When something interferes with interactions in the brain that allow awareness, a person’s level of consciousness can change in several ways. Altered level of consciousness (ALC) is among the most common problems seen in medicine. Studies estimate that up to 5% of emergency room admissions in urban hospitals are related to disorders of consciousness.
Consciousness can be measured on a spectrum that ranges from full wakefulness to deep coma.
Altered levels of consciousness include the following conditions:
Confusion: A confused person cannot properly process all the information from their surroundings. Apathy and drowsiness are the most noticeable symptoms. The person may be disoriented, especially to time. A severely confused person is usually unable to carry out more than a few simple commands.
Delirium: This is a common and complicated problem, especially in the elderly. The signs of delirium include disorientation, which may be total. People with delirium may not remember who they are, or may have delusions and hallucinations. People with delirium may also become drowsy or less alert at times.
Obtundation: A lower level of alertness typically characterizes this state. A person in this state often sleeps much more than usual, and when awakened, remains drowsy and confused. Wakefulness can only be maintained by continuously talking to the person, or through constant painful stimulation.
Stupor: Stupor is characterized by unresponsiveness from which a person can be aroused only by vigorous and repeated painful stimulation.
Coma: A person in a coma appears to be asleep, but cannot be awakened. Oftentimes reflexes are absent, and the legs and arms may be rigid. The respiration rate of someone in a coma is usually slowed.
Trauma to the brain can cause impaired consciousness. Traumatic brain injury (TBI) is the leading cause of death and disability in young adults in the U.S. Several types of head trauma may cause TBI. For example, a closed head injury—the most common TBI—can result if the head rapidly accelerates or decelerates, causing the brain to move through the fluid in the skull and strike the inside of the skull. Other causes include direct impact on the head or penetration by a foreign object such as a bullet.
Infections are a common cause of impaired consciousness. The inflammation that accompanies infection is responsible for ALC. Encephalitis and meningitis are two nervous system-specific infections that can cause ALC.
Defects in the metabolic system can lead to waste build-up that can cause altered levels of consciousness (ALC). As the body goes about the normal processes needed to keep us alive, chemicals and other by-products are produced. In most cases, byproducts get into the bloodstream and are filtered by the liver, kidneys, and other organs. If one of these systems fails, waste products can build-up and act as a poison that interferes with the brain’s ability to function. The insulin/sugar imbalance of diabetes, for example, is a major metabolic problem that can cause impaired consciousness. Diabetics with low blood insulin levels produce ketones, a toxic by-product of fat metabolism. Conversely, when there is too much insulin, cells begin to starve to death. Either case can result in ALC.
Drug exposure is a common cause for ALC. Drug-induced ALC can result from an overdose of either over-the-counter or illegal drugs. Alcohol intoxication is probably the most common cause of drug-induced ALC. Similarly, exposure to certain readily available home or industrial chemicals can lead to changes in consciousness or even to death.
Structural abnormalities of the brain can lead to ALC Figure 01. Tumors (benign or cancerous) can form and crowd out the normal structures of the brain. As a result, weakness in the walls of the blood vessels in the brain (aneurysms) may begin to swell, or may even break, causing blood to pool inside the head and push the brain against the bony wall of the skull. The resulting damage can then cause ALC.
Figure 01. MRI Scan Showing a Brain Tumor
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