How vets diagnose laryngeal paralysis in dogs using three tests

Abstract

OBJECTIVES: To evaluate laryngeal function using 3 diagnostic techniques: echolaryngography (EL), transnasal laryngoscopy (TNL), and laryngoscopy per os (LPO). STUDY DESIGN: Prospective clinical study. ANIMALS: Dogs with laryngeal paralysis (n=5) and control dogs (n=10); 5 age- and breed-matched dogs and 5 young, breed-matched dogs. METHODS: Laryngeal function was evaluated in conscious dogs using EL. All examinations were recorded and evaluated by separate, blinded observers upon completion of the study. The methods were compared with a standard evaluation incorporating all clinical knowledge of the case (STD) using sensitivity, specificity, positive, and negative predictive values. RESULTS: Three dogs with bilateral laryngeal paralysis requiring surgery were diagnosed as unilaterally affected or normal on EL. Three dogs had paradoxic motion on TNL and LPO, 2 of those were considered normal on EL, and 1 had no motion on EL. Paralysis was diagnosed in 1 age-matched and 3 young control dogs on EL. LPO and TNL falsely diagnosed lack of arytenoid movement in 2 age-matched controls and 1 young control. Two age-matched and 1 young control dog were misdiagnosed as paralyzed with TNL and LPO. DISCUSSION: Direct observation of the larynx allowed better evaluation of laryngeal function compared with EL. TNL did not require induction of anesthesia, but did not improve the ability to assess laryngeal function compared with LPO. CONCLUSIONS: EL was not as effective as direct observation of the larynx. TNL did not improve the evaluation of laryngeal function compared with LPO. CLINICAL RELEVANCE: We use LPO combined with knowledge of the clinical history and physical examination to diagnose laryngeal paralysis in preference to EL and TNL.