Morphometric Study of Styloid Process and its Clinical Importance on Eagle’s Syndrome

 

Roghith Kannan¹, M.S. Thenmozhi²

¹Department of Anatomy, Saveetha Dental College, Chennai – 600 077

²HOD, Department of Anatomy, Saveetha Dental College, Chennai – 600 077

 

ABSTRACT:

Background: The styloid process is a slender bony process that projects downwards from the inferior surface of the temporal bone and gives attachment to muscles and ligaments. The aim of the present study is to determine the anatomical morphometry of the styloid process and to study about the elongated styloid process (Eagle’s syndrome).

Materials and Method: An observational study was carried out on 60 dry adult human skulls which were used from the Department of Anatomy, Saveetha Dental College, Chennai, India, to study the morphometry of styloid process and its elongation. Length more than 30mm was considered as an elongated styloid process. A Vernier calliper was used for the measurement.

Result: The average length of the styloid process was 9.3mm (right) and 8.9mm (left) and the average of dry human skulls having an elongated styloid process was 3.3%.

Conclusion:   Anatomical knowledge of the styloid process and elongated styloid process is clinically important because of its close relation to important neurovascular structures. The present study highlights the importance of styloid process in patients with symptoms of Eagle’s Syndrome as it is useful for physicians, radiologists and neurosurgeons.

 

INTRODUCTION:

The styloid process is a slender, elongated, bony projection located anterior to the stylomastoid foramen that extends down from the skull just below the ear. It is occasionally curved. The stylohyoid ligament, stylomandibular ligament, styloglossus muscle, stylohyoid muscle and stylopharyngeus muscle are attached to the styloid process. The distal stylohyal part gives attachment to the muscles and ligaments and the tympanohyal part is ensheathed by tympanic plate. The styloid process is related to important structures such as facial nerve to its base, external carotid artery crossingits tip, parotid gland laterally and the internal jugular vein medially [1].The average length of the styloid process is about 20-25mm. The elongation of this process leads to various clinical symptoms such as neck and cervicofacial pain. A small percentage of the population suffers from a condition called Eagle Syndrome or stylohyoid syndrome which causes an elongation of the styloid process and stylohyoid ligament calcification. According to  Eagle, two types of the syndrome have been described : (A)

 

The  classic  syndrome  which is modulated by pain in the tonsillar fossa, sometimes  associated with  dysphagia and hyper salivation, leading to tonsillectomy and (B) the styloid-carotid syndrome: In this syndrome, the styloid process compresses the carotid arteries and exerts pressure on its sympathetic fibres [4]. Possible symptoms include: Otalgia (ear pain) [2], Dysphagia (difficulty in swallowing) [2], Foreign body sensation in throat [2], Odynophagia (painful swallowing) [3], Pain on chewing [3], Pain when turning the head (towards the affected side) [3], Intense pain when the stylohyoid process is palpated in the wall of the pharynx [2], Pain along the distribution of the carotid artery [3]. Diagnosis is confirmed by radiological findings. Palpation of the styloid process in the tonsillar fossa, which tends to be worsened on bimanual palpation of the styloid through the tonsillar bed. Infiltration with anaesthesia are also used in making the diagnosis. The treatment is primarily surgical; however, some conservative treatments have also been used. The objective of present study is to analyse the morphometric data of styloid process and clinical importance of elongated styloid process (Eagle’s Syndrome).

MATERIALS AND METHOD:

A total of 60 dry human skulls (20 cut skulls and 40 full skulls) with intact styloid process which were used from the Department of Anatomy, Saveetha Dental College, Chennai for this observational study to determine the anatomical variations of the styloid process using a digital Vernier calliper using millimetre scale. The only parameter was to measure the length of the styloid process on the right side and left side and to correlate its variation in relation to Eagle’s syndrome. The data collected was tabulated using Microsoft excel worksheet. Photographs were taken of the elongated styloid process.

 

RESULT:
Number of skulls with the presence of a prominent styloid process (Greater than 5mm) is present in  44 out of 60 dry human skulls (Average: 73.3%)

 

Table 1; Result of study

PARAMETERS	Right side	Left side
Occurrence of styloid process in 60 dry human skulls	37 skulls	38 skulls
Length of the styloid process	Average height: 9.3mm	Average height: 8.9mm
Occurrence of length of styloid process greater than 30mm	2 elongated styloid process (Average: 3.3%)	Nil

 

 

Figure 1: Representation of result in bar graph form

 

Figure 2: The elongated styloid process

 

Therefore the average of skulls with Eagle’s syndrome is 3.3%.

