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:

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.

Various diseases or injuries that result in executive dysfunction do not necessarily have to directly affect the frontal lobes per se. This is due to the presence of widespread subcortical–frontal cortical as well as other cortical–frontal cortical connections wherein a distant nonfrontal lesion can impact on primary frontal lobe function. When someone sustains an acceleration/deceleration brain injury wherein the brain strikes the bony prominences of the skull, there is an increased incidence of frontal lobe injury. This is particularly the situation with injuries either at the basal orbital frontal regions lying directly adjacent to the skull’s cribriform plate or at the frontal poles adjacent to the frontal bone. Frontal lobe injury may also result indirectly because of shearing of white matter tracts.

Dementing illness, particularly those referred to as frontal-temporal lobar dementias and Lewy Body disease, present with executive dysfunction. This similarly occurs with various subcortical dementias. These occur with Parkinson disease, Huntington disease, AIDS-related dementia, and demyelinating disorders that lead to involvement of subcortical white matter connections. Additionally, there is a high incidence of executive dysfunction with vascular disease, whether due to large vessel stroke, small vessel ischemic disease, or ruptured aneurysm (typically of the anterior communicating artery). The anterior cerebral artery and middle cerebral arteries supply the anterior and medial portions and the lateral dorsal frontal cortex, respectively. Primary brain tumors, for example, gliomas, oligodendrogliomas, meningiomas, and pituitary adenomas, may typically affect executive functioning. Various causes of hydrocephalus, particularly normal-pressure hydrocephalus, may present in a similar fashion although a gait disorder may often presage the dementia-associated normal-pressure hydrocephalus.

Temporal Lobe Dysfunction

Because of the complexity of the temporal lobe regions and the high interconnectivity with other brain regions, damage or injury can result in a wide variety of deficits involving many cognitive functions. It is impossible to assess all of them during an office visit or bedside consult. However, it is important to recognize some of the major symptom complexes that may occur with lesions in this elegant portion of our brains. One needs to be able to quickly evaluate the patient for lesions at this critical level through specific interview questions with the patient and family or in either the office or bedside setting. The primary manifestations that are addressed here are personality and affect alterations; language and naming deficits; visuoperceptual difficulties; and lastly memory learning problems.

An understanding of temporal lobe anatomy helps one appreciate the various clinical deficits that can arise from lesions at this level. The temporal lobe is defined as encompassing all brain regions below the Sylvian fissure and anterior to the occipital cortex (Figs. 2-1, 2-5, 2-6). These also include subcortical structures such as the hippocampal formation, the amygdala, and limbic cortex. The temporal lobe is divided into three distinct regions: the lateral area consisting of the superior, middle, and inferior temporal gyri; the inferior temporal cortex containing the auditory and visual areas; and the medial area including the fusiform gyrus and parahippocampal gyrus.

Figure 2-5 Cerebral Insular Cortex.

Figure 2-6 Cerebral Cortex (Medial Surface).

The temporal lobe is characterized by a high prevalence of multisite brain connections through efferent projections extending to the limbic system, basal ganglia, frontal and parietal association regions, as well as afferent projections from the sensory areas. The right and left temporal lobes are connected by the corpus callosum and anterior commissure. This interconnectedness contributes to the diverse cognitive and behavioral changes that can result from injury to the temporal lobes. Each of the temporal lobe regions is important for specific cognitive functions and modifies cognition specific to other regions through the many inherent temporal lobe interconnections.

Language

Functions of the right and left hemispheric regions have individual variations that are contingent upon hemispheric language dominance. Population studies estimate that 90–95% of adults are right handed. Estimates of left-hemisphere dominance for language have been determined by various studies of stroke patients, functional magnetic resonance imaging (fMRI), and intracarotid arterial amobarbital (WADA) investigations. Left brain dominance occurs in more than 95% of right-handers and in almost 20% of left-handers. Right hemisphere or bilateral language distribution is found in approximately 20% of left-handers. The likelihood of right hemisphere language dominance increases with the strength of a patient’s left-handedness and increased frequency of familial left handedness. Thus, a TIA with left-hand weakness could result in transient speech disruption or naming problems, particularly in a left-handed patient or a right hander with left-handed relatives. Knowing which hemisphere is most likely dominant for language is critical to the diagnosis of various cognitive problems.

