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Speech and Language Disorders
Introduction
Speech and language are important to our human existence, and they affect our ability to communicate with other people. Speech involves the articulation of language sounds via the vocal apparatus. Language involves the manipulation of symbols in the production and comprehension of communication.
Aphasias are acquired disorders of language secondary to brain disease. The aphasias include specific syndromes in which language functions are affected by lesions of the left hemisphere. The syndromes are diagnosed by the bedside examination of speech and language presented in Chapter 1.3 .
Evaluation of the Patient With Aphasia
The first task of the neurologist in evaluating a speech or language problem is to determine whether the patient is aphasic. The definition of aphasia distinguishes acquired language disorders from three other causes of abnormal communication:
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Developmental language disorders are excluded because aphasia is an acquired disorder in a patient with premorbid normal speech and language function.
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Motor speech disorders, such as dysarthria, disturb only spoken language output; written language expression and comprehension remain intact.
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Psychiatric disorders are excluded because the abnormal language content in psychiatric patients is due to a disturbed thought process rather than a language defect.
Paraphasic errors and neologisms (nonexistent words) characterize aphasia more than psychosis, except in a few untreated schizophrenic patients with “word salad speech” or in bipolar patients in a manic state who occasionally make “clang associations.” A key difference between psychosis and aphasia is the patient’s behavior; an aphasic patient usually behaves appropriately, although they are unable to communicate. The presence of other focal left hemisphere signs in aphasic patients also helps to indicate a neurologic rather than psychiatric disorder.
Motor Speech Disorders
Motor speech disorders refer to abnormalities of speech articulation in the absence of language dysfunction. On the bedside mental status examination, spontaneous speech, repetition, naming, and reading aloud may be abnormal, but auditory comprehension, reading comprehension, and writing should be intact. In general, if the examiner transcribes the speech output of a dysarthric patient and then reads it aloud, it should sound normal. Motor speech disorders are generally divided into dysarthria and apraxia of speech.
Dysarthria
Dysarthria refers to a consistent misarticulation of phonemes, resulting from disturbances of muscular control over the speech mechanism due to damage of the central or peripheral nervous system. By definition, dysarthria is a neurologic disorder. It excludes local, structural disorders such as cleft lip or palate and laryngectomy. The type of dysarthria can aid in the diagnosis of disorders of the central and peripheral nervous systems.
Classification of Dysarthria
Dysarthria is divided into six subtypes based on neuroanatomic lesions, but it is distinguishable by auditory-perceptual characteristics that a clinician can learn to recognize at the bedside. Table 5.2.1 lists a summary of the Mayo Clinic classification of dysarthria. The six types of dysarthria are flaccid, spastic, ataxic, hypokinetic, hyperkinetic, and mixed. Subsequently, the Mayo Clinic group added a subtype of spastic dysarthria called unilateral upper motor neuron dysarthria.
Table 5.2.1
Classification of Dysarthrias
Darley FL, Aronson AE, Brown JR. Differential diagnostic patterns of dysarthria. J Speech Hear Res. 1969;12:246-269, and Duffy JR. Motor speech disorders. Substrates, differential diagnosis, and management. St. Louis:Mosby; 1995.
| Type | Localization | Auditory Signs | Diagnoses |
|---|---|---|---|
| Flaccid | Lower motor neuron | Breathy, nasal voice; imprecise consonants | Stroke; myasthenia gravis |
| Spastic | Bilateral upper motor neuron | Strain, strangle; harsh voice; slow rate; imprecise consonants | Bilateral strokes; tumors; primary lateral sclerosis |
| Unilateral upper motor neuron | Unilateral upper motor neuron | Consonant imprecision; slow rate; harsh voice quality | Stroke; tumor |
| Ataxia | Cerebellum | Irregular articulatory breakdowns; extensive and equal stress | Stroke; degenerative disease |
| Hypokinetic | Extrapyramidal | Rapid rate; reduced loudness; monopitch; monoloudness | Parkinson disease |
| Hyperkinetic | Extrapyramidal | Prolonged phonemes; variable rate; inappropriate silences; voice stoppages | Dystonia; Huntington disease |
| Spastic-flaccid | Upper and lower motor neuron | Hypernasality; strain-strangle; harsh voice; slow rate; imprecise consonants | Amyotrophic lateral sclerosis; multiple strokes |
Flaccid dysarthria results from bilateral, lower motor neuron lesions or bulbar palsy, involving cranial nerves, neuromuscular junctions, or muscles. The auditory characteristics include
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Breathy voice quality,
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Hypernasality, and
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Imprecise consonants (errors or distortions of consonant sounds).
