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Assessment of Patients with Neurological Disorders
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16 Assessment of Patients with Neurological Disorders ANTHONY FEINSTEIN
INTRODUCTION The assessment of patients with neurological disorders presents a particular set of challenges for mental health professionals and students. With the emphasis shifting from the phenomenological components of psychiatric evaluation to the cognitive assessment, you will require additional skills that complement the standard mental state examination. Furthermore, ancillary investigations such as neuroimaging take on added relevance in the presence of neurological disease and, together with a detailed cognitive examination, may provide valuable insights that help account for behavioral abnormalities. This chapter will outline the basic principles you must follow in completing a cognitive examination, provide a template for the assessment, and highlight common misconceptions and diagnostic pitfalls. Finally, the utility of neuroimaging in conjunction with cognitive testing will be briefly discussed.
ness; (2) It may furnish valuable clues as to cerebral localization, which can then be explored further with the cognitive assessment and neuroimaging; (3) It can provide pointers to whether the pathological process is essentially cortical or subcortical, with implications for the cognitive profile of the patient. With the neurological examination completed, the following points should be adhered to when assessing cognition: ■
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There are some essential principles that must be followed for the assessment to retain validity. First and most obviously, if a neurological disorder is present or suspected, the patient must initially be seen by a neurologist. A neurological examination may not necessarily provide the diagnosis at that point, but notwithstanding will facilitate the subsequent mental state assessment in a number of important ways: (1) It will provide confirmation of neurological illness, an essential prerequisite in the case of patients whose primary difficulty may be a somatoform ill-
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The cognitive assessment follows a standard mental state examination that addresses the patient’s appearance and behavior, mood and affect, thought form and content, perceptual experiences, judgement, and insight. Patients with a neurological disorder may not be aware of any deficits, be they physical or cognitive. This “anosognosia” means they may not be able to direct you to the presence of any problems. Fatigue may frequently be an issue in cognitive testing. In more acutely ill patients admitted to hospital, testing may therefore require repeat sessions of short duration. In performing a cognitive assessment, you should always be aware of the patient’s level of education and cultural background and take these factors into account when interpreting the results. You should stick to a set order of testing. Thus, your examination proceeds sequentially through the following areas: consciousness and orientation, attention and concentration, language, memory, visuospatial and constructional abilities, and finally, frontal lobe tasks. Failure to follow this sequence can lead to difficulties when interpreting data. For example, if memory testing 227
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precedes the language assessment in an aphasic patient, deficits in recall may represent a failure to understand or respond correctly to a question instead of a failure in memory. Furthermore, within each cognitive domain you should start with the easiest questions and, depending on the response, move on to the next level of complexity. This basic premise is followed throughout the protocol outlined in further discussion. Access to an informant is often invaluable as an adjunct to the assessment, providing additional insight into the presence and severity of deficits. A cognitive assessment by itself is not diagnostic of any disorder. It is always completed as an adjunct to the history and formal mental state examination and complements other ancillary investigations like neuroimaging and biochemical indices. The cognitive assessment lacks the sensitivity of formal neuropsychological testing. However, the latter is more time consuming, expensive, and often not readily available. Guidelines for deciding whether a patient needs more detailed testing are provided in the Neuropsychological Testing section to follow.
THE COGNITIVE ASSESSMENT There is a plethora of tests from which to chose when it comes to completing cognitive testing. Although the choice is most often dictated by the preference of examiner, tests do vary in their sensitivity. A useful rule of thumb is that tests that tap into more than one aspect of cognition are particularly useful in teasing out deficits. A good example is the Controlled Oral Word Association Test (COWAT)1, also known as the Verbal Fluency or FAS test. This paradigm probes a patient’s attention, the ability to sustain attention (termed vigilance), and semantic memory, which collectively enhances its utility as a screening measure for cognitive deficits. Before beginning testing, you must note the patient’s age, her level of education, the time of day, and cerebral dominance. The latter will lie along a continuum, but for the purpose of this examination asking the patient whether she is right- or left-handed will suffice.
Premorbid IQ In patients who are fluent in English, this can be assessed rapidly with a reading test, such as the National Adult Reading Test.2 This consists of a list of 50 words that range from easy to difficult in terms of the correct pronunciation. All the patient has to do is read out the words while you score the responses according to phonetic accuracy. The
test is based on the premise that reading skills are fairly resilient to the deleterious effects of an acquired brain disorder and will therefore provide a marker for what the intellect was like before the patient took ill. Given the tests cultural bias, different versions have been developed for British and American subjects.
Consciousness In a general hospital setting, a psychiatric assessment is not infrequently requested for a patient whose level of consciousness is reduced. Under these circumstances, testing higher-order cognitive functions like those subserved by the frontal lobes will not be possible. However, some information may be still gleaned from patients whose consciousness is impaired. Here the help of an informant like a nurse or family relative is useful. Issues you should consider include the following: ■ ■ ■
Is the patient continent? Does the patient spontaneously open her eyes? Does the level of consciousness fluctuate according to time of day?
Such simple assessments can shed light on the degree to which consciousness is impaired, thereby providing a marker to judge future improvement or deterioration. Fluctuations according to time of day may suggest a delirium, particularly if a patient’s mental state worsens as nightfall approaches.
Orientation This is tested in three domains: time, place, and person. In keeping with principles outlined above, the sequence of questions moves from easy to more difficult. ■ ■ ■
Time: year ± month ± weekday ± time of day Place: country ± province (state) ± city ± building Person: name ± age ± date of birth
Attention and Concentration There are many different ways of testing these cognitive abilities. There may have been clues from the history that the patient is experiencing difficulties in these areas, for example, an inability to watch a television program from beginning to end, or similar difficulties concentrating on a newspaper article. Two ways to probe attention are as follows: 1. Ask the patient to give the months of the year in reverse order. 2. Ask the patient to serially subtract 7 from 100.
