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| ORIGINAL RESEARCH |
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| Year : 2023 | Volume
: 15
| Issue : 2 | Page : 161-167 |
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A study on calcification, variability of the stylo-mandibular ligament, or styloid process with regard to clinical parameters among United Arab Emirates population
Mohamed A Jaber1, Asok Mathew1, Essra M Elameen2
1 Department of Clinical Sciences, College of Dentistry, Centre for Medical and Bio-Allied Health Sciences Research, Ajman, UAE
2 Ajman University, Ajman, UAE
| Date of Submission | 06-Sep-2022 |
| Date of Decision | 09-Feb-2023 |
| Date of Acceptance | 10-Feb-2023 |
| Date of Web Publication | 28-Apr-2023 |
Correspondence Address:
Dr. Asok Mathew
Department of Clinical Sciences, College of Dentistry, Ajman University, P.O. Box 346, Ajman
UAE
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/jioh.jioh_193_22
Aim: The styloid process (SP) is often considered elongated when it is longer than 33 mm. The aim of this study is to assess the prevalence of the elongated styloid process (ESP) among dental patients and the role of dental pathology as a possible etiological factor. Materials and Methods: In total, 2000 consecutive panoramic radiographs of normal people were retrieved from the College of Dentistry, Ajman University, Ajman, UAE, during the 2-year study period. Two calibrated observers evaluated the radiographs to minimize interobserver bias and error. A caliper was used to measure the length (in millimeters of the ESPs directly on the radiographs from the caudal margin of the tympanic plate to the tip of the SP). The ESP was considered present when the measurements were ≥30 mm. Results: This study indicates that the prevalence of the ESP was about 6.9% among the patients who attended the dental school clinic. Of the 2000 panoramic radiographs reviewed, ESP could be measured in 100 cases at least on one side. There was a significant difference between distributions on the left and right sides. The distribution also depends significantly on age and gender. The incidence of related symptoms was higher than that reported in previous studies. Conclusions: The incidence of ESP among dental patients was estimated to be 6.9%, more prevalent among the elderly compared to the young people and bilateral. Odds ratio (OR) in favor of developing ESP in males is 2.378 times more than that in females. In contrast, the OR in favor of having unilateral ESP in males is less than that in females by 0.284. Keywords: Eagle’s Syndrome, ESP (elongated styloid process), Panoramic, Stylohyoid Ligament, Styloid Process
How to cite this article:
Jaber MA, Mathew A, Elameen EM. A study on calcification, variability of the stylo-mandibular ligament, or styloid process with regard to clinical parameters among United Arab Emirates population. J Int Oral Health 2023;15:161-7 |
How to cite this URL:
Jaber MA, Mathew A, Elameen EM. A study on calcification, variability of the stylo-mandibular ligament, or styloid process with regard to clinical parameters among United Arab Emirates population. J Int Oral Health [serial online] 2023 [cited 2023 Jun 1];15:161-7. Available from: https://www.jioh.org/text.asp?2023/15/2/161/375363 |
| Introduction | |  |
There are two types of Eagle’s syndrome seen commonly as reported in the literature. The first type, classic Eagle’s syndrome or stylohyoid syndrome, presents as a sharp pain in the neck or the ear extending to the maxilla, face, and oral cavity. It might appear or triggered with head rotation, chewing, swallowing, tongue protrusion, or yawning. The second type of Eagle’s syndrome is known as stylo-carotid artery syndrome, which occurs when the styloid process (SP) impinges upon the internal or external carotid artery and the nerve plexus accompanying them. It presents as pharyngeal pain, orbital pain, or headache. Compression of the internal carotid artery might present with symptoms of internal carotid vascular insufficiency such as weakness, vision abnormalities, or syncope exacerbated with head movement. There is also the risk of the elongated styloid process (ESP) causing carotid artery dissection, which can lead to transient ischemic attack or stroke.[1]
The SP of the temporal bone extends antero-inferiorly from the medial aspect of the mastoid process. The prevalence of individuals with this anatomical abnormality in the adult population is estimated to be 4% with 0.16%.[2] Langlais et al. reported additional radiographic descriptions for the stylohyoid complex. The terms included were “ram’s horn,” “elongated,” “segmented,” “joint-like,” “pseudo articulated,” “jointed,” “crooked,” and “nodular.”[3] Langlais et al.[3] developed their own classification system for the elongated stylohyoid ligament complex, namely, type I—elongated, type II—pseudo-articulated, and type III—segmented. Langlais et al. proposed a radiographic classification of the elongated and mineralized SP, which included three types of abnormal radiographic appearances and four patterns of calcification/mineralization.[4] There are three types of elongations, namely, elongated (uninterrupted elongation), pseudo-articulated (SP joined to stylohyoid ligament by pseudo-articulation, usually located superior to the inferior border of mandible), and segmented (interrupted segments of mineralized ligament or short or long noncontinuous portion of the SP).
