17
2 Signs of Aphasia ANTONIO R. DAMASIO This chapter discusses the clinical presentation of the aphasias, the major types, and the principal signs. A discussion of the neuroanatomy and neu- rophysiology of language (and, by extension, a discussion of the phys- iopathology of the aphasias) is outside the scope of this text. However, the comments on the clinical evidence presented here reflect a particular theo- retical perspective on neuroanatomy, neurophysiology, and physiopath- ology, which has been documented elsewhere in detail (A. Damasio, 1989a, 1989b, 1989c; A. R. Damasio & Damasio, 1994; H. Damasio & Damasio, 1989). It is important to note that when I refer to the LOCALIZATION VALUEor CORRELATE of a given sign, I do not mean to say that the correlated brain lo- cus normally operates to produce whatever function a sign reports as miss- ing. In the perspective outlined in the earlier articles, language, along with other complex cognitive processes, depends on the concerted operation of multicomponent, large-scale neural systems. The anatomical components are often widely dispersed and each acts as a partial contributor to a com- plicated process rather than as a single purveyor. In this view, Wernicke's area, a part of which is a component of a language system, does not accom- plish anything as complicated as auditory comprehension, although its im- pairment leads to auditory comprehension defects (A. Damasio, 1992). Aphasia Aphasia is a disturbance of the complex process of comprehending and formulating verbal messages that results from newly acquired disease of the central nervous system (CNS). ACQUIRED APHASIA, THIRD EDITION 25 Copyright 1998 by Academic Press. All rights of reproduction in any form reserved.

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  • 2 Signs of Aphasia ANTONIO R. DAMASIO

    This chapter discusses the clinical presentation of the aphasias, the major types, and the principal signs. A discussion of the neuroanatomy and neu- rophysiology of language (and, by extension, a discussion of the phys- iopathology of the aphasias) is outside the scope of this text. However, the comments on the clinical evidence presented here reflect a particular theo- retical perspective on neuroanatomy, neurophysiology, and physiopath- ology, which has been documented elsewhere in detail (A. Damasio, 1989a, 1989b, 1989c; A. R. Damasio & Damasio, 1994; H. Damasio & Damasio, 1989).

    It is important to note that when I refer to the LOCALIZATION VALUE or CORRELATE of a given sign, I do not mean to say that the correlated brain lo- cus normally operates to produce whatever function a sign reports as miss- ing. In the perspective outlined in the earlier articles, language, along with other complex cognitive processes, depends on the concerted operation of multicomponent, large-scale neural systems. The anatomical components are often widely dispersed and each acts as a partial contributor to a com- plicated process rather than as a single purveyor. In this view, Wernicke's area, a part of which is a component of a language system, does not accom- plish anything as complicated as auditory comprehension, although its im- pairment leads to auditory comprehension defects (A. Damasio, 1992).

    Aphasia Aphasia is a disturbance of the complex process of comprehending and

    formulating verbal messages that results from newly acquired disease of the central nervous system (CNS).

    ACQUIRED APHASIA, THIRD EDITION 25

    Copyright 9 1998 by Academic Press. All rights of reproduction in any form reserved.

  • 26 Antonio R. Damasio

    The disease processes that cause aphasia are acquired (e.g., cerebral in- farction, tumor, contusion) rather than congenital (e.g., genetic or environ- ment-induced perinatal cerebral defect). The former befalls individuals previously capable of using language appropriately. The latter may pro- duce developmental language defects in individuals whose ability to use language will never attain a normal level.

    Although it is clear that all mental activity and communication stems from the activity of the CNS, reference to the CNS is important because aphasia is not the result of a peculiar utilization of language related to psy- chogenic or social deviations.

    Throughout the chapter I refer to VERBAL COMMUNICATION and LAN- GUACE almost interchangeably. Under the terms verbal and language I in- clude both auditory-based words and the visuomotor-based signs of sign languages. On the other hand, language and speech are not interchange- able. The latter should be reserved for the act of "speaking a verbal mes- sage" independently of the process of formulating the message itself. In this definition, I use VERBAL MESSAGES to call attention to the fact that apha- sia relates exclusively to a disturbance in the use of words and signs, as op- posed, for example, to the use of gestures, facial expressions, or body ex- pressions, which are also important components of social communication but are not language in the sense used here.

    Aphasia can affect comprehension of the language the patient either hears spoken or sees written, or both. It can also affect the comprehension of visuomotor signs from a sign language. Aphasia can affect the formula- tion of oral language production, writing, or both. In users of a sign lan- guage it affects the ability to sign in a linguistically correct manner.

    Aphasia often disturbs both reception and expression of language, in both visual (written) and auditory (spoken) modes. Yet, each of the sever- al fundamental types of aphasia compromises one of these modes pre- ponderantly. Indeed, in some instances (e.g., in PURE ALEXIA or in PURE WORD DEAFNESS), only one of these abilities suffers while all others remain unaffected. There is more about this particular question later in the chapter.