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For both these tests, record the responses and encourage the patient to keep going until no further responses are possible. In one of the most widely cited of all psychometric tests, namely the Mini-Mental State Examination,3 the serial 7s test is done for five subtractions only. Although undoubtedly still useful, if you bail out early in this fashion, it is often not possible for you to comment on a patient’s ability to sustain attention over a more prolonged period of time, the attribute of vigilance. Thus, it is important with the serial 7 test for you to encourage the patient’s perseverance while recording the patient’s responses. A third useful way to assess attention is the Digit Span test.4 This test makes up one of the subtests of the Wechsler Adult Intelligence Scale and is considered a sensitive index of cerebral dysfunction in a patient with an acquired brain insult. In this test, a series of digits is presented at intervals of one per second. You start by calling out three digits and asking the patient to repeat them in the forward direction. If the correct answer is obtained, the process is repeated with four digits, then five digits, etc. Patients are allowed two chances at each level. If they correctly repeat the digits on first hearing, the examiner moves on to the next level. Once a ceiling is reached for the forward repetition of digits (usually seven digits), the process is repeated, but this time the patient is asked to repeat the digits in the reverse order. For the digit span backward, you start once again with a sequence of three digits and build up as described above until a ceiling of six digits is reached. Patients are once again allowed two chances at each level. Should a patient fail both attempts at one level, the score is taken from the previous level successfully completed. There are published, age-corrected normative data for the Digit Span test.5 It is strongly recommended that you have the series of digits written out before testing begins.
Language Disorders of language can be broadly divided into expressive (fluent) and receptive (nonfluent) difficulties. In a Broca-type aphasia (dominant inferior frontal lobe pathology), patients have difficulty expressing themselves, whereas in a Wernicke-type aphasia (dominant posterior superior temporal lobe lesion), the problem is primarily one of comprehension. A conduction aphasia occurs when lesions interrupt the arcuate fasciculus, the tract joining Broca’s and Wernicke’s area. The resultant speech is fluent, with many paraphasic errors that are mainly phonemic (see further discussion). Examining language involves four stages: ■
Assessment of spontaneous speech during conversation and picture description
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Naming ability Comprehension Repetition
During spontaneous speech by the patient, look for the following: articulation; fluency; syntax, that is, the correct use of grammar (agrammatism is associated with Broca’s aphasia); paraphasic errors or word substitutions that can either be semantic (e.g., calling a pen a pencil) or phonemic (e.g., calling a pen a pin); word-finding problems that manifest as circumlocutions (e.g., when asked to name a pen, the patient hesitates and then describes the object instead [“something to write with”]); and finally, the melodic flow to speech, which is termed prosody. When testing naming ability, you should point to some common everyday objects like a shoe, cuff, watch, strap, buckle, etc. A chart with pictures of less common objects can then be used to challenge the patient further. Comprehension can be tested at four levels. First, can the patient keep a conversation going? Second, can the patient respond to commands that do not require a verbal response (e.g., ask the patient to point to the door, ceiling, and floor)? Third, can the patient comprehend a sentence such as “What color is grass?” or “What do we cut bread with?” Finally, if all three levels have been successfully completed, you should move on to testing concept comprehension with questions such as, “What do we call the man who works in a fancy restaurant and creates delicious meals?” Repetition must be tested because it gives clues to the presence of a transcortical aphasia. Here, the lesion lies outside the primary language areas (i.e., Broca’s, Wernicke’s, and the arcuate fasciculus). To test repetition, begin with one-syllable words (e.g., gun, boat) and then move through two (e.g., prosper, happy), and three (e.g., enable, postulate) syllables. Finally, ask the patient to repeat a phrase such as “no if’s, and’s or but’s.” In patients with a conduction aphasia, repetition is severely affected. In a transcortical motor aphasia, however, a patient presents with expressive difficulties as in a Broca-type picture, except repetition to various degrees is spared. In the case of a transcortical sensory aphasia, the patient resembles a Wernicke-type picture, but with repetition once again intact.
Reading Reading is a skill that most often matches language. Ask the patient to read aloud, and then test the ability to comprehend what has been written. For example, hand the patient a piece of paper that has the sentence, “Close your eyes,” written on it. On a more complex level, give the patient a paragraph of text to read aloud, and then test
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whether the content has been understood. Pure alexia occurs but is rare.
Writing Ask the patient to write a sentence spontaneously and then to write a dictation from you. Agraphia, suggesting a lesion of the angular gyrus, may occur with acalculia, rightleft disorientation, and finger agnosia, the four features comprising the Gerstmann syndrome.
In addition to the above schematic representation, there are other terms that are frequently encountered. Memory may rely on recall (the absence of cues) or recognition (cues are present). Furthermore, anterograde memory refers to a patient’s ability to acquire or lay down new memories, whereas retrograde memory refers to the ability to retrieve facts and events from the past. The following template provides a method to assess memory: ■
Calculations Calculations should be tested verbally and in writing. Assess addition, subtraction, multiplication, and division. Examples illustrating the complexity would be as follows: 12 + 37; 45 − 16; 9 × 12; 64 ÷ 4.
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Praxis
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Apraxia refers to the inability to perform skilled motor movements in the presence of normal comprehension, muscle strength, and coordination. A distinction is made between buccofacial and limb apraxia. To test praxis, ask the patient to demonstrate how he would blow out a match, salute like a soldier, and brush his teeth. If a patient cannot follow these commands, test his ability to imitate you performing these movements.
Memory The plethora of terms describing various aspects of memory may at first glance appear confusing. One useful approach to disentangling the terminology is as follows: 6 Memory can be subdivided into that which is effortful (known as explicit or declarative) and that which is not (called implicit or procedural). The latter cannot be tested at the bedside and involves memory that arises from conditioning, priming, and the acquisition of motor skills. Explicit memory, on the other hand, demands conscious effort and can be divided according to whether it is short term or long term. There is no absolute time distinction between the two. Rather, short-term memory should be thought of as immediate or working memory, or to use a computer analogy, the memory that is held “online.” It can be subdivided further into verbal and visual components. Similarly, longterm memory (which by exclusion is all that is not immediate) can be divided into verbal and visual. Longterm memory may, in turn, be divided into semantic (i.e., factual information) and episodic (i.e., personally experienced and temporally specific).
