Proceedings of a Workshop on - The Havemeyer Foundation

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Havemeyer Foundation Monograph Series No. 11 MANAGEMENT OF CANINE LARYNGEAL PARALYSIS J. G. Lane Department <strong>of</strong> Clinical Veterinary Science, University <strong>of</strong> Bristol, Langford House, Langford, Bristol, BS40 5DU, UK In the horse recurrent laryngeal neuropathy has been recognised as a clinical disorder for centuries, but in the dog laryngeal paralysis was first documented only 30 years ago (O’Brien et al. 1973). It is likely that the condition is not new but newly recognised and in former times it may have been confused with cardio-pulmonary failure or non-responsive idiopathic millophylline deficiency (Table 1). The major differences between the canine and equine presentations <strong>of</strong> the neurogenic failure <strong>of</strong> the intrinsic laryngeal musculature are that in dogs the disease is typically bilateral by the time that clinical signs appear, and older animals are likely to be involved. A congenital and inherited version <strong>of</strong> the disorder is recognised in the Bouvier de Flandres (van Haagen 1978) and the husky (Hendricks and O’Brien 1985), but the majority <strong>of</strong> canine patients are over 10 years <strong>of</strong> age at presentation. Two thirds <strong>of</strong> afflicted dogs are male or neutered male and those weighing 25–35 kg are most susceptible. The best recognised predisposed breeds include the Labrador retriever, Afghan hound, Irish setter, and English and German pointers (Lane 1986; see Table 2). Giant breeds are rarely involved probably because <strong>of</strong> their limited longevity. TABLE 1: Major presenting signs reported by owners <strong>of</strong> 750 dogs with acquired laryngeal paralysis presented at UBVS Stridor 656 Gagging/retching cough 434 Changed bark 327 Reduced exercise tolerance 317 The presenting signs for canine laryngeal paralysis (Table 1) include stridorous breathing even at rest, reduced exercise tolerance, a moist retching cough and loss <strong>of</strong> bark. Owner expectations <strong>of</strong> older dogs <strong>of</strong>ten lead to delayed presentation. Ventriculo-cordectomy has never been proposed as a means to manage canine laryngeal paralysis (Table 3) but initially a radical partial laryngectomy was used (O’Brien et al. 1973). This comprised the excision <strong>of</strong> the true and false vocal folds as well as the ventral projections <strong>of</strong> the arytenoid cartilages. An unacceptable complication rate was achieved (Ross et al. 1991). Laryngoplasty (‘tie-back’) surgery represents one <strong>of</strong> the few instances where an equine technique has been transferred to canine surgery. The technique first proposed a lateralisation <strong>of</strong> the disarticulated arytenoid on each side <strong>of</strong> the larynx to the wing <strong>of</strong> the thyroid cartilage using a ventral approach (Harvey and van Haagen 1975). The technique most widely used today comprises a combined prosthetic abductor implantation with a lateralising suture on the left side <strong>of</strong> the larynx only (Lane 1982; LaHue 1989). The left lateral approach is similar to that used in the horse but the small muscular process <strong>of</strong> the dog is insufficiently robust to hold fixation sutures. Thus, the arytenoid is disarticulated to access the thicker body <strong>of</strong> the cartilage. Although the canine version <strong>of</strong> the disease is invariably bilateral a unilateral solution is sufficient for the demands <strong>of</strong> the sedentary life <strong>of</strong> an elderly dog. Only working dogs such as Huntaways are subjected routinely to bilateral surgery (Burbidge et al. 1993). The results <strong>of</strong> ‘tie-back’ surgery in dogs are excellent in experienced hands and the incidence <strong>of</strong> complication is much lower than for the equivalent procedure in horses (White 1989). 83
Equine Recurrent Laryngeal Neuropathy TABLE 2: Breed prevalence in 750 dogs with acquired laryngeal paralysis presented at UBVS Breed UBVS Cases UK control population (Thrusfield, 1989) No % % Labrador* 307 40.9 10.7 Afghan hound* 84 11.2 NR < 3 Irish setter* 61 8.1 NR < 3 Golden retriever* 43 5.7 3.8 English springer spaniel 20 2.7 2.9 Border collie 16 2.1 4.5 Flat coat retriever 14 1.9 NR < 3 English setter 13 1.7 NR < 3 Standard poodle 13 1.7 NR < 3 St Bernard 10 1.3 NR < 3 Finnish spitz 10 1.3 NR < 3 Rhodesian ridgeback 9 1.2 NR < 3 Weimaraner 7 0.9 NR < 3 Airedale 6 0.8 NR < 3 English cocker spaniel ‡ 6 0.8 4.3 Greyhound 6 0.8 NR < 3 Other + crosses 125 - - German SD ‡ 0 - 8.4 Yorkshire terrier ‡ 0 - 6.0 Jack Russell terrier ‡ 0 - 5.2 West Highland terrier ‡ 0 - 3.9 * Significantly over-presented breeds ‡ Significantly under-presented breed NR Insufficient numbers recorded but less than 3 percent TABLE 3: The development <strong>of</strong> surgical treatments for acquired laryngeal paralysis <strong>of</strong> dogs Date Technique Authors 1973 Partial laryngectomy O'Brien et al. 1975 Unilateral arytenoid lateralisation by ventral Harvey and Venker-van approach, using routine tracheotomy intubation Haagen 1982 Unilateral arytenoid lateralisation by lateral Lane approach without routine tracheotomy intubation 1982 Bilateral arytenoid lateralisation by ventral Rosen and Greenwood approach 1983 Castellated laryng<strong>of</strong>issure and vocal fold Gourley et al. resection 1986 Modified castellated laryng<strong>of</strong>issure with Smith et al. arytenoid lateralisation 1986 Abductor prosthesis Lane (also cited by LaHue 1989) 1986 Composite laryngoplasty combining unilateral Lane abductor prosthesis with lateralisation 1993 Bilateral arytenoid lateralisation using Burbidge et al. bilateral lateral approaches 84
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