Altered Pharyngeal Muscles in Parkinson Disease

Abstract

Dysphagia (impaired swallowing) is common in Parkinson disease (PD) patients and is related to aspiration pneumonia, the primary cause of death in PD. Therapies that ameliorate the limb motor symptoms of PD are ineffective for dysphagia. This suggests that the pathophysiology of PD dysphagia may differ from that affecting limb muscles but little is known about potential neuromuscular abnormalities in the swallowing muscles in PD. This study examined the fiber histochemistry of pharyngeal constrictor (PC) and cricopharyngeal (CP) sphincter muscles in postmortem specimens from 8 PD and 4 age-matched control patients. Pharyngeal muscles in PD patients exhibited many atrophic fibers, fiber type grouping, and fast-to-slow myosin heavy chain transformation. These alterations indicate that the pharyngeal muscles experienced neural degeneration and regeneration over the course of PD. Notably, the PD patients with dysphagia had a higher percentage of atrophic myofibers vs. with those without dysphagia and controls. The fast-to-slow fiber type transition is consistent with abnormalities in swallowing, slow movement of food and increased tone in the CP sphincter in PD patients. The alterations in the pharyngeal muscles may play a pathogenic role in the development of dysphagia in PD patients.

Effects of Age on Esophageal Motility: Use of High-resolution Esophageal Impedance Manometry

“…Several studies showed that the function of UES could be related to air swallowing, belching, vomiting, and aspiration pneumonia in aged people. [37][38][39] Some controversy has existed concerning the effect of age on LES function. In addition, differences in research topics might exist between the East and the West in the field of neurogastroenterology and motility.…”

Alterations in oropharyngeal sensory evoked potentials (PSEP) with Parkinson’s disease

“…In persons with Parkinson’s disease (PD), dysphagia can result from motor or sensory abnormalities (Born et al, 1996; El Sharkawi et al, 2002; Hunter et al, 1997; Miller et al, 2006; Mu et al, 2012; Pitts et al, 2009; Pitts et al, 2008; Pitts et al, 2010; Potulska et al, 2003; Robbins et al, 1986; Troche et al, 2010; Troche et al, 2008). Throughout the progression of PD, up to 100% of individuals experience some form of dysphagia and aspiration pneumonia is a leading cause of death in these patients (Akbar et al, 2015; Martinez-Ramirez et al, 2015; Pennington et al, 2010).…”

Characterization of Corticobulbar Pharyngeal Neurophysiology in Dysphagic Patients With Parkinson's Disease

“…were reported to be dysphagic before death. 9,10 In particular, there are pathologic signs of synucleinopathy (Lewy bodies) in the dorsal motor nucleus of the vagus nerve 25 (which innervates the smooth muscle of the esophagus) and surrounding areas. Therefore, it is possible that pathology outside the basal ganglia contributes to dysphagia.…”

“…8 Equally, histologic and histochemical studies showed the presence of denervated and atrophied pharyngeal fibers in tissue preparations of previously dysphagic deceased PD patients 9 and a higher density of a-synuclein lesions in pharyngeal motor branches compared with nondysphagic PD patients. 10 However, some physiological studies have shown that dopaminergic medication (L-3,4-dihydroxyphenylalanine [levodopa]), prescribed to enhance synaptic dopamine transmission, does not benefit swallowing.…”