The human brain can adjust its level of alertness as needed through information gained from sensory organs. But when outside agencies come into contact with the brain stem, altered levels of consciousness may be unavoidable. Obtundation, or a general reduction in alertness, can often lead to stupor if medical attention is not quickly administered.
According to the Merck online medical library, the term "obtunded," a form of obtundation, is an imprecise way to describe someone whose alertness or consciousness is moderately reduced. The National Institute of Health classifies obtundation as similar to lethargy and describes an obtunded patient as having lessened interest in the environment and slower responses to stimulations.
Stupor is a state from which someone can only be aroused, only briefly, by extreme stimulation, such as shaking or pinching. It differs from a coma, from which a person cannot be aroused. According to the NIH, patients in stupor will, unless stimulated, lapse back into an unresponsive state. The Daily Medical online journal lists levels of consciousness from a normal state as: alert, lethargic, somnolent, obtunded, stuporous and comatose.
Some drugs, and even minor physical ailments such as dehydration, can cause elderly persons to become stuporous, but altered consciousness has dozens of possible causes for people of any age. A head injury, stroke, tumor, drugs, alcohol, seizures, cardiac arrest, carbon monoxide and even infections or altered blood sugar levels can cause a patient to become obtunded and even progress to stupor.
Because doctors may not be able to communicate with a patient whose consciousness is altered, family and friends must communicate their knowledge of any drug or alcohol use by the patient. Someone who has overdosed on drugs, for example, may be obtunded but able to communicate. A patient who can only intermittently be aroused is said to be in stupor.
A physical examination, including a body temperature reading, is conducted first to determine possible causes. Stimuli isthen be applied; if the patient reacts, consciousness is not severely affected. Abnormal breathing patterns or reactions to reflex stimulation can also help determine levels of alertness.