SH 598- Voice Disorders

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SH 598- Voice Disorders
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Syllabus

• Office hours T TH 2-4 PM and 9-10 AM (Friday)
  by appointment.
• Phone [phone]
• Teaching Assistant Donna Eduardo
• Required Text Understanding Voice Problems-
  Colton Casper.

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Instructional Methods

• lecture
• case studies
• objective exam
• individual project presentation
• essay exam
• directed readings
• class activities

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Grading

• Scale
• Critiques
• Grade postings

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IMPORTANT!!

• Missing exams- Illness
• Office Hours
• Clinic office hours

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Anatomy and Physiology of Voice Production
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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

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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!

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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

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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).

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• 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.

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• 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.

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• 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.

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Laryngeal Cartilage's

• 3 Unpaired Cartilage's
• -Epiglottis
• -Thyroid
• -Cricoid

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• 3 Paired Cartilage's
• -Cuneiform
• -Corniculate
• -Arytenoid

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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.

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Extrinsic Laryngeal Muscles

• Suprahyoid Muscles
• 1) Digastricus
• 2) Geniohyoid
• 3) Hyoglossus
• 4) Mylohyoid
• 5) Stylohyoid
• Function Raise hyoid bone indirectly raise
  larynx.

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• 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.

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Extrinsic laryngeal Muscles

• Mastoid Tip
• Mylohyoid
• Hyoid Bone
• Sternohyoid
• Omohyoid
• Sternum

Mandible
Ant. Digastric
Post. Digastric
Stylohyoid
Thyrohyoid
Sternothyroid
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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,

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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

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Intrinsic Muscles
Action of Cricothyriod
Pars oblique
Pars recta

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

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Intrinsic Muscles
Vocal Ligament
Thyroarytenoid
Thyrovocalis
Thyromuscularis

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

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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.

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Intrinsic Muscles
Posterior Cricoarytenoid
Action of Post. Cricoarytenoid

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

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Intrinsic Muscles
Action of Lat. Cricoarytenoid
Lateral Cricoarytenoid

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

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Intrinsic Muscles
Transverse Interarytenoids
Oblique Interarytenoids

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

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The Glottis
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

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Ventricular Folds

• False Folds,
• Superior lateral to true vocal folds,
• Their role in phonation?
• -No role in voicing
• Consist of muscle, but doesnt have innervation
  for discrete movements,
• Hyperfunctional voice?

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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.

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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 (Brocas) area, and
• c) Supplementary motor area.

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Cortical Areas Involved in Speech Movement Control
Primary Motor Cortex
Premotor Supplementary Cortex
Somatosensory Cortex
Brocas Area

• 1. Stimulation of these areas can initiate, stop
  or distort vocalization.
• 2. These behaviors occur in dominant
  nondominant hemispheres.

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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.

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Subcortical Mechanisms

• Motor cortexconnections 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
  Brocas area.
• Thalamus also connects to midbrain, cerebellum
  and other structures in diencephalon.

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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.
• Brocas area- receives connections from
  dorsomedian centromedian nuclei.

to from Sup. Parietal Lobule
to from Parietal Lobe
Massa Intermedia
to from Prenucleus
Lateral Dorsal
Dorsal Median
Ventral posterior Lateral
Ventral Lateral
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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 informationcortex
• integrating incoming sensory information and,
• adding emotion to speech.

Projections to Cerebral Cortex
Thalamus
Midbrain
Projections to Cerebellar Cortex
Diencephalon
Pons
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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.

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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.

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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?

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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.

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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.

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Distribution of Vagus (X) Nerve
Nucleus Ambiguus
Pharyngeal Nerve
Nucleus ambiguus
chief part
vagal accessory
Vagus (X) nerve
Jugular foramen
Vagus (X) Nerve
Superior Laryngeal Nerve
Pharyngeal nerve
Superior laryngeal nerve
Jugular Foramen
Cricothyroid muscle
Recurrent Laryngeal Nerve
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Vagus innervation of larynx
Nodose ganglion
Pharyngeal branch
Hyoid bone
Sup. laryngeal nerve
Thyroid memb.
Internal SLN
External SLN
Thyroid gland
Cricothyroid memb.
Right recurrent laryngeal nerve
Common carotid artery
Left recurrent laryngeal nerve
Vagus nerve
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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.

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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

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RLN SLN

• Inferior Recurrent Laryngeal Branch
• Thyroarytenoid
• Lateral Cricoarytenoid
• Posterior Cricoarytenoid
• Interarytenoids
• Superior Laryngeal Branch
• Cricothyroid

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SLN RLN

• Ensure ability of intrinsic muscles to move
  quickly fine motor control
• High conduction velocity
• Rapid contractions
• Low innervation per motor unit ratio.

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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.

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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.

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Activity

• 1) 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?

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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?