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Motor Speech Signs in Neurologic Disease
Motor Speech Signs in Neurologic Disease FREDERIC L. DARLEY, Ph.D. ARNOLD E. ARONSON, Ph.D. JOE R. BROWN, M.D.
The alterations of speech and voice which are heard in certain neurologic diseases constitute useful diagnostic signs. Motor speech disorders, collectively known as dysarthria, may have a "localizing value," in the words of Grewel, " ... sometimes even suggesting a tentative diagnosis to the phonetically trained ear, when neurological examination still shows no convincing neurological symptoms." As currently employed in speech pathology and neurology, the term "dysarthria" means something more comprehensive and yet more specific than is implied in the definition offered by Dorland's Illustrated Medical Dictionary: "imperfect articulation in speech." Typically, multiple speech processes are affected simultaneously. Not only the process of articulation but all the other basic motor processes of respiration, phonation, resonance and prosody present distinctive changes that one can learn to recognize. The term is best restricted, however, to speech dysfunctions which are neurogenic. As used here, then, "dysarthria" will refer to the wide variety of impairments of the five basic motor speech processes that manifest disturbances in muscular control over the speech mechanism from damage to the central or peripheral nervous system. These impairments seldom occur in isolation but rather in various combinations, with impaired articulation being a common denominator. So conceived, dysarthria calls for one's listening for much more than simply the traditionally reported "slurred speech." Each basic process may be impaired in a number of ways, so that one learns to observe numerous separable characteristics which individually reveal distinctive alterations in different diseases and together- observed concurrently in a given patient - suggest a specific disease entity.
WHAT TO OBSERVE To make these systematic observations one must sample several types of speech and voice production. A sample of contextual speech Medical Clinics of North America- Va!. 52, No. 4, July, 1968
835
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FREDERIC
L.
DARLEY, ARNOLD
E.
ARONSON, JOE
R.
BRoWN
can be elicited by having the patient tell about a picture representing a situation, or one may have the patient read a standard paragraph of simple prose containing all the consonants and vowels of English as well as some consonant clusters. ,:. This procedure is preferred to asking the patient to repeat tongue-twisters, which are difficult even for normal speakers and not adequate as samples of normal articulatory performance. For analysis of his phonation, the patient should be asked to prolong the vowel lahl as long, clearly and steadily as possible. Finally, for the purpose of evaluating his oral diadochokinetic rate, he should be asked to repeat as rapidly as possible a bilabial sound, "puh-puh-puh ... ," a sound requiring elevation of the tongue tip, "tuh-tuh-tuh ... ," and a sound requiring elevation of the back of the tongue, "kuh-kuh-kuh.... " The speech and voice so produced can be analyzed in terms of the basic processes as follows. Respiration 1. Is there sufficient breath support for speech, or are phrases short because breath supply is inadequate? 2. Is inhalation audible? 3. Is the inhalation-exhalation cycle smooth, or are there sudden forced gusts of breath? 4. Is exhalation coordinated with the onset of phonation, or is there air wastage?
Phonation PITCH. 1. Is the pitch level appropriate to the patient's age and sex, too low, or too high? 2. Are there appropriate inflectional pitch changes, or is pitch usage monotonous (monopitch)? 3. Are there sudden, uncontrolled pitch breaks? 4. Is there a vocal tremor? LOUDNESS. 1. Is the voice adequately loud? 2. Are there normal variations in loudness? 3. Are there sudden bursts of loudness? 4. Does loudness decay as speech continues? VOICE QUALITY. 1. Is the voice harsh or raspy? 2. Is there audible escape of unused breath (breathiness)? 3. Does the voice sound strained or strangled (as if being effortfully squeezed through the glottis)? 4. Are there sudden stoppages of voice?
"Such a passage is "My Grandfather," reproduced (with slight alterations) from Van Riper: You wished to know all about my grandfather. Well, he is nearly 93 years old yet he still thinks as swiftly as ever; he dresses himself in an ancient black frock coat, usually minus several butto1'ls. A long, flowing beard clings to his chin, giving those who observe him a pronounced feeling of the utmost respect. When he speaks, his voice is just a bit cracked and quivers a trifle. Twice each day he plays skillfully and with zest upon our small organ. Except in the winter when the ooze or snow or ice prevents, he slowly takes a short walk in the open air each day. We have often urged him to walk more and smoke less, but he always answers, "Banana oil!" Grandfather likes to be modern in his language.