Left dominant temporal lobe injury leads to major language deficits. Wernicke aphasia is the most classic example occurring with lesions of the left superior temporal gyrus (see Fig. 2-1). Typically, these patients demonstrate spontaneous speech that is fluent with phonemic (mixed syllables) and verbal (incorrect words) paraphasic errors at times referred to as a word salad. In addition, these patients have problems with naming, comprehension, repetition, reading, and writing. There may be total lack or incomplete awareness of these various impairments. Such speech changes can be accompanied by emotional symptoms that are associated with the limbic region.

Circumscribed deficits in language functions sometimes emerge if the temporal lobe is disconnected from other brain regions. One of these disconnection syndromes, Pure Word Deafness, can occur when an intact Wernicke area is disconnected from both auditory cortices. The deafness is only for words, and the patient can hear and interpret normally meaningful nonverbal sounds like a baby crying or phone ringing. Bilateral destructive temporal lobe lesions including the transverse oriented Heschl gyrus impair word comprehension and also the identification of meaningful sounds and result in the syndrome of cortical deafness. These syndromes can result from a number of medical conditions, including bilateral strokes, herpes simplex encephalitis, and other infectious disorders. Patients may also have subtle problems discriminating speech sounds, suggestive of left temporal damage. These patients may complain that people are talking “too fast” or that they “can’t hear.” The problem is not actually the rate of speech; it is difficulty discriminating sounds that are presented quickly. To test this, simply speak more slowly with distinct pauses between each word without changing voice volume or simplifying the words that you are using.

Patients frequently complain of “short-term memory” problems that they describe as a failure to “remember” words (typically nouns) although they can recognize the word that they are searching for if it is provided by someone else. “Forgetting words” is not a memory problem; it is a disorder of language typically associated with impairment of the temporal lobe that may occur with or without a true memory impairment. Object naming is disrupted in all of the aphasic syndromes, and is also a common early symptom in dementias affecting the temporal lobes. It was an early symptom in the patient with frontal temporal dementia described at the beginning of this chapter and is a common early complaint for patients with degenerative disorders such as mild cognitive impairment (amnestic or nonamnestic), Alzheimer disease, and vascular dementia. Lesions in the nonlanguage temporal lobe can result in amusia. This is a collection of disorders wherein patients are unable to recognize musical melodies or specific aspects of music (including even dramatic changes in pitch).

Naming deficits are easily tested using the Mini-Mental State Examination (MMSE) naming items as well as objects available in the patient’s room or your office. If a patient cannot name the specified object that you point to, then provide the first sound of the object name (phonemic cue), such as com for the word computer or laa for the word laptop. If the patient is then able to say the name of the object, then they do know the word but have a problem with retrieval. Word fluency tests are also useful in measuring naming problems associated with temporal lobe dysfunction. In the frontal lobe section you learned to use a word generation task that asks the patient to generate in one minute as many words as he or she can beginning with a particular letter. A variation of that task requires the patient to generate words pertaining to a specific category (i.e., proper names, musical instruments, animals). This task requires the patient to retrieve nouns rapidly. Problems generating restricted category words are suggestive of temporal lobe damage, while problems with generating restricted letter words suggest frontal lobe damage.

