Cognitive and Language Evaluation

Published on 03/03/2015 by admin

Filed under Neurology

Last modified 03/03/2015

Print this page

This article have been viewed 2499 times

2 Cognitive and Language Evaluation

Yuval Zabar, Dana Penney, Caitlin Macaulay

This chapter provides an overview of the very important neurologic evaluation of higher cortical cognitive and language function. This is predicated on an understanding of frontal, temporal, parietal, occipital lobe and cerebellar function. Detailed anatomic drawings of the cerebral cortex are available for one’s review while reading this chapter. It will provide the basics for an introductory mental status examination. In conclusion, the complicated and detailed evaluation of the patient with aphasia is discussed.

Clinical Vignette

A 65-year-old, right-handed, elementary school principal was referred by her primary care physician for evaluation of progressive speech difficulties. The patient reported a 2-year history of insidiously progressive language problems that began with “yes/no unreliability” to the point where she would indicate yes when she meant no, or vice versa. During the next year, she also developed trouble explaining her thoughts. Her speech became variably slurred and “garbled” with mispronounced words, making it increasingly difficult for friends to comprehend. At times she began saying “unexpected” things such as answering the phone stating “yes” versus “hello.” Nevertheless, despite using unusual words for certain given situations, in general her speech “made sense.” Her voice became gravelly as her speech changed in melodic contour, becoming poorly modulated, and more monotone.

Her facial responsiveness became diminished; she frequently appeared angry despite feeling otherwise and her expression seemed “scary” to students. She “lost” her ability to smile and spit while brushing her teeth, developed facial apraxia, and could no longer initiate a smile or eye-blink, although she could spontaneously blink. Mild agraphia developed; in striking contradistinction, she could use the computer and keyboard without difficulty. Her speech and reading comprehension, as well as calculation were normal. She described her mood as “happy”; she denied being depressed. There was no personality change or memory problems. This lady was still independent in her basic activities of daily living (ADLs), being able to live alone, read voraciously easily recalling what she read, hosted dinner parties, pursued her photography hobby, played bridge, and drove her automobile without difficulty.

However, during the next year, she became increasingly apraxic, losing the ability to perform a number of ADLs, including many skilled motor tasks such as removing jar caps and knitting. Her language function further deteriorated and was characterized by an expressive aphasia with markedly dysfluent speech. Concomitantly, she also evidenced increasing verbal and phonemic paraphasic errors, and a stutter with oral lingual dyskinesias that compromised her intelligibility. Interestingly, she relied on texting (e-mails) for verbal communication, despite the frustration that her typing was becoming increasingly laborious as well. Memory and photography skills remained intact. Personality and mood remained unchanged.

On initial examination, she had only minimal facial animation, characterized by diminished eye-blink frequency. Oral lingual dyskinesia with tongue thrusting and grimacing occurred when she attempted to speak. Speech articulation was effortful, monotonic, and dysarthric. She displayed fine-dexterity problems, such as requiring to pick up her purse using a closed hand with a scooping motion rather than normally grasping her pocketbook with her fingers. Typewritten text was grammatically and semantically normal, yet she had trouble writing. She was able to print her name to command, but was unable to write in cursive. When asked to draw a clock to command, she could not form a reliable circle, drawing an ellipse instead, or could not make an appropriate circle face with correct numbers. Here she demonstrated evidence of mis-sequencing, perseveration, and misplacement of numbers and hands. In contrast, she could copy a clock better than draw one. This suggested impaired organization, planning, and sequencing rather than visuospatial construction impairment. Although she demonstrated inconsistencies in reasoning, she appeared highly intelligent, with intact ability to learn new information.

Comment: This case demonstrates a progressive apraxia of speech. The patient is unable to produce speech but she has relatively normal written language. Comprehension is normal. Other cognitive domains are intact although assessment is limited by the patient’s sparse speech production. This is an example of primary progressive aphasia, one of the clinical variants of frontotemporal lobar degeneration.

Introduction

The initial clinical evaluation of a patient such as this affords the opportunity to assess whether a neurologic patient has overt cognitive or language difficulties. The ability to give a well-organized history provides the experienced neurologist with insight into the patient’s general language and cognitive function. In most patient encounters, it is usually clear that intellect and speech are appropriate to the setting, and thus a more formal set of mental status testing is unnecessary. However, in instances of overt intellectual dysfunction, especially when the patient’s demeanor suggests such a possibility, or the family expresses concern about an additional problem beyond that of the primary patient complaint, a more detailed cognitive examination is necessary to complement the standard neurologic examination.

