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Clinical cognitive assessment 

Clinical cognitive assessment
Chapter:
Clinical cognitive assessment
Author(s):

Christopher Kipps

and John Hodges

DOI:
10.1093/med/9780199644957.003.0010
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Cognitive symptoms arise from the location of brain dysfunction and are not linked directly to any particular pathology. In the early stages of disease, symptoms may be nonspecific, and while certain symptom clusters are commonly seen in particular disorders, atypical presentations are not infrequent. For example, in Alzheimer’s disease, patients may present with a focal language syndrome instead of the more commonly appreciated autobiographical memory disturbance, despite identical pathology. In our approach to the cognitive assessment, we maintain a symptom-oriented approach. This facilitates the localization of pathology and subsequent clinical diagnosis, which may then be supplemented by associated neurological signs, imaging, or other investigations.

The purpose of the cognitive examination is to separate out those patients in whom a firm clinical diagnosis can be made from those in whom additional investigation is required. In this assessment, the history and clinical examination are completely intertwined, and the ability to respond to conversational clues or provide details of personal events is as much a consideration as any formal testing. Skilful examiners often weave their assessment into a relaxed conversation with a patient, making it more enjoyable for both. In neurodegenerative diseases in particular, poor memory and impaired insight make the perspective of an informant, who knows the patient well, essential.

A clear focus is needed from early in the consultation in order to direct the assessment to the areas of greatest relevance that need specific and more detailed examination. A list of particularly discriminating questions can be seen in Table 10.1. In the sections that follow, we divide the cognitive examination into a number of broad domains: attention and orientation, memory, language, executive function, apraxia, visuospatial ability, and behavioural.

Table 10.1 Discriminating features in common neurodegenerative diseases

Disease

Key questions to ask:

Is there…? Do they…?

Clinical signs/investigations

Alzheimer’s disease

  • Repetition of the same question with rapid forgetting of the answer

  • Get lost on familiar routes

  • MRI: generalized atrophy, particularly medial temporal and hippocampal regions

  • CSF biomarkers

  • Amyloid-PET imaging

Frontotemporal dementia (FTD)

  • behavioural variant (bv)

  • Loss of empathy

  • Eating changes

  • Stereotypical behaviours

  • Social inappropriateness

  • Disinhibition

  • Lack of insight

  • MRI: frontal and/or right predominant temporal lobe atrophy

  • Beware phenocopy bvFTD with normal imaging

  • semantic dementia

  • Difficulty with naming objects

  • An inability to understand words

MRI: anterior temporal lobe atrophy (usually left more than right)

  • progressive nonfluent aphasia

Mispronunciation of words with insertion of repeated or incorrect syllables

  • logopenic aphasia

  • Slow speech and difficulty with naming objects

  • Longer sentences are not understood

Frontotemporal dementia with motor neuron disease (FTD-MND)

Rapid progression of a behavioural syndrome and/or language deficits —prominent delusions and/or hallucinations (transient)

  • Fasciculations (limb or tongue)

  • EMG

Progressive supranuclear palsy (PSP)

  • A history of falls

  • Profound apathy

  • Slowed movement and thinking

  • Axial rigidity

  • Vertical gaze palsy

  • Loss of postural reflexes

Lewy body disease

  • Visual hallucinations

  • Fluctuating cognitive ability

  • Falls

  • REM sleep disorder

  • Mild parkinsonism

  • Visuospatial dysfunction

Corticobasal degeneration

  • Difficulty using objects with one hand

  • Limb having ‘a mind of its own’

  • Shock-like jerks

  • Limb apraxia

  • Visuospatial dysfunction

  • Parkinsonism

  • May develop nonfluent language syndrome

Huntington’s disease

Family history (autosomal dominant)

  • Generalized chorea

  • Huntington’s gene

Vascular dementia

  • Vascular risk factors

  • May have stepwise decline, but frequently do not

  • Pyramidal signs

  • Evidence of small and/or large vessel disease on brain imaging

CJD

  • Rapid cognitive decline

  • Movement disorder

  • Neurosurgical procedure or graft

  • Ataxia, tremor, myoclonus

  • MRI abnormalities on diffusion imaging

vCJD

  • Rapid cognitive decline

  • Sensory disturbance

  • Movement disorder

MRI—pulvinar sign

General

We start by establishing a picture of premorbid functioning (e.g. education, employment, significant relationships). Learning a little about the patient’s interests or hobbies allows one to tailor questions in the cognitive examination more precisely. The onset and time course of the deterioration are as important as the cluster of deficits, be they memory, language, visual function, behaviour, or indeed psychiatric, and often the first noted deficit has diagnostic relevance. It is frequently very helpful to ask patients directly what they believe the reason is for their attendance in the clinic.

