Larynx and Pharynx

Question 1

Intrinsic Laryngeal Muscles and innervations (5)

Answer 1

CAD

CAL

Arytenoideus transversus (unpaired)

Thyroarytenoideus (ventricularis and vocalis)

Cricothyroideus

All innervated by RLN - except cricothyroideus = external branch of cranial laryngeal nerve (CN X)

Question 2

Extrinsic Laryngeal Muscles and innervations (5)

Answer 2

1) Cricopharyngeus (CN IX/X)
2) Thyropharyngeus (CN IX/X)
3) Hyoepiglotticus (Hypoglossal)
4) Sternothyroideus (cut during Llewellyn) (C1/C2)
5) Thyrohyoideus (action replaced in tie forward) (Hypoglossal or pharyngeal branch of vagus)

Question 3

Intrinsic pharyngeal muscles and innervations (5)

Answer 3

1) Tensor veli palatini (mandibular br of Trigeminal - T for Tensor and T for Trigeminal)
2) Levator veli palatini - pharyngeal br of vagus
3) Palatinus - pharyngeal br of vagus
4) Palatopharyngeus - pharyngeal br of vagus
5) Stylopharyngeus - glossopharyngeal (dorsolateral pharyngeal wall/roof)

Question 4

Extrinsic Pharyngeal Muscles and innervations (8)

Answer 4

1) Hyoepiglotticus - Hypoglossal nn
2) Sternothyroideus (cut in Llewellyn) - C1/C2
3) Sternohyoideus (ventral midline) - C1/C2
4) Thyrohyoideus (action replaced in tie forward) - pharyngeal br of vagus or hypoglossal
5) Geniohyoideus - Hypoglossal
6) Genioglossus - Hypoglossal
7) Hyoglossus - Hypoglossal
8) Styloglossus - Hypoglossal

Question 5

According to McGivney 2019(EVJ), what effect does OGS position have on the presence of palatal dysfunction?

What is the effect of flushing interval?

Answer 5

Placement rostrally at the level of the GP ostia (position A) increased palatal dysfunction (PI and DDSP) - 63%

Placement caudally rostral to the tip of the epiglottis (position B) decreased palatal dysfunction - 45%

Need to be consistent with scope placement between horses and importantly, sequential examinations of the same horse

No significant effect of flushing interval on prevalence of PD, AAex, MDAF and VFC

Question 6

Function of the hyoglossus and genioglossus muscles

Answer 6

Increase pharyngeal airway size during breathing

Question 7

According to Brandenberger 2018 (Vet Surg) what are the risk factors for penetration of the vestibulum oesophagii

Answer 7

Lack of knowledge of the location of the vestibulum oesophagi in relation to the muscular process of the arytenoid

Increased distance between the suture in the MP and the CAD mm insertion

Question 8

Alternative tx for GP mycosis in horses that do not have haemorrhage described by Watkins 2018

Answer 8

Transendoscopic diode laser salpingopharyngeal fistula

(salpingopharyngostomy)

Question 9

What is this, what breed does it mainly affect and what is the suggested cause

Answer 9

Ventroaxial luxation of the apex of the corniculate process. Usually occurrs left under right but can be other way

Seen following induced swallowing or nasal occlusion, of durinf exercising scope

Typically affects draft breeds

Thought to be due to an abnormally wide transverse arytenoid ligament

Question 10

What % of horses with epistaxis and a dx of GP mycosis will bleed to death if left untreated

Answer 10

50%

Question 11

What degree of arytenoid abduction (as % of total rima XSA) is ideal post laryngoplasty

Answer 11

88% of XSA of rima glottidis

Equates to left-right quotient of 0.7-0.75

Question 12

PO laryngoplasty abduction grading (Dixon scale)

Answer 12

Grades 1-5

Grade 1: Excessive abduction, i.e. the affected arytenoid is close to or at maximal abduction (medial aspect of arytenoid at circa 80–90° to saggital plane), or sometimes even hyper-abducted

Grade 2: A high degree arytenoid abduction (arytenoid at circa 50–80° to saggital plane), i.e. less than complete abduction

Grade 3: A moderate degree of arytenoid abduction, i.e. arytenoid at circa 45° to the saggital plane

Grade 4: A slight degree of arytenoid abduction, i.e. arytenoid is slightly more abducted than the normal resting position.