Short-term verbal memory can be tested by asking a patient to remember a name and address (seven facts in all). Record the number of trials (up to five) that it takes the patient to do this. This simple test provides a marker of anterograde memory. Short-term visual memory can be tested by asking a patient to remember a series of shapes. These may be complex, as in the Rey-Osterrieth Test, or simpler, as in a series of checkerboard designs. Long-term verbal and nonverbal memory can be tested by asking the patient to recall the above information at the end of the entire cognitive examination. Retrograde amnesia is assessed with questions that probe semantic and episodic memory. Examples of the former are a series of general knowledge questions (e.g., “What is the capital of Canada?” “Who is the Prime Minister of the United Kingdom?”), whereas episodic memory can be tested by autobiographical recall.
Right-Hemisphere Skills The assessment of right-hemisphere skills centers on various aspects of neglect and agnosia in addition to constructional and spatial abilities. Different types of agnosia are tested as follows: ■
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Object recognition (visual agnosia): Ask the patient to identify common objects like keys, pen, etc. Finger agnosia: Ask the patient to name and move various fingers. Disturbance of identification body parts (autotopagnosia): Ask the patient to move on command and name various body parts. Estimating distances (visuospatial agnosia): Ask the patient which of two objects in the examination room is nearer. Facial recognition (prosopagnosia): Ask the patient to identify well-known personalities (Figure 16-1).
Personal neglect can be tested by asking the patient to discriminate left from right and thereafter various mixed combinations by instruction the patient to “touch your left foot with your right hand” and “touch your left ear with
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Frontal Lobe Tasks Before discussing a list of tests that are sensitive to frontal lobe function, a few comments on the anatomy of this region are called for. Although the prefrontal cortex is the area that subserves many aspects of cognition, an appreciation of other frontal areas is also necessary in completing an assessment: ■
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The motor cortex lies anterior to the central sulcus, and lesions here can result in a contralateral paralysis or paresis. The premotor system is important for integrating motor and sensory function with connections to the primary sensory cortex, somatosensory cortex, primary motor cortex, thalamus, and caudate nucleus. Lesions here may give rise to apraxia and difficulties with fine coordination. The frontal eye fields control conjugate eye gaze. Broca’s area in the inferior frontal lobe controls the expression of speech with lesions resulting in a nonfluent aphasia.
The prefrontal cortex, pivotal in regulating mood, behavior, and cognition, contains three discrete neural circuits that run in parallel to the basal ganglia before looping back to prefrontal areas of origin: ■
FIGURE 16-1 Face recognition. ■
the ring finger of your right hand.” Hemispatial neglect can also be tested by instructing the patient to fill in the numbers on a blank clock face and mark the time at 10 minutes past 11. Constructional ability can be tested by asking the patient to copy a series of shapes that increase in complexity from two to three dimensions (Figure 16-2).
FIGURE 16-2 Constructional ability test.
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The dorsolateral prefrontal cortex (DLPFC) is linked to spatial and conceptual reasoning processes and plays an important role in regulating verbal fluency, attention, and certain aspects of memory. The ventral prefrontal cortex (VPFC) is central to behavior regulation and emotional control, including stimulus reward associations. The anterior cingulate prefrontal cortex (ACPFC) is pivotal in controlling motivation. Lesions here can produce varying degrees of apathy ranging from mildly reduced motivation to akinetic mutism.
The fact that these circuits run to subcortical areas explains an important clinical observation, namely that nonfrontal lesions may produce typical frontal-type behaviors through a process of disconnection (e.g., a lesion in the VPFC may give rise to disinhibited, socially inappropriate behavior characterized by an indifference to adverse consequences). Given that the VPFC circuit starts in the inferior aspect of the prefrontal cortex before relaying sequentially in the caudate nucleus, globus pallidus, substantia nigra, subthalamic nuclei, and finally certain thalamic nuclei before returning to the inferior prefrontal cortex, a lesion anywhere along this pathway may alter behavior as described previously.
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There are a number of bedside frontal lobe test batteries available.7,8 They comprise a mixture of tests that probe attention, verbal fluency, semantic memory, abstract thinking, and cognitive flexibility, the last of these referring to an ability to inhibit or modify verbal and motor responses according to changing instructions or circumstances. All these cognitive functions can be tested, and the results should be combined with behavioral observations that better reflect the functioning of the VPFC because this region defies neat psychometric correlations. Some commonly used tests that are sensitive to the functional integrity of the prefrontal cortex include the following: ■
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Initiation tasks: The most widely used is the COWAT or letter fluency test.1 Here the patient is required to produce orally as many words as possible beginning with the letters F, A, and S. The patient is allowed 1 minute per letter, and at the end of the test the person’s totals are added to give the final score. Patients are instructed not to use proper names (e.g., Sydney, Simon, Sue) or the same word with different endings (e.g., fun, funnier, funniest). Like the Digit Span test, there are published normative data for the COWAT. Analogous tests: An analogous test calls for the patient to name as many four-legged animals as possible in 1 minute. Abstraction ■ Abstraction ability is tested by asking the patient to interpret the proverb, “A bird in the hand is worth two in the bush.” The examiner must be sensitive to education and cultural issues here. ■ A second way to test abstract thinking is to ask the patient a series of questions: “In what way are the following paired items similar and different . . .” ● “Car and bus?” ● “Apple and pear?” Response inhibition and shift testing: This can be tested as follows: ■ Go–No Go test: Ask the patient to raise one index finger in response to one tap on the table. The patient is not to respond when you tap twice. The patient should not see you tap, so use the undersurface of the table for this. Having completed 10 trials, switch instructions (e.g., the patient must not respond to one tap, but must raise an index finger when you tap twice). Failure to inhibit responses when none are called for is deemed pathological. ■ Alternating hand movements: In this test, one had forms a fist while the other has fingers extended, palm facing toward the patient. Alternate these positions between the right and left hand three times, then ask the patient to repeat what you have just done.
