Subacute lymphocytic thyroiditis or silent thyroiditis is a thyroid inflammatory condition.
Usually characterised by recent onset of symptoms and there is usually an absence of thyroidal pain or tenderness. On examination there can be a normal to modestly enlarged and fi...
Subclavius posticus is an accessory muscle in the root of the neck, lying between the subclavius muscle and the inferior belly of omohyoid. It has an incidence of ~ 7.5% 2,4.
origin: first costal cartilage
insertion: superior margin of scapula
nerve supply: nerve to subclavius or sup...
Subconjunctival fat prolapse is an acquired herniation of intraconal fat due to the weakening of the Tenon capsule by normal aging, surgery, or trauma. It presents clinically with a fat-containing epibulbar mass in the lateral canthal area.
Subconjunctival fat prolapse occurs mai...
Subgaleal haematoma describes scalp bleeding in the potential space between the periosteum and the galea aponeurosis.
It most commonly occurs after vacuum assisted delivery, but may also be seen following head trauma. In patients with intracranial haemorrhage or skull fractures, the incidence o...
The subglottis is the anatomical region caudal to the true vocal cords, and is a subsite of the larynx.
The inferior arcuate line of the vocal cord marks the cranial border whilst the lower margin of the cricoid cartilage marks the caudal border of the subglottis 1. The inferior arcuate line is...
The sublingual glands are salivary glands that lie in the floor of the mouth anterior to the submandibullar glands. They secrete predominantly mucous saliva that is drained by a collection of 8-20 excretory ducts collectively termed the duct of Rivinus. The largest of these ducts, the major subl...
The sublingual space is one of the suprahyoid deep spaces of the head and neck.
It is like an inverted V with its apex pointing anteriorly and is located between:
tongue musculature superiorly
and the anterior one-third of the mylohyoid muscle inferolaterally which separates it...
The submandibular duct (also known as Wharton's duct) allows the passage of saliva from the submandibular gland to the sublingual papilla located anteriorly.
The duct extends anteriorly from the submandibular gland superior to the lingual nerve and submandibular ganglion curving over the poster...
The submandibular ganglion is one of four parasympathetic ganglia of the head and neck. It receives parasympathetic fibres from the facial nerve.
small ganglion suspended from the undersurface of the lingual nerve
inferior to submandibular duct sitting on the hyoglossus muscle
The submandibular glands are paired salivary glands located behind and below the ramus of the mandible in the submandibular triangle. They secrete mixed serous and mucous saliva that is excreted into the oral cavity via the submandibular duct that connects the gland to the floor of the mouth.
The submandibular space is a U-shaped compartment of the suprahyoid neck.
The superficial layer of the deep cervical fascia encloses the submandibular space.
medially: anterior belly of digastric muscles (separating it from the submental sp...
The submental space lies in the midline below the chin, medially to the U-shaped submandibular space with which it freely communicates.
superiorly: mylohyoid muscle
inferiorly: superficial layer of the deep cervical fascia
laterally: anterior bellies of the digastr...
The submental triangle is the single midline triangle, part of the anterior triangle of the neck. The triangles of the neck are surgically focussed, first described from early dissection-based anatomical studies which predated cross-sectional anatomical description based on imaging (see deep spa...
The suboccipital muscle group contains four paired muscles, three of which pairs belong to the suboccipital triangle. These muscles all lie below the occipital bone and are responsible for postural support of the head, as well as extension, lateral flexion and rotation. As these muscles are smal...
Subperiosteal abscess of the mastoid is one of the more frequent complications of acute otomastoiditis and results in coalescent mastoiditis extending through the external cortex of the mastoid sinus. This can occur in any direction:
postauricular: common as the bone is particularly thin ("Mace...
Subperiosteal abscess of the orbit occurs as a complication of acute sinusitis.
Patients can present with pain, visual disturbance, proptosis and/or chemosis.
Bacteria can extend via neurovascular foramina or bony dehiscences. More commonly occurs from ethmoid...
Substernal goitre is a goitre (enlarged thyroid gland) with intrathoracic extension.
It remains unclear which goitres are to be termed substernal, but a recently proposed definition is a goitre that requires mediastinal exploration and dissection for complete removal or an intrathoracic compone...
Sulcal artery syndrome is a rare cause of spinal cord infarction involving the territory of one of the sulcal arteries, which are penetrating branches of the anterior spinal artery, each vessel supplying either left or right side of the cord, but not both. The result is an incomplete Brown-Séqua...
