Within the field of communication sciences and disorders, we think of communication as broadly
comprised of speech and language. Speech gener- ally refers to aspects of communication that involve motor output for production of speech sounds.
Production of speech sounds requires functional input from respiratory, phonatory, and articula- tory systems (Table 4.1). Language generally refers to the process by which we both encode and pro- cess meaning within messages, and is divided into three primary components: form, content, and use.
These components can be further subdivided based on five key aspects of language—specifically, phonology, morphology, syntax, semantics, and pragmatics.
Speech Components
As noted previously, production of speech requires input from respiratory, phonatory, and articulatory sys- tems. An airstream is generated by the lungs, passes through the vocal cords, and is then shaped by the articulators to form speech sounds. Impairments in any of these systems most likely will have a signifi- cant impact on speech production.
Respiration
The respiratory system is composed of the upper and the lower airways. The upper airway consists of the nose, mouth, pharynx, and larynx, and the lower airway consists of the tracheobronchial tree and the lungs (2).
Upper Airway. The upper airway has many functions.
The mucous membranes covering much of the upper airway structures are softer, looser, and more fragile in infants and young children than in older children and adults, and more susceptible to edema and injury from trauma.
Nose. All children are obligate nasal breathers during the first six months of life, during which time the soft palate is in close anatomic approximation with the epi- glottis. This factor, combined with the relatively large size of the tongue relative to the oral cavity at this age, renders nasal patency essential for maintaining an air- way. Those children with nasal obstructions such as choanal atresia are at risk for respiratory compromise (cyanosis) during feeding.
Mouth. The lips, mandible, maxilla, cheeks, teeth, tongue, and palate are the most important compo- nents of the oral cavity with regard to manipulation of airflow for respiration and speech production. The infant tongue takes up a larger area in the mouth and rests more anteriorly in the oral cavity than that of the adult. There are numerous congenital cranio- facial anomalies, often associated with syndromes, that have an adverse impact on airflow. Some anom- alies, such as cleft palate, prevent sufficient valving of the airstream, resulting in inaccurate production of speech sounds. Other anomalies, such as glossop- tosis (oropharyngeal or hypopharyngeal obstruction during feeding caused by tongue retraction, and common in Pierre Robin Sequence), can result in blockage of the airstream and subsequent respira- tory distress.
Pharynx. The pharynx, a muscular tube shared by the respiratory and digestive tracts, is sometimes referred to as the aerodigestive tract, and serves vital functions for both respiration and swallowing. It is divided into three portions: the nasopharynx, oro- pharynx, and the hypopharynx. The pharynx in an infant is gently curved, and as the child grows and develops, the angle increases to approximately 90 degrees.
The nasopharynx is the portion of the pharynx directly behind the nasal cavity, extending from the roof of the nasal cavity to the roof of the mouth. In addition to conducting air, the nasopharynx acts as a resonator for voice. The Eustachian tubes from the middle ear open into the nasopharynx.
The oropharynx is that portion of the pharynx directly behind the oral cavity, extending from the roof of the mouth (pharyngeal aspect of the soft palate) down to the base of the tongue, at the level of the tip of the epiglottis. Movement of the pharyngeal walls in this portion, together with elevation of the soft palate and the posterior portion of the tongue, are crucial for velopharyngeal closure. Inadequate closure, or velopha- ryngeal incompetence, can result in disordered speech production.
The hypopharynx extends from the base of the tongue at the level of the hyoid bone and tip of epiglottis down to the entrance of the larynx and esophagus.
RESPIRATORY PHONATORY ARTICULATORY
Upper Airway Larynx Lips
Nose Vocal Cords Tongue
Mouth Cartilage Palate
Pharynx Muscle
Nasopharynx Mucous
Oropharynx Membrane
Hypopharynx Ligaments Lower Airway
Trachea Lungs
4.1
Components of Speechtracheostomy. A tracheostomy is an artificial open- ing created between the outer surface of the neck and the trachea between the second and third tracheal rings. The opening itself is referred to as the stoma, and the tracheostomy tube inserted into the trachea through the stoma serves to maintain the opening, as well as provide means for connecting mechanical ventilatory devices. Tracheostomy provides a secure airway, long-term airway access, and a means for inter- face with mechanical ventilatory devices, and as such, is the most frequently used method of airway man- agement. Placement of the tracheostomy tube diverts airflow away from the trachea through the tube and out the neck, bypassing the upper airway, including the vocal cords. Depending on the size and type of tracheostomy tube, a portion of the airflow will still pass around the tube and through the vocal cords;
this may or may not be sufficient to produce sound.