The Luria three-step procedure: This calls for you to perform a sequence of movements with the right hand, using the left hand as a base with fingers extended and palm pointing upward. ● Step 1: Fist strikes palm. ● Step 2: Edge of hand with fingers extended strikes palm. ● Step 3: Palm strikes palm. Repeat this three times, then ask the patient to reproduce what you have just done. The patient should perform the sequence five times. Then ask the patient to repeat the process with the right hand acting as the base and the left hand completing the three-step sequence. ■
NEUROPSYCHOLOGICAL TESTING Although the cognitive examination outlined above has significantly greater sensitivity than screening instruments such as the Mini-Mental State Examination,3 it still falls short of a detailed neuropsychological assessment. The latter, however, is time consuming and expensive. Furthermore, many clinicians do not have ready access to such a service. All of this raises the question of when to refer a patient with a neurological illness to a neuropsychologist. Indications for undertaking a formal neuropsychological assessment include the following: ■
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Colleagues or superiors report a decline in a person’s work performance, or the person reports subjective cognitive difficulties in the absence of a prominent mood, substance use, or anxiety disorder. A patient is applying for a disability settlement. A patient is about to enter a treatment trial that may improve (or harm) cognition. A cognitive baseline is therefore required. A patient is entering a cognitive rehabilitation program. Once again, a cognitive baseline is needed to determine relative strengths and weaknesses.
CORTICAL VERSUS SUBCORTICAL DEMENTIA The cognitive profile in patients with neurological disorders can differ according to whether the burden of disease is cortical or subcortical. Senile dementia of the Alzheimer type may be regarded as the quintessential cortical dementing illness, whereas Huntington’s and Parkinson’s diseases represent typical subcortical gray-matter dementias, and multiple sclerosis represents the white-matter equivalent. It is important to emphasize that these
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cortical/subcortical distinctions are not neatly defined anatomical divisions; rather, they reflect differing functional profiles. Thus, apraxia, agnosia, and aphasia are all markers of cortical rather than subcortical cognitive abnormalities. On the other hand, one of the hallmarks of subcortical deficits is delayed information-processing speed. Therefore, patients will have difficulty with timed tasks such as the COWAT. Although both groups may display prominent memory problems, cortically based disorders may result in relatively greater difficulty acquiring new information, whereas in patients with a greater subcortical burden, memory deficits may be more pronounced when retrieval is challenged. In more advanced disease, these distinctions can become blurred. Nevertheless, clinicians must remember that a widely used brief cognitive screening measure like the Mini-Mental State Examination is geared toward cortical cognitive deficits and lacks sensitivity for predominantly white-matter dementias like multiple sclerosis.
NEUROIMAGING Brain imaging can be either structural (e.g., computed tomography [CT], magnetic resonance imaging [MRI]) or functional (e.g., single photon emission computed tomography [SPECT], positron emission tomography [PET], functional MRI [fMRI]). For clinicians, CT, MRI, and SPECT are the commonly available modalities. PET and fMRI are still largely limited to research protocols. MRI has many advantages over CT when it comes to structural brain imaging. These include greater anatomical sensitivity, improved visualization of cerebral white matter, and the ability to image the posterior fossa and medial temporal lobe structures without bone artefact. MRI technology does not make use of radiation, thereby facilitating serial studies. Finally, the brain can be easily scanned in the axial, coronal, and sagittal planes. CT, on the other hand, is cheaper and, in the early stages after traumatic brain injury, may be preferred given the isodense properties of blood. Neuroimaging is an important ancillary investigation for the following reasons: ■ ■
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It may help the neurologist diagnostically. It may provide important clues to the neurologist and psychiatrist concerning cerebral localization. However, here is it important to remember that a lesion at one anatomical location may exert functional effects that are removed from it, a process called diaschisis. It may provide clues as to why a patient’s behavior has altered. In this regard, it forms one part of a workup that starts with history-taking and proceeds through the neurological and mental state examinations, detailed
cognitive assessment, and other investigations (e.g., biochemical, electroencephalogram) if pertinent. What a clinician is looking for here is a confluence of findings. ■ One example of a clinical situation in which all the data come together neatly is as follows: The history suggests stroke; the neurological examination confirms a right-sided weakness; cognitive assessment reveals an expressive aphasia; MRI shows a left frontal hemorrhage; and SPECT demonstrates hypoperfusion in the area of the lesion. In this example, neuroimaging is essentially confirmatory. However, another common clinical situation where neuroimaging carries added diagnostic weight is as follows: The history reveals subtle personality change characterized by mildly inappropriate social behavior; neurological examination is normal; so too is the formal mental state; the cognitive assessment demonstrates mildly reduced verbal fluency (e.g., fewer than expected words on the FAS test); MRI shows mild frontal atrophy; and SPECT displays moderately severe frontal hypoperfusion. The confluence of the history and neuroimaging findings points strongly toward a diagnosis of fronto-temporal dementia.
CONCLUSIONS This chapter has provided a template for the psychiatrist, resident, and medical student to use in the assessment of patients with neurological illness. Given the high prevalence of cognitive deficits in neurological disorders, completing a clinically based cognitive assessment is mandatory to any comprehensive assessment. Furthermore, the information obtained is of considerable practical importance, for there are data linking deficits to many other real-world difficulties patients experience. These range from the workplace to relationships to the basic activities of daily living, all of which adversely impinge on quality of life. Completing an examination as outlined in this chapter will therefore not only enhance the diagnostic process, but will also assist in determining effective treatment and rehabilitation strategies.
REFERENCES 1. Benton AJ, Hamsher K, Sivan AB: Multilingual aphasia examination, Iowa City, IA, 1983, AJA Associates. 2. Nelson HE: National Adult Reading Test (NART): test manual, Windsor, England, 1982, NFER Nelson. 3. Folstein MF, Folstein SE, McHugh PR: “Mini-Mental State”: a practical method for grading the cognitive state of patients for the clinician, J Psychiatric Res 12:189–198, 1975.
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4. Wechsler D: Wechsler adult intelligence scale–revised, New York, 1981, Psychological Corporation. 5. Spreen O, Strauss E: A compendium of neuropsychological tests, ed 2, New York, 1998, Oxford University Press. 6. Hodges JR: Cognitive assessment for clinicians, Oxford, England, 1994, Oxford University Press, pp 5–19.
7. Dubois B, Slachevsky A, Litvan I, Pillon B: The FAB: a frontal assessment battery at bedside, Neurology 55:1621–1626, 2000. 8. Ettlin TM, Kischka U, Beckson M, et al: The frontal lobe score: part 1. Construction of a mental status of frontal systems, Clin Rehabil 14:260–271, 2000.