Grade 5: No detectable arytenoid abduction present

Question 13

What is the expected loss of abduction following traditional laryngoplasty & over what time frame?

Answer 13

1-2 grades over the first 6 weeks PO

See Dixon grading scale of laryngoplasty abduction

Question 14

List short term complications of laryngoplasty (4)

Answer 14

Prosthesis failure (leads to->)

-> Loss of abduction (acute and marked or more gradual and mild)

Incisional complications - Seroma formation (acutely), infection later

Incisional dehiscence

Coughing

Question 15

Mid-long term complications following laryngoplasty (7) and which is most common?

Answer 15

Loss of abduction (remember this can be immediate and sever (dt suture pull through or MP avulsion) or chronic and gradual

Chronic coughing (coughing dt dysphagia is the most common complication)

Dysphagia with or without the nasal return of ingesta

Aspiration pneumonia

Inflammatory airway disease

EIPH

Oesophageal incompetence

Palatal dysfunction

Other forms of dynamic airway obstruction

Arytenoid inflammation/chondritis

Question 16

Treatment options for dysphagia following LP

Answer 16

1) Vocal cord bulking (Ducharmme unpublished)
2) LP removal
3) Tie-forward

Question 17

Why might LP prosthesis removal be effective for tx of coughing/dysphagia following LP removal

Answer 17

Works if there is overabduction & resulting loss of protection of the rima glottidis dt inability to adduct the corniculate process and vocal cord removal

Question 18

RLN tx options (4)

Answer 18

1) Laryngoplasty (still the most common/mainstay)
2) Partial arytenoiectomy (muscular process left in situ, corniculate process removed; subtotal aryetnoidectomy not useful as MP and corniculate process left in place)
3) Re-innervation; nerve muscle pedicle graft or direct C1/C2 nerve transplantation (Rossignol)
4) Unilateral left or bilateral VCE. May get modest improvement in airway dynamics and reduction in noise production. Not suitable as sole procedure for horses exercising maximally (racehorses)

Question 19

Which 2 grading scales can be used to grade laryngoplasty abduction.

Answer 19

1) Dixon - 1-5; 1 being maximal abduction and 5 minimal
2) Russell and Slone - 1-5; 1 being minimal abduction and 5 maximal

Question 20

According to Fitzharris et al 2019 (Vet Surg), what were reasons cited for removal of LP sutures

Answer 20

1) Cough/dysphagia (90%)
2) Draining tract associated with the suture (5%)
3) Persistent noise at exercise (5%)

Question 21

List 4 suture materials that may be used for laryngeal prosthesis

Answer 21

1) Monofilament polyamide (nylon) (Ethilon)
2) Braided polyethylene and polyester (Fibrewire = UHMWPE and polyester jacket)
3) Polyethylene terephthalate (=polyester; Ethibond)
4) Stainless steel

Question 22

Mechanisms by which LP may cause coughing/dysphagia (3)

Answer 22

1) Arytenoid over abduction and loss of protection of rima glottidis dt VC removal. Frequently cited but controversial as coughing/dysphagia are seen in horses with poor/no abduction as well as those with good or excessive.
2) Local fibrous tissue response may compromise local innervation and muscle function associated with deglutition
3) Penetration of the oesophageal adventitia/vestibulum oesophagi (Brandenberger 2018 VS)

Question 23

Indications and timing for laryngoplasty prosthesis removal

Answer 23

Main indication is persistent coughing/dysphagia

Should be reserved for cases non-responsive to medical management and should be delayed until at least 60d PO to allow time for fibourous reaction around MP and prevent loss of abduction after prosthesis removal

Question 24

Outcomes following LP suture removal for tx of cough/dysphagia reported by Fitzharris et al VS 2019

Answer 24

66% resolution of CSs

9% improvement

25% unchanged

75% returned to some level of ridden exercise

No effect of timing on implant removal on outcome

Question 25

% of horses tx with LP for RLN requiring LP removal according to Fitzharris et al 2019 VS

Answer 25

3.5%

Question 26

Potential intra-op complications of laryngoplasty

Answer 26

Haemorrhage (NB br. of the linguofacial vein that enters OH mm may req. tying off)

Needle breakage (usually during placement through the MP)

Laryngeal or nasopharyngeal penetration (usually during placement through caudal aspect of the cricoid)

Question 27

Indications for partial arytenoidectomy (2)

Answer 27

1) Advanced arytenoid chondritis
2) Failed laryngoplasty

Question 28

What layers are incised to perform a laryngotomy?