MOTOR SPEECH SIGNS IN NEUROLOGIC DISEASE
837
Resonance 1. Is there hypernasality? 2. Is there nasal emission of air during speech? 3. Do hypernasality and nasal emission increase as speech continues? 4. Is there hyponasality? Articulation 1. Are consonant sounds precisely produced, or are they slighted or run together? 2. Is there clumsiness in going from one consonant to another? 3. Are consonant inaccuracies consistent, or is there irregular, unsystematic disintegration of articulation? 4. Are vowels distorted so that their identity is lost? 5. Are sounds unduly prolonged? 6. Are sounds repeated? Prosody 1. Is rate of speech abnormally slow or rapid? 2. Is speech made up of short rushes separated by pauses? 3. Are there inappropriate silences? 4. Are inter-word and inter-syllable intervals prolonged? 5. Is emphasis on key words and stressed syllables reduced? 6. Is there excessive stress on usually unstressed syllables and words? Additional Signs In addition to these auditory aspects of speech, one should be attentive to associated visual cues. 1. Is there tremor of the head? 2. Is there myoclonus of facial, palatal and possibly laryngeal muscles? 3. Are there other involuntary movements of face or body? 4. Are facies masked? 5. Are tongue movements in all directions rapid and smooth, or sluggish? 6. Is there fasciculation of the tongue? 7. Is there atrophy of the borders of the tongue? 8. Is there a sucking reflex? 9. Is the jaw jerk increased? 10. Is palate elevation adequate? 11. Is contraction of the alae of the nose or facial grimacing noticeable during speech? 12. Are accessory respiratory muscles used? SPECIFIC SPEECH DEVIATIONS The relationship of the above-listed speech signs to various neurologic diseases has been determined through detailed analysis of
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L. DARLEY, ARNOLD E. ARONSON, JOE R. BRoWN
speech samples. These were taken from patients assigned by unequivocal diagnosis to one of seven categories of motor impairment, and numbering 30 or more in each such group: pseudobulbar palsy (bilateral upper motor neuron lesion), bulbar palsy (lower motor neuron lesion), amyotrophic lateral sclerosis (both upper and lower motor neuron lesions), cerebellar lesions, parkinsonism, choreoathetosis and dystonia. Although the diagnostic significance of some speech deviations, especially the mild ones, is often not clear-cut, the relative frequency of occurrence of many speech signs is uniquely different in the various diagnostic groups. On hearing a given deviation, therefore, one may hypothesize that it is caused by a given type of impairment. Which diagnostic entity is the most likely to be associated with each of several specific speech deviations? RESPIRATION. Adequate breath support for speech requires smooth, controlled exhalation of reasonable duration and of sufficient pressure to create the necessary amplitude of vocal-fold vibration. There are three reasons for inadequacy of breath support: (1) respiratory musculature is weak; (2) peripheral resistance to the exhaled breath column at the larynx or the velopharyngeal port is decreased, allowing air wastage; and (3) peripheral resistance is excessive-too great for normal respiratory muscles to overcome. The second reason applies in bulbar palsies involving the tenth cranial nerve. There is often breathy voice with marked air wastage at the glottis with resulting shortening of phrases. Audible inhalation is most suggestive of bulbar involvement (bulbar palsy, amyotrophic lateral sclerosis), the vocal folds being incompletely abducted. The third reason applies in patients with upper motor neuron lesions (pseudobulbar palsy, amyotrophic lateral sclerosis). Shortening of phrases is typical here too. An effortful grunt at the ends of phrases is sometimes associated with exhaustion of breath supply. The hyperkinetic movement disorders, especially athetosis and chorea, are the most likely causes of interference with smooth cycling. Some patients (especially choreics) speak with irregular forced gusts of breath, while others (especially athetoids) display imperfect timing of their exhalations to coincide with onset of phonation, or vice versa. Also patients with hyperkinetic disorders may be noticeable for shortening of phrases as exhalation is interrupted. PHONATION. Because it occurs in many patients among all of the disease categories, monopitch is not a particularly useful sign; but it is markedly more prominent in parkinsonism than in the other groups, as is monotony of loudness. Just as paucity of bodily movement is characteristic of parkinsonism, so is paucity of vocal variation. Inadequate loudness and decay of loudness as speech proceeds are also more frequently heard in parkinsonism than in the other categories. Excessive loudness variations, on the other hand, are most often heard in choreoathetosis and dystonia. Though frequently noted in myxedema, excessively low pitch is most characteristic of patients with spasticity (pseudobulbar palsy, amyotrophic lateral sclerosis). In patients with spasticity low pitch is
MOTOR SPEECH SIGNS IN NEUROLOGIC DISEASE
839
commonly associated with harsh voice quality, a strained, strangled sound as though air were being effortfully squeezed through the glottis, and pitch breaks. Sudden voice stoppages are also heard in pseudobulbar palsy, but they occur even more frequently in patients with dystonia, who experience unpredictable spasmodic blockings of laryngeal and oral acti vity. All of these phonatory phenomena may be apparent in contextual speech but are made even more evident when the patient is asked to prolong the vowel lah/. Often voice tremor is associated with the other manifestations of hereditary essential tremor. However, it is frequently seen in patients with dystonic and spastic syndromes. The strongest indication from continuously breathy voice is bulbar palsy, the vocal folds being incompletely adducted during phonation. The voices of many patients with parkinsonism are also consistently breathy, though usually to a less severe degree than in bulbar palsy. RESONANCE. Hypernasality bespeaks velopharyngeal incompetence, represented in the layman's stereotype of "cleft-palate speech." Velopharyngeal mechanisms which are intact structurally but inadequately innervated similarly allow excessive nasal resonance and the nasal emission of the phonated and articulated air stream. Pronounced hypernasality and nasal emission most often suggest bulbar palsy, in which paresis of the soft palate prevents attainment of the critical limits of closure. Hypernasality is not uncommon in pseudobulbar palsy as well, the muscles of the velopharyngeal port moving too slowly in rapid contextual speech to effect firm closure; but the degree of hypernasality is typically less than in bulbar palsy, and nasal emission is not heard. Hypernasality is often a presenting symptom in myasthenia gravis. Marked increase in hypernasality (together with deterioration of articulation) as a patient speaks or reads aloud at length is highly suggestive of myasthenia gravis. Evidence of fatigue with prolongation of effort may be more readily elicited in some myasthenic patients by a more restricted muscular task such as repeating lahl once per second for several minutes. On the other hand, hyponasality is not an expected sign of any neurologic disease. If one hears the nasal consonants Iml, 1nl and Ingl altered to resemble Ibl, Idl and Igl, one should suspect that normal nasal resonance is prevented by occlusion of the nasal pathway by hypertrophied adenoids, a deviated septum, rhinitis or nasopharyngeal tumor. ARTICULATION. In itself, imprecise production of consonants is not suggestive of any certain diagnostic category, since all of the groups studied had articulatory troubles of some kind. There are, however, variations in the type of faulty production from disorder to disorder. Fairly consistent articulatory errors are the rule in spasticity, flaccidity and the hypokinesis of parkinsonism - that is, errors of the same kinds recur. In spasticity the tongue and lips move sluggishly, so that sounds are slighted and elided and sequences of adjacent consonants (as in swiftly) are produced clumsily. In the bulbar palsies involving the twelfth cranial nerve, the tongue lies flaccid in the floor
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L. DARLEY, ARNOLD E. ARONSON, JOE R. BROWN
