Dysphagia after Occipitothoracic Fusion is Caused by Direct Compression of Oropharyngeal Space Due to Anterior Protrusion of Mid-cervical Spine.

Study design: This was a retrospective study. Objective: To investigate the relationship among the craniocervical alignment, the oropharyngeal space, and the incidence of dysphagia after occipitothoracic fusion (OTF). Summary of Background Data: Craniocervical malalignment after OTF is one of a trigger of dysphagia. However, there has been no logical explanation for the etiology yet. Methods: A total of 32 patients who underwent OTF (5 male, 27 female) were reviewed. Following 4 parameters on the lateral cervical radiogram, pharyngeal tilt angle (PTA); the angle between the McGregor’s line and the line that links the center of C2 pedicle and the center of vertebral body at the apex of cervical sagittal curvature, diameter of oropharyngeal airway space (dPS), O–C2 angle, and C2–C7 angle were measured at follow-up and then the relationship of these parameters and their influence to the incidence of dysphagia were analyzed. Results: Six of 32 cases (18.8%) exhibited postoperative dysphagia. ROC curves showed that PTA and dPS had moderate accuracy for the predictor of the dysphagia after OTF with the area under the curve (AUC) of 0.76 and 0.86 respectively, whereas O–C2 angle had low accuracy with AUC of 0.69 and C2–C7 angle was almost useless for prediction of postoperative dysphagia with AUC of 0.51. A multiple linear regression analysis showed that only PTA was significantly correlated with dPS (β=0.822, P=0.014), whereas the O–C2 angle (β=0.101, P=0.779) and C2–C7 angle (β=0.352, P=0.157) had negligibly small influence on dPS. Conclusions: Our results demonstrated strong relationships between PTA and the value of dPS, and the incidence of dysphagia. As PTA reflects anterior protrusion of mid-cervical spine, these results indicated that dysphagia after OTF is caused by narrowing of oropharyngeal space due to direct compression from anteirorly protruded mid-cervical spine.