Sounds are produced by expired air passing through the vocal cords. Properly articulated speech requires coordination between the respiratory muscles and the muscles of the larynx, pharynx, soft palate, tongue, and lips. All these components are referred to as the vocal (oral) tract. Respiratory movements determine the strength and rhythm of the voice. Variations in pitch are produced by alterations in the tension and length of the vocal cords and the rate and character of the vibrations transmitted to the column of air that passes between them. Modifications in sound are produced by changes in the size and shape of the glottis, pharynx, and mouth, and by changes in the position of the tongue, soft palate, and lips. The oropharynx, nasopharynx, and mouth act as resonating chambers and further influence the timbre and character of the voice. Speech may be possible in the absence of vocal cords, and whispered speech may be possible in inspiration as well as expiration. An electrolarynx produces electromechanical vibrations in the oral tract that are then articulated into speech. Whispered sounds are also entirely articulatory.

Articulation is one of the vital bulbar functions. Several cranial nerves are involved in speech production, and an adequate appraisal of speech requires evaluating the function of each. The trigeminal nerves control the muscles of mastication and open and close the mouth. The facial nerves control the muscles of facial expression, especially the branches to the orbicularis oris and other smaller muscles about the mouth that control lip movement. The vagus nerves and glossopharyngeal nerves control the soft palate, pharynx, and larynx, and the hypoglossal nerves control tongue movements. The upper cervical nerves, which communicate with the lower cranial nerves and in part supply the infrahyoid and suprahyoid muscles, the cervical sympathetic nerves that contribute to the pharyngeal plexus, and the phrenic and intercostal nerves also contribute to normal speech.

Voiced sounds are produced by narrowing the glottis so that the vocal cords are approximated. Voiceless sounds are made with the glottis open. Either type of sound may be modulated by adjusting the size and shape of the vocal cavities. Vowels are largely of laryngeal origin, but are modified by the resonance of the vocal cavities. Certain vowel sounds such as i, a, and y are modified by the soft palate. Consonants may be either voiced or voiceless; they are enunciated by constriction or closure at one or more points along the vocal tract. A fricative is a sound articulated through a not quite closed glottis that creates turbulence in the airflow causing a frictional rustling of the breath, e.g., f, soft s.

Speech sounds may be placed in different categories related to the place of articulation, e.g., labiodental, interdental, alveolar, palatal, alveopalatal, velar, and uvular. From an anatomic and neurologic viewpoint it is more important to recognize how various sounds are produced. Articulated labials (b, p, m, and w) are formed principally by the lips. Modified labials (o and u, and to a lesser extent i, e, and a) are altered by lip contraction. Labiodentals (f and v) are formed by placing the teeth against the lower lip. Linguals are sounds formed with tongue action. T, d, l, r, and n are tongue-point, or alveolar, sounds, formed by touching the tip of the tongue to the upper alveolar ridge. S, z, sh, zh, ch, and j are dentals, or tongue-blade sounds. To hear distorted linguals, place the tip of your tongue against the back of your bottom teeth, hold it there and say “top dog,” “go jump,” and “train.” To hear distorted labials, hold your upper lip between the thumb and forefinger of one hand and your bottom lip similarly with the other and say “my baby.” Gutturals (velars, or tongue-back sounds such as k, g, and ng) are articulated between the back of the tongue and the soft palate. Palatals (German ch and g, and the French gn) are formed when the dorsum of the tongue approximates the hard palate.

Normal articulation depends on proper function and neuromuscular control of the vocal tract. Normal development of the tongue, larynx, and soft palate, and adequate hearing are essential to proper pronunciation. The cultural and emotional background of the individual are also important
in appraising speech. No two individuals possess the same speech patterns. This is true not only for pitch and timbre, but also for the quality, duration, and intensity of tones and sounds, and for the ability to pronounce certain words and syllables. Normal variations in enunciation and articulation result from regional variations in speech patterns (“accents”) evident in the pronunciation of vowels and many of the consonants. Education and training are important factors. The uneducated, illiterate, and mentally deficient may mispronounce letters and syllables despite normal powers of articulation. Some individuals are never able to make certain sounds. Those who learned another language before English may never master the pronunciation of certain English sounds. Adult native English speakers may never be able to accurately pronounce some of the guttural and palatal sounds that are part of some languages.

Examination of articulation begins with noting the patient’s spontaneous speech in normal conversation, usually during taking of the history. The accuracy of pronunciation, rate of speech, resonance, and prosody (variations in pitch, rhythm, and stress of pronunciation) are noted. Abnormalities of articulation include tremulousness, stuttering, slurring or sliding of letters or words, scanning, explosiveness, and difficulties with specific sound formations. Some difficult to enunciate phrases have been traditionally used to test articulation. These require the pronunciation of labials, linguals, and, to a lesser extent, velars. The nonsense phrase “puhtuhkuh” or “pataka” tests all three: labials (puh/pa), linguals (tuh/ta), and velars (kuh/ka). Traditional phrases have been selected to test primarily the labials and linguals, such letters as l, r, b, p, t, and d. As the patient repeats these phrases, various aspects of the dysarthria may become more evident. These phrases are time-honored, perhaps above their actual value, and are to a certain extent colloquial. Nonetheless, they are often useful. Pronouncing r’s requires a facile tongue, and many of the test phrases are loaded with this letter. The best test words and phrases have the significant consonants and vowels placed in the initial, middle, and final positions. Commonly used words and phrases include: third riding artillery brigade, Methodist Episcopal, West Register Street, liquid electricity, truly rural, voluntary retribution, baby hippopotamus, and irretrievable ball. Phrases such as “my baby ate a cupcake on the train” contain all the pertinent elements.