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16 Assessment of Patients with Neurological Disorders ANTHONY FEINSTEIN
INTRODUCTION The assessment of patients with neurological disorders presents a particular set of challenges for mental health professionals and students. With the emphasis shifting from the phenomenological components of psychiatric evaluation to the cognitive assessment, you will require additional skills that complement the standard mental state examination. Furthermore, ancillary investigations such as neuroimaging take on added relevance in the presence of neurological disease and, together with a detailed cognitive examination, may provide valuable insights that help account for behavioral abnormalities. This chapter will outline the basic principles you must follow in completing a cognitive examination, provide a template for the assessment, and highlight common misconceptions and diagnostic pitfalls. Finally, the utility of neuroimaging in conjunction with cognitive testing will be briefly discussed.
ness; (2) It may furnish valuable clues as to cerebral localization, which can then be explored further with the cognitive assessment and neuroimaging; (3) It can provide pointers to whether the pathological process is essentially cortical or subcortical, with implications for the cognitive profile of the patient. With the neurological examination completed, the following points should be adhered to when assessing cognition: ■
■
■
BASIC PRINCIPLES OF COGNITIVE TESTING ■
There are some essential principles that must be followed for the assessment to retain validity. First and most obviously, if a neurological disorder is present or suspected, the patient must initially be seen by a neurologist. A neurological examination may not necessarily provide the diagnosis at that point, but notwithstanding will facilitate the subsequent mental state assessment in a number of important ways: (1) It will provide confirmation of neurological illness, an essential prerequisite in the case of patients whose primary difficulty may be a somatoform ill-
■
The cognitive assessment follows a standard mental state examination that addresses the patient’s appearance and behavior, mood and affect, thought form and content, perceptual experiences, judgement, and insight. Patients with a neurological disorder may not be aware of any deficits, be they physical or cognitive. This “anosognosia” means they may not be able to direct you to the presence of any problems. Fatigue may frequently be an issue in cognitive testing. In more acutely ill patients admitted to hospital, testing may therefore require repeat sessions of short duration. In performing a cognitive assessment, you should always be aware of the patient’s level of education and cultural background and take these factors into account when interpreting the results. You should stick to a set order of testing. Thus, your examination proceeds sequentially through the following areas: consciousness and orientation, attention and concentration, language, memory, visuospatial and constructional abilities, and finally, frontal lobe tasks. Failure to follow this sequence can lead to difficulties when interpreting data. For example, if memory testing 227
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precedes the language assessment in an aphasic patient, deficits in recall may represent a failure to understand or respond correctly to a question instead of a failure in memory. Furthermore, within each cognitive domain you should start with the easiest questions and, depending on the response, move on to the next level of complexity. This basic premise is followed throughout the protocol outlined in further discussion. Access to an informant is often invaluable as an adjunct to the assessment, providing additional insight into the presence and severity of deficits. A cognitive assessment by itself is not diagnostic of any disorder. It is always completed as an adjunct to the history and formal mental state examination and complements other ancillary investigations like neuroimaging and biochemical indices. The cognitive assessment lacks the sensitivity of formal neuropsychological testing. However, the latter is more time consuming, expensive, and often not readily available. Guidelines for deciding whether a patient needs more detailed testing are provided in the Neuropsychological Testing section to follow.
THE COGNITIVE ASSESSMENT There is a plethora of tests from which to chose when it comes to completing cognitive testing. Although the choice is most often dictated by the preference of examiner, tests do vary in their sensitivity. A useful rule of thumb is that tests that tap into more than one aspect of cognition are particularly useful in teasing out deficits. A good example is the Controlled Oral Word Association Test (COWAT)1, also known as the Verbal Fluency or FAS test. This paradigm probes a patient’s attention, the ability to sustain attention (termed vigilance), and semantic memory, which collectively enhances its utility as a screening measure for cognitive deficits. Before beginning testing, you must note the patient’s age, her level of education, the time of day, and cerebral dominance. The latter will lie along a continuum, but for the purpose of this examination asking the patient whether she is right- or left-handed will suffice.
Premorbid IQ In patients who are fluent in English, this can be assessed rapidly with a reading test, such as the National Adult Reading Test.2 This consists of a list of 50 words that range from easy to difficult in terms of the correct pronunciation. All the patient has to do is read out the words while you score the responses according to phonetic accuracy. The
test is based on the premise that reading skills are fairly resilient to the deleterious effects of an acquired brain disorder and will therefore provide a marker for what the intellect was like before the patient took ill. Given the tests cultural bias, different versions have been developed for British and American subjects.
Consciousness In a general hospital setting, a psychiatric assessment is not infrequently requested for a patient whose level of consciousness is reduced. Under these circumstances, testing higher-order cognitive functions like those subserved by the frontal lobes will not be possible. However, some information may be still gleaned from patients whose consciousness is impaired. Here the help of an informant like a nurse or family relative is useful. Issues you should consider include the following: ■ ■ ■
Is the patient continent? Does the patient spontaneously open her eyes? Does the level of consciousness fluctuate according to time of day?
Such simple assessments can shed light on the degree to which consciousness is impaired, thereby providing a marker to judge future improvement or deterioration. Fluctuations according to time of day may suggest a delirium, particularly if a patient’s mental state worsens as nightfall approaches.
Orientation This is tested in three domains: time, place, and person. In keeping with principles outlined above, the sequence of questions moves from easy to more difficult. ■ ■ ■
Time: year ± month ± weekday ± time of day Place: country ± province (state) ± city ± building Person: name ± age ± date of birth
Attention and Concentration There are many different ways of testing these cognitive abilities. There may have been clues from the history that the patient is experiencing difficulties in these areas, for example, an inability to watch a television program from beginning to end, or similar difficulties concentrating on a newspaper article. Two ways to probe attention are as follows: 1. Ask the patient to give the months of the year in reverse order. 2. Ask the patient to serially subtract 7 from 100.