of the mouth, so that special difficulty is heard in the production of the vowels leel and Ii/ (as in seat and sit), and the consonants Itl, Idl, Ill, Isl and Ishl, all of which require elevation of the tip of the tongue. When the seventh cranial nerve is involved, lip movements are reduced, so that production of the vowels and bilabial consonants is impaired. The parkinsonian patient fails to move his articulators through the full excursion necessary for crisp consonants, so that all his sounds are likely to be blurred and fragmentary. In contrast to the performance observed in those groups, the ataxic articulation of the patient with a cerebellar disorder and the hyperkinetic problems of the patient with chorea or athetosis or dystonia are less consistent. In cerebellar disorders one may hear a generally good to fair performance in articulation punctuated irregularly by sudden breakdowns in accuracy, the disintegration due to momentary loss of coordination, sometimes involving a single sound, more likely a syllable, but often a group of syllables whose identity becomes lost. Adventitious movements cause similar unpredictable distortion of sounds in the hyperkinesias. Consonants usually suffer most in the dilapidated articulation of neurologic diseases, vowels usually remaining surprisingly intact except in advanced amyotrophic lateral sclerosis and in other cases of such extreme loss of motor power that they can be termed "anarthria." Not uncommon, however, in facial, tongue and oropharyngeal dystonia and in choreoathetosis is a marked distortion of vowels due to changes in mouth postures during speech. Some vowel distortion may be heard also in the articulatory disintegration of cerebellar disorders and, as mentioned above, in severe lingual and labial paresis of bulbar palsy. Parkinsonism, almost exclusively, is associated with repetition of initial sounds of words. This error suggests the occurrence of speech arrests analogous to the motor arrests observed in walking. Unusual prolongation of sounds is most frequently found in cerebellar disorders, where the timing of movements is faulty; however, one is likely to hear prolongation of speech sounds in the hyperkinetic disorders and indeed in any patient whose rate of speech is substantially slowed, as discussed below. Related to these articulatory inefficiencies observed in contextual speech is the performance on tests of the oral diadochokinetic rate (repetition of "puh," "tuh" and "kuh"). In spastic states the repetition is slow but rhythmical, and precision of articulation is reduced. In flaccid conditions rate may be slowed and precision of "tuh" and "kuh" particularly poor because of specific difficulty with tongue elevation, or on "puh" because of weakness of the lips. Parkinsonian patients move their articulators rapidly through a very narrow range of motion; therefore the identity of the separate pulses may be almost lost. In ataxia and hyperkinesia the rates may be normal or somewhat slow, but typically they are characterized by dysrhythmia and irregularities of pitch and loudness. PROSODY. In all the neurologic categories except parkinsonism, many of the patients speak at a slow rate. Most extreme slowness of
MOTOR SPEECH SIGNS IN NEUROLOGIC DISEASE
841
speech is observed in amyotrophic lateral sclerosis and pseudobulbar palsy. In parkinsonism patients sometimes, though not always, display fast rate. Occasionally one hears an increase in rate as speech proceeds; this phenomenon, analogous to festination in gait, is probably not as common as textbooks suggest. More typical-and indeed pathognomonic of parkinsonian speech-are short rushes of speech separated by pauses at points often not logically prescribed by the meaning. Variable rate, alternating between slow and fast, is often noted in parkinsonism, but it is even more prominent in choreoathetosis. Inappropriate silences occur more often in parkinsonism than in any other disorder, but they are frequent in the speech of choreoathetosis and dystonia. Two opposite kinds of alteration in normal vocal emphasis distinguish the neurologic groups. General reduction of stress on key words and accented syllables is most typical of parkinsonism, with lesser degrees observable in pseudobulbar palsy and amyotrophic lateral sclerosis. An equalization of stress of quite another kind is heard frequently in cerebellar disorders and the hyperkinesias: syllables and words usually unstressed are stressed equally with those usually stressed; the intervals between syllables are somewhat prolonged; and thus speech proceeds at a measured, artificially even pace. This is the "scanning speech" described by Charcot in 1877 as pathognomonic of advanced cases of multiple sclerosis. Its frequent appearance in ataxic patients, and in some patients with movement disorders as well, suggests that it may be a compensatory mechanism, an attempt by the patients to guard against the disintegrations and interruptions of voice and articulation that beset them.
DISTINCTIVE PATTERNS OF DYSARTHRIA Detection of the above-described individual speech deviations can suggest to the clinician the categories of neurologic disease in which these deviations have been found most often. His assurance in so pigeonholing them increases significantly as he finds a number of related deviations occurring simultaneously in a given patient. One may hear in one case a cluster of four or five characteristic speech errors, all known to be found to some degree in disorders of a certain type, and thus more safely expect appropriate search to reveal such an entity. Seven of these frequently appearing patterns are presented. Pseudobulbar palsy (spastic dysarthria) typically makes speech slow and labored, the articulation being rather consistently imprecise, especially on more complicated groups of consonant sounds. Pitch is low and monotonous. Voice quality is harsh and often strained or strangledsounding. There may be considerable hypernasality, but usually no nasal emission is audible. Associated nonspeech signs are increase of deep tendon reflexes, appearance of the sucking reflex, increased jaw jerk, sluggish tongue movements and activity of accessory respiratory musculature. Bulbar palsy (flaccid dysarthria) produces hypernasality with asso-
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L. DARLEY, ARNOLD E. ARONSON, jOE R. BROWN
ciated nasal emission of air during speech as its most prominent speech symptom. Inhalation is often audible and exhalation is often breathy, air wastage being manifested also in shortness of phrases. Articulation is often imprecise on either or both of two bases: (1) consonants may be weak through failure to impound sufficient intraoral breath pressure because of velopharyngeal incompetence; (2) immobility of tongue and lips because impairment of the hypoglossal and facial nerves prevents normal production of vowels and consonants. Associated nonspeech signs are fasciculation and atrophy of the tongue, reduced rate of alternating motion of tongue and lips, poor elevation of the soft palate and nasal alar contraction and grimacing as the patient tries to compensate for velopharyngeal incompetence. Amyotrophic lateral sclerosis (combined spastic and flaccid dysarthria) has a developing effect on speech. In an earlier stage either spastic or flaccid speech and nonspeech signs predominate; in an advanced stage both sets of features described above are present. Slow rate, low pitch, hoarse and strained-strangled quality, highly defective articulation, marked hypernasality and nasal emission combine to make the speaker struggle to produce short, scarcely intelligible phrases, his enormous effort seemingly inadequate amid a great weakness. Cerebellar disorders (ataxic dysarthria) usually produce one of two patterns of speech deviation, the two seldom appearing concurrently: (1) intermittent disintegration of articulation, together with dysrhythmia and irregularities of pitch and loudness in performing tests of oral diadochokinetic rate; or (2) altered prosody, involving prolongation of sounds, equalization of syllabic stress (by undue stress on usually unstressed words and syllables), and prolongation of intervals between syllables and words. Speech proceeds at an artificially even, measured pace. Parkinsonism (hypokinetic dysarthria) reduces vocal emphasis, peaks and valleys of pitch and variations of loudness being flattened out monotonously. Short rushes of speech are separated by illogically placed pauses, the rate being variable, often accelerated. Consonant articulation in contextual speech and syllable repetition is blurred, as muscles fail to go through their complete excursion. Difficulty in initiating articulation is shown by repetition of initial sounds and inappropriate silences. The voice is often breathy, and the loudness is reduced sometimes almost to inaudibility. An associated nonspeech sign is masking of facies. Dystonia (hyperkinetic dysarthria), through involuntary bodily and facial movements, unpredictably causes voice stoppages, disintegration of articulation, excessive variations of loudness and distortion of vowels. Perhaps in anticipation of these interruptions, normal prosody is altered by slowing of rate, reduction in variations of pitch and loudness, prolongation of inter-word intervals and interposition of inappropriate silences. Choreoathetosis (hyperkinetic dysarthria) causes involuntary movements that alter the normal breathing cycle and result in sudden exhalatory gusts of breath, bursts of loudness, elevations of pitch and disintegration of articulation. The overall loudness level may be increased.
