The superior ophthalmic vein 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, supratrochle...
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 ...
Superior orbital fissure syndrome (SOFS) or Rochon–Duvigneaud syndrome is a rare complication of craniofacial trauma with an orbital fracture that extends to the superior orbital fissure that results in injury to the cranial nerves III, IV, V (ophthalmic branch of the trigeminal nerve) and VI as...
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 esophagus.
Superior rectus muscle is one of the six extraocular 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 an inner ear abnormality, where a clinical disequilibrium phenomenon is associated with the absence of the bony covering of the superior semicircular canal (SSCC).
Notably, this CT finding has also been described in ~10% of individuals w...
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
The superior thyroid vein, along with the middle and inferior thyroid veins, drains a venous plexus on the anterior surface of the thyroid gland 1.
The paired vein shares a course with the superior thyroid artery 2. The superior thyroid veins also receive tributaries from the sup...
Supernumerary teeth (hyperdontia) are 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 ectopicall...
The suprabullar cells are a subset of variably present frontal recess cells located above the ethmoid bulla.
They are nearly identical to frontal bullar cells. The distinguishing features with the latter are that the suprabullar cells are located entirely below the frontal ostium a...
The suprabullar recess is a potential opening (cleft) between the bulla lamella and skull base located along the posterior margin of the frontal recess with which it may communicate directly. It is present when the bulla lamella is incomplete superiorly.
The term sinus lateralis is sometimes u...
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 the transport of lymph from the thora...
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 focused, first described from early dissection-based anatomical studies which predated cross-sectional anatomical description based on imaging (see deep spa...
The supraglottis is an anatomic subsite of the larynx, located superior to the glottis.
The supraglottic larynx includes, from superior to inferior, the epiglottis (including both lingual and laryngeal surfaces), the laryngeal aspect of the aryepiglottic folds, false vocal cords,...
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...
Supraorbital air cells are an anatomical variant of the paranasal sinuses. They consist of cells originating from the anterior ethmoid air cells extending posteriorly and superiorly over the orbit from the frontal recess. They may mimic septated frontal sinuses as their posterior wall is the sku...
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 supraorbital vein drains the anterior part of the scalp and forehead 1. The supraorbital vein drains into the superior ophthalmic vein and the angular vein at the root of the nose 2.
The supraorbital vein drains the forehead venous plexus and descends along with 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...
The supratrochlear vein drains a venous plexus on the anterior forehead and scalp 1,2. It is a tributary of the angular vein along with the supra-orbital vein 3.
The supratrochlear vein descends down the medial part of the forehead until it reaches the root of the nose where it i...
The supreme meatus is an air passage of the lateral nasal cavity located between the supreme nasal concha and lateral nasal wall. The ostium of a posterior ethmoidal air cell may be seen in the supreme meatus.
The plural of meatus is meatus (Latin noun of the fourth declension) or ...
The supreme nasal concha or turbinate is one of the conchae in the nose and is a bony projection, arising from the medial surface of the labyrinth of the ethmoid above the superior nasal concha. Its presence is variable and has been reported in up to 52% of subjects 1.
The air passage between t...
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...
The tarsal plates of the eye are formed by dense fibrous tissue representing thickened extensions of the orbital septum, moulded to the curvature of the eyeball. Each eye has a superior tarsal plate and an inferior tarsal plate.
The plates anchor the roots of the eyelashes and contain tarsal (...
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)
Technetium agents based on the technetium-99m (Tc-99m) radioisotope are frequently used agents in medical imaging. The radioactive technetium radiotracer can be chelated to a number of different compounds to create specific radiopharmaceuticals and optimize the functional imaging of various stru...
Teeth (collective term: dentition) can be both primary and secondary, with the eruption of permanent teeth occurring over a long period between the ages of 6 and 24 years. When an individual has a complete set of teeth, they are said to be dentate, if some are missing they are partially dentate....
Telecanthus represents increased intercanthal distance. It is often used interchangeably with hypertelorism, referring to increased distance between the eyes.
Causes and associations
trauma: naso-orbito-ethmoidal (NOE) fractures
sinus and orbital tumors
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:
Temporal bone fracture is usually a sequela of significant blunt head injury. In addition to potentially damage to hearing and the facial nerve, associated intracranial injuries, such as extra-axial hemorrhage, diffuse axonal injury and cerebral contusions are common. Early identification of tem...
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
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 fibers).
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 a superior discotemporal space and inferior discomandibular space by the TMJ disc (or meni...
The axiolateral temporomandibular view allows for visualization 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 characterized 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 hemorrhage associated with subarachnoid hemorrhage, however some authors include retinal hemorrhage as well. The syndrome is a poor prognostic marker in patients with subarachnoid hemorrhage.