Flaccid dysarthria may result from a brainstem stroke, traumatic brain injury, or neuromuscular disorders such as myasthenia gravis, bulbar polio, or Guillain-Barré syndrome.
Spastic dysarthria results from bilateral upper motor neuron lesions, also referred to as pseudobulbar palsy. The auditory characteristics are
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A strain-strangle, harsh voice quality;
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Slow rate; and
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Imprecisely articulated consonants, often with hypernasality.
Causes of spastic dysarthria include bilateral strokes, tumors, and degenerative diseases such as primary lateral sclerosis.
Unilateral upper motor neuron (UUMN) dysarthria results from a UUMN lesion. The auditory signs are similar to the spastic type but are less severe. They include
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Harsh voice,
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Slow rate, and
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Imprecise consonants.
Common causes of UUMN dysarthria are a unilateral hemisphere stroke or brain tumor.
Ataxic dysarthria results from damage in the cerebellum or its connections. The auditory signs are
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Irregular articulatory breakdowns and
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Excessive and equal stress, also referred to as scanning speech.
Possible causes include cerebellar degenerations, strokes, and tumors. Multiple sclerosis frequently produces ataxic dysarthria, but it may be mixed with elements of flaccid, spastic, or UUMN dysarthria.
Hypokinetic dysarthria is associated with extrapyramidal or basal ganglia diseases. The auditory characteristics are
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Rapid rate,
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Reduced loudness,
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Monopitch (unvarying pitch level), and
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Monoloudness (unvarying loudness level).
The most common cause of hypokinetic dysarthria is Parkinson disease. Occasionally, strokes involving the basal ganglia can mimic this pattern.
Hyperkinetic dysarthria is associated with extrapyramidal disorders that have increased rather than decreased movement. The auditory signs include
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Prolonged phonemes (individual speech sounds become stretched out),
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Variable rate (sometimes too fast, sometimes too slow),
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Harsh voice quality,
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Inappropriate pauses or silences, and
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Voice stoppages (inappropriate absence of phonation).
Common causes of hyperkinetic dysarthria are dystonia (e.g., dystonia musculorum deformans), Joseph disease, and Huntington disease.
Mixed dysarthria has several subtypes. The auditory perceptual characteristics vary depending on which neurologic systems are involved.
Spastic-flaccid dysarthria results from involvement of both the upper and lower motor neuron systems. The auditory characteristics are
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Hypernasality,
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Strain-strangle, liquid sounding voice quality (phonation is accompanied by a gurgle),
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Extremely slow rate, and
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Severe consonant imprecision.
Spastic-flaccid dysarthria is typically caused by amyotrophic lateral sclerosis (ALS) but may be seen in multiple strokes.
Multiple sclerosis may produce a mixed ataxic-spastic-flaccid dysarthria resulting from cerebellar, upper motor neuron, and lower motor neuron involvement. The ataxic features (excessive and equal stress, slow rate) may be most prominent.
Apraxia of Speech
Apraxia of speech is a disorder intermediate between the dysarthrias and the aphasias. Apraxia of speech is a disorder of the programming of rapid sequences of phonemes. The patient does not have significant weakness, slowness, or incoordination of the speech apparatus. By this definition, apraxia of speech is a motor speech disorder, not a language disorder or aphasia.