One’s direct interaction with the patient helps define the behavioral aspects of neurologic function; it is their mood, affect, level of cooperation, and distractibility that are noteworthy. The cognitive part of the neurologic evaluation strives to determine the precise level of various higher cortical functions. The human cerebral cortex, with its multiple gyri and network of many million interconnections, is the most complex part of the brain. Anatomically, the cortex is classified into four major functional areas: frontal, temporal, parietal, and occipital lobes (Fig. 2-1; Table 2-1 and Table 2-2). These anatomic substrates are carefully interconnected in a complex network. Although for the sake of discussion, these cortical areas are typically described in isolation, in reality these interconnections with other cortical and subcortical areas are critical for brain function (Fig. 2-2).

Figure 2-1 Cerebral Cortex (Superolateral Surface).

Table 2-1 Lateral Surface of the Brain: Notable Lateral Sulci

Structure	Anatomic Significance
Lateral (Sylvian) fissure	Separates temporal lobe from frontal and parietal lobes
Central (Rolandic) sulcus	Separates frontal lobe from parietal lobe

From Rubin M, Safdieh J. Netter’s Concise Neuroanatomy, Philadelphia, Saunders, 2007, p. 32.

Table 2-2 Lateral Surface of the Brain: Cortical Lobes, Lateral View

Figure 2-2 Cerebral Cortex: Localization of Function and Association Pathways.

Because some patients are not able to give a history or cooperate with the examiner, the history from reliable family and friends is an essential part of the evaluation. Direct interaction with the patient helps define the behavioral aspects of neurologic function. The patient’s mood, affect, level of cooperation, and distractibility are noteworthy. Many individuals with dementia may seem pleasant and jovial, often finding excuses for their inability to answer questions, rarely with any insight into their deficit. In contrast, patients with severe posterior aphasia may seem agitated and uncooperative, and often respond inconsistently to certain commands but not to others. Assessment of cognitive function requires direct testing of various cognitive domains and a structured, hierarchical approach.

Cognitive Testing

The major cognitive domains included in a routine mental status examination include level of consciousness, orientation, attention, language, memory, visuospatial processing, and executive function. These are best defined as follows:

1. Level of consciousness underlies all aspects of mental status and must be considered immediately. A stuporous patient often displays attention or language impairment; obviously it is not possible to make a cognitive assessment in a comatose patient.

2. Attention allows the individual to focus and register specific information from external and internal environments. Impaired attention may affect the patient’s performance in other cognitive tasks, such as reading, writing, or memorizing lists. Digit span testing is a good means to test attention. The examiner gives the patient a list of five digits and asks them to repeat these in the same sequence. Next, a list of three digits is provided and the patient is instructed to repeat these in reverse order. This test elicits the patient’s ability to give immediate focus and avoid distraction. Fewer than five digits forward or three digits backward may indicate attention problems.

3. Orientation allows an individual to identify when, where, and who they are at any given moment. This requires intact function within widespread cortical regions as well as high-order cognitive processing. Testing this simple modality provides an efficient means to survey general cognitive function. Disorientation to time and/or place may occur in either widespread or focal cortical dysfunction.

4. Language function includes the patient’s ability to monitor and to comprehend language-related sounds and symbols and to generate meaningful verbal or written responses. Most interaction with the patient is language-based, and, therefore, it is crucial to ascertain whether language function is impaired early in the course of the examination. A patient with a nonfluent aphasia may not be able to express three words during memory testing, for example. Such a deficit would not indicate impaired short-term memory or inattention, but primary impairment of language. Impairment of language typically follows left hemispheric damage, although right hemispheric lesions may also impair language function as discussed later in this chapter.

5. Memory testing often focuses on the ability to retrieve a short-term recollection of word lists or stories. Short-term memory, of course, involves far more than the ability to recall a list of words. The brain’s capacity for memory is enormous. It keeps track of what we hear and see, feel and think, from the moment we awaken to the moment we fall asleep. The use of word lists to test the brain’s ability to do this is a very useful bedside tool. The patient must be able to register the words, store them, and then retrieve them from storage. Storage of information can be facilitated with repetition/practice or cuing during the learning phase of the test. Similarly, retrieval of information may be similarly facilitated with cuing. The patient with retrieval memory impairment will benefit from cuing more than the patient with storage problems. The latter patient will not benefit from cuing or practice. Storage memory deficits are typical of medial temporal/hippocampal dysfunction, such as in early Alzheimer’s disease. Whenever a patient has impaired storage function, this must be considered abnormal regardless of age. Retrieval memory deficits are more typical of frontal and subcortical dysfunction; these limitations are characterized by increasing inefficiency and delay in retrieving information, and occur more frequently with advancing age. The precess of short-term memory is analogous to recording video tapes of various events. The person with impaired retrieval has trouble finding the recordings they made, while the person with impaired storage has trouble recording the tapes in the first place.

