Jaworek, Joanna Karolina

Skrzat, Janusz

Walocha, Jerzy

Zamojska, Izabela

Zawiliński, Jarosław

Folia Morphologica

English

Jagiellonian Univeristy Repository

Folia Morphol. Vol. 66, No. 3, pp. 203–206Copyright © 2007 Via MedicaISSN 0015–5659www.fm.viamedica.plC A S E   R E P O R T203Address for correspondence: Dr Janusz Skrzat, Department of Anatomy, Collegium Medicum, Jagiellonian University, Kopernika 12,31–034 Kraków, Poland, tel: +48 12 422 95 11, fax: +48 22 422 95 11, e-mail: jskrzat@poczta.onet.plBilateral ossification of the stylohyoidligamentJ. Skrzat, I. Mróz, J. Walocha, J. Zawiliński, J.K. JaworekDepartment of Anatomy, Collegium Medicum, Jagiellonian University, Cracow, Poland[Received 15 February 2007; Revised 22 June 2007; Accepted 27 June 2007]This paper presents the case of an adult male skull with bilateral ossification of thestylohyoid complex. The total length of the stylohyoid complex amounts to62 mm on the left side and 65 mm on the right side. Visual inspection of thestylohyoid revealed the presence of callosities that are located on both stylohyoidcomplexes at nearly the same level. These sites are regarded as the ossified attach-ments of the stylohyoid ligaments to the corresponding styloid processes. Theskull studied is an example of extreme development of the stylohyoid complex,which could cause severe pain and a restriction of head and neck movement.Key words: styloid process, hyoid bone, cranial ligaments, stylohyoidcomplexINTRODUCTIONThe stylohyoid ligament is a fibrous cord stretchedbetween the tip of the styloid process of the tempo-ral bone and the lesser horn of the hyoid bone. Thisprocess forms the background for the attachment ofnumerous muscles and ligaments that are connectedto the throat and tongue. The styloid process togeth-er with the stylohyoid ligament is referred as the sty-lohyoid complex. The entire complex can be dividedinto several segments, including the tympanohyal,stylohyal, ceratohyal and hypohyal segments [9].Many important anatomical structures are inclose proximity to the styloid process and the stylo-hyoid ligament. It is therefore worth studying thevariability of these structures and analysing the pos-sible effects of an ossified stylohyoid complex. Justposterior to the process lies the stylomastoid fora-men, through which the facial nerve exits to runanteriorly and medially to the styloid process. Theinternal carotid artery, the internal jugular vein andthe accessory and vagus nerves lie medially. The ex-ternal carotid artery runs laterally to the stylohyoidligament. The glossopharyngeal nerve exists in closeproximity under the styloid process, stylohyoid mus-cle and the stylopharyngeal muscle. The elongatedstyloid process and the ossified stylohyoid ligamentcan compress some of these structures, leading tomild or severe clinical syndromes, such as sore throat,dysphagia, dysphasia, dysphoria of the throat, otal-gia, the sensation of a foreign body in the throat,facial pain radiating to the ear or along the mandi-ble and head and neck pain [3, 5, 11, 13].The aim of this study is to describe the morpho-logical appearance of the bilateral ossification of thestylohyoid ligament found in a dry human skull.MATERIAL AND METHODSA skull with bilateral ossified stylohyoid ligamentsis housed in the Department of Anatomy of the Col-legium Medicum of the Jagiellonian University. Un-fortunately the exact dating and origin of the skull isunknown. Its morphological appearance suggests thatit belongs to a recent population. The skull is wellpreserved, with no noticeable deformities. The markedmuscular attachments, strongly developed temporallines, prominent supercilliary ridges, well-developedexternal occipital protuberance and the shape of themandible are all indicative of a male skull (Fig. 1).204Folia Morphol., 2007, Vol. 66, No. 3An anatomical study was performed on the ossi-fied stylohyoid ligaments on both sides of the skull.The length of the osseous complex (the stylohyoidprocess plus the ossified part of the stylohyoid liga-ment) was measured using a digital sliding calliper.RESULTSVisual inspection of the right and left stylohyoid com-plex revealed complete ossification of the styloid pro-cess and stylohyoid ligament. The ossified parts of thestylohyoid ligaments are clearly visible (Fig. 2, 3). Never-theless, it is difficult to determine the exact border be-Figure 1. Anterior view of the skull with bilateral ossification ofthe stylohyoid ligaments (the mandible was removed).Figure 2. Posterior view of the ossified stylohyoid ligaments(indicated by arrows); ma — mandible, mp — mastoid process.Figure 3. Lateral view