    The emphasis on COMPREHENDING and FORMULATING is especially per- tinent. Aphasics have trouble comprehending verbal messages, that is, de- ciphering their meaning as opposed to hearing or seeing those messages. Neither deafness (peripheral or central) nor blindness is the problem. A deaf or blind person cannot comprehend language in the modality of the perceptual impairment, but will comprehend the same verbal message normally when processed by an intact sensory channel, for example, tac- tile Braille reading in the blind. Aphasics also have trouble formulating verbal messages, for example, selecting the lexical and syntactical items necessary to convey meaning and deploying them in a relational frame-

  • 2 Signs of Aphasia 27

    work such that meaning is indeed imparted on the receiver of the message. Yet an impediment of phonation that prevents speech production has noth- ing to do with formulation of verbal messages (people can still write what they cannot say), nor does the loss of one's hands interfere with language formulation (people may still say it if they have formulated it, and they may even write with a pen held between the teeth or the toes).

    To characterize the nature of the disturbance, stating what aphasia is not becomes just as important as stating what it is. To begin with, aphasia is not a disturbance of articulation. Many patients suffer from speech distur- bances due to acquired disease of the basal ganglia, of the brain stem or cerebellum, or even of the cerebral cortex, and yet few of those patients will have aphasia. Although their speech sounds are poorly formed or are in- appropriately repeated, word selection and sentence structure are gram- matically correct, appropriate to the intentions of their author, and under- standable to the attentive listener. That is to say, such patients have a speech disturbance but it does not follow that they have a verbal language disturbance: Their language formulation is normal, their communication is linguistically correct, and thus they do not have aphasia.

    Patients with mutism, who can be entirely silent, are not necessarily aphasic, although on occasion their absence of speech does conceal an aphasia. Often these patients fail to indicate any desire to communicate by gesture, mimicry, or writing. Consequently, little is known about what they do or do not comprehend, or about what they may or may not want to say (or think, for that matter). However, when most mutism patients awake from these peculiar states of apparent indifference, they resume language communication and show no evidence of aphasia. When probed about their abnormal behavior, these patients clearly relate a strange experience of avolition and diminished richness of thought content, but not of any problem with the actual composition of verbal communication. Most such patients have disease in areas of the brain that are different from those that produce the aphasias, for example, in the supplementary motor area or in the cingulate gyrus as opposed to the region surrounding the Sylvian fis- sure. A few have acute psychotic states and no macroscopically detectable brain disease, although they may suffer from profound changes in neuro- transmitter systems innervating certain regions of the brain.

    Also not aphasic are patients with aphonia that may result from diseases of the larynx and pharynx. They are mute, in the narrow sense of the word, and are suffering from an impediment in their phonatory apparatus that prevents them from speaking. They should be able to comprehend lan- guage (and indicate so by nodding or pointing responses), and they should be able to turn their thoughts into language by writing, in addition to be- ing able to mouth words. The exception, other than for malingering, is a

  • 28 Antonio R. Damasio

    conversion reaction, the currently infrequent psychiatric diagnosis of HYS- TERICAL APHONIA .

    Finally, it should be noted that the language disorder experienced in al- tered states of awareness is not an aphasia. Any patient with a confusion- al state will produce disturbed language and fail to comprehend verbal communication. But such patients have a concomitant disorder of their thought processes that parallels the language disturbance. Unlike the pa- tient with aphasia who struggles to turn properly organized meanings into language and fails (or tries, without success, to turn the message heard into internal meaning), patients with confusional states communicate their dis- ordered thought processes verbally, with remarkable success. Confusion- al states are most commonly produced by metabolic disturbances or by substance intoxication, but they can also be the result of cerebral tumors (directly or indirectly affecting brain structures that sustain vigilance) or of trauma.

    A picture of a patient with aphasia should begin to emerge:

    1. An aphasic produces some speech, or even abundant speech, which does not conform to the grammatical rules of the language being used. The errors include omission of words, such as conjunctions or prepositions (functor words), erroneous choice of words (substitution of the intended word for another that may or may not be related in sound or meaning), and disturbances of the relationship among words in a sentence (e.g., as ex- pressed in word order). The rule that aphasic patients always produce some speech may not be true during the first hours or days of onset of dis- ease. But even during a phase of speechlessness, most aphasic patients at- tempt to communicate by gesture or facial expression.

    2. An aphasic often has difficulty in comprehending a purely verbal command (i.e., a verbal message given through auditory or visual means, without accompanying gestures, facial expressions, or meaningful emo- tional intonation). The errors of comprehension may range from an almost complete inability to understand any but the most elementary questions, to mild defects that surface when complex sentences are presented (e.g., sentences with double negatives or dependent clauses).

    3. An aphasic is aware of self and environment, and when medically ex- amined has an appropriate level of awareness. She or he is intent on com- municating thoughts regarding her or his own condition and surround- ings. Again, there may be exceptions, particularly in the first few hours after an acute brain lesion, when aphasic patients may appear inattentive and uninterested in communication. There may be patients, well into their chronic stages, in whom a depression will not permit an appropriate rela- tion with examiners and surroundings. In general, however, as far as can

  • 2 Signs of Aphasia 29

    be determined given that the view of the world available to an aphasic is impoverished by lack of intact verbal processing, it is not the view of a con- fused, or demented, or psychotic patient. Accordingly, the appearance of the aphasic patient is not that of an alienated individual. More often than not, beyond the barrier of handicapped communication, the examiner of an aphasic patient can empathize with the subject. The student of aphasia should develop a keen sensitivity to this important aspect of aphasia.

