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

Nasal bone

The nasal bones are paired oblong upper central facial bones placed side by side between the frontal processes of the maxilla, jointly forming the nasal ridge. Gross anatomy The nasal bones has two surfaces: external surface attaches the procerus and nasalis muscles internal, which is transv...
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Nasal bone fracture

Nasal bone fractures are the most common type of facial fractures, accounting for ~45% of facial fractures, and are often missed when significant facial swelling is present.  Clinical presentation Unsurprisingly, nasal bone fractures occur when the nose impacts against a solid object (e.g. fis...
Article

Nasal cavity

The nasal cavity forms part of the aerodigestive tract. Gross anatomy The nasal cavity is formed by 1: anteriorly: nasal aperture laterally: inferior, middle and superior nasal conchae or turbinates superiorly: cribiform plate of the ethmoid bone inferiorly: palatal processes of the maxill...
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Nasal concha

The nasal conchae are long, narrow curled shelves of bone that protrude into the nasal cavity. The superior, middle and inferior conchae divide the nasal cavity into three groove-like air passages. The conchae are located laterally in the nasal cavity and covered by pseudostratified columnar, c...
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Nasal encephalocoele

Nasal encephalocoeles are the herniation of cranial content in the nasal area. It is one of the causes of craniospinal dysraphism. Clinical presentation Nasal encephaloceles usually present at birth with symptoms of obstruction or other complications. It presents as an external swelling on the...
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Nasal glioma

Nasal gliomas, also know as nasal glial heterotopia, are a rare congenital lesion composed of dysplastic glial cells which have lost their intracranial connections and present as an extranasal or intranasal mass.  Epidemiology Nasal gliomas are rare congenital lesions. These masses occur spora...
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Nasal septal perforation

Nasal septal perforation may affect either the bony, or cartilaginous septum. Most commonly it affects the anterior septal cartilaginous area although with syphilis it characteristically affects the bony septum. Clinical presentation Symptoms include a nasal discharge, nasal congestion (loss o...
Article

Nasal septum perforation (mnemonic)

A not-very-useful mnemonic for the causes of nasal septum perforation is: Say Water Coke Syrup Sugarwater Lemonade or Say Nothing  Mnemonic S: saracoidosis W: Wegener granulomatosis C: cocaine S: syphilis S: surgery L: leprosy or say N: non-Hodgkin T-cell lymphoma (NHL)
Article

Nasion

The nasion is the midline bony depression between eyes where the frontal and two nasal bones meet, just below the glabella. It is also known as the bridge of the nose. It is one of the skull landmarks, craniometric points for radiological or anthropological skull measurement.
Article

Naso-orbitoethmoid (NOE) complex fracture

Naso-orbitoethmoid (NOE) fractures (also known as orbitoethmoid or nasoethmoidal complex fractures) are fractures which involve the central upper midface. Pathology Naso-orbitoethmoid (NOE) fractures are caused by a high-impact force applied anteriorly to the nose and transmitted posteriorly t...
Article

Nasolabial cyst

Nasolabial cyst (also known as nasoalveolar cyst or Klestadt`s cyst) is a rare non-odontogenic, soft-tissue, developmental cyst occurring inferior to the nasal alar region. The cyst is derived from epithelial cells retained in the mesenchyme after fusion of the medial and lateral nasal processes...
Article

Nasolacrimal drainage apparatus

The nasolacrimal (drainage) apparatus consists of: lacrimal canaliculi lacrimal sac nasolacrimal duct Tears produced by the lacrimal gland, accessory lacrimal glands of Krause Wolfring and Zeis, and Meibomian glands track medially along the eyelid margins and collect at the lacrimal lake at ...
Article

Nasolacrimal duct

The nasolacrimal duct is the terminal part of the nasolacrimal apparatus. Gross anatomy Then nasolacrimal duct is the inferior continuation of the lacrimal sac and is ~17 mm in length in total. There are two parts to the nasolacrimal duct: intraosseous part (12 mm): lies within nasolacrimal c...
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Nasolacrimal tumours

Nasolacrimal tumours, in other words tumours involving the nasolacrimal drainage apparatus, are uncommon, and have a variety of histologies. Clinical presentation Clinical presentation of nasolacrimal tumours are typically fairly non-specific, often resulting in delayed diagnosis 1. Typical pr...
Article

Nasomaxillary suture

This suture forms the fissure between the frontal process of maxilla and the lateral border of the nasal bone. The nasomaxillary sutures are paried.
Article

Nasopalatine nerve

The nasopalatine nerve (also known as the long sphenopalatine nerve) is a branch of the pterygopalatine ganglion. Gross anatomy Course exits the pterygopalatine ganglion in the pterygopalatine fossa passes through the sphenopalatine foramen to enter the nasal cavity passes along the roof of...
Article

