Comparison of Deep Cervical Flexor Muscle Strength and Endurance in Patients With and Without Neurogenic Dysphagia

Cervical posture is vital for normal swallowing function. Changes in cervical posture during swallowing alter the bolus flow and swallowing kinematics through changes in gravity and oropharyngeal space. The hyoid bone does not articulate with any bone, so it requires adequate tension of the hyolaryngeal complex and proper cervical postural alignment to maintain its stabilization and position. Changes in cervical posture and stabilization can cause changes in hyoid bone position and kinematics through muscles and ligaments which may lead to decrease in hyoid elevation, loss of optimal strength of the suprahyoid and infrahyoid muscles due to disrupted length-tension relationship, and an increased risk of aspiration due to insufficient laryngeal elevation. Further, deterioration in cervical posture and decreased stabilization resulting from cervical muscle weakness or/both endurance could affect the control and strength of masticatory muscles, tongue muscles and suprahyoid - infrahyoid muscles, which are involved in swallowing function. Whereby DCF weakness gives rise to inadequate cervical stabilization, change in hyoid bone stabilization, alterations in suprahyoid and infrahyoid muscle function, and decreased laryngeal elevation may adversely affect the normal function of the swallowing related muscles. Thus, decreased cervical stabilization, which is often seen in neurological diseases, may be related to neurogenic dysphagia. Given the known changes in cervical stabilization as a consequence of neurologic injury, the additional impact on swallowing or a potentially already neurologically-disordered swallow is considered. Thus, loss of cervical stabilization may be one of the factors affecting dysphagia in patients with neurological diseases providing more information on all potential factors contributing to swallow impairment, potentially leading to more targeted and effective swallowing interventions. However, there is no study investigating the role of the DCF muscles in dysphagia. Therefore, the aim of the present study was to comparison of deep cervical flexor muscle strength and endurance in patients with and without neurogenic dysphagia.