We try to interview both the patient and informant independently, even when the amount of information likely to be obtained from the patient is minimal. It allows a chance to assess both language and cooperation without assistance or interruption from the partner. Disparities between the two accounts are important as insight is often poor. A family history and risk factors, notably vascular, are particularly relevant, and should be specifically enquired about. Considerable, and sometimes repeated, probing may be needed, as a history of suicide or alcohol dependency in close relatives may disguise an unrecognized early onset dementia. Concomitant illness and medication use frequently underlie, or complicate, cognitive complaints. We use a questionnaire filled out before the consultation, which saves time and helps draw attention to issues in the background history.

Orientation and Attention

Alertness and cooperation with the assessment should be noted, as these factors may impact on the subsequent findings. The level of alertness is an important clue to the presence of a delirium or the effects of medication. Delirium may be marked by both restlessness and distractibility, or the patient may be quiet, and drift off to sleep easily during the consultation. If there is any concern about the level of alertness of the patient, review of the medication list is often helpful. It may be misleading, and is frequently hopeless, to perform a detailed cognitive assessment on a patient with diminished alertness. If that is the case, documentation of orientation and attention may be as much as can be achieved initially.

Orientation

Orientation is usually assessed to time, place, and person; it is not particularly sensitive, and intact orientation does not exclude a significant memory disorder, particularly if there is concern about memory from an informant.

Time orientation is the most helpful, and should include the time of day. Many normal people do not know the exact date, and being out by two days or less is considered normal when scoring this formally. Time intervals are often poorly monitored by patients with delirium, moderate to severe dementia, and in the amnesic syndrome, and are easily tested by asking about the length of time spent in hospital.

Place should be confirmed, and asking what the name of the building is (e.g. outpatient clinic), rather than the name of the hospital, often produces a surprising lack of awareness of location. Since there are often visual and contextual cues present, this is less sensitive than orientation to time, and is particularly the case when assessing someone at home.

Person orientation includes name, age, and date of birth. Disorientation to name is usually only seen in psychogenic amnesia. In the aphasic patient, earlier conversation should have revealed the true deficit, but a mistaken label of ‘confusion’ is frequently applied because such patients either fail to comprehend the question or produce the wrong answer. Given a choice, they can usually pick out their own name.

Attention

Attention can be tested in a number of ways including serial 7s, digit span, spelling WORLD backwards, and recitation of the months of the year in reverse order. Although serial 7s is commonly used, it is frequently performed incorrectly by older people, as well as by patients with impaired attention. Reverse-order months of the year is a highly overlearned sequence, and we prefer it as a measure of sustained attention.

Digit span is a relatively pure test of attention and is dependent on working memory, but it is not specific and can be impaired in delirium, focal left frontal damage, aphasia, and moderate to severe dementia. It should, however, be normal in the amnesic syndrome (e.g. Korsakoff’s syndrome and medial temporal lobe damage). Start with three digits and ensure that they are spoken individually and not clumped together in the way that one might recite a telephone number (e.g. 3–7–2–5 and not 37–25, etc.). Normal digit span is 6 ± 1, depending on age and general intellectual ability. In older people or the intellectually impaired, 5 can be considered normal. Reverse span is usually one less than forward span. In performing this test, it is helpful to write out the numbers to be used before starting.

Memory

Complaints about poor memory are the most frequent reason for referral to a cognitive disorders clinic and often provide a good starting point for the consultation, despite not being very specific.

A useful framework for analysing memory complaints divides memory into several separate domains. Episodic memory (personally experienced events) comprises anterograde (newly encountered information) and retrograde (past events) components, and depends on the hippocampal-diencephalic system. A second important system involves memory for word meaning and general knowledge (semantic memory), the key neural substrate being the anterior temporal lobe. Working memory refers to the very limited capacity that allows us to retain information for a few seconds, and uses the dorsolateral prefrontal cortex. The term ‘short-term’ memory is applied, confusingly, to a number of different memory problems, but has no convincing anatomical or psychological correlate.

Episodic memory

Anterograde memory loss is suggested by the following:

  • forgetting recent personal and family events (appointments, social occasions)

  • losing items around the home

  • repetitive questioning

  • inability to following and/or remember plots of movies, television programmes, details of current affairs

  • deterioration of message-taking skills

  • increasing reliance on lists.

Retrograde memory loss is suggested by the following:

  • memory of past events (jobs, past homes, major news items)

  • getting lost, with poor topographical sense (route-finding).

Specific questions about the route taken to the hospital or recent events on the ward can be tested directly during conversation. Recalling a name and address or the names of three items is also often used. If care is not taken to ensure proper registration of the items at the start of this test, the results may be confusing or misleading. Poor registration, usually a feature of poor attention or executive dysfunction, may invalidate the results of recall or recognition that test episodic memory. Free recall is harder than the recognition of an item from a list. Testing in the hearing impaired poses particular challenges but can be tested verbally by the use of written instructions, in large print, after handing the patient his or her spectacles.

