The clinical examination of language should include the assessment of naming, spontaneous speech, comprehension, repetition, reading, and writing. A deficit of naming (anomia) is the single most common finding in aphasic patients. When asked to name a common object (pencil or wristwatch), the patient may fail to come up with the appropriate word, may provide a circumlocutious description of the object ("the thing for writing"), or may come up with the wrong word (paraphasia). If the patient offers an incorrect but related word ("pen" for "pencil"), the naming error is known as a semantic paraphasia; if the word approximates the correct answer but is phonetically inaccurate ("plentil" for "pencil"), it is known as a phonemic paraphasia. Asking the patient to name body parts, geometric shapes, and component parts of objects (lapel of coat, cap of pen) can elicit mild forms of anomia in patients who otherwise can name common objects. In most anomias, the patient cannot retrieve the appropriate name when shown an object but can point to the appropriate object when the name is provided by the examiner. This is known as a one-way (or retrieval-based) naming deficit. A two-way naming deficit exists if the patient can neither provide nor recognize the correct name, indicating the likely presence of a comprehension impairment for the word. Spontaneous speech is described as "fluent" if it maintains appropriate output volume, phrase length, and melody or as "nonfluent" if it is sparse and halting and average utterance length is below four words. The examiner also should note if the speech is paraphasic or circumlocutious; if it shows a relative paucity of substantive nouns and action verbs versus function words (prepositions, conjunctions); and if word order, tenses, suffixes, prefixes, plurals, and possessives are appropriate. Comprehension can be tested by assessing the patient's ability to follow conversation, asking yes-no questions ("Can a dog fly?", "Does it snow in summer?") or asking the patient to point to appropriate objects ("Where is the source of illumination in this room?"). Statements with embedded clauses or a passive voice construction ("If a tiger is eaten by a lion, which animal stays alive?") help assess the ability to comprehend complex syntactic structure. Commands to close or open the eyes, stand up, sit down, or roll over should not be used to assess overall comprehension since appropriate responses aimed at such axial movements can be preserved in patients who otherwise have profound comprehension deficits.
Repetition is assessed by asking the patient to repeat single words, short sentences, or strings of words such as "No ifs, ands, or buts." The testing of repetition with tongue twisters such as "hippopotamus" and "Irish constabulary" provides a better assessment of dysarthria and pallilalia than of aphasia. Aphasic patients who have little difficulty with tongue twisters may have a particularly hard time repeating a string of function words. It is important to make sure that the number of words does not exceed the patient's attention span. Otherwise, the failure of repetition becomes a reflection of the narrowed attention span rather than an indication of an aphasic deficit. Reading should be assessed for deficits in reading aloud as well as comprehension. Writing is assessed for spelling errors, word order, and grammar. Alexia describes an inability to either read aloud or comprehend single words and simple sentences; agraphia (or dysgraphia) is used to describe an acquired deficit in the spelling or grammar of written language.
The correspondence between individual deficits of language function and lesion location does not display a rigid one-to-one relationship and should be conceptualized within the context of the distributed network model. Nonetheless, the classification of aphasias into specific clinical syndromes helps determine the most likely anatomic distribution of the underlying neurologic disease and has implications for etiology and prognosis (Table 26-1). The syndromes listed in Table 26-1 are most applicable to aphasias caused by cerebrovascular accidents (CVAs). They can be divided into "central" syndromes, which result from damage to the two epicenters of the language network (Broca's and Wernicke's areas), and "disconnection" syndromes, which arise from lesions that interrupt the functional connectivity of those centers with each other and with the other components of the language network. The syndromes outlined below are idealizations; pure syndromes occur rarely.
