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Emergence Of Deglutology: A Transdisciplinary Field.
Published 2014 · Medicine
Oropharyngeal dysphagia is a well-known manifestation of a large number of acute and chronic neurologic disorders including Parkinson's disease (PD), and is associated with pulmonary complications as a leading cause of mortality in these patients 1. Symptoms of dysphagia in PD patients poorly correlate with objective video fluoroscopic findings 2; in addition, age, severity and duration of the disease are not reliable predictors of dysphagia 3. Deglutitive dysfunction in PD does not improve with levodopa therapy 4-6, and may occasionally deteriorate with dopamine precursor therapy 2. The exact underlying neurogenic mechanisms of swallowing dysfunction in PD are not well established and involvement of non-dopaminergic mechanisms has been suggested 6. Recent comprehensive postmortem neuropathologic studies of PD patients have indicated that brain pathology (Lewy neurites and Lewy bodies) in PD originates in the olfactory bulb and visceromotor projections of dorsal nucleus of the glossopharyngeal and vagal nerves in medulla oblongata years prior to involvement of nigrostriatal pathway and onset of somatomotor dysfunction 7. Furthermore, these histopathologic observations have shown atrophic and denervated pharyngeal constrictors and cricopharyngeus myofibers 8; axonal degenerative changes in vagal and sympathetic motoneurons innervating pharyngeal constrictors and cricopharyngeus 9, along with degenerative changes of predominantly sensory internal superior laryngeal branch of the vagus nerve 10. Collectively these central and peripheral autonomic sensorimotor impairments in dysphagic PD patients may explain compromised cough reflex 11, delayed swallow reflex 3, 12, pharyngeal peristaltic incoordination 3, 13 and incomplete UES relaxation 3, 14. Together these mechanistic abnormalities contribute to self-reported dysphagia (28-41%) 15, objective videofluoroscopic metrics of dysphagia (77-87%) 15 and ultimately aspiration pneumonia (11-45%) in PD patients 16, 17. Current dysphagia management in PD patients is unsatisfactory. A number of approaches including dietary modification and swallowing maneuvers 16, dopaminergic and anticholinergic pharmacotherapy 18, expiratory muscle strengthening 19, video based biofeedback therapy 20, cricopharyngeal myotomy 21 and cricopharyngeus Botolinum toxin injection 22 have all been utilized with variable outcomes, necessitating further research to devise pathophysiology based therapeutic modalities 23.