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StatPearls . Sweetheart Island (FL): StatPearls Publishing; 2021 Jan-.


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Introduction

The hyoid bone (hyoid) is a little U-shaped (horseshoe-shaped) solitary bone, positioned in the midline the the neck anteriorly at the base the the mandible and posteriorly in ~ the 4th cervical vertebra. The anatomical position is simply superior come the thyroid cartilage. The is closely linked with an extended tendon-muscular complicated but not especially interconnected to any nearby bones and hence is taken into consideration by many anatomists and anthropologists to it is in an unconventional bone. That is anchored in the anterior triangle of the neck by muscles from the larynx, pharynx, tongue, and also the floor of the mouth. The surname hyoid derives native the Greek word “hyodeides,” which means “shaped like the letter Upsilon.” Although referred to as as an unconventional bone, the hyoid gift a part of the hyoid-larynx complicated is undoubtedly a bone that clinical and also forensic significance.


Structure and also Function

The hyoid consists of a body, two better horns, and two lesser horns.<1> The body develops the central quadrilateral-shaped broad segment of the hyoid. The higher horns are larger and also longer than the lesser horns of the hyoid. The better horns and lesser horns are also known together cornu majus and cornu minus, respectively. The body and also the higher horns appear to offer the hyoid that U-shape through the greater horns forming the limbs of the "U" on either side of the body. The greater and lesser horns normally unite come the body of the hyoid via fibrous tissue or a true joint.<2> As age progresses, over there is a physiological development of ankylosis the the joints connecting the greater and also lesser horns v the body of the hyoid.  

The hyoid takes part in all feasible functional actions of the orofacial complex. That preserves the patency the the airway in between the oropharynx above and tracheal ring below. It additionally connects come the larynx and also hence theatre a duty in phonation. Other functions incorporate tongue movement, mastication, swallowing, prevention of regurgitation, and even respiration.<1><3> Furthermore, the hyoid maintains the posture of the head, due to the complex connection it presumes in between the mandible and also the cervical spine.<1>


Embryology

The second pharyngeal arch creates the lesser horn (cornu) and also the upper body the the hyoid, while the higher horn (cornu) and also the lower portion of the human body derive indigenous the third pharyngeal arch. This embryonic development of the hyoid remains controversial.<1> The ossification that the greater horns occurs toward the end of the common gestational duration of the fetus; this is adhered to by the ossification of the body of the hyoid shortly after birth. Eventually, ossification the the lesser horns occurs throughout the very first or second year after ~ birth. Later on in adulthood, typically the horns fuse with the body, yet this may not take ar in every individuals. The hyoid is situated anterior come the 2nd and third cervical vertebra throughout infancy, and also ultimately in adulthood, it descends come the level that the fourth and fifth cervical vertebra. The descent takes location simultaneously through the other functionally appropriate structures consisting of the epiglottis and also the larynx.<3>


Muscles

The hyoid attributes as an anchor for the suprahyoid muscles (digastric, stylohyoid, mylohyoid and also geniohyoid) as well as the infrahyoid muscle (sternohyoid, sternothyroid, omohyoid, and thyrohyoid).<2> The stylohyoid ligament suspends the hyoid native the temporal styloid procedure on one of two people side. It is limited by the ligamentous attachments inferiorly to the superior facet of the thyroid cartilage through the thyrohyoid membrane. Additionally, the hyoid is attached come the cervical spine posteriorly via the cervical fascia.<1>

Suprahyoid Muscles

The suprahyoid muscle are four in number ~ above either side of the anterior midline above the level of the hyoid (Media Image, Table 1). They attach the hyoid come the mandible, tongue, and skull. The digastric muscle has two bellies, posterior and also anterior. The anterior belly originates from the digastric fossa the the mandible, if the posterior ship originates native the mastoid notch. Both the digastric bellies insert come the intermediary tendon the the digastric muscle i beg your pardon is attached come the hyoid. The stylohyoid muscle originates native the temporal styloid process; it is a thin and long muscle that lies parallel to the posterior belly of the digastric. The mylohyoid muscle originates native the mylohyoid heat of the mandible; it is a thin muscle that upholds and makes up the floor of the mouth while also creating a sling inferior to the tongue. The geniohyoid muscle is a narrow and also short muscle that originates indigenous the internal mental spine of the symphysis menti. The stylohyoid, mylohyoid, and also geniohyoid insert on the body of the hyoid.<1>