Damage to the inferotemporal cortex can result in disorders of visual perception; frequently this occurs without the physician being able to demonstrate precise visual field deficits. The temporal lobes help in processing the visual information. Damage to the right temporal lobe can result in a wide variety of deficits, including inattention to the contralateral left side of visual space (more frequent in right temporal lesions), problems with visual object recognition, and the ability to recognize anomalous aspects of pictures and discriminate faces. There may be problems with perceiving and understanding social cues, such as understanding that their appointment is over when you glance at your watch or when you stand up at the end of an appointment.

Perceptual deficits arising from the temporal lobe are difficult to test because other functions, including attention, organization, spatial orientation, and memory overlap with tasks of perception, making the perceptual component of a deficit difficult to isolate. Damage to either or both temporal lobes may result in perceptual impairment. When using visual material to test perception, the language hemisphere may be helping to process pictures, and the nondominant hemisphere may be contributing to understanding the shapes of words. Patients with acquired alexia are sometimes taught to use visuospatial techniques to help them relearn to read. The nonlanguage hemisphere role in reading is demonstrated below. One of the groups of lines below represents the word “horses” and the other represents the word “elephant.” Can you determine which grouping represents the word “elephant”?

Notice that there are no letters, but because of the right hemisphere contribution you can still identify the word on the left as “elephant” from the contour created by the lines. Similarly, the nonlanguage temporal lobe can also help decode words that are seemingly nonsense if you attend strictly to the letters and rules of phonics. In fact, it deosn’t mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae.

Asking the patient to provide a handwriting sample is very important in order to assess these various problems (Fig. 2-7). Damage to the left temporal region may result in wider right-side margins, spaces, or wide separations between letters or syllables and disrupt the continuity of the writing line. Patients with damage to the left temporal region may also be noted to have a decline in ability to write in script, as opposed to a better-preserved ability to print.

Figure 2-7 Testing for Defects of Higher Cortical Function.

The clock-drawing test that was used to identify frontal lobe deficits is also useful in identifying temporal lobe deficits (see Fig. 2-7). In order to draw a clock, there must be a mental visual representation of what features are essential. Visuospatial abilities are essential to determining the layout and proportions, and for making sure that features are accurate on both sides of space. Visuospatial perception is also a component of evaluating the output and making corrections.

In the clock drawing below, the entire left side is neglected, and the right side is drawn twice because the patient did not attend to his first attempt. This patient had a right temporal lesion causing perceptual problems on the left side of space within the context of intact visual fields.

The clock drawing below demonstrates several types of errors associated with the temporal lobes. The patient has added additional structure (lines that look like spokes in a wheel), in an attempt to compensate for perceptual problems in spacing the numbers. There is a numbering error in the upper left quadrant and the hands are missing. These errors are suggestive of right temporal involvement. In addition, the patient wrote a cue to help remember the time, suggesting compensation for a memory problem. Note, too, that the time cue is incorrect: Rather than 10 past 11, the patient wrote 10 to 11, suggesting a language-processing problem. Memory loss, language problem, and time concept error are all suggestive of temporal lobe deficit.

The temporal lobes are essential in the learning of new information. Damage here will affect memory. The ability to retain information starts with acquisition (attention, sustaining focus, organization), encoding (information processing), storage (retention of information through consolidation), and retrieval (accessing the information that is in storage) of the information that is stored. Explicit or episodic memory is information that can be specifically stated (contextual knowledge, autobiographical information, events, the knowledge in this book). Information that is recalled or influences behavior per se, without conscious intention, that is, procedures such as how to drive a car or ride a bicycle, is called implicit memory. Memory deficits may result if any of these complex stages fail. Damage to different regions of the temporal lobe can result in various breakdowns in the memory encoding and storage process. Damage to the mesial temporal regions, the hippocampal complex, can result in profound memory deficits as is well demonstrated by the famous case of HM.