Anterograde nonverbal memory can be assessed by asking a subject to copy and later recall geometric shapes. Alternatively, it is possible to hide several objects around the room at random, and ask the patient to search for them several minutes later. This is an easy task, and inability to perform well is a convincing sign of memory impairment.

Famous events, recent sporting results, or the names of recent prime ministers can all be used to test retrograde memory without an informant. More remote autobiographical memory assessment needs corroboration, and may be relatively preserved in early Alzheimer’s disease. Autobiographical ‘lacunes’, where discrete periods of time or events are forgotten, are a characteristic feature of transient epileptic amnesia (TEA).

Memory loss and learning impairment out of proportion to other cognitive disturbance is known as the amnesic syndrome. Generally, both anterograde and retrograde memory loss occur in parallel, such as in Alzheimer’s disease and head injury, but dissociations occur. Disproportionately severe anterograde amnesia may be seen when there is hippocampal damage, particularly in herpes simplex encephalitis, focal temporal lobe tumours, and infarction. Confabulation, for example in Korsakoff’s syndrome, might be grandiose or delusional, but more often involves the misordering and fusion of real memories that end up being retrieved out of context. A transient amnesic syndrome with marked anterograde, and variable retrograde, amnesia is seen in transient global amnesia (TGA), whilst ‘memory lacunes’, and repeated brief episodes of memory loss suggest TEA.

Simply asking both patient and informant to give an overall memory rating (out of 10) is often helpful. It is seldom, if ever, that truly amnestic patients will give themselves scores such as 0 or 1, although their spouse might. The reverse is often true of those who forget primarily because of anxiety or depression.

Working memory

Lapses in concentration and attention (losing your train of thought, wandering into a room and forgetting the reason, forgetting a phone number that has just been looked at) are common and increase with age, depression, and anxiety. Such symptoms are much more evident to patients than to family members and, in isolation, are usually not of great concern. It should be noted, however, that basal ganglia and white matter diseases may present with predominantly working memory deficits.

Semantic memory

Patients with semantic breakdown typically complain of ‘loss of memory for words’. Vocabulary diminishes and patients substitute words like ‘thing’. There is a parallel impairment in appreciating the meaning of individual words which first involves infrequent or unusual words. Word-finding difficulty is common in both anxiety and ageing, but it is variable and not associated with impaired comprehension. This is in stark contrast to the anomia (impaired naming) in semantic dementia which is relentlessly progressive and associated with both object agnosia (inability to recognize objects) and atrophy of the anterior temporal lobe, usually on the left. Testing of language function is described in detail in the next section.

Language

The majority of language deficits are usually revealed within the first few minutes of listening to the patient speak, particularly where poor fluency, prosody, agrammatism, and articulation are involved. Evidence of word-finding impairments and paraphasic errors are also usually quickly apparent. Documenting several examples of these errors is often quite helpful to subsequent clinicians. Sometimes, however, a relatively fluent history may mask quite significant naming and single-word comprehension deficits, and it is important to assess this routinely with infrequently encountered words and with directed questioning.

Naming

The degree of anomia is useful as an overall index of the severity of a language deficit, and is a prominent feature in virtually all post-stroke aphasic patients, in moderate stage Alzheimer’s disease, as well as semantic dementia. Naming ability requires an integration of visual, semantic, and phonological aspects of item knowledge. There is a marked frequency effect, and rather than using very common items to test the patient, such as a pen or watch, it may be more informative to ask about a winder, nib, cufflinks, or a stethoscope. Line drawings in the Addenbrooke’s Cognitive Examination (ACE-R) (see section Cognitive assessment scales and Fig. 10.1) are useful for assessing naming ability. Phonemic paraphasias (e.g. ‘electrickery’ for ‘electricity’) and semantic paraphasias (‘clock’ for ‘watch’, or ‘apple’ for ‘orange’) may also be seen, and reflect pathology in Broca’s area and the posterior perisylvian region, respectively. Broad superordinate responses, such as ‘animal’ may be given in response to pictures of, for example, a camel, with the progressive semantic memory impairment seen in semantic dementia. Posterior lesions, particularly of the angular gyrus, can produce quite pronounced anomia for visually recognized objects, and may be associated with alexia.

Fig. 10.1 Line drawings used in Addenbrooke’s Cognitive Examination (revised version) to assess naming and comprehension. (© John Hodges, 2000.)

Fig. 10.1
Line drawings used in Addenbrooke’s Cognitive Examination (revised version) to assess naming and comprehension. (© John Hodges, 2000.)

Comprehension

Difficulty with comprehension is often (incorrectly) assumed to be a result of hearing impairment. Complaints of difficulty using the telephone or withdrawal from group conversations may be more subtle clues to its presence. It is useful to assess comprehension in a graded manner, starting with simple and then more complex instructions.

