Year : 2008 | Volume
: 20 | Issue : 1 | Page : 1--5
Eagle syndrome: A review of current diagnostic criteria and evaluation strategies
Vishlesh Arora, Arvind Shetti, Vaishali Keluskar
Department of Oral Medicine and Radiology, Institute of Dental Sciences, Belgaum, Karnataka, India
Department of Oral Medicine and Radiology, Institute of Dental Sciences, Belgaum, Karnataka
The mineralized and elongated styloid process and Eagle«SQ»s syndrome are similar processes of elongation in which mineralization of the stylohyoid ligament leads to styloid process of the temporal bone. The mineralized and elongated styloid process and Eagle«SQ»s syndrome differ significantly in terms of the symptoms displayed and the treatment modalities that are sought. The mineralized and elongated styloid process refers to unilateral or bilateral elongation of the styloid process that does not result in any significant pain, discomfort, or limitation of neck movement. It often remains asymptomatic until it is discovered on extraoral radiographs. Eagle«SQ»s syndrome refers to pain and discomfort in the cervicofacial region resulting specifically from the elongated styloid process. Surgical shortening may be the only treatment that will alleviate the patient«SQ»s symptoms.This article reviews the entire process of elongation pertaining to the styloid process and discusses the associated syndromes, including current knowledge of the theories of elongation, diagnostic criteria and treatment strategies.
|How to cite this article:|
Arora V, Shetti A, Keluskar V. Eagle syndrome: A review of current diagnostic criteria and evaluation strategies.J Indian Acad Oral Med Radiol 2008;20:1-5
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Arora V, Shetti A, Keluskar V. Eagle syndrome: A review of current diagnostic criteria and evaluation strategies. J Indian Acad Oral Med Radiol [serial online] 2008 [cited 2021 Oct 16 ];20:1-5
Available from: https://www.jiaomr.in/text.asp?2008/20/1/1/44352
The styloid process of the temporal bone lies anterior to the stylomastoid foramen. It is attached by cartilaginous tissue. The process normally measures 25 mm in length, although it varies in length from person to person and even from side to side of the same person. ,,
Although researchers agree that elongation is common, symptoms associated with elongation are uncommon unless the calcification has progressed through the stylohyal complex to induce symptoms. Diagnosis is a clinical challenge for general dentists when the symptoms appear, as symptoms may emerge in a variety of manifestations. Common symptoms include foreign body sensation in the throat, dysphagia, and intermittent facial pain related to the mineralized and elongated styloid process (MESP). Various studies have reported incidence of the MESP ranging from 1.4-30%.
Elongation usually results from ossification within the stylohyoid ligament. The ossification usually occurs in the upper end of the ligament and is in keeping with the styloid process, although it has been reported as starting at the lower end of the stylohyoid ligament, at the lesser cornu of the hyoid bone, and, less commonly, in the mid-portion.  Subjects with elongated styloid processes at least 40 mm long had the highest incidence of discomfort on swallowing. The majority of patient with styloids less than 30 mm were symptom-free.
Anatomic and Embryological Considerations
The styloid process normally projects down, forward and slightly medially. The tip of the process is situated between the internal and external carotid arteries. It lies posterior to the tonsillar fossa and lateral to the pharyngeal wall; muscular and ligamentous structures are attached at various locations on the process. Three muscles are attached to the process, the stylopharyngeus (arising from the base and innervated by the glossopharyngeal nerve), the stylohyoid (attached to the middle portion and innervated by the facial nerve), and the styloglossus (originating from the extremity of the process and innervated by hypoglossal nerve).
The two ligaments in relation to the process are the stylomandibular and the stylohyoid. The stylomandibular ligament is inserted at the apex of the process and attaches at the angle of the mandible. The stylohyoid ligament inserts to the apex of the process and attaches at its far end to the lesser cornu of the hyoid bone. The stylohyoid chain consists of the styloid process, the lesser cornu of the hyoid bone, and its connecting ligament (usually the stylohyoid ligament). The chain is derived from the second branchial or hyoid arch known as Reichert's cartilage. In many mammals, this cartilage gives rise to a series of four bony parts: the tympanohyal, stylohyal, epihyal and ceratohyal.  In humans, it is believed that the tympanohyal fuses with the stylohyal and the petrous part of the temporal bone to form the styloid process. Normally, the epihyal cartilage degenerates but its fibrous sheath remains; this sheath is the stylohyoid ligament.  The ceratohyal or hypohyal cartilage persists and becomes the lesser cornu of the hyoid bone.  Variation in the ossification and fusion of these various parts can result in marked variation in the chain's appearance.
