Styloid Process; Correlation Between Symptoms, Palpability and Measurements on Three Dimensional Computed Tomography

Abstract

Styloid process is a long and slender osseous projection protruding downward, forward and slightly medially from the temporal bone and serves as an anchor point for various muscles associated with the tongue and the larynx. The aim of the present study was to record the length and the angle of Styloid process on three dimensional computed tomography in patients with unilateral symptomatic and palpable styloid process and compare the length and the angle of styloid process of symptomatic side to asymptomatic side on three dimensional computed tomography. 3D-CT face reconstruction were perfomed in all 35 patients (17 females, 18 males of age range 25–69 years). The length of the styloid process and its angulation (transverse and sagittal angles) were measured by means of three dimensional and multiplanar reconstruction images. The length of styloid process on symptomatic side had a mean of 33.61 ± 5.08 mm while on asymptomatic side mean was 31.11 ± 5.02 mm. The mean transverse angle on symptomatic sides had a mean of 72.37° ± 4.48° while on asymptomatic side mean was 74.17° ± 4.48°. The mean sagittal angle seen on symptomatic side was 88.11° ± 5.21° while on asymptomatic side was 87.88° ± 5.03°. Symptomatic side has a longer styloid. Length of the styloid process has a statistical correlation with the symptoms and symptomatic side has a longer styloid. Though there was a difference in transverse and sagittal angulation in symptomatic versus asymptomatic side; but it was not statistically significant. On examination of the opposite asymptomatic side, 5 patients had a palpable styloid process therefore we infer that long styloid process may not always be associated with symptoms. Patients with cervicofacial pain should be evaluated for Eagle syndrome by palpation of styloid process in the tonsillar fossa and further by three dimensional computed tomography (3D-CT). 3D CT is an effective tool in evaluating patients with cervicofacial pain and making a diagnosis of Eagle’s syndrome. Therefore, 3D CT should be performed while evaluating patients with these symptoms.

Introduction

Styloid process (SP) is a long and pointed bony process protruding downward, forward and slightly medially from the temporal bone [1]. It originates as a part of Reichert's cartilage forming from the second pharyngeal arch and undergoes endochondral ossification in the late stages of pregnancy that continues over to the first decade of life [2]. SP arises from the temporal bone immediately in relation to the anteromedial aspect of the stylomastoid foramen. There are three muscles namely styloglossus, stylopharyngeus and stylohyoid which are attached to the SP from the tongue, pharynx and hyoid bone, respectively. There are two ligaments named stylohyoid which arises from the tip of the SP to the lesser cornua of the hyoid bone and and stylomandibular which arises from the angle and posterior border of angle of the mandible between masseter and medial pterygoid respectively [3]. These ligaments help to regulate the movements of the mandible, the hyoid bone, tongue and the pharynx. Many critical anatomic structures such as the internal jugular vein, internal carotid artery and glossopharyngeal nerve (CN IX), vagus nerve (CN X) and accessory nerve (CN XI) lie on its medial side, while the occipital artery and hypoglossal nerve (CN XII) run along its lateral side⁴.

The normal length of SP is 20–30 mm and it is considered to be elongated if it exceeds a length of 30 mm [4]. The elongated SP is considered to be the result of ossification of the stylohyoid ligament producing cluster of symptoms and gives rise to “Eagle’s syndrome” or “Stylohyoid syndrome” [2]. There are variety of suggested hypothesis regarding the cause of elongation of SP that include theories of reactive hyperplasia, reactive metaplasia, anatomic variance, aging developmental anomaly, degenerative process and genetic hypothesis. The congenital theory, which is the most accepted one asserts that mechanical stresses may sometimes lead to stretching of the Reichert’s cartilage and the ossification of SP. Despite many suggested hypothesis, the exact etiology still remains unknown [5].

Styloid process shows a variance between individuals in length, angulations and other morphological features. Most of the times, the anatomical variations are asymptomatic, but sometimes it may cause series of symptoms such as foreign body sensation in the throat, pain on neck movement, facial pain, earache, headache, vertigo, dysphagia, odynophagia, tinnitus and trismus resulting in Eagle syndrome [6]. It can also cause dysphonia, carotidynia and reduced mandibular opening and may be misinterpreted as temporomandibular disorders, tumors of tongue base, trigeminal and glossopharyngeal neuralgia, migraine, unerupted third molars, myofascial pain, hypersalivation and even dysgeusia many a times mandating to be included under the differential diagnosis [7]. Hence, it is an important diagnosis to be taken into consideration to evaluate, diagnose and treat the condition with more expertise.