Infrahyoid Muscles

The infrahyoid muscle are 4 pairs the muscles located in the anterior component of the neck (Media Image, Table 2). They are found between the hyoid over and the shoulder girdle below. The sternohyoid muscle primarily originates indigenous the ago of the manubrium and also inserts top top the medial part of the inferior border that the hyoid body. The sternothyroid muscle originates mostly from the earlier of the manubrium and also inserts on the oblique line of the thyroid cartilage. The omohyoid muscle has actually a exceptional belly and also an inferior belly. The premium belly of the omohyoid arises from the intermediate tendon that the omohyoid and inserts on the hyoid. The inferior belly of the omohyoid originates native the scapular exceptional border and inserts to the intermediate tendon that the omohyoid. The thyrohyoid muscle originates from the oblique line of the thyroid cartilage and inserts in ~ the inferior facet of the body of the hyoid and the greater cornu.<1><4>

Other Muscles regarded the Hyoid

The hyoglossus and the center pharyngeal constrictor originate indigenous the hyoid. These muscles do not kind the team as mentioned above of muscles concerned the hyoid.

Elevation the the Hyoid

The digastric, stylohyoid, mylohyoid and also geniohyoid role in elevating the hyoid.

Depression that the Hyoid

The sternohyoid, sternothyroid, omohyoid, and thyrohyoid function in depressing the hyoid.


Physiologic Variants

The hyoid shows a wide selection of anatomical variations, most likely owing come the asymmetry that the greater and also lesser horns. Therefore, the hyoid is taken into consideration one that the many polymorphic parts of the human being body. The commonest sports of the hyoid takes location in the procedure of ankylosis the the joints between the horns (greater and also lesser horns) and the body the the hyoid. Ethnicity, sex, age, height, and also weight that the subject add to the morphological variations. These variations can take place unilaterally, bilaterally, and also multiple variations can take place in the very same individual.<2> Surprisingly, the lack of the hyoid has actually been reported also in a masculine neonate who was additionally a teratoma case, had actually a mandibular cleft, and also suffered from respiratory distress.<5> this anomalies correlate to part clinical problems such as micrognathia, Pierre Robin sequence, and also cleft lip and palate. Symptoms caused by these anomalies encompass dysphagia, neck movement limitations and also foreign body sensation in the throat.<2>


Surgical Considerations

The Hyoid and also its relation to Blood Vessels

The pointer of the greater horn of the hyoid is a significant landmark for cervical surgery in the mid-neck region. The carotid bifurcation, the remarkable thyroid artery, and also the lingual artery are carefully related to the pointer of the greater horn. The guideline of the higher horn is a advantageous landmark in locating these arteries during cervical surgery. The carotid bifurcation is located inferior and also posterior to the tip of the higher horn. Also, the origin of the superior thyroid artery which is the an initial branch that the inner carotid artery lies listed below the level that the better horn. The lingual artery is one of the closely related structures to the hyoid, and it branches turn off the external carotid artery over the level that the greater horn.<6>

The Hyoid and its relation to Nerves

The hypoglossal and also the superior laryngeal nerve are closely related come the guideline of the better horn of the hyoid. The pointer of the greater horn aids the operated doctor in locating these nerves throughout cervical surgery. The hypoglossal nerve lies superiorly to the tip of the better horn of the hyoid. The remarkable laryngeal nerve divides into its external and internal branches as it passes behind the better horn, v its external branch being deeper 보다 the interior one.<6>

