There are only scattered case reports of intracranial tuberculosis in industrialized nations; brainstem tuberculoma is even more unusual, accounting for 2.5% to 8% of all intracranial tuberculoma. In developing nations, however, central nervous system tuberculosis (CNS-TB) is not rare and intracranial tuberculoma may account for 5% to 30% of all intracranial masses. The authors present two cases of CNS-TB with expansion to brainstem tuberculoma in patients who were undergoing treatment and had no known prior exposure to Mycobacterium tuberculosis.
Blood in mouth, nose, and eye tissues of birds cools by evaporation, then flows to a cephalic vascular heat exchanger, the ophthalmic rete. There, acting as a heat sink, blood from the evaporative surfaces cools arterial blood flowing counter-current to it toward the brain. The brain thus remains cooler than the body core. Data for unanesthetized domestic pigeons (Columba livia) suggest that in addition to losing heat, blood perfusing the evaporative surfaces also exchanges oxygen and carbon dioxide with air. In the heat exchanger, this blood apparently gives up oxygen to, and gains carbon dioxide from, arterial blood. The consequent increase in oxygen and decrease in carbon dioxide in the brain's arterial blood enhance diffusion of these gases in, and oxygen supply to, the brain. Such events may help birds maintain the brain's oxygen supply during the high systemic demand of exercise and at the reduced oxygen availability of high altitude.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.