The ESP is classified into four types of calcifications, namely, calcified outline—reminiscent of the radiographic appearance of a long bone with a thin radiopaque cortex and a central radiolucency that constitutes most of the process; partially calcified—thicker radiopaque outline, with almost complete opacification as well as a small and occasionally discontinuous radiolucent core; nodular complex—scalloped outline and may be partially or completely calcified with varying degrees of central radiolucency; and completely calcified—totally radiopaque with no evidence of a radiolucent inner core [Figure 1]. | Figure 1: Prominent elongation of the segmented and pseudo-articulated variant
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Only a few patients develop symptoms from ESP. The symptoms are related to the impingement of the structure on the pharyngeal wall, adjacent nerves, or blood vessels, which include facial pain, pain on swallowing, and discomfort when turning the head or during mandibular function as well as dysphagia, dysphonia, otalgia, vertigo, headache, or a transient syncope. The combination of all these symptoms with the ESP is referred to as the Eagle’s syndrome.[3],[4] ESP is being detected more often with the widespread use of panoramic radiographs in dental practice.[5] ESP and/or the mineralization of the SP is considered present if its length is more than 30 mm (≥30 mm) from the temporal bone on the panoramic radiographs to the apex.[5]
Although the panoramic radiography is the most common projection to detect ESP,[4] other projections, such as posteroanterior of mandible, oblique lateral of mandible, axial and cephalometric radiographs, can also be used to detect. Some limitations of panoramic radiographs include the superimposition of other skeletal structures, which obscures a clear image of the basal part of the complex and the possibility of having linear distortion based on the position of the patient’s head in the orthopantomograph (OPG) machine.[4],[5]
The SP is normally a slender, cylindrical bone that arises from the temporal bone in front of the stylomastoid foramen. The structure includes the stylopharyngeus, the stylohyoid, the styloglossus muscles, and the stylohyoid ligament that reaches the hyoid bone.[5],[6] Embryologically, the SP, the stylohyoid ligament, and the lesser cornu of the hyoid bone that are developed from the second branchial arch are called Reichert’s cartilage. Due to its cartilaginous origin, the ligament has the potential to mineralize.[6] The presence of deeply staining reversal lines along the length of the ESPs was suggestive of multiple microfractures from recurrent traumatic/traction forces and repeated attempts at repair and ossification. It is proposed that mesenchymal structures that are composed of the stylohyoid ligament at its attachment, and tendinous insertions of styloid muscles into the ESPs are stimulated for metaplastic alterations by repetitive stress, traction, or traumatic stimuli from muscular contractions.
This osseous metaplasia of connective cells within them, followed by dystrophic bone deposition, brings about SP thickening and lengthening with associated clinicopathological sequelae.[5],[7],[8] There is a high variability in studies on the prevalence of ESP.[4] O Carrol reported a slightly more gender predilection in women.[7] In contrast, other authors[9],[10],[11] reported equal frequency in both male and female subjects. Some authors reported that the length of SP increased with age,[9],[12],[13] but Carrol[7] could not find a substantiate relationship to this finding. Although the ESP is generally asymptomatic, it can cause in some patients, atypical facial pain. The symptoms, such as facial pain, headache, a sensation of a foreign object lodged in the throat, difficulty in swallowing, have been associated with ESP and are clinically diagnosed as Eagle’s syndrome.[7],[12] The ESP is defined as that longer than 30 mm, and it sometimes compresses the cervical nerves or arteries, leading to symptomatic conditions.[7]
It is sometimes difficult to detect the point of emergence of the process from the temporal bone in the panoramic radiographs because of the superimposed shadow of the mastoid process.[5]
Due to the possibility of ESP being related to atypical facial pain, the present investigation has been designed to determine the prevalence and distribution of ESP in patients visiting Ajman University Dental Clinics during the 2-year study period (2017–2019). Medical management options and surgical management techniques were explored from the literature.
The aim of the present study was to study the prevalence of the ESP in the study population of patients from the treatment clinics of Ajman University, UAE, to study the gender difference and age wise distribution of ESP.
| Materials and Methods | | |
Setting and design
The present retrospective cross-sectional study was conducted in accordance with the Declaration with Helsinki and approved by the Research Ethics committee of College of Dentistry-Ajman University, reference number (D-F-H-19-04-29). All the patients are radiographed after obtaining a consent for the said investigation.