In the event that it is not sufficient, options to facil- itate sound include downsizing of the tracheostomy tube to a smaller diameter and use of a unidirectional flow valve such as the Passy-Muir valve (4), which directs greater air flow through the upper airway and out the nose and mouth. Table 4.2 reviews factors for Lower Airway
The lower airway consists of the tracheobronchial tree and the lungs. The tracheobronchial tree consists of a system of connecting tubes that conduct airflow in and out of the lungs and allow for gas exchange.
Trachea. The trachea is situated anterior to the esoph- agus, beginning at the cricoid cartilage and extend- ing inferiorly to the carina, where it bifurcates into the right and left main-stem bronchi. It is composed of C-shaped cartilage rings joined by connective tis- sue. These cartilage rings assist in keeping the tra- chea open during breathing. As noted previously, the mucous membranes of the trachea are softer, looser, and more fragile than those of the adult and more sus- ceptible to damage, increasing the risk of obstruction from edema or inflammation.
Lungs. The lungs are situated in the thoracic cavity, enclosed by the rib cage and diaphragm, the major muscle of ventilation, which separates the thoracic cavity from the abdominal cavity. The diaphragm in an infant is flatter than that of an adult, resulting in less efficient functioning for respiration. The air pas- sages in infants and small children are much smaller, increasing their susceptibility to obstruction. The respiratory bronchioles, alveolar ducts, and alveoli grow in number until about 8 years of age, after which they continue to grow in size. Impairments in lung function can occur as a result of birth-related condi- tions such as bronchopulmonary dysplasia and dia- phragmatic hernia, or due to acquired disorders such as spinal cord injury. These impairments often require tracheostomy and/or mechanical ventilation, which in turn have an impact on speech production.
Contribution of Respiratory Dysfunction to Speech Disorders
Speech disorders related to respiratory dysfunction are often secondary to the presence of tracheostomy and/or ventilator dependence. The primary diagnoses of chil- dren requiring chronic tracheostomy and/or ventilator dependence include conditions due to trauma such as brain injury, spinal cord injury and direct injury to the trachea; congenital conditions; progressive neurologic disorders; and acquired nontraumatic conditionssuch as Guillain-Barré syndrome and anoxic encephalopathy (3).
It is important to note that the causes of respiratory failure and subsequent need for mechanical ventilation are not always respiratory disease or disorder. The lungs them- selves may be healthy, but access to them or the systems that contribute to their function may be impaired.
A primary means of airway management in the presence of chronic respiratory insufficiency is a
4.2
Tracheostomy Tube Decision Flow ChartTTS—CUFF
↓ → ⇓
LW PRESS AIRCUFF↓ →
⇓
LW PRESS AIRCUFF ↑ →
⇓
TALKING TRACH → AAC
CUFFLESS CUFF ↓ PRTCUFF ↓
ADJ VENT →
SAME SZ → ADJ VENT ⇓
⇓ ⇓
PHON PHON PHON ENT-
W/LEAK → W/LEAK → W/LEAK → VF EXAM
⇓ ⇓ ⇓
CUFF↓DAY
UFV UFV CUFF↑NT
IN LINE IN LINE ⇓
UFV IN LINE
Note: A double-arrow pointing down indicates progression if successful with that step; arrow pointing to the right indicates progression if that step was not successful. Single arrow pointing down indicates deflate/
decrease pressure. Arrow pointing up indicates inflate/increase pressure.
TTS, tight-to-shaft cuff; Same SZ, same size; AAC, augmentative and alternative communication; LW PRESS, low pressure; ADJ, adjust;
PRT cuff, partial cuff; ENT, otolaryngologist; VF, vocal folds; Phon, phonation; UFV, unidirectional flow valve.
Source: From Ref. 5.
Sound is generated in the larynx, and that is where pitch and volume are manipulated. The strength of expiration of air from the lungs also contributes to loudness, and is necessary for the vocal folds to pro- duce speech (Fig. 4.2) (6).
Most of the muscles of the larynx receive their inner- vation via the recurrent laryngeal branch of the vagus nerve. This branch descends downward and wraps around the aorta, and for this reason, children who undergo cardiac surgery can sometimes experience voice disorders. If the recurrent laryngeal nerve is stretched or damaged during surgery, innervation to the vocal cords can be disrupted, and vocal hoarseness can occur.
consideration when determining the most efficient tra- cheostomy tube to use (5).
Phonation
The phonatory system is comprised of the larynx, and provides the sound source for speech. When this sound source is disrupted, it may result in alterations in voice quality, thus affecting communication.
The larynx is made up of cartilage, ligaments, muscles, and mucous membrane. It protects the entrance to the lower airway and houses the vocal cords (Fig. 4.1) (6).
Figure 4.2 The vocal cords.
