Surg Radiol Anat DOI 10.1007/s00276-014-1328-0
Anatomic Variations
Unilateral complete articulated ossification of the stylohyoid apparatus: case report and review of the literature Hubert Hardy · Benjamin Guichard · Mickael Eliezer · Olivier Choussy · Jean‑Marc Péron · Olivier Trost
Received: 31 December 2013 / Accepted: 12 June 2014 © Springer-Verlag France 2014
Abstract Anatomical variations of the stylohyoid apparatus are frequent. Two types can occur: an elongation of the stylohyoid ligament, from a long styloid process to a complete ossified structure connecting the skull base to the lesser horn of the hyoid bone, or the existence of supernumerary bones in the stylohyoid fibrous matrix, which sometimes resembles phalanges. These variations are in the majority of cases bilateral and symmetrical. The authors report the case of a 43-year-old male patient who presented with an unusual unilateral complete ossification of the stylohyoid apparatus, associated with vertebral and laryngeal calcifications. Original latest generation CT scan and threedimensional MRI imagery are provided to illustrate this rare case.
the lesser horn of the hyoid bone to the skull base. In some cases, the stylohyoid ligament can be divided into two or more supernumerary bones articulated through fibrous or cartilaginous joints, with more or less articulated osseous chains. In the majority of cases, stylohyoid apparatus ossifications or calcifications are bilateral, incomplete and fairly similar on both sides. To our knowledge stylohyoid variations are not related to other osteoligamentous variations or abnormalities. We report an original case of unilateral complete articulated ossification of the stylohyoid apparatus associated with a unilateral foramen arcuale and diffuse laryngeal calcifications in a 43-year-old man. Original latest generation three-dimensional CT scan and MRI imagery are shown in the figures.
Keywords Styloid process · Variation · Ossification · Calcification · Temporal bone · Eagle’s syndrome
Case report
Introduction Variations of the stylohyoid apparatus are frequent, well documented and in general asymptomatic. Sometimes an elongated styloid process can be involved in cervical aches and dysfunctions as described in the original article by Eagle [4]. Calcifications of a part or of the entire stylohyoid ligament can occur, resulting in an elongated styloid process. Complete stylohyoid ligament calcifications connect H. Hardy · B. Guichard · M. Eliezer · O. Choussy · J.-M. Péron · O. Trost (*) Department of Oral and Maxillofacial Surgery, Multidisciplinary Federation of Cervicomaxillofacial Oncology, Rouen University Hospital, Charles Nicolle Hospital, 1 rue de Germont, 76031 Rouen, France e-mail: olivier.trost@chu‑rouen.fr
A 43-year-old man was referred to the Department of Oral and Maxillofacial Surgery for the management of a left mandibular cyst. Panoramic X-ray examination showed an unusual variation of the styloid process of the right temporal bone. The patient did not recall any injury or surgical procedure in the cervicofacial region and had no functional complaint on the right side. In particular, he had neither discomfort nor pain during swallowing or head movements. Panoramic X-ray revealed a right stylohyoid apparatus with four articulated supernumerary bones resembling phalanges (a student during the hospital staff meeting of the Department wondered whether “the patient ate his index finger”). The proximal segment was articulated with the petrous part of the temporal bone whereas the distal segment was separated from the lesser horn of the hyoid bone through a thin space. The left stylohyoid process was considered normal (Fig. 1).
