SH 598- Voice Disorders

Syllabus• Office hours: T; TH 2-4 PM and 9-10 AM

(Friday); by appointment.

• Phone: 673-3202

• Teaching Assistant: Donna Eduardo

• Required Text: Understanding Voice

Problems- Colton & Casper.

Instructional Methods• lecture

• case studies

• objective exam

• individual project & presentation

• essay exam

• directed readings

• class activities

Grading

• Scale

• Critiques

• Grade postings

IMPORTANT!!

• Missing exams- Illness

• Office Hours

• Clinic office hours

Anatomy and Physiology of Voice

Production

What is voice?• The acoustic result of the interaction between:

– muscle groups – cartilage's and – the aerodynamic system.

• Three major subsystem to be concerned about:

– Respiratory

– Phonatory

– Supraglottal

Anatomy of the Larynx• Review:

-Anatomical structures of the larynx, including the primary cartilage's and intrinsic and extrinsic musculature.

-The function of the individual muscles should become a second language to you...at least until the semester ends!

Structural Support of the Larynx

• Larynx suspended by a single bone: hyoid bone.

• 6 laryngeal cartilage's: 3 paired and 3 unpaired: Provide structural support

Laryngeal Cartilage's

• Epiglottis:

-Shaped like a long leaf,

-Base attached to inner portion thyroid cartilage,

-Folds down over airway to protect during swallowing.

-Composed of elastic cartilage (does not ossify with age).

• Thyroid Cartilage:

-Angled saddle-shaped,

-Anterior attachment of true vocal folds,

-Posteriorly there are 2 superior cornu and 2 inferior cornu,

-Composed of hyaline cartilage- ossifies & limits flexibility with age,

-Lateral walls are laminae and attach to midline of notch.

• Cricoid Cartilage:-Signet ring shaped,

-2 sets of paired faces: Connects to other joints,

-Cricothyroid joint: Connects the cricoid to inferior cornu of the thyroid cartilage.

Arytenoid, Corniculate & Cuneiform Cartilage's:

-Hyaline,

-Pyramid shaped with 3 surfaces, anterior angle forms the vocal process,

-Lateral angle: muscular process, attaches to intrinsic muscles,

-Corniculate attached to superior tips of arytenoid cartilage,

-Cuneiform embedded in muscular complex, superior to corniculate: Provide no clear function, add stability for

abduction.

Laryngeal Cartilage's

• 3 Unpaired Cartilage's

-Epiglottis

-Thyroid

-Cricoid

• 3 Paired Cartilage's

-Cuneiform

-Corniculate

-Arytenoid

Extrinsic Laryngeal Muscles• Three Main Purposes:

1) Fixation (primary role)2) Elevation (move larynx up)3) Depression (move larynx down)

• Two major groups: Suprahyoid & Infrahyoid• Anatomical position:

Suprahyoid- Attachment lies above hyoid bone.

Infrahyoid- Attachment lies below hyoid bone.

Extrinsic Laryngeal Muscles• Suprahyoid Muscles:

1) Digastricus2) Geniohyoid3) Hyoglossus4) Mylohyoid5) Stylohyoid

• Function: Raise hyoid bone & indirectly raise larynx.

• Infrahyoid Muscles:1) Omohyoid & Sternohyoid:Function: Lowers the hyoid bone &

indirectly lowers larynx.

2) Sternothyroid:Function: Lowers thyroid cartilage

& lowers larynx.

3) Thyrohyoid:Function: Raises thyroid cartilage & raises larynx, or with thyroid fixed

lowers hyoid.

Extrinsic laryngeal Muscles

Mastoid Tip

Mylohyoid

Hyoid Bone

Sternohyoid

Omohyoid

Sternum

MandibleAnt. Digastric

Post.Digastric

Stylohyoid

Thyrohyoid

Sternothyroid

Intrinsic Laryngeal Muscles• Functions:

1) Abduction of vocal folds for respiration,

2) Fine discrete movements during voice production & closure of vocal folds and,

3) Protection of trachea,

More Specifically...

• Change degree of abduction/ adduction

• Change mass characteristics of folds

• Change tension of folds

• Change length characteristics of folds

• React during swallowing- closure of folds

• Assist in muscular mechanical advantage

Intrinsic Muscles

• Cricothyroid: fan-shaped, 2 divisions, Lengthens & tenses vocal folds.

