The supraodontoid space, also known as the supradental space or apical cave, is an extradural space at the anterior craniocervical junction superior to the odontoid process of C2 (dens axis).
The space is a cave-shaped region facing posteriorly with the following boun...
The Tuli classification of occipital condyle fractures is a clinically-oriented system for describing these injuries based on fracture displacement and ligamentous injury. It is newer than the more well-known Anderson and Montesano classification of occipital condyle fractures and allows the inc...
Central nervous system neuroblastoma, FOXR2-activated is a novel brain tumor entity recently included in the WHO brain tumor classification 1.
Central nervous system neuroblastoma with FOXR2 activation was identified in 2016 as a new molecular entity, distinguished from primitive n...
Hair (TA: pilus/pili) remains important physiologically and psychologically for humans. The hair shaft develops from a structure known as the hair follicle. Each hair has an arrector pili muscle and both sensory and sympathetic neural connections.
The hair shaft (TA: stipes pili)...
The tram-track sign refers to the posterior cruciate ligament (PCL) appearance when it has a diffuse or partial thickening of the anteroposterior diameter greater than 7 mm. It is associated with longitudinal intraligamentous signal abnormalities showing fluid signal characteristics (hyperintens...
The posterior superior aortic recess, (also known as the superior pericardial recess or the superior sinus) is one of the variable invaginations of the superior aortic recess and is located posterior to the ascending aorta.
It may mimic mediastinal lymphadenopathy or a bronchogenic cyst.
The posterior pericardial recess is one of the pericardial recesses forming a small space within the pericardium. It arises from the superior margin of the oblique pericardial sinus, posterior to the right pulmonary artery and medial to the bronchus intermedius.
It may mimic mediastinal lymphad...
Medial cuneiform to second metatarsal distance is the measurement of the distance between the lateral aspect of the medial cuneiform and the medial aspect of the base of the second metatarsal bone 1,2.
Medial cuneiform to second metatarsal distance is an important measurement used in ass...
Post-traumatic pseudolipomas, also known as post-traumatic lipohypertrophy, are prominent increases in the volume of subcutaneous adipose tissue or even benign tumors arising at the location of a preceding blunt soft tissue trauma 1.
Focal palpable mass, not tender and wi...
Lateral tibiotalar distance is a measurement on an ankle anterior drawer lateral view to assess for ankle instability.
On an ankle anterior drawer lateral view (typically performed using a Telos device 2-4), the distance between the posterior tip of the distal tibial articular sur...
A furuncle, also known as a boil, is an infected hair follicle with extension through the dermis into the subcutaneous soft tissues (cf. folliculitis, a more superficial hair follicle infection, with pus limited to the epidermis).
Outbreaks of furunculosis are seen, ...
The double beak sign refers to the sudden tapering that two adjacent intestinal loops show in the internal hernia at the transition point of the closed loop obstruction.
The marked reduction in caliber results in distension of the afferent and efferent intestinal loops.
History and etymology
Eburnation describes the appearance of bone following a degenerative process in which subchondral or otherwise exposed bone acquires a non-anatomical sclerotic, microimpacted, and "polished" articular surface.
This phenomenon typically arises in one of two situations:
hypertrophic non-union of...
Folliculitis (plural: folliculitides) is an inflammation of the hair follicle, which is usually infective and due to bacteria, most commonly Staphylococcus aureus.
Folliculitis is more common in men 1.
hot tubs, especially Pseudomonas aeruginosa
The Nunley-Vertullo classification is one of several classification systems used for the categorization of Lisfranc injuries. It is based on clinical, x-ray and bone scan findings and also associates the stages with management options or recommendations regarding those injuries 1-3.
Intraparotid nodal metastases refer to metastatic involvement of intraparotid lymph nodes from either a primary parotid tumor or an extraparotid tumor in the head and neck (e.g. nasopharyngeal carcinoma).
There may be a predilection towards the superficial lobe or tail regi...
The long axial hindfoot alignment view is a specialized, weight-bearing radiographic view that examines the hindfoot alignment as part of a foot and ankle instability investigation.
The long axial view requires no equipment and has higher inter-observer reliability compared to the standard hin...
The hindfoot alignment view is a specialized, weight-bearing radiographic view that examines the hindfoot alignment as part of a foot and ankle instability investigation.
The long axial view requires no equipment and has higher inter-observer reliability when measuring angular hindfoot alignme...
