Canine laryngeal paralysis, Part 2: Surgical treatment, aftercare, prognosis and complications - DVM
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Canine laryngeal paralysis, Part 2: Surgical treatment, aftercare, prognosis and complications
The tie back remains the most common surgical method for correction


DVM360 MAGAZINE



Figure 1A: The preoperative appearance of the larynx during inspiration of a dog with bilateral laryngeal paralysis. Note the airway obstruction produced by the paradoxical adduction of the arytenoids and vocal folds. (Photo courtesy of Dr. Brendan McKiernan.)
A newer concept in laryngoplasty is the use of nickel-titanium alloy (Nitinol—NDC) stents. The goal is to provide sufficient reduction in open-epiglottis airway resistance (to alleviate signs of obstruction) while increasing the closed-epiglottis airway resistance with a potential decrease in the risk for aspiration pneumonia. Some preliminary research with stents has been published, but results of clinical trials have not yet been reported.


Figure 1B: A laryngoscopic view after unilateral (left) arytenoid lateralization laryngoplasty, or tie back. Note the permanently abducted left arytenoid cartilage (to the viewer's right) as well as the absence of any blood or swelling associated with the procedure. Also note that the inability of this arytenoid to adduct during deglutition renders the airway at some increased risk for aspiration. Unilateral procedures are chosen (even though affected dogs have bilateral paralysis) precisely for this reason. Further enlargement of the rima glottidis offers minimal advantage in reducing airway resistance, but would greatly increase the risk for aspiration due to the inability to adduct during swallowing. (Photo courtesy of Dr. Brendan McKiernan.)







Because normal function is not restored, the downside of widening the glottis is increasing the risk for aspiration of food or liquid into the trachea or beyond, with resultant increased coughing, gagging, choking or, in the worst instances, signs of aspiration pneumonia. So it is a balancing act between adequate increased glottal widening and overcorrection that places the patient at increased risk for aspiration. A recall of fluid dynamics reminds us that resistance to flow in a tube is inversely proportional to the radius of that tube raised to the fourth power. Thus, small changes in diameter can result in huge differences in resistance. As surgeons, this means that only modest lateralization should dramatically reduce airway resistance. Hence, arytenoid lateralization is usually only done unilaterally, even though affected dogs are paralyzed bilaterally, and the degree of abduction need not be maximal to achieve clinically beneficial effects (Figures 1A and 1B).

Arytenoid lateralization surgery is most commonly performed on the left side because most surgeons are right-handed, so the left side is generally easier to operate on. If surgery fails (e.g., suture breakage, cartilage tearing), it provides the contralateral side as a spare. There has been some investigation into selectively choosing the side to operate based on the location of the esophageal ostium relative to the glottis, with the thinking that selection of the side farthest away from this opening might reduce the risk for aspiration. This concept has not yet been validated as being clinically significant.


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Source: DVM360 MAGAZINE,
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