Action of Cricothyriod

Pars oblique

Pars recta

Intrinsic Muscles

• Thyroarytenoid: muscle making up true vocal folds, 2 parts: thyrovocalis (bound to vocal ligament) & thyromuscularis (lateral to arytenoids).

ThyroarytenoidVocal

Ligament

Thyrovocalis

Thyromuscularis

Thyroarytenoid Functions

• Decreases distance between the thyroid & arytenoid cartilage's,

• Shortens folds,

• Decreases tension

• Decreases pitch of the voice,

• Active contraction lowers pitch of voice.

Intrinsic Muscles

• Posterior Cricoarytenoid: Abducts the vocal folds, actively contracted at the end of phonation & any speech sound not requiring v.f. vibration.

PosteriorCricoarytenoid

Action of Post.Cricoarytenoid

Intrinsic Muscles

• Lateral Cricoarytenoid: lies on upper surface of cricoid cartilage, adducts vocal processes of arytenoids closing membranous portion of v.f.’s.

Action of Lat.Cricoarytenoid

LateralCricoarytenoid

Intrinsic Muscles

• Interarytenoids (transverse & oblique): Unpaired, 2 part muscle, adducts v.f.’s in cartilaginous portion by pulling arytenoid tips together.

ObliqueInterarytenoids

TransverseInterarytenoids

The Glottis

• Glottis is an open space between vocal folds.• Size is dependent on what position the v.f.’s are in.• Not a muscle or cartilage.• Abduction- open v.f.’s; Adduction- closed v.f.’s

Glottis

Ventricular Folds

• False Folds,

• Superior & lateral to true vocal folds,

• Their role in phonation?

-No role in voicing

• Consist of muscle, but doesn’t have innervation for discrete movements,

• Hyperfunctional voice?

Neuroanatomy of Vocal Mechanism

• Volitional control of laryngeal muscles:

Resides in brain.

• Connecting points in brain having a role in

control of phonation: cortex, subcortical

areas, midbrain & medulla.

• Next slides will briefly review phonation

neuroanatomy & neurophysiology.

Cortical Mechanisms of Phonatory Control

• The cerebral cortex is responsible for conceptualization, planning, and execution of the speech act (phonation).

• Three major areas of cortex responsible for vocalization:

• a) Precentral & postcentral gyrus,

• b) Anterior (Broca’s) area, and

• c) Supplementary motor area.

Cortical Areas Involved in Speech Movement Control

1. Stimulation of these areas can initiate, stop or distort vocalization.

2. These behaviors occur in dominant & nondominant hemispheres.

Premotor & SupplementaryCortex

Broca’s Area

Primary Motor Cortex

Somatosensory Cortex

Speech and Phonation are Complex Motor Acts• Involves simultaneous activation and control

of many muscles.• Control of these motor acts occurs in cortex.• Control of individual muscles occurs lower in

brain.• No evidence that cortical stimulation

produces a response in a muscle.• Higher brain function = idealization of an

event, integration of sensory information, feedback control, and coordination of various muscles.

Subcortical Mechanisms

• Motor cortex:connections to Thalamus, a major portion of diencephalon or interbrain.

• Parts of diencephalon: a) hypothalamus, b) metathalumus, c) epithalumus, d) subthalamus, and, e) third ventricle.

• Thalamus has major pathways to motor cortex & Broca’s area.

• Thalamus also connects to midbrain, cerebellum and other structures in diencephalon.

Nuclei in the thalamus that project to parts of cerebral cortex

• Motor area receives projections from ventrolateral nucleus.

• 1971- Found that ventrolateral nucleus was responsible for initiation of speech movements & control of loudness, pitch, rate & articulation.

• Broca’s area- receives connections from dorsomedian & centromedian nuclei. Ventral

Lateral

Ventral posteriorLateral

DorsalMedian

to & from Prenucleus

to & fromSup. Parietal Lobule

to & fromParietal Lobe

LateralDorsal

MassaIntermedia

Thalamus: What Does it Do?• Acts as relay for

impulses in lower brain.

• integrates emotion into complex motor act.

• Plays a major role in:

• coordinate outgoing information:cortex

• integrating incoming sensory information and,

• adding emotion to speech.

Thalamus

Projections to Cerebral Cortex

MidbrainProjections

to CerebellarCortexDiencephalon

Pons

Midbrain Structures

• Midbrain (mesencephalon) lies beneath thalamus.

