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.

48 results found
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Abscess

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

Accessory parotid glands are a normal variant and represent ectopic salivary tissue present away and separate from the main parotid gland 1. Epidemiology Accessory parotid glands are not rare and are seen in ~20% of the general population 2. Gross anatomy Located on the masseter muscle, ante...
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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 sk...
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Acinic cell carcinoma of 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...
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Acoustic schwannoma

Acoustic schwannomas (a.k.a. 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 tumours c...
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Acquired cholesteatoma

Acquired cholesteatomas makeup 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 ...
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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...
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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...
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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...
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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 b...
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Acute sinusitis

Acute sinusitis is an acute inflammation of the nasal and paranasal sinus mucosa that last less than four weeks and can occur in any of the paranasal sinuses. Clinical presentation Fever, headache, postnasal discharge of thick sputum, nasal congestion and abnormal smell. Pathology Aetiology ...
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Adenoid cystic carcinoma

Adenoid cystic carcinoma (ACC) are a rare histological subtype of adenocarcinoma. Pathology ACCs are generally considered low grade 4. The tumors have notable tendency for perineural spread. Location They have wide distribution and mainly occur in relation to the airways, lacrimal glands and...
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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...
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Adenoid cystic carcinoma of salivary glands

Adenoid cystic carcinoma (ACC) of the salivary glands is the second most common malignancy involving the parotid and the most common involving minor salivary glands. Pathology ACCs arise more commonly in the minor salivary glands (~55%) than in the major salivary glands. They are locally aggre...
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Adenoid facies

Adenoid facies refers to the long, open-mouthed face of children with adenoid hypertrophy. Hypertrophy of the nasopharyngeal pad of lymphoid tissues (the adenoids) is the most common cause of nasal obstruction in children. The mouth is always open because upper airway congestion has made patient...
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Adenoidal hypertrophy

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

Adenolipoma of the thyroid gland (also known as a thyrolipoma or a thyroid hamartoma) is a benign rare fat containing thyroid lesion. These lesions are usually well encapsulated and are composed of varying degrees of thyroid glandular tissue and fat tissue; the amount of fat can markedly vary (...
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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...
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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...
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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 s...
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
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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...
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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

Ameloblastoma

Ameloblastomas are benign, locally aggressive tumours that arise from the mandible, or less commonly from the maxilla. Usually presented as a hard painless lesion near the angle of the mandible in the 3rd to 5th decades of life.  On imaging, they are commonly identified as a well-defined, expan...
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...
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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...
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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 ...
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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 posterior third. Clinical presentation Patient present wi...
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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 jugular vein

The anterior jugular vein is a paired tributary of the external jugular vein. Gross anatomy Origin and course The anterior jugular vein has its origin in the region of the hyoid bone or suprahyoid neck, as the confluence of several small superficial veins. It descends near the midline, medial...
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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 superior alveolar canal

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

Antrochoanal polyp

Antrochoanal polyps (ACP) are solitary sinonasal polyps that arises within the maxillary sinus but passes through and enlarges the sinus ostium and posterior nasal cavity to the nasopharynx.  Similar polyps can arise in the sphenoid sinus and extend into the nasopharynx, these are termed spheno...
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 and subclavian arteries. common carotid external carotid superior thyroid superior laryngeal ascending pharyngeal lingual facial occipital posterior auricular superior temporal maxillary (1st part) mandibular a...
Article

Arytenoid cartilage

The arytenoid cartilages are paired 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. Gross a...
Article

Ascending pharyngeal artery

The ascending pharyngeal artery, the smallest branch of the external carotid, 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: vertically with...
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 the star shaped junction on the side of the calvarium where 3 sutures meet: parietomastoid suture occipitomastoid suture lambdoid suture It is located at the the posterior end of the parietomastoid suture, where as 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

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...
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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

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...

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