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Case report

A 64-year-old man was admitted with complaints of severe dysphagia for 3 months. Seven years before the admission, the patient had had cervical fractures at C5-6-7 after blunt trauma by a heavy metal wire. At that time, cervical and neck computed tomography (CT) scans showed fractures of the right transverse processes and bodies of C5-7 and of the thyroid cartilage. Also, fractured small bony fragments were scattered anteriorly ( Fig. 1 ). The patient was treated conservatively with a neck collar. Three months after the trauma, the patient sought evaluation at our outpatient clinic with complaints of hoarseness and a scratchy sensation in the throat. A laryngoscopy showed no abnormalities, but an esophagography showed a smooth filling defect in the lateral portion of the right oropharynx. A neck CT scan demonstrated a bony fusion between the fractured transverse processes and small bony fragments and the marginal heterotopic ossification of the thyroid cartilage ( Fig. 2 ). However, the patient did not return to the clinic for follow-up. Seven years after the trauma, the patient returned to our clinic with severe dysphagia for 3 months. A physical examination showed atrophy of the right anterior neck muscles and cutaneous thinning, with prominence of the external carotid artery and vein. A cervical CT scan demonstrated heterotopic bony bridging between the thyroid cartilage and the right transverse processes and bodies of C5-6-7 ( Fig. 3 ). A barium swallow study revealed no laryngeal elevation and aspiration to solids and liquids. Based on the collective findings, we recommended a surgical release of the bony fusion between the cervical spine and the thyroid cartilage.

Cervical CT at the time of the initial cervical trauma demonstrates fractures of the transverse processes and thyroid cartilage and small bony fragments scattered anteriorly.

Cervical CT 3 months after trauma demonstrates heterotopic ossification of the thyroid cartilage and fusion between the transverse processes and bony fragments.

Cervical CT 7 years after trauma. The axial image (A) and 3-dimensional reconstruction image (B) demonstrate an unusual synostosis between the cervical transverse processes and the thyroid cartilage at C5-7.

A standard Smith-Robinson approach was performed, and a longitudinal incision was made anterior to the external carotid artery. We carefully dissected between the carotid artery and the bony bridge. The common carotid artery was pulled laterally, and the bony mass bridging the thyroid cartilage and transverse processes from C5 to C7 was identified. The thyroid cartilage was immobile because of bony arrest. The prevertebral space above and below the bony mass was exposed. Protecting the pharynx and esophagus, the bony mass was removed by a high drill and Kerrison punch, and the surrounding fibrous tissues were resected. Finally, the thyroid cartilage was released from the cervical spine, with restoration of mobility. We drilled out the remnant osteophytes of the cervical spine and put bone wax on both bony surfaces to prevent recurrence. Postoperatively, the patient was able to swallow solid foods and liquids, with immediate improvement in dysphagia. At follow-up, barium swallow study showed restoration of laryngeal elevation and pharyngeal peristalsis. A postoperative CT scan showed the bony bridging with sufficient gaps between the thyroid cartilage and the cervical spine ( Fig. 4 ). To prevent recurrent fusion and adhesions, we advised the patient to repetitively move the thyroid cartilage using swallowing exercise.

Postoperative 3-dimensional CT scan shows the bony bridging between the thyroid cartilage and the transverse processes with sufficient space.

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Discussion

Cervical osteophytes are common degenerative changes in the cervical spine. Occasionally, osteophytes cause compression of the pharynx or esophagus, resulting in dysphagia . However, surgical intervention is not necessary in patients with dysphagia due to osteophytes, except in rare cases of diffuse idiopathic skeletal hyperostosis (DISH) . Osteophytes alone rarely cause dynamic impairment of swallowing . Cervical osteophytes are a cause of dysphagia and have been reported to account for 4.4% of all cases . Large anterior cervical osteophytes causing dysphagia are associated with DISH, senile degenerative spondylosis, and posttraumatic osteophytogenesis . Dysphagia associated with DISH has been frequently reported in the literature . However, posttraumatic osteophytes causing dysphagia have rarely been reported .

The main mechanism leading to dysphagia secondary to cervical osteophytes is a direct mechanical obstruction of the pharynx or esophagus. However, osteophytes causing dynamic impairment of the pharyngeal phase during swallowing are extremely rare . Crowther and Ardrah first reported a case of osteophytes preventing retroversion of the epiglottis, resulting in dysphagia. In our case, posttraumatic bony fusion between the thyroid cartilage and the cervical spine caused severe dysphagia by an arrest of laryngeal elevation during the pharyngeal phase of swallowing. The current case is the first report of posttraumatic synostosis between the cervical spine and the thyroid cartilage causing dysphagia, which was improved by surgical treatment. In 1997, Moses et al first reported a similar case in which posttraumatic synostosis occurred between the transverse process of C3 and the greater thyroid cornu, with decreased laryngeal elevation. However, in the current report, longer fusion occurred between the transverse processes of C5-7 and the thyroid cartilage (from the greater to lesser cornua). Therefore, there was no laryngeal elevation during swallowing, and dysphagia was more severe. In addition, in the previous report, surgical treatment was not performed, and the patient was treated by speech therapy alone, with modest improvement. In the current case, the authors surgically removed the bony bridging between the thyroid cartilage and the cervical spine and were able to achieve complete improvement of dysphagia.

In addition, Moses et al did not include the initial radiologic findings of cervical fracture and the thyroid cartilage at the time of the trauma. Therefore, they suggested the fracture of asymptomatic cervical osteophytes, which had existed before trauma, causing heterotopic bony bridging as a possible mechanism. In our case, serial radiologic studies were obtained since the trauma. The authors speculated the mechanism of an unusual delayed synostosis between the thyroid cartilage and the cervical spine on the basis of serial radiologic studies. First, the cervical transverse processes should be fractured because the thyroid cartilage is closest to the cervical transverse processes. Only vertebral body fractures may not induce bony fusion due to the distance to the thyroid cartilage. Second, small bone fragments of fractured transverse processes, which can be bridges, should be scattered within the prevertebral space, as in the current case. Third, the concurrent injury of the thyroid cartilage should induce heterotopic ossification and its remodeling. Fourth, injury of the surrounding soft tissues may cause local adhesion of the esophagus or pharynx with the cervical spine, thus decreasing local mobility and accelerating delayed bony fusion. In the current case, esophagography 3 months after trauma showed a smooth filling defect at the lateral portion of the right oropharynx indicating posttraumatic adhesions. Nevertheless, our speculation may not completely explain the mechanism of delayed bony fusion 7 years after trauma.

The recurrence of bony fusion between the thyroid cartilage and the cervical spine may be possible. Therefore, we tried to drill bony bridges out as much as possible, creating enough space between the 2 structures, and applied massive bone wax on both surfaces of the resection margin. In addition, we instructed the patient to habitually move the thyroid cartilage to prevent recurrent fusion using swallowing exercise. Nevertheless, serial follow-up CT scans may be needed for early detection of a possible recurrence. In summary, we have presented an extremely rare case of posttraumatic synostosis between the thyroid cartilage and the cervical spine causing severe dysphagia. We suggest surgical resection of heterotopic bony bridging for immediate improvement of dysphagia. The mechanism is not clear, but concurrent fracture of the thyroid cartilage and cervical transverse process with anterior fragmental scattering was a factor causing dysphagia, and a decrease in local motility by posttraumatic adhesions may accelerate the unusual delayed synostosis between the 2 structures.