• Cerebral peduncles lie on anterior surface of midbrain and connect cerebrum with brainstem and spinal cord.

• Posterior side has four colliculi: Superior (visual function), inferior (audition).

• Within midbrain lies cerebral aqueduct of Sylvius, surrounded by periaqueductal gray.

Periaqueductal Gray: What does it do?

• Stimulation of dorsal and ventrolateral areas of periaqueductal gray = activity in some laryngeal muscles.

• 1985- Larson reported cells in ventrolateral area stimulate muscle activity, whereas some suppress activity.

• Periaqueductal gray is an intermediate area between recognition of a stimulus and production of motor act.

Brainstem

• Bilateral structures in brainstem implicated in neural control of phonation:

• Nucleus ambiguus

• Nucleus tractus solitarii

• Nucleus parabrachialis

• How do we know these structures are involved in phonation?

Cerebellum• Structure lying posterior to midbrain area.

• Control of movement.

• Three main portions: a) Vermis, b) Pars Intermedia, c) Hemispheres

• Consists of traverse folia- increases surface area.

• Fissura prima- fissure separating anterior & posterior lobes.

Peripheral Connections: The Vagus Nerve

• Major nerve that supplies larynx.• Provides sensory fibers in larynx & fibers to

control muscles of larynx.• Cell bodies of vagus located in nucleus

ambiguus.• Laryngeal muscles controlled by cells in caudal

portions of nucleus.• Vagus emerges from surface of medulla

between cerebellum peduncle and inferior olives in midbrain.

• Vagus exits skull through jugular foramen.

Distribution of Vagus (X) Nerve

Pharyngeal nerveSuperior laryngeal

nerve

chief part

vagal accessory

Nucleusambiguus

Jugular foramen

Vagus (X) nerve

Recurrent Laryngeal Nerve

Vagus (X) Nerve

Jugular Foramen Cricothyroid

muscle

Superior Laryngeal

Nerve

Nucleus AmbiguusPharyngeal

Nerve

Vagus innervation of larynxNodose ganglion

Pharyngeal branch

Sup. laryngealnerveInternal SLNExternal SLN

Cricothyroid memb.

Common carotid artery

Left recurrentlaryngeal nerveVagus nerve

Hyoid bone

Thyroid memb.

Thyroid gland

Right recurrentlaryngeal nerve

What nerve innervates the intrinsic laryngeal muscles?

• Intrinsic laryngeal muscles are innervated by branches of vagus (X) nerve

• The vagus nerve splits into several branches:

1. Recurrent laryngeal nerve,2. Superior laryngeal nerve,3. Pharyngeal nerve.

Recurrent Laryngeal nerve of Vagus

• Courses along laryngeal branch of inferior thyroid artery.

• It passes under caudal border of inferior constrictor muscle.

• Divides into a motor & sensory branch prior to entry into larynx.

• Innervates int. muscles that control abduction/adduction of vocal folds

RLN & SLN

• Inferior Recurrent Laryngeal Branch:– Thyroarytenoid

– Lateral Cricoarytenoid

– Posterior Cricoarytenoid

– Interarytenoids

• Superior Laryngeal Branch:– Cricothyroid

SLN & RLN• Ensure ability of intrinsic muscles

to move quickly & fine motor control

• High conduction velocity• Rapid contractions• Low innervation per motor unit

ratio.

Conclusion

• Neurology of larynx is specific and finely tuned

• More is known about peripheral connections

• Less known about higher brain centers

• Coordination of respiratory, phonatory & supraglottal areas must occur for adequate speech production.

Readings & Directed Reading Assignment

• For lecture - Chs. 10 & 11 in Colton & Casper.

• Directed Reading assignment- Hoit, J.D.(1995). Influence of body position on breathing and its implications for the evaluation and treatment of speech and voice disorders. Journal of Voice, vol.9 (4): 341-347.

Activity1) With you mouth open, hold your breath,

then abruptly release it with a vocal tone. What physiologic events occur at the glottis?

2) Produce an /h/ sound alone. What is the status of the glottis? How did it get there?

3) Produce an /h/ sound, then slide into phonation. What muscles are contracting to affect what conditions in the glottis?

More questions...

1) Place your finger on the laryngeal prominence, alternate between high and low pitched tones. Can you identify a change in the position of the larynx and describe the prime movers?

2) Can you phonate while inhaling? What are the physiological differences?