of the ossified stylohyoid ligaments (indi-cated by arrows).Figure 4. Close-up view of the callosities and apparent ossifiedattachment (indicated by arrow) of the right and left stylohyoidligament to the styloid process; stp — styloid process, shl —ossified stylohyoid ligament.tween the top of the styloid processes and the begin-ning of the stylohyoid ligaments on both sides. Closeobservation revealed a bulge of bony mass in the mid-dle parts of the ossified complexes. Its presence mayindicate the place of attachment of the ligament to thestyloid process (Fig. 4). This place was therefore regard-ed as the end of the styloid process and served asa landmark for measuring the distance to the cranialbase. This distance was treated as equivalent to thelength of the styloid process and measured 28 mm onthe left side and 31 mm on the right side. The remain-ing part of the left ossified stylohyoid complex, namelythe ligament, measured 34 mm, while the right ossifiedstylohyoid ligament was 30 mm in length. Thus the to-tal length of the stylohyoid complex amounts to 62 mmon the left side and 65 mm on the right side.The callosities are located on both stylohyoidcomplexes at nearly the same level and at a distance205J. Skrzat et al., Ossified stylohyoid ligamentof 31–35 mm from the basicranium. From theseplaces both osseous complexes bend medially.The distance between the bases of the right andleft styloid processes was 91 mm while the dis-tance between the ends of the ossified stylohy-oid ligaments decreased to 51 mm. This differ-ence between the origins and ends of the twostylohyoid complexes expresses a strong mutual-ly convergent course towards the mid-sagittalplane.DISCUSSIONThe normal length of the styloid process usuallyvaries between 25.0 and 30.0 mm [2]. However,Moffat et al. [14] regard the normal range of thelength of the styloid process as between 15.2 mmand 47.7 mm. In human skulls elongation of thestyloid process can occur. This condition is regardedas an anatomical anomaly. A styloid process is consid-ered to be elongated when it is longer than 30.0 mm[8, 10, 18, 20]. However, some researchers regardthe styloid process as elongated if its length exceeds40 mm [7, 15]. This anomaly appears in adults withvarying frequency, ranging from 2% to 30% [21].The styloid process can be elongated bilaterally orunilaterally. According to Scaf et al. [18] unilateralelongation of the styloid process is the more fre-quent unilateral elongation of the styloid process(90.5%). Ossification of the stylohyoid ligament oc-curs with differing frequency and may be as lowas 2–4% or as high as 84.4% but does not causeany symptoms [1, 4]. The incidence of ossificationof the stylohyoid ligament or stylohyoid complex(including the styloid process) varies in the pub-lished literature and depends on different crite-ria in radiographic evaluation and patient selec-tion [12].The skull investigated is a case of extensive bi-lateral ossification of the stylohyoid ligament,which is firmly fused with the styloid process, form-ing a long bony trabecula. It is difficult to deter-mine a clear border between the styloid processand part of the ossified ligament. If we accept thatthe present callosities are the sites of ossified at-tachments of the stylohyoid ligament to the tip ofthe styloid process, then its length remains withinthe normal anatomical range. Because the entireosseous stylohyoid complex is unusually long (morethan 50 mm on both sides of the skull), there is nodoubt that these structures have resulted from ab-normal ossification and are not merely an elonga-tion of the styloid processes. This must have takenplace during cranial development and could havecontinued during postnatal life.The stylohyoid ligament derives from the secondbranchial arch. The cartilaginous element of the sec-ond arch (Reichert’s cartilage) extends from the oticcapsule to the midline in the each side. Thereafterthe cartilage gives rise to the styloid process, stylo-hyoid ligament, the lesser cornu and probably thecranial rim of the body of the hyoid bone. Duringfoetal development Reichert’s cartilage links the sty-loid process to the hyoid bone. Probably owing toossification of the styloid process the ligament mayprolong the ossification, resulting in very long sty-loid processes. In adults the stylohyoid ligament mayretain some of its embryonic cartilage and thus havethe potential to become partially or completely ossi-fied [16].The elongated styloid process, which resultsfrom normal biological variation, is a slendersmooth pointed process projecting downwardand forward from the inferior surface of the tem-poral