Apraxia of speech is distinguished from dysarthria because the misarticulations are inconsistent; the patient may pronounce the same word differently, and sometimes normally, in different utterances. For example, a patient trying to repeat the word “catastrophe” might produce five different utterances, with one correct.
Apraxia of speech is distinguished from aphasia by the lack of language disorder. Apraxia of speech is rarely an isolated deficit and is often mixed with aphasia and sometimes with dysarthria.
The key features of apraxia of speech are
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Effortful, trial and error, groping articulatory movements, with attempts at self-correction;
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Dysprosodia, or disruptions in rhythm, stress (emphasis), and intonation of speech;
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Inconsistency, as in production of the word “catastrophe”; and
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Difficulty initiating speech.
Localization and Cause of Apraxia of Speech
The anatomic basis of the motor programming of speech sequences is likely the classical Broca area in the left inferior frontal gyrus because patients with Broca aphasia frequently have an associated apraxia of speech. The disorder can be seen with strokes, traumatic brain injury, degenerative disorders, tumors, and other causes.
Muteness
A patient with no speech output may have severe dysarthria (anarthria), severe apraxia of speech, a nonneurologic disorder such as a laryngeal obstruction, a frontal lobe syndrome with akinetic mutism, an extrapyramidal disorder such as severe Parkinson disease, a psychogenic state such as catatonia, simple uncooperativeness, or stupor.
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Muteness must be differentiated from aphasia:
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Some attempt at language output must be present to permit an examiner to diagnose aphasia.
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Normal writing and normal language comprehension make aphasia unlikely.
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Other signs of left hemisphere injury such as right hemiparesis and right hemianopia point to aphasia.
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In general, the aphasic patient tries to communicate by gesturing, grunting, or pointing; the patient is mute in speech but not in other behaviors.
Aphasias
Aphasias are divided into syndromes involving the primary language cortex and those involving other cortical and subcortical centers. The primary language cortex is arranged as a circuit of centers around the left sylvian fissure, involving the operculum (or roof of the sylvian fissure) in the frontal, parietal, and temporal lobes.
Since aphasia was first described, several clinical classifications of aphasia have been introduced. The aphasia syndrome diagnosis can be supported by standardized batteries such as the Boston Diagnostic Aphasia Examination (BDAE) or the Western Aphasia Battery (WAB).
There has been a tendency to classify aphasias into two groups: expressive versus receptive, motor versus sensory, fluent versus nonfluent, and anterior versus posterior aphasias. The problem with the expressive-receptive and motor-sensory dichotomies is that aphasias are rarely purely expressive or receptive. Virtually all persons with aphasia have abnormal language expression. The terms fluent versus nonfluent aphasia are at least descriptive and easily understood.
There are eight classical aphasia syndromes:
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Broca
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Wernicke
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Global
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Conduction
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Anomic
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Transcortical motor
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Transcortical sensory
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Mixed transcortical aphasia
Mixed transcortical aphasia is also called the syndrome of the isolation of the speech area. There are subsyndromes such as aphemia, pure word deafness, and the subcortical aphasia syndromes
Broca Aphasia
Paul Broca described two patients who had a difficulty in articulation yet could comprehend spoken language. In modern descriptions, the typical patient with Broca aphasia speaks little or nonfluently. Broca aphasia can range from complete muteness to single word utterances or phrases and short sentences produced hesitantly. The disorder is an aphasia rather than a motor speech disorder because grammatical constructions are disturbed. Expressive speech is agrammatic; it reads like a telegram. For example, a patient with Broca aphasia who wanted to express that his wife would be coming to the hospital might say “wife…come …hospital.” See Table 5.2.2 .