Use several common items (coin, key, pen) and ask the patient to point to each one in turn in order to assess single word comprehension. There is a frequency effect, and if this test seems too easy, try harder items around the room. We also test comprehension by asking patients to define the meaning of words such as hippopotamus, caterpillar, encyclopedia, emerald, and perimeter, which is done at the same time as assessing repetition (see below).

Sentence comprehension can be tested with several common items in order to devise syntactically complex commands. For example: touch the pen, and then the watch, followed by more difficult sentences such as touch the watch, after touching the keys and the pen. Alternatively, ask ‘If the lion ate the tiger, who survived?’ Syntactic ability is classically impaired with lesions of Broca’s area or the anterior insular region and is commonly accompanied by phonological errors and poor repetition.

Repetition

Use a series of words and sentences of increasing complexity. Repetition of polysyllabic words such as ‘hippopotamus’ or ‘caterpillar’ followed by enquiry as to their nature assesses phonological, articulatory, and semantic processing simultaneously. Listen carefully for phonemic paraphasias during this task. Sentence repetition can be tested with the well-known phrase ‘No ifs, ands or buts’ which is somewhat surprisingly more difficult than repeating ‘The orchestra played and the audience applauded’. This can be further supplemented by using statements with several embedded clauses such as ‘I only know that John is the one to help today’ from the Montreal Cognitive Assessment (MoCA). Inability to do this points to deficits in auditory working memory.

Reading

Failure to comprehend is usually accompanied by an inability to read aloud, but the reverse is not necessarily true. Test this either by writing a simple command, such as ‘Close your eyes’, or by using a few phrases from a nearby newspaper. If a reading deficit is detected, this should be characterized further.

Patients with so-called pure alexia exhibit the phenomenon of letter-by-letter reading, with frequent errors in letter identification. Neglect dyslexia, seen in right hemisphere damage, is usually confined to the initial part of a word and can take the form of omissions or substitutions (e.g. land for island, and fish for dish). Surface dyslexics have difficulty in reading words with irregular spelling (e.g. pint, soot, cellist, dough), which indicates a breakdown in the linkage of words to their underlying semantic meanings and is one of the hallmarks of semantic dementia. Deep dyslexics are unable to read plausible nonwords (e.g. neg, glem, deak), and make semantic errors (canary for parrot).

Writing

Writing is more vulnerable to disruption than reading and involves coordination of both central (spelling) and more peripheral (letter formation) components. Central dysgraphias affect both written and oral spelling. These syndromes are analogous to those seen in the acquired dyslexias, and can be tested similarly.

In general, intact oral spelling in the face of written spelling impairments suggests a writing dyspraxia or neglect dysgraphia. The former results in effortful, and often illegible, writing with frequent errors in the shape or orientation of letters. Copying is also abnormal. A mixed central and peripheral dysgraphia with spelling errors that tend to be phonologically plausible is commonly seen in corticobasal degeneration (CBD). Neglect dysgraphia results in misspelling of the initial part of words, and is frequently associated with other nondominant parietal lobe deficits of visuospatial ability and perceptual function.

Acalculia

Acalculia refers to the inability to read, write, and comprehend numbers, and is not exactly the same as an inability to perform arithmetical calculations (anarithmetria). Although simple calculation is sufficient for most purposes, a full assessment of this skill requires the patient to write numbers to dictation, copy numbers, and read them aloud. The left angular gyrus appears to be important for these numeracy skills. The patient should also be asked to perform oral arithmetic and written calculation and finally be tested in ability to reason arithmetically (e.g. calculating change received when purchasing several items). The integration of several skills is important here, including the retrieval of stored arithmetic facts and the ability to manipulate numerical quantities arithmetically.

Executive and Frontal Lobe Function

Impairments in this domain typically involve errors of goal setting, planning, judgement, initiation, flexibility, impulse control, and abstract reasoning. Although executive function is generally believed to be a (dorsolateral) frontal lobe function, this set of skills is probably much more widely distributed in the brain than this. Head injury is a common cause of impaired executive function, which is also usually seen in Alzheimer’s disease, even in the early stages. It is important not to forget that most of the frontal lobe is subcortical white matter, and consequently many of the leukodystrophies cause executive dysfunction and discrete frontal lobe signs. Basal ganglia disorders also impair these skills, the prime example being progressive supranuclear palsy (PSP).

