Impairments in orientation, attention, and vigilance are common sequelae to brain damage, and regardless of the localization of brain pathology, these abilities are often compromised. When a patient is disoriented and unable to attend to ongoing events, there is usually severe pathology. In addition, inability to attend to ongoing stimuli makes the interpretation of neuropsychological tests of higher cognitive functions, such as intelligence or memory, difficult. Therefore, the assessment of orientation, attention, and vigilance is an integral part of all neuropsychological assessments and usually is performed first.
ORIENTATION TESTS: PERSONAL, TEMPORAL, AND SPATIAL
Standard bedside mental status examinations always assess orientation to person, time, and place. Usually this information is gathered from interviewing the patient in an open manner, and is not part of a standardized test. Many tests of cognitive function include questions assessing orientation, although they may not provide selective scores for orientation. Specific tests with orientation questions, or tests designed to assess orientation, are listed here.
Mini-Mental Status Examination (MMSE).y The MMSE includes questions that assess orientation to time ("What is today's date?" "Month?" "Day of the week?" "Year?") and orientation to place ("Where are you now?" "What state are you in?" "County?" "City?" "What is the name of this place?"). Each item is scored as pass or fail. Although the orientation section of the MmSE does not provide a separate score, a failure of two or more items is reflective of impaired performance.
Wechsler Memory Scale-Revised (WMS-R).y Although the majority of this test's items assess memory function, there is a subset of questions assessing orientation to person, place, and time. Failure of two or more items is considered impaired.
Temporal Orientation Test (TOT). y The TOT is designed to specifically assess orientation to time. The questions include knowledge of current hour and minutes, date, day of the week, month, and year. Errors are assigned negative scores depending on the amount of disorientation. The error score is subtracted from 100 and any score less than 95 is reflective of impaired performance.
Money Road Map Test (MRMT).y The MRMT assesses the ability of the patient to identify left and right directions at different orientations. The patient views a map on which the examiner traces a route. At each turn, the patient has to identify whether the examiner made a left or right turn. In order to correctly perform this test, patients must be able to mentally reorient to the perspective of the examiner and to different orientations of the route. If a patient makes more than 10 errors (out of 32 turns) his or her performance is considered impaired.
Finger Localization Test. y This test of personal orientation requires the patient to identify which finger has been stimulated by the examiner under visual guidance, and in the absence of visual input. A variant of this test is found in the Halstead-Reitan Battery, which assigns numbers to each finger of each hand, and requires the patient to identify which hand and which finger number has been stimulated in the absence of visual input.
Left-Right Orientation Test. y This test of left-right orientation requires the patient to display lateralized body parts (e.g., "show me your left hand"), identify laterality of the examiner's body (e.g., "point to my left hand"), and touch lateralized body parts of the examiner (e.g., "touch my left hand"). In order to correctly perform this task, the patient must be able to reverse personal orientation when confronted with identifying laterality of the examiner. The normative data for this test are very limited, but a cutoff score of four errors is suggestive of impaired left-right orientation.
Mental status tests are used to assess overall level of cognitive functioning. These tests are brief to administer and not very comprehensive. They tend to include a few questions on orientation, attention, memory, language, and sometimes praxis. Although mental status testing provides basic information on the integrity of most cognitive functions, the tests tend to lack sensitivity to detect mild cognitive impairment. In addition, most tests of mental status do not have normative data, so the effects of various demographic
variables (e.g., age, gender, education) are not known. Despite these limitations, the tests provide useful information, and some form of mental status testing should be a part of all neuropsychological assessments.
Mini-Mental Status Examination (MMSE).y In addition to the orientation questions listed above, the MMSE includes items assessing registration of information, recall of three words, attention and sequencing abilities (serial sevens, or spell word backward), naming, repetition, following spoken commands, writing, and copying. The test provides a general summary of cognitive function, but does not assess any cognitive domain in depth. The maximum score for the MMSE is 30, and a cutoff score of 24 is considered to indicate impaired performance.