Table 26-1 Clinical Features of Aphasias and Related Conditions |Favorite Table|Download (.pdf)
Table 26-1 Clinical Features of Aphasias and Related Conditions
|Comprehension||Repetition of Spoken Language||Naming||Fluency|
|Wernicke's||Impaired||Impaired||Impaired||Preserved or increased|
|Broca's||Preserved (except grammar)||Impaired||Impaired||Decreased|
|Nonfluent (motor) transcortical||Preserved||Preserved||Impaired||Impaired|
|Fluent (sensory) transcortical||Impaired||Preserved||Impaired||Preserved|
|Isolation||Impaired||Echolalia||Impaired||No purposeful speech|
|Anomic||Preserved||Preserved||Impaired||Preserved except for word-finding pauses|
|Pure word deafness||Impaired only for spoken language||Impaired||Preserved||Preserved|
|Pure alexia||Impaired only for reading||Preserved||Preserved||Preserved|
Comprehension is impaired for spoken and written language, for single words as well as sentences. Language output is fluent but is highly paraphasic and circumlocutious. The tendency for paraphasic errors may be so pronounced that it leads to strings of neologisms, which form the basis of what is known as "jargon aphasia." Speech contains large numbers of function words (e.g., prepositions, conjunctions) but few substantive nouns or verbs that refer to specific actions. The output is therefore voluminous but uninformative. For example, a patient attempts to describe how his wife accidentally threw away something important, perhaps his dentures: "We don't need it anymore, she says. And with it when that was downstairs was my teeth-tick…a…den…dentith…my dentist. And they happened to be in that bag…see? How could this have happened? How could a thing like this happen…So she says we won't need it anymore…I didn't think we'd use it. And now if I have any problems anybody coming a month from now, 4 months from now, or 6 months from now, I have a new dentist. Where my two…two little pieces of dentist that I use…that I…all gone. If she throws the whole thing away…visit some friends of hers and she can't throw them away."
Gestures and pantomime do not improve communication. The patient does not seem to realize that his or her language is incomprehensible and may appear angry and impatient when the examiner fails to decipher the meaning of a severely paraphasic statement. In some patients this type of aphasia can be associated with severe agitation and paranoid behaviors. One area of comprehension that may be preserved is the ability to follow commands aimed at axial musculature. The dissociation between the failure to understand simple questions ("What is your name?") in a patient who rapidly closes his or her eyes, sits up, or rolls over when asked to do so is characteristic of Wernicke's aphasia and helps differentiate it from deafness, psychiatric disease, or malingering. Patients with Wernicke's aphasia cannot express their thoughts in meaning-appropriate words and cannot decode the meaning of words in any modality of input. This aphasia therefore has expressive as well as receptive components. Repetition, naming, reading, and writing also are impaired.
The lesion site most commonly associated with Wernicke's aphasia is the posterior portion of the language network and tends to involve at least parts of Wernicke's area. An embolus to the inferior division of the middle cerebral artery, to the posterior temporal or angular branches in particular, is the most common etiology (Chap. 370). Intracerebral hemorrhage, severe head trauma, and neoplasm are other causes. A coexisting right hemianopia or superior quadrantanopia is common and mild right nasolabial flattening may be found, but otherwise the examination is often unrevealing. The paraphasic, neologistic speech in an agitated patient with an otherwise unremarkable neurologic examination may lead to the suspicion of a primary psychiatric disorder such as schizophrenia or mania, but the other components characteristic of acquired aphasia and the absence of prior psychiatric disease usually settle the issue. Some patients with Wernicke's aphasia due to intracerebral hemorrhage or head trauma may improve as the hemorrhage or the injury heals. In most other patients, prognosis for recovery of language function is guarded.
Speech is nonfluent, labored, interrupted by many word-finding pauses, and usually dysarthric. It is impoverished in function words but enriched in meaning-appropriate nouns and verbs. Abnormal word order and the inappropriate deployment of bound morphemes (word endings used to denote tenses, possessives, or plurals) lead to a characteristic agrammatism. Speech is telegraphic and pithy but quite informative. In the following passage, a patient with Broca's aphasia describes his medical history: "I see…the dotor, dotor sent me…Bosson. Go to hospital. Dotor…kept me beside. Two, tee days, doctor send me home."