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Surg Radiol Anat
Fig. 1 Panoramic X-ray. The right ossified stylohyoid apparatus looks like an index finger
A 3D CT scan was performed in order to complete the diagnosis (Philips®, 16 slices, HT = 120 kV, charge = 80 mA, Pitch = 1.0, slice thickness = 5 mm, scanning = 30 cm, CTDIvol = 8 mGy, PDL = 240 mGy. cm). The styloid ligament was entirely ossified except for a distal attachment to the hyoid bone through a thin fibrous structure. The total length of these supernumerary bones was 65 mm. Each joint was ellipsoid, opposing two ovoid articular surfaces. The “finger like” aspect of the joints between the different segments was typical of styloid ligament ossifications. The left styloid process was morphologically normal with a length of 23 mm (Figs. 2, 3). Three-dimensional CT scan reconstructions showed another anatomic variation on the left side: a posterior ponticle of the atlas (C1) over the groove for the vertebral artery. Moreover, the thyroid cartilage of the larynx was almost completely mineralized (Figs. 4, 5). In addition, a three-dimensional MRI examination was performed to complete the analysis of this unusual anatomic variation. The joints appeared similar to a synchondrosis (low T1 signal, non-enhancement after gadolinium injection). The distal segment part of the stylohyoid apparatus was connected to the lesser horn of the hyoid bone with fibrous tissue, which was interpreted to be a remaining styloid ligament (Fig. 6).
Discussion Several classifications of the stylohyoid apparatus variations have been reported in the literature. Viéla suggested a classification based on the morphogenesis of the skull [13]. In fact, the stylohyoid apparatus originates from Reichert’s cartilage, a part of the second branchial arch. Later on, this cartilage provides the stapes bone, the styloid process of the temporal bone, the stylohyoid ligament and the lesser horn of the hyoid bone. According to Viéla, in complete ossification cases, four supernumerary bones are described from the skull base to the hyoid bone: epihyal, stylhyal,
13
Fig. 2 CT scan examination of the right stylohyoid apparatus, anteroposterior section, lateral view. The entire apparatus is ossified except in the very distal part. Each supernumerary bone is articulated with the adjacent one
ceratohyal and hypohyal. In our case, the observed supernumerary bones corresponded to those of the classification of Viéla, except for its unilaterality. Langlais et al. [7] proposed a radiological classification in three types: elongated, pseudo articulated or segmented styloid process. Furthermore, these authors described a pattern of calcifications in four groups: calcified outline, partially calcified, nodular and completely calcified. This radiological classification seemed anatomically less pertinent than Viéla’s. We are not in agreement with the expression “pseudoarticulated” used by these authors because we considered that all structures relating two or more bones should be named either joints or articulations, without any distinction between regular or supernumerary bones. The most common classification cited in the literature was reported by Okabe et al., based on embryological considerations. Twelve subtypes were described depending on the ossified segment part of the ligament [9]. Stylohyoid apparatus variations are frequent in general, occurring in more than 18 % of patients in a radiographic study on 1,771 patients by Corell et al. [3]. These variations seemed more frequent in elderly patients, afflicting men and women indifferently. The size of the mineralized parts of the ligament greatly varied from patient to patient, but
Surg Radiol Anat
Fig. 5 Three-dimensional CT scan reconstruction of the left cervical region, lateral view. Stylohyoid apparatus has a normal length and appearance. The posterior ponticle of the atlas over the groove of the vertebral artery is completely ossified Fig. 3 CT scan examination, frontal section, posterior view. The left stylohyoid apparatus has a classic aspect with a styloid process of normal length. On the right side, segmented ossified ligament is shown. Note the epihyal segment of the apparatus in the continuity of the temporal process of the temporal bone
Fig. 6 MRI examination of the right stylohyoid apparatus on a sagittal section, lateral view. Low T1 intensity in the joint structures suggested a synchondrosis between different bone segments of the apparatus
Fig. 4 Three-dimensional CT scan reconstruction of the right stylohyoid apparatus, inferolateral view. The index finger like structure of the ligament is well visualized. The hypohyal segment, not completely ossified, is situated next to the hyoid bone. The thyroid cartilage is almost completely mineralized
