Eagle syndrome . A narrative review

ISSN Online 0719-2479 ©2016 Official publication of the Facultad de Odontología, Universidad de Concepción www.joralres.com 248 1. Escuela de Odontología, Universidad Particular de Chiclayo. Chiclayo, Perú. 2. Escuela de Estomatología, Universidad Señor de Sipán. Chiclayo, Perú. 3. Centro de Salud Odontológico San Mateo. Trujillo, Perú. 4. Escuela de Estomatología, Universidad Privada Antonio Guillermo Urrelu. Cajamarca, Perú. 5. Facultad de Estomatología, Universidad Nacional de Trujillo. Trujillo, Perú. 6. Facultad de Odontología, Universidad San Martín de Porres – Filial Norte. Chiclayo, Perú.


INTRODUCTION.
Eagle Syndrome (ES) or Stylohyoid syndrome is an unusual pathology of the head and neck, which produces orofacial pain.0][21][22][23][24] ES is part of musculoskeletal disorders related to the temporomandibular joint; masticatory and cervical muscles as well as associated structures. 1,86][27] However, ES is frequently underdiagnosed due to its low prevalence and inadequate knowledge of craniofacial and cervico-pharyngeal syndromes.Moreover, as its symptoms are varied, health professionals and patients tend to confuse this disease with other disorders.The aim of this review is to describe the general aspects, diagnosis and treatment of Eagle syndrome.cribed by Watt W. Eagle in 1937, [28][29][30] who defines it as the relationship between the elongation of the styloid process and the calcification of the stylohyoid ligament resulting in pain related to the cranial and sensory nerves of the oropharynx, neck and ear.
This syndrome has three historical periods: the first one began 364 years ago with the first report of ossification of the stylohyoid process reported by Marchetti in 1652. 7,8,10,19,23wo centuries later, in 1852, Demanchetis 2,5 describes a calcified stylohyoid ligament.Eighteen years later in 1870, 1,4,18 Lucke relates this calcification with a painful syndrome.Weinlecher in 1872, 14,15,31 first reports pre and postoperative clinical symptoms of ossification of the styloid process.Sterling, in 1896, 1,5 reports a clinical case of elongated styloid process.Dwight, in 1907, 1,5 classifies stylohyoid complex anatomy, based on radiographs, finding ossification with clinical symptoms.Thigpen 19321, 5 reports eleven cases of elongated stylohyoid processes.Finally, Eagle described the syndrome in 1937, [28][29][30]32 and reported two cases related to an abnormal styloid process with pharyngeal and facial symptoms caused by irritation of the carotids.
The second period corresponds to the development of radiographic diagnosis, when Grossman correlates pains of the stylohyoid complex, including dysphagia, otalgia, estilalgia, headache, pain in the temporomandibular joint, and various forms of facial pain, with elongation of styloid process. 1,16The third period corresponds to the development of panoramic radiography and computed tomography, which allow better visualization of various structures of the maxillofacial complex. 31,33,34

CHARACTERISTICS AND ANATOMICAL RE-LATIONSHIPS
Styloid process or styloid apophyisis, is a word originating from the Greek "Stylos" which means "pillar".It is a bony projection of 2 to 2.5cm. 1,13,24,357][38] It belongs to the temporal bone from its lower surface at the junction of the petrous and tympanic portions below the external auditory meatus and anterior to the mastoid process. 15,16,19,31e styloid process is usually located between the internal and external carotid arteries 7,26,36 and allows the insertion of the stylopharyngeus, stylohyoid and styloglossus muscles, 9,24,30 and also of the stylomandibular ligaments. 11,33he stylohyoid ligament originates from the tip of the process and is inserted into the horn or lesser horn of the hyoid bone, 23,31,34 and the second originates from the medial part of the process and is directed forward and down to the inner surface of the mandibular gonial angle. 33,38,39

