Chapter 45 - Nasopharynx disorders in foals

Question 1

What are the nasopharynx congenital problems in foals ?

Answer 1

choanal atresia
nasopharyngeal disfunction
cleft palate

Question 2

diagnosis

Answer 2

Figure 1—Endoscopic views of the right choana in a foal with
bilateral choanal atresia before and after surgery. A—Image
obtained before surgery. Notice the imperforate oropharyngeal
membrane covering the choanal opening. B—Image obtained 3
days after surgery. A diode laser was used transendoscopically
to create an opening through the buccopharyngeal membrane
that covered the choanal openings. Pre- and postsurgical findings
for the left choana were similar. Arrows show edge of ethmoid
recess visible at the top of each image. JAVMA 2006

Question 3

choanal atresia is a failure of

Answer 3

congenital abnormality associated with failure to resorb this BUCCONASAL MEMBRANE this embryonic membrane that separates oral and nasal cavities

Question 4

what are the clinical signs of choanal atresia?

Answer 4

Bilateral –> foal’s death (unless emergency tracheostomy)
Unilaterally –> loud respiratory noise
exercise intolerance (asymptomatic at rest)
membrane obstructs caudal nasal passage –> asymmetric nostril airflow

Question 5

Diagnosis of choanal atresia is made with

Answer 5

– scope, skull XR +/- contrast, CT

Question 6

foals with unilateral choanal atresia should be allowed to grow untreated until what age?

Answer 6

1 year old

Question 7

why do you wait until 1 year old for surgical repair of unilateral coanal atresia?

Answer 7

• larger nasal cavity facilitates Sx
• decrease postop fibrosis
• reduced diameter of choana
• Postop nasal stent or nasal septum resection is avoided
• Allows the procedure to be performed less invasively under endoscopic control with the animal standing

Question 8

what is the surgical preference according to AUER authors for correction of choanal atresia?

Answer 8

Authors’ preference = incise membrane using endoscopic control and place a stent in the nostril to prevent stricture

Question 9

what are the 3 surgical approaches?

Answer 9

1) laser transendoscopically
2) choana is osseous - nasal flap in C-shape or S-shape incision
3) via laryngotomy resection of membrane

Question 10

Describe laser procedure for choana atresia

Answer 10

Local anaesthesia + 10ml of 0.15% phenylephrine
Outline of the chonanal membrane is identified using equine laryngeal forceps
600-μm laser (15W) – cauterize vessels and incise membrane  two lines of incision perpendicular to each other that cross at the center of the choanal membrane
Cross incision is made (membrane is vascular), local pressure to stop the bleeding may be needed – nasotracheal tube is passed through the membrane into the nasopharynx - cuff is inflated - pressure - hemostasis
Tube removed and each flap resected with the aid of laryngeal forceps (tension on flaps), NSAIDs 5d

Question 11

When choanal membrane is osseous or bilateral describe surgical procedure of C or S-incision

Answer 11

• Nasal flap is required to gain access to the caudal nasal passage
• Choanal membrane (bone) is resected + part of the nasal septum, using a nasal bone flap
• GA lateral recumbency tracheostomy ET tube
• C-shaped (unilateral) or S-shaped (bilateral) incision - nasal bones starting at the level of the medial canthus of the eye and extending rostrad to approximately the middle of the nasal cavity (near level of infraorbital foramen)
• Periosteum incised on midline, extending laterally to nasomaxillary suture, (care stay at least 1 cm medial to infraorbital canal)
• Nasal bone flap w osteotome @ 45-degree angle to create a ridge for the bone flap to rest on after Sx
• Bone flap is made in the shape of the periosteal incision
• Nasal mucosa excised, and choanal membrane resected, along with the caudal nasal septum if necessary
• Area packed with sterile gauze, which exits the nostril and is sutured to the false nostril.

Question 12

Describe the approach through laryngotomy

Answer 12

• If necessary to operate on a young foal
• Membrane is resected through a laryngotomy
• Place endoscope through the nares to illuminate the persistent membrane
• Laser dissection = unrewarding w profuse hemorrhage associated with recumbency and general anesthesia  rapid obscure of endoscopic view
• Membrane is incised best w ligasure
• A nasotracheal tube is placed through the surgically created fenestration and sutured to the false nostrils
• Stents are removed 14 days postoperatively

Question 13

nasopharyngeal disfunction is observed in foals of what age? what are the clinical signs?

Answer 13

• Foals <1m old
• Endoscopic examination  severe nasopharyngeal edema, laryngeal edema, milk pooling in the nasopharynx & persistent DDSP
• Nasopharyngeal dysfunction = resp distress, stridor, dysphagia

Question 14

What are the treatment options for nasopharyngeal dysfunction?

Answer 14

• If persistent DDSP  laryngotomy and tracheostomy tube +/- staphylectomy
• Sx NOT necessary in many foals - support medically for 1m, see if problem resolves
• White muscle disease should be identified & treated
• If dysphagic  enteral feeding w nasogastric feeding tube, or parenteral feeding
• Most recover 10-30 days
• Long-term survival = unknown

Question 15

what should you check ina foal with nasal pharyngeal disfunction?

Answer 15

• CE + endoscopic examination + XR of thorax and pharynx + blood work (IgG) and an arterial blood gas analysis

Question 16

at what percentage you should not repair the cleft palate?

Answer 16

if >20% missing DO NOT REPAIR

Question 17

what are the symptoms of cleft palate? dx?

Answer 17

milk from nostrils coughing aspiration pneumonia
oral exam and palpation along with endoscopic exam

Question 18

What are the surgical approaches to cleft palate?

