Loss of Consciousness Diagnosis

  • Diagnosis

    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.

    Click to enlarge: MRI Scan Showing a Brain Tumor

    Figure 01. MRI Scan Showing a Brain Tumor

    The symptoms of ALC are varied. Initial signs of ALC can be as subtle as slurring words while talking, or as severe as death. ALC can present as any of the levels of consciousness, from confusion to stupor to coma.

    Symptoms accompanying ALC provide clues to the underlying cause Table 01. For example, if a person with ALC also has a tongue that is bitten or scarred, a doctor would suspect that epilepsy is the underlying cause. Likewise, if the person with ALC also has neck stiffness, the doctor may suspect that meningitis is the cause.

    Table 1.  Possible Causes of ALC by Accompanying Symptom or Sign

    System or region Symptom Possible cause(s)
    Vital signs Hypertension Cerebral hemorrhage, hypertensive encephalopathy, increased intracranial pressure, renal or endocrine disorder
    Hypotension Ethanol or sedative drug toxicity, blood loss, diabetic coma
    Hyperthermia Systemic infection, heat stroke, withdrawal from alcohol or drugs
    Hypothermia Ethanol or barbiturate toxicity, shock, extracellular fluid deficit
    Bradycardia Heart block, Stokes-Adams syndrome, increased intracranial pressure, hypothyroidism
    Tachycardia Arrhythmia associated hypoxemia; atrial fibrillation associated with cerebral embolism
    Breath Peculiar odor Alcohol ingestion, hepatic failure, ketoacidosis, or uremia
    Skin Jaundice Hepatic disorder
    Needle-tracks Drug overdose
    Rashes Infectious disease, drug reaction, autoimmune disease, pellagra, thrombotic thrombocytopenic purpura
    Pallor Hemorrhage (internal or external)
    Head Localized tenderness, hematoma, crepitus Skull fracture
    Hemorrhage from ears or nostrils; hematoma, tenderness, or crepitus over mastoid process Basilar skull fracture
    Face and conjunctiva hyperemic Alcohol intoxication
    Tongue bitten or scarred Epilepsy
    Neck Stiffness Suggests meningitis/encephalitis, trauma, or subarachnoid hemorrhage

    Certain causes of ALC are more common in particular groups of individuals. Traumatic brain injury is the leading cause of death and disability in those under 45 years of age, while metabolic problems, which can also cause ALC, occur most often in middle-aged and older people.

    As most people with ALC are incapable of providing information about their own condition, information from family, friends, and bystanders is very valuable for doctors trying to make a diagnosis. If you witness someone suffering from ALC, you should go to the hospital with the person to provide information to the doctors. Similarly, make sure that any bottles of chemicals or other substances that the person may have ingested are taken to the hospital.

    The doctor will ask a family member or a witness about what happened before the ALC occurred, and will also ask about any other illnesses or allergies the person may have. If you were a witness to someone experiencing ALC, the doctor would want you to describe what the person was doing before calling for help. For example, was the person staggering, talking incoherently, or did they pass out? Was the person working with an insecticide, did they have the car running in an enclosed area? The doctor may also ask about family history of diseases that could cause ALC, orabout any possible allergies the person may have.

    • Has the person complained of headaches recently? If so, how frequent and severe have the headaches been?
    • Has the person experienced any episodes of dizziness?
    • Is there any tingling, numbness, or pricking feelings in the arms and legs?
    • Have there been any seizures, tremors, or weakness?
    • Has the person been able to understand what people are saying, and has the person been able to make themselves understood by others?
    • Has the person had any trouble reading or writing?

    After the history, the doctor will perform a quick physical and neurological exam. Since the brain also controls heart rate and rhythm, breathing characteristics, blood pressure, and body temperature, the doctor will check these vital signs for clues about the origin of ALC. The doctor will also evaluate level of consciousness by asking the person to recite their own name, and then assessing how well they are oriented to time and place. The doctor will then shine a light into the person’s eyes to see if both of the pupils get smaller, and will test whether the person has control over the muscles of the eyes by having them follow an objector finger around their field of vision. An EEG may also be run to check for the condition nonconvulsive status epilepticus (NSE) as a cause of coma.

