Ch 100 Palate Flashcards
Palate
- palate separates the nasal passages, choanae, and nasopharynx from the oral cavity and oropharynx
How may pairs of pharyngeal arches are there in the embryo?
What arches form the mandibular and maxillary prominences?
6 pharyngeal arches
The first arch forms the mandibular and maxillary prominences
Embryology
- secondary palate is formed from bilateral palatal shelves that grow out from the maxillary processes.
- These palatal shelves then elevate rapidly above the tongue and join with each other and the developing nasal septum
What form of epithelium forms in the nasal cavity and the oral cavity?
Nasal - pseudostratified ciliated columnar
Oral - stratified squamous
What bones form the hard palate?
Palatine
Maxillary
Incisive bones
Name the following bones
blood supply
- major palatine artery exits through the major palatine foramen
- major palatine branch of the maxillary division of the trigeminal nerve
- Blood to the soft palate is principally supplied by the minor palatine arteries (which branch off of the maxillary arteries
What is the normal level of extension of the soft palate?
Extends just caudal to last maxillary molar teeth in normal dogs
List the muscles of the soft palate and their function
- Palatinus - shortens the palate rostrocaudally
- Tensor veli palatini - Stretched the soft palate between the pterygoid bones
- Levator veli palatini - Elevates the caudal soft palate
What are the 2 functions of the soft palate during swallowing?
- Stimulation of sensory nerves in the palate are part of the mechanism that triggers swallowing
- Closure of intrapharyngeal opening suring swallowing and vomiting to prevent food entering the nasopharynx and subsequently being aspirated
Palate defects
- Congenital lip and palate defects in cats and dogs can be inherited or are a sequela of intrauterine trauma or stress
- Causes of palate defects acquired after birth include: infections, trauma, neoplasms, and surgical and radiation therapy.
congenital hypoplasia of the soft palate,
- restoration of a palatopharyngeal sphincteric ring and normal swallowing function may not be achieved because of the lack of functional soft palate musculature
What side do unilateral cleft lips most commony form?
left
At what time in foetal development does an insult need to occur to result in a palatal defect?
between day 25-28 in dogs
trauma; stress; corticosteroids, nutritional, hormonal, viral, or toxic
timing of surgery
- Most performed between 3 and 4 months of age.
- Surgery before 2 months of age is challenging
- Postponing surgery until after 5 months of age may result in a wider cleft as the animal grows and compounded management problems, which are not desirable
- prognosis without surgical repair for large defects reported to be guarded because of the risk of aspiration
trauma
- may take several days before the extent of local injury is clearly defined.
List some basic principles of surgical correction of palate defects
- Teeth at the surgical site or those which could damage the repair are removed 6-8 weeks prior to definitive repair
- Laser, electrosurgical and radiosurgical devices not used for haemostasis
- Flap should be at least 1.5x as wide as the defect they are going to cover
- 2-layer closure
- Suture lines preferable not overlying a void
- Injured tissue left to fully declare itself prior to repair
anaesthesia
- Regional analgesia (maxillary, infraorbital, and major palatine nerve blocks)
Repair of Rostral Defects
- congenital defects of the primary palate, attempts to close the lip and most rostral hard palate defects by simple sliding procedures are rarely successful
- Repair is achieved with advancement, rotation, transposition (from labial and buccal mucosa), or overlapping flaps, followed by reconstructive cutaneous surgery to provide symmetry
What is the standard closure technique for a:
- Congenital hard palate defect
- Traumatic hard palate “split” as with highrise syndrome
- Soft palate midline cleft
Congenital hard palate - Overlapping flap
Traumatic highrise syndrome - Medially positioned flap
Soft palate - medially positioned flap
name this flap
Overlapping flap
- There is less tension on the suture line,
- the suture line is not located directly over the defect,
- area of opposing connective tissues is larger, which results in a stronger scar.
- It provides more reliable results
- the major palatine artery must not be transected during flap
- major palatine foramen at the palatine shelf of the maxilla approximately 0.5 to 1.0 cm medial to the maxillary fourth premolar
- Granulation and epithelialization of exposed bone generally are completed in 3 to 4 weeks
name this flap
medially positioned flap
- making relieving incisions approximately 1 to 2 mm away from the maxillary cheek teeth on one or both sides is often necessary unilaterally or bilaterally so that the flaps can be moved medially
- trauma > proper occlusion can be accomplished by approximating displaced bony structures with digital pressure and placing a twisted orthopedic wire between the two maxillary canines and covering it with a self-curing composite resin.
- if the relieving incisions are long and gape, a lateral oronasal defect may result
List options for surgical correction of congenital hypoplasia of the soft palate
- Bilateral tonsillectomy and extension
- Bilateral buccal mucosal flaps (one rotated, one rotated and overlapped)
- Bilateral pharyngeal advancement flaps and one overlapping hard palate flap
How do you repair an oronasal fistula?
Labial-based mucoperiosteal flap
How can you close a large caudal hard palate defect?
split palatal U-flap
List options for large palatal defects
- Removal of teeth 6-8 weeks prior
- Local axial pattern flaps (based on major palatine and infraorbital arteries)
- Distant axial pattern flaps (angularis oris, caudal auricular, superifical temporal etc)
- Tongue flap
- Grafting of auricular cartilage
- Corticocancellous tibial bone
- Myoperitoneal microvascular flaps
- Prostheses (obturator) > Fabrication and placement of a palatal obturator usually requires two anesthetic episodes (metal alloy, nonaqueous elastomeric impression material, or synthetic resin.)