Output may be reduced to a grunt or single word ("yes" or "no"), which is emitted with different intonations in an attempt to express approval or disapproval. In addition to fluency, naming and repetition are impaired. Comprehension of spoken language is intact except for syntactically difficult sentences with a passive voice structure or embedded clauses. Reading comprehension also is preserved with the occasional exception of a specific inability to read small grammatical words such as conjunctions and pronouns. The last two features indicate that Broca's aphasia is not just an "expressive" or "motor" disorder and that it also may involve a comprehension deficit for function words and syntax. Patients with Broca's aphasia can be tearful, easily frustrated, and profoundly depressed. Insight into their condition is preserved, in contrast to Wernicke's aphasia. Even when spontaneous speech is severely dysarthric, the patient may be able to display a relatively normal articulation of words when singing. This dissociation has been used to develop specific therapeutic approaches (melodic intonation therapy) for Broca's aphasia. Additional neurologic deficits usually include right facial weakness, hemiparesis or hemiplegia, and a buccofacial apraxia characterized by an inability to carry out motor commands involving oropharyngeal and facial musculature (e.g., patients are unable to demonstrate how to blow out a match or suck through a straw). Visual fields are intact. The cause is most often infarction of Broca's area (the inferior frontal convolution; "B" in Fig. 26-1) and surrounding anterior perisylvian and insular cortex due to occlusion of the superior division of the middle cerebral artery (Chap. 370). Mass lesions, including tumor, intracerebral hemorrhage, and abscess, also may be responsible. Small lesions confined to the posterior part of Broca's area may lead to a nonaphasic and often reversible deficit of speech articulation that usually is accompanied by mild right facial weakness. When the cause of Broca's aphasia is stroke, recovery of language function generally peaks within 2 to 6 months, after which time further progress is limited.
Speech output is nonfluent, and comprehension of spoken language is severely impaired. Naming, repetition, reading, and writing also are impaired. This syndrome represents the combined dysfunction of Broca's and Wernicke's areas and usually results from strokes that involve the entire middle cerebral artery distribution in the left hemisphere. Most patients are initially mute or say a few words, such as "hi" or "yes." Related signs include right hemiplegia, hemisensory loss, and homonymous hemianopia. Occasionally, a patient with a lesion in Wernicke's area will present with a global aphasia that soon resolves into Wernicke's aphasia.
Speech output is fluent but paraphasic, comprehension of spoken language is intact, and repetition is severely impaired. Naming and writing also are impaired. Reading aloud is impaired, but reading comprehension is preserved. The lesion sites spare Broca's and Wernicke's areas but may induce a functional disconnection between the two so that neural word representations formed in Wernicke's area and adjacent regions cannot be conveyed to Broca's area for assembly into corresponding articulatory patterns. Occasionally, a Wernicke's area lesion gives rise to a transient Wernicke's aphasia that rapidly resolves into a conduction aphasia. The paraphasic output in conduction aphasia interferes with the ability to express meaning, but this deficit is not nearly as severe as the one displayed by patients with Wernicke's aphasia. Associated neurologic signs in conduction aphasia vary according to the primary lesion site.
Nonfluent Transcortical Aphasia (Transcortical Motor Aphasia)
The features are similar to those of Broca's aphasia, but repetition is intact and agrammatism may be less pronounced. The neurologic examination may be otherwise intact, but a right hemiparesis also can exist. The lesion site disconnects the intact language network from prefrontal areas of the brain and usually involves the anterior watershed zone between anterior and middle cerebral artery territories or the supplementary motor cortex in the territory of the anterior cerebral artery.
Fluent Transcortical Aphasia (Transcortical Sensory Aphasia)
Clinical features are similar to those of Wernicke's aphasia, but repetition is intact. The lesion site disconnects the intact core of the language network from other temporoparietal association areas. Associated neurologic findings may include hemianopia. Cerebrovascular lesions (e.g., infarctions in the posterior watershed zone) and neoplasms that involve the temporoparietal cortex posterior to Wernicke's area are the most common causes.