On December 2, 2008, Henry Gustav Molaison, age 82, died of respiratory failure. If the name is unfamiliar, that’s because for the last 55 years, he was known to the world only as HM. In 1953 Mr. Molaison underwent temporal lobe surgery for severe epilepsy with uncontrolled seizures. Although the surgery was largely successful in reducing seizure frequency, it left him with a profound memory loss and essentially no ability to learn new things. For fifty five years after the surgery, he could recall almost nothing that happened subsequently: births and deaths of family members, the events of 9-11, or what he did that morning. Each time he met a friend, each time he ate at a restaurant, each time he walked into his own home, it was for him, the first time.

Damage to the inferior temporal regions interferes with the intentional retrieval of information. Lesions of the left hemisphere tend to preferentially compromise retrieval of verbal information (e.g., conversations, word lists), whereas right hemisphere damage tends to impair the retrieval of visual information (e.g., misplacing items). Assessment of memory is an important aspect of the mental status exam. Patients with memory deficits frequently have difficulty accurately reporting the type and extent of their memory problems. Interviews with the family are the best way to quickly determine the type of memory impairment and the implication of the memory deficit for that patient. The terminology for memory functions may be confusing and may be used differently by different physicians. Effective communication of results and accurate retesting at a later date require both the use of descriptive terms for documenting memory complaints stated by the family, including examples, and a detailed description of the procedures amount and type of information presented, interval delay, and instructions that you use to test memory. One must specify the number of learning trials or types of problems observed during the learning trials, that is, acquisition. It is important to attend to any strategies, for example, rehearsal, that a patient may use to learn the information, that is, encoding. Note how much information is freely recalled after at least a 10- to 15-minute delay retention, and the improvement in the amount of information recalled with cues when compared to the amount freely recalled, that is, retrieval.

Information and orientation questions are useful in assessing episodic memory. Knowing where you are, the date and the time of day, without looking at a clock, have clinical utility. If the patient is not oriented to time, within 30 minutes, then there are likely to be medication compliance problems. The key to assessing information storage is to ensure that registration and encoding have taken place and to allow for sufficient time for memory to decay, that is, forgetting, prior to testing retention. The memory problems in disorders like early Alzheimer disease may not be apparent when tested following a few minutes’ delay, but they may be evident when tested 15 minutes later. The MMSE registration and recall of three objects is often used to assess memory function. Although a reasonable brief bedside task for the very impaired patient, it is insensitive to impairment in the young or mildly impaired and can result in the underestimation of memory deficits because of the abbreviated list to be learned and short interval delay between registration and recall. The addition of a second recall condition, 10–15 minutes later, at the completion of your examination affords additional time for storage as well as memory decay. This may be very important for detecting modest memory impairment.

Parietal Lobe Dysfunction

The parietal lobe is situated between the frontal and occipital lobes. The central sulcus separates frontal from parietal cortex, while the parietooccipital sulcus separates parietal from occipital cortex (see Fig. 2-1). The Sylvian fissure forms the lateral boundary separating parietal from temporal cortex. The most anterior portion of the parietal lobe, sitting immediately behind the central sulcus, is the primary somatosensory cortex (Brodmann area 3; see Fig. 2-3). More posteriorly, the parietal lobe may be divided into the superior parietal lobule (Brodmann areas 5 and 7) and the inferior parietal lobule (Brodmann areas 39 and 40) (see Fig. 2-3). These areas are separated by the intraparietal sulcus.

The primary role of the parietal lobe is to integrate multimodal sensory information, creating a sensory map of one’s self, the perceived world around you, and the relationship of the self within the world. Recent research in primates elucidated the functional anatomy of the parietal lobe. The posterior parietal lobe is thought to primarily integrate visual and somatosensory data allowing proper hand–eye coordination, spatial localization of objects, proper targeting of eye movements, and accurate gauging of the shape, size, and orientation of objects. Further functional subdivision identifies that the posterior (dorsal) portion provides integration of spatial vision via occipital-parietal connections, the “where” stream, whereas the inferior (ventral) regions involve visual recognition of objects and actions via occipital and temporal connections, the “what” stream. There is a further specialization of function within the parietal lobes determined by lateralization. Number processing and calculation are primarily represented within the left hemisphere whereas sensory integration is predominately defined within the right hemisphere.

