Cognitive function is the term used to describe a person's state of consciousness (alertness and orientation), memory, attention span, and insight. A mental status examination (MSE) is a standard tool used by clinicians to measure a patient's overall mental health. Evaluating a patient's cognitive functions includes first of all, measuring the level of alertness and orientation.
Awareness and thinking are dependent on integrated and organized thoughts, subjective experiences, emotions, and mental processes, each of which resides, to a certain extent, in anatomically defined regions of the brain. Self-awareness requires that the organism senses this personal stream of thoughts and emotional experiences. The inability to maintain a coherent sequence of thoughts, accompanied usually by inattention and disorientation, is the best definition of confusion, a disorder of the content of consciousness.(1)
is a measure of a patient's awareness of his or her environment and situation. Abnormal states range from confusion to lethargy, delirium, stupor, and at the end of the spectrum, coma. Similarly, orientation is a person's ability to describe knowledge of person, place, and time. Simple questions may be asked, such as the patient's name, where they live, the current date or day of the week, or season of the year to evaluate orientation. Disorientation is frequently associated with organic brain syndromes (e.g., dementia).(2)
Confusion is a behavioral state of reduced mental clarity, coherence, comprehension, and reasoning.(3
) Inattention and disorientation are the main early signs; however, as an acute confusional state worsens, there is deterioration of memory, perception, comprehension, problem solving, language, praxis, visuospatial function, and various aspects of emotional behavior, each identified with particular regions of the brain. Changes in a person's state of consciousness such as confusion, lethargy, and delirium may be caused by many medical conditions including fever, ischemia, trauma, or brain diseases. It may also be caused by suppression of cerebral function from extrinsic factors such as drugs or toxins. Additional potential causes include internal metabolic derangements such as hypoglycemia, azotemia, hepatic failure, or hypercalcemia; and any brainstem lesion that can cause damage to the reticular activating system (RAS). However, if confusion is a feature of a dementing illness, it will become chronic in nature and will manifest as having an effect primarily on memory as opposed to acute confusion. Sometimes what was thought to be a confused state may be more clearly defined as a single cortical deficit in higher mental function such as impaired language comprehension, loss of memory, appreciation of space, in which case each is defined by the dominant behavioral change rather than characterizing the state as confusion.
The confused patient is usually subdued, and not inclined to speak, and is inactive physically. Psychiatrists will sometimes interchange the terms of confusion and delirium, while neurologists tend to keep the two separate, generally using the term delirium to describe a patient who is in an agitated, hypersympathotonic, hallucinatory state, most frequently caused by drug or alcohol withdrawal, or hallucinogenic drugs.
Memory helps to test a patient's ability to recall both past and present information. Memory is generally considered the most common and the most important cognitive ability that is lost. Clinicians may test a patient's memory by asking questions about the history of their present illness or a recent meal. Additionally, they may ask a patient to remember three unassociated words, such as a color, a person's address, and an object, then, later in the interview, ask if the patient can recall what they were asked to remember. These are tests of present or short-term memory. Questions concerning family history, date of birth, and past factual information test a patient's past (distant) memory. Delirium, dementias, amnesia, Korsakoff's psychosis, and anxiety are conditions associated with an impaired memory.(4)
Dementias are neuropsychiatric disorders defined by widespread symptoms of memory loss and deficits in cognition and reasoning.(5) Dementia, sometimes considered to be synonymous with the lay term "senility", is not a part of the normal aging process, and reflects some underlying disease. A more simple definition of dementia is deterioration of cognitive abilities that impairs the previously successful performance of activities of daily living.(6) Accurate diagnosis of the underlying cause is essential for appropriate management, as well as an understanding of severity and prognosis.
The clinician also measures attention span and the ability to concentrate in evaluating cognitive function. This is most often accomplished by asking the patient to do a short series of problems such as sequentially subtracting seven from 100, or three from 30. Insight tests determine the patient's ability to recognize the importance of their illness or situation. When indicated, the clinician may also wish to test higher levels of intelligence. These tests evaluate the patient's command of language, fund of knowledge, abstract reasoning, and judgment.
The Diagnostic and Statistical Manual of Mental Disorders, fourth edition, (DSM-IV) provides a common language for mental health care practitioners to describe psychiatric disorders.(7) Common language is essential since there may be significant overlap in many diagnoses. The manual also provides the complete diagnosing criteria for each mental illness and the number of symptoms required to establish a diagnosis, as well as usual age of onset, clinical course, complications, predisposing factors, and prevalence. Another frequently used tool is the Mini-Mental Status Examination (MMSE), a 30-point series of test questions to measure cognitive function.