The superficial temporal artery is one of two terminal branches of the external carotid artery. It arises in the parotid gland and runs between the deep and superficial lobes, over the zygomatic process before terminating in three branches - parietal, frontal and transverse facial - to supply pa...
The superficial temporal vein arises in a plexus on the side and vertex of the skull and, in the substance of the parotid gland, joins with the maxillary vein to form the retromandibular vein.
The superficial temporal vein originates from a venous plexus on the side and vertex of...
Superior labial artery (old name: superior coronary artery) is one of the facial branches of the facial artery. It is bigger and more serpiginous than the inferior labial artery. It supplies the upper lip, including its labial glands, mucous membranes and muscles.
origin: facial branch...
The superior laryngeal artery accompanies the internal laryngeal branch of the superior laryngeal nerve, beneath the thyrohyoid muscle.
It pierces the thyrohyoid membrane, and supplies the muscles, mucous membrane, and glands of the larynx, anastomosing with the branch from the opposite side.
The superior longitudinal muscle of the tongue is one of the 4 intrinsic muscles of the tongue which alters the shape of the tongue mass, being entirely confined to the tongue without an attachment outside the tongue (like the extrinsic muscles of the tongue).
The muscles fibres ...
The superior nasal concha is one of the conchae in the nose and refers to a bony projection on the posterior surface of the labyrinth of ethmoid.
The superior oblique muscle is one of the 6 extra-ocular muscles that control eye movements. It abducts, depresses and internally rotates the eye.
innervation: trochlear nerve (CN IV)
origin: lesser wing of Sphenoid bone and is outside of Annulus of Zinn located supero-medially.
The superior ophthalmic vein (SOV) is a prominent vein of the orbit that is seen on CT and may be enlarged or tortuous in various disease entities.
The vein forms at the confluence of several veins within the superior orbit above the medial palpebral ligament: the angular, suprat...
The superior orbital fissure is the communication between the cavernous sinus and the apex of the orbit. It is straddled by the tendinous ring which is the common origin of the four rectus muscles (extraocular muscles).
medial: body of sphenoid
superior: lesser wing ...
The superior pharyngeal constrictor muscle is one of the pharyngeal constrictor muscles. Its primary action is constriction of the pharynx (in coordination with the middle pharyngeal constrictor and the inferior pharyngeal constrictor muscles) to deliver a bolus of food into the oesophagus.
Superior rectus muscle is one of the 6 extra-ocular muscles that control eye movements.
innervation: superior branch of the oculomotor nerve (CN III)
origin: Annulus of Zinn (tendinous ring)
insertion: globe (anterior, superior surface)
primary function: one of two ocular elevators
Superior semicircular canal dehiscence syndrome (SCDS) is a recently described inner ear abnormality, where a clinical disequilibrium phenomenon is associated with the absence of the bony covering of the superior semicircular canal (SSC).
Notably, this CT finding has also been described in ~10%...
The superior thoracic aperture, also known as the thoracic inlet or outlet, connects the root of the neck with the thorax.
The superior thoracic aperture is kidney-shaped and lies in an oblique transverse plane, tilted anteroinferiorly to posterosuperiorly.
The superior thyroid artery is a branch of the external carotid artery and supplies the larynx and thyroid gland.
origin: branch of the external carotid artery at the level of the hyoid bone
superior laryngeal artery
Supernumerary teeth (hyperdontia) are additional teeth that are in addition to the normal number of either primary or permanent teeth.
The term supplemental tooth may be used when the supernumerary tooth resembles its associated normal tooth and the term peridens may be used for an...
The supraclavicular lymph nodes are a paired group of lymph nodes located on either side in the hollow of clavicle close to the sternoclavicular joint. It is the final common pathway of the lymphatic system as it joins the central venous system. They oversee transport of lymph from the thoracic ...
The supraclavicular nerves are three cutaneous nerves that emerge as a common trunk from the cervical plexus before branching to innervate the skin over the upper chest and shoulders.
The supraclavicular nerves arise from the ventral rami of C3 and C4 spinal nerves, alth...
The supraclavicular triangle is one of the paired triangles in the posterior triangle of the neck. The triangles of the neck are surgically focussed, first described from early dissection-based anatomical studies which predated cross-sectional anatomical description based on imaging (see deep sp...
The suprahyoid muscles are a group of muscles in the neck, named because of their position to the hyoid bone:
anterior suprahyoid muscles
anterior bellies of digastric muscle
posterior suprahyoid muscles
posterior bellies of digastric muscle
The supraorbital artery is a branch of the ophthalmic artery supplying part of the orbit and face.
