Table e-1 and e-references for: Neurogenic dysphagia: a systematic review and proposal of a classification system

Objective: Introduction of a phenotypic classification of dysphagia with differential diagnostic implications and its validation in different disease groups using videos of flexible endoscopic evaluation of swallowing (FEES).

Methods: A systematic literature review was performed to summarize disease-typical FEES-findings. In an interdisciplinary team, a FEES-based classification of neurogenic dysphagia was developed which distinguishes different dysphagia phenotypes. The classification was validated using 1012 randomly selected FEES videos of patients with various neurological disorders. Chi-square tests were applied to investigate the relationship between the disease groups and each dysphagia phenotype.

Results: Seven dysphagia phenotypes were defined and all phenotypes were significantly  associated with specific neurological disease groups: (1) "Premature bolus spillage" and (2) "delayed swallowing reflex" occurred mainly in stroke patients, (3) "predominance of residue in the valleculae" was most common in Parkinson's disease, (4) "predominance of residue in the piriform sinus" occurred only in myositis, motoneuron disease and brainstem stroke patients, (5) "pharyngolaryngeal movement disorder" was found in atypical Parkinsonian syndromes and stroke patients, (6) "fatigable swallowing weakness" was common in patients with myasthenia gravis, and (7) "complex disorder" with a heterogeneous dysphagia pattern was the leading mechanism in amyotrophic later sclerosis. The interrater reliability showed a strong agreement (kappa = 0.84).

Conclusion: Neurogenic dysphagia is not a mere symptom, but a multi-etiological syndrome with different phenotypic patterns depending on the underlying disease. Dysphagia phenotypes can facilitate differential diagnosis in patients with dysphagia of unclear etiology.