Somatosensory integration begins in the primary somatosensory cortex, where basic tactile localization is appreciated. This is evaluated by testing both joint position and two-point discrimination sensory modalities. Once sensory information is received in the primary somatosensory cortex, this then streams posteriorly toward the somatosensory association cortex (see Fig. 2-2). Here, tactile information is integrated to provide discriminatory sensation over larger areas of the body surface for sensory definition of object weight, size and shape, texture, etc. This allows for specialized tactile sensation, such as graphesthesia and stereognosis. Most importantly, this allows the integrative mapping of the spatial, tactile, and visual aspects of one’s body. The sensory mapping of the external world takes place posteriorly in the parietal lobe. There are two “functional maps,” one of the self and the other of the world. These are also integrated, presumably in the heteromodal association area in the right parietotemporal–occipital junction.

Right Parietal Lobe

Patients with lesions at this level develop unilateral neglect of sensory events occurring on their left side when sensory input from those areas seemingly appears to vanish. The patient is unaware of those events, as though they were not happening at all. The patient may be completely unaware of the examiner standing on his left side. Sometimes, this occurs in a milder form, whereby events on the left side of the patient extinguish when competing with sensory events on the right side. Double simultaneous stimulation provides a way to test this at the bedside. When the examiner touches the patient on either side individually, the patient detects each stimulus correctly. However, when the stimuli are presented simultaneously, the patient with neglect will not detect the stimulus on the left side. This may also occur with simultaneous visual stimuli in both visual fields.

A related condition, called asomatognosia, involves the patient’s inability to recognize his own body part. When viewing his own hand, the patient does not recognize it as his own. Moreover, he may misidentify it as someone else’s limb. Anosognosia refers to the patient’s absent recognition of illness or disability, which is not mediated by psychological denial and is not associated with a disturbance of mood (Fig. 2-8). A milder version of neglect may occur while writing or drawing. The patient may draw a clock and place all the numbers and even the hands within the right hemispace of the clock face. Visuospatial impairment is relatively common following right parietal lesions. This may be seen on construction tests, where the patient is asked to copy shapes, such as a clock, a cube, or overlapping geometric figures (see Fig. 2-7).

Figure 2-8 Nondominant Hemisphere Higher Cortical Function.

Dressing apraxia is a fascinating condition though likely a misnomer. This condition involves loss of ability to dress in the absence of weakness or primary sensory loss. This is related to the patient having impaired spatial processing and body mapping and thus losing their ability to dress appropriately. Typically these individuals are unable to distinguish where to place their arm and/or leg within an article of clothing. This is amplified in the office or at the bedside when the examiner takes a shirt, for example, rolling it up, turning a sleeve inside out, and asking the patient to put it on appropriately. Such patients are classically befuddled by this setting and cannot appropriately place the garment on their body; they have difficulty aligning their clothes properly, rather than forgetting the proper motor sequence for dressing. They cannot rearrange the shirt appropriately to insert their arms correctly into the sleeves. It is not a true apraxia because the motor program for dressing is presumably intact. Sometimes, the dressing difficulty occurs only on the left side with a right parietal lesion. In this circumstance, this finding is considered a part of the neglect syndrome.

Occipital Lobe Dysfunction

The primary function of the occipital cortex is to process and organize visual information. The calcarine area, Brodmann area 17 (Figs. 2-9 to 2-11; Table 2-3), represents the primary visual cortex. It is located within the medial side of the occipital cortex along the calcarine sulcus. This region is also called the striate cortex because of prominent myelin striation, called the Stria of Gennari. The portion of the occipital cortex that lies beyond the primary visual area is termed extra-striate cortex; it subserves higher order visual processing, including color discrimination, motion perception, shape detection, etc. Each visual area contains a full map of the mentally perceived visual world.