Halitosis is a common complication with palatal obturators. Dogs and cats with palatal obturators should be reexamined under general anesthesia every 6 to 12 months to remove the obturator, flush the nose, clean the edges of the palatal defect, and scale and polish the obturator before it is placed back into position.
complications
wound dehiscence
- result of tension on suture lines because of insufficient flap mobilization before closure
- compromised blood supply of flaps as a result of severe trauma or multiple previous surgeries
- follow-up surgeries should not be attempted before healing of all tissues involved
What % or airway resistance is due to the nose in normal dogs?
80%
BOAS
- primary components: stenotic nares, hypoplastic trachea, redundant pharyngeal tissue and aberrant conchae
- eversion of the mucosa of the lateral ventricles occurs secondary to chronic subatmospheric pressure in the airway that is generated to overcome resistance to airflow.
- The turbulent airflow over the mucosa causes edema and swelling.
- Over time, the laryngeal cartilage frame can weaken and the larynx can progressively collapse
What is Poiseuille’s law?
Q = π(pressure difference)(r^4)/8nl
Q - rate of flow
r - radius
n - viscosity of the gas
l - length of airway
Flow is proportional to radius to the fourth power
Pathophysiology
- Stenotic nares and abnormal intranasal turbinate > stertorous breathing due to increased resistance to nasal airflow.
- overlong soft palate projects into the larynx and causes stridor
- causes a fixed-type upper airway obstruction in the majority of brachycephalic dog studies
- increased resistance to airflow is caused largely by a decrease in airway radius as illustrated by Poiseuille’s law
- inspiratory muscles contract for a longer time during each breath cycle in response to increasing upper airway resistance, thus prolonging inspiration
- decreases (PaO2) and increases (PaCO2), stimulates increased respiratory effort when compensation by other mechanisms is inadequate
- Inspiratory and expiratory muscle work generates substantial heat. The work of breathing, combined with hot weather and exercise, often precipitates decompensation in brachycephalic dogs
- funtional dz may contribute > Fibrosis of pharyngeal dilator muscles or Pharyngeal collapse
- are at risk of developing noncardiogenic pulmonary edema
- Presumably, subatmospheric intrapleural pressure required to overcome chronic partial upper airway obstruction in affected dogs predisposed them to hiatal hernia, gastroesophageal reflux, and subsequent esophagitis.
What is the Hering-Breuer reflex?
A stretch reflex mediated by vagal fibres that control the rate and depth of respiration.
Causes a longer contraction of the inspiratory muscles during each breath cycle in response to increased upper airway resistance
What functional disorders may also contribute to BOAS?
Fibrosis of the pharyngeal dilator muscles
Pharyngeal collapse
What % of dogs with BOAS have moderate to severe GI signs?
10-74%
What is the normal tracheal diameter?
20% of thoracic inlet
What should be given before or at induction for upper airway exam?
Anticholinergic to minimise risk of severe bradycardia from vagal discharge during pharyngoscopy
- glycopyrrolate over atropine when needed.
Monitor airway function closely, as thickened secretions and tachycardia can worsen respiratory issues.
Clinical Signs and Diagnosis
- Animals in severe respiratory distress need to be evaluated quickly and intubated if respiratory arrest is imminent
- cold intravenous fluids, sedation with acetylpromazine (0.01 mg/kg IV), oxygen supplementation, and dexamethasone (0.05 to 0.1 mg/kg IV)
- Concurrent cardiac disease has been reported in dogs with overlong soft palates,28 and Bulldogs are particularly prone to congenital pulmonic stenosis.
- radiographs of the neck and thorax to evaluate possible concurrent cardiac disease, aspiration pneumonia, pulmonary edema, and tracheal diameter.
staphalectomy
- proposed level of palate resection, the caudal border of the palatine tonsils
- excessive rostral retraction of the soft palate can make judging the appropriate level of palate resection difficult.
- Clinical experience is therefore often used to determine the appropriate palate length.
- resection is performed with scissors,a carbon dioxide laser, or bipolar sealing device
- caudal pharynx and area surrounding the endotracheal tube must be covered by saline-soaked gauze sponges for protection form laser
folded flap palatoplasty
- by reducing the soft palate’s length and thickness
- removed together with underlying connective tissue and parts of the palatinus and levator veli palatini muscles.
- suture knots will be located more rostral and farther from the pharynx
post op
- Corticosteroids (dexamethasone, 0.05 to 0.1 mg/kg IV
- respiratory rate and effort and arterial hemoglobin oxygen saturation are monitored frequently.
- Food and water are withheld for 12
- postoperative GI signs are aggressively treated with a proton pump inhibitor (omeprazole [0.7 mg/kg PO q24h]), or metoclopramide constant rate infusion [1 to 2 mg/kg/d IV])
dupre and finji
What setting should be used for CO2 laser staphylectomy?
5-6W
Continuous mode
What is the prognosis following soft palate resection?
Good to excellent in 90%
Persistent or recurrent signs should prompt a skull CT and retroflexed nasopharyngeal endoscopy to assess for nasopharyngeal turbinates or progression of laryngeal collapse
