Cerebral hypoxia is a medical term that refers to an insufficient supply of oxygen to the brain. In a strict technical sense, the term refers to a lack of oxygen in the outer area of the brain, or the cerebral hemisphere. It is generally used, however, to refer to any general lack of oxygen supply to the brain, regardless of where the specific lack is located. Prolonged cerebral hypoxia kills brain cells as they need oxygen to sustain themselves properly. Long-term hypoxia, then, can lead to severe cognitive and motor impairment or even death as a result of severe brain damage.
There are four main categories of cerebral hypoxia, organized by severity. The first, diffuse hypoxia, refers to a mild decrease in brain function as a result of decreased oxygen levels. Focal hypoxia refers to a localized decrease in oxygen levels and is often related to a mild stroke or aneurysm. A transient ischemic attack, also known as a mini-stroke, is a localized hypoxia lasting less than 24 hours that results in neurological impairment. Massive cerebral infarction occurs when blood flow to several areas of the brain is stopped; this is also referred to as a stroke.
Symptoms of cerebral hypoxia can be physical or neurological in nature and tend to vary greatly based on the severity of oxygen deprivation. In mild cases, individuals tend to demonstrate poor judgment and may be generally inattentive. They may also have motor difficulties, finding it much more difficult than usual to complete normal actions such as walking and holding onto objects. In particularly severe cases, the individual may slip into a coma and become completely unresponsive to and unaware of all stimuli. A coma can, in severe cases, be accompanied by complete loss of breathing.
If severe cases of cerebral hypoxia are not treated immediately, death is likely. In cases in which pulse and blood pressure remain normal but the hypoxia victim is otherwise unresponsive, complete brain death may have occurred. In such cases, there is no hope for restoring the victim to any semblance of complete and normal functionality.
Cerebral hypoxia can be caused in many different ways. Some causes are related to external factors such as drowning or excessive smoke or carbon monoxide inhalation. These can lead to asphyxiation if regular air flow is not returned quickly. Internal factors that can lead to cerebral hypoxia include stroke, cardiac arrest, low blood pressure, and paralysis of breathing muscles.