Figure 2-9 Cerebral Cortex (Medial Surface of Brain Lobes and Functional Areas).

Figure 2-10 Cerebral Cortex (Inferior Surface).

Figure 2-11 Occipital Lobe Functional Anatomy.

Table 2-3 Inferior Surface of the Brain

From Rubin M, Safdieh J. Netter’s Concise Neuroanatomy, Philadelphia, Saunders, 2007, p. 37.

The primary visual cortex provides a low-level description of visual object shape, spatial distribution, and color properties. Projections from the extra-striate cortex branch ventrally toward temporal lobes and dorsally toward parietal lobes. The visual information from the ventral stream integrates with temporal lobe association areas to allow recognition of objects, people, and places. Visual information travelling through the dorsal stream merges with parietal association areas to allow proper visual orientation of objects in the environment and of the self within the environment (see Fig. 2-2). There are few cognitive syndromes attributable to disorders placing the occipital lobe in isolation.

Cortical blindness follows bilateral occipital lobe injury. Patients are completely blind but, paradoxically, may deny their symptom. Frequently these individuals describe scenes with extraordinary detail, often with bizarre contextual information. These patients function as though delusional, insisting their vision is intact despite clear evidence to the contrary, lying down, or being unable to manipulate any object they see. This condition, also known as Anton syndrome, most commonly occurs after bilateral posterior cerebral artery strokes, progressive multifocal leukoencephalopathy, and posterior reversible leukoencephalopathy.

Pure alexia without agraphia is a disconnection syndrome that occurs when a lesion within the left occipital lobe extends to involve fibers traversing across the splenium of the corpus callosum from the right occipital lobe (see Fig. 2-10). This process causes loss of the ability to read while sparing all other language function. All cases include a right homonymous hemianopsia (hemifield cut). Visual information recorded by either or both occipital lobes must be directed to the posterior left temporal lobe per se in order for the individual to detect and process the visual symbols of language. Therefore, the combined left occipital lobe and splenium lesion effectively blocks data—perceived in the left visual field and recorded in the right occipital lobe—from being sent to the contralateral dominant temporal lobe. Thus, even though such individuals can see objects in their left hemifield, utilizing their still intact right occipital lobe, all vision from this cortex effectively has a conduction block vis-à-vis the precise act of reading. This is because any visual symbols of language are no longer being transmitted through the splenium and thus do not reach the dominant language areas. In essence, this lesion disconnects the right visual cortex visual information from reaching the contralateral language, and writing centers. Although the left hemifield remains intact, its potential language information cannot be “seen” by the dominant left temporal lobe. In effect, this condition could also be called pure word blindness.

In summary, the clinician may use a variety of higher cortical function assessment modalities to evaluate patients with primary cerebral cortex disorders. Some common examples of these methods are outlined in Figure 2-7.

Cerebellum

There has been longstanding debate regarding the cerebellum and the role it plays in cognition and behavior. During the 17th century, debates occurred as to whether the cerebellum was critical for vegetative functions and survival. During the 18th century, some considered whether the cerebellum was the center for sexual function or pure motor functioning, a more limited approach. In the 19th century, the sole proposed focus was directed at its role in coordinated movement. More recently, in the latter half of the 20th century, neuroscientists have come to recognize that the cerebellum may be responsible for more than just a balance and coordination function; however, for some this is still a debatable topic. Most think of motor symptoms when considering cerebellar disorders, and these would consist of ataxia, dysmetria, disordered eye movement, scanning dysarthria, dysphagia, and tremor.

However, the cerebellum is connected to the contralateral cerebral hemispheres, the dorsolateral prefrontal cortex, posterior parietal and superior temporal areas, and occipital lobes, as well as limbic structures. Thus, it is not surprising that there is an increased focus on the cerebellum having an important role in cognitive functioning. Kalashnikova et al. studied 25 patients with isolated cerebellar infarcts and found that 88% exhibited cognitive impairment. Based on the pattern of deficits, they divided them into two groups: dysfunction of the prefrontal and premotor areas and dysfunction of the posterior parietal/temporal/occipital area.