The Hyoid and also Obstructive Sleep Apnea Syndrome

Obstructive sleep apnea is a chronic sleep-related breath disorder. It is finest described by repeated narrowing and obstruction of the pharyngeal airway throughout sleep.<7> This problem is led to by pharyngeal collapsibility, which is due to the ns of wakefulness stimulus and changes in the neuromuscular control. Numerous factors add to the pharyngeal collapsibility; the hyoid position is among these factors. One imbalance in between the suprahyoid and infrahyoid muscles may lead to modification in the place of the hyoid, thus affecting the airway patency and causing more pharyngeal collapsibility.<8> The clinical manifestations encompass non-refreshing sleep, daytime sleepiness, fatigue, nocturia, irritability and also morning headache. If left unmanaged, it might lead to numerous complications, consisting of cardiovascular diseases, cognitive impairment, and decreased productivity and also concentration, i m sorry may lead to road traffic accidents.<7> The treatment of selection is the nasal consistent positive airway pressure; if unsuccessful, other choices include dental devices, positional therapy,<9> upper airway surgical procedure such together genioglossus advancement,<10> hyoidothyroidopexy (hyoid suspension),<11> hyoid myotomy and sliding genioplasty.<10>


Clinical Significance

Hyoid Bone Insertion Tendinitis

Hyoid bone insertion tendinitis is additionally known as hyoid bone syndrome. Patients define it together neck ache that increases with swallowing and movement the the neck. The pain is characteristically either dull or sharp, radiating come the temporal area, posterior pharyngeal wall, sternocleidomastoid muscle, ear, and supraclavicular region. Top top examination, tenderness end the greater horn that the hyoid is noted upon palpation. The problem is diagnosed greatly by history and physical examination. Imaging might be used to exclude, the various other differential diagnoses. Clinical therapy is the initial treatment of choice. It contains topical and also systemic non-steroidal anti-inflammatory medications, neighborhood anesthetics and also steroid injections. If medical therapy fails, then surgical treatment is the following consideration.<12>

Calcified Stylohyoid Ligament and also Eagle Syndrome


There room two types of Eagle syndrome. The very first type is the classic Eagle syndrome or the standard styloid syndrome, normally seen after ~ tonsillectomy together pharyngodynia uncovered in the tonsillar fossa, occasionally connected with odynophagia, dysphagia, international body sensation, hypersalivation, and seldom, short-term voice changes. Every one of these symptoms show up when the tightened tonsillectomy scar organization moves follow me the pointer of one elongated styloid process through practical movements.

Other Issues

Forensic Anatomy of the Hyoid

The forensic profile of the hyoid regarded forensic anthropology primarily consists of estimation that age and determination that sex. Blend of the hyoid is especially advantageous to predict period in adulthood. The bone thickness of the hyoid is a valuable predictor the both age and sex <3>. However, that is worth noting that the literary works reports a wide selection of variability in the degree and also timing of blend of the higher horns through the body of the hyoid. Making use of discriminant role analysis, miscellaneous metric dimensions of the hyoid are uncovered to be useful in identify the sex of the bone.<17>

Forensic definition of Hyoid Fracture

Trauma to the hyoid and laryngeal cartilages (thyroid cartilage and cricoid cartilage), is one of the significant signs of manual strangulation or throttling discovered during a forensic autopsy. Fractures the the hyoid-laryngeal complex are present in cases of death due come a constricting force about the neck. Forensic pathologists have actually intensively learned traumatic lesions the the hyoid-laryngeal facility in strangulation, including manual strangulation and ligature strangulation, and hanging. Other develops of dull force impact to the neck can additionally cause fracture that the hyoid.

The damage commonly affects the better horns or the region between the body of the hyoid and the horns. Injuries are greatly in the type of upright or oblique fractures. Displacements that the fracture segment are additionally observed. Bilateral fractures the the hyoid and double fractures of among the greater horns are not uncommon.<18> The frequency of a fractured hyoid is an ext in instances of strangulation in comparison to cases of hanging. However, a hyoid fracture is existing in only about a 3rd of all homicides indigenous strangulation.<19> Therefore, that merits noting that an undamaged hyoid walk not always rule out strangulation as the underlying cause of death. The hyoid is fractured more generally in the older victim of strangulation and is much less likely to happen in younger victim of strangulation in the age group 20 to 40.

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<19> The distinctions in the age-related frequency of hyoid fracture room dependent top top the level of ankylosis the the hyoid the progresses through age. The mobility in the region of the junction in between the higher horns and the human body of the hyoid have to not it is in mistaken for a fracture.