Spasticity or flaccidity
Flaccidity
Muscular spasm
Slowness or weakness
Weakness
Weakness or Flaccidity or small moverigidity ments
B. Voice tremor Strained-strangled voice Harsh voice Low pitch
C. Short phrases Hypernasality
D. Nasal emission Audible inhalation
E. Breathy voice Reduced stress Decay of loudness Inadequate loudness
Multiple
G. Consistent artic. errors Vowel distortions Slow rate Monopitch Inappropriate silences Variable rate
Any, including compensation
Rigidity
+ ++ +
++
++
++
BELLAR ATAXIA
+ ++ + + + ++
+
+
+ + +
ATHETOSIS
CHOREO-
+
~
++ ++
+
+
+ +
+ + +
DYSTONIA
++ + ++ ++
+
+
+ +
+
++ ++ ++
+
BULBAR PALSY
PSEUDO-
"Single plus (+) indicates frequent occurrence of deviation; double plus (++) indicates further prominence
Fast small movements
F. Fast rate Short rushes of speech Repetition of initial sounds
Spasticity or involuntary movements
Ataxia, involuntary movement, or severe weakness
Poor muscular control
A. Sudden artic. breakdown Prolongation of sounds Equalization of stress
SPEECH DEVIATIONS
NEURAL MECHANISM
CERE-
++ ++ ++ + +
+ +
++
++ +
+ ++ ++
++ +
SCLEROSIS
LATERAL
TROPHIC
AMYO-
Relation of Speech Deviations to Certain Neurologic Disorders':'
MUSCULAR MECHANISM
Table 1.
+ + + +
++
++
+ ++
PALSY
BULBAR
++ ++ +
++
+ ++ +
+ ++ ++ ++
SONISM
PARKIN-
0
""
~
~
00 ....
l'j
:»Ul
l'j
Ul
r;'J
n S'
::0 0 t" 0
l'j
Z c::
51
Ul
Z
r;'J
[Jl
...
:r
n
l'j l'j
>tI
[Jl
0 ::0
844
FREDERIC
L.
DARLEY, ARNOLD
E. ARONSON, JOE R. BROWN
Anticipated breakdowns are managed by varying the rate, introducing and prolonging pauses and equalizing stress on all syllables and words.
RECAPITULATION A wide variety of speech deviations can be observed in the dysarthrias. The individual speech deviations result from one or more types of muscular dysfunction, which in turn are reflections of particular neurologic disorders. The accompanying table summarizes these principles. Listed in the first column are many of the individual speech deviations. These are arranged vertically in small groups (A through G), since each group appears to result from a different muscular dysfunction or combination of dysfunctions. The second and third columns list the muscular dysfunction and neural disorder apparently responsible for each group of speech deviations. The remaining columns are headed by specific neurologic syndromes. If one looks, for example, at group A (sudden breakdown of articulation, prolongation of phonemes, excess and equal stress pattern), one notes that it is due to breakdown of coordinate muscular activity as the result of ataxia, involuntary movements or severe muscular weakness. Further to the right, this group may be observed in ataxia, choreoathetosis and dystonia; and one appears in pseudobulbar palsy and two (because of severe spastic-flaccid weakness) in amyotrophic lateral sclerosis. Group F, interestingly, occurs only in parkinsonism; but most of the speech deviations in group G occur, by way of contrast, in a majority of the seven syndromes. By following down anyone of the columns for syndromes one can readily identify the specific speech deviations frequently encountered in anyone neurologic syndrome.
SUMMARY Several neurologic diseases cause alterations of motor speech. As diverse motor systems are affected, the patterns of resultant motor speech errors mirror the neurophysiologic impairment. Individual deviations within the five basic motor speech processes (respiration, phonation, resonance, articulation and prosody) are observed with differential frequency in various diseases. The simultaneous appearance of several deviant factors even more surely suggests which disease is represented. Unique combinations of deviation characterize seven subcategories of dysarthria: spastic, flaccid, combined spastic and flaccid (amyotrophic lateral sclerosis), ataxic, hypo kinetic , and two forms of hyperkinetic (dystonia and choreoathetosis).
REFERENCES 1. Dorland's Illustrated Medical Dictionary. Ed. 24, Philadelphia, W. B. Saunders Company,
1965. 2. Grewel, F.: Classification of dysarthrias. Acta Psychiat Scand 32:325-337,1957. 3. Van Riper, C. G.: Speech Correction: Principles and Methods. Ed. 4, Englewood Cliffs, N.J., Prentice-Hall, Inc., 1963, p. 484.