this decreased with age. It could be interpreted as a consequence of the physiologic bone demineralization according to these authors. Ossifications and calcifications were present bilaterally in 93 % of cases. However, completely ossified unilateral segmented stylohyoid apparatus was rare
13
and represented less than 0.9 % according to Vougiouklakis in a review of 1,215 autopsies [14]. Ossification or osteogenesis, and calcification, are two distinct phenomena [12]. Ossification is due to a mineralized organic matrix set-up leading to bone formation. Calcification corresponds to calcium phosphate deposition constituting physiological or pathological structures, that do not have the same morphological or biomechanical signification as bone. Steinman distinguished two kinds of situations leading to these variations: trauma (accident or surgery) or congenital. According to this author, trauma would cause calcifications of the ligament whereas congenital cases would be ossified [11]. As a result Viéla’s classification seems clinically more pertinent. The histopathological sequence of stylohyoid ligament mineralization was discussed by Carmada et al. who coined the term “calcification”. According to their observations, bony structures in the stylohyoid ligament could be an intraligamentary metaplasic phenomenon [1]. However, this scarcely explained cartilaginous surfaces found in some articulations. In contrast, Gokce proposed that abnormally high concentration of osseous metabolites (calcium, phosphorus, vitamin D) would cause intraligamentary calcifications and could be observed in some pathologic conditions causing calcium deposits as in end-stage renal insufficiency [6]. Based on 241 dissections, Frommer showed that the joint between the different segments could be fibrous (ligament or synfibrosis) or cartilaginous (synchondrosis). Cartilaginous joints are more likely to be observed in congenital ossification cases [5]. In clinical practice, Eagle’s syndrome or elongated styloid process syndrome is often found in a context of oral or cervical trauma [4]. This would suggest stylohyoid ligament calcifications or scar fibrosis compressing neurovascular structures exiting from the skull base between the mineralized ligament and the lateral mass of the atlas. It also typically complicates tonsillectomy. Prades [10] suggested that the close relationships between the glossopharyngeal nerve and the styloid muscles inserting on the styloid process could be involved in stylohyoid complex syndromes. In his cadaveric study on ten specimen, he analyzed the course of the extracranial part of the IX, focusing on its relationships with the styloid muscles, vessels and the transverse process of the atlas (C1). However no significant variation of the styloid process was noticed by this author. The review of the articles reporting ossified styloid chains did not feature comments on the position of the glossopharyngeal nerve. According to Colby and del Gaudio, the stylohyoid apparatus ossifications are commonly associated with a pseudo, stylohyoid syndrome, mimicking an Eagle’s syndrome but without any trauma [2]. In the case study, we report that the stylohyoid ossification was associated with a posterior ponticle of the atlas
13
Surg Radiol Anat
over the groove of the vertebral artery, and calcifications of the thyroid cartilage. This argues for a congenital origin of these variations. The presence of a ponticle of the atlas was studied among primates and humans by Le Minor and Trost in 2004 [8] and seemed to depend on genetic factors. These authors interpreted the bony ponticle as the result of the intraosseous canal of the vertebral artery in the lateral mass of C1 in the vertebrae. In normal cases, a ligament covers the vertebral artery over the posterior arch of C1. The presence of a ponticle can be considered as a calcification of this ligament, especially if we consider quite frequent incomplete ponticles. In our case, multiple calcifications observed in fibrous structures of head and neck suggested general or genetic factors. The occurrence of other calcifications or supernumerary bones in this patient was not investigated. Acknowledgments The authors thank Richard Medeiros, Rouen University Hospital Medical Editor, for editing the manuscript. The authors wish to thank N. Zwetyenga, from the University of Dijon, France, for providing some of the pictures. Conflict of interest The authors declare that there is no conflict of interest.
