Eagle Syndrome

A specific orofacial pain secondary to calcification of the stylohyoid ligament or elongated styloid process has been known as Eagle syndrome (ES) since 1937, when an otolaryngologist at Duke University, Watt W. Eagle, described the first cases. This syndrome was characterized by symptoms typically occurring after pharyngeal trauma or tonsillectomy. It manifests as a nagging dull, long-term ache in the throat, sometimes radiating to the ipsilateral ear and the sensation of a foreign body in the throat. Occasionally, it manifests as odynophagia, dysphonia, increased salivation, and headache. Not rarely, patients believe that they have not properly healed from their tonsillectomy.

In the ensuing years, the term "styloid syndrome" was created to describe a cervico-pharyngeal pain related to the styloid process when no previous history of trauma was found.

Frequency

An elongated styloid process occurs in about 4% of the general population, while only a small percentage (between 4-10.3%) of these patients are symptomatic. ^[13] So the true incidence is about 0.16%, with a female-to-male predominance of 3:1. Bilateral involvement is quite common but does not always involve bilateral symptoms. No significant difference is detectable between the right and left sides.

This topic is still being debated. Eagle considered surgical trauma (tonsillectomy) or local chronic irritation could cause osteitis, periosteitis, or tendonitis of the stylohyoid complex with consequent reactive, ossifying hyperplasia. ^{[14, 13]} Lentini (1975) formulated the hypothesis that persistence of the mesenchymal elements (Reichert cartilage residues) could undergo osseous metaplasia as a consequence of trauma or mechanical stress during the development of the styloid process. ^[15] Epifanio (1962) considered that the ossification of the styloid process was related to endocrine disorders in women at menopause, accompanied by the ossification of ligaments elsewhere (eg, iliolumbar, thyrohyoid). ^[16]

Gokce C et al reported that ectopic calcification (EC) might have a role for the elongation of the styloid process, especially in patients with abnormal calcium (Ca), phosphorus (P), and vitamin D metabolism (as in end-stage renal disease). ^[17]

A retrospective study by Bruno et al indicated that chronic calcification is behind elongation of the styloid process, with the investigators finding, in an assessment of 1003 digital panoramic radiographs, that the number of patients with an elongated styloid process and the mean process length grew higher with increasing patient age. ^[18]

A retrospective study by Sekerci et al indicated that a correlation exists between the presence of a ponticulus posticus (also called an arcuate foramen) and an elongated styloid process. Results were derived using three dimensional (3-D) cone-beam computed tomography (CT) scans from 542 patients. ^[19]

A literature review by Saccomanno et al indicated that an association exists between trauma and the onset of Eagle syndrome symptoms. The investigators suggested that the styloid process, already elongated, or the stylohyoid ligament, already calcified, may be fractured by a traumatic event. As a result of styloid process fracture, granulation tissue may proliferate, compressing adjacent structures. A second possibility is that the adjacent noble structures and pharyngeal mucosa are directly irritated or compressed by the fractured element. In another scenario, however, instead of resulting in fracture, trauma activates pathophysiologic mechanisms that cause the styloid process to lengthen or the stylohyoid ligament to calcify. ^[20]

Eagle considered tonsillectomy responsible for the formation of scar tissue around the styloid apex, with consequent compression or stretching of the vascular and nervous structures contained in the retrostyloid compartment (in particular, the glossopharyngeal nerve and perivascular carotid sympathetic fibers). However, Eagle syndrome is also discovered in patients who have never been subjected to tonsillectomy. So many other factors have been considered, such as the following:

• The ossification of the stylohyoid ligament complex, causing contraction of the stylopharyngeal muscle and stretching of the XII cranial nerve ^[9]

• The fracture and medialization of the ossified stylohyoid ligament, with incomplete repair due to continuous hyoid bone movements and formation of excessive granulation tissue ^[3]

• The ossification of muscular tendons leading to irritation of the structures nearby ^{[4, 5]}

• The abnormal length associated with abnormal angulation of the styloid process ^{[21, 22]}

In 1937, Eagle described 2 possible clinical expressions attributable to elongated styloid process, as follows:

• The “classic Eagle syndrome” is typically seen in patients after pharyngeal trauma or tonsillectomy, and it is characterized by ipsilateral dull and persistent pharyngeal pain, centered in the ipsilateral tonsillar fossa, that can be referred to the ear and exacerbated by rotation of the head. A mass or bulge may be palpated in the ipsilateral tonsillar fossa, exacerbating the patient’s symptoms. Other symptoms include dysphagia, sensation of foreign body in the throat, tinnitus, or cervicofacial pain.