The alterations of speech and voice which are heard in certain neurologic diseases constitute useful diagnostic signs. Motor speech disorders, collectively known as dysarthria, may have a "localizing value," in the words of Grewel, " ... sometimes even suggesting a tentative diagnosis to the phonetically trained ear, when neurological examination still shows no convincing neurological symptoms." As currently employed in speech pathology and neurology, the term "dysarthria" means something more comprehensive and yet more specific than is implied in the definition offered by Dorland's Illustrated Medical Dictionary: "imperfect articulation in speech." Typically, multiple speech processes are affected simultaneously. Not only the process of articulation but all the other basic motor processes of respiration, phonation, resonance and prosody present distinctive changes that one can learn to recognize. The term is best restricted, however, to speech dysfunctions which are neurogenic. As used here, then, "dysarthria" will refer to the wide variety of impairments of the five basic motor speech processes that manifest disturbances in muscular control over the speech mechanism from damage to the central or peripheral nervous system. These impairments seldom occur in isolation but rather in various combinations, with impaired articulation being a common denominator. So conceived, dysarthria calls for one's listening for much more than simply the traditionally reported "slurred speech." Each basic process may be impaired in a number of ways, so that one learns to observe numerous separable characteristics which individually reveal distinctive alterations in different diseases and together- observed concurrently in a given patient - suggest a specific disease entity.
WHAT TO OBSERVE To make these systematic observations one must sample several types of speech and voice production. A sample of contextual speech Medical Clinics of North America- Va!. 52, No. 4, July, 1968
835
836
FREDERIC
L.
DARLEY, ARNOLD
E.
ARONSON, JOE
R.
BRoWN
can be elicited by having the patient tell about a picture representing a situation, or one may have the patient read a standard paragraph of simple prose containing all the consonants and vowels of English as well as some consonant clusters. ,:. This procedure is preferred to asking the patient to repeat tongue-twisters, which are difficult even for normal speakers and not adequate as samples of normal articulatory performance. For analysis of his phonation, the patient should be asked to prolong the vowel lahl as long, clearly and steadily as possible. Finally, for the purpose of evaluating his oral diadochokinetic rate, he should be asked to repeat as rapidly as possible a bilabial sound, "puh-puh-puh ... ," a sound requiring elevation of the tongue tip, "tuh-tuh-tuh ... ," and a sound requiring elevation of the back of the tongue, "kuh-kuh-kuh.... " The speech and voice so produced can be analyzed in terms of the basic processes as follows. Respiration 1. Is there sufficient breath support for speech, or are phrases short because breath supply is inadequate? 2. Is inhalation audible? 3. Is the inhalation-exhalation cycle smooth, or are there sudden forced gusts of breath? 4. Is exhalation coordinated with the onset of phonation, or is there air wastage?
Phonation PITCH. 1. Is the pitch level appropriate to the patient's age and sex, too low, or too high? 2. Are there appropriate inflectional pitch changes, or is pitch usage monotonous (monopitch)? 3. Are there sudden, uncontrolled pitch breaks? 4. Is there a vocal tremor? LOUDNESS. 1. Is the voice adequately loud? 2. Are there normal variations in loudness? 3. Are there sudden bursts of loudness? 4. Does loudness decay as speech continues? VOICE QUALITY. 1. Is the voice harsh or raspy? 2. Is there audible escape of unused breath (breathiness)? 3. Does the voice sound strained or strangled (as if being effortfully squeezed through the glottis)? 4. Are there sudden stoppages of voice?
"Such a passage is "My Grandfather," reproduced (with slight alterations) from Van Riper: You wished to know all about my grandfather. Well, he is nearly 93 years old yet he still thinks as swiftly as ever; he dresses himself in an ancient black frock coat, usually minus several butto1'ls. A long, flowing beard clings to his chin, giving those who observe him a pronounced feeling of the utmost respect. When he speaks, his voice is just a bit cracked and quivers a trifle. Twice each day he plays skillfully and with zest upon our small organ. Except in the winter when the ooze or snow or ice prevents, he slowly takes a short walk in the open air each day. We have often urged him to walk more and smoke less, but he always answers, "Banana oil!" Grandfather likes to be modern in his language.
MOTOR SPEECH SIGNS IN NEUROLOGIC DISEASE
837
Resonance 1. Is there hypernasality? 2. Is there nasal emission of air during speech? 3. Do hypernasality and nasal emission increase as speech continues? 4. Is there hyponasality? Articulation 1. Are consonant sounds precisely produced, or are they slighted or run together? 2. Is there clumsiness in going from one consonant to another? 3. Are consonant inaccuracies consistent, or is there irregular, unsystematic disintegration of articulation? 4. Are vowels distorted so that their identity is lost? 5. Are sounds unduly prolonged? 6. Are sounds repeated? Prosody 1. Is rate of speech abnormally slow or rapid? 2. Is speech made up of short rushes separated by pauses? 3. Are there inappropriate silences? 4. Are inter-word and inter-syllable intervals prolonged? 5. Is emphasis on key words and stressed syllables reduced? 6. Is there excessive stress on usually unstressed syllables and words? Additional Signs In addition to these auditory aspects of speech, one should be attentive to associated visual cues. 1. Is there tremor of the head? 2. Is there myoclonus of facial, palatal and possibly laryngeal muscles? 3. Are there other involuntary movements of face or body? 4. Are facies masked? 5. Are tongue movements in all directions rapid and smooth, or sluggish? 6. Is there fasciculation of the tongue? 7. Is there atrophy of the borders of the tongue? 8. Is there a sucking reflex? 9. Is the jaw jerk increased? 10. Is palate elevation adequate? 11. Is contraction of the alae of the nose or facial grimacing noticeable during speech? 12. Are accessory respiratory muscles used? SPECIFIC SPEECH DEVIATIONS The relationship of the above-listed speech signs to various neurologic diseases has been determined through detailed analysis of
838
FREDERIC
L. DARLEY, ARNOLD E. ARONSON, JOE R. BRoWN