Nasopharyngeal carcinoma

Nasopharyngeal carcinomas (NPC) are the most common primary malignancy of the nasopharynx. It is of squamous cell origin and some types of which are strongly associated with Epstein Barr virus (EBV). Epidemiology Nasopharyngeal carcinomas account for ~70% of all primary malignancies of the nas...
Article

Nasopharyngeal carcinoma staging

Nasopharyngeal carcinoma is staged using the TNM staging system with derived stage groupings.  TNM staging Primary tumour (T) Tx: primary tumour cannot be assessed T0: no evidence of primary tumour Tis: carcinoma in situ T1: tumour is confined to the nasopharynx T2: tumour extends to soft...
Article

Nasopharyngeal choristoma

A nasopharyngeal choristoma is a rare, non-neoplastic mass (type of choristoma) typically located in the lateral aspect of the nasopharynx without intracranial extension. These lesions are composed of fibrovascular tissue and fat. Resection is curative. Differential diagnosis nasopharyngeal ca...
Article

Nasopharyngeal mass (mnemonic)

A mnemonic for causes of nasopharyngeal masses is: SAIL Mnemonic S: squamous cell carcinoma A: antrachoanal polyp I: inverted papilloma L: lethal midline granuloma
Article

Nasopharynx

The nasopharynx forms part the pharynx, being the continuation of the nasal cavity superiorly, and the oropharynx inferiorly.  Gross anatomy Boundaries anteriorly: posterior nares and posterior margin of nasal septum 1,2 inferiorly: soft palate 2 superiorly: basi-sphenoid and basi-occiput 1...
Article

Neck dissection classification

There are several types of neck dissections which can classified as follows: Radical neck dissection Radical neck dissection is considered to be the standard basic procedure for cervical lymphadenectomy. All other procedures represent one or more alterations of this procedure. The dissection i...
Article

Necrotising otitis externa

Necrotising otitis externa (NOE), also known as malignant otitis externa, is a severe invasive infection of the external auditory canal (EAC) which can spread rapidly to involve the surrounding soft tissue, adjacent neck spaces and skull base.  Pathology Predisposing conditions for NOE include...
Article

Nerve to stapedius

The nerve to stapedius arises from the facial nerve to supply the stapedius muscle. The facial nerve branch is given off in its mastoid segment, as it passes posterior to the pyramidal process. Damage to this branch with resulting paralysis of stapedius leads to hypersensitivity to loud noises ...
Article

Neuroblastoma: craniocerebral metastases

Craniocerebral neuroblastoma metastases usually involve the calvaria, orbits, skull base and the dura. Please refer to the article neuroblastoma for a general discussion on this entity.  Clinical presentation proptosis periorbital ecchymosis "raccoon eyes" palpable calvarial masse...
Article

Neurofibromatosis type 1: orbital manifestations

Orbital manifestations of neurofibromatosis type 1 (NF1) reflects a mix of CNS, musculoskeletal and ocular disease. Usually only one orbit is affected, commonly associated with ipsilateral extracranial disease. Pathology NF1 manifests in the orbit in the following ways 1-5: plexiform neurofib...
Article

Non-decussating retinal-fugal fibre syndrome

Non-decussating retinal-fugal fibre syndrome (NRFFS), also referred to as achiasma, is the isolated congenital absence of optic chiasm with unremarkable rest of the optic pathway and midline structures. Clinically, it typically presents as seesaw nystagmus since childhood. Diagnosis is usually m...
Article

Normal bone marrow signal of the clivus

Bone marrow signal of the clivus changes predictably with age and is well assessed with midline T1 non-fat saturated, non-contrast images. As is seen in the rest of the body the proportion of yellow (fatty) marrow increases with age. Knowledge of these changes allows diagnosis of the abnormal cl...
Article

Normal head and neck imaging examples

This article lists examples of normal imaging of the head and neck and surrounding structures, divided by region and modality. Neck For normal spinal imaging, please see: normal spinal imaging Plain radiographs soft tissue: example 1 soft tissue: example 2 CT soft tissue contrast: exampl...
Article

Norrie disease

Norrie disease is a rare X-linked inherited cause of congenital bilateral blindness. It can present with a retinal mass (pseudoglioma) and cataracts. It is associated with developmental delay and hearing loss. 
Article

Nose

The nose, sometimes referred to as the external nose, is a feature of the face and is composed of soft tissues that extend externally from the skull. It is continuous posteriorly with the nasal cavity. Blood supply arterial supply facial artery (from external cartoid artery) with anastomoses ...
Article

Nystagmus (mnemonic)

A helpful mnemonic to remember the expected direction of nystagmus during caloric test is: COWS Mnemonic Cold-Opposite Warm-Same Following ear stimulation with water (left ear): cold water (cooler than body temperature), a right-beating nystagmus (directed toward the opposite ear) results ...

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