Although the MMSE is the most commonly used mental status test, it has a number of problems. First, one must accept the basic limitation of any screening exam. Since the test has a limited number of questions, adequate testing of cognitive function is not possible. Practically, however, the MMSE score is used as an indicator of intact or impaired performance. The cutoff score of 24 is associated with relatively high false-negative rates (test indicates absence of impairment when impairment is present) and relatively high false-positive rates (test indicates impairment when no impairment is present). Additionally, MMSE score is affected by education, race, and gender. Despite these limitations, the MMSE provides a "quick-and-dirty" assessment of overall cognitive function, and in most contexts a score of 22 or lower is considered an accurate mark of clinically significant cognitive impairment.
Mental Status Questionnaire (MSQ).y The MSQ is composed of items assessing orientation to time and place and ability to name the current and past presidents of the United States. The maximum score of the MSQ is 10 errors, and individuals making more than 2 errors are considered moderately impaired. This cutoff score suffers from the same limitations as the MMSE.
Short-Portable Mental Status Questionnaire (SPMSQ). y The advantage of the SPMSQ over the MMSE and MSQ is that normative data have been gathered to aid in interpreting performance. This represents a major advantage to the SPMSQ. However, the test still suffers from problems with false-positives and false-negatives (particularly in patients with mild cognitive impairment).
Testing attention involves assessment of the ability to attend to stimuli, the ability to focus attention on selected stimuli, and ability to inhibit attention to inappropriate stimuli. Tests of vigilance also require the active updating of information in an ongoing display requiring attention. All of these abilities are essential to intact cognitive function. Information on attention and vigilance should be reported in all neuropsychological assessments
Simple Reaction Time (SRT). SRT tasks require the patient to respond, as quickly as possible, to a stimulus. The time the patient takes to respond (RT) is usually measured in milliseconds. Slowed RT is one of the most sensitive measures of impaired cognitive functioning, but individual data are difficult to interpret owing to the large inter- and intrapatient variability.
Choice Reaction Time (CRT). There are many measures of CRT, but all follow a basic paradigm: the patient is required to respond to one stimulus but to not respond to another. An example of this is the Continuous Performance Test, in which the patient is asked to respond, as quickly as possible, to a rare stimulus that is embedded in a stream of ongoing similar stimuli. These tests assess the patient's ability to maintain attention and vigilance for the target stimulus and the ability to inhibit responses to the nontarget stimuli. Individual differences are difficult to interpret owing to large inter- and intrapatient variability.
Span Tests. Tests of span capacity are a more standard form of assessing attention and vigilance than reaction time measures. In addition to assessing attention, span tests also require some form of short-term memory. However, forward span tests (discussed below) are thought to be more reflective of attentional abilities. When backward span (repeating a sequence heard in the reverse order of presentation) is used, different cognitive processes are required, including working (or short-term) memory, so that the test is no longer a pure measure of attention.
The most commonly used span measures are the Digit Span tests from the WAIS-R and the Wechsler Memory Scale-Revised (WMS-R). y In these tests, patients listen to random sequences of numbers presented in increasing length, and immediately repeat each sequence. Two trials at each span length are presented, and maximum span is the number of digits the patient can correctly repeat on at least one trial. Average performance on this measure is considered to be between five and nine digits. y A variant of this task uses letters instead of digits. The interpretation of letter span performance is nearly identical to digit span performance.
Both digit and letter span are measures of verbal ability. A nonverbal span measure is the Corsi Block Test. y In this test the patient is presented with an array of nine blocks arranged in a random order. The examiner touches blocks in sequences of increasing length. The patient is required to reproduce the sequence at each length. As in the digit span test, two trials are given at each sequence length and maximum span is the number of blocks the patient taps in the correct order on at least one trial. Average performance on this test is similar to digit span.