Answer 28

Skin

SQ

Sternohyoideus (separated on midline)

Cricothyroid membrane

Question 29

Describe the steps described by Gray et al (VS 2019) for standing partial arytenoidectomy

Answer 29

1) Standing laryngotomy (with trach in place), 18g needle and endoscopic guidance to ensure incision in CT membrane was in correct position
2) VCE (if not prev performed)
3) Dorsally based U shaped incision in the mucosa of the axial aspect of the corniculate process from rostral to caudal (upto level of MP)
4) Some mucosal periosteal elevation from corniculate process
5) Transection of muscle attacnments from lateral (CAL), dorsal (arytenoid transversus) and medial (vocalis mm) aspects of corniculate process
6) Rostromedial traction to facillitate caudal muscular attachement transection
7) Transection and removal of corniculate process and attached mucosa
8) Removal (rongeurs) of protruding cartilage or redundant mucosa (metz)
9) No mucosal or incisional closure

Question 30

What was the main PO complication following standing arytenoidectomy reported by Gray et al (VS 2019)?

How was it treated and was treatment successful?

Answer 30

Granuloma formation occurred in 3/9 (33%) with endoscopic f/u

Treated with transendoscopic diode laser resection in 2/3- recurred in both -> tx repeated and was successful in 1/2

2 had permanent tracheotomies

Question 31

Summary of outcomes following partial arytenoidectomy performed standing reported by Gray et al (2019 VS)

Answer 31

All survived

9/12 (75%) w f/u returned to some athletic use without respiratory noise, 2 returned to some athletic use with noise during exercise that was reduced vs pre-op levels, and 1 horse continued to be used as a broodmare.

9/12 (75%) horses w f/u returned to intended exercise, 2 exercised at lower level than prev & 1 continued to be a broodmare - these were largely driving horses (deaft breeds) which may explain compartive high success rate vs other studies - 45-80% return to racing for TBs

Question 32

Damage to which 2 extrinsic laryngeal/pharyngeal muscles may have a role in development of epiglottic retroversion

Answer 32

Hyoepiglotticus

Geniohyoideus

Question 33

What is this condition, how is it diagnosed and what are the clinical features

Answer 33

Epiglottic retroverion

Need exercising endoscopy, resting scope typically normal.

Clinical features include exercise intollerence, abnormal respiratory noise (inspiratory grunt), can have dyspnoea

Poll flexion may be a contributing or exacerbating factor

Question 34

Possible tx options for epiglottic retroversion

Answer 34

1) Conservative (rest/anti-inflammatories)
2) Epiglottic augmentation with polytetrafluroethylene paste
3) Resection of the subepiglottic tissue

All of the above have been met with limited success

4) Epiglottopexy - 2 cases reported by Curtis and Parente (VS2019) both with good outcomes

Question 35

Describe the steps in the surgial procedure for epiglottopexy reported by Curtis and Parente 2019 (VS) for epiglottic retroversion

Answer 35

1) GA dorsal with nasotracheal intubation, speculum and scope placed into the oropharynx & broncho-oesophageal forceps used to position the epiglottis within the mouth
2) Ventral midline skin incision from cricoid to basihyoid, & separate omohyoideus on midline to expose larynx
3) Blunt dissection continued rostral and dorsal to expose the rostroventral thyroid and the base of the epiglottis to create a ledge of thyroid extending rostral and ventral to the base of the epiglottis
4) No 5 polyester suture (Ethibond), passes:
a) through the thyroid in a dorsal to ventral direction 0.5cm to the right of midline and 1cm caudal to the most rostral aspect of the ventral wing of the thyroid, which is just rostral to the level of the articulation of the thyroid and epiglottic cartilages.
b) Then passed in a horizontal plane from right to left, dorsal to the hyoepiglotticus muscle within the fascia between the muscle ellies and the epiglottic cartilage just rostral to the rostral edge of the thyroid cartilage.
c) The suture was then passed in a dorsal to ventral direction through the rostral aspect of the left wing of the thyroid cartilage and again through the fascia ventral to the epiglottis
4) Visualise suture placement via scope in the mouth to ensure mucosa not penetrated
5) Suture tightened such that the epiglottis could be seen to have ventral tension without distorting its horizontal position
6) Close in 3 layers OH mm (3-0 polyglactin 910), SQ (pg910) and skin (polyglycaparone – monocryll 20

Question 36

Outcome reported by Curtis and Parente (VS 2019) for epiglottopexy in the tx of epiglottic retroversion?