6. Executive function refers to the brain’s ability to coordinate multimodal cortical processes for the purpose of solving problems, planning and executing tasks, and keeping track of multiple tasks at once. This cognitive ability can be likened to that of a conductor of an orchestra where one efficiently plans and coordinates several sections of the orchestra to achieve a cohesive and meaningful whole.

7. Procedural memory, that is, praxis, is another important cognitive process that refers to the brain’s memory for skilled motor function. This encompasses a host of previously learned motor programs ranging from simple tasks, such as brushing one’s teeth or using a spoon, to far more complex motor activities such as playing the piano. When an individual performs these tasks, he or she does not have to precisely recall what to do; rather, once the person initiates the motor program, the task proceeds implicitly. Praxis per se probably involves several cerebral cortical regions, but when abnormal it is most often associated with dominant frontal lobe dysfunction.

8. Nonverbal recognition, that is, gnosis, refers to the identification and recognition of all aspects of the world around us as well as ourselves. We recognize objects, people, sounds, etc. arranged in very complex sensory environments without needing verbal definition of those items. We can navigate through our world safely and effectively without using language, much like we do while driving home from work, or moving through the hallways of one’s workplace. Agnosia is an acquired failure to recognize things normally. This may involve specific modalities as in visual agnosia or specific content as in prosopagnosia (loss of facial recognition). This processing likely involves bilateral temporal and parietal cortical regions, although right hemisphere temporal parietal pathology predominates.

An Introductory Mental Status Examination

This section provides a brief overview for the initial approach to evaluating mental function. Much of this discussion is further amplified in subsequent sections. A brief mental status exam should first include noting the patient’s level of consciousness, general appearance, behavior, and affect. In addition, there are a series of brief introductory screening tests that are very useful.

Attention testing: Digit span forwards and backwards is an excellent test for attention problems. Serial 7 subtractions taken sequentially from 100 is often examined at the bedside; however, it is not strictly a test of attention. This modality requires calculation and sustained attention or working memory to reliably keep track of the task and work in progress.

Language testing: There are a few basic and efficient means available to initially screen for such impairments. These include (1) a careful conversational speech analysis looking for paraphasic substitutions as well as grammatical errors, (2) noting the ability to follow commands, and (3) naming. Other very useful bedside testing modalities include analyzing the patient’s ability to read, write, and repeat sentences.

Memory is often tested by asking the patient to repeat a list of words immediately after the examiner and then to recall the words after some time delay. Often a 3- or 5-minute delay is employed; however, on occasion subtle problems with storage may require longer delays before recall. Executive function may be assessed by asking the patient to draw a clock with all the numbers and to indicate a specific time. The patient’s approach to drawing the clock given those instructions may provide hints regarding impairment in planning and organizing the task. For example, the circle may be too small, the number placement may be haphazard or incomplete, or the hands may indicate concrete processing, such as pointing to the 10 and the 11 to indicate the time at 11:10. Clock drawing may also demonstrate impairment of spatial processing.

There are several standardized brief assessments of cognition, including the Mini Mental State Exam and the Montreal Cognitive Assessment (MOCA). These studies are particularly useful for assessing memory problems in the elderly. The MOCA is available online at www.mocatest.org along with normative data and translation into multiple languages. It is very useful when screening for very subtle cognitive impairment as seen in Mild Cognitive Impairment or the very earliest stages of dementia. The MMSE may provide a useful tool for staging dementia severity in patients with Alzheimer disease. Additional discussion of such tests is presented in the subsequent dementia chapter (Chapter 18).

Frontal Lobe Dysfunction

The frontal lobe comprises the major portion of the adult brain occupying approximately 30% of brain mass. This includes the motor area (Brodmann area 4), the premotor cortex (Brodmann areas 6 and 8), and significant prefrontal areas (Fig. 2-3). A Brodmann area is a region of the cortex that is defined by the organization of its cells, or cytoarchitecture, as opposed to gross anatomic landmarks such as sulci or gyri. Reference to Brodmann’s areas may provide more precise clinicoanatomic correlation and localization (see Fig. 2-3).

Figure 2-3 Brodmann Areas: Lateral View of the Forebrain: Cytoarchitecture of the Brain Based on Neuronal Organization.

The significant prefrontal areas are distinct from the adjacent motor and premotor areas, particularly in their connections with other cortical areas and the thalamus (see Fig. 2-2). Most of the prefrontal–thalamic connections are made with the dorsal medial nucleus, a prime relay center for limbic projections originating from the amygdala and the basal forebrain. The reciprocal inputs are the most prominent cortical connections, originating from second-order sensory association and paralimbic association areas, including the cingulate cortex, temporal pole, and parahippocampal area. The frontal lobe is an integrator and analyzer of highly complex multimodal cortical areas, including limbically processed information.