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For both these tests, record the responses and encourage the patient to keep going until no further responses are possible. In one of the most widely cited of all psychometric tests, namely the Mini-Mental State Examination,3 the serial 7s test is done for five subtractions only. Although undoubtedly still useful, if you bail out early in this fashion, it is often not possible for you to comment on a patient’s ability to sustain attention over a more prolonged period of time, the attribute of vigilance. Thus, it is important with the serial 7 test for you to encourage the patient’s perseverance while recording the patient’s responses. A third useful way to assess attention is the Digit Span test.4 This test makes up one of the subtests of the Wechsler Adult Intelligence Scale and is considered a sensitive index of cerebral dysfunction in a patient with an acquired brain insult. In this test, a series of digits is presented at intervals of one per second. You start by calling out three digits and asking the patient to repeat them in the forward direction. If the correct answer is obtained, the process is repeated with four digits, then five digits, etc. Patients are allowed two chances at each level. If they correctly repeat the digits on first hearing, the examiner moves on to the next level. Once a ceiling is reached for the forward repetition of digits (usually seven digits), the process is repeated, but this time the patient is asked to repeat the digits in the reverse order. For the digit span backward, you start once again with a sequence of three digits and build up as described above until a ceiling of six digits is reached. Patients are once again allowed two chances at each level. Should a patient fail both attempts at one level, the score is taken from the previous level successfully completed. There are published, age-corrected normative data for the Digit Span test.5 It is strongly recommended that you have the series of digits written out before testing begins.
Language Disorders of language can be broadly divided into expressive (fluent) and receptive (nonfluent) difficulties. In a Broca-type aphasia (dominant inferior frontal lobe pathology), patients have difficulty expressing themselves, whereas in a Wernicke-type aphasia (dominant posterior superior temporal lobe lesion), the problem is primarily one of comprehension. A conduction aphasia occurs when lesions interrupt the arcuate fasciculus, the tract joining Broca’s and Wernicke’s area. The resultant speech is fluent, with many paraphasic errors that are mainly phonemic (see further discussion). Examining language involves four stages: ■
Assessment of spontaneous speech during conversation and picture description
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Naming ability Comprehension Repetition
During spontaneous speech by the patient, look for the following: articulation; fluency; syntax, that is, the correct use of grammar (agrammatism is associated with Broca’s aphasia); paraphasic errors or word substitutions that can either be semantic (e.g., calling a pen a pencil) or phonemic (e.g., calling a pen a pin); word-finding problems that manifest as circumlocutions (e.g., when asked to name a pen, the patient hesitates and then describes the object instead [“something to write with”]); and finally, the melodic flow to speech, which is termed prosody. When testing naming ability, you should point to some common everyday objects like a shoe, cuff, watch, strap, buckle, etc. A chart with pictures of less common objects can then be used to challenge the patient further. Comprehension can be tested at four levels. First, can the patient keep a conversation going? Second, can the patient respond to commands that do not require a verbal response (e.g., ask the patient to point to the door, ceiling, and floor)? Third, can the patient comprehend a sentence such as “What color is grass?” or “What do we cut bread with?” Finally, if all three levels have been successfully completed, you should move on to testing concept comprehension with questions such as, “What do we call the man who works in a fancy restaurant and creates delicious meals?” Repetition must be tested because it gives clues to the presence of a transcortical aphasia. Here, the lesion lies outside the primary language areas (i.e., Broca’s, Wernicke’s, and the arcuate fasciculus). To test repetition, begin with one-syllable words (e.g., gun, boat) and then move through two (e.g., prosper, happy), and three (e.g., enable, postulate) syllables. Finally, ask the patient to repeat a phrase such as “no if’s, and’s or but’s.” In patients with a conduction aphasia, repetition is severely affected. In a transcortical motor aphasia, however, a patient presents with expressive difficulties as in a Broca-type picture, except repetition to various degrees is spared. In the case of a transcortical sensory aphasia, the patient resembles a Wernicke-type picture, but with repetition once again intact.
Reading Reading is a skill that most often matches language. Ask the patient to read aloud, and then test the ability to comprehend what has been written. For example, hand the patient a piece of paper that has the sentence, “Close your eyes,” written on it. On a more complex level, give the patient a paragraph of text to read aloud, and then test
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whether the content has been understood. Pure alexia occurs but is rare.
Writing Ask the patient to write a sentence spontaneously and then to write a dictation from you. Agraphia, suggesting a lesion of the angular gyrus, may occur with acalculia, rightleft disorientation, and finger agnosia, the four features comprising the Gerstmann syndrome.
In addition to the above schematic representation, there are other terms that are frequently encountered. Memory may rely on recall (the absence of cues) or recognition (cues are present). Furthermore, anterograde memory refers to a patient’s ability to acquire or lay down new memories, whereas retrograde memory refers to the ability to retrieve facts and events from the past. The following template provides a method to assess memory: ■
Calculations Calculations should be tested verbally and in writing. Assess addition, subtraction, multiplication, and division. Examples illustrating the complexity would be as follows: 12 + 37; 45 − 16; 9 × 12; 64 ÷ 4.
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Praxis
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Apraxia refers to the inability to perform skilled motor movements in the presence of normal comprehension, muscle strength, and coordination. A distinction is made between buccofacial and limb apraxia. To test praxis, ask the patient to demonstrate how he would blow out a match, salute like a soldier, and brush his teeth. If a patient cannot follow these commands, test his ability to imitate you performing these movements.
Memory The plethora of terms describing various aspects of memory may at first glance appear confusing. One useful approach to disentangling the terminology is as follows: 6 Memory can be subdivided into that which is effortful (known as explicit or declarative) and that which is not (called implicit or procedural). The latter cannot be tested at the bedside and involves memory that arises from conditioning, priming, and the acquisition of motor skills. Explicit memory, on the other hand, demands conscious effort and can be divided according to whether it is short term or long term. There is no absolute time distinction between the two. Rather, short-term memory should be thought of as immediate or working memory, or to use a computer analogy, the memory that is held “online.” It can be subdivided further into verbal and visual components. Similarly, longterm memory (which by exclusion is all that is not immediate) can be divided into verbal and visual. Longterm memory may, in turn, be divided into semantic (i.e., factual information) and episodic (i.e., personally experienced and temporally specific).