Answer 36

2 cases reported with successful outcomes.

No PO complications and both returned to racing at previous class (1 stdbd and one prev unraced TB)

Question 37

Describe the Havemayer grading scale for laryngeal function at rest

Answer 37

1. All arytenoid cartilage movements are synchronous and symmetrical and full arytenoid cartilage abduction can be achieved and maintained.
2. Arytenoid cartilage movements are asynchronous and/or larynx is asymmetric at times but full arytenoid cartilage abduction can be achieved and maintained.
3. 1 Transient asynchrony, flutter or delayed movements
4. 2. There is asymmetry of the rima glottidis much of the time due to reduced mobility of the affected arytenoid and vocal fold but there are occasions, typically after swallowing or nasal occlusion when full symmetrical abduction is achieved and maintained.

3 Arytenoid cartilage movements are asynchronous and/or asymmetric. Full arytenoid cartilage abduction cannot be achieved and maintained.

3. 1 There is asymmetry of the rima glottidis much of the time due to reduced mobility of the arytenoid and vocal fold but there are occasions, typically after swallowing or nasal occlusion when full symmetrical abduction is achieved but not maintained.
4. 2. Obvious arytenoid abductor deficit and arytenoid asymmetry. Full abduction is never achieved
5. 3 Marked but not total arytenoid abductor deficit and asymmetry with little arytenoid movement. Full abduction is never achieved
6. Complete immobility of arytenoid and ipsilateral vocal fold

Question 38

Describe the exercising grades for recurrent laryngeal neuropathy

Answer 38

A-C scale (earlier scale by Rakestraw 1991)

A Full abduction of the arytenoid cartilages during inspiration.

B Partial abduction of the affected arytenoid cartilages (between full abduction and the resting position).

C Abduction less than resting position including collapse into the contralateral half of the rima glottidis during inspiration.

A-D scale - adapted by Rossignol 2019

A - full abduction

B - partial abduction between full and resting position

C - abduction less than resting position

D - collapse across midline to the contralateral side

Question 39

Which 2 dynamic URT obstructions are commonly seen with RLN?

Answer 39

1. Bilateral vocal fold collapse
2. Right sided MDAF

Question 40

What methods can be used to reduce the risk of ventral laryngeal cicatrix (& possibly decrease risk of PO dysphagia following LP) when performing bilateral VCE?

Answer 40

1. Use scalpel rather than laser
2. Leave 5mm cord ventrally on each side.
3. Suturing the edge of the fold to the axial border of the ventricle
4. Only removing the dorsal half of the right vocal fold
5. Performing a right vocal cordotomy (rather than cordectomy) to induce scarring in the right vocal fold and thus reduce the severity of right VFC

Question 41

Describe the main findings of Barakzai et al (EVJ 2019) WRT noise production following unilateral left VCE in horses with RLN

Answer 41

1. Horses with grade B laryngeal function and VFC make less noise & subjectively have a narrower band of abnormal energy in the F2 formant vs grade C horses
2. There was significantly less noise in the F2 formant post vs pre-operatively; which was no significantly different between grade B and C horses. NB a good proportion of horses still made an audible noise PO clincially
3. Horses with most noise in the F3 formant had the most unstable larynges
4. In horses with grade C laryngeal function, bilateral VFC and right-sided MDAF are extremely common. Ongoing noise PO may be attributed to dynamic collapse of these structures- 6/7 grade Cs had bilateral VC prolapse & 5/7 had right sided MDAF - which remained the same PO and 1/3 grade B had R VC prolapse PO
5. Study suggests that in some cases, laser VCE can stabilise a previously unstable arytenoid cartilage to some degree.
6. Unilateral laser VCE is not necessarily a useful tx for horses w grade C laryngeal function; esp if noise resolution is the goal of sx - Bilateral VCE or LP plus VCE & right AEF resection may be a better option for horses with grade C RLN

Question 42

5 grade laryngeal grading described by Geoff Lane

(shouldn’t be used post 2003 following Havermayer concensus 7 point grading)

Answer 42

Grades 1 and 2 are considered clinically normal and grades 3 and above are considered abnormal.