The supraorbital artery originates from the ophthalmic artery, upon branching it lies medial to the optic nerve.
The supraorbital artery courses superiorly and med...
The supraorbital foramen or notch is the small opening at the central edge of the superior orbital margin in the frontal bone just below the superciliary arches that transmits the supra-orbital nerve, artery and vein.
It is lateral to the supratrochlear foramen, where the supratrochlear nerve, ...
The supraorbital nerve is the lateral and larger of the two branches of the frontal nerve, a branch of ophthalmic division of the trigeminal nerve. As it courses through the superior aspect of the extraconal space of the orbit it exits the orbit through the supraorbital notch to supply the conju...
The supraorbital ridge, also known as the supraorbital margin or superciliary arch is the superior margin of the bony orbit. Part of the frontal bone, the supraorbital ridge contains the supraorbital foramen (or notch). The corrugator supercilii muscles arise from the medial end of the supraorbi...
The suprascapular artery is 1 of the 4 branches of the thyrocervical trunk (off the first part of the subclavian artery).
It traverses inferiorly and laterally in the lower anterior neck superficial to the anterior scalene muscle and phrenic nerve before crossing the third part of the subclavia...
The suprasternal space (of Burns) is a space of the inferior neck.
Inferior to the hyoid bone, the superficial or investing layer of the deep cervical fascia divides into anterior and posterior leafs to attach to the respective borders of the suprasternal (jugular) notch, forming...
The supratrochlear artery, also known as the frontal artery, originates from the ophthalmic artery as one of its terminal branches.
After arising from the ophthalmic artery, it pierces the orbital septum and courses in the superior and medial aspect of the orbit, medial to the su...
The supratrochlear foramen is the small opening at the medial edge of the superior orbital margin in the frontal bone that transmitts the supratrochlear nerve, artery and vein. When incomplete, it forms a notch. It is variably present, and when absent the neurovascular bundle will simple exit th...
The supratrochlear nerve is the medial and smaller of the two branches of the frontal nerve, a branch of ophthalmic division of the trigeminal nerve. As it courses through the superomedial aspect of the extraconal space of the orbit, it passes over the trochlear and exits the orbit under the sup...
Sutural diastasis is an abnormal widening of the skull sutures. It may be physiological in a neonate during a growth spurt.
In non-traumatic scenarios accelerated growth of the sutural connective tissue without concurrent ossification is the underlying pathology.
There are many sutures of the skull, which are where skull bones meet. In general, sutures don't fuse until brain growth is complete, therefore allowing the skull to increase in size with the developing brain.
Sutures are fibrous joints with the periosteum externally and outer la...
Syphilis is the result of infection with the gram negative spirochete Treponema pallidum, subspecies pallidum. It results in a heterogeneous spectrum of disease with many systems that can potentially be involved, which are discussed separately.
Despite the discovery of penicillin...
Tc-99m pertechnetate is one of the technetium radiopharmaceuticals used in imaging of thyroid, colon, bladder and stomach.
photon energy: 140 keV
biological half-life: 6 hours
normal distribution: stomach, thyroid, salivary glands, (testicles)
Tc-99m sestamibi is one of the technetium radiopharmaceuticals.
photon energy: 140 KeV
physical half life: 6 hours
normal distribution: thyroid, parathyroid, heart
target organ: colon, kidneys, bladder, gallbladder
Uses, doses and timings
Teeth can be both primary and secondary, with the eruption of permanent teeth occurring over a long period between the ages of 6 and 24.
There are twenty deciduous (primary) teeth in young children, with ten per jaw and five in each quadrant, which consist of (distal to mesial):...
Telecanthus represents increased intercanthal distance. It is often used interchangeably with hypertelorism, referring to increased distance between the eye.
Causes and associations
trauma: naso-orbito-ethmoidal (NOE) fractures
sinus and orbital tumours
The temporal bone is situated on the sides and the base of the cranium and lateral to the temporal lobe of the cerebrum. The temporal bone is one of the most important calvarial and skull base bones. The temporal bone is very complex and consists of five parts:
A helpful mnemonic for remembering the complications of temporal bone fractures that may require early intervention is:
C: carotid artery injury
L: leakage of CSF
O: other intracranial complications, e.g. hematoma
N: nerve injury leading to complete facial paralysis
Temporal bone fractures are usually a sequela of blunt head injury, generally from severe trauma. Associated intracranial injuries, such as extra-axial haemorrhage, shear (or diffuse axonal) injury, and cerebral contusion are common. Early identification of temporal bone trauma is essential to m...