Answer 18

1) transoral approach
2) laryngotomy
3) pharyngotomy
4) mandibular symhysiotomy
5) pharyngotomy with splitting of the basihyoid bone (reair of caudal third of soft palate)

Question 19

Should you wait before going to surgery for cleft palate?

Answer 19

YEs, check Ig and give AB and plasma and check for pneumonia to treat first

Question 20

what is the prefered surgical approach to celft palate?

Answer 20

mandibular symhysiotomy

Question 21

what happens to prognosis if hard palate is involved?

Answer 21

• If hard palate is involved prognosis drops significantly

Question 22

what is the prognosis if midline with minimal tissue missing?

Answer 22

• Cleft palate = midline with minimal tissue missing = 50% prognosis

Question 23

If it is a small defect (1/3 plate) and tracheal aspiration is minimal what is the approach?

Answer 23

• 1/3 soft palate and tracheal aspiration is minimal  delay surgery (monitoring for aspiration pneumonia)
• Weaning early decreases tracheal aspiration
• Advantage of delaying = larger oropharynx facilitates Sx

Question 24

In case of large defaut or significant aspiration pneumonia what should you do?

Answer 24

• LARGE or aspiration is significant
• Sx or euthanasia (poor quality of life and morbidity from chronic aspiration pneumonia)
• Sx = salvage procedure, and it is fraught with complications
• Sutured palatoplasty usually  some failure (with complete or partial dehiscence)
• Reoperation is frequently needed
• Pneumonia = serious, life-ending, complication

Question 25

describe the surgical approach of mandibular symphysiotomy

Answer 25

• GA dorsal recumbency- tracheotomy
• Incise from hyoid  lower lip
• Skin and gingiva over mandibular symphysis completely incised
• Before splitting the symphysis, a hole is prepared to facilitate realignment of the bones during closure.
• Mandibular symphysis severed using a scalpel blade (neonate), or osteotome/oscillating bone saw
• Avoid incising the lip to minimize postoperative dehiscence and discomfort
• Transverse incision at the base of the lip and lip moved caudad  access to symphysis
• After splitting symphysis, lip is moved orally
• Surgical dissection along the right ramus of the mandible, and the attachments of the mylohyoid, geniohyoid, and genioglossus muscles are transected, exposing the buccal mucosa.
• Buccal mucosa is sharply incised
• Rami of the mandibles retracted
• Malleable retractor may be inserted through the laryngotomy over the base of the tongue to push the tongue out of the surgical field
• Moist towels should be used to retract the mandibles
• Cleft repaired
• Mandibles are apposed and stabilized with a Steinmann pin & hemicerclage wire + central incisors are wired together
• Buccal mucosa - closed, and geniohyoid and mylohyoid muscle layers - apposed
• lip is replaced
• Laryngotomy is left open
• Skin closed w interrupted sutures (2 cm gaps up to laryngotomy)  drainage

Question 26

describe soft palate repair in soft palate

Answer 26

• Sx light directed into incision
• Pharyngotomy approach- videoendoscope placed orally
• Mandibular symphysiotomy approach- endoscope placed through laryngotomy
• Stay sutures are passed through SP at the caudal extent of the cleft, and are secured at the laryngotomy site
• Thin strip of mucosa is excised from each edge of the cleft, and a narrow incision is extended into the palate using a No. 12 hooked blade
• Nasal mucosa is closed first, beginning at the caudal free margin of SP (picture shows opposite direction), using 2-0 absorbable suture in a simple-continuous pattern * Oral mucosa and muscular layers are closed together using absorbable sutures in a horizontal mattress pattern (see Figure 45-31, H)
• Silk has excellent handling characteristics and good knot security
• Oral mucosa is closed with absorbable material in a simple-continuous pattern
• Tension  dehiscence
• Tension-relieving incisions are made parallel to the closure plane in the lateral mucosa axial to the molar teeth
• OR - interrupted vertical mattress sutures placed in palate to relieve the tension
• Tensor veli palatini muscle can be transected bilaterally or osteotomy of the hamulus of the pterygoid can be performed to decrease tension
• (may  PI)
• Difficult to repair the caudal end of SP
• Combined transoral and laryngotomy can be an alternative to mandible symphisiotomy
• To gain better access to the caudal aspect of SP, the thyroid cartilage may be split sagittal
• Sutured with three single interrupted sutures of No. 2 monofilament nylon
• The incision of cricothyroid membrane is closed in a simple-continuous pattern with 2-0 polyglactin 910
• SQ and skin are left to heal by second intention

Question 27

describe hard palate repair in cleft palate

Answer 27

• Performed mucoperiosteal flaps
• Mucoperiosteal incision is made parallel to the maxilla from the junction of the HP and SP
• Mucoperiosteum is elevated to the edge of the defect using a periosteal elevator
• Care = palatine artery = emerges from palatine foramina at the caudolateral aspect of the hard palate at the level of the 2nd molar tooth
• Flap is elevated and moved axially
• Sutured together with horizontal mattress sutures
• The defects along the lateral aspect of each mucoperiosteal flap heal by second intention

Question 28

what is the posoperative care of the foal following cleft palate repair?

Answer 28

• If only SP repaired – foal can nurse
• If SP defect was extensive or hard palate was repaired,  nasogastric feeding tube or parenteral feeding for 7 to 10 days
• AB min 5 days
• Oral exam (by looking in the mouth, not by digital palpation), but NOT endoscopic examination during the early postop period

Question 29

What are the common complications of soft palate?

Answer 29

• Dehiscence = most likely and severe complication
• Apparent within 7-14d
• Nasal reflux and coughing
• Other complications include pneumonia, osteomyelitis of the mandible, salivary fistulas, and incisional infections

Question 30

Answer 30