DYSPHAGIA

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DYSPHAGIA

• 3236

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Esophagus
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Esophagus

• A. Empty tube approx.
• 20 cm in length
• (See Figure 2-4, page 15 in Kahrilas)

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Esophagus (cont.)

• B. Two muscle layers
• 1. Inner circular layer
• 2. Outer longitudinal layer

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Esophagus (cont.)

• C. Muscle Type
• 1. Upper 1/4 striated (similar to pharyngeal
  muscles)
• 2. Middle 1/4 mixed striated smooth
• 3. Lower 1/2 smooth (similar to gastric muscles)

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Esophagus (cont.)

• D. Innervation -Vagus Nerve
• 1. Meissner's plexus - "submucosal" between
  muscularis mucosa and circular muscle layer

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Meissner's plexus
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Esophagus (cont.)

• D. Innervation -Vagus Nerve (cont.)
• 2. Auerbach's plexus - "myenteric"
  between circular and longitudinal
  muscle layers

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Auerbach's plexus
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Esophagus (cont.)

• E. Esophageal Peristalsis
• 1. Onset with bolus entry through Upper
  Esophageal Segment
• 2. Moves from striated to smooth

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Swallow Response Neurophysiology
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A. Sensory Input

• 1. Anterior 2/3 of tongue (cont.)
• a) General Sensation - Trigeminal (V)
  (Lingual nerve)
• b) Taste - Facial nerve (VII) (chorda
  tympani)

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A. Sensory Input (cont.)

• 2. Posterior 1/3 of tongue (cont.)
• a) Glossopharyngeal (IX) for Gen. Sensation
  Taste

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A. Sensory Input (cont.)

• 3. Pharynx (gen sens.)
• a) Vagus (X) (via SLN Pharyngeal Branch)
• b) Glossopharyngeal(IX)

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Primary Afferent input controlling the swallowing
response is from the Superior Laryngeal Nerve.
(Kahrilas Figure 2-5, page 17)
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B. Motor Innervation
1. Glossopharyngeal (IX) 2. Vagus
(X) 3. Hypoglossal (XII).
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C. CENTRAL SWALLOW CENTER?
1. Medullary Reticular Formation - most ventral
(toward belly) part of the reticular formation
extending rostrally through the pons and midbrain
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C. CENTRAL SWALLOW CENTER?
1. Medullary Reticular Formation
a. Receives sensory input for swallowing from
Vagus (primarily superior laryngeal nerve) and
Glossopharyngeal nerves.
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C. CENTRAL SWALLOW CENTER?
1. Medullary Reticular Formation
b. Receives excitatory motor input from
structures involved in motor control including
the motor and premotor cerebral cortex via
cortico reticular pathway
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C. CENTRAL SWALLOW CENTER?
1. Medullary Reticular Formation
c. Sends excitatory motor output via anterior and
lateral reticulospinal tract
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Schematic of Theoretical Model of Neural Control
of Swallowing
Cerebral Cortex
Corticoreticular Pathway
Dorsal and Ventral Trigeminal Lemniscus
MOTOR PATHWAYS
SENSORY PATHWAYS
Medullary Reticular Formation
Reticulospinal Pathway
Spinal Trigeminal Neucleus and Tract
CN Motor Nuclei V, IX, X, XII Spinal Motor Neurons
CN Sensory Nuclei VI, VII, X
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C. CENTRAL SWALLOW CENTER?
1. Medullary Reticular Formation
d. Only one side of the medullary swallowing
center is necessary to coordinate a swallow
response.
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NOTE CORTICAL INPUT IS NOT NECESSARY FOR NORMAL
SWALLOW RESPONSE (HOWEVER, DAMAGE TO PRECENTRAL
GYRUS HAS BEEN ASSOCIATED WITH ORAL PHASE
IMPAIRMENT)
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• C. Sequence of events from CNS to cranial
  nerves
• 1 . Appropriate sensory stimulation
  activates the swallow center
• 2. "...the entire behavior of swallowing
  results from activation of the center." (p.
  17)

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• C. Sequence of events from CNS to cranial
  nerves (cont.)
• 3. A bilateral sequence of excitation and
  inhibition occurs involving
  approximately 2 dozen motoneuron pools
  scattered throughout the brainstem.

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• C. Sequence of events from CNS to cranial
  nerves (cont.)
• 4. Efferent signal activates portions of the
  nucleus ambiguous and nuclei of cranial nerves V,
  VII, and XII (associated with oral phase)

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• C. Sequence of events from CNS to
  cranial nerves (cont.)
• 5. Once stimulated, the entire pharyngeal
  swallowing response is generated (CN X)

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• C. Sequence of events from CNS to
  cranial nerves (cont.)
• 6. An apneic pause of .5 to 3.5 sec. accompanies
  swallowing. The swallow center inhibitory
  influence overrides respiratory centers competing
  for access to the same motoneurons.

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Swallow Response Neurophysiology (cont.)

• D. Sequence of muscle contraction events
  (observed experimentally, Doty Bosma, 1956)

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• D. Sequence of muscle contraction events
• 1. Mylohyoid contraction (first detectible
  action, precedes other muscular contraction by
  30-40 ms)

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• D. Sequence of muscle contraction events
• 2. "Leading complex" activation

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• 2. "Leading complex" activation
• a) Posterior tongue
• b) Superior constrictor
• c) Palatopharyngeus
• d) Stylohyoid
• e) Geniohyoid

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• D. Sequence of muscle contraction events
• 3. Pharyngeal constrictors fire in overlapping
  order
• 4. Cricopharyngeal dilation
• 5. Esophageal peristalsis (velocity between 2-4
  cm sec)