References 1. Camarda AJ, Deschamps C, Forest D (1989) I. Stylohyoid chain ossification: a discussion of etiology. Oral Surg Oral Med Oral Pathol 67:508–514 2. Colby CC, Del Gaudio JM (2011) Stylohyoid complex syndrome: a new diagnostic classification. Arch Otolaryngol Head Neck Surg 137:248–252 3. Correll RW, Jensen JL, Taylor JB, Rhyne RR (1979) Mineralization of the stylohyoid–stylomandibular ligament complex. A radiographic incidence study. Oral Surg Oral Med Oral Pathol 48:286–291 4. Eagle W (1937) Elongated styloid process. Arch Otolaryngol 25:584–587 5. Frommer J (1974) Anatomic variations in the stylohyoid chain and their possible clinical significance. Oral Surg Oral Med Oral Pathol 38:659–667 6. Gokce C, Sisman Y, Sipahioglu M (2008) Styloid process elongation or eagle’s syndrome: is there any role for ectopic calcification? Eur J Dent 2:224–228 7. Langlais RP, Miles DA, Van Dis ML (1986) Elongated and mineralized stylohyoid ligament complex: a proposed classification and report of a case of Eagle’s syndrome. Oral Surg Oral Med Oral Pathol 61:527–532 8. Le Minor JM, Trost O (2004) Bony ponticles of the atlas (C1) over the groove for the vertebral artery in humans and primates: polymorphism and evolutionary trends. Am J Phys Anthropol 125:16–29 9. Okabe S, Morimoto Y, Ansai T, Yamada K, Tanaka T, Awano S, Kito S, Takata Y, Takehara T, Ohba T (2006) Clinical significance and variation of the advanced calcified stylohyoid complex detected by panoramic radiographs among 80-year-old subjects. Dentomaxillofac Radiol 35:191–199 10. Prades JM, Gavid M, Asanau A, Timoshenko AP, Richard C, Martin CH (2014) Surgical anatomy of the styloid muscles and the extracranial glossopharyngeal nerve. Surg Radiol Anat 36:141–146
Surg Radiol Anat 11. Steinmann EP (1968) Styloid syndrome in absence of an elongated process. Acta Otolaryngol 66:347–356 12. Trost O, Trouilloud P (2013) Ostéologie. In: Introduction à l’anatomie, 2nd edn. Ellipses ed, Paris, pp 19–20 13. Viéla A (1925) Contribution à l’étude des anomalies de l’appareil hyoïdien. Bulletins et Mémoires de la Société d’anthropologie de Paris VIIe série (Tome 6, fascicule 1–3):89–97
14. Vougiouklakis T (2006) Overview of the ossified stylohyoid ligament based in more than 1200 forensic autopsies. J Clin Forensic Med 13:268–270
13
Anatomic Variations
Unilateral complete articulated ossification of the stylohyoid apparatus: case report and review of the literature Hubert Hardy · Benjamin Guichard · Mickael Eliezer · Olivier Choussy · Jean‑Marc Péron · Olivier Trost
Received: 31 December 2013 / Accepted: 12 June 2014 © Springer-Verlag France 2014
Abstract Anatomical variations of the stylohyoid apparatus are frequent. Two types can occur: an elongation of the stylohyoid ligament, from a long styloid process to a complete ossified structure connecting the skull base to the lesser horn of the hyoid bone, or the existence of supernumerary bones in the stylohyoid fibrous matrix, which sometimes resembles phalanges. These variations are in the majority of cases bilateral and symmetrical. The authors report the case of a 43-year-old male patient who presented with an unusual unilateral complete ossification of the stylohyoid apparatus, associated with vertebral and laryngeal calcifications. Original latest generation CT scan and threedimensional MRI imagery are provided to illustrate this rare case.
the lesser horn of the hyoid bone to the skull base. In some cases, the stylohyoid ligament can be divided into two or more supernumerary bones articulated through fibrous or cartilaginous joints, with more or less articulated osseous chains. In the majority of cases, stylohyoid apparatus ossifications or calcifications are bilateral, incomplete and fairly similar on both sides. To our knowledge stylohyoid variations are not related to other osteoligamentous variations or abnormalities. We report an original case of unilateral complete articulated ossification of the stylohyoid apparatus associated with a unilateral foramen arcuale and diffuse laryngeal calcifications in a 43-year-old man. Original latest generation three-dimensional CT scan and MRI imagery are shown in the figures.
