No abstract

Sinus pericranii is a rare vascular anomaly involving an abnormal communication between the extracranial and intracranial circulations. A case of frontal sinus pericranii is presented which appeared to be a posttraumatic sinus because it developed 2 years after a cranial injury. However, the presence of vascular endothelium in the pathological examination and its association with a vascular anomaly (persistent trigeminal artery) suggested a congenital origin. The lesion, pericranial blood sinuses, and bone were totally removed. The computerized tomography, angiography, and magnetic resonance imaging findings are presented. The literature is reviewed and the pathogenesis of sinus pericranii is discussed.

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Determination of optimal population densities underlies the economic rationality when planning the provision of basic public infrastructure by local governments. Using econometric techniques based on the translog cost function, we investigate the existence of economies of scale, associated to a larger urban size in terms of population and housing, determine the effect of alternative urban patterns -compact or dispersed -on the cost of provision, and calculate optimal population densities as targets for urban planning. We illustrate the practicality of our model using Spanish municipal data, and unveil latent economies of scale and suboptimal urban densities due to excessive dispersion. Based on these findings we propose specific policy guidelines in terms of desirable urban structures.JEL classification: C3, D24, H1, H4, R53