The ablation of both frontal lobes in experimental animals leads to very unusual observations. Some of the most dramatic symptoms, including automatic nonpurposeful behaviors with a tendency to chew randomly on objects, led to the conclusion that the frontal lobe was important for the integration of goal-directed movement. Investigations in the 1950s began to define the importance of the frontal lobe for analyzing various stimuli. Frontal lobe lesions led to loss of normal social interchange, personal internal reinforcement, and judgment. Therefore, patients sustaining frontal lobe lesions are unable to modify behavior despite the potentially harming or embarrassing effects of their actions. Additionally, these individuals tend to perseverate by repeating automatic behaviors that do not result in conclusive actions; these are identified with perseveration testing.

Humans sustaining frontal lobe disorders develop significant personality changes and “release of animal instincts.” One of the earliest descriptions of frontal lobe damage described patients with apathy and disturbed emotions. Elucidation of the frontal lobe connections, particularly the medial-basal portion, demonstrates that the limbic system provides significant input to that area (Fig. 2-4). Autonomic centers originating in the brainstem and hypothalamus also have significant connections with the basal frontal lobe. When these connections are disrupted, aggressive, impulsive, and uncontrolled behavior results. Subsequent study has revealed an even greater depth and breadth of frontal lobe function.

Figure 2-4 Major Limbic Forebrain Cingulate Cortex Areas.

From a neuropsychological perspective, the frontal lobes are responsible for executive functions. Frontal lobe syndromes typically are classified clinically, anatomically, and neuropsychologically into lateral, medial, and mesial groups. Prefrontal syndromes that affect these anterior areas have been described as dysexecutive, disinhibited, and apathetic-akinetic. From an anatomic perspective, the dysexecutive syndrome is due to damage of the dorsolateral prefrontal area. The disinhibited syndrome is due to disorders affecting the orbital brain while the apathetic–akinetic syndrome is due to medial area dysfunction.

Patients with damage to the dorsolateral prefrontal cortex typically exhibit stereotyped and perseverative behaviors with mental inflexibility (i.e., stuck in set). Additionally, one will note that these patients demonstrate poor self-monitoring, deficient working memory, difficulty generating hypotheses, and reduced fluency. These patients often demonstrate an associated inefficient/unorganized learning strategy, with impaired retrieval for learned information as well as a loss of set. Such individuals are typically apathetic, exhibiting reduced drive, depressed mentation, and motor programming deficits.

Damage to the orbital–frontal area is characterized by patients presenting with prominent personality changes. They are often disinhibited, impulsive, perseverative, and have potential to be socially inappropriate with poor self-monitoring. Inappropriate euphoria, affective lability with quick onset, poor judgment, and tendency to confabulate are other characteristic personality changes. Typically, these patients exhibit impaired sustained and divided attention, increased distractibility, and anosmia.

Patients with damage to the anterior cingulate gyrus typically experience difficulty reacting to stimuli. They have an impaired initiation of action as well as impaired persistence, reduced arousal, and akinesia/bradykinesia, with loss of spontaneous speech and behavior. Such individuals may present with monosyllabic speech, appear apathetic, have a flat or diminished affect, and may be docile.

Although these various prefrontal lobe syndromes pertain to localized lesions, it is not uncommon for patients to display overlapping behaviors as it is relatively uncommon to have isolated areas of precise frontal lobe pathology. Also, certain behaviors are witnessed that are not due to specific localized deficits. There are some nonspecific frontal signs that sometimes can be elucidated during neurologic examination of the patient with disorders of this nature. These include various frontal release signs, particularly involuntary grasping, and suck reflexes. However, one must take care with interpretation of these findings, especially with elderly individuals, many of whom will have an increased incidence of such findings with normal aging or in the presence of generalized neurologic illness such as with various encephalopathies.

Language dysfunction is a common finding of some frontal lobe lesions. Broca aphasia is the classic form of frontal lobe language dysfunction with dominant hemisphere lesions. It is characterized by a nonfluent, effortful, slow, and halting speech. This language dysfunction is typically of reduced length, that is, few words with reduced phrase length, simplified grammar, and impaired naming. Repetition is characteristically intact. These individuals often have associated apraxia (buccofacial, speech, and of the nonparalyzed limb) and right-sided weakness of the face and hand. Transcortical motor aphasia is another characteristic of frontal lobe language dysfunction. These patients often have very limited spontaneous speech as well as delayed responsiveness. They also tend to be perseverative, akinetic, and may also have contralateral leg weakness and urinary incontinence because of a mesial lesion. This may result from a lesion either in the distribution of the anterior cerebral artery or in the watershed area between the middle and anterior cerebral artery territories. Proximal extremity weakness very rarely, if ever, occurs with a vascular watershed lesion. Auditory comprehension (barring complex syntax), repetition, and naming are intact in transcortical motor aphasia.

Buy Membership for Neurology Category to continue reading. Learn more here

Related

Netters Neurology