The weight-bearing medial oblique view of the foot is a specialized projection that places the foot under normal weight-bearing conditions. The projection is utilized to assess the foot under stress and better demonstrate structural and functional deformities.
This projection is ...
The weight-bearing mortise (mortice is equally correct) view of the ankle is a specialized projection that places the joint under normal weight-bearing conditions. The projection is utilized to assess the joint under stress and better demonstrate structural and functional deformities.
The weight-bearing AP view of the ankle is a specialized projection that places the joint under normal weight-bearing conditions. The projection is utilized to assess the joint under stress and better demonstrate structural and functional deformities.
This projection is utilized ...
The weight-bearing lateral view of the ankle is a specialized projection that places the joint under normal weight-bearing conditions. The projection is utilized to assess the joint under stress and better demonstrate structural and functional deformities.
This projection is util...
Antipyretics is the term given to medication that reduces a fever.
Commonly used antipyretics 1:
However these agents are far from being side effect free, and research continues into safer body temperature-lowering agents 2.
The thalamo-occipital distance is a marker of ventricular size in infants. It is defined as the distance between the most posterior surface of the thalamus at its junction with the choroid plexus and the outermost point of the occipital horn in the parasagittal plane 1.
The anterior horn width is a marker of ventricular dilatation. It is predominantly used in prenatal and neonatal imaging to determine ventriculomegaly.
The anterior horn width is the diagonal width of the anterior horn at its widest point in the coronal plane 1. In neonates, this i...
The anterior to posterior fibular gap illustrates the displacement of the proximal and distal fibular fragments in trans-syndesmotic lateral malleolar fractures on the lateral view of the ankle and might indicate a medial injury.
The anterior to posterior fibular gap can be used in the s...
The tibiotalar angle is between the anatomic axis of the tibia and the superior articular surface of the talar dome. Differently from the talar tilt, the tibiotalar angle uses the tibial longitudinal axis instead of the distal articular surface as a tibial reference point.
The first to second metatarsal distance or M1-M2 distance is the length between the bases of the first and second metatarsal bone and a measurement for the evaluation of midfoot instability.
The first to second metatarsal distance is used for the evaluation and classification of midfoot ...
The hallux interphalangeal angle is between the proximal and distal phalanx of the great toe and serves for the evaluation of toe deformity at the level of the first interphalangeal joint.
The hallux interphalangeal angle is used in the setting of hallux valgus or hallux varus to assess ...
The distal metatarsal articular angle (DMAA) evaluates the relationship between the longitudinal axis and the articular surface of the first metatarsophalangeal joint and thus metatarsophalangeal coverage or joint congruity on a weight-bearing dorsoplantar radiograph of the foot.
Autoimmune hemolytic anemia is a group of hemolytic anemias characterized by an antibody response to red blood cells. It can present as acute or chronic anemia. It can be idiopathic or can occur with other disorders.
Several types have been described:
warm-antibody type anemia (WAIHA)
A mnemonic to remember the radiographic signs of pulmonary edema is:
A: alveolar opacification
D: diffuse interstitial thickening (septal lines) and diversion (vascular upper zone diversion, cephalisation)
E: effusions (pleural)
Medial cuneiform-fifth metatarsal height is the distance between the most inferior part of the medial cuneiform and the most inferior part of the base of the 5th metatarsal and is used to evaluate the height and integrity of the medial vertical arch 1.
Medial cuneiform-fifth metatarsal h...
The ADNEX (Assessment of Different NEoplasias in the adneXa) model is a risk model developed by the IOTA (International Ovarian Tumor Analysis) group to differentiate benign and malignant neoplasms of the ovary and, among them, four different subgroups (borderline, stage I cancer, stage II-IV ca...
"Bow-tie sign" refers to the appearance of rotated facets in unilateral facet joint dislocation. Facet joint displacement coupled with a rotational deformity gives a bow-like like appearance on a lateral view radiograph of spine 1.
Talar shift is a concept, sign and/or measurement describing a displacement of the talus in relation to the articular surface of the distal tibia and the malleolar end segment. The direction of the talar shift is further described in the medical literature and lateral talar shift receives the mo...
Talar tilt is a measurement of the angle between the talus and the distal tibia, used in the assessment of ankle instability and ankle osteoarthritis (OA).
Talar tilt is an important measurement in the assessment of ankle osteoarthritis. It is measured as part of the Kellgren and Lawrenc...
The Landells (and van Peteghem) classification of fractures of the atlas is one of the commonly used systems to describe C1 vertebral injuries.