speech samples. These were taken from patients assigned by unequivocal diagnosis to one of seven categories of motor impairment, and numbering 30 or more in each such group: pseudobulbar palsy (bilateral upper motor neuron lesion), bulbar palsy (lower motor neuron lesion), amyotrophic lateral sclerosis (both upper and lower motor neuron lesions), cerebellar lesions, parkinsonism, choreoathetosis and dystonia. Although the diagnostic significance of some speech deviations, especially the mild ones, is often not clear-cut, the relative frequency of occurrence of many speech signs is uniquely different in the various diagnostic groups. On hearing a given deviation, therefore, one may hypothesize that it is caused by a given type of impairment. Which diagnostic entity is the most likely to be associated with each of several specific speech deviations? RESPIRATION. Adequate breath support for speech requires smooth, controlled exhalation of reasonable duration and of sufficient pressure to create the necessary amplitude of vocal-fold vibration. There are three reasons for inadequacy of breath support: (1) respiratory musculature is weak; (2) peripheral resistance to the exhaled breath column at the larynx or the velopharyngeal port is decreased, allowing air wastage; and (3) peripheral resistance is excessive-too great for normal respiratory muscles to overcome. The second reason applies in bulbar palsies involving the tenth cranial nerve. There is often breathy voice with marked air wastage at the glottis with resulting shortening of phrases. Audible inhalation is most suggestive of bulbar involvement (bulbar palsy, amyotrophic lateral sclerosis), the vocal folds being incompletely abducted. The third reason applies in patients with upper motor neuron lesions (pseudobulbar palsy, amyotrophic lateral sclerosis). Shortening of phrases is typical here too. An effortful grunt at the ends of phrases is sometimes associated with exhaustion of breath supply. The hyperkinetic movement disorders, especially athetosis and chorea, are the most likely causes of interference with smooth cycling. Some patients (especially choreics) speak with irregular forced gusts of breath, while others (especially athetoids) display imperfect timing of their exhalations to coincide with onset of phonation, or vice versa. Also patients with hyperkinetic disorders may be noticeable for shortening of phrases as exhalation is interrupted. PHONATION. Because it occurs in many patients among all of the disease categories, monopitch is not a particularly useful sign; but it is markedly more prominent in parkinsonism than in the other groups, as is monotony of loudness. Just as paucity of bodily movement is characteristic of parkinsonism, so is paucity of vocal variation. Inadequate loudness and decay of loudness as speech proceeds are also more frequently heard in parkinsonism than in the other categories. Excessive loudness variations, on the other hand, are most often heard in choreoathetosis and dystonia. Though frequently noted in myxedema, excessively low pitch is most characteristic of patients with spasticity (pseudobulbar palsy, amyotrophic lateral sclerosis). In patients with spasticity low pitch is
MOTOR SPEECH SIGNS IN NEUROLOGIC DISEASE
839
commonly associated with harsh voice quality, a strained, strangled sound as though air were being effortfully squeezed through the glottis, and pitch breaks. Sudden voice stoppages are also heard in pseudobulbar palsy, but they occur even more frequently in patients with dystonia, who experience unpredictable spasmodic blockings of laryngeal and oral acti vity. All of these phonatory phenomena may be apparent in contextual speech but are made even more evident when the patient is asked to prolong the vowel lah/. Often voice tremor is associated with the other manifestations of hereditary essential tremor. However, it is frequently seen in patients with dystonic and spastic syndromes. The strongest indication from continuously breathy voice is bulbar palsy, the vocal folds being incompletely adducted during phonation. The voices of many patients with parkinsonism are also consistently breathy, though usually to a less severe degree than in bulbar palsy. RESONANCE. Hypernasality bespeaks velopharyngeal incompetence, represented in the layman's stereotype of "cleft-palate speech." Velopharyngeal mechanisms which are intact structurally but inadequately innervated similarly allow excessive nasal resonance and the nasal emission of the phonated and articulated air stream. Pronounced hypernasality and nasal emission most often suggest bulbar palsy, in which paresis of the soft palate prevents attainment of the critical limits of closure. Hypernasality is not uncommon in pseudobulbar palsy as well, the muscles of the velopharyngeal port moving too slowly in rapid contextual speech to effect firm closure; but the degree of hypernasality is typically less than in bulbar palsy, and nasal emission is not heard. Hypernasality is often a presenting symptom in myasthenia gravis. Marked increase in hypernasality (together with deterioration of articulation) as a patient speaks or reads aloud at length is highly suggestive of myasthenia gravis. Evidence of fatigue with prolongation of effort may be more readily elicited in some myasthenic patients by a more restricted muscular task such as repeating lahl once per second for several minutes. On the other hand, hyponasality is not an expected sign of any neurologic disease. If one hears the nasal consonants Iml, 1nl and Ingl altered to resemble Ibl, Idl and Igl, one should suspect that normal nasal resonance is prevented by occlusion of the nasal pathway by hypertrophied adenoids, a deviated septum, rhinitis or nasopharyngeal tumor. ARTICULATION. In itself, imprecise production of consonants is not suggestive of any certain diagnostic category, since all of the groups studied had articulatory troubles of some kind. There are, however, variations in the type of faulty production from disorder to disorder. Fairly consistent articulatory errors are the rule in spasticity, flaccidity and the hypokinesis of parkinsonism - that is, errors of the same kinds recur. In spasticity the tongue and lips move sluggishly, so that sounds are slighted and elided and sequences of adjacent consonants (as in swiftly) are produced clumsily. In the bulbar palsies involving the twelfth cranial nerve, the tongue lies flaccid in the floor
840
FREDERIC
L. DARLEY, ARNOLD E. ARONSON, JOE R. BROWN
of the mouth, so that special difficulty is heard in the production of the vowels leel and Ii/ (as in seat and sit), and the consonants Itl, Idl, Ill, Isl and Ishl, all of which require elevation of the tip of the tongue. When the seventh cranial nerve is involved, lip movements are reduced, so that production of the vowels and bilabial consonants is impaired. The parkinsonian patient fails to move his articulators through the full excursion necessary for crisp consonants, so that all his sounds are likely to be blurred and fragmentary. In contrast to the performance observed in those groups, the ataxic articulation of the patient with a cerebellar disorder and the hyperkinetic problems of the patient with chorea or athetosis or dystonia are less consistent. In cerebellar disorders one may hear a generally good to fair performance in articulation punctuated irregularly by sudden breakdowns in accuracy, the disintegration due to momentary loss of coordination, sometimes involving a single sound, more likely a syllable, but often a group of syllables whose identity becomes lost. Adventitious movements cause similar unpredictable distortion of sounds in the hyperkinesias. Consonants usually suffer most in the dilapidated articulation of neurologic diseases, vowels usually remaining surprisingly intact except in advanced amyotrophic lateral sclerosis and in other cases of such extreme loss of motor power that they can be termed "anarthria." Not uncommon, however, in facial, tongue and oropharyngeal dystonia and in choreoathetosis is a marked distortion of vowels due to changes in mouth postures during speech. Some vowel distortion may be heard also in the articulatory disintegration of cerebellar disorders and, as mentioned above, in severe lingual and labial paresis of bulbar palsy. Parkinsonism, almost exclusively, is associated with repetition of initial sounds of words. This error suggests the occurrence of speech arrests analogous to the motor arrests observed in walking. Unusual prolongation of