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.

32 results found
Article

Dacryoadenitis

Dacryoadenitis is infection of the lacrimal gland results in diffuse homogeneous enlargement, which can sometimes compress the globe. Most common organisms are Staphylococcus aureus, mumps, infectious mononucleosis, and influenza virus.
Article

Dacryocystitis

Dacryocystitis is the inflammation of the nasolacrimal sac and needs to be distinguished from conjunctivitis and pre-septal orbital cellulits (both of which often co-exist).  Epidemiology Dacryocystitis has a bimodal distribution: neonates and individuals older than 40 years of age.  Most cas...
Article

Dacryocystocele

Dacryocystoceles are caused by obstruction of both the proximal and distal ends of the nasolacrimal duct. An imperforate Hasner membrane causes the distal blockage, but the cause of proximal obstruction is less clearly understood . Epidemiology Dacryocystoceles, although rare, are the second m...
Article

Danger space

The danger space is a potential space located behind the true retropharyngeal space, which connects the deep cervical spaces to the mediastinum.  Gross anatomy Boundaries anteriorly: alar fascia posteriorly: prevertebral layer of the deep cervical fascia superiorly: clivus inferiorly: post...
Article

De Quervain thyroiditis

De Quervain thyroiditis (or subacute granulomatous thyroiditis) is a form of self limited subacute thyroiditis usually preceded by upper respiratory tract viral infection such as mumps, measles, coxsackie virus, adenovirus, and influenza viruses. Epidemiology It usually affects middle age fema...
Article

Deep cervical fascia

The deep cervical fascia consists of 3 separate but related fascial layers that encircle structures in the neck and allow anatomic compartmentalisation. All 3 layers meet to form the carotid sheath. From superficial to deep, the 3 layers are: 1. Investing layer of the deep cervical fascia is th...
Article

Deep spaces of the head and neck

Head and neck anatomy is described in slightly different terms in the radiology literature reflecting the importance of fascia lined spaces in confining various pathologies. As such the neck has been divided into a number of 'deep spaces' which overlap with traditional anatomical description. A...
Article

Deep temporal branches

The deep temporal arteries (anterior and posterior) are branches from the second part of the maxillary artery. They ascend between the temporalis muscle and the pericranium supplying the overlying muscle. The anterior branch communicates with the lacrimal artery by means of smal...
Article

Dehiscence

Dehiscence is a general term referring to 'splitting open' and is used in a variety of contexts in medicine generally and radiology more specifically.  The two most common usages are: splitting open of a wound (e.g. sternal dehiscence) loss of bone separating one structure from another (e.g. ...
Article

Dehiscent jugular bulb

Dehiscent jugular bulbs are present when the sigmoid plate between a high riding jugular bulb and the middle ear is absent, allowing the wall of the jugular bulb to bulge into the middle ear cavity. Clinical presentation It is one of the causes of pulsatile tinnitus and is a common cause of a ...
Article

Delphian node

The Delphian node (prelaryngeal) along with paratracheal nodes, pretracheal nodes, perithyroidal nodes make up level VI and not routinely excised in radical neck dissection. Involvement of this node can be as a result of diffuse nodal involvement in SCC (H&N) as in case 1, or in isolation f...
Article

Dental abscess

Dental (periapical) abscess is an acute infection of the periapical tissue around the root of the tooth. Clinical presentation Patients may present with pain, oedema and purulent discharged localised to the site of pathology with or without fever and tender cervical lymphadenopathy 1. Patholo...
Article

Dentigerous cyst

Dentigerous cysts, also called follicular cysts, are slow growing benign and non-inflammatory odontogenic cysts that are thought to be developmental in origin. On imaging, they usually present as a well-defined and unilocular radiolucency surrounding the crown of an unerupted or impacted tooth ...
Article

Denver criteria for blunt cerebrovascular injury

The Denver criteria are a set of screening criteria for blunt cerebrovascular injury (BCVI) used to reduce the need for CT angiography and its associated radiation exposure.  The screening protocol criteria 1,3 for BCVI are divided into signs and symptoms of BCVI and risk factors.  Signs and s...
Article

Depressed skull fracture

Depressed skull fractures result in the bone of the skull vault being folded (depressed) inward into the cerebral parenchyma. It is usually the result of a high energy impact to the skull. Pathology These mostly (~75%) occur in the frontoparietal region 3. Associations There are number of as...
Article

Dermolipoma

The dermolipoma is one of the fat-containing epibulbar mass lesions of lateral canthal area beneath the temporal or superotemporal bulbar conjunctivae. Epidemiology  Dermolipomas are congenital and more commonly seen in young patients with mean age of 30 years old. There is no gender predilect...
Article