Fractures are classified by their involvement of the C1 anterior arch, posterior arch, and/or lateral mass 1:
type I: confined to eith...
The term lead pipe fracture is the term for a radiographic appearance given to a simultaneous greenstick fracture of one side of the bone (usually metaphysis) with a buckle fracture of the opposing cortex of the same bone.
There are differing opinions in texts as to whether this term should be...
Age-related macular degeneration (AMD) is an eye disease that affects central vision. It occurs when aging causes damage to the macula. The macula is responsible for fine detailed vision also known as central vision.
Nerve compression syndromes of the shoulder is a term used to include diseases of the shoulder that cause weakness, discomfort or numbness of the upper extremity. These include quadrilateral space syndrome, suprascapular neuropathy, long thoracic nerve palsy and multiple others 1. They are usual...
The Greek alphabet has been used in science and mathematics for millennia. The alphabet has 24 letters with an order similar to the Latin alphabet (used for English and many European languages).
In the list, the name of the letter is given first, followed by the upper and lower case symbols 1....
Calcinosis of chronic renal failure is a rare cause of soft tissue calcifications in hemodialysis patients with chronic renal failure. This condition is characterized by the deposition of calcium phosphate crystals in the periarticular soft tissues, resulting in large calcified masses.
Lobular capillary hemangioma of the nasal cavity, also known as nasal pyogenic granuloma, is an uncommon benign, rapidly growing vascular neoplasm of the nasal cavity.
The term “pyogenic granuloma” is a misnomer due to its lack of infectious origin according to histological and mic...
Posterior ligamentous complex injury refers to tears/ruptures of the spinal posterior ligamentous complex, which consists of the ligamentum flavum, interspinous ligaments, supraspinous ligament, and facet joint capsules. Posterior ligamentous complex disruption is a central part of the currently...
Post traumatic arterio-venous vascular malformations are an uncommon acquired form arteriovenous malformations which occur following a traumatic to that site.
As with other vascular malformations, they comprise multiple communicating channels between arterial and venous channels at t...
Dural venous sinus cysts are rare, usually congenital lesions, most commonly observed as fluid-filled intraluminal lesions on cross-sectional imaging.
Dural venous sinus cysts are very rare, and are mostly congenital 1.
Most dural venous sinus cysts are true fluid-fi...
Ovarian agenesis refers to a situation where there is a congenital absence of the ovary.
Unilateral ovary agenesis affects approximately 1 in one in 11,240 women while bilateral agenesis is even rarer 1.
Most patients with agenesis of the ovary are asympt...
Ventricular arrhythmias are potentially very dangerous cardiac arrhythmias arising from the cardiac ventricles that require immediate attention and medical care and include the following rhythms:
premature ventricular complexes
torsades de pointes
Acute encephalopathy is a general term that describes the clinical presentation of a patient with acute cerebral dysfunction. It is usually caused by viral infections, metabolic disorders, dysfunction of the liver or kidneys, or hypertension.
Acute encephalopathy may occur in adults and childre...
Acute leukoencephalopathy with restricted diffusion (ALERD) is a clinicoradiological spectrum of disease with clinical features of leukoencephalopathy and associated imaging findings where diffusion restriction is the dominant finding.
The dominant radiological feature is...
Atrioventricular block, AV block or heart block is a conduction disturbance and a type of arrhythmia where the impulse transmission between the cardiac atria and ventricles is either transiently or permanently delayed or completely blocked 1.
Atrioventricular block can be found in...
Medical devices in the limbs are regularly observed by radiologists on plain film, CT and MRI reporting. Most commonly they include orthopedic hardware.
joint replacement hardware (arthroplasty)
joint fusion hardware (arthrodesis)
internal fixation hardware (ORIF)
The flame sign refers to a gradual tapering of contrast opacification in the mid-cervical internal carotid artery, sparing the carotid bulb. The sign can be observed on angiography (digital subtraction angiography 1, CT angiography 1, or contrast-enhanced MR angiography 2) in either of two scena...
The quadruple screening test, also known as the quad screen, AFP Plus quad test or multiple marker screening test, is a maternal antenatal screening blood test that can be used in conjunction with other investigations e.g. ultrasound soft markers, to estimate the risk of aneuploidy 1.
This is ...
The nasal septal cartilage, also known as quadrangular cartilage, forms most of the anterior portion of the nasal septum, and is one of five named nasal cartilaginous components supporting the external nose.
Most of the anterior one-third of the nasal septum is formed by the sept...