This rare syndrome represents a combination of the two transcortical aphasias. Comprehension is severely impaired, and there is no purposeful speech output. The patient may parrot fragments of heard conversations (echolalia), indicating that the neural mechanisms for repetition are at least partially intact. This condition represents the pathologic function of the language network when it is isolated from other regions of the brain. Broca's and Wernicke's areas tend to be spared, but there is damage to the surrounding frontal, parietal, and temporal cortex. Lesions are patchy and can be associated with anoxia, carbon monoxide poisoning, or complete watershed zone infarctions.
This form of aphasia may be considered the "minimal dysfunction" syndrome of the language network. Articulation, comprehension, and repetition are intact, but confrontation naming, word finding, and spelling are impaired. Speech is enriched in function words but impoverished in substantive nouns and verbs denoting specific actions. Language output is fluent but paraphasic, circumlocutious, and uninformative. Fluency may be interrupted by word-finding hesitations. The lesion sites can be anywhere within the left hemisphere language network, including the middle and inferior temporal gyri. Anomic aphasia is the single most common language disturbance seen in head trauma, metabolic encephalopathy, and Alzheimer's disease.
The most common causes are either bilateral or left-sided middle cerebral artery (MCA) strokes affecting the superior temporal gyrus. The net effect of the underlying lesion is to interrupt the flow of information from the auditory association cortex to Wernicke's area. Patients have no difficulty understanding written language and can express themselves well in spoken or written language. They have no difficulty interpreting and reacting to environmental sounds since primary auditory cortex and subcortical auditory relays are intact. Since auditory information cannot be conveyed to the language network, however, it cannot be decoded into neural word representations, and the patient reacts to speech as if it were in an alien tongue that cannot be deciphered. Patients cannot repeat spoken language but have no difficulty naming objects. In time, patients with pure word deafness teach themselves lipreading and may appear to have improved. There may be no additional neurologic findings, but agitated paranoid reactions are common in the acute stages. Cerebrovascular lesions are the most common cause.
Pure Alexia Without Agraphia
This is the visual equivalent of pure word deafness. The lesions (usually a combination of damage to the left occipital cortex and to a posterior sector of the corpus callosum—the splenium) interrupt the flow of visual input into the language network. There is usually a right hemianopia, but the core language network remains unaffected. The patient can understand and produce spoken language, name objects in the left visual hemifield, repeat, and write. However, the patient acts as if illiterate when asked to read even the simplest sentence because the visual information from the written words (presented to the intact left visual hemifield) cannot reach the language network. Objects in the left hemifield may be named accurately because they activate nonvisual associations in the right hemisphere, which in turn can access the language network through transcallosal pathways anterior to the splenium. Patients with this syndrome also may lose the ability to name colors, although they can match colors. This is known as a color anomia. The most common etiology of pure alexia is a vascular lesion in the territory of the posterior cerebral artery or an infiltrating neoplasm in the left occipital cortex that involves the optic radiations as well as the crossing fibers of the splenium. Since the posterior cerebral artery also supplies medial temporal components of the limbic system, a patient with pure alexia also may experience an amnesia, but this is usually transient because the limbic lesion is unilateral.
There is an acute onset of severely impaired fluency (often mutism), which cannot be accounted for by corticobulbar, cerebellar, or extrapyramidal dysfunction. Recovery is the rule and involves an intermediate stage of hoarse whispering. Writing, reading, and comprehension are intact, and so this is not a true aphasic syndrome. Partial lesions of Broca's area or subcortical lesions that undercut its connections with other parts of the brain may be present. Occasionally, the lesion site is on the medial aspects of the frontal lobes and may involve the supplementary motor cortex of the left hemisphere.