Keywords Styloid process · Variation · Ossification · Calcification · Temporal bone · Eagle’s syndrome
Case report
Introduction Variations of the stylohyoid apparatus are frequent, well documented and in general asymptomatic. Sometimes an elongated styloid process can be involved in cervical aches and dysfunctions as described in the original article by Eagle [4]. Calcifications of a part or of the entire stylohyoid ligament can occur, resulting in an elongated styloid process. Complete stylohyoid ligament calcifications connect H. Hardy · B. Guichard · M. Eliezer · O. Choussy · J.-M. Péron · O. Trost (*) Department of Oral and Maxillofacial Surgery, Multidisciplinary Federation of Cervicomaxillofacial Oncology, Rouen University Hospital, Charles Nicolle Hospital, 1 rue de Germont, 76031 Rouen, France e-mail: olivier.trost@chu‑rouen.fr
A 43-year-old man was referred to the Department of Oral and Maxillofacial Surgery for the management of a left mandibular cyst. Panoramic X-ray examination showed an unusual variation of the styloid process of the right temporal bone. The patient did not recall any injury or surgical procedure in the cervicofacial region and had no functional complaint on the right side. In particular, he had neither discomfort nor pain during swallowing or head movements. Panoramic X-ray revealed a right stylohyoid apparatus with four articulated supernumerary bones resembling phalanges (a student during the hospital staff meeting of the Department wondered whether “the patient ate his index finger”). The proximal segment was articulated with the petrous part of the temporal bone whereas the distal segment was separated from the lesser horn of the hyoid bone through a thin space. The left stylohyoid process was considered normal (Fig. 1).
13
Surg Radiol Anat
Fig. 1 Panoramic X-ray. The right ossified stylohyoid apparatus looks like an index finger
A 3D CT scan was performed in order to complete the diagnosis (Philips®, 16 slices, HT = 120 kV, charge = 80 mA, Pitch = 1.0, slice thickness = 5 mm, scanning = 30 cm, CTDIvol = 8 mGy, PDL = 240 mGy. cm). The styloid ligament was entirely ossified except for a distal attachment to the hyoid bone through a thin fibrous structure. The total length of these supernumerary bones was 65 mm. Each joint was ellipsoid, opposing two ovoid articular surfaces. The “finger like” aspect of the joints between the different segments was typical of styloid ligament ossifications. The left styloid process was morphologically normal with a length of 23 mm (Figs. 2, 3). Three-dimensional CT scan reconstructions showed another anatomic variation on the left side: a posterior ponticle of the atlas (C1) over the groove for the vertebral artery. Moreover, the thyroid cartilage of the larynx was almost completely mineralized (Figs. 4, 5). In addition, a three-dimensional MRI examination was performed to complete the analysis of this unusual anatomic variation. The joints appeared similar to a synchondrosis (low T1 signal, non-enhancement after gadolinium injection). The distal segment part of the stylohyoid apparatus was connected to the lesser horn of the hyoid bone with fibrous tissue, which was interpreted to be a remaining styloid ligament (Fig. 6).
Discussion Several classifications of the stylohyoid apparatus variations have been reported in the literature. Viéla suggested a classification based on the morphogenesis of the skull [13]. In fact, the stylohyoid apparatus originates from Reichert’s cartilage, a part of the second branchial arch. Later on, this cartilage provides the stapes bone, the styloid process of the temporal bone, the stylohyoid ligament and the lesser horn of the hyoid bone. According to Viéla, in complete ossification cases, four supernumerary bones are described from the skull base to the hyoid bone: epihyal, stylhyal,
13
Fig. 2 CT scan examination of the right stylohyoid apparatus, anteroposterior section, lateral view. The entire apparatus is ossified except in the very distal part. Each supernumerary bone is articulated with the adjacent one
