1) The document describes two cases of laryngeal dysfunction in horses. Case 1 involves left laryngeal hemiplegia, while Case 2 involves epiglottic entrapment. 2) For Case 1, a prosthetic laryngoplasty surgery was performed under general anesthesia to create abduction of the left arytenoid cartilage using sutures. For Case 2, a standing laser surgery was used to perform an axial excision of thickened aryepiglottic tissue causing the entrapment. 3) Both surgeries aimed to improve airflow and resolve the underlying laryngeal issues. Post-operative care and monitoring was provided for several weeks to manage pain and ensure healing. The prognosis

1. LARYNGEAL DYSFUNCTION:
1. Left Laryngeal
Hemiplegia
2. Epiglottic Entrapment
Dec.
Dane Tatarniuk, DVM
12, 2012

2. ANATOMY & FUNCTION

3. Equine Larynx
 Anatomy
 Paired arytenoids
 Epiglottis
 Thyroid
 Cricoid

4. Equine Larynx
 Intrinsic muscles
 Move laryngeal
cartilages in relation to
each other
 Cricoarytenoideus
dorsalis – abduction of
arytenoids & tensing
of vocal folds
 Thyroarytenoideus, ar
ytenoideus
transversus, cricoaryte
noideus lateralis –
adduction of
arytenoids

5. Equine Larynx
 Arytenoid Function
 Situated on either side of cricoid
 Composed of hyaline cartilage
 Cricoarytenoid joint – diarthrodial
 Facilitates adduction & abduction movement
 3 processes
 Corniculate, cuneate & muscular process
 Arytenoids adduct (close) during swallowing reflex
 Arytenoids abduct (rima glottidis dilates) fully at high-
intensity exercise to maximize airflow
 Abduction of arytenoid counter-acts increasing negative
inspiratory pressure (which acts to adduct arytenoids)
 Decreased airflow  hypoxemia  hypercarbia 
metabolic acidosis  musculoskeletal fatigue  poor
performance

6. Equine Larynx
 Epiglottis Anatomy & Function
 Triangular structure with apex
pointing rostral
 Attached to thyroid via
thyroepiglottic ligament
 Composed of elastic cartilage
 Normally situated above soft palate
 Soft palate against epiglottic base
 Scallop appearance laterally
 Vascular pattern dorsally
 Flips caudally to cover rima glottis
during swallowing

7. CASE #1

8. Case #1- Signalment
 7 years old
 Gelding
 Canadian Warmblood
 Discipline: Eventing

9. Case #1 - History
 Tiring with exercise
6 month history
 Noise
 Less of a concern
 Evaluation by rDVM
 Standing endoscopy
 Laryngeal paralysis
 Referred to UMEC

10. Case #1 – Diagnostics
 Normal vital parameters
 Resting
endoscopy, standing, un-
sedated
 Left laryngeal hemiplegia
 Grade 4
 Recurrent laryngeal
neuropathy
 No other concurrent
upper airway

11. Left Laryngeal Paralysis
 Neurogenic atrophy of intrinsic laryngeal
musculature (94% of cases)
 Loss of abductor and adductor arytenoid
function
 Cricoarytenoideus dorsalis muscle
 Progressive loss of function (not immediate)
 Other causes:
 Perivascular damage from IV injection, guttural
pouch mycosis, neck trauma, abscessation of
head/neck, neck neoplasms, organophosphate
toxicity, plant poisoning, hepatic

12. Laryngeal Paralysis Grades
 Grade 1
 Arytenoid movements synchronous & symmetrical
 Full adduction attained
 Grade 2
 Arytenoid movements are asynchronous or
asymmetrical at times
 Full adduction attained
 Grade 3
 Arytenoid movements are asynchronous or
asymmetrical
 Full adduction can not be attained
 Grade 4
 Complete immobility of arytenoid cartilage

13. Case #1 - Therapy
 Recommendation:
 Prosthetic Laryngoplasty
 “Tie Back”
 Prosthesis between arytenoid and cricoid
 Create abduction
 Provide adequate airflow but not allow aspiration
 +/- ventriculectomy via laryngotomy
 Eliminate noise, further stabilize airway
 Can be used as sole procedure in draft horses
 +/- ventriculocordectomy via standing laser
endoscopy
 2 cm crescent wedge of tissue removed from leading
edge of vocal fold