This generic term designates a complex motor deficit that cannot be attributed to pyramidal, extrapyramidal, cerebellar, or sensory dysfunction and that does not arise from the patient's failure to understand the nature of the task. The form that is encountered most frequently in clinical practice is known as ideomotor apraxia. Commands to perform a specific motor act ("cough," "blow out a match") or pantomime the use of a common tool (a comb, hammer, straw, or toothbrush) in the absence of the real object cannot be followed. The patient's ability to comprehend the command is ascertained by demonstrating multiple movements and establishing that the correct one can be recognized. Some patients with this type of apraxia can imitate the appropriate movement (when it is demonstrated by the examiner) and show no impairment when handed the real object, indicating that the sensorimotor mechanisms necessary for the movement are intact. Some forms of ideomotor apraxia represent a disconnection of the language network from pyramidal motor systems: commands to execute complex movements are understood but cannot be conveyed to the appropriate motor areas even though the relevant motor mechanisms are intact. Buccofacial apraxia involves apraxic deficits in movements of the face and mouth. Limb apraxia encompasses apraxic deficits in movements of the arms and legs. Ideomotor apraxia almost always is caused by lesions in the left hemisphere and is commonly associated with aphasic syndromes, especially Broca's aphasia and conduction aphasia. Its presence cannot be ascertained in patients with language comprehension deficits. The ability to follow commands aimed at axial musculature ("close the eyes," "stand up") is subserved by different pathways and may be intact in otherwise severely aphasic and apraxic patients. Since the handling of real objects is not impaired, ideomotor apraxia by itself causes no major limitation of daily living activities. Patients with lesions of the anterior corpus callosum can display ideomotor apraxia confined to the left side of the body, a sign known as sympathetic dyspraxia. A severe form of sympathetic dyspraxia known as the alien hand syndrome is characterized by additional features of motor disinhibition on the left hand.
Ideational apraxia refers to a deficit in the execution of a goal-directed sequence of movements in patients who have no difficulty executing the individual components of the sequence. For example, when the patient is asked to pick up a pen and write, the sequence of uncapping the pen, placing the cap at the opposite end, turning the point toward the writing surface, and writing may be disrupted, and the patient may be seen trying to write with the wrong end of the pen or even with the removed cap. These motor sequencing problems usually are seen in the context of confusional states and dementias rather than focal lesions associated with aphasic conditions. Limb-kinetic apraxia involves a clumsiness in the actual use of tools that cannot be attributed to sensory, pyramidal, extrapyramidal, or cerebellar dysfunction. This condition can emerge in the context of focal premotor cortex lesions or corticobasal degeneration.
The combination of acalculia (impairment of simple arithmetic), dysgraphia (impaired writing), finger anomia (an inability to name individual fingers such as the index and thumb), and right-left confusion (an inability to tell whether a hand, foot, or arm of the patient or examiner is on the right or left side of the body) is known as Gerstmann's syndrome. In making this diagnosis it is important to establish that the finger and left-right naming deficits are not part of a more generalized anomia and that the patient is not otherwise aphasic. When Gerstmann's syndrome is seen in isolation, it is commonly associated with damage to the inferior parietal lobule (especially the angular gyrus) in the left hemisphere.
Variations of melodic stress and intonation influence the meaning and impact of spoken language. For example, the two statements "He is clever." and "He is clever?" contain an identical word choice and syntax but convey vastly different messages because of differences in the intonation and stress with which the statements are uttered. This aspect of language is known as prosody. Damage to perisylvian areas in the right hemisphere can interfere with speech prosody and can lead to syndromes of aprosodia. Damage to right hemisphere regions corresponding to Wernicke's area can selectively impair decoding of speech prosody, whereas damage to right hemisphere regions corresponding to Broca's area yields a greater impairment in the ability to introduce meaning-appropriate prosody into spoken language. The latter deficit is the most common type of aprosodia identified in clinical practice; the patient produces grammatically correct language with accurate word choice, but the statements are uttered in a monotone that interferes with the ability to convey the intended stress and affect. Patients with this type of aprosodia give the mistaken impression of being depressed or indifferent.
Damage to subcortical components of the language network (e.g., the striatum and thalamus of the left hemisphere) also can lead to aphasia. The resulting syndromes contain combinations of deficits in the various aspects of language but rarely fit the specific patterns described in Table 26-1. In a patient with a CVA, an anomic aphasia accompanied by dysarthria or a fluent aphasia with hemiparesis should raise the suspicion of a subcortical lesion site.