Schmahmann and Sherman have postulated that there is a cerebellar cognitive affective syndrome. They attribute this to cerebellar lesions that are connected with the associative zones. Cognitive affective syndrome (CAS) is associated with executive dysfunction (e.g., planning, set-shifting, abstract reasoning, divided attention, working memory, perseveration, verbal fluency, and memory deficits due to executive dysfunction), speech disorder (agrammatism, dysprosody, mild anomia), visual spatial dysfunction (difficulty copying and conceptualizing drawings), and personality changes (flat affect, disinhibition, impulsivity, pathologic laughing/crying). However, the degree of impairment tends to depend on the location of cerebellar damage.

Specifically, those with acute cerebellar stroke, slowly progressive cerebellar degenerations, or small strokes within the cerebellum, primarily supplied by the superior cerebellar artery, tended to exhibit very subtle deficits. In contrast, those with bilateral or large unilateral strokes in the territory of the posterior inferior cerebellar arteries, or those with subacute onset of pancerebellar disorders, exhibited more striking deficits. There is a wide range of possible etiologies of cerebellar disorders, including developmental, genetic, toxic, vascular, metabolic, infectious, tumor, trauma, degenerative, and autoimmune. Thus, these patients not only have cerebellar involvement but frequently also have involvement of other areas of the cerebrum.

However, the neurophysiologic role of the cerebellum in cognition is still in relative infancy. It is likely that some study findings will be replicated and it will become more widely accepted that the cerebellum does have a significant role in cognitive functioning. Bedside testing of cerebellar motor dysfunction requires observation of gait and balance, the presence of dysmetria with use of the extremities, tendency to overshoot or overcorrect, and eye movement abnormalities.

Aphasia

Language encompasses multiple cortical regions and is not classifiable within strict cortical anatomic borders. Impairment of language function is a common neurologic symptom presenting acutely, as in stroke, or more insidiously, as in primary progressive aphasia. The classic nomenclature of the aphasia syndromes is largely based on lesion analysis in cases of stroke or tumor. These syndromes postulate distinct cortical regions responsible for the various phases of language processing from comprehension to expression. Broca syndrome is characterized by stuttering, agrammatical, effortful, and telegraphic language. This was thought to be an expressive language disorder typical of anterior frontal lesions (so-called motor aphasia). Wernicke aphasia, typified as a receptive comprehension language disorder, is characterized by the fluent expression of wrong or nonexistent words and syllables that is sometimes referred to as a word salad. Receptive language disorders were thought to be related to lesions of the more posterior temporal parietal cortex (Fig. 2-12).

Figure 2-12 Dominant Hemisphere Language Dysfunction.

Other aphasia syndromes, such as conduction aphasia, anomic aphasia, and the transcortical aphasias emerged to describe aphasic syndromes that did not fit neatly into the broader forms of expressive and receptive aphasias. These syndromes were traditionally associated with strokes in various left MCA strokes or tumors and thought to have some localizing value. However, exceptions to the traditional classification of aphasia occur commonly. For example, it is not unusual for a posterior MCA division stroke to produce a nonfluent aphasia. Moreover, the progressive aphasia syndromes often produce characteristic language disorders that do not fit any of the traditional aphasia paradigms. Indeed, even in the acute stroke setting, the classification of aphasia as expressive or receptive, motor or sensory, nonfluent or fluent, is too simplistic and often inaccurate. Very few patients present with pure aphasia syndromes.