CLASSIFICATION
Eagle suggests that the normal length of the styloid process is approximately 25mm, 6,7,20,26 therefore any length exceeding that size would be considered elongated. 1,8,9,32owever, other authors, in current studies, indicate that the length of the styloid is variable. 4,29,30,31They agree that a styloid process exceeding 30mm should be considered elongated. 13,18,23,27,34,35,39ccording to the symptoms, Eagle describes two types of syndrome: the classical or typical syndrome associated with carotid artery and the atypical one. 13,25,35,36,38The first type occurs in patients with previous tonsillectomy 12,25,27,40 and is related to the extension of nerve endings, mainly cranial nerve IX (glossopharyngeal), 1,14,22 causing constant or dull pain in the pharyngeal region that often radiates to the ear resulting in dysphagia, 9,35,36 foreign body sensation in the throat, 9,19,21 increased salivation, 4,11,30 nausea, 1,4 facial and neck pain (unilateral), 1,18,31 trismus and limited mandibular lateral excursion. 1,30Eagle attributed the paint to the scarring process around the styloid process after a tonsillectomy. 2,4,30he second type would be present in patients with or without tonsillectomy, 1 and occurs when the styloid process contacts the external carotid artery on the affected side, 14,22,30 resulting in carotodynia (pain caused by compression of the carotid and referred to the neck and to the area around the eyes), 18,25,31 intermittent headache in the frontal, 4,11 temporal 1,4,35 or parietal 12,17,25 regions, earache 35,40 and dizziness, 40 and tenderness on palpation in the area of the carotid artery. 35,40Pain would be asso-ciated with pressure on sympathetic fibers of perivascular carotid artery, 13,16,27,38 as well as elongation and calcification of stylohyoid complex, 1,25 causing a transient ischemic event, 2,22,31 a stroke 2,25,36 and even death. 12,14,19,21olby and Del Gaudio, 16 developed a new classification based on cone beam computed tomography (CBT), dividing it into: elongated styloid process, ossified stylohyoid ligaments and elongated hyoid bone.Langlais et al. 1,36,40,41 made a classification for elongation and calcification patterns of the stylohyoid complex by radiographic appearance.Three radiographic patterns are known: 1. Type I or elongated 1,23,24 : This calcified stylohyoid complex is characterized by a continuous styloid process. 36,41If the study is conducted by observing panoramic radiographs, a length of 28mm is accepted, taking into account the normal magnification affecting this type of radiographs. 4,40. Type II or pseudoarticulated 1,23,24 : In this radiographic image, the styloid process is attached to the stylomandibular ligament or to the stylohyoid ligament by a pseudoarticulation, 36 which is located on the lower edge of the mandible (tangentially).This gives the appearance of an articulated and elongated complex. 4,40,413. Type III or segmented 1,23,24 : It consists of short or long portions of the styloid process that are discontinuous or interrupted segments of the mineralized ligament.36,40 Two or more segments are observed, with interruptions either above or below the lower border of the mandible, or both.4,41 Also, according to the pattern of calcification, four patterns can be determined: 1. Calcified contour 1,23,24,41 : A radiopaque and thin edge with a central radiolucency comprising most of the process is observed, 4,40 giving the radiographic appearance of a long bone. 34,40. Partially calcified 23,24,41 : It indicates that the process has a radiopaque and almost completely opaque contour, however, it may have discontinuous radiolucent centers.1,4,34,40 3. Nodular complex 23,24,41 : It is characterized by an undulating or scalloping contour, partially or completely cal-cified with varying degrees of central radiolucency.1,4,34,40 4. Completely calcified 1,4,23,40 : It is totally radiopaque.24,34,41

EPIDEMIOLOGY
Lirios 1 states that the prevalence of an elongated styloid process has great variability in the population.Eagle, in its original publication, found the elongated styloid process in 4% of his cases. 2,4,13,16,29,30,38,42t is estimated that between 3 and 30% of the world population has elongated styloid process, and of them, from 4 to 10.3% suffer from painful symptoms. 1,14,36The wide variation in the prevalence of elongated styloid process evidenced in different studies can be explained by variations in diagnostic criteria and interpretation of images, geographic location and characteristics of the local population. 37hen comparing both processes, findings suggest that bilateral elongations are more frequent, 15,25,29,33,41 larger on the right side. 1,38Studies indicate that the highest prevalence of the disease is found in women (3:1) 4,10,18,28 and in the age range of 30 to 50 years. 12,13

SYMPTOMATOLOGY
A wide variety of symptoms have been associated with the elongation of the styloid process, including an intense facial pain, 3,5 nonspecific cervical pain or during rotation of the head, headaches, sore throat, ear pain, dysphagia or odynophagia, 6,7,19 pain by extending the tongue, burning sensation on the tongue, pain when opening the mouth, discomfort during chewing, difficulty to speak, voice change, 8,9,32 sensation of hypersalivation, foreign body sensation in the throat, tinnitus, trismus, syncope, submandibular swelling and brain vascular symptoms induced by the change of position. 13,14,36Pain is the main characteristic of this condition.It is constant and distressing, and can last from minutes to days. 25,26,31Also, most patients experience this discomfort unilaterally. 18,28,41owever, most patients with ES are asymptomatic. 36,43[24]