• The “second form” of the syndrome (“stylocarotid syndrome”) is characterized by the compression of the internal or external carotid artery (with their peri-vascular sympathetic fibers) by a laterally or medially deviated styloid process. It is related to a pain along the distribution of the artery, which is provoked and exacerbated by rotation and compression of the neck. It’s not correlated with tonsillectomy. In case of impingement of the internal carotid artery, patients often refer supraorbital pain and parietal headache. In case of external carotid artery irritation, the pain radiates to the infraorbital region.

A study by Bai et al reported that in Eagle syndrome patients in whom styloid process compression caused internal jugular vein stenosis (IJVS), the most common symptoms included insomnia (81.5%), tinnitus (63.0%) and head noises (63.0%). The investigators also found that 68.8% of patients with bilateral IJVS suffered hearing impairment, compared with 18.2% of those with unilateral stenosis. ^[23]

A variety of head and neck conditions should, however, be considered in the differential diagnosis of Eagle syndrome (ES) and cervicopharyngeal pain. These include the following:

• Temporomandibular disorders

• Laryngopharyngeal dysesthesia

• Hyoid bursitis

• Sluder syndrome

• Glossopharyngeal neuralgia

• Esophageal diverticula

• Trigeminal neuralgia

• Migraine-type headaches

• Sphenopalatine neuralgia

• Cervical arthritis

• Temporal arteritis

• Glossodynia ^[24]

• Unerupted or impacted molar teeth

• Faulty dental prostheses

• Otitis

• Salivary gland disease

• Possible tumors

• Cervical mass ^[25]

• Transient ischemic attacks ^[26]

• Carotid artery dissection ^[27]

One case of sudden death due to Eagle syndrome is also reported, caused by the mechanical irritation of the carotid sinus by an elongated styloid process with consequent acute cardiovascular failure. ^[28]

Only severe cases, which do not respond to analgesics and anti-inflammatory

medications, require surgery.

• Intraoral approach

  • Advantages

    • Avoids external scarring

    • Less time consuming

  • Disadvantages

    • Risk of deep space neck infection

    • Poor visualization of the surgical field

    • Major risk of iatrogenic injury to main neurovascular structures

    • Poor hemorrhage control

    • Alterations of speech and swallowing for postoperative edema

    • Difficult in patients with markedly decreased jaw opening

• Extraoral approach

  • Advantages

    • Better visualization of the surgical field

    • Greater intraoperative sterility

  • Disadvantages

    • More time-consuming

    • Risk of injury of facial nerve structures

    • Neck scar

    • Longer recovery

Styloid process is derived from the Greek word stylos, meaning a pillar. The structure is a long, cylindrical, cartilaginous bone located on the inferior aspect of temporal bone, posterior to the mastoid apex, anteromedial to the stylomastoid foramen, and lateral to the jugular foramen and carotid canal. Medial to the styloid process is the internal jugular vein along with cranial nerves VII, IX, X, XI, and XII. The tip of the styloid process is close to the external carotid artery laterally, while medially, it is in close proximity to the internal carotid artery and accompanying sympathetic chain. It forms with the stylohyoid ligament and the small horn of the hyoid bone, the stylohyoid apparatus, which is derived from the cartilage of Reichert of the second brachial arch. Three muscles originate from the styloid process: the styloglossal, stylohyoid, and stylopharyngeus. The styloid and the stylomandibular ligaments are also attached to the styloidprocess. ^{[29, 30]}