Articles

Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.

68 results found
Article

Abscess

Abscesses are focal confined collections of suppurative inflammatory material and can be thought of as having three components 1: a central core consisting of necrotic inflammatory cells and local tissue peripheral halo of viable neutrophils surrounded by a 'capsule' with dilated blood vessel...
Article

Accessory meningeal artery

The accessory meningeal artery is a branch of the maxillary artery but can also branch from the middle meningeal artery. The artery passes upwards through the foramen ovale to supply the trigeminal ganglion and the dura mater of Meckel's cave and the middle cranial fossa. It also usually suppli...
Article

Accessory occipital bone sutures

The parietal and occipital bones in particular are common regions for accessory sutures because of their multiple ossification centres. The occipital bone has complex development, ossifying from six centres. The foramen magnum is surrounded by four ossification centres. On each side are the exo...
Article

Accessory parotid glands

Accessory parotid glands are a normal variant and represent ectopic salivary tissue separate from, but usually in close proximity to, the main parotid glands 1. Occasionally the accessory tissue is contiguous with the main glands. Epidemiology Accessory parotid glands are commonly picked up in...
Article

Achondroplastic base of skull abnormalities

Achondroplasia is the most common cause of short-limb dwarfism. (For a general discussion, see the generic article on achondroplasia.) As the skull base forms by endochondral ossification whereas the skull vault by membranous ossification, there is a marked discrepancy in relative size as the s...
Article

Acinic cell carcinoma (salivary glands)

Acinic cell carcinomas of the salivary glands are rare malignant neoplasms that account for 1-3% of all salivary gland tumours.  Pathology Pathology may superficially resemble normal serous (acinar) cells of the salivary glands. It is considered a low-grade, indolent malignancy, but with a ten...
Article

Acoustic schwannoma

Acoustic schwannomas (also known as vestibular schwannomas) are relatively common tumours that arise from the vestibulocochlear nerve (CN VIII) and represent ~80% of cerebellopontine angle masses. Bilateral acoustic schwannomas are strongly suggestive of neurofibromatosis type 2 (NF2). These tu...
Article

Acquired cholesteatoma

Acquired cholesteatomas make up 98% of all middle ear cholesteatomas and are almost always closely related to the tympanic membrane, from which most are thought to arise.  Clinical presentation The vast majority of acquired cholesteatomas develop as a result of chronic middle ear infection and...
Article

Acrocephalopolysyndactyly

Acrocephalopolysyndactyly (ACPS) syndrome is comprised of a rare group of disorders collectively characterised by: calvarial anomalies: e.g. craniosynostoses digital anomalies: syndactyly and polydactyly While there can be some overlap in features, they can be primarily classified into the fo...
Article

Acrocephalosyndactyly

Acrocephalosyndactyly syndromes (ACS) is a rare group of disorders collectively characterised by: calvarial anomalies, e.g. craniosynostoses digital anomalies, e.g. syndactyly Classification While there can be some overlap in features, they can be primarily classified into the following majo...
Article

ACR Thyroid Imaging Reporting and Data System (ACR TI-RADS)

ACR TI-RADS is a reporting system for thyroid nodules on ultrasound proposed by the American College of Radiology (ACR) 1. This uses a standardised scoring system for reports providing users with recommendations for when to use fine needle aspiration (FNA) or ultrasound follow-up of suspicious ...
Article

Acute invasive fungal sinusitis

Acute invasive fungal sinusitis is the most aggressive form of fungal sinusitis. It is seen particularly in immunocompromised patients and is the source of significant morbidity and mortality. It should be distinguished from the other two forms of invasive fungal sinusitis, chronic invasive fung...
Article

Acute mastoiditis

Acute mastoiditis is largely a disease of childhood and occurs when acute otitis media extends into the mastoid air cells.  Terminology When mastoiditis and acute otitis media occur concurrently, sometimes the term acute otomastoiditis is used.  When mucoperiosteal involvement evolves into bo...
Article

Acute otitis externa

Acute otitis externa (AOE), also known as "swimmer's ear", is inflammation of the external auditory canal (EAC) that can involve the pinna as well. Bacterial infection, most commonly with Pseudomonas aeruginosa, is responsible for the overwhelming majority of cases. It is a common condition. Ep...
Article