Sampling criteria
A sample size of 2000 panoramic radiographs were retrieved from the College of Dentistry, Ajman University, during the 2-year study period (January 2017–January 2019). The panoramic radiographs were obtained using the same X-ray unit Panoramax AX-4CM (Asahi, Kyoto, Japan).
Methodology
Only those radiographs without errors in patient positioning, exposure, or development were included in the study. All radiographs were observed by two calibrated observers using a standard view box under limited room lighting in order to prevent extraneous light from reaching their retinas.
In order to minimize bias, these radiographs were read twice by the same observer independently on two different occasions. The interval between the two interpretations was 2 weeks. The age and gender of patients were recorded for each radiograph. The length of the ESP was measured from the base of the temporal bone to the tip of the structure, and the occurrence of ESP on one or both sides was documented.
Observational parameters
Any elongation of the SP and/or mineralization of the stylohyoid ligament measuring ≥30 mm in length was considered as ESP. We used a calliper (in millimeter) (Fowler, Ultra-Call Mark III, Switzerland) to measure the ESP.
Statistical analysis
Analysis is done with SPSS software version 23 in which the descriptive analysis was done. Power analysis was found to be 0.95. We applied kappa statistics (k) for interobserver agreement in detecting the ESP and intra-class correlation coefficient (r) in order to verify the interobserver agreement related to the measurements of the ESP. Since the kappa value was indicative of good agreement at both interpretations, the prevalence of ESP was estimated among edentulous patients based on age and gender (relative risk, odds ratio [OR], and chi-square test [χ2]) were applied). The significance was set at P-value of 0.05 with 95% confidence interval.
| Results | | |
The incidence of ESP among dental patients was estimated to be 6.9%, more prevalent among the elderly compared to the young people. Most of the cases were bilateral in occurrence. OR in favor of developing ESP in males is 2.378 times more than that in females. There was an excellent inter-observer agreement in detecting and measuring ESP with k value as 0.85 and r value as 0.52.
Of the 2000 orthopantomographic radiographs examined, only 138 (6.9%) cases (88 males and 50 females) showed an ESP with a significant difference between the two genders (P < 0.000) [Table 1] and [Table 2]. | Table 1: Prevalence of elongated styloid process (ESP) in percentage based on gender
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 | Table 2: Test statistics and relative risk of the elongated styloid process based on gender
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The OR in favor of developing ESP in males is 2.378 times more than that in females. In contrast, the OR of having unilateral ESP in males is less than that in females by 0.284 [Table 2]. The majority of these ESPs were bilateral (73.9%) in their occurrence, especially among male patients (83.0%) compared with female patients (58%) [Table 1].
According to the age-wise distribution, elderly patients (aged 60–80 years) had the highest prevalence (10.7%) in developing ESP compared with younger patients (4.6%) having a high level of significance (P < 0.000) [Table 3]. The interobserver agreement related to the presence of ESP was considered excellent when k = 0.85. The interobserver agreement related to the measurements was considered moderate when r = 0.52. When the two observers performed the measurements, the agreement was low due to the difficulty in distinguishing ESP from the temporal bone. However, when the two observers detected the presence of ESP, the agreement was excellent because the tip of the ESP is easier to detect than the base of the temporal bone. | Table 3: Prevalence of the elongated styloid process in percentage based on age
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| Discussion | | |
The reported studies on the prevalence of ESP among different people showed a different range[4],[14] due to the difficulty in the measurement of ESP. Carrol[7], in a sample of edentulous patients, reported that the prevalence of ESP was 30.0%. In this study, the prevalence of ESP was 6.9%, which agrees with the findings of MacDonald-Jankowski[13], who reported a prevalence rate of 7.8% for the people in London and 8.6% for the people in China. In another study, females were more commonly affected than males (59.8% and 40.2%, respectively), which was not in accordance with our study.[15] We agree with the findings of Ferrario et al.[16] regarding the impossibility of comparing the results from prevalence studies because the discrepancies in the results are based on different radiographic criteria and sample size. When measurements of ESP were performed, we faced some difficulties in distinguishing them from the temporal bone on panoramic radiographs. Hence, two observers were involved before interpreting the presence of ESP and analyzing the measurements in order to eliminate probable disagreement on radiographic interpretation.
