Stylocarotid Artery Syndrome (Eagle Syndrome, Vascular Variant)
- Background:
- Stylocarotid artery syndrome, a vascular variant of Eagle syndrome, is a rare entity that results in compression of the carotid artery by an elongated styloid process and/or calcified stylohyoid ligament.
- The etiology is unknown but is proposed to be due to heterotopic calcification in the setting of chronic renal failure or other causes of abnormal calcium/phosphorus metabolism.
- An elongated styloid process is seen in up to 4% of the population; however, only 4–10% are symptomatic. The clinical signs and symptoms are usually unilateral; however, the elongation of the styloid process is usually bilateral.
- Clinical Presentation:
- Symptoms relate to the mechanical compression of the carotid artery, irritation of the sympathetic plexus adjacent to the carotid artery, or both with some overlapping symptoms. Head and neck movement or rotation can trigger or aggravate symptoms.
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Arterial impingement may result in dizziness, syncope, carotid dissection, transient ischemic attack, aphasia, visual disturbance, and rarely thrombus formation and embolic stroke.
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Sympathetic plexus irritation can cause neck pain, headache, eye pain, tinnitus, or dizziness.
- Key Diagnostic Features:
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On imaging, there is an elongated styloid process measuring greater than 3 cm. The normal length of the styloid process in an adult is approximately 2.5 cm.
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CT angiogram may demonstrate carotid artery dissection or a filling defect consistent with thrombus.
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Acute embolic stroke is demonstrated with restricted diffusion on brain MRI.
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- Differential Diagnoses:
- Carotid dissection would demonstrate a flap or vascular caliber change on angiogram.
- Cardioembolic stroke would demonstrate restricted diffusion on MRI with or without a filling defect at the embolic source.
- Atherosclerotic carotid stenosis would demonstrate narrowing of the carotid artery either from calcified or noncalcified plaque.
- Vasculitis may present on imaging as an ectatic or narrowed vessel or surrounding soft-tissue/inflammatory change.
- Treatment:
- Acute management may include thrombectomy, anticoagulation, or surgical removal of the prominent styloid process.
- Satisfactory long-term management would require surgical resection of the elongated styloid process and/or calcified stylohyoid ligament, either by transoral or lateral neck approach.
