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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, located in the midline that the neck anteriorly at the base the the mandible and posteriorly in ~ the 4th cervical vertebra. Its anatomical position is simply superior come the thyroid cartilage. That is closely linked with an extended tendon-muscular facility but not particularly interconnected to any surrounding bones and also hence is considered by numerous anatomists and also anthropologists to be an unconventional bone. That is anchored in the anterior triangle that the neck by muscle 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 dubbed as an unconventional bone, the hyoid being a component of the hyoid-larynx complex is without doubt a bone the clinical and also forensic significance.


Structure and also Function

The hyoid consists of a body, two greater horns, and also two lesser horns.<1> The body creates the main quadrilateral-shaped broad segment that the hyoid. The greater horns space larger and longer than the lesser horns of the hyoid. The better horns and also lesser horns are likewise known as cornu majus and cornu minus, respectively. The body and also the better horns show up to provide the hyoid that is U-shape with the higher horns forming the four of the "U" ~ above either side of the body. The greater and lesser horns normally unite to the body of the hyoid via fibrous tissue or a true joint.<2> As period progresses, there is a physiological progression of ankylosis that the joints connecting the greater and also lesser horns v the body of the hyoid.  

The hyoid takes part in all possible functional plot of the orofacial complex. It preserves the patency of the airway in between the oropharynx over and tracheal ring below. It also connects to the larynx and hence theatre a role in phonation. Other functions encompass tongue movement, mastication, swallowing, avoidance of regurgitation, and also even respiration.<1><3> Furthermore, the hyoid maintains the posture of the head, due to the complex connection that presumes between the mandible and the cervical spine.<1>


Embryology

The 2nd pharyngeal arch creates the lesser horn (cornu) and also the top body of the hyoid, while the better horn (cornu) and the lower part of the body derive indigenous the third pharyngeal arch. This embryonic development of the hyoid continues to be controversial.<1> The ossification of the higher horns occurs towards the end of the normal gestational period of the fetus; this is adhered to by the ossification the the body of the hyoid shortly after birth. Eventually, ossification the the lesser horns occurs throughout the first or second year after birth. Later in adulthood, usually the horns fuse through the body, but this might not take place in all individuals. The hyoid is located anterior to the second and third cervical vertebra during infancy, and also ultimately in adulthood, that descends come the level that the fourth and fifth cervical vertebra. The descent takes place simultaneously through the various other functionally appropriate structures including the epiglottis and also the larynx.<3>


Muscles

The hyoid attributes as one anchor for the suprahyoid muscles (digastric, stylohyoid, mylohyoid and geniohyoid) and also the infrahyoid muscles (sternohyoid, sternothyroid, omohyoid, and also thyrohyoid).<2> The stylohyoid ligament suspends the hyoid from 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 v the thyrohyoid membrane. Additionally, the hyoid is attached come the cervical spine posteriorly via the cervical fascia.<1>

Suprahyoid Muscles

The suprahyoid muscle are 4 in number on either side of the anterior midline above the level of the hyoid (Media Image, Table 1). They affix the hyoid come the mandible, tongue, and skull. The digastric muscle has actually two bellies, posterior and anterior. The anterior ship originates from the digastric fossa the the mandible, while the posterior ship originates native the mastoid notch. Both the digastric bellies insert to the intermediate tendon that the digastric muscle i m sorry is attached come the hyoid. The stylohyoid muscle originates from the temporal styloid process; that is a thin and long muscle the lies parallel come the posterior belly of the digastric. The mylohyoid muscle originates native the mylohyoid heat of the mandible; that is a thin muscle that upholds and also makes increase the floor that the mouth while likewise creating a sling inferior to the tongue. The geniohyoid muscle is a narrow and short muscle that originates indigenous the internal mental spine the the symphysis menti. The stylohyoid, mylohyoid, and also geniohyoid insert on the human body of the hyoid.<1>

Infrahyoid Muscles

The infrahyoid muscles are 4 pairs that muscles situated in the anterior component of the neck (Media Image, Table 2). They are found between the hyoid above and the shoulder girdle below. The sternohyoid muscle mostly originates native the back of the manubrium and 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 ~ above the oblique heat of the thyroid cartilage. The omohyoid muscle has a remarkable belly and also an inferior belly. The remarkable belly that the omohyoid occurs from the intermediate tendon the the omohyoid and also inserts top top the hyoid. The inferior belly of the omohyoid originates indigenous the scapular premium border and also inserts come the intermediate tendon the the omohyoid. The thyrohyoid muscle originates native the oblique heat of the thyroid cartilage and also inserts in ~ the inferior aspect of the human body of the hyoid and also the greater cornu.<1><4>

Other Muscles concerned the Hyoid

The hyoglossus and the center pharyngeal constrictor originate native the hyoid. These muscles carry out not type the team as mentioned above of muscles regarded the hyoid.

Elevation that the Hyoid

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

Depression of the Hyoid

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


Physiologic Variants

The hyoid reflects a wide variety of anatomical variations, most likely owing to the asymmetry that the greater and lesser horns. Therefore, the hyoid is taken into consideration one the the many polymorphic parts of the human body. The commonest sports of the hyoid takes place in the process of ankylosis the the joints in between the horns (greater and also lesser horns) and the body of the hyoid. Ethnicity, sex, age, height, and weight the the subject add to the morphological variations. This variations can happen unilaterally, bilaterally, and multiple sports can occur in the exact same individual.<2> Surprisingly, the absence of the hyoid has actually been reported also in a masculine neonate that was additionally a teratoma case, had a mandibular cleft, and suffered from respiratory tract distress.<5> this anomalies correlate to some clinical problems such together micrognathia, Pierre Robin sequence, and also cleft lip and also palate. Symptoms caused by these anomalies include dysphagia, neck movement limitations and foreign human body sensation in the throat.<2>


