An update on Laryngeal Paralysis
AN UPDATE ON LARYNGEAL PARALYSIS
Ameet Singh DVM, DVSc, DACVS-SA
University of Guelph
Idiopathic laryngeal paralysis has recently been renamed to Geriatric Onset Laryngeal Paralysis Polyneuropathy (GOLPP). This is based on the findings that over 2/3rds of dogs have esophageal dysfunction and ~1/3 of dogs have signs of neurological weakness at time of presentation. A thorough physical, neurological and orthopedic examination is recommended in all suspect GOLPP patients. The most common breed affected is the Labrador Retriever, however, other breeds such as the Brittany Spaniel, Golder Retriever and Australian Shepherd can be affected.
Clinical signs as a result of the inability of the cricoarytenoideus dorsalis (CAD) muscle to abduct the arytenoid cartilage include inspiratory stridor, dyspnea, exercise intolerance and even collapse. Historical signs may include a change in bark. The diagnosis of GOLPP is not solely based on upper airway exam findings. The author strongly believes that the diagnosis should be made in the exam room while listening to the dog and matching with suspicious signlament and history. The upper airway exam prior to surgery is used as a confirmatory test and also to rule-out mass lesions.
Prior to surgery all GOLPP dogs should have three-view thoracic radiographs as a general health screening to rule out neoplasia but also as a baseline evaluation of the pulmonary parenchyma for evidence of aspiration pneumonia. Abdominal ultrasonography should be performed ideally in stable dogs to rule out evidence of any sinister disease. Complete bloodwork should be completed prior to anesthesia for surgery.
Laryngoscopic examination should be performed under a light plane of anesthesia. An assistant should be available to call out the phase of respiration. This is a critical step so as not to confuse paradoxical movement of the arytenoids with normal movement. During inspiration the arytenoids should abduct whereas with paradoxical movement, they adduct and then abduct during expiration due to the flaccid nature of the arytenoids. This author routinely used doxopram (1 mg/kg) which stimulates the respiratory centre and results in improved ventilatory efforts so that a more accurate evaluation of arytenoid function can be performed.
Surgical intervention is required for cases with bilateral laryngeal paralysis. This consists of unilateral crico-arytenoid ("tie-back") which increases the diameter of the airway (rima glottidis). The patient is placed in right lateral recumbency as it is easier for the right handed surgeon to operate on the left side of the larynx. The initial approach is made ventral to the jugular vein, just caudal to the bifurcation through the skin, subcutaneous tissues and platysma/cutaneous trunci muscles. Digital palpation reveals the wing of the thyroid cartilage and the thyropharyngeus muscle that overlies this cartilage is sharply incised in a cranial to caudal manner along the ridge of the thyroid cartilage. A stay suture is placed in the wing of the thyroid cartilage and lateral traction is gently applied. Careful blunt dissection is made through to expose the muscular process of the arytenoid cartilage where the CAD muscle attaches. The muscle is atrophied in many GOLPP cases. This muscle is incised at its attachment on the muscular process of the arytenoid and the incised edge is used as a handle to provide lateral traction. This movement allows for careful dissection and exposure of the cricoarytenoid joint. This can be carefully penetrated with mosquito forceps. Once the circular joint surface on the arytenoid has been visualized, two sutures are passed from caudal to cranial from the cricoid cartilage through the muscular process of the arytenoid, mimicking the direction/angulation of the CAD muscle.
Author TIP: Over-tightening of the suture can result of increased risk of aspiration pneumonia post-operatively. The author recommends firm tightening of the suture. A large bore endotracheal tube is recommended and the arytenoid simply needs to be maintained to the opening created by placement of the endotracheal tube.
Author TIP: The author recommends intra-operative visualization of the laryngoplasty whichrequires extubation and then re-intubation following confirmation of appropriate lateralization.
The second suture is tied to approximately the same tightness as the first suture and a splash block with local analgesia. The thyropharyngeus muscle is closed in a simple continuous pattern. The remainder of the soft tissues are closed routinely.
Post-operatively, opioid analgesia is minimized to reduce the risk of nausea and/or aspiration pneumonia by maintaining airway control. The author feeds these dogs balls of soft food for the first several days postoperatively and continues anti-emetic therapy. Discharge from hospital is performed within 24 hours post-operatively to minimize excitement and the potential for suture breaking and/or aspiration pneumonia.
Summarily, postoperative outcomes are positive with surgical treatment of GOLPP and dogs can enjoy a good quality of life. Aspiration pneumonia is the biggest risk of surgery perioperatively and for life and owners of GOLPP dogs should be made aware of this prior to surgery.