Preliminary Evaluation of the Pathomechanisms of Dysphagia After Occipitospinal Fusion: Kinematic Analysis by Videofluoroscopic Swallowing Study.

Kinematic analysis of swallowing function using videofluoroscopic swallowing study (VFSS).The aims of this study were to analyze swallowing process in the patients who underwent occipitospinal fusion (OSF) and elucidate the pathomechanism of dysphagia after OSF.Although several hypotheses about the pathomechanisms of dysphagia after OSF were suggested, there has been little tangible evidence to support these hypotheses since these hypotheses were based on the analysis of static radiogram or CT. Considering that swallowing is a compositive motion of oropharyngeal structures, the etiology of postoperative dysphagia should be investigated through kinematic approaches.Each four patients with or without postoperative dysphagia (group D and N, respectively) participated in this study. For VFSS, all patients were monitored to swallow 5-mL diluted barium solution by fluoroscopy, and then dynamic passing pattern of the barium solution was analyzed. Additionally, O-C2 angle (O-C2A) was measured for the assessment of craniocervical alignment.O-C2A in group D was -7.5 degrees, which was relatively smaller than 10.3 degrees in group N (P = 0.07). In group D, all cases presented smooth medium passing without any obstruction at the upper cervical level regardless of O-C2A, whereas the obstruction to the passage of medium was detected at the apex of mid-lower cervical ocurvature, where the anterior protrusion of mid-lower cervical spine compressed directly the pharyngeal space. In group N, all cases showed smooth passing of medium through the whole process of swallowing.This study presented that postoperative dysphagia did not occur at the upper cervical level even though there was smaller angle of O-C2A and demonstrated the narrowing of the oropharyngeal space towing to direct compression by the anterior protrusion of mid-lower cervical spine was the etiology of dysphagia after OSF. Therefore, surgeon should pay attention to the alignment of mid-cervical spine as well as craniocervical junction during OSF.4.