Have the patient repeat a syllable such as “puh” over and over as rapidly as possible. Normally the syllable can be pronounced accurately at a rate of 5-7 Hz. Similarly for “tuh” and “kuh.” Listen for abnormally slow or rapid repetition, regularity and evenness, uniform loudness, or tremulousness.

Weakness and fatigueability of articulation, such as might occur in myasthenia gravis, may be brought out by having the patient count to 100 at about one number per second, enunciating each number clearly. Listen for the voice to become hoarse, hypernasal, slurred, or breathy. Disturbances of laryngeal function and of speech rhythm may be elicited by having the patient attempt prolonged phonation, such as by singing and holding a high “a” or “e” or “ah” sound. Assess loudness, pitch, quality (hoarseness, breathiness), steadiness, nasality, and duration. The voice may break, waver, or flutter excessively, particularly when there is cerebellar dysfunction. Note whether the pitch of the voice is appropriate for the patient’s age and sex.

Normal coughing requires normal vocal cord movement. A normal cough indicates that vocal cord innervation is intact. Dysphonia with a normal cough suggests laryngeal disease or a nonorganic speech disturbance. The glottal coup (glottic click, coup de glotte) is the sharp sound at the beginning of a cough. The intensity of the glottic click reflects the power of vocal cord adduction. The glottic click may also be elicited by asking the patient to say “oh-oh,” or make a sharp, forceful grunting sound. A cough without a glottal coup (bovine cough) suggests vocal cord palsy.

Resonance is an important voice quality. Normal resonance depends on an adequate seal between the oropharynx and nasopharynx (velopharyngeal competence). When palatal weakness causes an inadequate seal on pronouncing sounds that require high oral pressure, the voice has a “nasal” quality. An audible nasal emission is nasal air escape that causes a snorting sound.
Hypernasality is more noticeable when the head is tipped forward; it is less evident when the patient lies with his head back, because the weakened soft palate falls back by its own weight and closes off the nasopharynx. Velopharyngeal incompetence is common in patients with cleft palate.

Lesions of the nervous system may cause various abnormalities of sound production and word formulation (Table 6.1). Laryngeal disorders may alter the volume, quality, or pitch of the voice (dysphonia). Laryngitis causes dysphonia. Aphonia is complete voice loss. A central or peripheral disturbance of the innervation of the articulatory muscles may cause dysarthria. Lesions may involve the peripheral nerves, brainstem nuclei, or the central corticobulbar, extrapyramidal, or cerebellar pathways. Anarthria is a total inability to articulate because of a defect in the control of the peripheral speech musculature.

Lesions of the cerebral centers and connections that subserve language function may cause aphasia, an abnormality of language, even though the articulation mechanisms may be intact. Mutism is a total inability to speak; usually the patient appears to make no attempt to speak or make sounds. Mutism is usually of psychogenic origin if present in an apparently otherwise normal patient, but may occur with lesions of the cerebrum, brainstem, and cerebellum (especially in children).

Abnormalities of articulation may be caused by many different pathologic conditions. Disturbances in the respiratory rhythm interfere with speech, and respiratory muscle weakness causes a feeble voice with abnormalities in regularity and rhythm. Laryngeal disease may cause severe speech impairment, but whispered speech may still be possible. In children, articulation disturbances may be developmental and are often temporary. Structural abnormalities of the vocal tract, such as congenital craniofacial defects (cleft palate, cleft lip), ankyloglossia (abnormal shortness of the frenulum of the tongue; “tongue-tie”), adenoidal hypertrophy, vocal cord edema or nodules, nasal obstruction, or perforated nasal septum may cause abnormalities in sound production. The importance of the teeth in articulation is apparent in the speech of edentulous patients.

Neurologic disturbances of articulation may be caused by primary muscle diseases affecting the tongue, larynx, and pharynx; neuromuscular junction disorders; lower motor neuron disease involving either the cranial nerve nuclei or the peripheral nerves that supply the muscles of articulation; cerebellar dysfunction, basal ganglia disease, or disturbances of the upper motor neuron control of vocalization. Lesions of the hypoglossal nerve or nucleus, or local disorders of the tongue such as ankyloglossia, may cause impairment of all enunciation, but with special difficulty pronouncing lingual sounds. The speech is lisping in character and is clumsy and indistinct. Paralysis of the laryngeal musculature causes hoarseness, and the patient may not be able to speak above a whisper; there is particular difficulty pronouncing vowels. Similar changes occur in laryngitis and in tumors of the larynx. With unilateral laryngeal muscle weakness, such as in recurrent laryngeal nerve lesions, the voice is usually low-pitched and hoarse, but occasionally severe unilateral vocal cord weakness may be present without much effect on speech because the normal vocal cord is able to adduct across the midline and approximate the abnormal cord. Hoarseness due to slight vocal cord weakness may be brought out by having the patient talk with the head turned to one side. With paralysis of the cricothyroid, the voice is hoarse and deep and fatigues quickly. In bilateral abductor paralysis, speech is moderately affected, but in bilateral total paralysis it is lost.