Grade 1: All movements, both adductory and abductory are synchronized at rest and after exercise.

Grade 2: All major movements are symmetrical with a full range of abduction and adduction. Transient asynchrony, flutter or delayed or biphasic abduction may be seen.

Grade 3: Although the left arytenoids is still capable of full abduction, activity is generally reduced on the left compared with the right with periods of prolonged asymmetry, particularly during quiet movements. Full bilateral abduction can be stimulated transiently by partial asphyxiation using nostril closure but it is not sustained.

Grade 4: The left arytenoids is no longer capable of full abduction and during adduction compensation by the right arytenoids crossing the midline may be evident. Asymmetry is marked but some residual movements are present.

Grade 5: True hemiplegia, ie. there is a complete absence of active movement on the affected side and no response to the ‘slap’ test will be provoked.

Question 43

6 grade larygeal endoscopic resting grading system developed by Paddy Dixon (grades 0-5)

(Shouldn’t be used post Havemayer concensus 7-point grading)

Answer 43

0 (Normal) perfect synchrony of arytenoid movement, and symmetry of appearance, full bilateral arytenoid abduction achieved and maintained (eg during nasal occlusion on excitement).

1 (Normal) asynchronous arytenoid movements, ± presence of arytenoid or vocal shiver but full symmetrical arytenoid abduction achieved and maintained.

2 (Mild paresis) slight arytenoid asymmetry, incomplete arytenoid abduction or complete but transient abduction ie unable to maintain full abduction.

3 (Moderate paresis) obvious arytenoid abductory deficit and arytenoids asymmetry.

4 (Severe paresis) marked but not total arytenoid abductory deficit and asymmetry, very little arytenoid movement.

5 (Total paresis [hemiplegia]) no arytenoid movements detectable.

Question 44

Calculate the sensitivity, specificity, PPV and NPV for use of resting endoscopy to predict dynamic laryngeal collapse reported by Elliot et al (2019 EVJ)

Answer 44

Sensitivity = 74.4%

Specificity = 95.1%

PPV = 85.6%

NPV = 90.5%

Diagnostic odds ratio 56.8

Question 45

What were the conclusions of Elliot et al (EVJ 2019) WRT use of resting laryngeal grade as a predictor for exercising layngeal function?

Answer 45

1. Overall resting endoscopy is a useful tool for predicting dynamic laryngeal movements with sensitivity of 74.4%, specificity of 95.1%, PPV of 85.6% & NPV 90.5%.
2. In a subset of horses however, resting grade not reflective of dynamic situation; 9.5% of those with normal resting grades had evidence of dynamic collapse, and 16% of resting grade 3’s were exercising A
3. Generally progressive increase in the proportion of horses with dynamic collapse as subgrade (within grade 3) worsens. General trend is obviously for worsening resting grade to be assoc with worsening exercising grade, but not always the case and highlights importance of exercising endoscopic exam

Question 46

What did McGivney et al (EVJ 2019) find WTR serial resting/exercising endoscopic exams of TBs in training?

Answer 46

• High degree of variability between examinations for most conditions, esp PI and epiglottic grade at rest
• AA at rest was the most variable condition between exams WRT magnitude of grade changes that occurred as time between examinations increased, with no distinct pattern of improvement or deterioration over time
• AAexercise was the most consistent between examinations with grades/appearance either remaining unchanged or becoming more severe - with 11% deteriorating over time

Question 47

According to McGivney et al (2019 EVJ), what conformational features were most likely to be associated with having, and not having, evidence of RLN on overground endoscopy

Answer 47

Factors assoc with presence of RLN

1. ↑Withers height (this was the predominant feature & key finding of the study)
2. ↑ ventral neck length
3. ↑ age

Factors assoc with not having RLN (generally weaker associations and more variation among controls)

1. ↑ neck circumference
2. ↑ inter-mandibular distance
3. ↓ body size (this is not that clear in the paper)

Question 48

Suggested grading for palatal dysfunction (from Allen and Franklin 2013)

Answer 48

1) Stable: when no movement or lifting of the soft palate is observed
2) Palatal instability with no rima glottidis obstruction - assigned when SP lifts up to the level of the base of the epiglottis but the rima glottidis is not obscured
3) Palatal instability with rima glottidis obstruction - assigned when the soft palate lifts so that the rima glottidis becomes obscured

The soft palate of horses with palatal instability can be described as either flaccid, billowing dorsally in front of the epiglottis or billowing dorsally either side of the epiglottis. The presence or absence of a sling appearance to the ventrolateral pharyngeal walls at the level of the GP ostia .