Short-term verbal memory can be tested by asking a patient to remember a name and address (seven facts in all). Record the number of trials (up to five) that it takes the patient to do this. This simple test provides a marker of anterograde memory. Short-term visual memory can be tested by asking a patient to remember a series of shapes. These may be complex, as in the Rey-Osterrieth Test, or simpler, as in a series of checkerboard designs. Long-term verbal and nonverbal memory can be tested by asking the patient to recall the above information at the end of the entire cognitive examination. Retrograde amnesia is assessed with questions that probe semantic and episodic memory. Examples of the former are a series of general knowledge questions (e.g., “What is the capital of Canada?” “Who is the Prime Minister of the United Kingdom?”), whereas episodic memory can be tested by autobiographical recall.
Right-Hemisphere Skills The assessment of right-hemisphere skills centers on various aspects of neglect and agnosia in addition to constructional and spatial abilities. Different types of agnosia are tested as follows: ■
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Object recognition (visual agnosia): Ask the patient to identify common objects like keys, pen, etc. Finger agnosia: Ask the patient to name and move various fingers. Disturbance of identification body parts (autotopagnosia): Ask the patient to move on command and name various body parts. Estimating distances (visuospatial agnosia): Ask the patient which of two objects in the examination room is nearer. Facial recognition (prosopagnosia): Ask the patient to identify well-known personalities (Figure 16-1).
Personal neglect can be tested by asking the patient to discriminate left from right and thereafter various mixed combinations by instruction the patient to “touch your left foot with your right hand” and “touch your left ear with
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Frontal Lobe Tasks Before discussing a list of tests that are sensitive to frontal lobe function, a few comments on the anatomy of this region are called for. Although the prefrontal cortex is the area that subserves many aspects of cognition, an appreciation of other frontal areas is also necessary in completing an assessment: ■
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The motor cortex lies anterior to the central sulcus, and lesions here can result in a contralateral paralysis or paresis. The premotor system is important for integrating motor and sensory function with connections to the primary sensory cortex, somatosensory cortex, primary motor cortex, thalamus, and caudate nucleus. Lesions here may give rise to apraxia and difficulties with fine coordination. The frontal eye fields control conjugate eye gaze. Broca’s area in the inferior frontal lobe controls the expression of speech with lesions resulting in a nonfluent aphasia.
The prefrontal cortex, pivotal in regulating mood, behavior, and cognition, contains three discrete neural circuits that run in parallel to the basal ganglia before looping back to prefrontal areas of origin: ■
FIGURE 16-1 Face recognition. ■
the ring finger of your right hand.” Hemispatial neglect can also be tested by instructing the patient to fill in the numbers on a blank clock face and mark the time at 10 minutes past 11. Constructional ability can be tested by asking the patient to copy a series of shapes that increase in complexity from two to three dimensions (Figure 16-2).
FIGURE 16-2 Constructional ability test.
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The dorsolateral prefrontal cortex (DLPFC) is linked to spatial and conceptual reasoning processes and plays an important role in regulating verbal fluency, attention, and certain aspects of memory. The ventral prefrontal cortex (VPFC) is central to behavior regulation and emotional control, including stimulus reward associations. The anterior cingulate prefrontal cortex (ACPFC) is pivotal in controlling motivation. Lesions here can produce varying degrees of apathy ranging from mildly reduced motivation to akinetic mutism.
The fact that these circuits run to subcortical areas explains an important clinical observation, namely that nonfrontal lesions may produce typical frontal-type behaviors through a process of disconnection (e.g., a lesion in the VPFC may give rise to disinhibited, socially inappropriate behavior characterized by an indifference to adverse consequences). Given that the VPFC circuit starts in the inferior aspect of the prefrontal cortex before relaying sequentially in the caudate nucleus, globus pallidus, substantia nigra, subthalamic nuclei, and finally certain thalamic nuclei before returning to the inferior prefrontal cortex, a lesion anywhere along this pathway may alter behavior as described previously.
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There are a number of bedside frontal lobe test batteries available.7,8 They comprise a mixture of tests that probe attention, verbal fluency, semantic memory, abstract thinking, and cognitive flexibility, the last of these referring to an ability to inhibit or modify verbal and motor responses according to changing instructions or circumstances. All these cognitive functions can be tested, and the results should be combined with behavioral observations that better reflect the functioning of the VPFC because this region defies neat psychometric correlations. Some commonly used tests that are sensitive to the functional integrity of the prefrontal cortex include the following: ■
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Initiation tasks: The most widely used is the COWAT or letter fluency test.1 Here the patient is required to produce orally as many words as possible beginning with the letters F, A, and S. The patient is allowed 1 minute per letter, and at the end of the test the person’s totals are added to give the final score. Patients are instructed not to use proper names (e.g., Sydney, Simon, Sue) or the same word with different endings (e.g., fun, funnier, funniest). Like the Digit Span test, there are published normative data for the COWAT. Analogous tests: An analogous test calls for the patient to name as many four-legged animals as possible in 1 minute. Abstraction ■ Abstraction ability is tested by asking the patient to interpret the proverb, “A bird in the hand is worth two in the bush.” The examiner must be sensitive to education and cultural issues here. ■ A second way to test abstract thinking is to ask the patient a series of questions: “In what way are the following paired items similar and different . . .” ● “Car and bus?” ● “Apple and pear?” Response inhibition and shift testing: This can be tested as follows: ■ Go–No Go test: Ask the patient to raise one index finger in response to one tap on the table. The patient is not to respond when you tap twice. The patient should not see you tap, so use the undersurface of the table for this. Having completed 10 trials, switch instructions (e.g., the patient must not respond to one tap, but must raise an index finger when you tap twice). Failure to inhibit responses when none are called for is deemed pathological. ■ Alternating hand movements: In this test, one had forms a fist while the other has fingers extended, palm facing toward the patient. Alternate these positions between the right and left hand three times, then ask the patient to repeat what you have just done.