Aphasias caused by cerebrovascular accidents start suddenly and display maximal deficits at the onset. The underlying lesion is relatively circumscribed and is associated with a total loss of neural function in at least part of the lesion site. These are the "classic" aphasias described above. Aphasias caused by neurodegenerative diseases have an insidious onset and a relentless progression so that the symptomatology changes over time. Since the neuronal loss within the areas encompassed by the neurodegeneration is partial and since it tends to include multiple components of the language network, the clinico-anatomic patterns are different from those described in Table 26-1.
Clinical Presentation and Diagnosis of Primary Progressive Aphasia (PPA)
When a neurodegenerative disease selectively undermines language function, a clinical diagnosis of PPA is made. A patient with PPA comes to medical attention because of word-finding difficulties, abnormal speech patterns, word-comprehension impairments, or spelling errors of recent onset. PPA is diagnosed when other mental faculties, such as memory for daily events, visuospatial skills (assessed by tests of drawing and face recognition), and comportment (assessed by history obtained from a third party), remain relatively intact; when language is the major area of dysfunction for the first few years of the disease; and when structural brain imaging does not reveal a specific lesion, other than atrophy, that accounts for the language deficit. Impairments in other cognitive functions may emerge eventually, but the language dysfunction remains the most salient feature and deteriorates most rapidly throughout the illness.
The language impairment in PPA varies from patient to patient. Some patients cannot find the right words to express thoughts; others cannot understand the meaning of heard or seen words; still others cannot name objects in the environment. The language impairment can be fluent (that is, with normal articulation, flow, and number of words per utterance) or nonfluent. The single most common sign of primary progressive aphasia is an inability to come up with the right word during conversation and/or an inability to name objects shown by the examiner (anomia). Distinct forms of agrammatism and/or word comprehension deficits also can arise. The agrammatism consists of inappropriate word order and misuse of small grammatical words. Comprehension deficits, if present, start with an occasional inability to understand single low-frequency words and gradually progress to encompass the comprehension of conversational speech.
The impairments of syntax, comprehension, naming, or writing in PPA form slightly different patterns from those seen in CVA-caused aphasias. Three subtypes of PPA can be recognized: an agrammatic variant characterized by poor fluency and impaired grammar, a semantic variant characterized by preserved fluency and syntax but poor single word comprehension, and a logopenic variant characterized by preserved syntax and comprehension but frequent word-finding pauses during spontaneous speech. The agrammatic variant also is known as progressive nonfluent aphasia and displays similarities to Broca's aphasia. However, dysarthria is usually absent. The semantic variant of PPA displays similarities to Wernicke's aphasia, but the comprehension difficulty tends to be most profound for single words denoting concrete objects.
The three variants of PPA display overlapping distributions of neuronal loss, but the agrammatic variant is most closely associated with atrophy in the anterior parts of the language network (where Broca's area is located), the semantic variant with atrophy in the anterior temporal components of the language network, and the logopenic variant with atrophy in the temporoparietal component of the language network. The abnormalities may remain confined to the left hemisphere perisylvian and anterior temporal cortices initially, but gradual deterioration in PPA leads to a loss of syndromic specificity as the disease progresses.
In the majority of PPA cases, the neuropathology falls within the family of frontotemporal lobar degenerations (FTLDs) and displays various combinations of focal neuronal loss, gliosis, tau-positive inclusions including Pick bodies, and tau-negative TDP-43 inclusions. Familial forms of PPA with TDP-43 inclusions recently were linked to mutations of the progranulin gene on chromosome 17. The agrammatic variant most frequently is associated with tauopathy, whereas the semantic variant is most closely associated with TDP-43 inclusions. Alzheimer's pathology is seen most frequently in the logopenic variant. The clinical subtyping of PPA thus may help predict the nature of the underlying neuropathology. The intriguing possibility has been raised that a personal or family history of dyslexia may be a risk factor for primary progressive aphasia, at least in some patients, suggesting that this disease may arise on a background of genetic or developmental vulnerability that affects language-related areas of the brain.