A discussion of cognitive function and the disorders that lead to loss of cognitive function includes a review of Alzheimer's disease. Alzheimer's disease is the most common cause of dementia, accounting for over 60 percent of all cases of late-life cognitive dysfunction.(8) Loss of memory is typically the patient's presenting complaint. Minor memory loss, sometimes called age-associated memory impairment, is a common complaint associated with normal aging and is not a cause for concern. However, if minor memory loss affects social or occupational functioning, or is noticed by friends and coworkers, patients should be encouraged to visit a neurologist for formal evaluation.(
9) Loss of memory as presented in patients with Alzheimer's typically includes an inability to extract and use previously learned information, activity, and experience. Patients are generally disturbed with their inability to recall recent events, or with their disorientation with time.
Another cause of decreased cognition that should be mentioned is dementias that occur as the result of dietary deficiencies.(10) A lack of thiamine is known to produce Wernicke's encephalopathy. Such a patient presents with malnutrition, confusion, ataxia, and diplopia. A severe lack of vitamin B12, folic acid or omega 3 fatty acids may cause, among other things, dementia due to damage to cerebral myelinated fibers. Deficiency of nicotinic acid (pellagra) and pyridoxine may cause spastic paraparesis, peripheral neuropathy, fatigue, irritability, and dementia. This syndrome has been seen in prisoner-of-war camps. To prevent cognitive impairment, researchers found that any frequency of moderate exercise reduced the risk of developing this condition.(11)
Toxicities known to produce dementias include narcotic poisoning, heavy metal intoxication, dialysis dementia (aluminum), and other organic toxins. Dementias associated with vitamin deficiencies or poisonings are potentially treatable.
The most common symptom of decreased cognitive function is a loss of memory. While some memory loss occurs in the normal aging process, it is a gradual process and generally involves things like forgetting phone numbers, people's names, or where objects have been placed. In dementia causing illnesses such as Alzheimer's disease, the process continually worsens until the patient is unable to perform normal activities of daily living.
In the early stages, patients may seem inattentive or disoriented. Patients that become confused are generally subdued, not inclined to speak, and physically inactive. As the disease progresses, patients have increasing difficulty with memory, perception, comprehension, problem solving skills, language skills, praxis, visuospatial functions, and various aspects of emotional behavior. In the final stages of dementia producing illnesses, the patient may lose the ability to coordinate muscle movement for walking, control the bowel or bladder, and may lose the ability to chew or swallow.
- Memory loss
- Disorientation (impaired
perception of time or direction, acquaintances, family, or self)
- Dysphasia (anomia, aphasia)
- Impaired calculation
- Impaired judgment or problem
- Behavioral or emotional problems
1. Ropper AH, Martin JB. Acute Confusional states and coma. In: Fauci AS, Braunwald E, Isselbacher KJ, et al, eds. Harrison's Principles of Internal Medicine, 14th ed. New York: McGraw-Hill; 1998:125-133.
2. Longe RL, Calvert JC. Mental Status Examination. In: Young LY, ed. Physical Assessment, A Guide for Evaluating Drug Therapy. Vancouver, WA: Applied Therapeutics Inc; 1994:3-3-3-5.
3. Ropper AH, Martin JB. Acute Confusional states and coma. In: Fauci AS, Braunwald E, Isselbacher KJ, et al, eds. Harrison's Principles of Internal Medicine, 14th ed. New York: McGraw-Hill; 1998:125-133.
4. Longe RL, Calvert JC. Mental Status Examination. In: Young LY, ed. Physical Assessment, A Guide for Evaluating Drug Therapy. Vancouver, WA: Applied Therapeutics Inc; 1994:3-3-3-5.
5. Crismon ML, Eggert AE. Alzheimer's Disease. In: DiPiro JT, Talbert RL, Yee GC, et al, eds. Pharmacotherapy, A Pathophysiologic Approach, 4th ed. Stamford, CT: Appleton & Lange; 1999:1065-1080.
6. Bird T. Memory loss and dementia. In: Fauci AS, Braunwald E, Isselbacher KJ, et al, eds. Harrison's Principles of Internal Medicine, 14th ed. New York: McGraw-Hill; 1998:142-150.
7. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 4th ed. (DSM-IV). Washington DC: American Psychiatric Press; 1994.
8. Eggert A, Crismon ML. Current concepts in understanding Alzheimer's Disease. Clin Pharm Newswatch. 1994;1:1-8.
9. Ropper AH, Martin JB. Acute Confusional states and coma. In: Fauci AS, Braunwald E, Isselbacher KJ, et al, eds. Harrison's Principles of Internal Medicine, 14th ed. New York: McGraw-Hill; 1998:125-133.
10. View Abstract: Gray GE. Nutrition and dementia. J Am Diet Assoc. Dec1989;89(12):1795-802.
11. View Abstract: Geda YE, et al. Physical exercise, aging, and mild cognitive impairment: a population-based study. Arch Neurol. Jan2010;67(1):80-6
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