    S igns of Aphas ia

    Naming Disturbances and the Production of Paraphasias

    At the core of language formulation lies the ability to select from the ver- bal lexicon a word that conveys the meaning of a given thought. The se- lection process is often automatic although we may deliberately search for the precise lexical item, a process designated as WORD FINDING. When-word selection fails, the result is either the omission of the intended item or a substitution of an incorrect and unintended word. The latter is termed PARAPHASIA and probably is the central sign of aphasia. If an entire word is substituted, the paraphasia is called VERBAL or GLOBAL. If the incorrect- ly selected item belongs to the same semantic field (e.g., chair for table), it is termed a SEMANTIC paraphasia. Too many verbal paraphasias appearing in sentence after sentence give rise to JARGON SPEECH.

    Paraphasias can be entirely novel words which do not exist in the lexi- con of a given language (NEOLOGISTIC paraphasias). The mechanism for the formulation of the new word may be a succession of phoneme substi- tutions. When a single phoneme is substituted or added (e.g., table becomes trable or fable), the sign is known as a PHONEMIC or LITERAL paraphasia. Too many phonemic paraphasias produce an unintelligible neologism (and too many neologistic paraphasias become NEOLOGISTIC JARGON).

    Paraphasias can appear in spontaneous speech or in a dialogue, on rep- etition of spoken sentences or on reading aloud, in naming tasks, and in writing; but they are generally absent in automatic speech (emotional ex- clamations, series of numbers, calendar sequences).

    One of the most exciting new developments in aphasia research comes from the identification of patterns of word-finding defects related to var- ied domains of conceptual knowledge. Patients with naming defects are not impaired for all words that decode all categories of knowledge. On the contrary, the defects are more pronounced in some categories than in oth-

  • 30 Antonio R. Damasio

    ers, and their seeming selectivity reveals some of the underpinnings of lex- ical organization (see A. Damasio, 1990; A. Damasio & Damasio, 1992; A. R. Damasio, Damasio, Tranel, & Brandt, 1990; A. R. Damasio & Tranel, 1993; H. Damasio, Grabowski, Tranel, Hichwa, & Damasio, 1996).

    Disturbance of Fluency

    Although the general characteristics of speech in aphasic patients are not always easily classifiable, they often fall into one of two categories: FLU- ENT or NONFLUENT. The designations can have slightly different meanings for different authors, but for most aphasiologists, fluent speech approxi- mates normal speech in terms of the rate of word production, the length of each sentence, the melodic contour of the sentences, and the overall ease of the speaking act. In practical terms, it is usually measured by the longest continuous string of words that the patient produces in conversation. Flu- ent aphasic speech may be actually more abundant than normal speech. Nonfluent speech is the opposite: The rate is low, sentence length is short, the melodic contour is lost, the production is effortful, and there may be more pauses than actual words in a given time unit.

    Judging the quality of articulation is a separate matter from judging flu- ency. Most patients with fluent speech have normal articulation, although some may have minor difficulties. Many patients with nonfluent speech also have perfect articulation, although some do not. As noted, the ability to articulate speech and the ability to formulate language are different. Even patients with severe nonfluent speech are able to produce perfectly articulated automatized verbal sequences (as in counting or in emotional exclamations).

    A measure of fluency may help with clinical classification and provide a rough indication for the localization of lesion. Most patients with fluent aphasias have lesions located in the posterior aspect of the perisylvian re- gion. Most patients with nonfluent aphasias have lesions located in the an- terior aspect of the perisylvian region (Benson, 1967).

    Disturbances of Repetition

    A failure to repeat words or sentences is another hallmark of aphasia. The ability to repeat may be entirely lost, or may be marred by phonemic paraphasias or omissions of sounds and words. Repetition is impaired in most aphasias, and actually dominates the clinical presentation of con- duction aphasia largely because other pronounced defects are lacking.

    The impairment of repetition has major localization value. Its presence

  • 2 Signs of Aphasia 31

    places the lesion firmly in the perisylvian region of the dominant hemi- sphere. Repetition defects are notably absent in the transcortical aphasias and in the so-called anomic aphasias, whose correlated lesion is located outside the perisylvian ring. Patients with transcortical aphasias may ac- tually repeat only too well, echoing the examiner's words immediately af- ter they are pronounced, often with little or no comprehension of what they are parroting. Such a defect is called ECHOLALIA.

    Disturbances of Auditory Comprehension

    Auditory comprehension can be impaired to variable degrees. Some pa- tients are able to participate in a colloquial conversation, giving appropri- ate verbal replies or indicating that they understand the content of the mes- sages by nodding, pointing responses, facial expression, or gestures. Yet, confronted with laboratory tests, they may fail many items, especially when the question aims at specifics rather than generalities, and when the linguistic structure is complex rather than transparent. Other patients may be quite impaired even in a simple conversation, let alone in the laborato- ry tests.