sounds is most frequently found in cerebellar disorders, where the timing of movements is faulty; however, one is likely to hear prolongation of speech sounds in the hyperkinetic disorders and indeed in any patient whose rate of speech is substantially slowed, as discussed below. Related to these articulatory inefficiencies observed in contextual speech is the performance on tests of the oral diadochokinetic rate (repetition of "puh," "tuh" and "kuh"). In spastic states the repetition is slow but rhythmical, and precision of articulation is reduced. In flaccid conditions rate may be slowed and precision of "tuh" and "kuh" particularly poor because of specific difficulty with tongue elevation, or on "puh" because of weakness of the lips. Parkinsonian patients move their articulators rapidly through a very narrow range of motion; therefore the identity of the separate pulses may be almost lost. In ataxia and hyperkinesia the rates may be normal or somewhat slow, but typically they are characterized by dysrhythmia and irregularities of pitch and loudness. PROSODY. In all the neurologic categories except parkinsonism, many of the patients speak at a slow rate. Most extreme slowness of
MOTOR SPEECH SIGNS IN NEUROLOGIC DISEASE
841
speech is observed in amyotrophic lateral sclerosis and pseudobulbar palsy. In parkinsonism patients sometimes, though not always, display fast rate. Occasionally one hears an increase in rate as speech proceeds; this phenomenon, analogous to festination in gait, is probably not as common as textbooks suggest. More typical-and indeed pathognomonic of parkinsonian speech-are short rushes of speech separated by pauses at points often not logically prescribed by the meaning. Variable rate, alternating between slow and fast, is often noted in parkinsonism, but it is even more prominent in choreoathetosis. Inappropriate silences occur more often in parkinsonism than in any other disorder, but they are frequent in the speech of choreoathetosis and dystonia. Two opposite kinds of alteration in normal vocal emphasis distinguish the neurologic groups. General reduction of stress on key words and accented syllables is most typical of parkinsonism, with lesser degrees observable in pseudobulbar palsy and amyotrophic lateral sclerosis. An equalization of stress of quite another kind is heard frequently in cerebellar disorders and the hyperkinesias: syllables and words usually unstressed are stressed equally with those usually stressed; the intervals between syllables are somewhat prolonged; and thus speech proceeds at a measured, artificially even pace. This is the "scanning speech" described by Charcot in 1877 as pathognomonic of advanced cases of multiple sclerosis. Its frequent appearance in ataxic patients, and in some patients with movement disorders as well, suggests that it may be a compensatory mechanism, an attempt by the patients to guard against the disintegrations and interruptions of voice and articulation that beset them.
DISTINCTIVE PATTERNS OF DYSARTHRIA Detection of the above-described individual speech deviations can suggest to the clinician the categories of neurologic disease in which these deviations have been found most often. His assurance in so pigeonholing them increases significantly as he finds a number of related deviations occurring simultaneously in a given patient. One may hear in one case a cluster of four or five characteristic speech errors, all known to be found to some degree in disorders of a certain type, and thus more safely expect appropriate search to reveal such an entity. Seven of these frequently appearing patterns are presented. Pseudobulbar palsy (spastic dysarthria) typically makes speech slow and labored, the articulation being rather consistently imprecise, especially on more complicated groups of consonant sounds. Pitch is low and monotonous. Voice quality is harsh and often strained or strangledsounding. There may be considerable hypernasality, but usually no nasal emission is audible. Associated nonspeech signs are increase of deep tendon reflexes, appearance of the sucking reflex, increased jaw jerk, sluggish tongue movements and activity of accessory respiratory musculature. Bulbar palsy (flaccid dysarthria) produces hypernasality with asso-
842
FREDERIC
L. DARLEY, ARNOLD E. ARONSON, jOE R. BROWN
ciated nasal emission of air during speech as its most prominent speech symptom. Inhalation is often audible and exhalation is often breathy, air wastage being manifested also in shortness of phrases. Articulation is often imprecise on either or both of two bases: (1) consonants may be weak through failure to impound sufficient intraoral breath pressure because of velopharyngeal incompetence; (2) immobility of tongue and lips because impairment of the hypoglossal and facial nerves prevents normal production of vowels and consonants. Associated nonspeech signs are fasciculation and atrophy of the tongue, reduced rate of alternating motion of tongue and lips, poor elevation of the soft palate and nasal alar contraction and grimacing as the patient tries to compensate for velopharyngeal incompetence. Amyotrophic lateral sclerosis (combined spastic and flaccid dysarthria) has a developing effect on speech. In an earlier stage either spastic or flaccid speech and nonspeech signs predominate; in an advanced stage both sets of features described above are present. Slow rate, low pitch, hoarse and strained-strangled quality, highly defective articulation, marked hypernasality and nasal emission combine to make the speaker struggle to produce short, scarcely intelligible phrases, his enormous effort seemingly inadequate amid a great weakness. Cerebellar disorders (ataxic dysarthria) usually produce one of two patterns of speech deviation, the two seldom appearing concurrently: (1) intermittent disintegration of articulation, together with dysrhythmia and irregularities of pitch and loudness in performing tests of oral diadochokinetic rate; or (2) altered prosody, involving prolongation of sounds, equalization of syllabic stress (by undue stress on usually unstressed words and syllables), and prolongation of intervals between syllables and words. Speech proceeds at an artificially even, measured pace. Parkinsonism (hypokinetic dysarthria) reduces vocal emphasis, peaks and valleys of pitch and variations of loudness being flattened out monotonously. Short rushes of speech are separated by illogically placed pauses, the rate being variable, often accelerated. Consonant articulation in contextual speech and syllable repetition is blurred, as muscles fail to go through their complete excursion. Difficulty in initiating articulation is shown by repetition of initial sounds and inappropriate silences. The voice is often breathy, and the loudness is reduced sometimes almost to inaudibility. An associated nonspeech sign is masking of facies. Dystonia (hyperkinetic dysarthria), through involuntary bodily and facial movements, unpredictably causes voice stoppages, disintegration of articulation, excessive variations of loudness and distortion of vowels. Perhaps in anticipation of these interruptions, normal prosody is altered by slowing of rate, reduction in variations of pitch and loudness, prolongation of inter-word intervals and interposition of inappropriate silences. Choreoathetosis (hyperkinetic dysarthria) causes involuntary movements that alter the normal breathing cycle and result in sudden exhalatory gusts of breath, bursts of loudness, elevations of pitch and disintegration of articulation. The overall loudness level may be increased.