The Luria three-step procedure: This calls for you to perform a sequence of movements with the right hand, using the left hand as a base with fingers extended and palm pointing upward. ● Step 1: Fist strikes palm. ● Step 2: Edge of hand with fingers extended strikes palm. ● Step 3: Palm strikes palm. Repeat this three times, then ask the patient to reproduce what you have just done. The patient should perform the sequence five times. Then ask the patient to repeat the process with the right hand acting as the base and the left hand completing the three-step sequence. ■
NEUROPSYCHOLOGICAL TESTING Although the cognitive examination outlined above has significantly greater sensitivity than screening instruments such as the Mini-Mental State Examination,3 it still falls short of a detailed neuropsychological assessment. The latter, however, is time consuming and expensive. Furthermore, many clinicians do not have ready access to such a service. All of this raises the question of when to refer a patient with a neurological illness to a neuropsychologist. Indications for undertaking a formal neuropsychological assessment include the following: ■
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Colleagues or superiors report a decline in a person’s work performance, or the person reports subjective cognitive difficulties in the absence of a prominent mood, substance use, or anxiety disorder. A patient is applying for a disability settlement. A patient is about to enter a treatment trial that may improve (or harm) cognition. A cognitive baseline is therefore required. A patient is entering a cognitive rehabilitation program. Once again, a cognitive baseline is needed to determine relative strengths and weaknesses.
CORTICAL VERSUS SUBCORTICAL DEMENTIA The cognitive profile in patients with neurological disorders can differ according to whether the burden of disease is cortical or subcortical. Senile dementia of the Alzheimer type may be regarded as the quintessential cortical dementing illness, whereas Huntington’s and Parkinson’s diseases represent typical subcortical gray-matter dementias, and multiple sclerosis represents the white-matter equivalent. It is important to emphasize that these
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cortical/subcortical distinctions are not neatly defined anatomical divisions; rather, they reflect differing functional profiles. Thus, apraxia, agnosia, and aphasia are all markers of cortical rather than subcortical cognitive abnormalities. On the other hand, one of the hallmarks of subcortical deficits is delayed information-processing speed. Therefore, patients will have difficulty with timed tasks such as the COWAT. Although both groups may display prominent memory problems, cortically based disorders may result in relatively greater difficulty acquiring new information, whereas in patients with a greater subcortical burden, memory deficits may be more pronounced when retrieval is challenged. In more advanced disease, these distinctions can become blurred. Nevertheless, clinicians must remember that a widely used brief cognitive screening measure like the Mini-Mental State Examination is geared toward cortical cognitive deficits and lacks sensitivity for predominantly white-matter dementias like multiple sclerosis.
NEUROIMAGING Brain imaging can be either structural (e.g., computed tomography [CT], magnetic resonance imaging [MRI]) or functional (e.g., single photon emission computed tomography [SPECT], positron emission tomography [PET], functional MRI [fMRI]). For clinicians, CT, MRI, and SPECT are the commonly available modalities. PET and fMRI are still largely limited to research protocols. MRI has many advantages over CT when it comes to structural brain imaging. These include greater anatomical sensitivity, improved visualization of cerebral white matter, and the ability to image the posterior fossa and medial temporal lobe structures without bone artefact. MRI technology does not make use of radiation, thereby facilitating serial studies. Finally, the brain can be easily scanned in the axial, coronal, and sagittal planes. CT, on the other hand, is cheaper and, in the early stages after traumatic brain injury, may be preferred given the isodense properties of blood. Neuroimaging is an important ancillary investigation for the following reasons: ■ ■
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It may help the neurologist diagnostically. It may provide important clues to the neurologist and psychiatrist concerning cerebral localization. However, here is it important to remember that a lesion at one anatomical location may exert functional effects that are removed from it, a process called diaschisis. It may provide clues as to why a patient’s behavior has altered. In this regard, it forms one part of a workup that starts with history-taking and proceeds through the neurological and mental state examinations, detailed
cognitive assessment, and other investigations (e.g., biochemical, electroencephalogram) if pertinent. What a clinician is looking for here is a confluence of findings. ■ One example of a clinical situation in which all the data come together neatly is as follows: The history suggests stroke; the neurological examination confirms a right-sided weakness; cognitive assessment reveals an expressive aphasia; MRI shows a left frontal hemorrhage; and SPECT demonstrates hypoperfusion in the area of the lesion. In this example, neuroimaging is essentially confirmatory. However, another common clinical situation where neuroimaging carries added diagnostic weight is as follows: The history reveals subtle personality change characterized by mildly inappropriate social behavior; neurological examination is normal; so too is the formal mental state; the cognitive assessment demonstrates mildly reduced verbal fluency (e.g., fewer than expected words on the FAS test); MRI shows mild frontal atrophy; and SPECT displays moderately severe frontal hypoperfusion. The confluence of the history and neuroimaging findings points strongly toward a diagnosis of fronto-temporal dementia.
CONCLUSIONS This chapter has provided a template for the psychiatrist, resident, and medical student to use in the assessment of patients with neurological illness. Given the high prevalence of cognitive deficits in neurological disorders, completing a clinically based cognitive assessment is mandatory to any comprehensive assessment. Furthermore, the information obtained is of considerable practical importance, for there are data linking deficits to many other real-world difficulties patients experience. These range from the workplace to relationships to the basic activities of daily living, all of which adversely impinge on quality of life. Completing an examination as outlined in this chapter will therefore not only enhance the diagnostic process, but will also assist in determining effective treatment and rehabilitation strategies.
REFERENCES 1. Benton AJ, Hamsher K, Sivan AB: Multilingual aphasia examination, Iowa City, IA, 1983, AJA Associates. 2. Nelson HE: National Adult Reading Test (NART): test manual, Windsor, England, 1982, NFER Nelson. 3. Folstein MF, Folstein SE, McHugh PR: “Mini-Mental State”: a practical method for grading the cognitive state of patients for the clinician, J Psychiatric Res 12:189–198, 1975.
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4. Wechsler D: Wechsler adult intelligence scale–revised, New York, 1981, Psychological Corporation. 5. Spreen O, Strauss E: A compendium of neuropsychological tests, ed 2, New York, 1998, Oxford University Press. 6. Hodges JR: Cognitive assessment for clinicians, Oxford, England, 1994, Oxford University Press, pp 5–19.
7. Dubois B, Slachevsky A, Litvan I, Pillon B: The FAB: a frontal assessment battery at bedside, Neurology 55:1621–1626, 2000. 8. Ettlin TM, Kischka U, Beckson M, et al: The frontal lobe score: part 1. Construction of a mental status of frontal systems, Clin Rehabil 14:260–271, 2000.