    Disturbances of Grammatical Processing

    AGRAMMATISM is another important sign of aphasia. It refers to diffi- culty with generating the syntactical frames into which lexical selections must be placed, and to a defective utilization of grammatical morphemes. Grammatical morphemes include functor words (free grammatical mor- phemes) or the inflectional affixes that mark tense, aspect, or person when placed at a verb ending (bound grammatical morphemes). It used to be thought that only patients of the Broca type were agrammatic, but it is now clear that patients with other aphasia types, namely the commonly en- countered Wernicke's aphasia, can be agrammatic too. Agrammatism is discussed at length elsewhere in this volume.

    Disturbances of Reading and Writing

    Reading comprehension can be disturbed in much the same way as au- ditory comprehension, although the two defects do not necessarily go to- gether. For instance, patients with auditory comprehension defects usual- ly have some reading impairment, but the proportion of those with both defects is small. On the other hand, impairment of reading can appear in pure form without impairment of auditory comprehension or writing. In

  • 32 Antonio R. Damasio

    most cases of aphasia, however, reading, writing, and auditory compre- hension are impaired together, although rarely to the same degree.

    Apraxia

    Many aphasic patients also present with apraxia, forms of which, from a practical and clinical standpoint, can be considered yet another sign of aphasia. APRAXIA may be defined as a disorder of the execution of learned movement that cannot be accounted for by weakness, incoordination, sen- sory loss, or impaired comprehension or attention to commands. From a theoretical point of view, however, it should be clear that apraxia can ap- pear in isolation, without aphasia, and that its many varieties and mecha- nisms justify a separate entity status. The presence of apraxia should be in- vestigated in all aphasic patients, as it may interfere with the performance of acts requested through verbal command. Students of aphasia should be aware of the fact that patients do not "complain" of apraxia and that, ex- cept for the extreme forms of ideational apraxia, the phenomenon is nei- ther immediately disruptive to the patient's life nor evident to the exam- iner. The reader is referred to Geschwind (1975; A. Damasio & Geschwind, 1984; Geschwind & Galaburda, 1985) for a comprehensive view of the phe- nomenon.

    C lass i f icat ions of Aphas ia

    Classifications are a necessary evil. Attempting to review the classifica- tion systems of aphasia is probably foolhardy. The variety of criteria used over the past 100 years may disorient the reader at first. The diversity of the nomenclature is exasperating. The seeming conflict between systems that include as many as eight different varieties of aphasia and those that limit themselves to two or three is a source of puzzlement. Yet, the student of aphasia should realize that the diversity reflects the evolution of the sci- ence of the aphasias and the conflicts are more apparent than real--the sys- tems derive from different points of view about the phenomena of apha- sia. For instance, Weisenburg and McBride's (1935) classic designations of EXPRESSIVE, RECEPTIVE, and MIXED aphasia reflect a clinical vantage point. The terms in Luria's (1966) nomenclature--for example, EFFERENT and AF- FERENT MOTOR, or DYNAMIC--reflect a physiological approach. On the oth- er hand, Jakobson's (1964) description of CONTIGUITY (or combination) and SIMILARITY (or selection) defects draws on a psycholinguistic point of view. The systems do not conflict but rather complement each other. Be that as

  • 2 Signs of Aphasia 33

    it may, a modern researcher or clinician should have a working know- ledge of the different classification systems, from Wernicke's (1874) to Geschwind's (1965). This should be complemented with a conversance in one of the modern classification systems: the proper definition of each of the categories, their anatomical and physiological significance, and their prognostic implications.

    The system generally associated with the Boston school of aphasia is perhaps the most useful. It can be used in conjunction with most forms of laboratory and bedside assessment and does not necessarily require the use of the Boston Diagnostic Aphasia Examination (BDAE). The Boston classification comprises all of the frequently encountered aphasias for which there is an established and accepted anatomical correlation. The nomenclature utilizes a combination of eponyms, clinically descriptive terms, and physiologically based terms and is not especially mysterious (see Goodglass & Kaplan, 1972).

    The following paragraphs contain descriptions of the aphasias most fre- quently encountered in clinical practice. I refer to them as "types" because each description corresponds to the averaged mental representation that an experienced observer forms, out of many comparable exemplars, bring- ing together signs that are salient over different epochs after the onset of aphasia. The reasons why signs cluster themselves in fairly distinct pat- terns are largely biological. Damage to certain neural units tends to pro- duce, fairly consistently, a given sign of dysfunction. By the same token, the reason why the precise cluster of signs varies from individual to indi- vidual--a sign may be missing from the usual combination or some sign may be more or less pronounced than usualmis largely neuroanatomical. The precise lesion placement varies from individual to individual because of individual variations of normal neural and vascular anatomy, combined with variations of neuropathologic dynamics. Furthermore, there are indi- vidual variations in the assignment of components of normal psychologi- cal function to separate anatomical components of neural networks.

    In spite of all of these sources of variance, the astonishing fact remains the consistency with which certain signs do cluster, in case after case. Con- sequently, the aphasia typology discussed here will continue to be useful to clinicians in sorting diagnostic and management issues and in commu- nicating effectively among themselves. On the other hand, it is clear that aphasia types, or even finer-etched aphasia syndromes, are generally not helpful in establishing groups of patients for research, and are of little use as a basis for neurophysiological reasoning. Research purposes are best served by making individual signs the variables with which neuroana- tomical information or the result of cognitive experiments are connected.

