstrated that the aneurysm had disappeared and the patency of the basilary artery had been preserved. Radiation-induced intracranial vasculopathy is a well-recognized phenomenon, but aneurysm formation is less common than arterial occlusive lesion. However, the mortality rate after bleeding is so high that immediate diagnosis and treatment by direct surgery or coil embolization are necessary.

HEPES inhibits contractile responses of canine basilar artery.

N-2-hydroxyethylpiperazine-N'-2-ethanesulphonic acid (HEPES) is a commonly-used buffer. This study determined the effect of HEPES on contractility of the dog basilar artery and tested the hypothesis that HEPES inhibits vasoconstriction of isolated arterial segments by generating H2O2. Rings of dog basilar artery with or without endothelium were suspended under isometric tension and contracted with KCl, serotonin, or prostaglandin F2 alpha (PGF2 alpha) in bicarbonate or HEPES buffer. Addition of HEPES, 30 mmol l-1, before or after contraction with KCl, serotonin or PGF2 alpha significantly decreased maximal tension in rings with or without endothelium. Preincubation with HEPES buffer, 10 mmol l-1, significantly decreased maximal contractions to each agonist in rings with endothelium and to KCl and serotonin in rings without endothelium. HEPES, 30 mmol l-1, noncompetitively inhibited concentration-contraction curves to increasing concentrations of each agonist in rings with or without endothelium. Inhibition by HEPES was completely reversible with washing. The inhibitory effects of HEPES on responses to each agonist in rings with endothelium were significantly less in the dark or after coincubation with catalase. Unlike HEPES, effects of H2O2 were endothelium-dependent in that H2O2 caused contractions in rings with endothelium and relaxations in rings without endothelium. 5-(N,N'-dimethyl)-amiloride and 4,4'-diisothiocyanataostilbene-2,2'-disulfonic acid did not affect contractility in this preparation. These results show that HEPES exerts significant inhibitory effects on arterial smooth muscle contractility. The mechanism does not involve endothelium-dependent relaxation, effects on chloride channels or the sodium-hydrogen exchanger or generation of H2O2 by HEPES in the light.

Age dependency of nanosecond fluorescence characteristics in human arteries.

Human arteries fluoresce as a result of illumination by UV-light. The fluorescence characteristics of the human aorta and basilar artery were investigated with respect to aging. For this experiment, a time-resolved microscope fluorometer was employed. Resultant fluorescence decayed on a nanosecond scale when applying pulse UV-light. These fluorescences were found to be age dependent in the basilar artery; the fluorescence decay time decreased with increasing human age. However, fluorescence from the aorta did not show the age dependency.

Controlled ultraviolet irradiation generates endothelial damage without affecting the nerve terminals of the cerebral artery in cats.

The vesicles of adventitial autonomic nerve terminals were examined quantitatively under an electron microscope in controlled ultraviolet ray (UV)-irradiated cerebral vessels. Five cats whose basilar arteries were irradiated with UV (UV group) and 5 cats whose basilar arteries were irradiated with visible rays (control group) were compared. Endothelial vacuolation was observed only in the UV group. There was no statistically significant difference in the diameters of the dense-cored vesicles, related to noradrenaline, and clear vesicles, related to acetylcholine, between the two groups. It is concluded that controlled UV irradiation which generates endothelial damage does not affect the vascular adventitia ultrastructurally.

Radiation-induced aneurysm of the basilar artery--a case report.

A dolichoectatic basilar artery aneurysm, following irradiation for nasopharyngeal carcinoma, is described and discussed.

Stereotactic gamma irradiation of basilar artery in cat. Preliminary experiences.

Irradiation of the basilar artery of cats by stereotactic technique was performed with doses varying from 100 to 300 Gy in a gamma unit. Histologically, vascular lesions such as vacuolization, degeneration and desquamation of the endothelium and hyalinization and necrosis of the muscular coat predominated, whereas reparatory reactions were relatively sparse. Thrombosis was completely absent.