+ General Considerations
- Mean age 11.3 years, with 90% cats > 8 years
- Malignant tumors are more common
- LSA is most common although ADC and SCC also reported
- LSA may present as a diffuse thickening of laryngeal mucosa or localized mass
+ Clinical Features
- Clinical Signs: voice change, respiratory noise or distress with obstruction, exercise intolerance, dysphagia, and pain with inflammation and ulceration
- Diagnosis: ultrasound, survey radiographs, and biopsy under direct endoscopic visualization
- DDx: inflammatory polyps and laryngeal cysts
TREATMENT
+ General Considerations
- Benign tumors and cysts can be removed while preserving function although more radical procedures required for malignant tumors such as permanent tracheostomy and complete laryngectomy
- Partial or complete laryngectomy is indicated for proliferative (i.e., granulomatous laryngitis) and neoplastic diseases
- Temporary tracheostomy may be required to permit resection
- Other options include radiation therapy and chemotherapy depending on tumor type and extent
+ Total Laryngectomy
- Total laryngectomy is indicated for tumors with bilateral laryngeal involvement
- Ventral midline cervical incision
- Traction sutures are placed around the 4th tracheal ring
- Trachea is transected caudal to the cricoid cartilage
- Sterile endotracheal tube is placed into the distal trachea and used to maintain general anesthesia
- Laryngeal attachments of the thyropharyngeal, cricopharyngeal, sternothyroid, and thyrohyoid muscles are transected
- Sternohyoid muscle is preserved
- Caudal aspect of the larynx is elevated and mobilized free of all attachments
- Sensory and motor nerves to pharyngeal mucosa and muscles and cranial esophagus are preserved to maintain normal swallowing ability
- Mucosa is incised at the rostral edge of the larynx and the entire larynx, including the epiglottis, is removed
- Pharyngeal mucosa is closed with a continuous inverting pattern of 3-0 absorbable suture material
- Transected ends of the thyropharyngeal and cricopharyngeal muscles are sutured together ventral to the pharynx and esophagus
- Proximal segment of the trachea is exteriorized
- Sternohyoid muscle is sutured to the trachea with interrupted sutures to maintain the trachea in a ventral position
- Excess subcutaneous tissue and skin are removed from the stoma site to prevent occlusion of the tracheostomy
- Elliptical skin incision is made 25%-30% larger than the trachea
- Subcutaneous tissue is sutured to the tracheal wall
- Skin is sutured to the tracheal mucosa with 3-0 or 4-0 absorbable suture material in an interrupted pattern
+ Rotatory Door Myocutaneous Flap
- Rotatory door myocutaneous flap was developed to bring vascularized epidermis into the laryngeal defect
- Island flap is based on the sternohyoid muscle with the dermis sutured to the mucosa
- Ventral midline cervical skin incision forms the medial edge of the myocutaneous flap
- Skin is not separated from the sternohyoid muscle and cranial thyroid blood vessels are preserved
- Cutaneous segment of the myocutaneous flap is depilated by shaving the epidermis down to the dermis
- Adequate dermal shaving prevents regrowth of hair and subsequent dermal scarring supports the graft
- Exposed dermal surface is covered by squamous or respiratory epithelium
+ Segmental Hemilaryngectomy
- Indication: small tumors involving the vocal cord and adjacent superficial tissues
- Ventral midline laryngotomy
- Tumor extent and margins are assessed
- Standard vocal cordectomy is performed if the tumor is localized to the vocal cord
- Mucosal incisions are deepened through full-thickness laryngeal cartilage if tumor involvement is more extensive
- Mucosal and cartilage defect is repaired primarily or filled with free tissue implants
- Free tissue implants include costal cartilage, buccal mucosa, and thyroid cartilage
- Free tissue implants are only used when the majority of the thyroid and arytenoid cartilages are resected
- Free tissue implants are sutured to the remaining cartilage with 3-0 or 4-0 monofilament absorbable suture material on a cutting needle
- Strap muscles and subcutaneous tissue are used to support the external aspect of the free tissue implant
Augmented Myomucosal Flap
+ General Considerations
Augmented myomucosal flap was developed to repair laryngotracheal resection in 2 stages
+ Stage 1
- Ventral midline cervical incision
- Free buccal mucosal graft is used to cover the planned defect
- Porous high-density polyethylene (0.85 mm thick, average pore size > 150 μm, and pore volume 50%) is sutured over the free buccal mucosal graft
- Sternohyoid muscle, with preservation of cranial and caudal attachments, is mobilized and sutured over the free buccal mucosal graft and polyethylene
+ Stage 2
- Composite graft is released
- Laryngotracheal resection is performed as planned for tumor excision
- Laryngotracheal defect is repaired with the composite graft
- Polyethylene does not need to be fully covered by mucosa at the time of reconstruction as the polyethylene will be infiltrated by granulation tissue and rapidly epithelialized
- Temporary tracheostomy is performed distal to the resection site and maintained until healing and confirmation of airway patency
+ Prognosis
- Rhabdomyoma: most dogs will live > 1 year and are considered cured
- Malignant laryngeal tumors are rare tumors which are not frequently treated hence data not available