  • 34 Antonio R. Damasio

    Major Aphas ia Types

    Wernicke's Aphasia

    Wernicke's aphasia is perhaps the least controversial of the aphasia types. Speech is fluent and well articulated, with frequent paraphasias (both verbal and literal). Syntactic structure appears less disturbed than in Broca's aphasia, but it is reasonable to say that both Wernicke's and Broca's aphasics exhibit some form of agrammatism. Aural comprehension is de- fective. Repetition of words and sentences is also defective. In general, both reading and writing are disturbed.

    Most patients may have no other evidence of neurological disease, as right hemiparesis is infrequent or transient; right visual field defects are not the rule. Thus, the diagnosis rests almost solely on the language signs and accuracy of the diagnosis is mandatory: For the unskilled examiner, a patient with acute Wernicke's aphasia may sound "confused," with the consequence that a psychiatric rather than neurological diagnostic ap- proach may be taken. Even assuming that the mistake is eventually cor- rected, the delay can be disastrous.

    Patients with Wernicke's aphasia are less easily frustrated than those with Broca's aphasia. Yet, a tendency for paranoid ideation is more evident in Wernicke patients than in Broca patients. It should be recalled that these are among the few neurological patients who can develop a major para- noid syndrome and become homicidal.

    This complex syndrome, which combines both output and input dis- turbances, is also known as RECEPTIVE aphasia, from Weisenburg and McBride's classification (1935), and as SENSORY aphasia, as Wernicke him- self called it (1874), with appreciable modesty but little physiological sense. Kleist (1934) aptly called it WORD DEAFNESS, but the term is rarely used; whereas Brain (1961) named it PURE WORD DEAFNESS, an inaccurate desig- nation, as patients with Wernicke's aphasia are indeed word deaf but clear- ly not in pure form. (Patients with pure word deafness do exist, however; they are unable to understand speech and to repeat words but speak flu- ently and without paraphasias). Head (1926) called this type of aphasia SYN- TACTIC aphasia, a rather useless designation.

    Broca's Aphasia

    The existence of Broca's aphasia is currently well established. Yet some of the major controversies in the history of aphasia have revolved around its nature and pathological correlation. The first patient described by Bro-

  • 2 Signs of Aphasia 35

    ca in 1861 did not have what came to be known as Broca's aphasia, and it is clear that the degree of involvement of Broca's area and of the sur- rounding frontal operculum produce considerably different degrees of aphasia (Mohr et al., 1978). What currently is called Broca's aphasia can be defined as the opposite of Wernicke's aphasia. The speech is nonfluent. There are few words, short sentences, and many intervening pauses. What words emerge are produced with labor and often with distorted sounds. The melodic contour is flat. Syntactical structure is more disturbed than in Wernicke's. The general appearance of speech is telegraphic, due both to the selective deletion of many functor words and to disturbances of canon- ical word order. On the other hand, aural comprehension is relatively in- tact in colloquial conversation, although formal testing often discloses a defective performance. Repetition of words and sentences is impaired. Broca's aphasia should be distinguished from APHEMIA, an articulatory disorder caused by generally small lesions underneath the motor cortices or in the vicinity of the basal ganglia (Schiff, Alexander, Naeser, & Gala- burda, 1983).

    Unlike patients with Wernicke's aphasia, the patient with Broca's apha- sia invariably presents with a right-sided motor defect (often a complete hemiparesis more marked in the upper extremity and face). As a conse- quence, patients with Broca's aphasia are less vulnerable to misdiagnosis. Their presentation is clearly neurological. On the other hand, they are of- ten depressed and may respond to testing failures with "catastrophic" re- actions (sudden weeping and refusal to proceed with the examination) more frequently than do Wernicke's aphasics.

    Broca's aphasia has also been known as EXPRESSIVE (Weisenburg & McBride, 1935) and MOTOR (Goldstein, 1948; Wernicke, 1874) aphasia. For a time it was refused the status of aphasia and instead was called ANARTHRIA (Marie, 1906) and, later, DYSARTHRIA (Bay, 1964). Head (1926) called it VERBAL aphasia.

    Conduction Aphasia

    The speech of conduction aphasics is fluent although usually less abun- dant than that of Wernicke's. Commonly there are minor defects in aural comprehension, although understanding of colloquial conversation is in- tact. The impairment in repetition of words and sentences dominates the picture. The defect takes many forms. Most commonly, patients repeat words with phonemic paraphasias, but often they will omit or substitute words, and they may fail to repeat anything at all if function words rather than nouns are requested. Comprehension of the defectively repeated sen-

  • 36 Antonio R. Damasio

    tences is good. Similarly, patients comprehend the sentences that they read aloud with numerous paraphasias.

    Conduction aphasics often have some accompanying motor signs (pare- sis of the right side of the face and of the right upper extremity), but re- covery is good. The syndrome has been known as CENTRAL aphasia, Gold- stein's (1948) curious designation, and as AFFERENT MOTOR APHASIA, Luria's term. Luria attempted to break down the condition, giving it a mo- tor component (AFFERENT MOTOR) and an auditory one (ACOUSTIC AM- NESIC). Kertesz (1979) proposed a comparable distinction (EFFERENT CON- DUCTION and AFFERENT CONDUCTION).

