Overview of the Ossified Stylohyoid Ligament Based in More Than 1200 Forensic Autopsies

JOURNAL OF CLINICAL FORENSIC MEDICINE Journal of Clinical Forensic Medicine 13 (2006) 268–270 www.elsevier.com/locate/jcfm Original communication Overview of the ossiﬁed stylohyoid ligament based in more than 1200 forensic autopsies

Theodore Vougiouklakis *

University of Ioannina, Department of Forensic Medicine and Toxicology, University Campus, 451 10 Ioannina, Greece

Received 25 May 2005; received in revised form 10 August 2005; accepted 28 September 2005 Available online 25 January 2006

Abstract

The human stylohyoid chain presents considerable anatomic variability. In a personal series of 1215 forensic autopsies, eleven cases of complete ossification of the stylohyoid ligament have been revealed. Nine cases were bilateral and two cases were unilateral ossifications. A fractured ossified stylohyoid ligament was found in one case. The embryology and clinical significance of this condition has been men- tioned briefly. Ó 2005 Elsevier Ltd and AFP. All rights reserved.

Keywords: Stylohyoid; Ossiﬁcation; Forensic; Autopsy; Incidence; Fracture

1. Introduction 2. Methodology – Results

The human stylohyoid chain includes the styloid pro- In a series of 1215 forensic autopsies performed in our cess (SP), the stylohyoid ligament (SHL), and the lesser department a careful dissection of the neck structures com- cornu of the hyoid bone. The stylohyoid chain is derived plex was done by 1 investigator. Only a macroscopic exam- from the second branchial arch and is sub-divided into ination of the stylohyoid chain was carried out; four parts: the segment known as tympanohyale, the sty- radiographs and histological slices were not regularly lohyale, the ceratohyale, and the hypohyale.1 The SHL is made. Therefore only a completely ossification of the a connective tissue band originating from the apex of the SHL could be detectable; for example, the extent of ossifi- SP and is attached to the lesser horn of the hyoid bone. cation could not be considered with this simple method. For no obvious reason it occasionally ossifies and forms Ossifications of the SHL were found in 11 cases (0.9%). a solid structure. Various degrees of ossification may be Males were 7/11 cases and females were 4/11 cases (male/ observed in SHL because of the cartilaginous content of female ratio: 1.75). Age distribution of the diseased the ligament. Although the partial ossification of the sty- showed: 2 cases in the 2nd decade, 5 cases in the 3rd dec- lohyoid ligament is not uncommon, the complete ossifica- ade, 3 cases in the 4th decade and 1case in the 6th decade tion is rare.2 Variable radiographic appearances may be of life. Nine out of the eleven cases were bilateral and 2/11 present due to variations in ossification and fusion of cases were unilateral ossifications in the left side (Fig. 1). In elements.3 one case was found a fractured ossified SHL. The case con- To our knowledge this is the first report about ossified cerned a 23-year-old man who was involved in a fatal road SHL presented in the forensic literature. incident as the passenger of a bus. Autopsy revealed several injuries on the left side of the neck consequence of blunt impact. Dissection of the neck structures revealed bilateral * Tel.: +30 2651 097614; fax: +30 2651 097857. completely ossified stylohyoid ligaments. The left ligament E-mail address: [email protected]. was recently fractured in the middle.

suggested that the vast majority of ossified sites in the stylohyoid ligaments are established during childhood and adolescence. The mean length of these sites has shown a rapid, linear increase with age until the end of adolescence; any further increase has been not linear and has occurred at a much slower rate.8 Fractures of an ossified SHL are an uncommon and unusual entity that could be seen incidentally during autopsy. Generalisations on the fractures of ossified SHL are impossible because of the limited reported cases in the literature. The inciting cause may be as mild as yawning but more often blunt trauma of a serious nature, like in our case, is the cause.9,10 In cases without ossification, specimens often remained macroscopically uninjured. Symptoms are non-specific and rarely occur before the age of 40. An elongated SHL or SL process is considered to be the source of craniofacial and cervical pain com- monly known as EagleÕs syndrome.11 Fig. 1. The figure nicely illustrates the stylohyoid ligament that ossified An ossified SHL has been implicated as a cause of unan- from the skull base all the way to the hyoid bone. ticipated difficulty in tracheal intubation. An immobile lar- ynx, as direct result of SHL ossification and the elevation 3. Discussion of the epiglottis due to forward traction of the hyoid bone would render direct laryngoscopy difficult. If not well man- The presence of the ossified stylohyoid ligament and aged, there may be serious traumatic consequences and possible risk of regurgitation and aspiration especially in elongated styloid has been noted both, with and without 12–14 symptoms, by various authors in the late nineteenth and emergency situation. early twentieth centuries.4 The reported incidence of Moreover, a simultaneous occurrence of an ossified 5 SHL and anomalies in the atlantic section of the vertebral radiographic stylohyoid ossification varied from 1.4% to 15 84.4%6, most probably due to different definitions used to artery has been also reported. The discovery of an ossi- describe this phenomenon. The condition is usually bilateral, fied SHL seems to be a warning for potential arterial but it has been reported to occur unilaterally. Although the anomalies. These subjects may be more susceptible to a term calcification has been originally used, this terminology variety of head and neck insults resulting to disturbance is considered erroneous.7 The definition as ossification is in blood flow. Consequently, such anomalies should be recorded during autopsy in subjects who die as a result of considered more precise, since histologically the specimen 16,17 will exhibit either hyperplasia of the styloid process or fatal vertebral artery injuries. This consideration may metaplasia of stylohyoid ligament into bone (Fig. 2). have clinical and medico legal implications for therapists Different suggestions have been put forward regarding who perform spinal manipulation in the cervical region. the extent of ossification versus age. Previous studies have It is important for the therapist to identify patients at risk of complications from minor trauma and in the presence of any signs of vertebrobasilar insufficiency such manipulation should be avoided.

References

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