Comparison of the Length of Styloid Process in Panoramic Radiographs to Computed Tomography as the Gold Standard.

Aims: To compare the length of styloid process assessed using computed tomography (CT) and panoramic radiographs (PAN). Materials and
Methods: PAN were taken for 15 patients requiring CT reporting to PMS Dental College or metro scans, after obtaining informed consent and fulfilling all the inclusion and exclusion criteria. CT images were taken in metro scans. The apparent lengths of styloid process were measured in both CT and PAN using software provided with the respective machines. Ethical committee approval was obtained from PMS Dental College, Trivandrum.
Results: The length of left styloid process in CT was observed 20-30 mm in 4 (27%) patients and same in PAN was observed in 5 (33%) patients. Out of 15 patients, abnormal styloid process (length >30 mm) was observed in 11 (73%) patients when measured with CT and 10 (67%) patients in PAN. In CT, the length of the styloid process on the right side was observed between 20 and 30 mm, in 3 (20%) patients. PAN of 2 (13%) patients were found between 20 and 30 mm. On the right side, abnormal styloid process (length >30 mm) was noted in 12 (80%) patients using CT and 13 (87%) patients in PAN. The length of styloid process in the combined sample (both right and left side) was found to be between 20 and 30 mm in 3 (10%) patients and styloid process >30 mm long (in both CT and PAN) was observed in 12 (40%) patients. Conclusions: This study demonstrated positive correlation between CT and panoramic measurements. "P" values were statistically significant on both sides with values of right side (P = 0.01) and left side (P = 0.002), respectively. Hence, PAN, which are routinely taken, cost-effective and involving relatively low radiation dose, may be used as substitute for CT for the purpose of diagnosis of elongated styloid process. However, for precise measurement of the length of styloid process, CT is still the imaging modality of choice. Copyright:

INTRODUCTION

The word styloid process originated from Greek word “stylos” meaning a pillar.[1] The normal length of styloid process is 20–30 mm.[2] Length more than 30 mm is considered as elongation.[3] Patients with elongated styloid process often have pain in throat, dysphagia, otalgia, dizziness, and foreign body sensation that may be classified as Eagle's Syndrome.[3]

Radiographs in which styloid process is seen are panoramic, lateral oblique, anteroposterior view, Towne's view, Submento-vertex radiographs, and computed tomography (CT).[4] The preferred radiographic studies for detecting abnormalities of styloid process are panoramic radiography and computed tomography of the neck and base of skull as they offer bilateral visibility and help in comparison of length of the right and left styloid process in the same radiograph/scan.[345]

At present, CT is considered the gold standard for the estimation of length of styloid process.[6] However, CT involves high doses of radiation and is expensive.[7] Panoramic radiographs (PAN) routinely taken for the diagnosis of dental diseases can display styloid process bilaterally. It is available in most dental institutions and is cost-effective. The radiation dose is comparatively low.

This study was performed to compare the length of styloid process assessed in PAN to CT (gold standard).

MATERIALS AND METHODS

The study subjects comprised 15 patients reported to PMS DENTAL COLLEGE or METRO SCANS for CT studies fulfilling the inclusion and exclusion criteria were sent for panoramic radiograph after getting informed consent. CT images and PAN were taken in METRO SCANS. The apparent lengths of styloid process were measured in both CT and PAN using software provided with the respective machines. SIDEXIS software accompanying the panoramic machine was used for measuring the length.

Inclusion criteria were (i) patient age group of 20–60 years, (ii) patient reporting for head and neck CT as part of investigation willing to undergo panoramic radiograph, (iii) patients already having CT and panoramic radiograph, and (iv) patients reporting with CT images requiring panoramic radiograph. Exclusion criteria were pregnant patients, children, noncooperative and nonwilling patients and patients with history of styloid fracture.

Statistical analysis

The statistical methods such as mean and standard deviation (SD) and Karl–Pearson correlation were employed in the present study. Statistical package for the Social Sciences (SPSS) Version 16, manufactured by International Business Machines Corporation company, USA was used for statistical analysis. Significance was set at 0.01 level.

RESULTS

On assessment of CT, the length of left styloid process in 4 (27%) patients was found between 20 and 30 mm and the same in PAN was observed in 5 (33%) patients. Out of 15 patients, elongated styloid process (>30 mm) was observed in 11 (73%) patients when measured with CT and in 10 (67%) patients when measured with PAN. On the right side, the length of styloid process was observed to be between 20 and 30 mm in 3 (20%) patients in CT, whereas using PAN 2 (13%) patients had length between 20 and 30 mm. The elongated styloid process (>30 mm) was noted in 12 (80%) patients using CT and 13 (87%) using PAN. The length of styloid process in combined sample, both right and left side, in CT and PAN was found between 20 and 30 mm in 3 (10%). Both CT and PAN identified elongated styloid process in 12 (40%) patients. The unilateral elongation was noted only in 1 (3%) patient when measured with CT, whereas with PAN unilateral elongation noted with 3 (10%) patients [Table 1]. Unilateral elongation noted in PAN of 3 patients also showed that right side styloid process was longer than left side. Bilateral elongation was noted in 11 (37%) patients out of 15 patients when examined using CT and 10 (33%) patients out of 15 patients in PAN. Normal length on both sides was observed in 3 (10%) patients using CT and 2 (7%) patients in PAN [Table 1].