Attention/Concentration Subtest of the WMS-R. y One subtest of the WMS-R (discussed below) is the Attention/Concentration Index. This composite measure of attention and concentration includes test performance on digit span, visual span (a variant of the Corsi Block Test), and three measures of speeded performance. One major advantage to the use of this measure is that it has good normative information (see WMS-R description later) and is converted to age-adjusted standard scores with a mean of 100 and a standard deviation of 15. The use of these standard scores allows for comparisons across many different neuropsychological tests (e.g., WAIS-R).
Paced Auditory Serial Addition Test (PASAT). y The PASAT is a test requiring attention and vigilance. In this test, the patient listens to a tape recording of digits presented one at a time. The task for the patient is to add each number to the one immediately preceding it. For example, the recording might present the numbers 1, 7, 5, 4. The patient adds the first two numbers (1 + 7) and
responds with the number 8. The patient then adds the second two numbers (7 + 5) and responds with the number 12. The patient then adds the third two numbers (5 + 4) and responds with the number 9. This continues for a total of 61 numbers presented in a random order. The test can be given at different rates of presentation ranging from a slow rate of one number every 2.4 seconds to the fastest rate of one number every 1.2 seconds. This test assesses attention and vigilance because the patient is required to not only attend to the relevant stimuli (numbers) but also be vigilant to changes in the ongoing presentation. This is an extremely sensitive measure of vigilance. However, the test also involves working or short-term memory because the patient must "hold" in short-term memory the preceding number while formulating a response. Although this is a sensitive test, the norms for interpretation are limited.
Digit Symbol.y This subtest of the WAIS-R presents the patient with a row of numbers one through nine, each paired with nonsense symbols (e.g., inverted T). Below this key are empty boxes with numbers above each box. The patient is required to transcribe the symbol corresponding to the number above the box as quickly as possible. This measure requires focused attention and switching behavior between the key and the target boxes. One advantage of this test is the extensive WAIS-R norms available on performance expectations. This test also requires motoric speed and may not be appropriate for patients with marked motor impairment. A variant of this test is available that requires a verbal response only, thus decreasing motoric demands. y
Trail Making Test.y There are two forms to this test: Trail Making Tests A and B. Trail Making Test A provides an assessment of complex attention. This test requires the patient to connect randomly positioned numbered circles in numeric order as quickly as possible. Form B presents the patient with numbered circles and circles with letters. The patient is required to connect the circles in numeric and alphabetic order as quickly as possible, alternating between numbers and letters. Both Forms A and B require focused attention for successful performance. In addition, Form B requires the patient to switch cognitive sets between numbers and letters. Both forms of the Trail Making Test are highly dependent upon motoric speed, and may not be appropriate for patients with marked motor impairment (e.g., Parkinson's disease).
Cancellation Tests. Another useful test of attention and vigilance is that which requires the patient to seek a selected stimulus out of a background of similar stimuli. One such measure is the Letter Cancellation Testy where the patient is required to cancel selected letters, designs, or words from a background of nontarget letters, designs, or words. Because cancellation tasks are timed measures requiring motoric responses, they may not be appropriate for patients who have marked motor impairment.
CLINICAL SITUATIONS FOR TESTING ORIENTATION, ATTENTION, AND VIGILANCE
Neuropsychological data on orientation, attention, and vigilance abilities are useful in defining dysfunction in all levels of neurological functioning. Such tests are particularly useful in cases of toxic and metabolic abnormalities (see Ch.apteL.3.8 and Ch§pter3.9. ), which affect level of consciousness (see C.h.ap.te.L.1), sleep/wake cycles (see ChapteL2 ), and memory functioning (see Chapters ). In addition, attentional testing is essential for patients who evidence neglect or dyspraxia (see Chapt§Li4. ). Useful information on patients with psychiatric presentations is also provided when attention is assessed ( „Chapters ). When requesting neuropsychological assessment of orientation, attention, and vigilance, it is important to request testing on all aspects of attention and vigilance including simple attention, focused attention, and set-shifting.
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