Eagle's syndrome with stylohyoid chain pseudoarthrosis and thyrohyoid ligament ossification: A case report and literature review.

RATIONALE: Eagle's syndrome is caused by anatomical variations or ossification of the stylohyoid chain (SHC) and presents with complex, nonspecific symptoms, often leading to delayed diagnosis. Complete ossification of the SHC is exceptionally rare, and reporting such cases may enhance clinical awareness and improve diagnostic accuracy.

PATIENT CONCERNS: A 57-year-old man presented with persistent right mandibular pain lasting over 4 months. The pain intensified with mouth opening, swallowing, or head tilting, and radiated beneath the right earlobe. Conservative treatments including anti-inflammatory medication, nerve block therapy, and acupuncture were ineffective.

DIAGNOSES: Physical examination revealed tenderness and swelling under the right earlobe, pain in the right floor of the mouth, and moderate limitation of mouth opening. Multilayer spiral CT with 3-dimensional reconstruction demonstrated complete ossification and thickening of the right SHC, elongation of the left styloid process, and ossification of the left lateral thyrohyoid ligament, confirming Eagle's syndrome.

INTERVENTIONS: Extraoral surgical resection was performed, including excision of the ossified stylohyoid ligament, the entire styloid process, and partial hyoid bone resection.

OUTCOMES: The patient achieved complete pain relief postoperatively. During a long-term follow-up of nearly 5 years, no recurrence was observed.

LESSONS: This case illustrates an uncommon presentation of Eagle's syndrome with complete SHC ossification and thyrohyoid ligament involvement. Multilayer spiral CT with 3-dimensional reconstruction provides critical diagnostic and surgical planning value. Surgical resection remains the most effective treatment and should be individualized according to the patient's anatomical features and symptoms.