ceratohyal and hypohyal. In our case, the observed supernumerary bones corresponded to those of the classification of Viéla, except for its unilaterality. Langlais et al. [7] proposed a radiological classification in three types: elongated, pseudo articulated or segmented styloid process. Furthermore, these authors described a pattern of calcifications in four groups: calcified outline, partially calcified, nodular and completely calcified. This radiological classification seemed anatomically less pertinent than Viéla’s. We are not in agreement with the expression “pseudoarticulated” used by these authors because we considered that all structures relating two or more bones should be named either joints or articulations, without any distinction between regular or supernumerary bones. The most common classification cited in the literature was reported by Okabe et al., based on embryological considerations. Twelve subtypes were described depending on the ossified segment part of the ligament [9]. Stylohyoid apparatus variations are frequent in general, occurring in more than 18 % of patients in a radiographic study on 1,771 patients by Corell et al. [3]. These variations seemed more frequent in elderly patients, afflicting men and women indifferently. The size of the mineralized parts of the ligament greatly varied from patient to patient, but
Surg Radiol Anat
Fig. 5 Three-dimensional CT scan reconstruction of the left cervical region, lateral view. Stylohyoid apparatus has a normal length and appearance. The posterior ponticle of the atlas over the groove of the vertebral artery is completely ossified Fig. 3 CT scan examination, frontal section, posterior view. The left stylohyoid apparatus has a classic aspect with a styloid process of normal length. On the right side, segmented ossified ligament is shown. Note the epihyal segment of the apparatus in the continuity of the temporal process of the temporal bone
Fig. 6 MRI examination of the right stylohyoid apparatus on a sagittal section, lateral view. Low T1 intensity in the joint structures suggested a synchondrosis between different bone segments of the apparatus
Fig. 4 Three-dimensional CT scan reconstruction of the right stylohyoid apparatus, inferolateral view. The index finger like structure of the ligament is well visualized. The hypohyal segment, not completely ossified, is situated next to the hyoid bone. The thyroid cartilage is almost completely mineralized
this decreased with age. It could be interpreted as a consequence of the physiologic bone demineralization according to these authors. Ossifications and calcifications were present bilaterally in 93 % of cases. However, completely ossified unilateral segmented stylohyoid apparatus was rare
13
and represented less than 0.9 % according to Vougiouklakis in a review of 1,215 autopsies [14]. Ossification or osteogenesis, and calcification, are two distinct phenomena [12]. Ossification is due to a mineralized organic matrix set-up leading to bone formation. Calcification corresponds to calcium phosphate deposition constituting physiological or pathological structures, that do not have the same morphological or biomechanical signification as bone. Steinman distinguished two kinds of situations leading to these variations: trauma (accident or surgery) or congenital. According to this author, trauma would cause calcifications of the ligament whereas congenital cases would be ossified [11]. As a result Viéla’s classification seems clinically more pertinent. The histopathological sequence of stylohyoid ligament mineralization was discussed by Carmada et al. who coined the term “calcification”. According to their observations, bony structures in the stylohyoid ligament could be an intraligamentary metaplasic phenomenon [1]. However, this scarcely explained cartilaginous surfaces found in some articulations. In contrast, Gokce proposed that abnormally high concentration of osseous metabolites (calcium, phosphorus, vitamin D) would cause intraligamentary calcifications and could be observed in some pathologic conditions causing calcium deposits as in end-stage renal insufficiency [6]. Based on 241 dissections, Frommer showed that the joint between the different segments could be fibrous (ligament or synfibrosis) or cartilaginous (synchondrosis). Cartilaginous joints are more likely to be observed in congenital ossification cases [5]. In clinical practice, Eagle’s syndrome or elongated styloid process syndrome is often found in a context of oral or cervical trauma [4]. This would suggest stylohyoid ligament calcifications or scar fibrosis compressing neurovascular structures exiting from the skull base between the mineralized ligament and the lateral mass of the atlas. It also typically complicates tonsillectomy. Prades [10] suggested that the close relationships between