The diagnosis of the syndrome depends on clinical presentation including duration of the symptom, location and nature of pain, digital palpation of elongated styloid process, radiological investigation utilizing X-ray (Orthopantomogram) and CT scans. Although conventional radiographs provide a rough idea of the anatomy, it is difficult to get to the actual diagnosis due to superimposed anatomical structures. Nowadays newer modalities like Multi-slice CT with 3D reconstruction is the best diagnostic method for Eagle syndrome. 3D CT is an extremely valuable imaging tool in head and neck pathologies because of its ability to accurately image the anatomy and thus it is beneficial for determining appropriate surgical strategy and allow the physician to better explain the condition and treatment options to patients.

Treatment of Eagle syndrome includes conservative treatment or surgery. Treatment method depends on the severity and duration of patient's symptoms. The conservative treatment of ES includes reassurance, analgesics medication, and steroid injection. Surgical treatment can be conducted by shortening or complete excision of the elongated styloid process through intraoral or external approach.

Material and Methods

This prospective study was conducted in the Department of Otorhinolaryngology & Head and Neck Surgery and the Department of Radiodiagnosis at a tertiary care centre in India from November 2018 to May 2020 after the approval by the Research/Ethics Committee. These patients were clinically diagnosed as unilateral cervicofacial pain with palpable styloid process attending outpatient department were part of the study group and the opposite asymptomatic side in these patients formed the control group.

Thus, 35 patients clinically presenting with symptoms of unilateral neck pain and having clinically palpable unilateral styloid process in tonsillar fossa on digital palpation were included in the study. All these patients underwent complete ENT evaluation and 3D CT reconstruction after obtaining a written informed consent.

Patients clinically presenting with symptoms of dysphagia, odynophagia, referred otalgia, recurrent throat pain, dental caries, peritonsillar abscess, patients with cervical lymphadenopathy, post operated post radiotherapy patients of carcinoma head and neck region, growth oropharynx/larynx, cases of cervical spondylosis were excluded from the study.

All included patients were examined and styloid process was palpated digitally. The patients then underwent 3D CT reconstruction face in the Department of Radiodiagnosis with multiplanar reconstruction (MPR) as well as 3D VRT (Volume rendering technique) images in the Department of Radiodiagnosis. The measurements were taken from Multiplanar reformatted data sets on CT workstation (SIEMENS). The following parameter were assessed -

• Length of the styloid process in the transverse and sagittal planes.

• Angle of the styloid process in transverse plane (in coronal images) and in sagittal planes.

The length was defined between the attachment point of the SP to the temporal bone and the tip of the SP. Angulation of the SP was defined in the coronal and sagittal planes, respectively. The angle between the line connecting the base of the SPs and the long axis of the SP was defined as the transverse angle and the angle between the long axis of the SP and McRae’s line (i.e. a line connecting the anterior and posterior lips of foramen magnum) on lateral aspect was defined as the sagittal angle. The data was collected, tabulated and analyzed statistically.

Statistical analysis was performed with the statistical package for the social science system version SPSS 17.0. Continuous variables were presented as mean ± SD, and categorical variables were presented as absolute numbers and percentage. The comparison of normally distributed continuous variables between the groups was performed using Student’s t test. Nominal categorical data between the groups were compared using Chi-squared test. P < 0.05 was considered statistically significant.

Observation and Results

There were 28.6% patients each in 31–40 years and > 50 year age group. The youngest patient was 25 years of age and oldest was 69 years old. Mean age came out to be 44.4 ± 12.18.

Ratio of males and females in the study group was almost equal.

Majority of the patients 25 (71.4%) presented with symptoms ranging from 6 to 12 months and 65.7% patient had right sided cervicofacial pain (Tables 1, 2).

Table 1.

Sex distribution compared to the side of cervicofacial pain

Sex	Cervicofacial pain				p value
	Left		Right
	Frequency	%	Frequency	%
Females	7	58.3%	10	43.5%	0.404
Males	5	41.7%	13	56.5%
Total	12	100%	23	100%

Comparison of cervicofacial pain in relation to sex showed that right side neck pain was more common in both sexes but without any statistical significance (Table 1)

Table 2.

Comparison of length and angle of styloid process in symptomatic and asymptomatic side

	Symptomatic side (n = 35)	Asymptomatic side (n = 35)	p value
	Mean ± SD	Mean ± SD
Length	33.61 ± 5.08 mm	31.11 ± 5.02 mm	0.042
Transverse angle	72.37° ± 4.48°	74.17° ± 4.48°	0.097
Sagittal angle	88.11° ± 5.21°	87.88° ± 5.03°	0.853

The mean length of styloid process in symptomatic side was 33.61 ± 5.08 mm and in asymptomatic side was 31.11 ± 5.02 mm and this difference was statistically significant. The transverse angle on the symptomatic side was slightly less than that of asymptomatic side (72.37° Vs. 74.17°). However, the sagittal angle was slightly more on the symptomatic side as compared to asymptomatic side (88.11° Vs. 87.88°). (Table 2). This difference in angles was not statistically significant

Discussion

According to literature there are different studies about elongated styloid process (SP) and the incidence of elongated styloid process is around 4–7% and only 4% of patients with elongation of styloid show the symptoms [8]. However we recruited only unilaterally symptomatic patients with palpable styloid process in our study.