    Laboratory tests on the blood and other body fluids help the doctor make a diagnosis. Blood tests can help rule out metabolic reasons for ALC such as diabetes or kidney failure. Blood and urine tests can also be used to detect levels of medication or drug overdose.

    The doctor may perform radiologic tests to help diagnose physical causes of ALC. Skull x-rays and computed tomography (CT) scans can detect fractures, tumors, and abnormal blood vessels. CT scans are also useful when bruising or inflammation are suspected. Cerebral angiography uses a special dye to highlight the blood vessels in the brain to see where they might be narrowed or obstructed. Magnetic resonance imaging (MRI) studies may be used to get a better view of the soft tissue—for example, when a stroke or an aneurysm might be the cause of concern. The MRI also is less affected by bones, and can get specific views of the brain that aren’t available using conventional x-rays. If the cause of ALC remains unknown after these tests, the doctor may order a chest radiograph to determine if cardiac or pulmonary disease is the culprit. If the doctor suspects meningitis, and the CT scan is normal, he or she will perform a spinal tap, looking for laboratory evidence of infection. This procedure involves putting a needle into the spinal cord.

    Take precautions while driving or engaging in activities where head injuries might be possible. Wear helmets and other protective gear when engaging in contact sports, skateboarding, riding a bicycle or motorcycle, or participating in other forms of recreation where head injuries might be possible. Wear appropriate protective gear if required at your job. You should also wear a seatbelt when in a car to avoid head injuries from an accident.

    Drink alcohol in moderation. Alcohol dulls your reflexes and decreases judgment, increasing the likelihood that you will get in an accident that could cause a head injury. Therefore, if you drink, do so in moderation, and do not attempt to drive or take part in other activities that require attention.

    If you are diabetic, maintain appropriate blood sugar levels. Excessively high or low blood sugar levels can lead to ALC. Therefore, be sure to monitor your blood sugar levels closely if you are diabetic.

    Take precautions to avoid stroke, which can cause ALC. You can reduce your risk for ALC-causing stroke by controlling high blood pressure, treating heart rhythm problems, watching for and treating cholesterol problems, and quitting smoking.

    Get the Haemophilus vaccine (HiB vaccine) to prevent a type of meningitis. As ALC can be triggered by meningitis and other infections, get the HiB vaccine to protect yourself against a certain strain of the infection. Teenagers are also advised to get an additional vaccine, Menactra, to prevent meningitis cause by a different bacteria.

  • Prevention and Screening

    Take precautions while driving or engaging in activities where head injuries might be possible. Wear helmets and other protective gear when engaging in contact sports, skateboarding, riding a bicycle or motorcycle, or participating in other forms of recreation where head injuries might be possible. Wear appropriate protective gear if required at your job. You should also wear a seatbelt when in a car to avoid head injuries from an accident.

    Drink alcohol in moderation. Alcohol dulls your reflexes and decreases judgment, increasing the likelihood that you will get in an accident that could cause a head injury. Therefore, if you drink, do so in moderation, and do not attempt to drive or take part in other activities that require attention.

    If you are diabetic, maintain appropriate blood sugar levels. Excessively high or low blood sugar levels can lead to ALC. Therefore, be sure to monitor your blood sugar levels closely if you are diabetic.

    Take precautions to avoid stroke, which can cause ALC. You can reduce your risk for ALC-causing stroke by controlling high blood pressure, treating heart rhythm problems, watching for and treating cholesterol problems, and quitting smoking.

    Get the Haemophilus vaccine (HiB vaccine) to prevent a type of meningitis. As ALC can be triggered by meningitis and other infections, get the HiB vaccine to protect yourself against a certain strain of the infection. Teenagers are also advised to get an additional vaccine, Menactra, to prevent meningitis cause by a different bacteria.

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