bone. When ossification of the stylohyoidligament propagates along its course there mayappear different callosities and the entire com-plex resembles an irregular bony trabecula, whichis usually bent medially. In the case studieda swelling and narrowing on the ossified stylohy-oid complexes of both sides of the skull may beperceived.Abnormal length and anatomy of the stylohy-oid complex may cause various clinical symptoms.One of these is Eagle’s syndrome, in which the elon-gated styloid process or ossified stylohyoid ligamentis a source of pain [3, 5, 13, 17, 18]. Eagle’s syn-drome is not frequently suspected in clinical prac-tice, and only in a small percentage of the popula-tion does an ossified stylohyoid ligament manifestthe clinical symptoms. The syndrome exists at about28% of the population and is most commonly seenafter the age of 30; there is no significant sex pre-dilection [3, 6, 10, 19].The following are also symptoms associated withossified stylohyoid complex: a foreign-body sensa-tion in the throat, difficulty in swallowing, dys-phagia, headache, otalgia, pain on rotation of theneck, pain on extension of the tongue, a change invoice, facial pain, vertigo, syncope and a sensationof hypersalivation [3, 5, 11, 18].The case studied is a good example of extremedevelopment of the stylohyoid complex, which couldcause severe pain and significantly restricted headand neck movement.206Folia Morphol., 2007, Vol. 66, No. 3REFERENCES1. Camarda AJ, Deschamps C, Forest D (1989) Stylohyoidchain ossification: a discussion of etiology. Oral SurgOral Med Oral Pathol, 67: 512–520.2. Eagle WW (1962) The symptoms, diagnosis and treatmentof the elongated styloid process. Am Surg, 28: 1–5.3. Feldman V (2003) Eagle’s syndrome: a case of symp-tomatic calcification of the stylohyoid ligaments. J CanChiropr Assoc, 47: 21–27.4. Ferrario VF, Sigurta D, Daddona A, Dalloca L, Miani A,Tafuro F, Sforza C (1990) Calcification of the stylohy-oid ligament: incidence and morphoquantitative eval-uations. Oral Surg Oral Med Oral Pathol, 69: 524–529.5. Godden DRP, Adam S, Woodwards RTM (1999)Eagle’s syndrome: an unusual cause of a clicking jaw.Br Dent J, 186: 489–490.6. Gossman JR, Tarsitano JJ (1977) The styloid-stylohy-oid syndrome. J Oral Surg, 35: 555–560.7. Jung T, Tschernitschek H, Hippen H, Schneider B,Borchers L (2004) Elongated styloid process: when is itreally elongated? Dentomaxillofac Radiol, 33: 119–124.8. Kaufman SM, Elzay RP, Irish EF (1970) Styloid processvariation: radiologic and clinical study. Arch Otolaryn-gol, 91: 460–463.9. Keats TE (1992) An atlas of normal roentgen variantsthat may simulate disease. 5th ed. Mosby, St. Louis.10. Keur JJ, Campbell JP, McCarthy JF, Ralph WJ (1986)The clinical significance of the elongated styloid pro-cess. Oral Surg Oral Med Oral Pathol, 61: 399–404.11. Kirchhoff G, Kirchhoff C, Buhmann S, Lenz K, Vogel T,Kirchhoff RM (2006) A rare differential diagnosis tooccupational neck pain bilateral stylohyoid syndrome.J Occup Med Toxicol, 1: 14–19.12. Krennmair G, Piehslinger E (2003) Variants of ossifica-tion in the stylohyoid chain. Cranio, 21: 31–37.13. Miller DB (1997) Eagle’s syndrome and the traumapatient. Funct Orthod, 14: 30–35.14. Moffat DA, Ramsden RT, Shaw HJ. The styloid processsyndrome: aetiological factors and surgical manage-ment. J Laryngol Otol, 91: 279–294.15. Monsour PA, Young WG (1986) Variability of the styloidprocess and stylohyoid ligament in panoramic radio-graphs. Oral Surg Oral Med Oral Pathol, 61: 522–526.16. Moore KL, Persaud TVN (1998) The DevelopmentalHuman. Clinically Oriented Embryology. 6th ed. W.B.Saunders Company, Philadelphia, London, Toronto,Montreal, Sydney, Tokyo.17. Murtagh RD, Caracciolo JT, Fernandez G (2001) CT find-ings associated with Eagle’s syndrome. Am J Neurol,22: 1401–1402.18. Scaf G, de Freitas DQ, de Castro Monteiro Loffredo L(2003) Diagnostic reproducibility of the elongated sty-loid process. J Appl Oral Sci, 11: 120–124.19. Silva HJ, Moraes SRA, Santos LCF, Albuquerque CI,Leonel T (2001) Dissection of the stylohyoid chain.A method of approach. Rev Chil Anat, 19: 145–148.20. Sokler K, Sandev S (2001) New classification of thestyloid process length — clinical application on thebiological base. Coll Antropol, 25: 627–632.21. Zaki HS, Greco CM, Rudy TE, Kubinski JA (1996) Elon-gated styloid process in a temporomandibular disor-der sample: prevalence and treatment outcome. J Pros-thet Dent, 75: 399–405.

Bilateral ossification of the stylohyoid ligament

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Bilateral ossification of the stylohyoid ligament

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