The only study that reports ESP considering interobserver agreement, with two examiners using panoramic radiographs, was carried out by Zaki and coworkers.[17] An interobserver agreement was found to be 0.86 on the left side and 0.82 on the right side.
We noticed that the occurrence of ESP was higher in males compared to females, while in some studies[7],[14],[16], it was reported that there is more predilection in females. The majority of ESPs were bilateral (73.9%). Only 26.1% were unilateral, mainly on the right side and that is in agreement with other studies.[14],[16] Majority of ESPs were found to occur bilaterally upon radiological evaluation. The prevalence of ESP either bilaterally or unilaterally may be related to the muscle tension originated from occlusal disarrangements.[18]
Some studies reported that there was a positive relationship between the presence and/or increasing length of ESP with age.[5],[8],[10],[11] Various theories have been proposed to explain the ossification of stylohyoid ligaments, namely, theory of reactive hyperplasia, reactive metaplasia, due to loss of elasticity in the ligament simulating tendinosis.[16] In this study, we noticed that the prevalence of ESP increases significantly with age. However, such observation needs to be interpreted with caution as 67% of our study sample were aged below 60 years.
Our study did not consider the prevalence of ESP to facial pain due to multicausal factors. It was reported that pain in swallowing and throat pain are the main clinical symptoms of ESP, but various other symptoms may also occur depending on the overgrowth and direction of elongation of SP.[18],[19],[20],[21] This study sheds some light on the presence of ESP among some dental patients, and it should be carefully evaluated in geriatric patients with some clinical symptoms. In [Table 4], various researches[22],[23],[24],[25],[26],[27],[28],[29],[30],[31] on ESP were compared for clinical symptoms, diagnostic approaches, and treatment modalities. One of the types, the symptomatic vascular type of eagle’s syndrome can occur with internal carotid artery dissection. This type can be managed with antithrombotic therapy, including antiplatelet drugs, anticoagulants, and tissue plasminogen activator as a first-line treatment. In most of the cases, trans-oral or trans-pharyngeal surgical approach was being carried out to get a faster relief of clinical symptoms. | Table 4: Summary of the different clinical parameters and the treatment approaches used in published research related to elongated styloid process[19],[20],[21],[22],[23],[24],[25],[26],[27],[28],[29]
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Intraoral approach method is more favored as it will minimize the postoperative scar formation and neurological symptoms. The most preferred diagnostic method for the accurate diagnosis is cone beam computed tomography or multislice computed tomography. Cone beam computed tomography allows for the evaluation of length and angulation of the SP.[32] A three-dimensional computed tomography is considered as the gold standard for radiological diagnosis and provides the best supplement to a plain X-ray. Computed tomography angiography is highly recommended in stylo-carotid syndrome to assess blood flow dynamics. The lidocaine infiltration test is confirmatory for symptomatic patients. If a patient’s symptoms get relieved after administering 1 mL of 2% lidocaine to the area surrounding the palpable SP, the test is considered positive and establishes the diagnosis of Eagle’s syndrome.[32] In most of the studies, there is more prevalence in female gender, and there is a clear association of increased prevalence in subjects above 40 years of age. In most of the studies, the prevalence rate is between 4% and 10%, and the majority of the cases caused symptoms ranging from pain in the neck to dysphagia. In most of the cases, the length was in the range of 1.5–4.8 cm.
| Conclusions | | |
Studies are needed in future in order to observe the presence of ESP in symptomatic patients and to identify the role of occlusal derangements in the development of ESP. Based on the clinical, surgical, and radiological evaluation, many treatment options are available for ESP, either intraorally or extraorally, to get the best possible outcomes. The occurrence of ESP was higher in males compared to females, while some studies reported a slightly more predilection in females. Unilateral elongation was more seen in females compared to males, whereas bilateral elongation was more seen in male population. Limitations of the study include the use of conventional radiographs and the variability of the positioning of patient head that can alter the measurement of ESP. In future studies, we do recommend to use large cone beam computed tomography-3D reconstructed volumes by which we can have images with minimal variability from the real anatomical data.
Acknowledgment
None.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interests.
Author contributions
AM—writing and collection of data; MJ—design of the study and data collection; Essra El Ameen—data collection and proof reading.
Ethical policy and institutional review board statement
The above study was given the ethical clearance from the Research ethical committee—Ajman University, UAE. (Reference number (D-F-H-19-04-29).
Patient declaration of consent
Not applicable.
Data availability statement
Data will be available for review upon request
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[Figure 1]
[Table 1], [Table 2], [Table 3], [Table 4]
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