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


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Introduction

The hyoid bone (hyoid) is a small U-shaped (horseshoe-shaped) solitary bone, situated in the midline of the neck anteriorly at the base of the mandible and posteriorly at the fourth cervical vertebra. The anatomical place is just superior come the thyroid cartilage. The is closely linked with an extended tendon-muscular complicated but not particularly interconnected to any nearby bones and also hence is considered by many anatomists and anthropologists to it is in an unconventional bone. That is anchored in the anterior triangle that the neck by muscles from the larynx, pharynx, tongue, and the floor that the mouth. The name hyoid derives from the Greek word “hyodeides,” which means “shaped favor the letter Upsilon.” Although referred to as as an unconventional bone, the hyoid gift a component of the hyoid-larynx complex is undoubtedly a bone of clinical and forensic significance.


Structure and also Function

The hyoid consists of a body, two better horns, and also two lesser horns.<1> The body creates the central quadrilateral-shaped broad segment the the hyoid. The better horns are larger and longer than the lesser horns the the hyoid. The higher horns and lesser horns are also known as cornu majus and cornu minus, respectively. The body and the higher horns show up to give the hyoid that U-shape through the greater horns creating the limbs of the "U" top top either next 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 progression of ankylosis that the joints connecting the greater and lesser horns with the human body of the hyoid.  

The hyoid takes part in all possible functional actions of the orofacial complex. That preserves the patency of the airway between the oropharynx over and tracheal ring below. It also connects to the larynx and also hence dram a duty in phonation. Other functions include tongue movement, mastication, swallowing, avoidance of regurgitation, and also even respiration.<1><3> Furthermore, the hyoid maintains the attitude of the head, because of the complicated connection that presumes in between the mandible and the cervical spine.<1>


Embryology

The second pharyngeal arch forms the lesser horn (cornu) and also the top body of the hyoid, while the better horn (cornu) and also the lower part of the human body derive indigenous the third pharyngeal arch. This embryonic development of the hyoid stays controversial.<1> The ossification the the higher horns occurs toward the end of the normal gestational period of the fetus; this is adhered to by the ossification that the body of the hyoid quickly after birth. Eventually, ossification of the lesser horns occurs during the first or 2nd year after ~ birth. Later on in adulthood, typically the horns fuse v the body, yet this might not take place in every individuals. The hyoid is situated anterior come the second and third cervical vertebra throughout infancy, and ultimately in adulthood, it descends to the level that the fourth and fifth cervical vertebra. The descent takes location simultaneously v the other functionally relevant structures consisting of the epiglottis and the larynx.<3>


Muscles

The hyoid features as an anchor for the suprahyoid muscles (digastric, stylohyoid, mylohyoid and also geniohyoid) as well as the infrahyoid muscle (sternohyoid, sternothyroid, omohyoid, and also thyrohyoid).<2> The stylohyoid ligament suspends the hyoid from the temporal styloid process on one of two people side. It is restricted 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 ~ above either side of the anterior midline over the level of the hyoid (Media Image, Table 1). They affix the hyoid to the mandible, tongue, and skull. The digastric muscle has two bellies, posterior and also anterior. The anterior ship originates from the digastric fossa the the mandible, while the posterior belly originates native the mastoid notch. Both the digastric bellies insert come the intermediary tendon of the digastric muscle i beg your pardon is attached come the hyoid. The stylohyoid muscle originates native the temporal styloid process; the is a thin and long muscle that lies parallel come the posterior ship of the digastric. The mylohyoid muscle originates native the mylohyoid line of the mandible; it 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 the originates from the inner 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 four pairs that muscles located in the anterior component of the neck (Media Image, Table 2). They space found in between the hyoid above and the shoulder girdle below. The sternohyoid muscle generally originates from the back 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 inserts top top the oblique line of the thyroid cartilage. The omohyoid muscle has actually a remarkable belly and also an inferior belly. The exceptional belly that the omohyoid occurs from the intermediate tendon the the omohyoid and inserts top top the hyoid. The inferior belly of the omohyoid originates indigenous the scapular superior border and also inserts come the intermediary tendon that the omohyoid. The thyrohyoid muscle originates native the oblique heat of the thyroid cartilage and inserts in ~ the inferior element of the human body of the hyoid and also the greater cornu.<1><4>

Other Muscles pertained to the Hyoid

The hyoglossus and also the middle pharyngeal constrictor originate native the hyoid. This muscles carry out not kind the group as mentioned above of muscles concerned the hyoid.