Letter and category fluency

Letter and category verbal fluency are very useful tests, and poor performance in both is common in executive dysfunction. Patients are asked to produce as many words as possible, starting with a particular letter of the alphabet (F, A, and S are the commonly used letters). Proper names and the generation of exemplars from a single stem (e.g. pot, pots, potter) are not allowed. Category fluency is performed by, for example, asking for as many animals as possible in 1 minute. Young adults can produce 20 animals, 15 animals is low average, and less than 10 is definitely impaired. Letter fluency is usually more difficult (a score of 15 words per letter is normal), and subjects with subcortical or frontal pathology score poorly on both measures but worse on letter fluency. In contrast, patients with semantic deficits, such as semantic dementia and Alzheimer’s disease, have a more marked impairment for categories. Refinements, such as categories of dogs and type of fruit, can be introduced to detect more subtle deficits.

Impulsivity, cognitive estimates, perseveration, and proverbs

Impulsivity is thought to reflect failure of response inhibition and is seen in inferior frontal pathology. It can be assessed using the Go-No-Go task. The examiner instructs the patient to tap once in response to a single tap and to withold a response for two taps. This test can be made more difficult by changing the initial rule after several trials (e.g. tap once when I tap twice, and not at all when I tap once). The ability to switch task and the inhibition of inappropriate, or perseverative, responses can also be assessed by asking the patient to copy a short sequence of alternating squares and triangles, and then to continue across the page (Fig. 10.2). Perseveration in drawing one or other of the shapes may be seen in frontal lobe deficits, but the test is relatively insensitive. A tendency to clap more than the same number of times as the examiner (usually three) also suggests perseveration. Further clinical examples include palilalia and palalogia which are characterized by the repetition of sounds and words respectively, whilst the repetition of whatever is heard is known as echolalia.

Fig. 10.2 A sequence of alternating shapes to test the ability to switch tasks and suppress inappropriate perseverative responses.

Fig. 10.2
A sequence of alternating shapes to test the ability to switch tasks and suppress inappropriate perseverative responses.

The Cognitive Estimates Test may prompt bizarre or improbable responses in patients with frontal or executive dysfunction. Although it is a formal test, with defined scoring norms, it can be performed at the bedside by asking, for example, the population of a nearby city, of London, and of the UK, the height of the Post Office Tower, or the speed of a typical racehorse. Questions about the similarity between two conceptually similar objects can be used to assess inferential reasoning which may be impaired in the same way. Simple pairs such as ‘apples and oranges’ or ‘desk and chair’ are tested first, followed by more abstract pairs such as ‘love and hate’ or a ‘poem and a statue’. Patients typically answer, quite concretely, that two objects are ‘different’ or that they are ‘not similar’ and are unable to form an abstract concept to link the pair. This often persists despite encouragement to consider other ways in which the items are alike. Testing of proverbs probably measures a similar skill, but it is highly dependent on premorbid educational ability and cultural background.

The three-step Luria test, a motor sequencing task, is thought to be a left frontal lobe task, and is discussed more in the section Apraxia.

Behavioural assessment

Inappropriate behaviour is seldom, if ever, elicited from the history given by the patient, who may act quite normally during a clinical consultation. Direct questioning about conflict at work, with interpersonal relationships, or involvement with law enforcement agencies may be helpful in determining the degree of insight; however, the corroboration of the history from an informant, interviewed alone, is crucial. Spouses may mention embarrassing social behaviour, changes in food preference (in particular sweet foods), or inappropriate sexual behaviour. Ability to empathize and judge the emotional state of others is particularly disrupted in the frontotemporal syndromes. The informant should also be questioned about irritability, anxiety, and poor judgement. Apathy and poor motivation are common features of Alzheimer’s disease and frontotemporal and subcortical dementias, but do not differentiate well between different aetiologies. Impulsiveness, which is sometimes demonstrated clinically by the Go-No-Go task described in the section Impulsivity, cognitive estimates, perseveration, and proverbs, may be a marker of impaired inhibition, an inferior frontal lobe function.

There are few clinical tests that reliably and objectively document behavioural impairment. Of most use are a number of behavioural inventories that list symptoms and their severity (e.g. the Neuropsychiatric Inventory (NPI), Cambridge Behavioural Inventory (CBI), and Frontal Behavioural Inventory (FBI)) and are either filled out by the carer prior to the consultation or scored in a structured clinical interview.

The anatomic localization of many behavioural symptoms is poorly understood, but there is an increasing awareness of the role of the right hemisphere, particularly the medial (anterior cingulate) and inferior (orbital) frontal and anterior temporal.

Apraxia

The inability to perform a movement with a body part despite intact sensory and motor function is termed apraxia. Theoretically, the concept can be divided into errors of action conception (knowledge of actions and of tool functions, e.g. the pupose of a screwdriver) and action production (generation and control of movement). Although a number of categories, such as limb-kinetic, ideomotor, and ideational apraxia, exist, these labels are seldom useful in clinical practice. It is more helpful to describe the apraxia by region (orobuccal or limb), and to provide a description of impaired performance, recording both spatial and temporal or sequencing errors on several different types of task.