The caudal soft palate assessed as to whether a concave appearance was present. Concave depressions can be graded subjectively as absent, small or large on both inspiration and expiration. Large depressions were assigned when they extended across the width of the soft palate either side of the midline palatinus muscle.

Question 49

Epiglottic grading at exercise (from Allen and Franklin 2013)

Answer 49

1) Convex epiglottic appearance: the epiglottis maintains a convex shape during exercise; typically only the its tip is in contact with the soft palate.
2) Flattened epiglottis: the epiglottis loses its convex shape and appears to lie flat or slightly concave on the surface of the soft palate, but the tip of the epiglottis remains ventral to the base.
3) Tipped up: when the epiglottis has a flattened or concave appearance & during inspiration the tip of the epiglottis is at the same level as or higher than its base.

Question 50

Grading for MDAF

Answer 50

(None)

1. Mild - axial collapse of the AEF; however, the folds remain abaxial to the vocal cords
2. Moderate - axial deviation of the AEF < halfway between the vocal cord and midline
3. Severe - collapse of the aryepiglottic folds > halfway between the vocal cord and midline

Question 51

What is the apparent relationship between endoscope position and MDAF grade observed by McGivney et al (2019 EVJ)?

Answer 51

MDAF appeared to be influenced by interactions between peak velocity and scope position, and peak velocity and flushing interval, but not individually by either; horses examined in position A (at the level of the GP ostia)are more likely to have more severe MDAF grades as velocity increases. Although there was no clear pattern making it possible this was due to random chance

Question 52

What were the key findings of Hackett et al (EVJ 2019) WRT OGS of draft breeds presenting with abnormal resp noise +/- poor performance?

Answer 52

1. 92% horses had URT abnormalities; complex in 62%
2. Good correlation with resting and exercising laryngeal grades; with more severe arytenoid cartilage collapse at exercise for the same resting grades vs TBs and other sports horses.
   All grade 1s were grade A. 55% of grade 2’s had collapse at exercise. All 3 and 4s had collapse at exercise; All but 1 grade 4 horse had exercising grade C & grade 3 horses were 50:50 B:C
3. Lower %/incidence of PI/iDDSP in draft breeds vs TB and performance horses w similar presenting complaints - (14/50 had PD) & lack of observation of circumferential, lateral wall or dorsal pharyngeal collapse abnormalities which is prevalent in non-racing performance horses who work with similar head positions to working draft breeds
4. Combining resting and exercising exam allowed for more full dx evaluation; highlights the importance of OGS in these horses where many issues would go un-dx if not
5. High incidence of upper oesophageal incompetence than expected - dt intervention incl LP and arytenoidectomy? Likely but also present in 3 horses w no prev sx; part of the dz process rather than the tx?
6. Epiglottic deviation observed here in 1 case has not yet been reported elsewhere - unknown aitiology

Question 53

What did McLellen et al (2019 EVJ) find regarding inter and intra observer agreement for laryngeal function grading of 2yr old TB sales videoscopes?

Answer 53

Arytenoid function grading agreement varied depending on the grading scales chosen and the nature of the statistical agreement criteria imposed.

The ability of veterinarians to exactly agree with each other and themselves on AFG assignment, was low. Agreement levels were better for all veterinarians when the ordinal Havemeyer scale was reclassified dichotomously (into does or doesn’t meet the condition of sale).