14. Case #1 - Therapy
 Pre-operative medication
 Potassium penicillin, 22,000iu/kg, IV
 Gentamicin, 6.6mg/kg, IV
 Phenylbutazone, 4.4mg/kg, IV
 Tetanus toxoid, IM
 General anesthesia
 Small endotracheal tube
 Left lateral recumbancy
 Neck extended
 IV catheter low in left jugular vein or on right side
 5L fluid bag under proximal neck
 Help extend throatlatch upwards

15. Case #1 - Therapy
 Surgery
 ~10cm cranial-caudal incision, cranial extent
starting at left ramus of mandible
 Ventral and parallel to lingual-facial vein
 Blunt dissect lingual-facial vein from omohyoideus
muscle
 Avoid pertinent nerves and vasculature
 Dissect between sternocephalicus and
cricothyroideus muscles
 Follow plane of dissection under lingual-facial
vein until expose larynx & associated laryngeal
musculature

16. Case #1 - Therapy
 Palpate caudal aspect of cricoid
cartilage & muscular process of left
arytenoid cartilage
 Assistant retracts upwards
 Suture
 #5 Ethibond (Polyester)
 Alternatives: Stainless steel
wire, nylon, polyethylene
 Pass suture through cricoid cartilage
(x 2)
 Walk needle off caudal aspect of cricoid
 Stay axial to dorsal sagittal ridge
 „Notch‟ of cricoid cartilage
Auer & Stick

17. Case #1 - Therapy
 Intra-operative endoscopic exam
 Ensure suture does not penetrate laryngeal
mucosa
 Tunnel leading edges of suture
 Under cricopharyngeus muscle
 Pass suture in caudal-medial to cranial-
lateral direction through muscular process
(x2)
 Engage spine, not tip, of muscular process
 Tie cranial suture strand to caudal strand
(x2)
 Assess abduction of left arytenoid with
endoscope
 Curvature of corniculate cartilage comes into
contact with pharyngeal wall
 Close musculature & skin routinely
 Stent bandage Auer & Stick

18. Case #1 – Post Op Care
 Post operative medication
 Potassium penicillin, 22,000iu/kg, IV, QID, 3 days
 Gentamicin, 6.6mg/kg, IV, SID, 3 days
 Phenylbutazone, 2.2mg/kg, PO, BID, 5 days
 Trimethoprim sulfa, 15mg/kg, PO, BID, 5 days
 Fed on the ground
 Exercise
4 weeks of stall rest then 2 weeks of small
paddock
 Return to exercise at 6 to 8 weeks post-op

19. Case #1 – Recheck Endoscopy
 24 hour recheck
endoscopy
 Maintained abducted
position
 Estimate 60 to 70% of
rima glottidis area
attained
 4 week follow up
 Horse doing well

20. Prognosis
 Success depends on use of horse and
measurement of success
 Between 50% to 70% of horses have improved
performance following laryngoplasty surgery
 Success better in horses not intended to race
 Decreased noise production not a measure of
improved airway function

21. Complications
 Complications decrease prognosis
 Dysphagia
 Bilateral nasal discharge
 Feed, water, saliva
 Aspiration pneumonia
 Chronic coughing
 Incisional infection
 Prosthesis failure
 Chondritis

22. CASE #2

23. Case #2 - Signalment
 11 years old
 Gelding
 Quarter Horse
 Discipline: Mounted
shooting

24. Case #2 - History
 History of intermittent coughing
 Severe coughing fit while at show
 Difficulty eating
 No performance issues
 Attended by rDVM

25. Case #2 – rDVM Diagnostics
 Oral exam: normal
 Head radiographs: normal
 Endoscopy:
 Epiglotticentrapment
 Severe thickening and necrotic ulceration of
aryepiglottic tissue
 Intermittent dorsal displacement of soft palate
 Small ulcer present on the left rim of soft palate

26. Case #2 – rDVM Endoscopy

27. Case #2 – rDVM Therapy
 Procaine Penicillin 22,000iu/kg IM BID
 Flunixin Meglumine 1.1mg/kg PO SID
 Recheck Endoscopy by rDVM:
 At 7 days - continued entrapment with intermittent
soft palate displacement; improvement of the
ulcer
 At 14 days - continued healing of
ulcers, intermittent soft palate
displacement, periodic ventral pharyngeal
collapse