Median glosso-epiglottic ligament
Root of tongue (lingual tonsil)
Epiglottis Ventricular folds (false cords)
Aryepiglottic fold Cuneiform tubercle Interarytenoid incisive
Normal larynx: Inspiration Normal larynx: Phonation
Vocal folds (true cords)
Trachea Pyriform fossa Corniculate tubercle Esophagus
Epiglottis Hyoid bone Thyrohyoid membrane
Superior cornu of thyroid cartilage Thyroid cartilage lamina
Corniculate cartilage Arytenoid cartilage
Vocal ligament Cricothyroid ligament
Inferior cornu of thyroid cartilage
Cricoid cartilage Trachea
Anterior aspect Posterior aspect
Figure 4.1 The larynx.
articulators are located, as well as places of articula- tion for various speech sounds. Impairment in one or more of these components is likely to result in a disor- der of articulation/resonance.
Contribution of Articulatory/Resonatory Dysfunction to Speech Disorders
Speech disorders related to articulatory/resonatory dys- function include disorders that result from impairment in any component of the articulatory/resonatory system, and as such are quite comprehensive. They include all motor speech disorders, including dysarthria and apraxia (Table 4.4), as well as disorders resulting from congenital conditions such as cleft palate.
Although the three components of speech described previously are considered separately as individual components, they function as a single coordinated and interactive unit for production of speech, and as such, are subsystems of a complex motor act requiring pre- cise coordination of muscle groups. It is easy to under- stand how impairments in any of these components can have an impact on communication, as the extent and complexity of the speech system make it suscepti- ble to the influence of a myriad of factors.
Motor Speech Disorders
Motor speech disorders are a collection of communi- cation disorders involving retrieval and activation of motor plans for speech, or the execution of movements for speech production (7). Subcategories include dys- arthria and apraxia of speech. Motor speech disor- ders occur in both children and adults. They may be acquired or developmental in nature (Table 4.3).
Acquired: adverse event (usually neurologic) occurs that impedes continuation of previously normal speech acquisition
Developmental: no specific identifiable etiology to explain delays in speech acquisition
Dysarthria refers to a group of related motor speech disorders resulting from impaired muscular
Contribution of Phonatory
Dysfunction to Speech Disorders
Speech disorders related to phonatory dysfunction are generally classified as voice disorders, and include dysphonia (abnormal voice quality) and aphonia (loss of voice). Dysphonia is an impairment of voice sec- ondary to cranial nerve involvement, laryngeal pathol- ogy or tracheostomy, and is characterized by varying degrees of breathiness, harshness, and vocal strain.
Dysphonia may be a prominent feature of dysarthria related to cranial nerve involvement. Laryngeal pathol- ogies resulting in dysphonia may include polyps, gran- ulomas, nodules, or other lesions affecting the vocal fold mucosa. A common vocal fold trauma resulting in dysphonia is traumatic intubation following serious injury requiring assisted ventilation.
Articulation/Resonance
The articulatory/resonatory system is composed of the structures of the oral and nasal cavities, which modulate the airstream into the acoustic waveforms perceived as speech. Articulators responsible for pro- duction of speech sounds include the lips, tongue, and palate.
In addition to the placement of articulators, suc- cessful production of accurate speech sounds requires adequate functioning of the oral and nasal cavities as resonating chambers (resonance). Modulation of the airstream by these structures is a complex process that relies on intact structures as well as precise neuromus- cular coordination. Fig. 4.3 illustrates where various
Figure 4.3 Places of articulation.
Velar Palato-
alveolar Palatal Alveolar
Uvular Glottal Dental
Labiodental Bilabial
Interdental
4.3
Motor Speech DisordersDEVELOPMENTAL ACQUIRED Phonological disorder Dysarthria
Verbal apraxia Verbal apraxia
Articulation disorder Articulation disorder
Oral apraxia refers to an impairment of the vol- untary ability to produce movements of the facial, labial, mandibular, lingual, palatal, pharyngeal, or laryngeal musculature in the absence of muscle weakness.
Verbal apraxia (also called apraxia of speech, or AOS) refers to an impairment of motor speech charac- terized by a diminished ability to program the posi- tioning and sequencing of movements of the speech musculature for volitional production of speech sounds. Apraxia is not the result of muscle paralysis or weakness, but may lead to perceptual disturbances of breathing/speaking synchrony, articulation, and pros- ody. Site of lesion is generally the left precentral motor or insular areas.
