Sex differences in intracranial arterial bifurcations.

BACKGROUND: Subarachnoid hemorrhage (SAH) is a serious condition, occurring more frequently in females than in males. SAH is mainly caused by rupture of an intracranial aneurysm, which is formed by localized dilation of the intracranial arterial vessel wall, usually at the apex of the arterial bifurcation. The female preponderance is usually explained by systemic factors (hormonal influences and intrinsic wall weakness); however, the uneven sex distribution of intracranial aneurysms suggests a possible physiologic factor-a local sex difference in the intracranial arteries. OBJECTIVE: The aim of this study was to explore sex variation in the bifurcation anatomy of the middle cerebral artery (MCA) and internal carotid artery (ICA), and the subsequent hemodynamic impact. METHODS: Vessel radii and bifurcation angles were measured in patients with MCA and ICA bifurcations. Data from a previously published study of 55 patients undergoing diagnostic cerebral digital subtraction angiography at Dalcross Private Hospital in Sydney, Australia, between 2002 and 2003, were available for analysis. The measurements were used to create idealized, averaged bifurcations of the MCA and ICA for females and males. Computational fluid dynamics simulations were performed to calculate hemodynamic forces in the models. RESULTS: The vessel radii and bifurcation angles of 47 MCA and 52 ICA bifurcations in 49 patients (32 females, 17 males; mean age, 53 years; age range, 14-86 years) were measured. Statistically significant sex differences were found in vessel diameter (males larger than females; P < 0.05), but not in bifurcation angle. Computational fluid dynamics simulations revealed higher wall shear stress in the female MCA (19%) and ICA (50%) bifurcations compared with the male bifurcations. CONCLUSIONS: This study of MCA and ICA bifurcations in female and male patients suggests that sex differences in vessel size and blood flow velocity result in higher hemodynamic forces acting on the vessel wall in females. This new hypothesis may partly explain why intracranial aneurysms and SAH are more likely to occur in females than in males.

[Treatment practice in primary hyperparathyroidism]. / Behandlingspraksis ved primaer hyperparatyreoidisme.

BACKGROUND: A recent study found considerable regional differences in treatment of primary hyperparathyroidism in Norway. There is no consensus on specific indications for operation in these patients. We surveyed opinions among Norwegian endocrine surgeons and endocrinologists on the indications for surgical treatment of primary hyperparathyroidism. MATERIAL AND METHODS: A questionnaire on preoperative evaluation, indications for surgery and treatment of patients with primary hyperparathyroidism was sent to the chief consultants of surgical departments that operated on parathyroid glands in 2005. The questionnaire was also sent to endocrinologists at the same hospitals. RESULTS: In 2006, 415 parathyroid gland operations were performed in 17 Norwegian hospitals, with a median of 18 operations per hospital. A total of 46 surgeons operated on the parathyroid glands, with a median of two surgeons per hospital. Hospitals differed with respect to preoperative evaluations and indications for operative treatment; but these differences did not coincide with regional differences in the frequency of parathyroid surgery. There was a good correlation between endocrine surgeons and endocrinologists on the indications for surgery in primary hyperparathyroidism, but neither group adhered unconditionally to the international guidelines for surgical treatment of patients with primary hyperparathyroidism. Patients in the hospitals that operated most frequently were initially diagnosed in a surgical department. INTERPRETATION: Our survey did not reveal differences that could explain the large regional variations in the frequency of parathyroid surgery.