Paralysis limited to the pharynx causes little detectable impairment of articulation. Weakness of the soft palate results in nasal speech, caused by inability to seal off the nasal from the oral cavity. Voice sounds have an added abnormal resonance. There is special difficulty with the velar sounds, but labials and linguals are also affected, as much of the air necessary for their production escapes through the nose. The speech resembles that of a patient with a cleft palate. Characteristically, b becomes m, d becomes n, and k becomes ng. Amyotrophic lateral sclerosis and myasthenia gravis are common causes of this type of speech difficulty.

Seventh nerve paralysis causes difficulty in pronouncing labials and labiodentals. Dysarthria is noticeable only in peripheral facial palsy; the facial weakness in the central type of facial palsy is usually too mild to interfere with articulation. Bell palsy occasionally causes marked dysarthria because of inability to close the mouth, purse the lips, and distend the cheeks. Similar articulatory defects are found in myopathies involving the labial muscles (e.g., facioscapulohumeral or oculopharyngeal dystrophy), in cleft lip, and with wounds of the lips. There is little impairment of articulation in trigeminal nerve lesions unless the involvement is bilateral; in such cases there are usually other characteristics of bulbar speech. Trismus may affect speech because the patient is unable to open the mouth normally.

Lower motor neuron disorders causing difficulty in articulation may occur in cranial neuropathies. Lesions of the ninth and eleventh nerves usually do not affect articulation. A unilateral lesion of CN X causes hypernasality. Lesions involving the vagus bilaterally distal to the origin of the superior laryngeal nerve may leave the vocal cords paralyzed in adduction, resulting in a weak voice with stridor. With more proximal lesions, there is no stridor but the voice and cough are weak.

Neuromuscular disorders, particularly neuromuscular junction disorders, often interfere with speech. In myasthenia gravis (MG), prolonged speaking, such as counting, may cause progressive weakness of the voice with a decrease in volume and at times the development of a bulbar or nasal quality, which may even proceed to anarthria. As the voice fatigues, the speech of a patient with
bulbar myasthenia may be reduced to an incoherent whisper. An occasional myasthenic patient must hold the jaw closed with the hand in order to enunciate.

In progressive bulbar palsy, dysarthria results from weakness of the tongue, pharynx, larynx, soft palate, and, to a lesser extent, the facial muscles, lips, and muscles of mastication. Both articulation and phonation may be affected; speech is slow and hesitant with failure of correct enunciation, and all sounds and syllables may be indistinct. The patient talks as though his mouth were full of mashed potatoes. Supranuclear lesions involving the corticobulbar pathways may also cause dysarthria. Unilateral cortical lesions do not usually affect speech unless they are in the dominant hemisphere and cause aphasia. Occasionally some dysarthria accompanies aphasia. Rarely, lesions in the cortical motor areas for articulation may cause severe dysarthria without aphasia. Both dysarthria and dysprosody, or a defect in rhythm, melody, and pitch, have been described with localized frontal lobe lesions; these may be due to an apraxia of speech.

Bilateral supranuclear lesions involving the cortex, corona radiata, internal capsule, cerebral peduncles, pons, or upper medulla may cause pseudobulbar palsy with spastic dysarthria. The muscles which govern articulation are both weak and spastic. Phonation is typically strained-strangled, and articulation and diadochokinesis are slow.

Lesions of the basal ganglia may affect speech. Athetotic grimaces of the face and tongue may interfere with speech. Irregular spasmodic contractions of the diaphragm and other respiratory muscles, together with spasms of the tongue and pharynx, may give the speech a curious jerky and groaning character. In addition, there may be a pseudobulbar element with slurred, indistinct, spastic speech. When chorea is present, the violent movements of the face, tongue, and respiratory muscles may make the speech jerky, irregular, and hesitant. The patient may be unable to maintain phonation and occasionally there is loss of the ability to speak.

Speech in parkinsonism is often mumbled, hesitant, rapid, and soft (hypophonic). There may sometimes be bradylalia, with feeble, slow, slurred speech because of muscular rigidity and immobility of the lips and tongue. There is dysprosody and the speech lacks inflections, accents, and modulation. The patient speaks in a monotone, and the words are slurred and run into one another. The voice becomes increasingly weak as the patient talks, and he may become unable to speak above a whisper; as the speech becomes more indistinct it may become inaudible or practically disappear. Words may be chopped off. There may be sudden blocks and hesitations, or speech may stop abruptly. There may be pathologic repetition of syllables, words, or phrases (palilalia). Like the parkinsonian gait, the speech may show festination, with a tendency to hurry toward the end of sentences or long words.