Abnormal swallowing–breathing coordination is an electrokinesiographic feature of dysphagia in multiple system atrophy: a comparative study with Parkinson’s disease

Multiple system atrophy (MSA) is a progressive neurodegenerative disorder characterized by autonomic failure and motor impairment, with dysphagia emerging early and representing a key feature for differential diagnosis from Parkinson’s disease (PD). Safe and efficient swallowing relies on precise coordination between oropharyngeal events and breathing, yet this interaction has not been systematically investigated in MSA. To quantify the temporal relationships between oropharyngeal phases and breathing during water and jelly swallows, we retrospectively analyzed the electrokinesiographic study of swallowing (EKSS) from 38 patients with the parkinsonian variant of MSA (MSA-P), 16 patients with the cerebellar variant of MSA (MSA-C), 21 patients with PD, and 15 healthy controls. MSA patients exhibited widespread oropharyngeal dysfunction across both bolus consistencies, with MSA-C showing the most severe abnormalities. Both MSA phenotypes indeed displayed multiple EKSS alterations consistent with disrupted swallowing–breathing coordination, including paradoxical sequencing and prolonged inter-events intervals. The MSA-C group showed additional impairment in the control of the upper esophageal sphincter. In contrast, PD patients had milder EKSS abnormalities, predominantly involving oral phase parameters. The post-swallowing inspiration index reliably discriminated MSA from PD across all bolus types, being significantly higher in MSA patients and indicating more pronounced swallowing–breathing desynchronization. These findings provide a detailed neurophysiological characterization of oropharyngeal swallowing in MSA and PD, highlighting disease- and phenotype-specific patterns: predominant impairment of the pharyngeal phase and its coordination with breathing in MSA, particularly in MSA-C, and mainly oral phase involvement in PD.