In 1964, Lengele and Dhem proposed the developmental theory about the elongated styloid process, based on the morphogenesis of Reichert's cartilage.  To establish the mechanisms involved in the morphogenesis of the so-called elongated styloid process, a comparative microradiographic and histological study was performed on 19 long and short processes. Some morphological differences between short and long processes were noticed. Numerous partially calcified cartilaginous islets were observed within the trabecular bone of very long styloid processes or covering their tip. Although calcified fibrous tissue or calcified fibrocartilage sometimes contributed to the thickening of an enlarged styloid process, the authors reported that the growth of the process did not seem to result from calcification or ossification of the stylohyoid ligament. Mechanical stresses stretch the second branchial arch during fetal development and the morphogenesis of the styloid process may induce a variable involvement from the different parts of Reichert's cartilage. Lengele and Dhem concluded that the elongated styloid process should he congenital; however, they agreed that further growth still was possible through the cartilaginous cap of the tip of the styloid process. 
Clinical Features and Examination
According to studies performed on the elongated styloid process between 1964 and 1986, symptomatic patients usually were over the age of 40. , There was no sex predilection in the majority of the studies. When pain and discomfort upon swallowing, foreign body sensation in the throat, or a limitation of mandibular movements appear to be associated with the radiographically detectable MESP, the condition known as Eagle's syndrome (also known as elongated styloid process syndrome) is diagnosed.
An extensive review concerning the association between cervicopharyngeal pain and stylohyoid ossification placed patients in three broad categories based on their symptoms (the stylohyoid, pseudostylohyoid, or Eagle's syndromes).  The same study reported that Eagle's syndrome typically involves patients with a recent history of neck trauma or surgical procedures (for example, a tonsillectomy) who show radiographic evidence of an elongated styloid process. Clinical palpation of such elongation or calcification usually can be performed chairside. Patients may complain of sensation of a foreign body in the throat, pain on swallowing, or neurologic pain in the head and neck region; they also may have significant pain in the temporomandibular joint (TMJ) region, radiating to the sub-auricular and submandibular regions. The term stylohyoid syndrome applies to patients of any age, although most usually are older than 40 at the time of diagnosis; while these patients may not have significant symptoms, the ossification can be demonstrated on routine extraoral radiographs.  Such ossification also may be palpable clinically.
Pseudostylohyoid syndrome is reserved for patients older than 40 who have no history of trauma and no radiographic or clinical evidence of stylohyoid chain ossification. These patients have symptoms identical to those of stylohyoid syndrome patients but do not have radiographic or clinical findings of ossification within the ligament. It is proposed that these people have tendonitis at the junction of the stylohyoid ligament and the lesser horn of the hyoid bone resulting from the degenerative and inflammatory changes in the tendinous portions of the stylohyoid insertion. 
Langlais et al . reported on a subgroup of patients with constant parietal headaches; these patients were theorized as having a "stylo-carotid syndrome."  The differential diagnosis depends on the symptoms. The most common inclusions are glossopharyngeal neuralgia, sphenopalatine neuralgia (also known as Sluder's syndrome), histamine cephalgia (cluster headaches), migraine headaches, carotidynia, myofascial pain dysfunction, impacted third molars, and other conditions associated with dysphagia, otalgia and tinnitus. 
The effects of hyperflexion/hyperextension (that is, whiplash) injuries are exacerbated by the presence of this unexpected calcified structure. Researchers have correlated the ligamentous ossification of the stylohyal complex and osteophytes of the cervical spine, concluding that a significant correlation exists between cervical diffuse idiopathic skeletal hyperostosis (DISH) and various styloid process-stylohyoid ligament complex abnormalities. 
The examination of the styloid region can be performed by seating the patient in a chair with firm back support. The palpation of the styloid region of the neck can be conducted bimanually and digitally by standing behind the patient. An intraoral examination method includes visualizing the tonsillar area with a tongue blade or a mouth mirror and digital palpation of the area. Patients whose referred pain is in the tonsillar area will be able to respond to the palpatory stimulus.