The characteristic shape of the crescent has been given to many radiological signs over the years.
crescent sign (disambiguation)
crescent sign (arterial dissection)
crescent sign (inguinal hernia)
crescent sign (intravenous pyelogram)
crescent sign (lung hydatid)
crescent sign (osteonecro...
The doughnut sign, also known as the bull's-eye, halo or ring sign, is the name of a distinctive appearance of a missed testicular torsion on scrotal scintigraphy.
In a missed torsion (i.e. established testicular infarction), there is a reactive hyperperfusion of the ipsilateral dartos muscle ...
Subependymal cysts may either be postnatally acquired posthemorrhagic cysts or may be congenital (germinolytic). The congenital cysts may result from infection, ischemic injury, or hemorrhage.
Most frequently seen in preterm infants, likely related to their persistent germinal mat...
This is a basic article for medical students and other non-radiologists
Intussusception occurs when a loop of bowel is pulled into the lumen of a distal bowel loop, and is an important cause of acute abdominal pain, particularly in young children.
This is a summary article; ...
Peripheral T cell lymphoma is an uncommon, heterogeneous group of lymphoma. It can account for around 5-15% of non-Hodgkin lymphoma (NHL).
The word "peripheral" does not mean involvement in the extremities but refers to tumor cells that arise from lymphoid tissue outside of the bon...
Iodinated oil pulmonary embolism is a form of particulate material pulmonary embolism which in turn falls under non-thrombolic pulmonary emboli. Iodinated oil pulmonary embolism occurs in the setting of:
oily chemoembolisation of tumors
hepatocellular carcinoma 1,3
Presentation refers to the clinical details that need to be included as part of Radiopaedia cases and can include symptoms, signs, physical examination findings, relevant past history and/or laboratory studies. Complications, if part of the initial disease process (e.g. hemorrhage as a complicat...
A joint mouse (plural: joint mice) is a historical synonym for an intra-articular loose body. This evocative term predates the discovery of x-rays and originated in orthopedics. It derives from the way in which some intra-articular osteochondral fragments appeared to move rapidly around the insi...
A corkscrew esophagus, also known as a rosary bead esophagus, is a classic appearance of distal esophageal spasm on a barium swallow. It is actually quite a rare appearance which is seen in <5% cases of distal esophageal spasm. The finding is caused by multiple tertiary (non-propulsive) contract...
Pathology reports are encouraged to be uploaded as substantiation of the diagnosis of the case where appropriate.
text reports are preferred over scanned or photographed reports
no identifiable information should be included (see: patient confidentiality)
ideally, permission from the...
The Heidelberg bleeding classification categorizes intracranial hemorrhages occurring after ischemic stroke and reperfusion therapy.
Class 1: hemorrhagic transformation of infarcted brain tissue
1a: HI1: scattered small petechiae, no mass effect
1b: HI2: confluent petech...
The superficial epigastric vein (TA: vena epigastrica superficialis) is an important tributary of the great saphenous vein that drains the anterior abdominal wall inferior to the level of the umbilicus.
The superficial epigastric vein drains into the great saphenous vein at the saphenous openin...
The lateral thoracic vein (TA: vena thoracica lateralis) is a tributary of the axillary vein. It provides venous drainage for the axilla, anterolateral chest wall, including serratus anterior and pectoralis muscles and breast, and the supraumbilical abdominal wall.
In some texts, t...
The World Health Organizatiοn classification of skin tumors is the most widely used pathologic classification system for skin tumors. The most recent edition is the 4th, which was published in 2018 1. The radiologically relevant and common entities are reflected below.
Diverticula of the anal canal are very rare with only a few cases reported in the global literature.
Patients have presented with anorectal bleeding and/or pain.
The few cases have either not been characterized on imaging or only imaged on barium s...
Submandibular gland enlargement refers to an increase in the volume of the submandibular gland, exceeding "normal" values of 7.4 ± 1.8 mL 1.
submandibular duct stenosis (e.g. tumor, granulomatous disease)
acute sialadenitis: following ...
Syndesmotic screw fixation is a rigid fixation technique for stabilization of distal tibiofibular syndesmosis injury. Depending on the injury and the surgeon's preference it can involve the placement of one or two syndesmotic screws and can be combined with an antiglide plate.
The acromioclavicular (AC) distance or joint space is an important measurement in the evaluation of acromioclavicular joint injury.
The AC distance is assessed on the frontal radiograph of the shoulder as the distance between the medial cortex of the acromion and the lateral cortex...