Surgical Considerations

The Hyoid and its relation to Blood Vessels

The guideline of the better horn of the hyoid is a far-ranging landmark for cervical surgical treatment in the mid-neck region. The carotid bifurcation, the premium thyroid artery, and also the lingual artery are very closely related to the guideline of the higher horn. The reminder of the greater horn is a helpful landmark in locating these arteries throughout cervical surgery. The carotid bifurcation is situated inferior and posterior come the reminder of the greater horn. Also, the origin of the superior thyroid artery which is the an initial branch that the inner carotid artery lies below the level that the higher 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 the the better horn.<6>

The Hyoid and also its relation to Nerves

The hypoglossal and also the superior laryngeal nerve are very closely related come the tip of the higher horn of the hyoid. The pointer of the greater horn aids the surgeon in locating these nerves during cervical surgery. The hypoglossal nerve lies superiorly come the guideline of the better horn that the hyoid. The exceptional laryngeal nerve divides right into its external and also internal branches as it overcome behind the greater horn, v its external branch being deeper than the inner one.<6>

The Hyoid and Obstructive Sleep Apnea Syndrome

Obstructive sleep apnea is a chronic sleep-related breath disorder. The is best described by recurring narrowing and obstruction that the pharyngeal airway during sleep.<7> This condition is resulted in by pharyngeal collapsibility, i beg your pardon is because of the ns of wakefulness stimulus and also changes in the neuromuscular control. Numerous factors add to the pharyngeal collapsibility; the hyoid position is one of these factors. An imbalance in between the suprahyoid and also infrahyoid muscles might lead to change in the place of the hyoid, therefore affecting the airway patency and also causing more pharyngeal collapsibility.<8> The clinical manifestations incorporate non-refreshing sleep, daytime sleepiness, fatigue, nocturia, irritability and also morning headache. If left unmanaged, it may lead to plenty of complications, including cardiovascular diseases, cognitive impairment, and also decreased productivity and also concentration, i m sorry may lead to road website traffic accidents.<7> The therapy of selection is the nasal consistent positive airway pressure; if unsuccessful, other options include oral devices, positional therapy,<9> top airway surgical treatment such as genioglossus advancement,<10> hyoidothyroidopexy (hyoid suspension),<11> hyoid myotomy and sliding genioplasty.<10>


Clinical Significance

Hyoid Bone Insertion Tendinitis

Hyoid bone insertion tendinitis is likewise known as hyoid bone syndrome. Patients define it together neck ache that rises with swallowing and also movement that the neck. The ache is characteristically one of two people dull or sharp, radiating come the temporal area, posterior pharyngeal wall, sternocleidomastoid muscle, ear, and also supraclavicular region. On examination, tenderness over the higher horn that the hyoid is noted upon palpation. The problem is diagnosed greatly by background and physics examination. Imaging may be offered to to exclude, the various other differential diagnoses. Medical therapy is the initial therapy of choice. It has topical and also systemic non-steroidal anti-inflammatory medications, neighborhood anesthetics and also steroid injections. If clinical therapy fails, then surgery is the following consideration.<12>

Calcified Stylohyoid Ligament and also Eagle Syndrome


There are two varieties of Eagle syndrome. The an initial type is the classic Eagle syndrome or the standard styloid syndrome, normally seen ~ tonsillectomy as pharyngodynia discovered in the tonsillar fossa, occasionally connected with odynophagia, dysphagia, foreign body sensation, hypersalivation, and seldom, temporary voice changes. Every one of these symptoms show up when the tightened tonsillectomy scar tissue moves along the reminder of an elongated styloid procedure through useful movements.

Other Issues

Forensic Anatomy of the Hyoid

The forensic file of the hyoid concerned forensic anthropology primarily includes estimation that age and also determination the sex. Fusion of the hyoid is especially useful to predict age in adulthood. The bone thickness of the hyoid is a an useful predictor that both age and sex <3>. However, it is worth noting that the literature reports a wide range of variability in the degree and also timing of fusion of the better horns v the body of the hyoid. Utilizing discriminant role analysis, various metric dimensions of the hyoid are discovered to be beneficial in identify the sex of the bone.<17>

Forensic significance of Hyoid Fracture

Trauma to the hyoid and also laryngeal cartilages (thyroid cartilage and also cricoid cartilage), is among the far-reaching signs of hand-operated strangulation or throttling uncovered during a forensic autopsy. Fractures of the hyoid-laryngeal complicated are current in cases of death due to a constricting force roughly the neck. Forensic pathologists have intensively learned traumatic lesions the the hyoid-laryngeal complicated in strangulation, including manual strangulation and ligature strangulation, and also hanging. Other forms of blunt force affect to the neck can also cause fracture that the hyoid.

The damage typically affects the greater horns or the region between the body of the hyoid and also the horns. Injuries are mainly in the type of vertical or slope fractures. Displacements the the fracture segment are additionally observed. Bilateral fractures of the hyoid and dual fractures of one of the higher horns room not uncommon.<18> The frequency of a broken hyoid is more in instances of strangulation in compare to cases of hanging. However, a hyoid fracture is existing in only about a 3rd of every homicides indigenous strangulation.<19> Therefore, it merits noting that an intact hyoid go not constantly rule out strangulation together the underlying cause of death. The hyoid is broken more generally in the older victims of strangulation and is less likely to happen in younger victim of strangulation in the age group 20 come 40.

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<19> The distinctions in the age-related frequency of hyoid fracture space dependent ~ above the degree of ankylosis of the hyoid that progresses v age. The mobility in the an ar of the junction between the greater horns and the human body of the hyoid should not be mistaken for a fracture.