Keur et al. found that the prevalence of elongated styloid processes was equal in men and women [9] which is almost similar to our study. However, several studies quoted a female preponderance [10, 11]. According to More et al. males show higher predilection for an elongated styloid process [12]. However, in our study there was no significant variation in the length of styloid process in males and females. We observed a bimodal presentation of age in our study where the most commonly affected age was in between 30 and 40 years and more than 50 years whereas Montelbetti et al. reported that the most commonly affected age group was more than 50 years [13] but other studies like Onbas et al. and Palesy et al. reported it to be more than 30 years [14, 15]

In our study, out of 35 patients presenting with unilateral cervicofacial pain and a palpable styloid process, 5 patients had palpable styloid process on the opposite asymptomatic side also. Murthy et al. and Zohar et al. mentioned that bilateral elongation of SP is quite common but the patient may not always present with bilateral symptoms. It implies that elongation of styloid process is not always associated with symptoms [16, 17].

Majority of the studies in the available literature have been performed on cadavers or dry skull and conventional method for measurement was used. In a study done by Kaufman et al. out of 80 cadavers, the length of the styloid process was found to range from 15 to 47 mm [18]. However in our study, the length of styloid process was found in the range of 24 mm and 43.8 mm. This variation in the range may be due to the employment of different methods for measurement of the length of styloid process i.e. osteometric methods, panoramic radiographs and CT. In our study, the longest SP calculated was 43.8 mm whereas according to Balcioglu, mean length of the styloid process was 40.0 ± 4.72 mm [19]. Kaufman et al. in a study of 848 patients found that longest SP was 62 mm [18]. The normal SP measures between 25 and 30 mm according to Eagle’s criteria although his method of measurement was not described, but his examples showed lateral radiographs of the skull¹. In a CT study, Onbas et al. estimated the length of SP on both sides to vary between 0 and 62 mm (mean 26.8 mm) [14]; 2.51 to 6.11 cm (mean: 3.51 cm) according to Ceylan et al. [20] and between 1.58 and 5.48 cm (mean 2.83 cm) acoording to Basekim et al. [21] whereas in our study we found out that SP length varied between 24 and 43.8 mm. We did not came across any study which performed anthropological measurements and observed its racial variation.

In our study, the mean length of styloid process on symptomatic side was 33.61 mm while on asymptomatic side it was 31.11 mm and this difference was statistically significant. Azin S et al. reported the mean length of styloid process was 25.3 mm [22]; Onbas et al. in their study evaluated 283 patients by MDCT and observed that the mean length of SP was 26.8 mm [14]. Hence we conclude that the length of the styloid process is an important parameter for causing symptoms.

In our study, the mean transverse angle was 72.37° on symptomatic side and 74.17° on asymptomatic side whereas sagittal angle on symptomatic side was 88.11° and 87.88° on asymptomatic side. However the difference between angulation on both sides was not statistically significant. Onbas et al. [14] evaluated SP by MDCT and they observed that the mean transverse angle was 72.7° and the mean sagittal angle was 93.5°. Thus according to our study the length of styloid process was mainly responsible for the symptoms and angulation of styloid process had lesser impact on the symptomatology.

The main limitation in our study is the small sample size and a restrictive inclusion criteria as we had recruited only unilaterally symptomatic patients with palpable styloid process. However it also resulted in better correlation of symptoms to both length and angle of styloid process measured by 3D-CT (Figs. 1, 2, 3).

Fig. 1.

3D-CT showing the styloid processes and the measurement of length

Fig. 2.

3D CT showing the styloid processes and the measurement of transverse angle

Fig. 3.

3D CT showing the styloid processes and the measurement of sagittal angle

Conclusion

On evaluation of styloid process using 3D CT we concluded that the patients with unilateral cervicofacial pain have a longer styloid process in comparison to the asymptomatic side. Though there was a difference in transverse and sagittal angulation in symptomatic versus asymptomatic side; but it was not statistically significant. On examination of the opposite asymptomatic side, 5 patients had a palpable styloid process therefore we infer that long styloid process may not always be associated with symptoms. We also conclude that 3D CT is an effective tool in evaluating the styloid process in patients with cervicofacial pain.

Declarations

Conflict of interest

Authors declare that they have no conflicts of interest.

Ethical Approval

This article does not contain any studies which experiments with human participants or animals and all institutional and international ethical standards have been followed.

Informed Consent

Informed consent was obtained from all individuals participants included in the study.