Spasticity or flaccidity
Flaccidity
Muscular spasm
Slowness or weakness
Weakness
Weakness or Flaccidity or small moverigidity ments
B. Voice tremor Strained-strangled voice Harsh voice Low pitch
C. Short phrases Hypernasality
D. Nasal emission Audible inhalation
E. Breathy voice Reduced stress Decay of loudness Inadequate loudness
Multiple
G. Consistent artic. errors Vowel distortions Slow rate Monopitch Inappropriate silences Variable rate
Any, including compensation
Rigidity
+ ++ +
++
++
++
BELLAR ATAXIA
+ ++ + + + ++
+
+
+ + +
ATHETOSIS
CHOREO-
+
~
++ ++
+
+
+ +
+ + +
DYSTONIA
++ + ++ ++
+
+
+ +
+
++ ++ ++
+
BULBAR PALSY
PSEUDO-
"Single plus (+) indicates frequent occurrence of deviation; double plus (++) indicates further prominence
Fast small movements
F. Fast rate Short rushes of speech Repetition of initial sounds
Spasticity or involuntary movements
Ataxia, involuntary movement, or severe weakness
Poor muscular control
A. Sudden artic. breakdown Prolongation of sounds Equalization of stress
SPEECH DEVIATIONS
NEURAL MECHANISM
CERE-
++ ++ ++ + +
+ +
++
++ +
+ ++ ++
++ +
SCLEROSIS
LATERAL
TROPHIC
AMYO-
Relation of Speech Deviations to Certain Neurologic Disorders':'
MUSCULAR MECHANISM
Table 1.
+ + + +
++
++
+ ++
PALSY
BULBAR
++ ++ +
++
+ ++ +
+ ++ ++ ++
SONISM
PARKIN-
0
""
~
~
00 ....
l'j
:»Ul
l'j
Ul
r;'J
n S'
::0 0 t" 0
l'j
Z c::
51
Ul
Z
r;'J
[Jl
...
:r
n
l'j l'j
>tI
[Jl
0 ::0
844
FREDERIC
L.
DARLEY, ARNOLD
E. ARONSON, JOE R. BROWN
Anticipated breakdowns are managed by varying the rate, introducing and prolonging pauses and equalizing stress on all syllables and words.
RECAPITULATION A wide variety of speech deviations can be observed in the dysarthrias. The individual speech deviations result from one or more types of muscular dysfunction, which in turn are reflections of particular neurologic disorders. The accompanying table summarizes these principles. Listed in the first column are many of the individual speech deviations. These are arranged vertically in small groups (A through G), since each group appears to result from a different muscular dysfunction or combination of dysfunctions. The second and third columns list the muscular dysfunction and neural disorder apparently responsible for each group of speech deviations. The remaining columns are headed by specific neurologic syndromes. If one looks, for example, at group A (sudden breakdown of articulation, prolongation of phonemes, excess and equal stress pattern), one notes that it is due to breakdown of coordinate muscular activity as the result of ataxia, involuntary movements or severe muscular weakness. Further to the right, this group may be observed in ataxia, choreoathetosis and dystonia; and one appears in pseudobulbar palsy and two (because of severe spastic-flaccid weakness) in amyotrophic lateral sclerosis. Group F, interestingly, occurs only in parkinsonism; but most of the speech deviations in group G occur, by way of contrast, in a majority of the seven syndromes. By following down anyone of the columns for syndromes one can readily identify the specific speech deviations frequently encountered in anyone neurologic syndrome.
SUMMARY Several neurologic diseases cause alterations of motor speech. As diverse motor systems are affected, the patterns of resultant motor speech errors mirror the neurophysiologic impairment. Individual deviations within the five basic motor speech processes (respiration, phonation, resonance, articulation and prosody) are observed with differential frequency in various diseases. The simultaneous appearance of several deviant factors even more surely suggests which disease is represented. Unique combinations of deviation characterize seven subcategories of dysarthria: spastic, flaccid, combined spastic and flaccid (amyotrophic lateral sclerosis), ataxic, hypo kinetic , and two forms of hyperkinetic (dystonia and choreoathetosis).
REFERENCES 1. Dorland's Illustrated Medical Dictionary. Ed. 24, Philadelphia, W. B. Saunders Company,
1965. 2. Grewel, F.: Classification of dysarthrias. Acta Psychiat Scand 32:325-337,1957. 3. Van Riper, C. G.: Speech Correction: Principles and Methods. Ed. 4, Englewood Cliffs, N.J., Prentice-Hall, Inc., 1963, p. 484.