What is Eagle syndrome and how does it occur?

What is Eagle Syndrome and How Does It Occur

Eagle syndrome is a rare condition caused by an elongated styloid process (typically >30 mm) or calcification of the stylohyoid ligament, resulting in compression of adjacent nerves and arteries that produces characteristic orofacial and neck pain. 1, 2

Anatomical Basis and Pathophysiology

The styloid process is a slender bony projection that normally measures approximately 2.5 cm (15.2-47 mm) in adults, with its tip positioned between the external and internal carotid arteries, just lateral to the tonsillar fossa. 2, 3

When the styloid process elongates beyond 30 mm or when the stylohyoid ligament calcifies, it can mechanically impinge on surrounding neurovascular structures, leading to the symptom complex known as Eagle syndrome. 1, 3

The pathophysiology involves:

• Direct mechanical compression of adjacent sensory nerve endings (particularly cranial nerves V, VII, IX, and X) 2
• Vascular compression of the internal and external carotid arteries 2
• Inflammatory changes developing in the surrounding tissues due to chronic irritation 2

Epidemiology and Clinical Significance

The prevalence of anatomic elongation of the styloid process in the adult population is estimated at 4%, but only approximately 0.16% of these individuals become symptomatic. 1 This means that while the anatomical abnormality is relatively common, the actual syndrome is rare. 1, 4

Clinical Presentation

Patients with Eagle syndrome typically present with a constellation of symptoms including:

• Throat and neck pain with radiation to the ipsilateral ear 4, 2
• Pharyngeal foreign body sensation 1, 4
• Dysphagia and odynophagia 1, 3
• Pain upon head movement or rotation 1, 5
• Facial pain (often unilateral) 4, 2
• Headache and retroauricular pain 1, 5
• Dysphonia, voice changes, and cough 4, 3
• Dizziness or vertigo 3

A critical diagnostic clue is that symptoms are exacerbated by head rotation and digital palpation of the styloid process in the tonsillar fossa. 2

Mechanism of Development

The exact etiology of styloid process elongation remains unclear, but potential mechanisms include:

• Congenital elongation of the styloid process 1
• Calcification of the stylohyoid ligament (which connects the styloid process to the hyoid bone) 1, 4
• Post-traumatic ossification following pharyngeal trauma 2
• Chronic inflammatory changes leading to reactive bone formation 2

Diagnostic Approach

Diagnosis requires correlation of clinical history, physical examination findings, and imaging confirmation: 1

• Physical examination: Digital palpation of an elongated styloid process in the tonsillar fossa that reproduces or exacerbates the patient's pain is highly suggestive 2
• Anesthetic test: Relief of symptoms following injection of local anesthetic into the tonsillar fossa strongly supports the diagnosis 2
• Imaging: Anterior-posterior and lateral skull radiographs can demonstrate elongation, but computed tomography (CT) provides superior visualization and documentation of the styloid process length and any ligamentous calcification 2, 5

Common Pitfalls

Eagle syndrome is frequently misdiagnosed because its symptoms overlap with numerous other conditions causing orofacial and neck pain. 3 Clinicians should maintain a high index of suspicion in patients with persistent throat pain, especially when accompanied by foreign body sensation and pain on head rotation. 4, 3

The syndrome was notably mentioned in tonsillectomy guidelines as a rare complication presenting as persistent neck pain post-operatively, highlighting the importance of considering this diagnosis in the post-surgical setting. 6