Acute sinusitis

Acute sinusitis is an acute inflammation of the paranasal sinus mucosa that lasts less than four weeks and can occur in any of the paranasal sinuses. If the nasal cavity mucosa is also involved then the term rhinosinusitis may be used. Clinical presentation Fever, headache, postnasal discharge...
Article

Adenocarcinoma of the lacrimal glands

Adenocarcinoma of the lacrimal glands is rare, with few cases reported in the literature since it was first described in 1996 1. Primary adenocarcinoma of the lacrimal gland is extremely rare; only 9 cases have been reported in the literature 1,2. It can be classified into high- and low-grade ma...
Article

Adenoidal hypertrophy

Adenoidal hypertrophy or enlargement is common in childhood and is due to an increase in the size of the adenoids. Clinical presentation nasal congestion: adenoid facies chronic or recurrent otitis media due to their proximity to the Eustachian tubes swallowing difficulties speech anomali...
Article

Adenoid cystic carcinoma

Adenoid cystic carcinomas are a rare histological subtype of adenocarcinoma. Pathology Adenoid cystic carcinomas are generally considered low grade 4. The tumours have a notable tendency for perineural spread. Location They have a wide distribution and mainly occur in relation to the airways...
Article

Adenoid cystic carcinoma of lacrimal glands

Adenoid cystic carcinoma (ACC) of the lacrimal glands is an extraconal malignancy usually originating from the orbital lobe of the lacrimal gland. Clinical presentation It often presents with orbital pain and paresthesia, since this type of tumour is frequently associated with perineural sprea...
Article

Adenoid cystic carcinoma of the salivary glands

Adenoid cystic carcinoma (ACC) of the salivary glands is the most common malignancy involving the minor salivary glands and the second most common malignancy involving the parotid gland. Pathology Adenoid cystic carcinomas arise more commonly in the minor salivary glands (~55%) than in the maj...
Article

Adenoid facies

Adenoid facies, also known as the long face syndrome, refers to the long, open-mouthed face of children with adenoid hypertrophy. Hypertrophy of the nasopharyngeal pad of lymphoid tissues (adenoids) is the most common cause of nasal obstruction in children. The mouth is always open because upper...
Article

Adenolipoma (thyroid gland)

Adenolipoma of the thyroid gland (also known as a thyrolipoma or a thyroid hamartoma) is a rare, benign fat-containing thyroid lesion. These lesions are usually well encapsulated and are composed of varying degrees of follicular thyroid tissue (thyroid adenoma) and mature adipose tissue; the amo...
Article

Adenomatoid odontogenic tumour

Adenomatoid odontogenic tumours are rare and differ from most other dentition related lesions in that they more frequently occur in the maxilla. Epidemiology They are also seen more frequently in females, most frequently in the second decade of life. Radiographic features They present as an ...
Article

Adrenal vein sampling

Adrenal vein sampling (AVS) is a procedure where blood is collected from the adrenal veins via catheter to confirm autonomous hormone production, if it is unilateral or bilateral, and to guide further treatment. Indication AVS is commonly performed in primary aldosteronism, being indicated to ...
Article

Adult cervical lymphadenopathy (differential)

Cervical lymphadenopathy in an adult can result from a vast number of conditions. They include: malignancy metastases  from head and neck tumours lymphoma other neoplastic lesions Castleman disease Kaposi sarcoma infection bacterial infection viral infection Epstein-Barr virus herpes...
Article

Agger nasi cells

Agger nasi air cells are the most anterior ethmoidal air cells lying anterolateral and inferior to the frontoethmoidal recess and anterior and above the attachment of the middle turbinate. They are located within the lacrimal bone and therefore have as lateral relations the orbit, the lacrimal s...
Article

Allergic fungal sinusitis

Allergic fungal sinusitis (AFS) is the most common form of fungal sinusitis and is common in warm and humid climates. On imaging, it usually presents as opacification and expansion of multiple paranasal sinuses, unilaterally or bilaterally, with content that is centrally hyperdense on CT. MRI sh...
Article