Developmental orbital cysts

Developmental orbital cysts correspond to a heterogeneous group of congenital orbital developmental anomalies with cystic component, ranging from closed sacs lined by an ectodermal epithelium, such as epidermoid and dermoid, to neoplasms as teratoma 1.    choristoma: it is formed by heterotopic...
Article

Deviated nasal septum

A deviated nasal septum is a common incidental finding seen on brain and paranasal sinus CT studies. Pathology Aetiology It can be congenital or acquired. The most common acquired cause is trauma from motor vehicle accidents, sports-related injuries, and altercations. Associations Deviated ...
Article

Diabetes insipidus

Diabetes insipidus (DI) is the deficiency or resistance to the hormone vasopressin (antidiuretic hormone), which results in polyuria and polydipsia.  Epidemiology DI occurs in 3 per 100,000 people 2.  Pathology DI may be described as 1-3: central/neurogenic/hypothalamic: vasopressin deficie...
Article

Differential diagnosis for calcified masses in the mandible

Differential diagnosis for calcified masses in the mandible includes: calcifying odontogenic cyst (Gorlin cyst) calcifying epithelial odontogenic tumour (Pindborg tumour) fibrous dysplasia foreign body odontoma cemento-ossifying fibroma osteoma synovial osteochondromatosis focal sclero...
Article

Differential diagnosis of adult cervical lymphanopathy

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

Differential diagnosis of paediatric cervical lesions

The differential diagnosis of paediatric cervical lesions is commonly encountered in practice, unfortunately the list is long.  Differential diagnosis Inflammatory Most lesions tend to be inflammatory 3 nontuberculous lymphadenitis scrofula sialodochitis abscess infected branchial cleft...
Article

Differential diagnosis of petrous apex lesions

There is a wide differential diagnosis of petrous apex lesions: asymmetrical marrow petrous apex cephalocoele 4 petrous apicitis congenital cholesteatoma  cholesterol granuloma: most common cystic appearing lesion 3 mucocoele of petrous apex 2 benign tumours meningioma schwannoma malig...
Article

Digastric line

The digastric (or biventer) line has been described and used to evaluate basilar invagination on frontal skull plain film and coronal recontructed CT image.  The digastric line is drawn between right and left digastric grooves. The tip of the odontoid process and atlanto-occipital joint normall...
Article

Digastric muscle

The digastric muscle is composed of two bellies, anterior and posterior, connected by an intermediate round tendon. The two bellies of the muscle have different embryonic origins and hence are supplied by different cranial nerves. Summary origin anterior belly: mandible posterior belly: mast...
Article

Disc herniation

Disc herniation refers to displacement of intervertebral disc material beyond the normal confines of the disc, but involving less than 25% of the circumference (to distinguish it from a disc bulge. A herniation may contain nucleus pulposus, vertebral endplate cartilage, apophyseal bone/osteophyt...
Article

Dolichoectasia

The term dolichoectasia means dilated and elongated. It is used to characterise arteries that have shown a significant deterioration of their tunica intima (and occasionally the tunica media), weakening the vessel walls and causing the artery to elongate and distend. Epidemiology Dolichoectasi...
Article

Dorello canal

Dorello canal channels the abducens nerve (CN VI) from the pontine cistern to the cavernous sinus.  Gross anatomy Dorello canal is found at the medial most end of the petrous ridge at the confluence of the inferior petrosal sinus, basal sinus and cavernous sinus. Boundaries superiorly: petro...
Article

Double disc sign

Thickening of the insertion of the lateral pterygoid muscle can mimic an anterior displaced TMJ disc. When both thickening of the inferior belly insertion and an anteriorly displaced disc are present, the two structures parallel each other; the so called "double disc" sign.
Article

Duct of Rivinus

The duct of Rivinus connects the sublingual gland to the floor of the mouth. Despite its name, it is not a single duct, but numerous small ducts all of which open into the floor of the mouth and are collectively termed the duct of Rivinus. The largest of these little ductules is the major duct...
Article

Ducts of the salivary glands

The ducts of the salivary glands allow the passage of salivary juice from the glands to the oral cavity: parotid duct (Stenson duct): connects the parotid gland to the buccal mucosa, adjacent to maxillary second molar submandibular duct (Wharton duct): connects the submandibular gland to the f...
Article

Dysphagia

Dysphagia refers to subjective awareness of difficulty or obstruction during swallowing. It is a relatively common and increasingly prevalent clinical problem.  Fluoroscopy is the mainstay of imaging assessment but manometry can help evaluate the esophageal motor pattern and lower esophageal sp...

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