Often, patients with aphasia present to the neurologist complaining of word-finding difficulty; this is a broad-based symptom that is not always the result of a primary language disorder. Rather, it may be a manifestation of either inattention or a memory impairment. Therefore, the assessment of language must distinguish primary language disorders from other cognitive deficits, that is, secondary word-finding impairment. The patient presenting with progressive primary language disturbance often does not fit neatly into the traditional neuroanatomic aphasia classifications (Table 2-4). Therefore, further discussion of language assessment will not focus on the traditional bedside aphasia exam, namely, tests of fluency, comprehension, naming, repetition, writing, and reading. Rather, we will review newer techniques for the examination of language elucidated through study of patients with primary progressive aphasia (Fig. 2-13).

Table 2-4 Characteristics of Aphasias

Figure 2-13 Structural Anatomy of Word-Finding Difficulty in Degenerative Disorders.

Language may be defined as the attempt to convey a thought in verbal, spoken, or written form. This seems to occur in four stages, including speech initiation, speech content, speech structure, and motor programming of speech.

Stage I: Initiation of speech involves the ability to generate and plan a spoken message. Patients with speech initiation problems are quiet, as though they have nothing to say, so-called dynamic aphasia. Responses are terse and elaboration is absent. Patients speak only in response to conversation, not to initiate conversation. Although the amount of speech is reduced, the content and structure of spoken language are normal. This is often seen in patients with anterior frontal and subcortical abnormalities. These individuals often appear inert and slow to respond in general, sometimes referred to as appearing as a “bump on a log.”

Stage II: The content of the message comes next once the mental plan for speech is set. This includes vocabulary and concepts. Content is assessed at the level of single words or in the way words are combined. Loss of vocabulary is the major abnormality encountered in this setting. The patient substitutes approximate words or imprecise expressions for words they cannot conjure. Speech seems vague and deficient of meaning in more severe cases. Errors of meaning (semantic paraphasias) may occur. Stereotyped expressions, such as clichés, are overutilized. This is characteristic of semantic dementia, a variant of frontotemporal lobar degeneration.

A variation of this occurs in Alzheimer disease, where the patient cannot retrieve words from storage, gradually and progressively developing logopenic aphasia. Here the content of the message is impaired because of a loss for words, rather than a loss of the meaning of words. At the level of word combinations, there is a lack of coherence due to incomplete sentences, tangentiality, fragmented phrases, etc. It is hard to follow the patient’s train of thought in these cases. This also occurs acutely, most commonly in states of delirium such as alcohol withdrawal.

Stage III: Grammar and phonology is the basis for the structure of spoken language. Grammar is the ordering of words into normal sentence structure, that is, subject and predicate. It also includes the use of function words such as prepositions and conjunctions. Phonology refers to the selection of individual sounds and syllables to form spoken words. Agrammatism leads to telegraphic speech, composed of single words or phrases, often omitting connector words. Phonologic errors lead to errors in particular sounds within words, also known as phonemic paraphasic errors. For example, saying “aminal” for “animal,” or “nucular” for “nuclear.” These types of errors are common in progressive nonfluent aphasia.

Stage IV: Once the structure of the message is defined, the message is conveyed to the motor areas for speech where phonetics, articulation, and prosody are applied and the message is spoken. Impairment at this phase is often characterized by apraxia of speech, or the loss of learned motor programming for speech production. This often produces great frustration and effortful speech, with severe loss of fluency, phonetic errors, and impaired speech timing and rhythm, as seen in the case vignette at the beginning of this chapter.

The most important aspect of language assessment is carefully listening to conversational language during the patient interview. If the patient is not very talkative, the examiner may present him or her with a picture to describe. Further tests of naming, repetition, writing, and reading all provide additional important information. In the case of progressive aphasia, the nature of language disturbance may have significant implication in identifying the underlying neurodegenerative disease. Indeed, assessment of language in this way has proven utility in localizing cortical regions attributed to various primary progressive aphasic syndromes (see Fig. 2-13). This approach elaborates on the classic aphasia exam, providing a better understanding of language processing and improving localization during examination.