Allgrove syndrome

Allgrove syndrome (also known as triple A syndrome) is an autosomal recessive condition that consists of three main findings: achalasia alacrima ACTH insensitivity
Article

Alport syndrome

Alport syndrome is an X-linked recessive disease characterised by:  haematuria sensory neural hearing loss: typically high frequency 2 ocular abnormalities  anterior lenticonus: most common ocular abnormality; may result in cataracts perimacular pigmentary changes flecks around the fovea 2...
Article

Amaurosis fugax

Amaurosis fugax is the transient mono-ocular loss of vision, normally lasting a few seconds to a few minutes, and is secondary to vascular ischaemia/insufficiency. Usually the cause is ascribed to occlusion of the central retinal artery there are a wide number of local and central causes. 
Article

Ameloblastic fibroma

Ameloblastic fibromas appear as unilocular lucent mandibular lesions, most frequently in the posterior mandible, and are usually associated with impacted teeth, centred on the unerupted crown. They, therefore, appear very similar to unilocular ameloblastomas. They are composed of enamel and embr...
Article

Ameloblastic fibro-odontoma

Ameloblastic fibro-odontoma (AFO) is a rare benign mixed odontogenic tumour that usually arises in the maxilla and mandible. According to the 2005 WHO classification of odontogenic tumours, it is defined as a benign tumour that resembles ameloblastic fibroma but contains enamel and dentin. Epid...
Article

Ameloblastoma

Ameloblastomas are locally aggressive benign tumours that arise from the mandible, or, less commonly, from the maxilla. Usually present as a slowly but continuously growing hard painless lesion near the angle of the mandible in the 3rd to 5th decades of life, which can be severely disfiguring if...
Article

Anaplastic thyroid carcinoma

Anaplastic thyroid carcinoma (ATC) is a highly aggressive form of thyroid cancer and accounts for ~1-2% of primary thyroid malignancies. Of all the subtypes, this carries the worst prognosis. Epidemiology Typically occurs in the elderly (peak incidence in 6th to 7th decades). A significant pro...
Article

Anatomy curriculum

The anatomy curriculum is one of our curriculum articles and aims to be a collection of articles that represent the core anatomy knowledge for radiologists and imaging specialists. General anatomy Neuroanatomy Head and neck anatomy Thoracic anatomy Abdominal and pelvic anatomy Spinal anat...
Article

Angular vein

The angular vein drains the anterior region of the scalp 1. It is formed by the union of the supratrochlear and supraorbital veins and becomes the facial vein 1,2,3. Gross Anatomy The angular vein is formed at the medial canthus as the supratrochlear vein and supraorbital vein unite 1,2. The a...
Article

Ansa cervicalis

The ansa cervicalis is a component of the cervical plexus which gives muscular branches to the geniohyoid muscle of the suprahyoid group and all 4 of the infrahyoid muscles.  Gross anatomy Roots superior root: derived from the anterior primary rami of C1 inferior root: derived from the anter...
Article

Anterior cervical space

The anterior cervical space is a small infrahyoid compartment of the head and neck. It is a fat containing space and is not enclosed by fascia 1. Gross anatomy Contents areolar fat Relations posterior: carotid space medial: visceral space superior: submandibular space Related pathology ...
Article

Anterior cord syndrome

Anterior cord syndrome (also known as Beck's syndrome or anterior spinal artery syndrome) is a clinical subset of spinal cord injury syndromes, due to ischaemia/infarction of the anterior two-thirds of the spinal cord, typically sparing the posterior third. Clinical presentation Patient presen...
Article

Anterior cranial fossa

The anterior cranial fossa constitutes the floor of cranial vault which houses the frontal lobes of the brain. Gross anatomy Structures present in the midline of anterior cranial fossa from anterior to posterior are:  groove for superior sagittal sinus groove for anterior meningeal vessels ...
Article

Anterior division of the mandibular nerve

The anterior division of the mandibular division of the trigeminal nerve has four branches, which are all motor branches except one. The four branches are: deep temporal nerves lateral pterygoid nerves masseteric nerve buccal nerve
Article