Specifically:

• Inter-observer agreement was GOOD for dichotomous grading (does or doesn’t meet sales conditions)
• Inter-observer agreement for ordinate (Havemayer) grading was fair for unweighted kappa analysis and moderate for weighted kappa stastical analysis
• Intra-observer agreement for ordinate grading was fair for unweighted analysis and good for weighted kappa analysis

Question 54

Label the diagram of the ventral aspect of the larynx and hyoid

Answer 54

B - stylohyoid

D - ceratohyoid

E - basihyoid and lingual process

F - thyrohyoid

G - thyroid

i - ceratohyoid mm

j - transverse hyoid mm

Question 55

Main findings of Shaw and Rosonowski (2019 TVJ) WRT racing performance following surgical correction of EE with an intra-oral technique UGA

Answer 55

1. No sig difference between racing performance of all case horses post-surgery and their matched controls when treated with the oral technique UGA - no sig diff in number of starts, wins or placings
2. Seemingly beneficial effect of surgery on racing performance; 20/32 horses raced with a dx of EE and post-correction; 14/20 won or placed PO vs 1/20 pre-op
3. 5/32 had complications incl thickening/adhesions; 3 had a 2nd surgery. All returned to racing - 2 won and all were placed
4. Provides evidence that horses treated conservatively are likely to race poorly, and the intra-oral sx technique may benefit performance. Techniqeu has low complication risk, is associated with improvement in race-day performance, and long term post-surgical race performance comparable to control horses

Question 56

Return to racing % reported for QHs undergoing prosthetic LP for RLN (Kreuger 2019 VCOT)

Answer 56

• Overall return to racing was 85% in cases and 83% in controls
• No difference in pre-op grades on return to racing - 89% gII, 85% GIII and 82% GIV, although GII pre-op horses had the best performance indices PO
• Number of racing starts, racing earnings, and career longevity did not differ between case and control horses; however, case horses had a higher postoperative PI vs controls (but not higher than themselves pre-op … this calls into question the need for the procedure, if they cope with RLN then do they need sx?)
• Performing concurrent procedures or getting PO complications didn’t significantly decrease odds of return to racing
• No PO exercising endoscopy to see improvement in airway function, based on PI only which were pretty good pre-op anyway. QHs likley to cope better since they race fast and over v short distances

Question 57

Possible mechanisms of coughing post tie-back

Answer 57

• Tracheal aspiration is the most commonly reported cause of coughing
• Traction on the isthmus of the oesophagus has been proposed as a cause of coughing
• Tracheal aspiration from esophageal reflux dt damage to the cranial esophageal sphincter during laryngeal surgery has also been reported

Question 58

What 3 methods can be used to expierimentally induce DDSP

Answer 58

1. Bloking pharyngeal branch of the vagus nerve
2. Thyrohyoideus model
3. Blocking hypoglossal nerve

Question 59

Give 2 advantages of standing vs traditional laryngoplasty

Answer 59

1. Avoids GA risk
2. Better assessment of intra-op abduction

Question 60

4 possible reasons for dysphagia post tie-back

Answer 60

1) Excessive abduction
2) Inflammation/fibrosis of the oesophagus dt perr-sx inflammation of suture penetration
3) Failure of the contralateral arytenoic/cord to compensate for L sided overabduction
4) Excissive fibrosis from the hemi-larynx dt surgical scarring deviating the larynx on operated side so that epiglottis can’t cover the rima during swallowing

Question 61

Structures originating from the 4th branchial arch

Answer 61

Cricoid cartilage

Thyroid cartilage

Cricopharyngeus

Thyropharyngeus

Cricothyroid muscle

Question 62

Structures originating from 6th branchial arch

Answer 62

Aryternoids

CAD

CAL

Thyroarytenoideus (ventricularis/vocalis)

Arytenoideus transversus

Question 63

Tx options for laryngeal dysplasia (4-BAD)

Answer 63

Depend on OGS findings

Laryngoplasty not usually poss dt dorsal extension of throid making muscular process inaccessible.

Usually tx w VF resection. RDPA can be tx w laser thermoplasty. Partial arytenoidectomy or permanent tracheostomy also options

Question 64

Diagnostic features of laryngeal dysplasia

Answer 64

PE: palpable laryngeal abnormalities incl gap between thyroid and cricoid, MP may not be palpable dt dorsal extension of thyroid lamina

ENDOSCOPY: most common features are RDPA (51%) & R sided pariesis (65%). W OGS, often see VFC, RDPA, MDAF, R sided pariesis

RADS: gas in upper oesophagus (care if sedated), RDPA - soft tissue opacity rostral to corniculate processes.

US: dorsal extension of thyroid lamina past MP (on trumpet view). Absent cricothyroid articulation