Neuroanatomy Review Relative to Swallowing: Part II Susan G. Butler, Ph.D., CCC-SLP

Review of the Cranial Nerves We Assess Indirectly During Oral Mechanism Examinations

 

Cranial Nerve V: Trigeminal

• The Trigeminal Nerve emerges from the pons of the brainstem. It has both motor and sensory components.

Motor: Supplies muscles of mastication and some of the suprahyoid muscles (i.e., anterior belly of digastric, mylohyoid) that facilitate hyolaryngeal elevation.

Sensory:

Oral cavity * Nasal cavity * Tongue * Teeth * Face

The Trigeminal Nerve has three branches:.

1. Opthalamic- Opthalamic branch courses near the upper face and eyes.
2. Maxillary- Maxillary branch courses around the nose and upper lips areas.
3. Mandibular – Mandibular branch courses around the lower face and chin.

Brief Functional Assessment:

Motor:

• Palpate for strength and symmetry of jaw opening and closing; laryngeal elevation with phonation (/g/), and swallowing.

Sensory:

• Lightly stroke both sides of buccal area, tongue, lips, face with a feather or cotton swab. May ask , “Does this side feel the same or different as the other side?”

Example Report Writing:

• “ Presents with jaw opening and closing WNL.”
• “ Presents with hyolaryngeal excursion WNL.”
• “Demonstrates adequate tactile sensation of oral cavity and structures.”

 

Cranial Nerve VII: Facial

• The Facial Nerve emerges from the lower margin on the Pons. It has both motor and sensory components.

Motor:

• Supplies muscles of facial expression and some of the supra-hyoid muscles (i.e., posterior belly of digastric, stylohoid).

Sensory:

• Taste from anterior two-thirds of the tongue and the hard and soft palates.

Brief Functional Assessment:

Motor:

• Pucker lips like giving a kiss, smile, lift eyebrows and then scowl.

Sensory:

• Give a LifeSaver and ask “What flavor is that?”

Example Report Writing:

• “ Presents with labial protrusion and eversion WNL.”
• “ Presents with upper face strength and ROM WNL.”
• “ Presents with hyolaryngeal excursion WNL.”
• “ Presents with gustatory discrimination for sweet WNL.”

 

Cranial Nerve IX: Glossopharyngeal

• The Glossopharyngeal Nerve emerges from the medulla.

Motor:

• Supplies some of the muscles in palatal elevation.

Sensory:

• Tactile sensation to posterior tongue.
• Taste from posterior one third of the tongue.

 

Brief Functional Assessment

Motor:

• Say “ahhh” loudly.
• May elicit gag and assess for velopharyngeal movement.

Sensory:

• Offer a cracker and ask what does that taste like?
• May touch back of tongue to see if gag is elicited.

 

Example Report Writing Motor:

• Report CN IX palatal elevation under CN X.

Sensory:

• “Presents with lingual mechanotactile sensory abilities WNL”
• “ Presents with gustatory discrimination for salty WNL.”

 

Cranial Nerve X: Vagus

• The Vagus Nerve emerges from the medulla.
• It has both sensory and motor components.
• The Vagus Nerve has three branches:
  1. Pharyngeal Branch
  2. Superior Laryngeal Branch a. Internal limb b. External limb

3. Recurrent Branch

Motor:

Pharyngeal:

• Supplies muscles of pharyngeal contraction.
• Supplies some of the muscles in velopharyngeal closure.
• Superior Laryngeal Branch – External Limb:

• Supplies innervation to the Cricothyroid muscle (responsible for voice pitch change).

Recurrent:

• Supplies innervation to all the intrinsic muscles of the larynx except the cricothyroid. Thus, it supplies innervation to the vocal fold adductor muscles and to the sole vocal fold abductor muscle (Posterior Cricoarytenoid).

Sensory:

Pharyngeal: Pharynx Superior Laryngeal Branch – Internal Limb:

• Supraglottic Sensation (responsible for feeling penetration of food).

Recurrent Branch:

• Subglottic sensation (responsible for feeling aspiration of food).

Brief Functional Assessment:

Motor:

Pharyngeal:

• (Assessing with CN X) – say “ah” and assess for superior bilateral palatal movement. Also, observe lateral superior pharyngeal wall approximation.

Superior Laryngeal Branch – External Limb:

• Pitch change tasks such as gliding voice on the vowel /i/ up and down the musical scale.

Recurrent:

• Say “ah” and assess voice quality in terms of vocal fold adduction. Think in terms of the ability of the vocal folds to approximate midline.
• Clear throat and cough while assessing potential for vocal fold adduction and ability to clear airway.

Sensory:

• (Assessing with CN IX) – May touch posterior oropharyn- geal wall with tongue depressor and ask if she feels the

depressor (This may also elicit gag reflex).

Example Report Writing:

• “Presents with palatal and oropharyngeal movement WNL on a speaking task” (Anatomy functioning may differ on tasks such as speaking and swallowing).
• “ Presents with pitch range WNL.”
• “Presents with vocal quality WNL.”
• “ Presents with apparent vocal fold adduction WNL on throat clearing and coughing tasks.”
• “ Presents with adequate oropharyngeal wall mechanotactile recognition abilities.”

 

Cranial Nerve XII: Hypoglossal

• The Hypoglossal Nerve emerges from the medulla of the brainstem. It has only a motor component.

Motor:

• Supplies all intrinsic and extrinsic muscles of the tongue (except the palatoglossus muscle).

Brief Functional Assessment

• Stick out tongue.
• Move tongue from one corner of mouth to the other corner.

• Do the “around the world” by moving tongue on upper and lower lips in a circular fashion.

• Push tongue against the tongue depressor or therapeutic band at midline and on both sides of mouth.
• Repeat the word “buttercup” several times.

 

Example Report Writing:

• lingual protrusion and bilateral lateralization WNL.
• Presents with general lingual ROM (range of motion) WNL.
• Presents with lingual strength WNL.
• Presents with lingual diadochokinesis abilities WNL.

 

C1 – C3: Cervical Spinal Nerves – Ansa Cervicalis

• Spinal Nerves function similarly to cranial nerves however they emerge from the spinal cord as opposed to the brainstem.
• The infrahyoid muscles (i.e., those that depress and posteriorly displace the hyoid and larynx to complete the swallow – Thyrohyoid, Sternohyoid, etc.) receive innervation from C1 – C3.
• Hyolaryngeal depression after the swallow may be palapated at the thyroid notch during a swallow; however, this functional assessment is conducted best under direct visualization such as videofluoroscopy.

C3 – C5: Phrenic Nerve

• When assessing swallowing function, it is important we are cognizant of respiration and its coordination with swallowing.
• The Phrenic Nerve is a spinal nerve as described above. That is, it is similar to a cranial nerve but it emerges from the spinal cord instead of the brainstem.
• The Phrenic Nerve innervates the diaphragm which is the primary muscle utilized in inspiration. T1 – T12: Thoracic Spinal Nerves
• When assessing swallowing function, it is important we are cognizant of respiration and its coordination with swallowing.
• The Thoracic Spinal Nerves innervate the other muscles of inspiration and expiration .