Terson syndrome has been reported to occur in 13-50% o...
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 edematous 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. They are however reported to be the second most common type of primary mediastinal cyst 7....
The thyrocervical trunk is one of the 3 branches of the first part of the subclavian artery and gives off 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 wal...
The thyroglossal duct is an epithelium-lined connection between the foramen cecum 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 cecum located at the junction of a...
Thyroglossal duct cysts (TGDC's) are the most common type of congenital neck cysts and pediatric neck masses. 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, a...
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...
Thyroid-associated orbitopathy is the most common cause of proptosis in adults and is most frequently associated with Graves disease. On imaging, it is characterized by bilateral and symmetrical enlargement of the extraocular muscle bellies. The typical distribution is inferior rectus > medial r...
Successful treatment of thyroid cancer 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 characterizing thyroid nodules, h...
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 bilateral flattened laminae that are fused anteriorly in the median plane to form the laryngeal prominence. Eac...
The thyroidea ima artery is an uncommon variant of the blood supply to the inferior aspect of the thyroid gland. It is reported in ~7.5% (range 1.5-12.2%) of individuals and can arise from:
right common carotid artery
internal thoracic artery
The thyroidea ...
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...
TI-RADS is a risk stratification system for classifying thyroid lesions and was recently recognized in an American College of Radiology (ACR) white paper1. Its use is being advocated similar to BI-RADS category for breast lesions.
In 2017, a white paper2 was released by the ACR committee on th...
Thyroid inferno refers to the color 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 color flow seen diffusely throughout the gland representing increased vascularity and arteriovenou...
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 categorized 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...
Tc-99m pertechnetate thyroid scan is a functional nuclear medicine study used to assess the thyroid gland.
fast for 4 hours prior to exam
dose and route of administration
111-185 MBq (3-5 mCi) IV
time of imaging
Thyroseq® is an expanded gene classifier test designed for further evaluation of indeterminate thyroid nodules on fine needle aspiration (FNA). In particular, it is designed to further evaluate nodules that show atypia of undetermined significance / follicular lesion of undetermined significance...
Thyrotoxicosis is a hypermetabolic clinical syndrome caused by a pathological excess of circulating free T4 (thyroxine) and/or free T3 (tri-iodothyronine).
Although commonly done, thyrotoxicosis should not be confused with, nor is it synonymous with hyperthyroidism. The latter term...
Tinnitus refers to a sensation of “sound in one ear or both ears, such as buzzing, ringing, or whistling, occurring without an external stimulus” 1. It can be subjective or objective.
It is thought that as many as 40 million people in the United States may have tinnitus. The repor...
Tobey-Ayer-Queckenstedt sign is used in the diagnosis of unilateral and bilateral lateral sinus thrombophlebitis. In cases where the lateral sinus is obstructed on one side, compression of the jugular vein on the intact side causes a rise in CSF pressure, whereas compression of the obstructed si...
Tolosa-Hunt syndrome (THS) is an idiopathic inflammatory condition that involves the cavernous sinus and orbital apex and is essentially a clinical diagnosis of exclusion.
Clinically it refers to the presence of a painful ophthalmoplegia secondary to surrounding cavernous...
The tongue is a complex, principally muscular, structure that extends from the oral cavity to the oropharynx. It has important roles in speech, swallowing and taste.
The tongue has a tip, ventral surface, dorsal surface and root. The tongue is made of a midline lingual septum an...
Tonsillitis refers to inflammation of any of the tonsils and is one of the most common head and neck infections in adolescents and young adults.
Patients may present with a variety of symptoms including painful throat (may be unilateral), dysphagia, fevers, tender cervica...
Tonsilloliths, also known as tonsil (or tonsillar) stones or calculi, are clusters of calcifications that form in tonsillar crypts, within the tonsils or around them. Although they are uncommon and benign, they may be symptomatic (pain, halitosis, etc).
Small foci of calc...
Tornwaldt cyst (also spelled as a Thornwaldt cyst or Thornwald cyst) is a common incidental benign midline nasopharyngeal mucosal cyst.
The lesion is developmental and usually asymptomatic. In most cases it is found incidentally; as such, age of diagnosis typically represents age ...
Torticollis (wryneck) is a clinical finding of head tilt with or without rotational spinal malalignment. It is not a diagnosis in itself and there are a wide range of underlying conditions. It is most common in the pediatric age group.
Torticollis can be acute (<1 week) or chronic (...
Torus ethmoidalis, also known as torus lateralis, is the term given when there is no air cell in the ethmoid bulla (failure of pneumatization). It is encountered in 8% of subjects.