Aphasia and Aphasic Syndromes

Symptoms and Differential Diagnosis of Disordered Language

Muteness , a total loss of speech, may represent severe aphasia (see the section Aphemia, a rare syndrome, later in this chapter). Muteness can also be a sign of dysarthria; frontal lobe dysfunction with akinetic mut ism; severe extrapyramidal system dysfunction, as in Parkinson disease; non-neurological disorders of the larynx and pharynx; or even psychogenic syndromes, such as catatonia. Caution must therefore be taken in diagnosing the mute patient as aphasic. A good rule of thumb is that if the patient can write or type and the language form and content are normal, the disorder is probably not aphasic in origin. If the patient cannot speak or write but makes apparent effort to vocalize, and if there is also evidence of deficient comprehension, aphasic muteness is likely. Associated signs of a left hemisphere injury, such as right hemiparesis, also aid in diagnosis. Finally, if the patient gradually begins to make sounds containing paraphasic errors, aphasia can be identified with confidence.

Halting and effortful speech is a symptom of aphasia, but also of motor speech disorders, such as dysarthria or stuttering, and it may be a manifestation of a psychogenic disorder (see under Differential Diagnosis of Causes of Aphasia, later in this chapter; ). A second rule of thumb is that if one can transcribe the utterances of an effortful speaker into normal language, the patient is not aphasic. Effortful speech occurs in many aphasia syndromes for varying reasons, including difficulty in speech initiation, imprecise articulation of phonemes, deficient syntax, or word-finding difficulty.

Anomia , or inability to produce a specific name, is generally a reliable indicator of language disorder, although it may also reflect memory loss. Anomia is manifest in aphasic speech by word-finding pauses and circumlocutions or use of a phrase where a single word would suffice.

Paraphasic speech refers to the presence of errors in the patient’s speech output. Paraphasic errors are divided into literal or phonemic errors, involving substitution of an incorrect sound (e.g., shoon for spoon), and verbal or semantic errors, involving substitution of an incorrect word (e.g., fork for spoon). A related language symptom is perseveration , the inappropriate repetition of a previous response. Occasionally, aphasic utterances involve nonexistent word forms called neologisms . A pattern of paraphasic errors and neologisms that so contaminate speech that the meaning cannot be discerned is called jargon .

Another cardinal symptom of aphasia is the failure to comprehend the speech of others. Most aphasic patients also have difficulty with comprehension and production of written language (reading and writing).

Fluent, paraphasic speech usually makes an aphasic disorder obvious. The chief differential diagnosis here involves aphasia, psychosis, acute encephalopathy or delirium, and dementia. Aphasic patients are usually not confused or inappropriate in behavior; they do not appear agitated or misuse objects, with occasional exceptions in acute syndromes of Wernicke or global aphasia. By contrast, most psychotic patients speak in an easily understood, grammatically appropriate manner, but their behavior and speech content are abnormal. Only rarely do schizophrenics speak in “clang association” or “word salad” speech. Sudden onset of fluent, paraphasic speech in a middle-aged or elderly patient should always be suspected of representing a left hemisphere lesion with aphasia.

Patients with acute encephalopathy or delirium may manifest paraphasic speech and “higher” language disorders, such as inability to write, but the grammatical expression of language is less disturbed than is its content. These language symptoms, moreover, are less prominent than accompanying behavioral disturbances, such as agitation, hallucinations, drowsiness, or excitement, and cognitive difficulties, such as disorientation, memory loss, and delusional thinking.

Chronic encephalopathies, or dementias, pose a more difficult diagnostic problem because involvement of the language cortex produces readily detectable language deficits, especially involving naming, reading, and writing. These language disorders (see Language in Dementing Diseases, later in this chapter) differ from aphasia secondary to focal lesions mainly by the involvement of other cognitive functions, such as memory and visuospatial processes.

Bedside Language Examination

The first part of any bedside examination of language is the observation of the patient’s speech and comprehension during the clinical interview. A wealth of information about language function can be obtained if the examiner pays deliberate attention to the patient’s speech patterns and responses to questions. In particular, minor word-finding difficulty, occasional paraphasic errors, and higher-level deficits in discourse planning and in the pragmatics of communication, such as turn-taking in conversation and the use of humor and irony, can be detected principally during the informal interview.

D. Frank Benson and Norman Geschwind popularized a bedside language examination of six parts, updated by ( Box 13.1 ). This examination provides useful localizing information about brain dysfunction and is well worth the few minutes it takes.

The first part of the examination is an analysis of spontaneous speech. A speech sample may be elicited by asking the patient to describe the weather or the reason for coming to the doctor. If speech is sparse or absent, recitation of lists, such as counting or listing days of the week, may be helpful. The most important variable in spontaneous speech is fluency: fluent speech flows rapidly and effortlessly; nonfluent speech is uttered in single words or short phrases, with frequent pauses and hesitations. Attention should first be paid to such elementary characteristics as initiation difficulty, articulation, phonation or voice volume, rate of speech, prosody or melodic intonation of speech, and phrase length. Second, the content of speech utterances should be analyzed in terms of the presence of word-finding pauses, circumlocutions, and errors such as literal and verbal paraphasias and neologisms.

