Proceedings of a Workshop on - The Havemeyer Foundation

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Havemeyer Foundation Monograph Series No. 11 REFERENCES Bathe, A.P. (1993) Left laryngeal hemiplegia in the horse: A survey <strong>of</strong> diagnostic criteria and management practices employed by 20 veterinary surgeons in Europe. Equine vet. Educ. 5, 84-85. Bayly, W.M., Grant, B.D., and Modransky, P.D. (1984) Arterial blood gas tensions during exercise in a horse with laryngeal hemiplegia, before and after corrective surgery. Res. vet. Sci. 36, 256-258. Brown, J.A., Derksen, F.J., Hartman, W.M., Robinson, N.E., and Stick, J.A. (2003) Ventriculo-cordectomy reduces respiratory noise in horses with laryngeal hemiplegia. Equine vet. J. 35, (6) 570-574. Cadoit, P.J. (1893) Roaring in Horses: Its Pathology and Treatment. Translated by T.J.W. Dollar, Swan Sommnenschein & Co. London. pp 15-78. Dixon, P.M., McGorum, B.C., Railton, D.I., Tremaine, W.H., Dacre, K. and McCann J. (2003a) Long-term survey <strong>of</strong> laryngoplasty and ventriculo-cordectomy in an older, mixed-breed population <strong>of</strong> 200 horses. Part 2: Owners’ assessment <strong>of</strong> the value <strong>of</strong> surgery. Equine. vet. J. 35, 397-401. Dixon, P.M., McGorum, B.C., Railton, D.I., Tremaine, W.H., Dacre, K. and McCann J. (2003b) Long-term survey <strong>of</strong> laryngoplasty and ventriculo-cordectomy in an older, mixed-breed population <strong>of</strong> 200 horses. Part 1: Maintainence <strong>of</strong> surgical arytenoids abduction and complication <strong>of</strong> surgery. Equine. vet. J. 35, 389-396. Ducharme, N.G. and Hackett, R.P. (1991) The value <strong>of</strong> surgical treatment <strong>of</strong> laryngeal hemiplegia in horses. Comp. cont. Educ. pract. Vet. 13, 472-475. Ducharme, N.G. and Hackett, R.P. (1995) Surgical alternatives in the treatment <strong>of</strong> laryngeal hemiplegia in horses. <strong>Proceedings</strong> <strong>of</strong> Geneva Congress <strong>of</strong> Equine Medicine and Surgery. Swiss Vet. 11-5, pp 59-61. Duncan, I.D., Amundson, J., Cuddon, P.A., Sufit, R., Jackson, K.F. and Lindsay, W.A. (1991) Preferential denervation <strong>of</strong> the adductor muscles <strong>of</strong> the equine larynx 1: muscle pathology. Equine vet. J. 23, 94-98. Hammer, E.J, Tulleners, E.P., Parente, E.J. and Martin, B.B. (1998) Videoendoscopic assessment <strong>of</strong> dynamic laryngeal function during exercise in horses with grade-3 left laryngeal hemiparesis at rest: 26 cases (1992-1995). J. Am. vet. med. Ass. 212, 399-403. Hawkins, J.F., Tulleners, E.P., Ross, M.W., Evans, L.H., and Raker, C.W. (1997) Laryngoplasty with or without ventriculectomy for treatment <strong>of</strong> left laryngeal hemiplegia in 230 racehorses. Vet. Surg. 26, 484-491. Kidd, J.A. and Slone, D.E. (2002) Treatment <strong>of</strong> laryngeal hemiplegia in horses by prosthetic laryngoplasty, ventriculectomy and vocal cordectomy. Vet. Rec. 150, 481-484. Marks, D., Mackay-Smith, M.P., Cushing, L.S., and Leslie, J.A. (1970) Observations on laryngeal hemiplegia in the horse and treatment by abductor muscle prosthesis. Equine vet. J. 2, 159-166. Nemeth, F. (1987) Techniques and results <strong>of</strong> the surgical treatment <strong>of</strong> roaring in 398 horses, using a modified Mackay-Smith method. Pferdeheilkunde 3, 27-31. Parente, E.J. (2004) Improvements in laryngoplasty. Havemeyer Foundation Monograph Series No 11, Eds: P. Dixon, E. Robinson and J.F.Wade, R&W Publications (Newmarket) Ltd, pp 66-67. Speirs, V.G., Bourke, J.M., and Anderson, G.A. (1983) Assessment <strong>of</strong> the efficiency <strong>of</strong> an abductor muscle prosthesis for the treatment <strong>of</strong> laryngeal hemiplegia in horses. Aust. vet. J. 60, 294-299. Strand, E., Martin, S.G., Haynes, P.F., McLure, J.R. and Vice, J.D. (2000) Career racing performance in Thoroughbreds treated with prosthetic laryngoplasty for laryngeal neuropathy: 52 cases. (1981-1989). J. Am. vet. med. Ass. 217, 1689-1696. Tetens, J., Derksen, F.J., Stick, J.A., Lloyd, J.W. and Robinson, N.E. (1996) Efficacy <strong>of</strong> prosthetic laryngoplasty with and without bilateral ventriculocordectomy as treatments for laryngeal hemiplegia in horses. Am. J. vet. Res. 57, 1668-1673. Weishaupt, M.A., Vogt, R., Fürst, A. and Auer, J.A. (2003) Spirometric and endoscopic assessment <strong>of</strong> surgical treatment in horses with laryngeal hemiplegia. Equine Recurrent Laryngeal Neuropathy. Havemeyer Foundation Monograph Series No 11, Eds: P. Dixon, E. Robinson and J.F.Wade, R&W Publications (Newmarket) Ltd, pp 81-82. 65