 

DISCUSSION:
Eagle’s syndrome is a rare condition of unknown pathophysiology and etiology. Kaufman et al mentioned that the length of styloid process was less than 3cm [5] and according to Lindeman the length of the styloid process ranges from 2cm to 3cm [6]. Eagle stated that the average length of the styloid process is 2-2.5 cm and 4% of the population had elongated styloid process [4]. The length of the right and left styloid process on the same individual may differ greatly [7].

 

Eagle syndrome is associated with unilateral or bilateral elongated styloid process or stylohyoid ligament calcification. Embryological, the styloid process, stylohyoid ligament, lesser cornua of the hyoid bone and the superior portion of the hyoid body which arises from the second pharyngeal arch and are derived from Reichert’s cartilage. In the present study, length more than 30mm was recorded as an elongated styloid process. The average length of the styloid process on the right side was 9.3mm and on the left side was 8.9.

 

Also the occurrence of the length of the styloid process which was greater than 30 mm was 2 in number out of 60 skulls. Saheib et al mentioned that the incidence of the elongated styloid process is 3.87% [8] and according to Dhanalakshmi et al the incidence was 6.1% [9]. In the present study the incidence of an elongated styloid process was 3.3%. Approximately only 4% of the general population have an elongated styloid process, and of these about 4% give rise to the symptoms of Eagle syndrome and patients with this syndrome tend to be between the age of 30 and 50 years and it is more common in females with a ratio of 1:2 with males. Traumatic fracture of styloid process, compression of adjacent nerves leads to pain on turning the head, discomfort on swallowing and pain on protrusion of the tongue [10]. The elongated styloid process can be treated either conservatively or surgically by excising the elongated styloid process. Depending on the severity of the symptoms and pathogenesis of the syndrome, appropriate treatment is selected.

 

CONCLUSION:

The anatomical knowledge of the styloid process and its elongation is important as the styloid process is closely related to the neuro vascular structures like the facial nerve to its base, external carotid artery crossing its tip, parotid gland laterally and the internal jugular vein medially. The morphometric variations of styloid process is important for physicians, neurosurgeons and dentists to diagnose and treat chronic neck pain and dysphagia. The surgical anatomy of the elongated styloid process is equally important for radiologists and surgeons. In the course of Eagle’s syndrome dissection, aneurysm and pseudo aneurysm of the carotid artery may occur. Further studies are needed to investigate the relationship between the elongated styloid process and the development of such complications [11].

 

ACKNOWLEDGEMENT:

With sincere gratitude, we acknowledge the staff members of Department of Anatomy of Saveetha Dental College for the whole hearted support and permission granted to utilize the resources and to conduct this study.

REFERENCES:

1.     Standring S. Gray’s Anatomy. 40th ed. Elsevier: Churchill Livingstone, Edinburg;2008. P. 599-617.

2.     Kamal, A; Nazir, R; Usman, M; Salam, BU; Sana, F (November 2014). "Eagle syndrome; radiological evaluation and management.". JPMA. The Journal of the Pakistan Medical Association 64 (11): 1315–7. PMID 25831655.

3.     Scully C (21 July 2014). Scully's Medical Problems in Dentistry. Elsevier Health Sciences UK. ISBN 978-0-7020-5963-6.

4.     Eagle WW. Elongated styloid process: report of two cases. Arch Otolaryngol. 1937;25:584-7.

5.     Kaufman SM, Elzay RP, Irish EF. Styloid process variation. Radiologic and clinical study. Arch Oto laryngol. 1970;91:460-3

6.     Lindeman P. The elongated styloid process as a cause of throat discomfort. Four case reports. J Laryngol Otol. 1985;99:505-8

7.     Worth HM. Styloid process. In: Worth HM,eds. Principles and Practice of oral Radiologic interpretation. Chicago: Year Book Medical Publishers; 1963:27.

8.     Saheib HS, Shepur MP, Haseena S. Study of length of styloid process on South Indian adult dry skulls. J Pharm Sci Res 2011;3:1456-9.

9.     Dhanalakshmi V, Santhi B, Manoharan C, Ananthi KS, Kumar RS. Morphometric study of Temporal Styloid Process and Stylohyoid Ligament Calcification. Int J Sci Stud 2015;3(1):130-132.

10.   Eagle WW. Symptomatic elongated styloid process; report of two cases of styloid process-carotid artery syndrome with operation. Arch Otolaryngol. 1949;49:490-503.

11.   Dao A, Karnezis S, Lane JS, Fujitani RM, Saremi F. Eagle syndrome presenting with external carotid artery pseudoaneurysm. Emerg Radiol 2011;18:263-265.

 

 

Accepted on 15.06.2016        © RJPT All right reserved

Research J. Pharm. and Tech 2016; 9(8):1137-1139.