Actively depressing the tongue appears to be critical in stabilizing the pharynx and soft palate

1

• Activelydepressingthe tongueappearsto be
  criticalin stabilizingthe pharynxand soft
  palate

2

• Conservative treatment
• Tongue tie, figure-8 noseband to increase
  pressure on tongue, reduce caudal movement back
  into pharynx may be helpful
• Mechanical restraints that passively pull the
  tongue forward dont really replace active muscle
  constriction

3

• SDPP
• Surgicaloptions
• Reduce caudalmovementof SP orcranial
  movement of larynx lasers to augment/stabilize
  edges of soft palate
• 60 improvement w/ surgery

4

• Palatal instability
• Upward billowing of soft palate during exercise
  without displacement above epiglottis
• Turbulent airflow, snoring
• More common in older horses
• SPDD more common in younger horses

5

• Laryngeal hemiplegia half paralyzed
• 2nd most common upper respiratory disorder in
  performance horses
• 17 24 race horses
• 40 of sport horses
• Age plus trauma may be contributing factor

6

• Larger breeds
• Rare in small breeds/ponies
• More common in long necked breeds?
• Also seen in draft breeds

7

• Roarer
• Whistling orroaring soundduring exercise
  inspiration
• Cannot makedefinite diagnosison airway
  noisesalone

8

• Normal function vocal arytenoid folds close
  (adduct) during swallowing, open (abduct) during
  respiration to maximize airflow

9

• Vocal arytenoid folds are innervated by recurrent
  laryngeal branch of vagus nerve (CN X)
• Right VF by right recurrent laryngeal nerve
• Left VF by left recurrent laryngeal nerve
• Left affected much more than right

10

• Vagusnervecoursesdownneck,branchesin
  cranialthorax
• Vagal trunks to heart and viscera

11

• Recurrentlaryngealnerve(a branchof
  vagusnerve)travelsback upthe neck to
  innervate the muscles of the pharynx and larynx

12

• The only muscles that open the glottic cleft of
  the larynx by abducting the vocal arytenoid folds
  are the left and right dorsal cricoarytenoideus
  muscles, innervated by the left and right
  recurrent laryngeal nerves, which are branches of
  CN X (vagus)

13

• Trauma or disease to recurrent branch causes
  partial or complete loss of muscle function to
  dorsal cricoarytenoideus muscle of arytenoid
  vocal folds of larynx
• Arytenoids fail to open during respiration

14

• Failure to open during respiration
• Decreased tracheal diameter
• Decreased ventilation
• Runs out of gas at finish line

15

• How does damage to RLN occur?
• Perivascular injection to jugular vein
• Trauma
• Injury
• Surgical procedures
• Guttural pouch mycosis
• Retropharyngeal abscesses /mass
• Toxicity

16

• Most common etiology idiopathic
• UNKNOWN cause of neuropathy

17

• Why left more than right?
• RLNs paired structures (there are two of them)
• Left nerve longer, located more ventral, away
  from center axis of cervical rotation than right
  nerve
• More tension? More prone to trauma?

18

• Laryngeal function is graded on a scale of I IV
  based on movement and degree of abduction of
  arytenoids/vocal folds during swallowing
• Grade I normal and symmetrical movement
• Grade IV - total paresis (no movement)

19

• Most horses presented for roaring are Grade III
• Multiple sub-categories, based on degree of
  collapse during exercise

20

• Diagnosis
• Atrophy of external musculature to larynx
• Standing endoscopy
• Slap test
• Endoscopy during exercise

21

• Treatment
• Treat any underlying disease
• Surgery
• Tie back
• Suture arytenoid cartilage to permanantly open
  glottic cleft

22

• Success rate following surgery
• 75 return to racing
• 50 of those improved performance and racing
  times
• Back stretch belief you have to wait for full
  paralysis before attempting sx
• Not true no benefit to delay
• Success rate approaches 86 93 in sport and
  draft horses

23

• Surgical complications
• Arytenoid/vocal folds cannot close during
  swallowing
• Coughing during eating
• Chronic tracheitis
• Higher risk of aspiration pneumonia
• Infection, suture failure
• Prognosis tends to be poorer in right laryngeal
  paralysis than left

24

• Partial arytenoidectomy to surgically remove
  dysfunctional tissue
• Usually a secondary surgery if original tie-back
  procedure fails
• Prognosis becomes guarded to poor for return to
  racing performance
• Newer laser sx procedures Univ of Penn improving
  prognosis
• 60 80 successful return to racing