Prevalence of Elongated Styloid Process in 1,000 Panoramic Radiographs of a Brazilian Population

The aim of this study was to evaluate the elongation of the styloid process’ prevalence in a population from the outback of Paraíba state, using digital panoramic radiographs, and to identify differences related to side, gender and age. This was a retrospective observational study in which 1,000 panoramic radiographs of patients over the age of 18 who met the research inclusion criteria were evaluated. The styloid process was measured from its origin, where it leaves the tympanic plate, to its Apex, being considered short when it was less than 20 mm long, normal when it was between 20–30 mm long and elongated when it was longer than 30 mm. A 32% prevalence was found, with a progressive increase related to age, greater length in males and bilateral involvement. It was concluded that around 1/3 of the population studied had an elongated styloid process. Further studies are needed to correlate the elongation of the styloid process and clinical manifestations.

Introduction

The styloid process is a thin, cylindrical and smooth bony projection that arises from the lower surface of the petrous portion of the temporal bone, immediately posterior to the tympanic plate and anterior to the stylomastoid foramen [1], [2]. Its location is clinically significant as it relates to many vital neurovascular structures: the external and internal carotid arteries, as well as the internal jugular vein, the facial, glossopharyngeal, vagus, accessory and hypoglossal nerves. It also provides anchorage for the stylopharyngeus, stylohyoid and styloglossus muscles, as well as the stylohyoid and stylomandibular ligaments [3], [4].

The normal range for the length of the styloid process differs in the scientific literature, which includes different diagnostic methods [5].

The length of the styloid process varies according to the methodology used to measure it. According to Kaufman et al. [6], the normal length of the styloid process varies between 20 and 30 mm, getting classified as elongated when it is longer than 30 mm and short when it is less than 20 mm long. For other authors, the styloid process is within the size considered normal as long as it does not extend below the mandibular foramen; otherwise, it would be considered elongated [7].

Elongation of the styloid process can irritate numerous structures around it, leading to Eagle’s syndrome, which presents through pharyngeal pain, otalgia and an irritating sensation in the throat. However, the presence of an elongated styloid process is generally not a pathognomonic finding to characterize this syndrome since some patients can manifest identical symptoms in the absence of radiographic evidence of elongation [3], [8]. This elongation was first described by the Italian surgeon Pietro Marchetti in 1652 [9]. In 1937, the term stylalgia was created to describe the pain associated with the elongation of the styloid process, whose incidence was 4% of the population [10].

Despite its limitations, in panoramic radiographs, the elongated styloid process has often been seen in dental practice when used to measure the styloid process, such as the superimposition of other bony structures, these structures in the basal part of the craniofacial complex, with the possibility of linear distortion [11]. Although computed tomography and cone beam computed tomography are more suitable for measuring anatomical structures in three dimensions, digital panoramic radiographs are sufficient for diagnosing the abnormal size of the styloid process. Furthermore, digital panoramic radiographs are the main resource for epidemiological studies due to their high distribution, affordability and easy interpretation [12].

A study carried out in 2021 by Nogueira et al. [5], in which the prevalence and characteristics of the elongated styloid process were analyzed through a systematic review, found that the overall prevalence of the elongated styloid process was 30.2%, with a propensity for bilaterality. However, the quality of the studies evaluated was low, demonstrating the need for more homogeneous primary studies with a standardized methodology.

The aim of this study was to assess the prevalence of styloid process elongation in digital panoramic radiographs.

Materials and Methods

To carry out this study, Resolution No. 510/2016 criteria of the National Health Council were obeyed, which deals with ethics in research involving human beings directly or indirectly.

This is a descriptive, retrospective observational study of panoramic radiographs from the spontaneous demand universe of the Dental Radiology Clinic of the University Center of Patos-UNIFIP, related to the elongation of the styloid process in the population of the Paraíba outback, where 1,000 panoramic radiographs taken during the years 2018 to 2022 were selected.

Panoramic radiographs that identified the age and gender of the participants and provided a good view of the styloid process on both sides were included; on the other hand, panoramic radiographs with artefacts lacked information such as the age and gender of the participants and did not encompass the styloid process region were excluded.

The sample consisted of panoramic radiographs of patients over 18 who met the inclusion criteria for the study. The sample was divided into different age groups: Group I: individuals aged between 18 and 25; Group II: individuals aged between 26 and 35; Group III: individuals aged between 36 and 45. Moreover, Group IV consists of individuals aged over 46.

The images were acquired using the ORTHOPHOS XG® device (Sirona Dental Systems, Bernsheim, Germany) with exposure parameters: 70 Kv, 10 mA and 14 seconds. The magnification factor provided by the manufacturer was 1, 1.

