page_title: Cerebral hypoxia
section_title: Signs and symptoms
hierarchical_section_title: Cerebral hypoxia / Signs and symptoms
caption_attribution_description: This image is part of a series which can be scrolled interactively with the mousewheel or mouse dragging. This is done by using Template:Imagestack. The series is found in the category Profound hypoxia case 001. Computertomographie des Schädels bei einem Patienten nach generalisierter Hypoxie: Besonders die stoffwechselintensiven und somit hypoxieempfindlichen Regionen wie Globus pallidum, Hippocampus und auch die Hirnschenkel sind betroffen. Auch die Mark-Rinden-Differenzierung ist deutlich vermindert.
context_page_description: Cerebral hypoxia is a form of hypoxia, specifically involving the brain; when the brain is completely deprived of oxygen, it is called cerebral anoxia. There are four categories of cerebral hypoxia; they are, in order of severity: diffuse cerebral hypoxia, focal cerebral ischemia, cerebral infarction, and global cerebral ischemia. Prolonged hypoxia induces neuronal cell death via apoptosis, resulting in a hypoxic brain injury.
  Cases of total oxygen deprivation are termed "anoxia", which can be hypoxic in origin or ischemic in origin. Brain injury as a result of oxygen deprivation either due to hypoxic or anoxic mechanisms are generally termed hypoxic/anoxic injuries. Hypoxic ischemic encephalopathy is a condition that occurs when the entire brain is deprived of an adequate oxygen supply, but the deprivation is not total. While HIE is associated in most cases with oxygen deprivation in the neonate due to birth asphyxia, it can occur in all age groups, and is often a complication of cardiac arrest.
context_section_description: The brain requires approximately 3.3 ml of oxygen per 100 g of brain tissue per minute. Initially the body responds to lowered blood oxygen by redirecting blood to the brain and increasing cerebral blood flow. Blood flow may increase up to twice the normal flow but no more.  If the increased blood flow is sufficient to supply the brain's oxygen needs then no symptoms will result.
  However, if blood flow cannot be increased or if doubled blood flow does not correct the problem, symptoms of cerebral hypoxia will begin to appear. Mild symptoms include difficulties with complex learning tasks and reductions in short-term memory. If oxygen deprivation continues, cognitive disturbances, and decreased motor control will result. The skin may also appear bluish (cyanosis) and heart rate increases. Continued oxygen deprivation results in fainting, long-term loss of consciousness, coma, seizures, cessation of brain stem reflexes, and brain death.
  Objective measurements of the severity of cerebral hypoxia depend on the cause. Blood oxygen saturation may be used for hypoxic hypoxia, but is generally meaningless in other forms of hypoxia.  In hypoxic hypoxia 95–100% saturation is considered normal; 91–94% is considered mild and 86–90% moderate. Anything below 86% is considered severe.
  Cerebral hypoxia refers to oxygen levels in brain tissue, not blood.  Blood oxygenation will usually appear normal in cases of hypemic, ischemic, and hystoxic cerebral hypoxia. Even in hypoxic hypoxia blood measures are only an approximate guide; the oxygen level in the brain tissue will depend on how the body deals with the reduced oxygen content of the blood.
caption: CT in a person after generalized hypoxia.
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