Naming, the second part of the bedside examination, is tested by asking the patient to name objects, object parts, pictures, colors, or body parts. A few items from each category should be tested because anomia can be specific to word classes. Proper names of persons are often affected severely. The examiner should ask questions to be sure that the patient recognizes the items or people that he or she cannot name.

Auditory comprehension is tested first by asking the patient to follow a series of commands of one, two, and three steps. An example of a one-step command is “stick out your tongue”; a two-step command is “hold up your left thumb and close your eyes.” Successful following of commands ensures adequate comprehension, at least at this simple level, but failure to follow commands does not automatically establish a loss of comprehension. The patient must hear the command, understand the language the examiner speaks, and possess the motor ability to execute it, including the absence of apraxia. Apraxia (see Chapter 11 for full discussion) is defined operationally as the inability to carry out a motor command despite normal comprehension and normal ability to carry out the motor act in another context, such as to imitation or with use of a real object. Because apraxia is difficult to exclude with confidence, it is advisable to test comprehension by tasks that do not require a motor act, such as yes–no questions, or by commands that require only a pointing response. The responses to nonsense questions (e.g., “Do you vomit every day?”) quickly establish whether the patient comprehends. Nonsense questions often produce surprising results, given the tendency of some aphasics to cover up comprehension difficulty with social chatter.

Repetition of words and phrases should be deliberately tested. Dysarthric patients have difficulty with rapid and variable sequences of consonants, such as “Methodist Episcopal,” whereas people with aphasia have particular difficulty with grammatically complex sentences. The phrase “no ifs, ands, or buts” is especially challenging for individuals with aphasia. Often, they can repeat familiar or “high-probability” phrases much better than unfamiliar ones.

Reading should be tested both aloud and for comprehension. The examiner should carry a few printed commands to facilitate a rapid comparison of auditory with reading comprehension. Of course, the examiner must have some idea of the patient’s premorbid reading ability.

Writing, the element of the bedside examination most often omitted, not only provides a further sample of expressive language but also allows an analysis of spelling, which is not possible with spoken language. A writing specimen may be the most sensitive indicator of mild aphasia, and it provides a permanent record for future comparison. Spontaneous writing, such as a sentence describing why the patient has come for examination, is especially sensitive for the detection of language difficulty. When spontaneous writing fails, writing to dictation and copying should be tested as well.

Finally, the neurologist combines the results of the bedside language examination with those of the rest of the mental status examination and of the neurological examination in general. These “associated signs” help to classify the type of aphasia and to localize the responsible brain lesion.

Differential Diagnosis of Aphasic Syndromes

Broca Aphasia

In 1861, the French physician Paul Broca described a nonfluent speech disorder in two patients, one of whom could say only “tan..tan”. He proposed the term aphemia, but aphasia was adopted. In Broca aphasia, the speech pattern is nonfluent; on bedside examination, the patient speaks hesitantly, often producing the principal, meaning-containing nouns and verbs but omitting small grammatical words and morphemes. This pattern is called agrammatism or telegraphic speech. An example is “wife come hospital.” Patients with acute Broca aphasia may be mute or may produce only single words, often with dysarthria and apraxia of speech. They make many phonemic errors, inconsistent from utterance to utterance, with substitution of phonemes usually differing only slightly from the correct target (e.g., p for b). Naming is deficient, but the patient often manifests a “tip of the tongue” phenomenon, getting out the first letter or phoneme of the correct name. Paraphasic errors in naming are more frequently of literal than verbal type. Auditory comprehension seems intact, but detailed testing usually reveals some deficiency, particularly in the comprehension of complex syntax. For example, sentences with embedded clauses involving prepositional relationships cause difficulty for patients with Broca aphasia in comprehension as well as in expression (“The rug that Bill gave to Betty tripped the visitor”). This may reflect the demands that these types of sentences make on working memory and other functions that depend on the frontal lobe. A study of grammatical comprehension in normal subjects with positron emission tomography (PET) scanning did show activation of the left frontal, Broca area during this function ( ). Repetition is hesitant in these patients, resembling their spontaneous speech. Reading is often impaired, despite relatively preserved auditory comprehension. Patients with Broca aphasia may have difficulty with syntax in reading, just as in auditory comprehension and speech. Writing is virtually always deficient in Broca aphasia. Most patients have a right hemiparesis, necessitating use of the nondominant, left hand for writing, but this left-handed writing is far more abnormal than the awkward renditions of a normal right-handed subject. Many patients can scrawl only a few letters.

Associated neurological deficits of Broca aphasia include right hemiparesis, hemisensory loss, and apraxia of the oral apparatus and the nonparalyzed (typically left) limbs. Apraxia in response to motor commands is important to recognize because it may be mistaken for comprehension disturbance. Comprehension should be tested by responses to yes-no questions or commands to point to an object. The common features of Broca aphasia are listed in Table 13.1 .

