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]

Blood work is required to exclude possible systemic diseases. A complete blood count (CBC) is obtained if infection is suspected.

Lateral view radiographs of the skull can be substituted for panoramic radiographs of the mouth; the disadvantage of this view is the overlapping between styloid processes of both sides and/or with adjoining bony structures. An antero-posterior view radiograph should be obtained to determine whether the styloid process is medially or laterally deviated.

An advantage of orthopantomogram (panoramic view) is that the entire length of the process can be seen very distinctly and its deviation can also be made out clearly. Although conventional radiographs provide a rough idea of the anatomy, the actual diagnosis is difficult due to the superimposed anatomical structures.

CT scanning (and in particular 3-D CT scanning; see images below) represents an extremely valuable imaging tool in patients with Eagle syndrome, offering an accurate evaluation of the styloid process in relation to its anatomical relationship with the other head and neck structures, to its length and to its usefulness in surgical planning.

CT scan: calcification of the stylohyoid ligament.

Three-dimensional reconstruction CT scan.

CT scanning of the skull base and neck is best for diagnosis, although an accurate case history and the specialist’s intuition are also important for the differential diagnosis.

Three-dimensional cone-beam CT is an excellent alternative to study the styloid process.

A study by Kent et al suggested that the distance from the tip of the styloid process to the tonsillar fossa may be a better diagnostic criterion for Eagle syndrome than the actual length of the styloid process. Using conventional and 3-D CT scanning analysis in persons with Eagle syndrome, glossopharyngeal neuralgia, or neither condition (asymptomatic controls), the study found that the average distance from the tip of the styloid process to the tonsillar fossa was significantly smaller in the Eagle syndrome cases (12.7 mm, versus 21.4 mm and 24.8 mm, respectively). Moreover, no significant difference was found in the average length of the styloid process between each group of subjects.[31]

Reproduction of the patient’s pain on palpation of the tonsil or tonsillar fossa and relief of this discomfort by injection of local anesthetic are diagnostic. In the lidocaine infiltration test, 1 mL of 2% lidocaine is infiltrated into the anterior pillar and deep into the tonsillar fossa; after a few minutes, if the patient’s symptoms are relieved temporarily, the test is regarded as positive, confirming the diagnosis of Eagle syndrome.[32]

Medical management includes the following:

• Analgesics

• Anticonvulsants

• Antidepressant

• Local infiltration with steroids or long-acting local anesthetic agents[12]

The two traditional surgical approaches to styloidectomy (removal of the elongated portion of the styloid process) are the intraoral approach (or transpharyngeal) and the extraoral approach.

Eagle introduced and preferentially used the intraoral transpharyngeal approach. Manual fracture of the styloid process was also proposed.[33] This technique should be avoided because it often does not relieve the symptoms and needlessly endangers important surrounding structures.

See Indications.

Intraoral approach

The surgeon locates the styloid process by digital palpation of the tonsillar fossa. After the incision and the identification of the styloid process, it is necessary to split the muscles, to elevate the mucoperiosteum, and, finally, to fracture and excise the styloid process. If the pharyngeal tonsil is present, performing tonsillectomy first during the same operation is necessary.

The advantages of the intraoral approach are that the method is safe, simple, less time consuming, and an external scar is avoided. The disadvantages are possible infection of deep neck spaces, risk of injury to major vessels, and poor visualization. Intraoral resection of the styloid process is a safe technique, but it is not recommended with bilateral intervention at the same surgery, because of possible great discomfort postoperatively.[32, 34]

A study by Torres et al of a modified, tonsil-sparing transoral approach to removal of an elongated styloid process, as performed in 11 patients with Eagle syndrome involving the carotid artery, found that 10 of the patients experienced complete symptom relief and functional improvement. No intraoperative or postoperative complications were reported in any of the cases.[35]

A study by Fitzpatrick et al indicated that in patients with Eagle syndrome, transoral robotic styloidectomy leads to symptom improvement similar to that derived through traditional transoral and transcervical techniques, while being associated with reductions in length of hospital stay, blood loss, and operative time.[36]

Extraoral approach

The external approach starts with a cervical incision at the upper two thirds of the anterior margin of the sternocleidomastoid muscle to the hyoid bone. After identification and incision of the platysma muscle and the superficial cervical fascia, the parotid fascia is reflected anteriorly and the carotid sheath and the sternocleidomastoid posteriorly in order to reach the posterior belly of the digastric muscle and the vascular-nervous bundle of the neck. The styloid process can now be palpated. Aponeurotic and muscular insertions are separated from the styloid process. Styloidectomy is then performed. Ceylan et al reported a 93.4% of success after external resection.[32, 37]

A study by Heim et al suggested that Eagle syndrome can be safely and effectively treated with a cervical approach, with a survey of four patients who underwent the procedure finding them to be asymptomatic at mean 53.75-month follow-up. No visible scarring or hypoesthesia in the involved area was reported by the patients.[38]

A retrospective study by Jalisi et al indicated that either transoral or transcervical styloidectomy represents an effective treatment for long-standing Eagle syndrome, with the report, in which each approach was used on three patients, finding complete symptom resolution in all six cases.[39]

A retrospective cohort study by Chen et al indicated that an elongated styloid process can also be addressed using an endoscope-assisted styloidectomy carried out through a retroauricular incision. Complete symptom relief was found in 107 of 133 patients (80.5%), with partial symptom relief achieved in 20 patients (15%).[40]

For the intraoral approach, patients usually start to take oral soft foods after 4-6 hours, and they are discharged 8-24 hours after surgery. For external approach, patients are usually discharged 36 hours after surgery.

All patients take oral antibiotics and analgesics for 1 week.[32]

Patients are followed up for at least 1 year (12-20 months) and are examined every 3 months during the first year.[32]

The main surgical complications associated with styloidectomy are as follows:

• Deep space neck infection

• Injury to main neurovascular structures

• Hemorrhage

• Temporary alterations of speech and swallowing

• Injury of the facial nerve

The overall success rate for treatment (medical or surgical) is about 80%.

The failure of treatment may be associated with the presence of other causes involved in the pathogenesis of the problem (multifactorial etiology).