    Transcortical Sensory Aphasia

    Patients with transcortical sensory aphasia (TSA) have fluent and para- phasic speech (global paraphasias predominate over phonemic) and a se- vere impairment in aural comprehension. Yet their repetition is intact (oc- casionally echolalic), setting them clearly apart from Wernicke's aphasics. The distinction is important because the localization of the lesion is differ- ent (see Chapter 3 on localization). This underscores the need to test repe- tition in every aphasic patient.

    TRANSCORTICAL was the original designation of Goldstein, and it has held up well through the years, both for TSA and for transcortical motor aphasia, some cases of which Luria preferred to call DYNAMIC aphasia (Luria & Tsevtkova, 1968).

    Transcortical Motor Aphasia

    Patients with transcortical motor aphasia (TMA) have intact repetition, as do patients with TSA, and can have echolalia as well. But the speech is nonfluent and troubled by phonemic and global paraphasias, persevera- tion, and loss of connective words. Auditory comprehension is also im- paired when tested formally, although patients can often carry on a simple conversation at bedside.

    Patients with TMA should be distinguished from those with mutism on several counts. First, patients with TMA are inclined to communicate and do so within their verbal imitations. Patients with mutism do not and are as impoverished in nonverbal communication as in verbal communica- tion. Secondly, the speech of TMA is clearly aphasic: there are unquestion- able phonetic, lexical, and syntactical errors, whereas patients with mutism either produce no speech at all or utter a few short but linguistically cor- rect sentences. Again, the distinction is important because the localization of the lesion is different.

  • 2 Signs of Aphasia 37

    Global Aphasia

    As the name implies, global aphasics present with an almost complete loss of ability to comprehend or formulate verbal communication. Propo- sitional speech may be reduced to a few words, and the remainder of ver- bal communication consists of emotional exclamations and serial utter- ances. Auditory comprehension is often reduced to a variable number of nouns and verbs, and the comprehension of functor words or of syntacti- cally organized sentences is virtually negligible.

    Hemiplegia accompanies most global aphasias but not all. In global aphasia without hemiplegia the defects are less pronounced and the re- covery is better (Tranel, Biller, Damasio, Adams, & Cornell, 1987).

    Anomic Aphasia

    It is important to distinguish pure anomic aphasia from anomia as a sign of aphasia, as the latter is present in practically all aphasias. Anomic apha- sia is characterized by a pervasive impairment of word finding, which con- trasts with intact repetition and speech that is fluent, well articulated, and grammatically correct. The neuroanatomical basis of anomic aphasia is be- ing elucidated. These patients have damage to language areas outside the perisylvian circle, largely within anterior and inferior left temporal regions (A. R. Damasio & Damasio, 1992; H. Damasio & Damasio, 1989; H. Dama- sio et al., 1996; Graff-Radford et al., 1990; Tranel, Damasio, & Damasio, 1988). Different entities and conceptual-lexical categories are impaired or spared in a dissociated manner (e.g., patients are better at naming entities that are manufactured than natural, and subgroupings within those broad classes reveal further dissociations). Such disparities, along with the theo- retical formulations necessary to account for them, provide an important source of evidence for studies of lexical representation. The terms AMNESIC (amnestic) aphasia, NOMINAL aphasia and VERBAL AMNESIA are synony- mous.

    The signs of anomic aphasia can also be found in the so-called progres- sive aphasias. As the name indicates, progressive aphasias are conditions in which the language impairment appears gradually rather than acutely. Rather than being caused by a stroke or a head injury, which are the most frequent causes of standard acute aphasia, the progressive aphasias are caused by degenerative diseases. Examples are Pick's disease, spongiform encephalopathies, and even Alzheimer's disease.

    In the most typical presentation, patients develop gradual difficulties with word retrieval. The grammatical class most frequently involved is nouns, and that frequent defect correlates well with a pronounced neu-

  • 38 Antonio R. Damasio

    ropathological involvement of the left temporal region. In some instances the predominant defect may involve verbs, and the presentation may even begin with an impairment in the retrieval of word-forms for verbs rather than for nouns. In those cases the neuropathological compromise tends to be more pronounced in the left premotor and premotor regions than in the temporal lobe. In general, as the condition progresses, both grammatical classes come are affected.

    It should be noted that patients with progressive aphasia may develop cognitive impairments outside the language realm. In those circumstances the aphasia becomes part of a dementia syndrome.

    Alexia with Agraphia

    Alexia with agraphia is a true rarity. More often than not, patients with both alexia and agraphia have signs of Wernicke's aphasia or transcortical sensory aphasia. In the absence of aphasia, they generally have signs of parietal lobe dysfunction. The diagnosis of alexia with agraphia only ap- plies when the disturbances of reading and writing predominate over the aphasic or parietal symptomatology. The fact that this syndrome can be as- sociated with impaired as well as intact repetition, and with a greater or smaller extent of accompanying signs, suggests that a large segment of parietal and temporal lobe structures, cortical and subcortical, is engaged in the complex processes of reading and writing. The anatomical signifi- cance of this is considerably smaller than that of alexia without agraphia (pure alexia).