ETIOPATHOGENESIS
Pathogenesis is caused by the compression of the glossopharyngeal nerve and associated vascular structures, because of the enlarged process. 5,9,26,32The etiology is still unknown, 21,24,29 however, there are different theories that attempt to explain it. 17,18,30teinmann 2,4,13,33 proposed three theories to explain the process of ossification: 1. Theory of reactive hyperplasia, which suggests that surgery or chronic irritation of the throat can cause tendinitis, ossifying periostitis or osteitis in the stylohyoid ligament. 17. Theory of reactive metaplasia (Heteromorphosis) associated with a partial ossification of fibrocartilaginous tissue of the stylohyoid ligament, usually in response to a previous trauma. 17. Theory of anatomical variation: it proposes that early elongation of the styloid process and ligament ossification are anatomical variations which occur without the presence of previous trauma; this would explain the presence of ossification in children. 30n addition, there is a theory involving congenital elongation, 21 which is the most accepted model, and explains that ES is the result of the persistence of embryonic mesenchymal sheet capable of producing bone tissue in adults; 21,29 and ossification of stylohyoid ligament related to mechanical stress during fetal development. 9,13n rare cases they are associated with endocrine disorders (menopause). 17,30One study reports the possibility that ES could be the result of the expression of an autosomal dominant gene. 13,43urthermore, it has been explained that the cause of pain symptoms is the relationship of the stylohyoid complex with anatomical structures, 1,5,20 such as muscles, nerves, arteries, veins, fasciae and increased length of styloid process, as it can lead to irritation and inflammation of those structures. 21,29,42There are some mechanisms that may explain the cause of pain produced by ES, such as: 1. Secondary mechanical irritation of the pharyngeal mucosa. 13,14,36. Extension of nerve endings of cranial nerves V, VII, IX and X, resulting from the fibrosis that occurs after tonsillectomy. 13,14,36. Fracture of the calcified stylohyoid ligament, 15,31,33 caused by cervical trauma or a sudden movement of the neck, with the consequent proliferation of granulation tissue that can cause pressure on the structures surrounding the stylohyoid complex.16,37,41 4. Pressure on the carotid artery, with stimulation of the sympathetic chain involving the carotid sheath. 1 5. Degenerative changes in the insertion of the stylohyoid muscle or insertion tendinitis.17,18,30

DIAGNOSIS
Diagnosis of ES is based on four parameters: clinical manifestations, digital palpation of the styloid process, lidocaine infiltration test, and radiological findings. 1,25herefore a correct anamnesis 30,39,41 is required, as well as the use of clinical 13,16,33 and radiographic 3,5,24,42 methods.

Clinical examination
Clinical examination is performed by means of palpation of the styloid process in the tonsillar fossa. 3,20,24,34t is perceived as a bone spicules that causes pain, 13,35,42 which is relieved by infiltrating lidocaine. 2,16,25,30adiographic examination Various imaging techniques (panoramic, 20,30,33,34 oblique lateral of skull and neck, 4,9,24 anteroposterior skull. 10,13,39.41However, computed axial tomography (CT) 3,7,12,36 and, particularly, computed tomography cone beam is considered the radiological examination of choice 32,37 because it prevents image overlaps and provides low levels of distortion, larger scale contrast, accurate measurement of the length of the styloid process as well as its angulation and anatomical relationship. 2

Nonsurgical Treatment
In cases where the symptoms are of medium intensity, treatment is not recommended, except reassuring the patient. 1,56,17,30 Extraoral or transcervical approach Loeser and Caldwell 2,14,39 described this technique: A proximal incision is made near the sternocleidomastoid muscle to the hyoid bone; parotid fascia is retracted upwards and the carotid sheath along with the sternocleidomastoid muscle are placed on the back.Muscle insertions of the styloid process are dissected and to then remove the portion of the elongated styloid process.14,19,39 Advantages of extraoral procedures include: better view of the work area, 12,14,39,44 exhibition and preservation of vascular and nerve structures, 1,17 broader styloid process resection, 1 minimum generation of edema in the airway 19 and reduced risk of infection. 13,28,30 The sadvantages are: longer surgical time 16,28,31 and paresthesia of the cutaneous nerves; 13,25,28 the resulting external scar of this surgical approach: is cervical, high, small and aesthetically acceptable.1,21,31 Hoffmann 25 and Spalthoff 22 describe the use of a piezoelectric device as a safe and effective way to surgically treat this disease.
Intraoral or transpharyngeal approach Eagle 14,17 described this technique.It consists of a longitudinal incision with blunt dissection performed to locate and remove the styloid process. 14,16,44If the tonsils are present, a tonsillectomy is performed in the same surgical event. 14,28,30espite being an easier, 21,28,31 rapid, 1,16,17,28 and less invasive 12 technique, leaving no visible external scar; 1,13,21 it does not allow adequate visualization of the structures adjacent to the styloid process, 1,21,25 thrombosis of the internal carotid artery, 30 subcutaneous emphysema 17,30 and an increased risk of contaminating cervical spaces. 12,13,21ome authors recommend an intraoral or extraoral endoscopically-assisted approach to solve the disadvantages of this procedure 28,31 because it decreases the amount of bleeding, duration of surgery and hospitalization time, and improves the subjective symptoms of patients, being this an effective and minimally invasive solution to treat Eagle syndrome. 289,31,36,42 The success rate of surgical treatment is 80% to 95.6%.For the nonsurgical treatment there is no real positive long-term effect and after 6 to 12 months, the symptoms reappear. 8,9,12,16,17,18,20,28,30,32,37,41gle syndrome.A narrative review.

CONCLUSION
Eagle syndrome is a complex disorder demanding a thorough knowledge of its signs and symptoms to make a correct diagnosis and provide an appropriate subsequent treatment.
Spread information about this syndrome among health professionals is essential to provide adequate dental care to each patient.