A thorough assessment of apraxia should involve the following:

  • Imitation of gestures, both meaningful (e.g. wave, salute, hitch-hiking sign) and meaningless (body and nonbody-oriented hand positions). Meaningful gestures should also be tested to command. See Fig. 10.3.

  • Orobuccal movements (blow out a candle, stick out your tongue, cough, lick your lips) and the use of imagined objects (comb your hair, brush your teeth, carve a loaf of bread) are assessed. A common error is to use a body part as a tool, such as a finger for a toothbrush; if repeated after being corrected, this can be considered pathological. Actual use of the object generally elicits better performance than when it is mimed, and is typical of so-called ideomotor apraxia.

  • A sequencing task such as the Luria three-step command (fist, edge, palm) or the alternating hand movements test completes the assessment. This latter task is performed, after demonstration, with arms outstretched, and alternate opening and closing of the fingers of one hand, while those of the other remain clenched in a fist.

  • Lower limb apraxia may be demonstrated by an inability to trace patterns with the feet on the ground in response to command. Relative preservation of some movements (e.g. bicycling movements with the legs whilst lying down) in the presence of gait ataxia may also suggest an apraxic cause.

Fig. 10.3 Examples of meaningful and meaningless hand gestures that may be used in testing for limb apraxia. It is important to ensure that there is no physical limitation (e.g. severe arthritis, contractures, hemiplegic stroke) that prevents the patient from copying the gesture.

Fig. 10.3
Examples of meaningful and meaningless hand gestures that may be used in testing for limb apraxia. It is important to ensure that there is no physical limitation (e.g. severe arthritis, contractures, hemiplegic stroke) that prevents the patient from copying the gesture.

In general, apraxic signs are of limited localizing value, but the left parietal and frontal lobes appear to be of greatest importance. Orobuccal apraxia is closely associated with lesions of the left inferior frontal lobe and the insula, and commonly accompanies the aphasia caused by lesions of Broca’s area. Progressive, isolated limb apraxia is virtually diagnostic of corticobasal degeneration.

Visuospatial Ability

Deficits in the visuospatial domain are quite commonly associated with neurodegenerative diseases, particularly Alzheimer’s disease, but are often clinically silent and missed unless enquired about specifically (Fig. 10.4). Getting lost in familiar surroundings (topographical disorientation), difficulties with dressing (dressing apraxia), misreaching for objects, and the failure to identify familiar faces are all markers of this type of impairment.

Fig. 10.4 Examples of poor visuospatial performance when reproducing interlocking pentagons, the wire cube, or drawing a clock face. This patient has dementia with Lewy bodies (DLB), which frequently causes visuospatial impairment. Other common causes include Alzheimer’s disease and corticobasal degeneration (CBD).

Fig. 10.4
Examples of poor visuospatial performance when reproducing interlocking pentagons, the wire cube, or drawing a clock face. This patient has dementia with Lewy bodies (DLB), which frequently causes visuospatial impairment. Other common causes include Alzheimer’s disease and corticobasal degeneration (CBD).

Visual neglect may produce a failure to groom one half of the body or eat what is placed on one side of a plate. Visual hallucinations invariably suggest an organic cause and are prominent in dementia with Lewy bodies and acute confusional states. Formed visual hallucinations may also be seen in the absence of cognitive impairment in the Charles Bonnet syndrome, and are often associated with poor eyesight; insight is generally retained.

Information from the visual cortex is directed towards the temporal or parietal cortex via one of two streams. The dorsal (‘where’) stream links visual information with spatial position and orientation in the parietal lobe, whereas the ventral (‘what’) stream links this information to the store of semantic knowledge in the temporal lobes. The frontal eye fields are important in directing attention towards targets in the visual field.

Neglect

Neglect of personal and extrapersonal space is usually caused by lesions to the right hemisphere—usually the inferior parietal or prefrontal regions. Deficits can be uncovered by simultaneous bilateral sensory or visual stimulation, or having the patient bisect lines of variable length. Letter and star cancellation tasks are similar, more formal tasks. Patients with object-centred neglect fail to copy one side of an object, and neglect dyslexics may not read the beginning of a line or word. Patients with anosognosia deny they are hemiplegic or even that the affected limb belongs to them.

Dressing and constructional apraxia

Although deficits in dressing and constructional ability are termed apraxias, they are best considered as visuospatial rather than motor impairments. Copying three-dimensional shapes such as a wire cube, interlocking pentagons, or constructing a clock-face with numbers are good tests of constructional ability, and may also highlight neglect if it is present. Left-sided lesions tend to cause oversimplification in copying, whereas right-sided lesions may result in abnormal spatial relationships between the constituent parts of the figure. Dressing apraxia is easily tested by having the patient put on clothing that has been turned inside-out.