the glossopharyngeal nerve and the styloid muscles inserting on the styloid process could be involved in stylohyoid complex syndromes. In his cadaveric study on ten specimen, he analyzed the course of the extracranial part of the IX, focusing on its relationships with the styloid muscles, vessels and the transverse process of the atlas (C1). However no significant variation of the styloid process was noticed by this author. The review of the articles reporting ossified styloid chains did not feature comments on the position of the glossopharyngeal nerve. According to Colby and del Gaudio, the stylohyoid apparatus ossifications are commonly associated with a pseudo, stylohyoid syndrome, mimicking an Eagle’s syndrome but without any trauma [2]. In the case study, we report that the stylohyoid ossification was associated with a posterior ponticle of the atlas
13
Surg Radiol Anat
over the groove of the vertebral artery, and calcifications of the thyroid cartilage. This argues for a congenital origin of these variations. The presence of a ponticle of the atlas was studied among primates and humans by Le Minor and Trost in 2004 [8] and seemed to depend on genetic factors. These authors interpreted the bony ponticle as the result of the intraosseous canal of the vertebral artery in the lateral mass of C1 in the vertebrae. In normal cases, a ligament covers the vertebral artery over the posterior arch of C1. The presence of a ponticle can be considered as a calcification of this ligament, especially if we consider quite frequent incomplete ponticles. In our case, multiple calcifications observed in fibrous structures of head and neck suggested general or genetic factors. The occurrence of other calcifications or supernumerary bones in this patient was not investigated. Acknowledgments The authors thank Richard Medeiros, Rouen University Hospital Medical Editor, for editing the manuscript. The authors wish to thank N. Zwetyenga, from the University of Dijon, France, for providing some of the pictures. Conflict of interest The authors declare that there is no conflict of interest.
References 1. Camarda AJ, Deschamps C, Forest D (1989) I. Stylohyoid chain ossification: a discussion of etiology. Oral Surg Oral Med Oral Pathol 67:508–514 2. Colby CC, Del Gaudio JM (2011) Stylohyoid complex syndrome: a new diagnostic classification. Arch Otolaryngol Head Neck Surg 137:248–252 3. Correll RW, Jensen JL, Taylor JB, Rhyne RR (1979) Mineralization of the stylohyoid–stylomandibular ligament complex. A radiographic incidence study. Oral Surg Oral Med Oral Pathol 48:286–291 4. Eagle W (1937) Elongated styloid process. Arch Otolaryngol 25:584–587 5. Frommer J (1974) Anatomic variations in the stylohyoid chain and their possible clinical significance. Oral Surg Oral Med Oral Pathol 38:659–667 6. Gokce C, Sisman Y, Sipahioglu M (2008) Styloid process elongation or eagle’s syndrome: is there any role for ectopic calcification? Eur J Dent 2:224–228 7. Langlais RP, Miles DA, Van Dis ML (1986) Elongated and mineralized stylohyoid ligament complex: a proposed classification and report of a case of Eagle’s syndrome. Oral Surg Oral Med Oral Pathol 61:527–532 8. Le Minor JM, Trost O (2004) Bony ponticles of the atlas (C1) over the groove for the vertebral artery in humans and primates: polymorphism and evolutionary trends. Am J Phys Anthropol 125:16–29 9. Okabe S, Morimoto Y, Ansai T, Yamada K, Tanaka T, Awano S, Kito S, Takata Y, Takehara T, Ohba T (2006) Clinical significance and variation of the advanced calcified stylohyoid complex detected by panoramic radiographs among 80-year-old subjects. Dentomaxillofac Radiol 35:191–199 10. Prades JM, Gavid M, Asanau A, Timoshenko AP, Richard C, Martin CH (2014) Surgical anatomy of the styloid muscles and the extracranial glossopharyngeal nerve. Surg Radiol Anat 36:141–146
Surg Radiol Anat 11. Steinmann EP (1968) Styloid syndrome in absence of an elongated process. Acta Otolaryngol 66:347–356 12. Trost O, Trouilloud P (2013) Ostéologie. In: Introduction à l’anatomie, 2nd edn. Ellipses ed, Paris, pp 19–20 13. Viéla A (1925) Contribution à l’étude des anomalies de l’appareil hyoïdien. Bulletins et Mémoires de la Société d’anthropologie de Paris VIIe série (Tome 6, fascicule 1–3):89–97
14. Vougiouklakis T (2006) Overview of the ossified stylohyoid ligament based in more than 1200 forensic autopsies. J Clin Forensic Med 13:268–270
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