The temporal fossa is located in the temporal region and communicates inferiorly with infratemporal fossa deep to the zygomatic arch.
The temporal fossa is bounded by a few anatomical landmarks, anteriorly the frontal process of the zygomatic bone, superiorly and posteriorly the...
The temporalis muscle is one of the muscles of mastication. It is responsible for both closing the mouth and retraction (posterior fibres).
origin: temporal fossa between the infratemporal crest and inferior temporal line
insertion: coronoid process and ramus of mandible
The temporomandibular joint (TMJ) is an atypical synovial joint located between the condylar process of the mandible and the mandibular fossa and articular eminence of the temporal bone. It is divided into superior discotemporal space and inferior discomandibular space by the TMJ disc (or menisc...
The axiolateral temporomandibular view allows for visualisation of the articular tubercle, mandibular condyle and fossa and is thus useful to identify structural changes and displaced fractures, as well as assess excursion and joint spaces.
Clinical indications include trauma, the presence of ...
The temporomandibular joint (TMJ) disc (or meniscus) is made of fibrocartilage and divides the joint into two compartments.
The disc is composed of fibrocartilage, with crimped collagen, thought to better absorb impacts. It has a biconcave shape with a thicker periphery attached...
Temporomandibular joint dislocation represents the condyle of the mandible being abnormally displaced, with a loss of the normal articulation with the glenoid fossa.
Dislocations of the temporomandibular joint (TMJ) are common and occur in as many as 7% of the entire population, a...
Temporomandibular joint (TMJ) dysfunction is characterised by an abnormal relationship between the disc and the adjacent articular surfaces (condyle below with mandibular fossa and articular eminence above).
TMJ dysfunction is far more common in women (F:M 8:1).
Temporomandibular joint (TMJ) effusions are unusual in asymptomatic patients, and thus should trigger a careful search for underlying pathology. It usually precedes osteoarthritis of the TMJ. Effusions are seen in:
rheumatoid arthritis (RA)
Temporomandibular joint (TMJ) inflammation may occur as a result of an inflammatory arthropathy or secondary to TMJ dysfunction. Since the TMJ is a synovial joint, it is susceptible to inflammatory arthropathies that affect other joints.
rheumatoid arthritis (RA) : is by far the most common
Temporomandibular joint (TMJ) pathology encompasses three main entities:
temporomandibular joint dysfunction: relating to abnormal TMJ disc relationship to condyle and temporal bone, which can lead to osteoarthritis.
temporomandibular joint inflammation
temporomandibular joint trauma
The temporomandibular joint (TMJ) can be affected by trauma in a number of ways:
condylar process fractures
temporomandibular joint dislocation
fracture of the mandibular fossa
The temporozygomatic suture (or zygomaticotemporal suture) is between the zygomatic process of the temporal bone and the temporal process of the zygomatic bone.
It can mimic a zygoma fracture.
The tendinous ring, also known as the annulus of Zinn, is the common origin of the four rectus muscles (extraocular muscles).
The tendinous ring straddles the superior orbital fissure and through it (from superior to inferior) pass:
superior division of the oculomotor nerve (CN III)
The Tenon capsule, also known as fascia bulbi or bulbar sheath, functions as an extraocular muscle pulley. It also provides a socket which separates the globe from the surrounding fat and allows free movement. It merges posteriorly with the dural sheath of the optic nerve and extends anteriorly ...
The tensor tympani is a short muscle in the middle ear that arises from the superior surface of the cartilaginous part of the Eustachian tube, the greater wing of the sphenoid, and the petrous part of the temporal bone. It passes across the tympanic cavity and inserts into the upper end of the h...
The tensor veli palatini is one of the 5 paired muscles of the soft palate. It is triangular in shape and it's tendon wraps around the pulley of pterygoid hamulus to alter the shape of the soft palate.
origin: it has 3 sites of origin:
scaphoid fossa of the medial pterygoid plate
The tentorial angle is measured between a line connecting the nasion with the tuberculum sellae and the the angle of the straight sinus. Normally it should measure between 27° and 52°.
Abnormalities of the posterior fossa / base of skull can alter this. For example this angle is elevated in ach...
The tentorial nerve is the first branch of the ophthalmic division of the trigeminal nerve (CN Va) which is the dominate dural nerve supplying most of the supratentorial dura. It specifically supplies the falx, calvarial dura and superior surface of the tentorium.
Terson syndrome refers to vitreous haemorrhage associated with subarachnoid haemorrhage, however some authors include retinal haemorrhage as well. The syndrome is a poor prognostic marker in patients with subarachnoid haemorrhage.