Radiographic Features and Classification
Elongation and mineralization of the stylohyoid ligament complex can be observed readily on panoramic radiographs [Figure 1]. However, because the panoramic radiographs are obtained primarily for the visualization of teeth and associated bony structures within the jaws, observing the mineralized stylohyoid complex within the pantomograms is inconsistent and often distorted. This is due to the fact that the styloid process frequently lies outside of the panoramic focal trough depending on the patient positioning. The images become distorted due to the unreliable magnification within the posterior focal trough of the panoramic machines. Lateral skull view, reverse Towne view [Figure 2] and posterior-anterior views of the skull also demonstrate the unilateral or bilateral presence and elongation of the styloid process. The mineralized stylohyoid ligament is easy to recognize when it extends below the mandibular border or when its attachment to the mandibular cornu of the hyoid bone can be seen on the radiographs.
Radiographic features alone are not enough to distinguish the symptomatic from the asymptomatic elongated styloid processes. When the posteroanterior radiographs show extreme medial deviation, the carotid artery subtype may be considered.  Langlais et al. proposed a radiographic classification of the elongated and mineralized stylohyoid ligament complex. Their classification included three types of abnormal radiographic appearances and four patterns of calcification/mineralization [Figure 3] (see [Table 1] and [Table 2]).
Diagnosis and Management
An elongated styloid process may be one cause of aggravated maxillofacial or craniocervical pain. Diagnosis requires a thorough clinical examination of the head and neck and should be confirmed radiographically. Panoramic radiographs or bilateral lateral oblique radiographs should be taken for patients who are examined in a dental office setting for oropharyngeal discomfort, chronic cervicofacial pains, or chronic headaches. Radiographically, the mineralized styloid process falls under any of the aforementioned types of elongation or the patterns of mineralization. The outcomes of treatment have no bearing on the type of elongation or pattern of mineralization. The classification is designed to help dentists understand the variation among the different elongation patterns and may even offer clues as to the etiology of the elongation.
Eagle's syndrome can be a secondary cause of glossopharyngeal neuralgia. Glossopharyngeal neuralgia may be a life-threatening condition as a result of associated cardiovascular complications. Even when life-threatening complications are absent, glossopharyngeal neuralgia can be a severely debilitating disease, leading to depression, suicidal tendencies, fear of swallowing, weight loss and malnutrition. Due to the elongated styloid process, Eagle's syndrome is considered an important etiological factor for precipitation of secondary glossopharyngeal neuralgia.  A stylectomy is effective for Eagle's syndrome and should be considered before embarking on any neurosurgical procedure.
The effects of hyperfiexion/hyperextension/whiplash injuries can be exacerbated by the presence of the calcified styloid. Additional symptoms may include neck or throat pain radiating to the ipsilateral ear. Diagnosis usually can be made by physical examination. Digital palpation of the styloid process in the tonsillar fossa exacerbates the pain. This diagnosis should be considered if symptoms can be . relieved by injecting an anesthetic solution in to the tonsillar fossa.
Surgical shortening is the universally accepted treatment for confirmed elongation of the styloid process. Multidisciplinary management yields optimal results; some studies have recommended an intraoral approach (that is, trans-tonsillar fossa excision). Other authors have preferred an extraoral cervical approach, believing that surgical visualization was optimal and the risk of deep cervical infection was minimal. Trans-tonsillar fossa excisions is a simple technique that does not result in greater morbidity than a routine tonsillectomy, although the trans-tonsillar approach has been criticized for inadequate surgical shortening of the styloid process due to poor visualization of the surgical field. Dentists must weigh the advantages and disadvantages of each technique and select the procedure that is appropriate for the patient.
Cases in which a MESP alone is present do not require any immediate treatment, although patients should be warned about the elongation of the styloid process.
Although the elongated styloid process is not an entirely new entity, studies of symptomatology and diagnostic strategies involving different population groups have produced new information about the various types of elongation, patterns of calcification, and symptomatology. When evaluating the chronic orofacial or cervicofacial pain, elongation of the styloid process should always be considered. Proper selective radiographic techniques and examination of the tonsillar and cervical areas may reveal elongation or mineralization in the stylohyoid complex, which may be the cause of the elongated styloid process. The styloid elongation should be included in the list of differential diagnoses for evaluating headaches, tonsillar discomfort, pain referred to the jaw region, difficulty in swallowing and the inability to move the jaw from side to side during lateral excursions. Symptomatic cases of stylohyoid elongations should be referred to as Eagle's syndrome. When complex patterns of stylohyoid chain mineralization appear on plain radiographs and tomograms with no signs of disabling symptoms, mineralized and elongated styloid process may be the more appropriate diagnosis.
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