An ulnar nerve neuropathy can refer to pathology and associated symptoms pertaining to the ulnar nerve anywhere along its course (i.e. from C8/T1 roots to the hand). It can occur at any site along its course and commonly occurs due to pathology at the elbow/cubital tunnel region or in the Guyon ...
Intramural pseudocysts are a rare form of pancreatic pseudocysts that occur within the wall of the upper gastrointestinal tract. They may result in gastric outlet obstruction.
They can considerably vary in size with one study reporting a range of 8 mm to 8 cm 1.
Unicentric Castleman disease (UCD) is considered the more common form of Castleman disease and involves one or more enlarged lymph nodes in a single region of the body that demonstrates histopathologic features that have features of Castleman disease. A subset of patients can have systemic symp...
Reduced leaflet motion refers to an abnormally decreased mobility of one or more valvular leaflets and is a phenomenon that has been observed after (transcatheter) implantation of prosthetic heart valves and gained clinical significance for the diagnosis of subclinical leaflet thrombosis.
The bowler hat sign refers to an appearance on a GI contrast study, which may be seen with both polyps and diverticula of the bowel. The filling defect produced by the pathology mimics the outline of a bowler hat. It was originally described for colonic lesions, but can be seen with lesions thro...
Diffuse low-grade glioma, MAPK pathway-altered is a novel tumor type included in the 5th Edition (2021) of the WHO brain tumor classification 1.
Several genetic mutations were recognized in low-grade IDH-wt/H3-wt brain diffuse gliomas occurring in children and adolescents, such as ...
Finger pathology is wide and includes all lesions involving the tendons, ligaments, muscles, bone, and articulations of the hand and foot digits.
brachydactyly - short digits
arachnodactyly - elongated, thin "spider-like" digits 1
polydactyly (hyperdactyly) - supernumerary digits
Two different radiological signs are named for their similarity in size and shape to grains of rice.
rice bodies (intra-articular)
rice grain calcification (cysticercosis)
Hypovascular retroperitoneal lesions are those which do not enhance in the late arterial and portal venous phases on CT. Some of these lesions may show progressive enhancement in the delayed phase due to their fibrous or myxoid matrix components.
Hypervascular retroperitoneal lesions are findings that enhance avidly in the late arterial phase with or without washout in the portal venous and delayed phases, on contrast-enhanced CT or MRI.
Early enhancement with slow washout
retroperitoneal paragangliomas - of...
Due to its distinctive morphology and its layered internal structure the onion has given rise to a number of signs in imaging:
onion bulb nerves: Charcot-Marie-Tooth type 1A and chronic inflammatory demyelinating polyneuropathies (CIDP)
onion peel sign: pulmonary hydatid cyst
onion skin peri...
Achard-Thiers syndrome is a rare condition in elderly postmenopausal females, which is illustrated by androgen excess and insulin resistance secondary to type 2 diabetes mellitus.
hirsutism in older females
high serum glucose levels
The long head of the biceps tendon (LHBT) is the proximal tendon of the long head of the biceps muscle and encircles the humeral head on its course. It has an intraarticular extrasynovial and an extraarticular portion.
insertion: supraglenoid tubercle of the scapula...
Salt and pepper noise, also known as impulse noise, has been used to describe the characteristic appearance of a certain artifact seen on MRI.
The artifact looks like innumerable black and white pixels throughout the image. Smoothing filters are algorithms designed to diminish the noise whilst ...
The salt and pepper sign has been given to the heterogeneous echotexture of the enlarged kidneys on ultrasound in children with autosomal recessive polycystic kidney disease (ARPCKD).
The salt and pepper sign has been used to describe the MRI appearance of the parotid gland in Sjögren syndrome. This pertains to a combination of punctate regions of calcification (pepper) and fatty replacement (salt) 1.
The salt and pepper sign is used to describe a typical MRI appearance of some highly vascular tumors which contain foci of hemorrhage, typically a paraganglioma 1-3. The appearance is on T1-weighted sequences, and is made up of:
punctate regions of hyperintensity = salt
small flow voids = pepp...
Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is an epileptogenic tumor of children and young adults.
First described in 2016 1, polymorphous low-grade neuroepithelial tumor of the young has been recently included in the new family of "pediatric-type" low-grade ...
The autonomic nervous system (ANS) is a subdivision of the peripheral nervous system. The autonomic system provides innervation of the involuntary muscles, i.e. myocardium and smooth muscle, and glands, through which fine control of homeostasis is maintained.
The afferent innervation of the aut...