Page 12 - Functional impairment and cues for rehabilitation of head and neck cancer patients -

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Chapter 1
issues such as lymphedema, sticky saliva and xerostomia, and altered taste and sensibility in the treated areas. As imaginable, these negative side effects may cause serious deterioration of the quality of life of HNC survivors.
Although tumor- and treatment-related functional limitations are most likely to occur in advanced stage (III and IV) HNC, knowledge on functional limitations in early stage (I and II) is also needed to inform (shared) treatment decisions. For early-stage oropharyngeal cancer, for example, surgery as well as radiotherapy are equivalent concerning oncological outcomes, but different with respect to severity and timing of short- and long-term morbidity (18-24). To our knowledge, only one study has assessed differences in self-reported functional outcomes using a randomized comparison between these treatment modalities. This study showed no clinically meaningful difference in the swallowing-related quality of life, one year after treatment (25). In the near future, currently ongoing (randomized) comparative studies, such as the EORTC-1420- HNCG-ROG trial (NCT02984410) and the ORATOR trial (NCT03210103), comparing surgery and RT, will increase the body of evidence and hopefully provide more definitive conclusions on the optimal patient selection for surgery or radiotherapy (26, 27). In the meantime, further observational analyses comparing self-reported swallowing and other functional outcomes would be informative.
Muscles involved in eating and drinking
Treatment in the head and neck area is prone to causing functional limitations because this area has a high density of vital functions, which are regulated by complex mechanisms. Swallowing, for instance, is enabled by subsequent activation of over thirty different muscles, with the need for close coordination to ensure a safe swallow (28, 29). The first of the four phases of swallowing, the oral preparatory phase includes chewing and preparing the food bolus for transportation to the oropharynx. This transportation by the tongue occurs during the subsequent oral phase. These first two phases are facilitated by facial, masticatory, and tongue muscles innervated by the facial, trigeminal, and hypoglossal nerve. Afterwards, during the pharyngeal phase, velopharyngeal closure occurs, and the bolus is transported down to the upper esophageal sphincter by reflexive contractions of the pharyngeal muscles. Also, the airway is protected by forward elevation and closure of the larynx. Muscles involved include the pharyngeal, laryngeal, palatal and supra- and infrahyoid muscles, innervated by the glossopharyngeal, accessory and vagal nerve, respectively. During the last phase, the esophageal phase, the bolus is transported to the stomach by peristaltic contractions of the esophageal muscles. This complex mechanism of swallowing may be interrupted on multiple levels, with dysphagia as a result, which may lead to aspiration and pneumonia.
Assessment of swallowing function
To identify and assess the extent of functional limitations, and swallowing in particular, currently, numerous objective (e.g., videofluoroscopy and functional oral intake scale) and subjective (e.g., Swallowing Quality of Life Questionnaire (SWAL-QOL) and MD Anderson Dysphagia Inventory (MDADI), evaluation methods are available (39). However, there is a