28. Case #2 – Referral
Presentation
 After 14 days medical therapy,
 Improvement in ulcer
 Epiglottic entrapment persists
 Case referred for further management
 Initial endoscopy:
 Confirm epiglottic entrapment with mild ulceration
 Ulceration less compared to previous exam
images
 Ventral aryepiglottic tissue normal with no
ulceration
 No adhesions present between epiglottis and
aryepiglottic tissue

29. Case #2 - Initial Endoscopy

30. Epiglottic Entrapment
 Loose aryepiglottic folds &
subepiglottic mucosa displace
dorsally above the epiglottis
 Exercise intolerance main complaint
usually
 Less commonly coughing, nasal
exudate
 Prevalence 0.9% in Thoroughbreds
 Can be induced by
 Epiglottic hypoplasia
 Aryepiglottic fold inflammation /
swelling
 Chronic cases
 Thickened, fibrous tissue

31. Case #2 - Assessment
 Recommendation: Surgery
 Entrapment unlikely to resolve without
intervention
 Techniques:
 Standing vs. general anesthesia
 Laser axial transection
 Sharp axial transection
 Determined to post-pone surgical
management
 Additional 7 days
 Allow ulcer to heal further prior to surgery

32. Case #2 – Interim
 Medical therapy
 Procaine Penicillin, 22,000iu/kg, IM, BID, 7 days
 Flunixin Meglumine, 0.55mg/kg, PO, BID, 3 days
 Throat Spray, 10cc, PO, SID, 7 days
 Glycerin9cc
 Dimethyl sulfoxide 1cc

33. Surgical Techniques
 Sharp axial division of aryepiglottic tissue
 Curved bistoury knife passed nasally and applied
under endoscopic guidance
 Scalpel transection through laryngotomy or
pharyngotomy
 Axial division allows membrane to retract and
heal in normal sub-epiglottic position
 Tissue sparing, minimize scar tissue
 If thickened or ulcerated
 Can consider taking out triangular wedge
segments of aryepiglottic tissue instead of axial
division

34. Surgical Techniques
 Laser axial division of aryepiglottic tissue
 Contact vs. non-contact
 Tip of laser applied to caudal aspect of tissue (on
midline) and moved rostrally
 10 to 12 watts
 Continue dissection until elastic property of
aryepiglottic tissue causes entrapping membrane
to retract below epiglottis
 Care to not cause collateral damage to
epiglottis, soft palate or pharynx

35. Case #2 – Surgery
 Surgical management
7 days following initial UMEC exam
 21 days following initial rDVM exam
 Pre-operative medication
 Detomidine, 0.02mg/kg, IV, given to effect
 Intranasal lidocaine, 100cc
 Procaine Penicillin, 22,000iu/kg, IM
 Gentamicin, 6mg/kg, IV
 Phenylbutazone, 4.4mg/kg, IV

36. Case #2 - Surgery
 Standing axial excision of aryepiglottic tissue
using diode contact laser

37. Case #2 - Surgery
 Standing axial excision of aryepiglottic tissue
using diode contact laser

38. Case #2 - Surgery
 Rostral edge of
epiglottis appears
hypoplastic
 Blunted prominence
 Residual thickening of
aryepiglottic tissue
present on left edge of
epiglottis
 Contract with time
 Require transection at
future date

39. Case #2 – Post Op Care
 Phenylbutazone, 2.2mg/kg, PO, BID, 5 days
 Procaine Penicillin, 22,000iu/kg, IM, BID, 3
days
 Throat Spray, 10cc, PO, SID, 7 days
 Glycerin7.7cc
 Dimethyl sulfoxide 0.8cc
 Dexamethasone 1.5cc
 Recheck endoscopy 24 hours later
 Confirmed epiglottis free
 Discharged 24 hours after surgery

40. Case #2 – Recheck
 Recheck endoscopy 6 days
post-surgery
 Swellingdecreased
considerably
 Some residual inflammation
present

41. Prognosis
 Reported re-entrapment rate is 5 to 15% with
curved bistoury
 Reported re-entrapment rate is 4% with laser
axial division
 Between 10 to 15% of cases develop DDSP
following un-entrapment
 Complications reduce prognosis:
 Thermal trauma to epiglottis, soft palate
 Lacerations to epiglottis, soft palate
 Cicatrix

