AN ABNORMALLY LONG STYLOID PROCESS WITH OSSIFICATION OF THE STYLOHYOID LIGAMENT

Address for Correspondence: Massimo Guarna,MD Assistant Professor, Department of MedicalSurgical Sciences and Neuroscience, University of Siena, Italy. E-Mail: guarna@unisi.it The styloid process of the temporal bone is an elongated bony projection presenting a variable length as demonstrated in osteometric and radiological studies conducted with different techniques: three-dimensional computed tomography (3dct) or dental panoramic three-dimensional scanning. An elongated styloid process can cause neck pain , dysphagia, headache, sore throat, ear pain, mandibular dysfunction which characterize Eagle’s syndrome. Here we present a rare image of an abnormally long styloid process with ossification of left stylohyoid ligament belonging to a bone collection of the local anatomical museum , part of our department, and discovered during routine osteology classes .Also if a direct relation between the length of the styloid process and syndrome of Eagle is not always obvious ,radiologists , neurologists,neurosurgeons, dentists, anesthetists and otolaryngologists could be aware of this bone anomaly to diagnose this syndrome.

The bone process gives insertion to muscles and ligaments: the stylohyoid and stylomandibular ligaments, as well as the muscles styloglossus , stylospharyngeus , stylohyod [2].The SL,derived from the ceratohyal part of Reichert's cartilage, extends from the apex of the SP to the tip of the lesser cornu of the hyoid bone.For unknown reason the ligament occasionally ossifies and forms a solid structure.However, the complete ossification is rare.Several studies conducted with different technique reported a variable length for the styloid process.Jung et al [3] with the study of panoramic radiography found an average value of 28 mm in length and claimed that the SP should be considered to be elongated, when its length was greater than 45 mm.As reported by Patil et al [4], in a recent osteometric study, the mean of length of SP was The styloid process(SP) of the temporal bone has a pointed shape and at the origin of the cranial base is covered by a tympanic bony sheath.In the fetus this process originates from Reichert's cartilage of the second brachial arch.This region of Reichert's cartilage has four separate centers of development: the tympanohyal, the stylohyal, the ceratohyal, and the hypohyal which give origin to different parts of styloid chain.The tympanohyal forms the basis of the (SP).The stylohyal becomes the stem of the SP.The ceratohyal part gives rise to the stylohyoid ligament (SL) and the hypohyal part forms the lesser cornu of the hyoid bone.In rare instances Reichert's cartilage developed into a bar of bone extending from the temporal bone to the hyoid bone [1].2.58 cm, and a SP longer than 3 cm was identified as an elongated SP.Although partial ossification of the SL is not uncommon, complete ossification is rare.We present the image of a rare anomaly characterized by a temporal bone SP abnormally long with a left ossified SL.The anatomical preparation belonged to a bone collection of the local anatomical museum of Siena "Leonetto Comparini."part of our department.

CASE REPORT
The SP length was measured using a digital caliper and photographed.The SP was long 50 mm on the right and 70 mm on the left (fig 1).The abnormally elongated SP was due to ossification of the SL (fig1) .It was attached to the skull base superiorly, just in front of the mastoid process, and inferiorly attached to the hyoid bone.These earlier large series suggest that a fully ossified and abnormally thickened SL is rare and atypical [11].Langlais et al [12] recognizes three types of elongated and ossified styloid processes: the first two are interrupted and have pseudo-articulations, the third is an uninterrupted segment formed by the ossified SL.Our case belongs to the third type.Campos et al. [13 ] reported that the etiology of styloid bone elongation can be explained by a genetic alteration or according to several theories.The ossification of the SL could be caused by a pharyngeal trauma which causes metaplastic change .According to the anatomic variance theory, the elongated SP and the ossified SL are anatomical variations that occur without any trauma.Clinical significance: The abnormal length of SP or the calcification /ossification of SL causing a pressure on neural and vascular structures is sometimes accompanied by a set of symptoms, as neck pain, dysphagia, headache, sore throat, ear pain, mandibular dysfunction which characterize Eagle's syndrome [14].About 4% of the population has an elongated SP, but only 4 to 10.3% of this group has symptoms of this syndrome [15].Also, if a direct relation between the length of the styloid process and syndrome of Eagle is not always obvious, we can assume that the person with this anomaly may have experienced this syndrome.In the present case, on the left side, we have observed ossification of SL.Diffuse ossification of SL is very rare, and it may remain asymptomatic throughout life.However ,especially in older patients it may restrict the neck movements ,and difficulty may arise during intubation.An immobile larynx, due to SL ossification would cause difficulties in direct laryngoscopy.
Cases of such a long SP in the dried human skull reported in the literature are quite scant while there are several radiologic studies of this anatomic anomaly.Prabhu et al [5],reported a case of bilateral elongated SP with the length of 60 and 59 mm on the right and left side, respectively.Paraskevas et al [6] presented a case of the dried skull with an elongated right SP with a length of 58 mm.Ishwar et al [7] reported a bilaterally elongated SP in dried skull measuring 60 mm.There might be serious traumatic consequences and possible risk of regurgitation and aspiration especially in emergency situations.Knowledge of the existence of an elongated styloid process and of its possible ossification must be well present to anatomists, radiologists, anesthetists, dentists,neurosurgeons and otolaryngologists.

Fig. 1 :
Fig.1: Arrow pointing the elongated styloid process and calcified stylohyoid ligament.Beder et al.[8]  diagnosed SP with the length of 42.5 mm on the right side and 41.5 mm on the left side by computed tomography.Using the same imaging technique,Savranlar et al [9]   described a case of elongated SP with the length of 45.6.Vougiouklakis reported in an autoptic study[10]  that 11/1215 of the cadavers had complete calcification of the SL.Nine out of the eleven cases were bilateral and 2/11 cases show unilateral ossification on the left side.These earlier large series suggest that a fully ossified and abnormally thickened SL is rare and atypical[11].Langlais et al [12]  recognizes three types of elongated and ossified styloid processes: the first two are interrupted and have pseudo-articulations, the third is an uninterrupted segment formed by the ossified SL.Our case belongs to the third type.Campos et al.[13 ] reported that the etiology of styloid bone elongation can be explained by a genetic alteration or according to several theories.The ossification of the SL could be caused by a pharyngeal trauma which causes metaplastic change .According to the anatomic variance theory, the elongated SP and the ossified SL are anatomical variations that occur without any trauma.Clinical significance: The abnormal length of SP or the calcification /ossification of SL causing a pressure on neural and vascular structures is sometimes accompanied by a set of symptoms, as neck pain, dysphagia, headache, sore throat, ear pain, mandibular dysfunction which characterize Eagle's syndrome[14].About 4% of the population has an elongated SP, but only 4 to 10.3% of this group has symptoms of this syndrome[15].Also, if a direct relation between the length of the styloid process and syndrome of Eagle is not always obvious, we can assume that the person with this anomaly may have experienced this syndrome.In the present case, on the left side, we have observed ossification of SL.Diffuse ossification of SL is very rare, and it may remain asymptomatic throughout life.However ,especially in older patients it may restrict the neck movements ,and difficulty may arise during intubation.An immobile larynx, due to SL ossification would cause difficulties in direct laryngoscopy.

DISCUSSION
Guarna M, Aglianò M. AN ABNORMALLY LONG STYLOID PROCESS WITH OSSIFICATION OF THE STYLOHYOID LIGAMENT.Guarna M, Aglianò M. AN ABNORMALLY LONG STYLOID PROCESS WITH OSSIFICATION OF THE STYLOHYOID LIGAMENT.