Anterior ethmoidal artery

The anterior ethmoidal artery is a branch of the ophthalmic artery. It supplies the anterior and middle ethmoidal sinuses, frontal sinus, the lateral nasal wall and the nasal septum (see nasal cavity). Course It traverses the anterior ethmoidal foramen with the anterior ethmoidal nerve (which ...
Article

Anterior ethmoidal nerve

The anterior ethmoidal nerve is an extraconal branch of the nasociliary nerve, a branch of ophthalmic division of the trigeminal nerve. Some authors describe it as either the terminal branch or a direct continuation of the nasociliary nerve.  It branches off distal to the infratrochlear nerve an...
Article

Anterior jugular vein

The anterior jugular vein is a paired tributary of the external jugular vein. Gross anatomy Location It arises beneath the chin in the region of the hyoid bone or suprahyoid neck. Origin and course The anterior jugular vein has its origin as the confluence of several small superficial subma...
Article

Anterior lacrimal crest

The anterior lacrimal crest is a bony projection on the frontal process of the maxilla continuous with the orbital rim which creates the lateral margin of the lacrimal sac fossa. The medial palpebral ligament is attached to anterior lacrimal crest. Immediately anterior to the anterior lacrimal ...
Article

Anterior nares

The anterior nares (or nostrils) form the entrance to the nose. Each naris is formed by a ring of structures: medially the columella (soft tissue anteroinferior portion of the nasal septum) laterally and superiorly the ala inferiorly the nasal sill  
Article

Anterior superior alveolar canal

The anterior superior alveolar canal courses through the anterior wall of the maxillary sinus, and contains the anterior superior alveolar nerve, artery and vein. Usually, it shares a common channel with the infraorbital canal but when seen separately should not be confused for a fracture. 
Article

Anterior superior alveolar nerve

The anterior superior alveolar​ nerve, also known as the anterior superior dental nerve, is the third branch of the infra-orbital nerve, from the maxillary division of the trigeminal nerve. It is the largest of the superior alveolar nerves and contributes to the superior dental plexus. Gross an...
Article

Anterior triangle

The anterior triangle forms the anterior compartment of the neck and is separated from the posterior triangle by the sternocleidomastoid muscle. The triangles of the neck are surgically focussed, first described from early dissection-based anatomical studies which predated cross-sectional anatom...
Article

Antrochoanal polyp

Antrochoanal polyps (ACP) are solitary sinonasal polyps that arise within the maxillary sinus. They pass to the nasopharynx through the sinus ostium and posterior nasal cavity, enlarging the latter two. Similar, less common, polyps can arise in the sphenoid sinus extending into the nasopharynx:...
Article

Antrolith

An antrolith is a calcified mass within the maxillary sinus. The origin of the nidus of calcification may be extrinsic (foreign body in sinus) or intrinsic (stagnant mucus, fungal ball). Most antroliths are small and asympotomatic. Larger ones may present as sinusitis with symptoms like pain a...
Article

Arrested pneumatisation of the skull base

Arrested pneumatisation of the skull base is an anatomical variant that most commonly occurs in association with the sphenoid sinus. It is known that the sphenoid bones undergo early fatty marrow conversion antecedent to normal pneumatisation. However, for unclear reasons, some individuals exper...
Article

Arterial supply of the head and neck

The arteries of the head and neck are branches of the common carotid and subclavian arteries. common carotid artery carotid body carotid bifurcation internal carotid artery (segments) caroticotympanic artery persistent stapedial artery ophthalmic artery supraorbital artery lacrimal arte...
Article

Aryepiglottic folds

The aryepiglottic folds are two ligamentomuscular structures within the supraglottic larynx that function to protect the airway when swallowing. Gross Anatomy Each aryepiglottic fold is comprised of the superior ligamentous edge of the quadrangular membrane and covering mucous membrane1, the e...
Article

Arytenoid cartilage

The arytenoid cartilages are paired hyaline cartilages that articulate with the sloping upper border of the lamina of the cricoid cartilage by the cricoarytenoid joint. This joint allows movement of the arytenoid cartilages, which is vital in approximating, tensing and relaxing the vocal folds. ...
Article