Developmental verbal apraxia (also called develop- mental apraxia of speech, or DAOS) refers to a speech disorder resulting from delays or deviances in those processes involved in planning and programming movement sequences for speech in the absence of mus- cle weakness or paralysis. Associated characteristics of DAOS include receptive-better-than-expressive lan- guage, presence of oral apraxia (may or may not exist with DAOS), phonemic errors (often sound omissions), difficulty achieving initial articulatory configuration, increase in errors with increase in word length and/
or phonetic complexity, connected speech poorer than word production, inconsistent error patterns, groping and/or trial-and-error behavior, and presence of vowel errors.
control of the speech mechanism, and manifested as disrupted or distorted oral communication due to paralysis, weakness, abnormal tone, or incoordination of the muscles used in speech (Table 4.4) (8). It affects the following:
Respiration: respiratory support for speech, breathing/
speaking synchrony, sustained phonation Phonation/Voice: loudness, quality
Articulation: precision of consonants and vowels Resonance: degree of airflow through nasal cavity Prosody: melody of speech, use of stress and inflection
Movements may be impaired in force, timing, endurance, direction, and range of motion. Sites of lesion include bilateral cortices, cranial nerves, spinal nerves, basal ganglia and cerebellum.
Associated characteristics of dysarthrias include slurred speech; imprecise articulatory contacts; weak respiratory support and low volume; incoordination of the respiratory stream; hypernasality; harsh or strained/strangled vocal quality; weak, hypophonic, breathy vocal quality; involuntary movements of the oral facial muscles; spasticity or flaccidity of the oral facial muscles; and hypokinetic speech.
Some common etiologies for dysarthria in chil- dren include stroke, brain tumor, aneurysm, traumatic brain injury, encephalopathy, seizure disorder, cere- bral palsy, and high-level spinal cord injury.
4.4
Types of DysarthriaSPASTIC HYPOKINETIC HYPERKINETIC ATAXIC FLACCID MIXED Site of Lesion Bilateral upper
motor neuron
Extra-pyramidal system
Extra-
pyramidal system
Cerebellum Unilateral or bilateral lower motor neuron
Multiple sites of lesion Associated
characteristics
Spasticity of orofacial muscles Imprecise articulatory contacts Strained/
strangled voice quality Monopitch Reduced stress Reduced rate
Rigidity of orofacial muscles
Imprecise articulatory contacts Hypophonia Monopitch Reduced stress and inflection
Transient increased rate/rapid rate
Involuntary movements of orofacial muscles Imprecise articulatory contacts
Harsh voice quality Incoordination of the respiratory stream Transient increased rate
Irregular articulatory breakdown Harsh vocal quality
Incoordination of the respiratory stream
Excess and equal stress pattern Reduced rate
Flaccidity of the orofacial muscles Imprecise articulatory contacts Breathy voice quality
Low vocal volume Reduced stress and inflection Hypernasality
Characteristics dependent on site of lesion
Example of disorder
Cerebral palsy Parkinson’s disease Dystonia Friedreich’s ataxia Bulbar palsy Amyotrophic lateral sclerosis Source: From Ref. 8.
Variations in tongue position for production of dif- ferent vowels are systematically characterized as high, mid, or low, as well as front, central, or back, and can further be described as tense or lax (Fig. 4.6) (12). For example, the vowel /i/, pronounced “ee,” is considered a high, front, tense vowel, as the front of the tongue is Children with motor speech disorders may dem-
onstrate impaired phonological systems because their ability to acquire the sound system of their language is believed to be undermined by difficulties in managing the intense motor demands of connected speech (9).
Language Components
With regard to models of language, the prevailing school of thought follows Bloom and Lahey’s philosophy, which proposes three main components of language: form, con- tent, and use (Fig. 4.4). According to Bloom and Lahey, language can be defined as “a knowledge of a code for representing ideas about the world through a conventional system of arbitrary signals for communication (10).”
These three components can be subdivided further into phonology, morphology, syntax, semantics, and pragmatics, as described in the following sections.
Form
Form with reference to language refers to the rule- based structure humans employ to formulate language, ranging from phonemes to sentences, and comprises phonology, morphology, and syntax.
Phonology refers to the rule-governed system by which sounds, or phonemes, are combined to create meaningful units, or words. The English language contains 44 recognized phonemes, which are classi- fied as consonants or vowels. This distinction involves presence or absence of interruption of the air stream.
Vowels are formed through modulation (without inter- ruption) of the air stream via variation in position of the lips and tongue (Fig. 4.5) (11).
Form
• word order
• word endings
• speech
Use
• conversation
• social rules
• matching language to the situation
Content
• word meanings
• the way word meanings link together
• sequencing
Figure 4.4 The three components of language.
i
r
e ɜ
ə ʌ
ɔ
ɑ ɒ æ
a ə-
U o ʉ
i
ɛ
ɜ-
u
( )
(æ)
Lips unroundedtoLips rounded Mouth opentoMouth closed Front
Tense
Lax High
Mid
Low Tense
Tense Lax
Lax
Central Back
Lips opentoLips spread Mouth opentoMouth closed
Figure 4.6 Tongue positions for vowel production.
(Reprinted with permission from Bronstein AJ. The pronunciation of American English. New York:
Appleton-Century-Crofts, Inc., 1960.)
Front Central
Back
High Medium Low
Figure 4.5 Vowel areas.