Data was collected by one examiner (kappa = 0.673; p < 0.005) on a computer monitor in a darkened environment using the IMAGE J® software (version 1.53e, National Institutes of Health, USA). The styloid process was measured from its origin to its apex when it leaves the tympanic plate. The magnification factor was incorporated. The styloid processes were considered short when they were less than 20 mm long, normal when they were between 20–30 mm long and elongated when they were longer than 30 mm, as previously done by Kaufman et al. in 1970.

The obtained measurements were transcribed onto an evaluation form containing information about the participant’s age and gender and the measurement of the styloid processes on the right and left sides. The quantitative data was tabulated using Microsoft Excel, and descriptive statistics were analyzed using SPSS v20.0 to present the results.

Absolute and percentage frequencies were calculated for the categorical variables and measures of central tendency for the quantitative variables. The student’s t-test was used to determine the variability between the sample measurements in relation to the gender of the participants. The ANOVA test was then used to determine the association between the lengthening of the styloid process and the age and gender of the participants. The significance level was set at p < 0.05.

Results

A total of 1,000 panoramic radiographs taken between 2018 and 2022 were analyzed, with patients aged between 18 and 89 years. The sample consisted of 758 panoramic radiographs. Table I shows a higher percentage of females (n = 524; 69.1%) and ages between 26 and 35 (n = 211; 27.8%).

Table I. Sample’s Distribution According to Gender and Age

Variable	n	%
Gender
Feminine	524	69.1
Masculine	234	30.9
Age
18–25 years old	171	22.6
26–35 years old	211	27.8
36–45 anos years old	190	25.1
Above 46 years old	186	24.5

As shown in Table II, there was no significant difference in the elongation of the styloid process on the right and left sides, with 248 radiographs suggesting an elongated styloid process on the right side (32.7%) and 243 on the left side (32.1%).

Table II. Absolute and Relative Frequencies Relating to Elongation of the Styloid Process

	Right side		Left side
Variable	n	%	n	%
Size of styloid processes
Short	43	5.7	58	7.7
Normal	467	61.6	457	60.3
Elongated	248	32.7	243	32.1

A p-value of less than 0.05 showed a statistically significant difference between the size of the styloid process related to gender for the right (0.001) and left (<0.001) sides, with a larger average size being observed in males (Table III).

Table III. Prevalence of Elongated Styloid Process According to Gender

		Right side			Left side
Variable	n	Average	Standard deviation	p	Average	Standard deviation	p
Gender
Feminine	524	28.61	7.20	0.001	28.07	6.72	<0.001
Masculine	234	30.48	7.59		30.55	7.87

For the age groups, a significant difference was found regarding the elongated styloid process, with a p-value of less than 0.05 for the right (<0.001) and left (0.001) sides, and it was possible to notice an increase in the length of the styloid processes as the individuals got older (Table IV).

Table IV. Prevalence of Elongated Styloid Process According to Age Groups

		Right side			Left side
Variable	n	Average	Standard deviation	p	Average	Standard deviation	p
Age group
18–25	171	29.95	7.58	<0.001	27.74	7.18	0.001
26–35	211	28.03	6.60		27.79	6.06
36–45	190	29.76	7.20		29.84	7.73
>46	186	31.05	7.75		30.01	7.50

Discussion

Elongation of the styloid process is a frequent condition widely investigated based on prevalence studies in panoramic radiographs.

In this study, a prevalence of 32% of elongated styloid processes was found, with both sides frequently affected, as previously mentioned by Nogueira et al. [5] in a systematic review study that evaluated the general prevalence in the literature, whose value was 30.2%, commonly bilateral.

Despite the still uncertain etiology, some theories have been proposed to explain the elongation of the styloid process from the ossification of the stylohyoid and stylomandibular ligaments. Steinman [13] proposed the Reactive Hyperplasia Theory, the Reactive Metaplasia Theory and the Anatomical Variation Theory. The fact is that the elongation of the styloid process may be linked to its origin from the second branchial arch, whose sheath contains high cartilaginous and bone potential, persists as a ligament after the degeneration of the ceratohyal element [8]. and when exposed to some stress factor could produce ossifying hyperplasia [14].

Regarding gender, it was possible to notice a greater average length in male individuals (30 mm) compared to females (28 mm). However, this phenomenon may have occurred due to the bias in the sample, predominantly female (69.1%). Nonetheless, this is controversial, and its prevalence may vary [5].

A progressive increase was found in relation to the age of the participants, where individuals aged between 18–25 years old had an average length of 29.95 mm, while individuals aged >46 years old had an average of 31.05 mm. Although the unknown etiopathogenesis does not allow us to say whether the elongation of the styloid process is directly linked to age, it is assumed that with aging and loss of elastic properties of soft tissues, tendinosis develops between the stylohyoid ligament and the lesser cornu of the hyoid bone [8].

The literature shows variability in prevalence between gender and age in different populations, possibly related to the ethnic factor [5]. But does not necessarily reveal preferences.

Conclusion

It was possible to note that the length of the styloid process increases with age, with a larger average size in males and a propensity for bilaterality.