TABLE 13.1

Bedside Features of Broca Aphasia

Feature	Syndrome
Spontaneous speech	Nonfluent, mute, or telegraphic, sometimes dysarthric
Naming	Impaired
Comprehension	Intact (mild difficulty with complex grammatical phrases)
Repetition	Impaired
Reading	Often impaired (“third alexia”)
Writing	Impaired (dysmorphic, dysgrammatical)
Associated signs	Right hemiparesis
	Right hemisensory loss
	± Apraxia of left limbs

An important clinical feature of Broca aphasia is its frequent association with depression ( ). Patients with Broca aphasia are typically aware of and frustrated by their deficits. At times, they become withdrawn and refuse help or therapy. Usually, the depression lifts as the deficit recovers, but it may be a limiting factor in rehabilitation.

The lesions responsible for Broca aphasia usually include the traditional Broca area in the posterior part of the inferior frontal gyrus, along with damage to adjacent cortex and subcortical white matter. Most patients with lasting Broca aphasia, including Broca original cases, have much larger left frontoparietal lesions, including most of the territory of the upper division of the left middle cerebral artery. Such patients typically evolve from global to Broca aphasia over weeks to months. Patients who manifest Broca aphasia immediately after their strokes, by contrast, have smaller lesions of the inferior frontal region, and their deficits generally resolve quickly. In computed tomography (CT) scan analyses at the Boston Veterans Administration Medical Center, lesions restricted to the lower precentral gyrus produced only dysarthria and mild expressive disturbance. Lesions involving the traditional Broca area (Brodmann areas 44 and 45) resulted in difficulty initiating speech, and lesions combining Broca area, the lower precentral gyrus, and subcortical white matter yielded the full syndrome of Broca aphasia ( ). In studies by the same group, damage to two subcortical white matter sites—the rostral subcallosal fasciculus deep to the Broca area and the periventricular white matter adjacent to the body of the left lateral ventricle—was required to cause permanent nonfluency. Fig. 13.3 shows an MRI scan from a case of Broca aphasia.

Wernicke Aphasia

Wernicke aphasia may be considered a syndrome opposite to Broca aphasia, in that expressive speech is fluent, but comprehension is impaired. The speech pattern is effortless and sometimes even excessively fluent (logorrhea). A speaker of a foreign language might notice nothing amiss, but a listener who shares the patient’s language detects speech empty of meaning, containing verbal paraphasias, neologisms, and jargon productions. In milder cases, the intended meaning of an utterance may be discerned, but the sentence goes awry with paraphasic substitutions. Naming in Wernicke aphasia is deficient, often with bizarre, paraphasic substitutions for the correct name. Auditory comprehension is impaired, sometimes even for simple nonsense questions. Repetition is impaired; whispering a phrase in the patient’s ear, as in a hearing test, may help cue the patient to attempt repetition. Reading comprehension is usually affected similarly to auditory comprehension, but occasional patients show greater deficits in one modality versus the other. The discovery of relatively spared reading ability in Wernicke aphasics is important in allowing these patients to communicate. Writing is also impaired, but in a manner quite different from that of Broca aphasia. The patient usually has no hemiparesis and can grasp the pen and write easily. Written productions are even more abnormal than oral ones, however, in that spelling errors are also evident. Writing samples are especially useful in the detection of mild Wernicke aphasia.

Associated signs are limited in Wernicke aphasia; most patients have no elementary motor or sensory deficits, although a partial or complete right homonymous hemianopia may be present. The characteristic bedside examination findings in Wernicke aphasia are summarized in Table 13.2 .

TABLE 13.2

Bedside Features of Wernicke Aphasia

Feature	Syndrome
Spontaneous speech	Fluent, with paraphasic errors
	Usually not dysarthric
	Sometimes logorrheic
Naming	Impaired (often bizarre paraphasic misnaming)
Comprehension	Impaired
Repetition	Impaired
Reading	Impaired for comprehension, reading aloud
Writing	Well-formed, paragraphic
Associated signs	± Right hemianopia
	Motor, sensory signs usually absent

The psychiatric manifestations of Wernicke aphasia are quite different from those of Broca aphasia. Depression is less common; many Wernicke aphasics seem unaware of or unconcerned about their communicative deficits. With time, some patients become angry or paranoid about the inability of family members and medical staff to understand them. This behavior, similarly to depression, may hinder rehabilitative efforts.

The lesions of patients with Wernicke aphasia are usually centered on the posterior portion of the superior temporal gyrus, extending into the inferior parietal lobule and middle temporal gyrus ). Fig. 13.4 shows a typical example. In the acute phase, the ability to match a spoken word to a picture is quantitatively related to decreased perfusion of the Wernicke area on perfusion-weighted MRI, indicating less variability during the acute phase than after recovery has taken place ( ). Recent literature (see ) has suggested that auditory comprehension is subserved by wider regions of the left temporal lobe. Electrical stimulation of the Wernicke area produces consistent interruption of auditory comprehension, supporting the importance of this region for decoding auditory language ( ). A receptive speech area in the left inferior temporal gyrus has also been suggested by electrical stimulation studies and by a few descriptions of patients with seizures involving this area ( ). In terms of vascular anatomy, Wernicke aphasia is generally associated with the inferior division of the left middle cerebral artery.