    Alexia without Agraphia (Pure Alexia)

    As the designation implies, patients presenting alexia with agraphia be- come unable to read while they continue to be able to write, spontaneous- ly or to dictation. Many such patients can also copy writing, although they do so with difficulty. Speech, auditory comprehension, and repetition are intact. Oral spelling of words (or its converse, the construction of words spelled orally) is normal. Reading in the tactile mode is also normal. What- ever visual reading the patient can do is of single letters. This often allows the patient to read aloud the letters of a word, one by one, and then recon- stitute the word from the spelled out components.

    Although neither writing nor oral language impairments are present, most patients have some form of accompanying impairment of visual function (see A. R. Damasio & Damasio, 1983, for review). It can be a right homonymous hemianopia (the field of vision to the right of the vertical me- dian is blind) or a right hemiachromatopsia (loss of color perception with-

  • 2 Signs of Aphasia 39

    out true blindness in the right hemifield). Most patients also have color anomia, a disturbance of naming colors with otherwise normal color per- ception. Some present with optic ataxia, a disturbance in the visual guid- ance of hand movements.

    First described by Dejerine (1892), the syndrome was long forgotten and even denied, but it was revived by Geschwind (1965), who used it as a cor- nerstone for his theory of disconnection syndromes.

    Pure Word Deafness

    Patients with pure word deafness have a profound loss of auditory com- prehension and a complete impairment of repetition. Yet they produce nor- mal fluent speech, mostly without paraphasias. It could be argued that pure word deafness, like pure alexia, is not a true aphasia, because lan- guage formulation itself is not affected. From a physiopathological stand- point, both conditions reflect the inability of verbal information to reach structures capable of processing it into meaning. Inner language opera- tions as well as exteriorization of well-formulated language remain intact. There are reasons, however, why the two conditions should be discussed along with the aphasias. First, they resemble aphasias from the stand- point of the communication impairment they produce. Second, the anatomical and physiological knowledge derived from studying these two "input" disorders has contributed importantly to the understanding of the aphasias.

    "'Atypical" Aphasias

    A considerable number of cases of aphasia fail to conform to any of the types described here. This happens for a variety of neurobiological, neu- ropsychological, and cultural reasons. Perhaps the most frequently en- countered atypical exemplars are ascribed to a so-called nonstandard cere- bral dominance disposition (right cerebral dominance for language in a left-hander or right-hander, or "ambidominance" in a left-hander). How- ever, another important source of "atypical" aphasias is damage in a non- cortical sector of language networks. The lesion can be located in the deep nuclear gray masses (basal ganglia or thalamus) and may involve white matter in the vicinity (e.g., the anterior limb of the internal capsule). As an example, aphasia can arise after nonhemorrhagic infarction, which dam- ages the left head of the caudate and the anterior limb of the internal cap- sule (A. R. Damasio, Damasio, Rizzo, Varney, & Gersh, 1982; H. Damasio, Eslinger, & Adams, 1984; Naeser et al., 1982). Damage to the left thalamus from either hemorrhagic (Alexander & Lo Verme, 1980; Hier & Mohr, 1975)

  • 40 Antonio R. Damasio

    or nonhemorrhagic infarction (Graff-Radford, Damasio, Yamada, Eslinger, & Damasio, 1985) also causes aphasia.

    Acknowledgment This work was supported by NINCDS Grant PO1 NS19632.

    References

    Alexander, M. P., & Lo Verme, S. R. (1980). Aphasia after left hemispheric intercerebral hem- orrhage. Neurology, 30, 1193-1202.

    Bay, E. (1964). Principles of classification and their influence on our concepts of aphasia. In A. V. S. De Reuck & M. O'Connor (Eds.), Disorders of language. London: Churchill.

    Benson, D. F. (1967). Fluency in aphasia: Correlation with radioactive scan localization. Cor- tex, 3, 373-394.

    Brain, W. R. (1961). Speech disorders. London: Butterworth. Broca, P. (1861). Remarques sur le si6ge de la facult6 du langage articule, suivies d'une ob-

    servation d'aph6mie (perte de la parole). Bulletin de la Societe d'Anatomie (Paris), 36, 330 -357.

    Damasio, A. R. (1989a). Time-locked multiregional retroactivation: A systems level model for some neural substrates of recall and cognition. Cognition, 33, 25-62.

    Damasio, A. R. (1989b). The brain binds entities and events by multiregional activation from convergence zones. Neural Computation, 1, 123-132.

    Damasio, A. R. (1989c). Concepts in the brain. Mind and Language, 4, 24-28. Damasio, A. R. (1990). Category-related recognition defects as a clue to the neural substrates

    of knowledge. Trends in Neuroscience, 13, 95-98. Damasio, A. R. (1992). Aphasia. New England Journal of Medicine, 326, 531-539. Damasio, A. R., & Damasio, H. (1983). The anatomic basis of pure alexia. Neurology, 33, 1573

    -1583. Damasio, A. R., & Damasio, H. (1992). Brain and language. Scientific American, 267, 89-95. Damasio, A. R., and Damasio, H. (1994). Cortical systems for retrieval of concrete knowledge:

    the convergence zone framework. In C. Koch (Ed.), Large-scale neuronal theories of the brain (pp. 61-74). Cambridge, MA: MIT Press.