42. REVIEW

43. Review: Laser
 Types:
 Neo-dymium : yttrium aluminum garnet (Nd:YAG)
 Gallium aluminum arsinate diode
 Quartz or silica fiber-optics to conduct laser energy
 Human safety - wear protective eyewear
 Specific to wavelength of laser – avoid ocular injury
 Smoke plume
 Xylene, toluene – can be toxic
 If considerable amount produced consider smoke evacuator
 Laser energy converted to thermal energy when
contacting tissue
 Incise, coagulate, vaporize
 Wavelength used influences amount
absorbed, scattered, reflected, transmitted

44. Review: Laser
 Precision incision
 Smaller fiber (400–600μm)
 Small contact area, high power density
 Direct contact with tissue
 10 to 15 watts power
 Non-specific tissue ablation
 Larger fiber (800–1000μm)
 Less specific, do not require direct contact
 Up to 50 watts power
 Can coagulate tissue 5mm deep
 Capable with Nd:YAG, not capable with diode

45. Review: Recent Literature
 Dart, 2009. “Effect of Prosthesis Number and
Position on Rima Glottidis Area in Equine
Laryngeal Specimens.”
 Placed dorsal suture and lateral suture
 dorsally in the cricoid & through the rostral and proximal
muscular process
 1.5 cm lateral to the 1st suture & more caudal and distal in
the muscular process
 When tied independently, no difference in rima glottis
area
 8.51cm2 & 8.46cm2
 When both sutures were tied together, mean area was
greater than when either suture was tied alone
 9.31cm2

46. Review: Recent Literature
 Rakesh, 2008. “Implications of different degrees
of arytenoid cartilage abduction on equine upper
airway characteristics”.
 Used computational fluid dynamics modeling to
measure the effects of different degrees of abduction
 Tested abduction at 100%, 88% & 75% cross
sectional area of rima glottis
 88% cross sectional area optimal
 less reduction in airflow
 less collapsing pressure
 less stress on the repair

47. Review: Recent Literature
 Aitken, 2011. “Epiglottic abnormalities in mature
non-racehorses: 23 cases.”
 8+ years, non race-horses
 Primary complaint
 70% chronic cough
 13% nasal discharge
 Racehorses – exercise intolerance
 57% epiglottic entrapment
 All chronic: thick, ulcerated, and blunted epiglottis
 74% resolution of symptoms with appropriate
management
 24% prolonged medical management (therapy >2 weeks)
due to post-surgical epiglottic inflammation
 9% developed DDSP post-epiglottic surgery

48. Review: Recent Literature
 Lacourt, 2011. “Treatment of Epiglottic Entrapment by
Trans-nasal Axial Division in Standing Sedated
Horses Using a Shielded Hook Bistoury.”
 Reviewed 33 cases using conventional bistoury technique
 2 – laceration of soft palate
 2 – laceration of epiglottis
 Shield hook in 8 standardbreds
 Minimize damage to soft palate, epiglottis
 Mean surgical time = 83 seconds
 6 resolution with one incision
 2 resolution with two incisions
 Inexpensive
 Faster
 Authors opinion: technically easier

49. References
 Aitken, 2011. “Epiglottic abnormalities in mature non-racehorses: 23
cases.” JAVMA 238: 12, 1634 – 1638.
 Dart, 2009. “Effect of Prosthesis Number and Position on Rima
Glottidis Area in Equine Laryngeal Specimens.” Vet Surg 38: 452 –
456.
 Lacourt, 2011. “Treatment of Epiglottic Entrapment by Trans-nasal
Axial Division in Standing Sedated Horses Using a Shielded Hook
Bistoury.” Vet Surg 40: 299 – 304.
 Fulton I: Larynx, in Auer JA, Stick JA (eds): Equine Surgery (ed 4).
Philadelphia, PA, WB Saunders, 2006, pp 592 – 623.
 Palmer SE. “The use of lasers for treatment of upper respiratory
tract disorders” Vet Clin Equine (2003) 19: p245 – 263.
 Rakesh, 2008. “Implications of different degrees of arytenoid
cartilage abduction on equine upper airway characteristics”. EVJ 40
(7), 629 – 635.