Visual agnosias

Visual object agnosias cause a failure of object recognition despite adequate perception. Those with apperceptive visual agnosia have normal basic visual functions, but fail on more complex tasks involving object identification and naming. However, they are able to name objects to description, or by touch, indicating a preserved underlying semantic representation of the object. This phenomenon is described with bilateral occipitotemporal infarction. In cases of associative visual agnosia, the deficit reflects a disruption of stored semantic knowledge, and involves all modalities accessing this information. This is always secondary to anterior temporal lobe pathology, typically semantic dementia and herpes encephalitis. To test for these syndromes, it is necessary to assess object naming and description, along with tactile naming, naming unseen objects to description, and the ability to provide semantic information about unnamed items.

Prosopagnosia

Prosopagnosics cannot recognize familiar faces. Often other clues, such as gait, voice, and distinctive clothing, are used to aid identification. The deficit may not be entirely selective to faces, and often fine-grained identification within categories may also be impaired (e.g. makes of car, types of flowers). Patients are generally able to characterize individual facial features, and if the underlying (semantic) knowledge associated with a particular person is not disrupted, the ability to produce attributes of the face in question, if it is named, remains intact. An occipitotemporal lesion underlies this disability and is often associated with a field defect, achromatopsia, or pure alexia. Whether it is necessary to have bilateral pathology remains controversial. Where there is anterior right temporal lobe involvement, as in the right temporal variant of semantic dementia, person-based social knowledge is often profoundly affected. These patients also find it difficult to judge facial affect. In delusional misidentification syndromes such as the Capgras syndrome, patients are convinced that an impostor, who looks identical, has replaced a close relative. It occurs in dementia and schizophrenia, and there is a suggestion that the linkage of affective attributes to a face may be disconnected from processing of its identification.

Colour deficits

Colour processing deficits such as achromatopsia (loss of ability to discriminate colours) are often associated with pure alexia after medial occipitotemporal damage, following left posterior cerebral artery infarction. Colour agnosia impairs tasks requiring retrieval of colour information (e.g. ‘What colour is a banana?’), and colour anomia (e.g. ‘What colour is this?’) refers to a specific disorder of colour naming despite intact perception and colour knowledge, probably caused by a disconnection of the language structures in the temporal lobe from the visual cortex.

Rare visual syndromes

A few rare syndromes are worthy of mention. Balint’s syndrome consists of a triad of simultanagnosia (inability to attend to more than one item of a complex scene at a time), optic ataxia (inability to guide reaching or pointing despite adequate vision), and occulomotor apraxia (inability to voluntarily direct saccades to a visual target). Fields may be full when challenged with gross stimuli, and occulocephalic reflexes are intact. This syndrome results from bilateral damage including the superior-parieto-occipital region, which disrupts the dorsal (‘where’) visual processing stream linking visual with parietal association areas. Possible causes include carbon monoxide poisoning, watershed infarction, leucodystrophy, and the posterior cortical variant of Alzheimer’s disease. Anton’s syndrome is a visual agnosia, in which the patient denies any deficit and may attempt to negotiate the environment, invariably without success. In the curious phenomenon known as blindsight, visual stimuli can induce a response despite cortical blindness. It is probably mediated by perceptual processing in subcortical structures and brainstem nuclei.

Activities of daily living (ADLs)

Recent research criteria for dementia include impaired ADLs in the definition of dementia. The ability to organize finances, use home appliances, to drive safely, and organize medication regimens are higher order (instrumental) ADLs that are usually impaired earlier in disease than more commonly assessed skills such as cooking, walking, personal hygiene, and continence (basic ADLs). This is an area in which a reliable informant, who knows the patients well, is essential.

Driving

Driving is often a sensitive issue. Early cognitive impairment does not preclude driving but should prompt discussion of driving ability. In general, spouses are fairly aware of changes in driving skill, and their concerns should not be dismissed lightly. Impairments in visuospatial ability (e.g. copying the wire cube, pentagons, drawing a clock face) are good markers of increased driving risk. Often, cessation of driving can be negotiated, but in extreme cases, where poor insight conflicts with a sensible approach, keys can be hidden, cars can be disabled, moved, or sold, and the licensing authority notified. An independent driving assessment may be very advisable.

Cognitive Assessment Scales

Perhaps the most widely used cognitive rating scale is the mini-mental state examination (MMSE), which, although useful, is weighted significantly towards aspects of memory and attention. However, it provides relatively little by way of language testing, minimal assessment of visuospatial ability, and no testing of executive performance. It is scored out of 30, with a score of 24 or less being regarded as abnormal. The patient’s educational background, age, and first language should be considered. It has the benefit of being fast to administer and is well recognized as a screening instrument, but it is quite insensitive, particularly in the context of frontal and subcortical pathology, as well as mild cognitive impairment.