Ascending cervical artery

The ascending cervical artery is 1 of the 4 branches of the thyrocervical trunk (off the first part of the subclavian artery). It is a small artery that ascends medial to the phrenic nerve on the prevertebral fascia. It contributes many small spinal branches into the intervertebral foramina of ...
Article

Ascending pharyngeal artery

The ascending pharyngeal artery, the smallest branch of the external carotid artery, is a long, slender vessel, deeply seated in the neck, beneath the other branches of the external carotid and under the stylopharyngeus. Summary origin: a branch of the external carotid artery course: vertical...
Article

Assessment of thyroid lesions (general)

Assessment of thyroid lesions is commonly encountered in radiological practice. Thyroid mass hyperplastic / colloid nodule / nodular hyperplasia: 85% adenoma follicular: 5% others: rare carcinoma papillary: 60-80% of carcinomas follicular: 10-20% medullary: 5% anaplastic: 1-2% thyroi...
Article

Assessment of thyroid lesions (ultrasound)

Ultrasound along with nuclear medicine, is an important modality for assessment of thyroid lesions, and it is also frequently used to guide biopsy. Diagnostic criteria for thyroid nodules continue to evolve with improving ultrasound technology. Radiographic features Ultrasound Calcification ...
Article

Asterion

The asterion is the junction on the side of the posteroinferior calvarium where three sutures meet: parietomastoid suture occipitomastoid suture lambdoid suture It is located at the posterior end of the parietotemporal suture, whereas the pterion is located at the anterior end. It is one of...
Article

Asteroid hyalosis

Asteroid hyalosis is a degenerative condition of the eye where there is accumulation of calcium soaps in vitreous chamber. Epidemiology The prevalence increases with age from 0.2% 43-54 year olds to 2.9% in 75-86 year olds. The overall prevalence is 1.2%. It is more commonly unilateral and fav...
Article

Asymmetric fatty bone marrow of the petrous apex

Asymmetric pneumatisation of petrous apex results in asymmetric fatty bone marrow within the petrous apex. It is a common incidental finding on brain and skull base MRI. Clinical presentation Asymptomatic. Pathology Asymmetric pneumatisation of the petrous apex results in the presence of bon...
Article

ATA guidelines for assessment of thyroid nodules

The American Thyroid Association (ATA) guidelines for assessment of thyroid nodules are meant to improve inter- and intra-reader consistency during assessment of thyroid nodules on ultrasound, and to facilitate communication with referring endocrinologists. The 2015 guidelines stress the import...
Article

Atlantodental interval

The atlantodental interval (ADI), as the name suggests, is the horizontal distance between the anterior arch of the atlas and the dens of the axis, used in the diagnosis of atlanto-occipital dissociation injuries and injuries of the atlas and axis. It is the distance (in mm) between the posteri...
Article

Auditory brainstem response tracing (mnemonic)

This mnemonic helps when remembering the ascending order of structures that corresponds to each waveform in an auditory brainstem response (ABR) tracing: E COLI Mnemonic E: eighth nerve action potential (wave I) C: cochlear nucleus (wave II) O: olivary complex (superior) (wave III) L: late...
Article

Auricular pseudocyst

An auricular pseudocyst is a rare and benign cystic swelling resulting from intracartilaginous accumulation of fluid within the pinna. Epidemiology While it can occur at any age and in either gender, it typically presents in middle aged males with a mean age of presentation being around 35-40 ...
Article

Auriculotemporal nerve

The auriculotemporal nerve is a sensory branch of the posterior division of the mandibular division of the trigeminal nerve. Gross anatomy The auriculotemporal nerve divides posteriorly from the posterior division of the mandibular division before dividing into two roots separate to encircle t...
Article

Autoimmune thyroiditis

Autoimmune thyroiditises (AIT) refers to a group of conditions where there is inflammation involving the thyroid gland related to thyroid antibodies. Epidemiology They are most common thyroid disease group in the paediatric population 5. Pathology Entities that fall under this category inclu...

Updating… Please wait.
Loadinganimation

Alert accept

Error Unable to process the form. Check for errors and try again.

Alert accept Thank you for updating your details.