Laryngeal paralysis is a relatively common neurological disease characterized by loss of motor control to the larynx, resulting in dysphagia, voice changes and involuntary aspiration of food and fluids.
Damaged to any of the four nerves innervating the larynx (right and left recurrent laryngeal nerves and superior laryngeal nerves) can result in partial or complete temporary or permanent laryngeal paralysis.
An underlying polyneuropathy complex is thought to be involved in many cases.
Laryngeal paralysis can be congenital or acquired and is common seen in large-breed dogs such as Labrador Retrievers.
Acquired laryngeal paralysis can occur from trauma or surgical injury during thyroidectomy or compression of the recurrent laryngeal nerve by a cranial mediastinal carcinoma or thyroid carcinoma. More commonly, however, laryngeal paralysis is classified as idiopathic in older dogs.
- Trauma to recurrent laryngeal nerve - bite wounds, thyroidectomy
- Idiopathic neuropathy
- Greyhound polyneuropathy
- Brachycephalic breed predisposition
- Primary laryngeal neoplasia
- Tick paralysis - responsive following treatment
- Systemic lupus erythematosus - responsive
- Tetanus - responsive
- Myasthenia gravis
- Idiopathic acute canine polyradiculoneuropathy
- Neuroaxonal dystrophy
- Masticatory muscle myositis
- Pulmonary edema
- Thyroid carcinoma
Affected dogs usually present with varying degrees of phonation change and respiratory distress which may be of acute or slow onset, depending on cause. These symptoms develop as a result of laryngeal collapse and consequent spatial distortion to the larynx, resulting in physiological airway obstruction.
Diagnosis is based on endoscopic evaluation of the larynx, often during general anesthesia. A contrast esophagram with videofluoroscopy may be required to make a definitive diagnosis of decreased esophageal motility. Biopsies of laryngeal tissue usually reveal varying degrees of loss of large-caliber nerve fibers, axonal degeneration and neurogenic atrophy.
With idiopathic laryngeal paralysis, a bilateral ventriculocordectomy can be performed through a ventral median laryngotomy, which is successful in many cases.
Alternative treatment methods include partial arytenoidectomy, vocal fold resection, bilateral arytenoid stenting and transverse cordotomy with cuneiform cartilage amputation. Some dogs may require concurrent soft palate resection because prolonged negative airway pressure can increase soft palate length and thickness.
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