Speech-swallow dissociation in velopharyngeal closure for differentiating amyotrophic lateral sclerosis and myasthenia gravis.

OBJECTIVE: Speech-swallow dissociation (SSD) in velopharyngeal closure on laryngoscopy is a sign of pseudobulbar palsy. We hypothesized that this finding could differentiate amyotrophic lateral sclerosis (ALS) from myasthenia gravis (MG). This study aimed to identify laryngoscopic findings useful in differentiating these two diseases. METHODS: ALS and MG patients with bulbar symptoms who underwent fiberoptic laryngoscopy in our hospital were retrospectively examined. The following laryngoscopic items were evaluated: velopharyngeal incompetence (VPI) in phonation and swallowing, pharyngeal constriction, vocal cord movement, and salivary status. RESULTS: One hundred seven patients (70 with ALS and 37 with MG) were included for analysis. The prevalence of VPI in phonation was significantly higher in the ALS group (40 % vs. 19 %; P = 0.027). The prevalence of SSD in velopharyngeal closure was also significantly higher in the ALS group (33 % vs. 3 %; P < 0.001). The other laryngoscopic findings did not differ between the groups. Multivariate logistic regression showed that SSD in velopharyngeal closure was independently associated with ALS (odds ratio, 26.64; 95 % confidence interval, 2.24-317.58; P = 0.009). CONCLUSION: SSD in velopharyngeal closure is useful for differentiating ALS from MG.