    Damasio, A. R., Damasio, H., Rizzo, M., Varney, N., & Gersh, F. (1982). Aphasia with non- hemorrhagic lesions in the basal ganglia and internal capsule. Archives of Neurology (Chica- go), 39, 15-20.

    Damasio, A. R., Damasio, H., Tranel, D., & Brandt, J. P. (1990). Neural regionalization of knowledge access: Preliminary evidence. Cold Spring Harbor Symposia on Quantitative Bi- ology, 55, 1039-1047.

    Damasio, A. R., & Geschwind, N. (1984). The neural basis of language. Annual Review of Neu- roscience, 7, 127-147.

    Damasio, A. R., & Tranel, D. (1993). Nouns and verbs are retrieved with differently distrib- uted neural systems. Proceedings of the National Academy of Sciences of the U.S.A. 90, 4957- 4960.

    Damasio, H., & Damasio, A. R. (1989). Lesion analysis in neuropsychology. New York: Oxford University Press.

  • 2 Signs of Aphasia 41

    Damasio, H., Eslinger, P., & Adams, H. P. (1984). Aphasia following basal ganglia lesions: New evidence. Seminars in Neurology, 4, 151-161.

    Damasio, H., Grabowski, T. J., Tranel, D., Hichwa, R., & Damasio, A. (1996). A neural basis for lexical retrieval. Nature (London), 380, 499-505.

    Dejerine, J. (1892). Des diff6rentes vari6t6s de c6cit6 verbale. Memoires de la Societe de Biologie, Series 9, 4, 61-90.

    Geschwind, N. (1965). Disconnexion syndromes in animals and man. Brain, 88, 237-294, 585 -644.

    Geschwind, N. (1975). The apraxias: Neurological mechanisms of disorders of learned move- ment. American Scientist, 63, 188-195.

    Geschwind, N., & Galaburda, A. M. (1985). Cerebral lateralization: Biological mechanisms, association, and pathology. Archives of Neurology (Chicago), 428-426.

    Goldstein, K. (1948). Language and language disturbances. New York: Grune & Stratton. Goodglass, H., & Kaplan, E. (1972). Assessment of aphasia and related disorders. Philadelphia:

    Lea & Febiger. Graff-Radford, N. G., Damasio, A. R., Hyman, B. T., Hart, M., Tranel, D., Damasio, H., Van

    Hoesen, G. W., & Rezai, K. (1990). Progressive aphasia in a patient with Pick's disease: A neuropsychological, radiological and anatomical study. Neurology, 40, 620-626.

    Graff-Radford, N., Damasio, H., Yamada, T., Eslinger, P., & Damasio, A. R. (1985). Nonhem- orrhagic thalamic infarction: Clinical, neurophysiological and electrophysiological find- ings in four anatomical groups defined by CT. Brain, 108, 485-516.

    Head, H. (1926). Aphasia and kindred disorders of speech. Cambridge, England: Cambridge Uni- versity Press.

    Hier, D. B., & Mohr, J. P. (1977). Incongruous oral and written naming. Evidence for a subdi- vision of the syndrome of Wernicke's aphasia. Brain and Language, 4, 115-126.

    Jakobson, R. (1964). Towards a linguistic typology of aphasic impairments. In A. V. S. De Reuck & M. O'Connor (Eds.), Disorders of language. London: Churchill.

    Kertesz, A. (1979). Aphasia and associated disorders. New York: Grune & Stratton. Kleist, K. (1934). Gehirnpathologie. Leipzig: Barth. Luria, A. R. (1966). Higher cortical functions in man. New York: Basic Books. Luria, A. R., & Tsevtkova, L. (1968). The mechanisms of dynamic aphasia. Foundations of Lan-

    guage, 4, 296-307. Marie, P. (1906). Revision de la question de l'aphasie: La troisi6me circonvolution frontale

    gauche ne joue aucun role special dans la fonction du langage. Semaine Medicale, 21, 241-247.

    Mohr, J. P., Pessin, M. S., Finkelstein, S., Funkenstein, H. H., Duncan, G. W., & Davis, K. R. (1978). Broca's aphasia: Pathologic and clinical. Neurology, 28, 311-324.

    Naeser, M. A., Alexander, M. P., Helm-Estabrooks, N., Levine, H. L., Laughlin, S. A., & Geschwind, N. (1982). Aphasia with predominantly subcortical lesion sites. Archives of Neurology (Chicago), 39, 2-14.

    Schiff, H. G., Alexander, M. P., Naeser, M. A., & Galaburda, A. M. (1983). Aphemia: Clinical- anatomic correlations. Archives of Neurology (Chicago), 40, 720-727.

    Tranel, D., Biller, J., Damasio, H., Adams, H. P., & Cornell, S. (1987). Global aphasia without hemiparesis. Archives of Neurology (Chicago), 44, 304-308.

    Tranel, D., Damasio, H., & Damasio, A. R. (1988). Dissociated verbal and nonverbal retrieval and learning following left anterotemporal damage. Neurology, 38, 322.

    Weisenburg, T., & McBride, K. (1935). Aphasia. New York: Commonwealth Fund. Wernicke, C. (1874). Der aphasische symptomencomplex. Breslau: Cohn & Weigert.