Table 5.2.2
Broca, Wernicke, and Global Aphasias
| Feature | Broca | Wernicke | Global |
|---|---|---|---|
| Spontaneous speech | Nonfluent, hesitant, from mute to agrammatic; often dysarthria | Fluent with paraphasic errors of both phonemic and verbal type | Nonfluent, mute or restricted to a stereotyped phrase |
| Naming | Impaired (tip-of-the-tongue) | Impaired, often paraphasic | Impaired |
| Auditory comprehension | Intact for simple material; impaired for complex syntactic constructions | Impaired, often for even simple questions | Impaired |
| Repetition | Impaired; hesitant | Impaired | Impaired |
| Reading | Difficulty reading aloud; often poorer reading than auditory comprehension | Usually impaired, with exceptions | Impaired |
| Writing | Difficulty writing, even with left hand | Well-formed but paragraphic | Impaired |
| Associated signs | Right hemiparesis; right hemisensory loss; apraxia of left limbs | With or without right hemianopia, usually no motor or sensory abnormalities | Most have right hemianopia, right hemiparesis, right hemisensory loss; often apraxia |
| Behavior | Frustrated, depressed, but appropriate | Often unaware of deficits; may be inappropriately happy; later sometimes angry, suspicious | Often depressed |
Naming in Broca aphasia is impaired. Often the patient has some idea of the name and produces the initial letter or syllable, the so-called “tip of the tongue phenomenon.” In some patients, naming of actions (verbs) is worse than naming of objects (nouns).
Repetition in Broca aphasia is usually only slightly better than spontaneous speech, showing the same articulatory difficulty and hesitancy.
Auditory comprehension is largely preserved, but sentences with complex grammar cause comprehension problems. For example, the sentence “the sculpture that Mary gave to Bill was beautiful” may cause confusion about who gave the sculpture and who received it. Modern evidence confirms that the Broca area is involved in both production and comprehension of phrases with complex syntax.
Reading is often more affected than auditory comprehension in Broca aphasia.
Writing is also affected. Most patients have weakness of the right arm, making it difficult for a right-handed patient to write with the dominant hand. The patient may refuse to write with the left hand, but if they attempt to write, only a few awkward letters emerge. Persons with injuries to the right arm can learn surprisingly quickly to write awkwardly but intelligibly with the left hand. The agraphia of Broca aphasia is thus not simply a motor disorder but is a central language disorder affecting writing.
Associated deficits with Broca aphasia include weakness of the right face, arm, and leg and often some sensory loss on the right side of the body. Visual fields are usually spared. Some studies have found an association between poststroke depression and infarctions of the anterior left hemisphere. Behaviorally, patients with Broca aphasia seem appropriately concerned about their stroke deficits; they are frustrated but fully aware. Some patients with Broca aphasia may show apraxia of the left limbs and fail to follow commands for use of the left limbs. The clinician should recognize this apraxia and not mistake it for lack of comprehension.
Lesions of Broca aphasia classically involve the posterior two-thirds of the inferior frontal convolution, the pars triangularis and pars opercularis. Precise lesion localization has significant clinical implications:
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Infarctions restricted to the cortical Broca area are associated with excellent recovery over a few weeks.
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Patients with lesions in areas 44 and 45 have primarily a deficit in initiation of speech without true aphasia.
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Patients with lesions only of the lower motor cortex have only dysarthria and speech hesitancy.
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Both areas 44 and 45 and the lower motor cortex have to be damaged to produce the full picture of Broca aphasia.
Fig. 5.2.1 shows a magnetic resonance imaging (MRI) scan from a patient with a transitory Broca aphasia and apraxia of speech. Patients with lasting Broca aphasia usually have larger lesions, involving not only Broca area but also much of the frontoparietal operculum.
Prognosis for recovery in Broca aphasia depends on how soon after the stroke that the patient is examined. Naeser and her colleagues reported that lesions associated with poor recovery of fluent speech always include two subcortical areas: (1) the subcallosal fasciculus deep to Broca area, and (2) the periventricular white matter along the body of the left lateral ventricle. The combined cortical-subcortical frontal lesion appears to be required for lasting nonfluency.
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