Table 1

Length of styloid process in computed tomography and panoramic radiographs

Patient numbers (n=15)	Length in CT (mm)		Length in PAN (mm)
	Right side	Left side	Right side	Left side
1	25.2	25.7	21.1	27.4
2	34.4	34.3	39.3	33.9
3	22.4	26.5	25.2	29.5
4	31.2	32.4	54	55.8
5	34.3	32	49.5	45.4
6	46.1	37.9	55.3	55.5
7	56.8	54.6	61.2	57.7
8	36.4	31.6	43.7	37.5
9	37.2	35.1	40.2	39.7
10	32.5	35.3	30.6	27
11	33.2	31.9	32.7	31.7
12	30.8	27.6	30.6	22.7
13	40.4	46.2	48	50.8
14	34.7	33	37.4	35.7
15	26.1	25	33.3	25.4

CT: Computed tomography, PAN: Panoramic radiographs

Computed Tomography (Gold standard) and Panoramic Radiography were used to determine the length of the styloid process on the right side. When these were tabulated, it was discovered that the average length of the styloid process on the right side in the Computed Tomography group was 34.8 mm, with a standard deviation of 8.5 mm. In panoramic group, mean length and SD was 38.4 mm and 11.9 mm, respectively. The median length in CT group observed was 32.4 mm and that in panoramic group was 35.7 mm [Table 2].

Table 2

Descriptive statistics for length of styloid process for left side

Descriptive statistics	CT (length in mm)	Panoramic (length in mm)
Mean	33.9	38.4
SD	7.8	11.9
Median	32.4	35.7
Minimum	25.0	22.7
Maximum	54.6	57.7

CT: Computed tomography, SD: Standard deviation

The length of styloid process on right side was measured in CT (gold standard) and PAN when tabulated showed, mean length of 34.8 mm with SD 8.5 mm in the CT group. In panoramic group, mean length and SD was 40.1 mm and 11.7 mm. The median length in CT group observed was 34.3 mm and that in PAN group was 39.3 mm. The maximum and minimum length of styloid process noted in CT group were 56.8 mm and 22.4 mm and that in panoramic group was 61.2 mm and 21.1 mm [Table 3].

Table 3

Descriptive statistics for length of styloid process for right side

Descriptive statistics	CT (Length in mm)	Panoramic (Length in mm)
Mean	34.8	40.1
SD	8.5	11.7
Median	34.3	39.3
Minimum	22.4	21.1
Maximum	56.8	61.2

CT: Computed tomography, SD: Standard deviation

The correlation coefficient was r = 0.73, which denoted moderate positive correlation among measurements observed in CT and PAN on the left side. On the right side, correlation coefficient was r = 0.814, which shows strong positive correlation in CT and panoramic measurements. When the lengths of the styloid processes on the right side were compared to the lengths of the styloid processes on the left side, a moderate positive correlation of r = 0.773 was found. When the length of the styloid process was compared between CT and Panoramic radiography, the p on the left side was significant (p = 0.002), while the p on the right side and of the whole sample was highly significant (p=0.000). whereas that in the right side and the whole sample were highly significant (p = 0.000) [Table 4].

Table 4

Correlation of length of styloid process between computed tomography and panoramic measurements

Side	r	P
Left	0.73**	0.002
Right	0.814**	0.000
Total	0.773**	0.000

DISCUSSION

Even though the normal length of styloid process is considered to be between 20 and 30 mm in adults, several authors are of opinion that the length could vary from 15.2 mm to 47.7 mm.[8] Sokler et al. have classified the styloid process according to length into short (<20 mm), normal (21–30 mm), and elongated (>30 mm)[9] Hence, in our study, length of the styloid process more than 30 mm was considered as elongation. Elongated styloid process may often lead to clinical symptoms such as neck and cervicofacial pain that characterize Eagle's Syndrome.[101112] Elongated styloid process can present unilaterally or bilaterally.[13]

In a cross-sectional study by Leila et al.,[14] the authors identified elongated styloid process in 153 out of 400 patients (38.25%). In our study on 15 patients, elongated styloid process was observed in 86.6% of patients (13/15 patients), a figure much more than the available studies. This probably can be attributed to the small sample size and the fact that both CT and panoramic radiograph were taken mostly in symptomatic individuals who had reported for either of the two imaging modalities, but willing for an exposure of the other.

Unilateral elongation of the styloid process in our study was noticed in 3% of our patients (1/15 patients) using CT, whereas using PAN, 10% of patients were identified with unilateral elongation. On assessment with CT, 27.7% unilateral elongated styloid process assessed was noticed in a study involving 530 patients by Apaydin et al.[15] The incidence of unilateral elongation of styloid process noted in PAN group of our study was very similar to that observed by Gokce et al.[16] and More et al.[17] In the CT group, our study showed very low incidence in comparison to other studies, probably due to the small sample size.

Bilateral elongation of the styloid process in our study was noticed in 37% of our patients (11/15 patients) using CT, whereas using PAN, 33% of patients were identified with bilateral elongation. Bilateral elongation of styloid process assessed using PAN in literature ranged from 3.7% to 84.7%.[18192021]

Correlation of the length of the styloid process between CT and panoramic measurements in our study showed a strong positive correlation on the right side (r = 0.814) than on the left side (r = 0.73). The correlation was moderate (r = 0.773) when both side measurements were considered together. Our results are in agreement with that of Wang et al. who reported a statistically significant positive correlation between panoramic and three-dimensional CT (r = 0.982).[22]

CONCLUSIONS

In the present study, it was evident that the length of styloid process obtained in panoramic radiograph was not comparable with CT measurements. Moderate positive correlation between CT and panoramic measurements was noticed on the left side and combined sample. The strong positive correlation was observed on right side compared to the left side. It may be concluded that a PAN may be sufficient to measure the length of the styloid process for making a diagnosis of diseases caused by elongated styloid process. However, for precise measurement of the styloid process for treatment/surgical purpose, CT is the imaging modality of choice. Since the sample size was small in our study, which was a limitation, further studies are recommended to evaluate and compare the two imaging modalities.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.