33rd Annual Scientific Meeting proceedings

Laryngeal diseases associated with brachycephalic obstructive airway syndrome (BOAS) are thought to be mainly secondary to the turbulent airflow and chronic high negative pressures in the pharynx.¹ In addition, granuloma development can occur as a result of reflux laryngitis or as a complication of laryngeal surgery such as excision of everted laryngeal saccules. They include:

• Mucosal oedema
• Everted laryngeal saccules (ELS)
• Laryngeal collapse
• Granuloma

Laryngeal collapse is a form of upper-airway obstruction caused by loss of cartilage rigidity that allows medial deviation of the rostral laryngeal cartilages.^2-4 The condition represents an advanced, secondary stage in the progression of BOAS.⁵ Its development is related to the increased airway resistance, increased negative intra-glottic luminal pressure, and increased air velocity associated with the BOAS.^2,3 These forces displace the rostral laryngeal structures medially with permanent cartilage deformation.⁶ The net result is the gradual collapse of the rostral laryngeal opening. Classically, three stages of laryngeal collapse are recognised in the dog: in stage I laryngeal collapse there is eversion of the laryngeal saccules, in stage II there is loss of rigidity and medial displacement of the cuneiform processes of the arytenoid cartilage, and in stage III there is collapse of the corniculate processes of the arytenoid cartilages with loss of the dorsal arch of the rima glottidis.⁷

The reported prognosis for dogs suffering from laryngeal collapse appears to be variable. Many individuals with stage I collapse show a marked improvement following multimodal surgical intervention: saccule resection, partial staphylectomy and nasal alaplasty surgery.^2,3,8-10 Resection of the saccules was for many years considered the standard treatment for clinically significant stage I laryngeal collapse. However, recently, the role of sacculectomy has been questioned.^9,11,12 The use of sacculectomy surgery remains controversial, with some authorities suggesting that such surgery might increase significantly the morbidity following BOAS surgery.¹³

Dogs suffering from stage II or III laryngeal collapse have been considered to carry a very guarded prognosis with, historically, aryepiglottic fold resection, permanent tracheostomy or euthanasia cited as the only options for management.^14-17 More recently, two novel surgical options have been proposed and evidenced for the management of stage II and III collapse; these are arytenoid laryngoplasty and cuneiformectomy.^18,19

Arytenoid laryngoplasty
In a retrospective study of a consecutive series of 12 dogs suffering from life-threatening stage II or III laryngeal collapse associated with BOAS combined cricoarytenoid and thyroarytenoid caudo-lateralisation (arytenoid laryngoplasty) was used to enlarge the rima glottidis leading to an associated long-term improvement
in respiratory function in the remaining 10/12 dogs suffering from stage II and stage III laryngeal collapse.¹⁸ The procedure of arytenoid lateralisation has also been used to successfully manage non-brachycephalic dogs suffering from combined laryngeal paralysis and laryngeal collapse.¹⁹ Personal observations of the technique of combined cricoarytenoid and thyroarytenoid caudo-lateralisation (arytenoid laryngoplasty) for the management of stage II or III laryngeal collapse would suggest that it is most effective in the management of cases suffering from stage II rather than stage III collapse.

Cuneiformectomy
Partial cuneiformectomy has been described as part of the modified multilevel surgery for management of BOAS.²⁰ The procedure reduces dynamic obstruction and widens the rima glottidis. Healing occurs by granulation and epithelialisation and has been reported to be complete by 14 days postoperatively.³ Recently, retrospective study of 182 dogs with BOAS undergoing modified multilevel airway surgery (95 control dogs; 87 additionally undergoing cuneiformectomy) has been described.²¹ Cuneiformectomy was performed if clinically indicated where grade II or III laryngeal collapse was present. Dogs were assessed for preoperative stridor and laryngeal collapse, respiratory functional grading (RFG) and whole body barometric plethysmography (WBBP) index scores, hospitalisation duration and complication rates. Cuneiformectomy was not associated with a higher overall complication rate than conventional multilevel surgery and was considered an effective treatment for laryngeal collapse in dogs with BOAS.²¹ One practical advantage of performing cuneiformectomy rather than arytenoid laryngoplasty for the management of grade II or III laryngeal collapse is that it can be performed at the same time as other intra-oral components of BOAS multilevel  surgery, such as palatoplasty or tonsillectomy, negating the requirement for intra-operative repositioning.²¹

A further recent study has described performing a subtotal epiglottectomy and ablation of unilateral arytenoid cartilage as a surgical treatment for grade III laryngeal collapse in dogs.²² One-year postoperative findings of this study were encouraging (owners of 12/16 patients rated their dogs as follows: excellent in five cases, good in five cases, and fair in two cases).

Granulomas
Vocal fold granulomas are recognised in brachycephalic dogs and are considered to be associated with chronic inspiratory efforts, air turbulence, regurgitation and laryngeal aspiration of acidic gastro-oesophageal reflux.^23,24 In the dog, the lesions appear to be most commonly unilateral affecting the vocal cords.^23,24 The lesions are often ulcerated and their gross appearance can be mistaken for malignant disease. Their presence might cause a change in bark, or, as they grow, their size will obstruct the laryngeal lumen causing respiratory obstructive signs and stridor. Current therapy for laryngeal granulomas consists of surgical excision (sharp excision or laser ablation) combined with multilevel BOAS surgery and medical management of gastro-oesophageal reflux disease. Although only a small number of managed cases have been reported, the prognosis following multilevel intervention is currently considered favourable.^23,24 Recurrence is a possibility and this might relate to incomplete excision and/or failure to manage the underlying cause for the development of the condition.

References
Available on request.