Elevation that the Hyoid

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

Depression the the Hyoid

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


Physiologic Variants

The hyoid mirrors a wide range of anatomical variations, most likely owing come the asymmetry that the greater and lesser horns. Therefore, the hyoid is considered one the the most polymorphic components of the human body. The commonest sports of the hyoid takes location in the process of ankylosis that the joints between the horns (greater and also lesser horns) and the body the the hyoid. Ethnicity, sex, age, height, and weight that the subject add to the morphological variations. This variations can take place unilaterally, bilaterally, and also multiple sport can take place in the exact same individual.<2> Surprisingly, the lack of the hyoid has been reported too in a masculine neonate who was likewise a teratoma case, had a mandibular cleft, and also suffered from respiratory distress.<5> these anomalies correlate to part clinical problems such as micrognathia, Pierre Robin sequence, and cleft lip and palate. Symptoms brought about by these anomalies incorporate dysphagia, neck activity limitations and also foreign body sensation in the throat.<2>


Surgical Considerations

The Hyoid and its relationship to Blood Vessels

The reminder of the better horn the the hyoid is a far-ranging landmark for cervical surgical treatment in the mid-neck region. The carotid bifurcation, the premium thyroid artery, and the lingual artery are carefully related come the tip of the better horn. The tip of the better horn is a beneficial landmark in locating this arteries throughout cervical surgery. The carotid bifurcation is situated inferior and also posterior to the tip of the better horn. Also, the beginning of the premium thyroid artery i beg your pardon is the first branch that the internal carotid artery lies below the level that the greater horn. The lingual artery is one of the carefully related frameworks to the hyoid, and also it branches off the exterior carotid artery over the level of the greater horn.<6>

The Hyoid and its relationship to Nerves

The hypoglossal and also the exceptional laryngeal nerve are closely related come the reminder of the greater horn the the hyoid. The tip of the higher horn aids the surgeon in locating these nerves throughout cervical surgery. The hypoglossal nerve lies superiorly come the reminder of the better horn the the hyoid. The superior laryngeal nerve divides right into its external and also internal branches together it passes behind the better horn, with its outside branch being deeper than the inner one.<6>

The Hyoid and Obstructive Sleep Apnea Syndrome

Obstructive sleep apnea is a chronic sleep-related breathing disorder. It is finest described by recurring narrowing and obstruction the the pharyngeal airway during sleep.<7> This problem is led to by pharyngeal collapsibility, i m sorry is because of the ns of wakefulness stimulus and also changes in the neuromuscular control. Several factors add to the pharyngeal collapsibility; the hyoid position is among these factors. One imbalance in between the suprahyoid and also infrahyoid muscles might lead to alteration in the place of the hyoid, therefore affecting the airway patency and also causing much 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 countless complications, including cardiovascular diseases, cognitive impairment, and also decreased productivity and concentration, i m sorry may bring about road website traffic accidents.<7> The therapy of choice is the nasal continuous positive airway pressure; if unsuccessful, other options include dental devices, positional therapy,<9> upper airway surgery 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 pain that increases with swallowing and movement the the neck. The pains is characteristically either dull or sharp, radiating come the temporal area, posterior pharyngeal wall, sternocleidomastoid muscle, ear, and also supraclavicular region. Top top examination, tenderness over the greater horn the the hyoid is provided upon palpation. The condition is diagnosed largely by history and physics examination. Imaging may be offered to to exclude, the various other differential diagnoses. Medical therapy is the initial treatment of choice. It contains topical and also systemic non-steroidal anti-inflammatory medications, regional anesthetics and steroid injections. If clinical therapy fails, then surgical treatment is the next consideration.<12>

Calcified Stylohyoid Ligament and Eagle Syndrome


There space two varieties of Eagle syndrome. The first type is the standard Eagle syndrome or the classic styloid syndrome, commonly seen ~ tonsillectomy as pharyngodynia discovered in the tonsillar fossa, occasionally connected with odynophagia, dysphagia, international body sensation, hypersalivation, and seldom, short-lived voice changes. Every one of these symptoms appear when the tightened tonsillectomy scar organization moves follow me the pointer of an elongated styloid procedure through useful movements.

Other Issues

Forensic Anatomy the the Hyoid

The forensic file of the hyoid regarded forensic sociology primarily includes estimation the age and also determination of sex. Blend of the hyoid is especially useful to predict period in adulthood. The bone density of the hyoid is a an important predictor the both age and sex <3>. However, it is precious noting the the literature reports a wide variety of variability in the degree and also timing of combination of the better horns v the human body of the hyoid. Using discriminant role analysis, miscellaneous metric dimensions of the hyoid are found to be helpful in determining the sex of the bone.<17>

Forensic definition of Hyoid Fracture

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

The damage commonly affects the better horns or the region between the human body of the hyoid and also the horns. Injuries are mostly in the form of upright or oblique fractures. Displacements the the fracture segment are also observed. Bilateral fractures that the hyoid and dual fractures of among the higher horns are not uncommon.<18> The frequency of a fractured hyoid is more in instances of strangulation in to compare to situations of hanging. However, a hyoid fracture is current in only about a 3rd of all homicides from strangulation.<19> Therefore, it merits noting the an undamaged hyoid go not always rule out strangulation together the underlying reason of death. The hyoid is fractured more generally in the older victims of strangulation and also is less likely to happen in younger victim of strangulation in the period group 20 to 40.

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<19> The differences in the age-related frequency of hyoid fracture room dependent ~ above the degree of ankylosis the the hyoid that progresses v age. The mobility in the an ar of the junction between the higher horns and the body of the hyoid have to not it is in mistaken for a fracture.