Equine Recurrent Laryngeal Neuropathy IMPROVEMENTS IN LARYNGOPLASTY E. J. Parente University <strong>of</strong> Pennsylvania, New Bolton Centre, 382 West Street Road, Kennet Square, PA 19348, USA Despite recognition <strong>of</strong> laryngeal hemiplegia for over 100 years and development <strong>of</strong> the laryngoplasty procedure over 30 years ago, there have been no major changes to treatment <strong>of</strong> laryngeal hemiplegia since its description by Marks et al. (1970). There is still reluctance by trainers to have the procedure performed as it does not return the horse to ‘normal’, and has potential complications. Furthermore, failure to maintain abduction <strong>of</strong> the arytenoid, both short-term and long-term, is a documented problem. This has led to interest in modifications <strong>of</strong> the standard laryngoplasty and alternative procedures. Unfortunately, alternative procedures such as reinnervation have had limited success and require a longer return to return to training. A minor but significant improvement in laryngoplasty is removal <strong>of</strong> the vocal cord. While early research did not detect a significant improvement in airway mechanics with a ventriculectomy, most surgeons now believe that removal <strong>of</strong> the vocal cord is beneficial based on both clinical and experimental evidence. Treadmill endoscopy clearly demonstrates the deviation <strong>of</strong> the vocal cord during inspiration if it is not removed as an adjunctive procedure with laryngoplasty. While the sacculectomy may not truly stabilise the cord, there is some question whether a sacculectomy is beneficial by creating fibrous support for the abducted arytenoid. The majority <strong>of</strong> efforts to improve laryngoplasty deal with maintenance <strong>of</strong> arytenoid abduction and thus suture retention (Dixon et al. 2003). Causes <strong>of</strong> failure are thought to be associated with suture pull out, assumed through the muscular process based on experimental models (Dean et al. 2001). Yet, more <strong>of</strong>ten it appears to be ‘loosening’ in clinical cases that results in decreased abduction. One technique developed to minimise loosening was concurrent recurrent laryngeal neurectomy while performing laryngoplasty for horses with remaining laryngeal motion (Davenport et al. 2001). The hypothesis was that cycling from remaining muscular pull resulted in suture loosening. Performing the neurectomy was ineffective in improving the prognosis relative to standard laryngoplasty. Other methods to maintain arytenoid abduction include techniques to place sutures and different suture materials. Mechanical testing <strong>of</strong> in vitro models has been promising but these methods do not yet have long-term clinical followup and may present greater difficulty in placement in vivo than present standard procedures. We have pursued 2 other methods. We now <strong>of</strong>ten approach the muscular process from behind the cricopharyngeus muscle. This can be performed with appropriate positioning <strong>of</strong> the horse under general anaesthesia. Dissection is performed easily just above a branch <strong>of</strong> the cranial thyroid vein and just caudal to the cricopharyngeus muscle through dense fascia to access the muscular process <strong>of</strong> the arytenoid. This approach should minimise any slack <strong>of</strong> the suture material by fascial interference and prevent crossing <strong>of</strong> suture that could occur when passing multiple strands under the cricopharyngeus muscle belly. An approach to improve stability <strong>of</strong> the larynx with laryngoplasty has also been developed by creating an arthrosis <strong>of</strong> the cricoarytenoid (CA) joint. The hypotheses for the experimental model were: 1) that surgical destruction <strong>of</strong> the CA joint could be performed using a motorised burr via a routine laryngoplasty surgical approach; 2) that surgical destruction <strong>of</strong> the CA joint with a motorised burr in conjunction with laryngoplasty would result in joint fusion and improved stability 66
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