Terson syndrome has been reported to occur in 13-5...
Third branchial cleft cysts are a very rare type of branchial cleft cysts. Although they are extremely rare, they remain the second most common congenital lesion of the posterior cervical region after cervical lymphatic malformations or cystic hygromas 3.
By definition, a t...
The thumb sign in epiglottitis is a manifestation of an oedematous and enlarged epiglottis which is seen on lateral soft-tissue radiograph of the neck, and it suggests a diagnosis of acute infectious epiglottitis. This is the radiographic corollary of the omega sign 1-3.
Thumb sign is...
Thymic cysts are cysts that occur within, or arise from, the thymus.
Thymic cysts are uncommon lesions and are estimated to account for approximately 1-3% of all anterior mediastinal masses 4. Approximately 50% of congenital thymic cysts are incidentally discovered during the firs...
The thyrocervical trunk is one of the 3 branches of the first part of the subclavian artery and gives of numerous branches to supply viscera of the neck, the brachial plexus, neck muscles and the scapular anastomosis.
The trunk arises lateral to the vertebral artery from the anterosuperior wall...
The thyroglossal duct is an epithelium-lined connection between the foramen caecum and the thyroid that develops during the descent of the thyroid. It usually involutes in the 8th-10th week of gestation.
The thyroglossal duct arises from foramen caecum located at the junction of...
Thyroglossal duct cysts (TGDC) are the most common congenital neck cyst. They are typically located in the midline and are the most common midline neck mass in young patients. They can be diagnosed with multiple imaging modalities, including ultrasound, CT, and MRI.
The thyrohyoid muscle is an infrahyoid muscle of the neck that is innervated by the ventral ramus of C1. The primary function of the thyrohyoid muscle is to depress and fix the hyoid bone and larynx though it may also raise the larynx when the hyoid bone is fixed.
origin: oblique line ...
Thyroid acropachy is an unusual presentation of autoimmune thyroid disease, (~1% of patients with Graves disease). It can occur in hyperthyroid, euthyroid, hypothyroid, or even post-treatment patients. It is almost always associated with thyroid ophthalmopathy.
The majority of pa...
Successful treatment of thyroid malignancies highly depends on accurate preoperative staging.
Ultrasound and ultrasound guided FNA or core biopsy remain the investigation of choice for diagnosing primary thyroid malignancies; CT and MRI are inferior to ultrasound for characterising thyroid nodu...
The thyroid cartilage is the largest of the cartilages of the larynx, with its superior pole sitting at the level of the C4 vertebrae.
The thyroid cartilage consists of two laminae that are fused anteriorly in the median plane to form the laryngeal prominence. Each laminae posses...
The thyroid gland is an endocrine organ in the neck which is completely enveloped by pretracheal fascia (middle-layer of the deep cervical fascia) and lies in the visceral space.
The thyroid extends from C5 to T1 and lies anterior to the thyroid and cricoid cartilages of the lar...
TIRADS is a risk stratification system for classifying thyroid lesions and was recently recognized in an American College of Radiology (ACR) white paper 1. Its use is being advocated similar to BIRADS category for breast lesions.
In 2017, a white paper 2 was released by the ACR committee on th...
Thyroid inferno refers to the colour Doppler appearance of the thyroid gland in active Graves disease (inclusive of variants such as Marine Lenhart syndrome), and consists of multiple small areas of colour flow seen diffusely throughout the gland representing increased vascularity and arterioven...
A number of inflammatory conditions can affect the thyroid gland, which are commonly described as thyroiditides:
acute suppurative thyroiditis (AST)
subacute lymphocytic thyroiditis: silent thyroiditis or painless subacute thyroiditis
Thyroid lymphoma is rare, accounting for a minority of both thyroid malignancies and lymphoma in general.
The thyroid may be affected primarily or secondary to lymphoma elsewhere. This article is concerned with primary thyroid lymphoma.
Thyroid lymphoma accounts for <5% of thyr...
Thyroid malignancies are most commonly primary thyroid cancers but can rarely be metastatic deposits.
Thyroid malignancies can be categorised into the following key subtypes:
primary thyroid cancers
papillary thyroid carcinoma: 60-80% of carcinomas
A mnemonic for thyroidal mass differential diagnosis is:
C: colloid cyst
H: hyperplasia (parathyroid gland)
Thyroid scan (thyroid scintigraphy) is a nuclear medicine examination used to evaluate thyroid tissue.
functional status of a thyroid nodule
thyrotoxicosis: differential diagnosis
whole body scan for distant metastases
estimation of local residual thyro...