The Addenbrooke’s Cognitive Examination (ACE) has been developed in an attempt to address the deficiencies of the MMSE. It was designed to be sensitive to the early stages of frontotemporal dementia and Alzheimer’s disease and has been shown to be sensitive to cognitive dysfunction in the Parkinson-plus syndromes. The 100-point scale incorporates the items of the MMSE, but includes more tests of executive function, visuospatial skill, and more complex language assessment. The revised version (ACE-R) provides subscores for five domains: orientation and attention, memory, verbal fluency, language, and visuospatial/perceptual functioning. A cut-off of 88 provides high sensitivity but lower specificity, while a cut-off of 82 has very high specificity for dementia at the cost of lower sensitivity.

The Montreal Cognitive Assessment (MoCA) is a 30-point cognitive screening test of orientation, memory, language, attention, and executive function. This has good sensitivity for Mild Cognitive Impairment (MCI), Alzheimer’s disease, and other neurodegenerative diseases.

The briefest of all of the screening examinations is the mental test score (MTS), which is a 10-item scale assessing orientation, memory (anterograde and retrograde), and attention. A score of 6 or less is abnormal in older people, but as with the other cognitive rating scales, the profile of deficits is more instructive than the global score. It may help direct further, more detailed assessment, but offers no advantages over the other scales other than speed of administration.

Formal Neuropsychological Assessment

Unfortunately, neuropsychological services are not always available. In general, it is reasonable to reserve this facility for patients in whom we need more detailed assessment for diagnostic purposes, or those in whom we wish to better characterize deficits for the purposes of rehabilitation. Patients with clearcut deficits of moderate severity are unlikely to need formal testing to reach a diagnosis. In contrast, neuropsychology has much to offer for patients in whom deficits are early and subtle, or who have marginal performance on cognitive screening scales.

General Neurological Examination

A cognitive assessment is incomplete without a careful general neurological examination. There are a number of clinical features that have particular importance. Although in the early stages of many neurodegenerative diseases, clinical signs may be absent, this is not invariable. Table 10.2 highlights the important neurological findings associated with various cognitive disorders.

Table 10.2 Associated neurological features in dementia

Neurological feature

Common or early

Less common or late

Extrapyramidal signs:

  • - bradykinesia

  • - rigidity

  • - tremor

Parkinson’s disease (PD), corticobasal degeneration (CBD), progressive supranuclear palsy (PSP), frontotemporal dementia (FTD), dementia with Lewy bodies (DLB), vascular dementia (VaD)

Alzheimer’s disease, dementia pugilistica, Wilson’s disease (WD), neurodegeneration with brain iron accumulation (NBIA), leucodystrophies, dentato-rubro-pallido-luysian atrophy (DRPLA)

Chorea

Huntington’s disease (HD), DRPLA

Autoimmune: systemic lupus erythematosus (SLE)

Eyes:

  • - impaired saccades and/or gaze palsy

  • - visual hallucinations

  • - Kayser-Fleischer rings

  • PSP, HD, Niemann-Pick type C (NPC), Wernicke-Korsakoff (W-K)

  • DLB, delirium

  • WD

Frontal signs:

  • - utilization

  • - grasp

  • - palmomental

  • - pout

Subcortical dementia, leucodystrophy, FTD, PSP, WD, frontal tumours, hydrocephalus

Alien limb

CBD

Corpus callosum lesion

Dystonia

CBD, WD, HD

AD, Lesch-Nyhan

Myoclonus

Prion disease, CBD, familial AD, encephalopathy (asterixis)

MSA, DLB, post-anoxic, Whipples (facial myorhythmia)

Ataxia

Prion diseases, multiple sclerosis (MS), MSA, W-K, SCA, NBIA, DRPLA, (WD), leucodystrophy

Orobuccal apraxia

CBD, progressive nonfluent aphasia (PNFA)

Pyramidal signs

MND, MS, MSA, SCA, leucodystrophy, prion disease, hydrocephalus

FTD, familial AD

Peripheral neuropathy

Leucodystrophy (especially metachromatic), deficiency states, NBIA, SCA syndromes

Neuroacanthocytosis

Muscle wasting, weakness, and fasciculation

MND-associated FTD

Anosmia

Head injury, most neurodegenerative diseases (HD, PD, AD)

Anterior cranial fossa tumour

Conclusion

It is not possible to examine everything in the cognitive assessment and, as in most other areas of neurology, the history remains pre-eminent in guiding subsequent examination. The central role of a reliable informant, and the ability to immediately test hypotheses generated during the history-taking, distinguish this means of neurological assessment.

In some patients it is not possible to reach a firm diagnosis after a single cognitive assessment, even when in possession of a formal neuropsychological report. This is particularly true for the mild stages of neurodegenerative diseases where symptoms may be nonspecific, and reflects the relative insensitivity of both clinical and imaging assessment to early pathology. The time-honoured method of longitudinal follow-up and repeated assessment in such cases is invaluable and should not be forgotten.

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