Ossified Stylohyoid chain with Stylohyoid joint

Clinical History

Admitted to emergency with facial trauma for evaluation.

Imaging Findings

The patient was admitted to the emergency room with acute head and facial injuries from a traffic accident. Imaging of the face by CT scan showed the incidental presence of complete ossification of the right stylohyoid chain articulating with the lesser cornu of the hyoid bone. A contralateral elongated styloid process was present. No fractures were identified in relation to these findings. Oblique reformatted images from the coronal facial spiral CT were obtained demonstrating the ossified segment in continuity as shown in figure. The patient was treated for his minor head and facial injuries and discharged for follow up in the outpatient surgery clinic.

Discussion

Multiple anatomical variations are described in relation to the styloid process and the stylohyoid ligament. An elongated styloid process or calcification/ossification of the stylohyoid ligament is most often an incidental finding on plain film radiography or computerized tomographic (CT) scan. Rarely these can be symptomatic due to compression of the neurovascular structures in the upper neck resulting in craniofacial and cervicopharyngeal pain syndromes described as Eagle syndrome, Stylohyoid and Pseudostylohyoid syndromes. This entity can also result in extrinsic compression and impingement over the external or internal carotid arteries. A pseudoarticulation between the ossified stylohoyid chain and the hyoid bone is extremely rare. We report one such case which was incidentally found on CT scan in a male patient with acute trauma. He was asymptomatic for this finding at presentation.
The stylohyoid chain articulating with the hyoid bone is a rare finding with only a few cases reported in the literature. The case shows psuedoarticulation of the ossified segment above the mandibular angle. Simple elongation of the opposite styloid process is also noted. Despite the unilateral complete ossification of the stylohyoid complex and elongation of the contralateral styloid process, our patient had no clinical symptoms related to the abnormality.
The styloid process, stylohyoid ligament and lesser cornu of the hyoid bone form from the stylohyoid chain which develops from the first and second branchial arches and Reichert’s cartilage. The incidence of a stylohyoid chain abnormality is variable ranging from 1.4% to 84% depending on the classification of the anomaly and clinical presentation. However, the average radiographic incidence is about 18.2 % with a reported prevalence of symptomatic cases in 1 %-5 % of patients. It may be unilateral or bilateral with increasing incidence in older age groups. Diffuse idiopathic skeletal hyperostosis(DISH) has been implicated in some cases. This stylohyoid chain aberration most commonly presents as an incidental finding on imaging in the asymptomatic adult. The radiographic mineralization of the styloid process is classified into 3 types. Type I is simple elongation of the styloid process . Type II is ossification of the stylohyoid complex with pseudoarticulation as featured in this case. Type III represents a true segmentation and is rare. Segmentation with true articulation has been reported in cadaveric dissections.
Plain film radiography, orthopantomograms and CT scans have been widely utilized in the evaluation of these patients. The most common presentations in symptomatic patients include craniofacial and pharyngeal pain, odynophagia, dysphagia, dysphonia, pain on extension of the tongue, sensation of hypersalivation, headache, neck pain, glossopharyngeal neuralgia and carotidynia.
The mineralized stylohyoid segment is prone to fractures. Cases have been reported where ossification of the stylohyoid chain followed cervicopharyngeal trauma. The effects of hyperflexion and hyperextension(whiplash) injuries can be exacerbated in the presence of this process. Only severely symptomatic cases not responding to medical management require surgical excision of the mineralized segment. In our case, surgery was not recommended since the patient was completely asymptomatic. A close follow up in such cases for onset of clinical symptoms of nerve or vessel compression is recommended . Early surgical intervention by intraoral or external approach with excision of the ossified segment will result in complete amelioration of pain in symptomatic patients.

Differential Diagnosis List

Final Diagnosis

Ossified stylohyoid chain with stylohyoid joint

URL:	https://www.eurorad.org/case/2348
DOI:	10.1594/EURORAD/CASE.2348
ISSN:	1563-4086