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.
The nasal bone has two surfaces:
external surface attaches the procerus and nasalis muscles
internal, which is transve...
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.
Unsurprisingly, nasal bone fractures occur when the nose impacts against a solid object (e.g. fis...
The nasal cavity forms part of the aerodigestive tract.
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...
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 four groove-like air passages.
The conchae are located laterally in the nasal cavity and covered by pseudostratified columnar, ci...
Nasal encephalocoeles are in most cases a form of neural tube defect particularly common in Southeast asia. They are are herniation of cranial content through a bony defect in the anterior skull base into the nasal area.
The term is variably used, but generally encompasses both frontoethmoidal ...
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.
Nasal gliomas are rare congenital lesions. These masses occur spora...
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.
Symptoms include a nasal discharge, nasal congestion (loss o...
The nasal septum (Latin: septum nasi) separates the left and right nasal cavities. It extends from the nares anteriorly to the choanae posteriorly and is covered by squamous epithelium.
The nasal septum is comprised primarily of one cartilage and two bones. Anteriorly there is the se...
A not-very-useful mnemonic for the causes of nasal septum perforation is:
Say Water Coke Syrup Sugarwater Lemonade or Say Nothing
W: Wegener granulomatosis
N: non-Hodgkin T-cell lymphoma (NHL)
The nasal sill is the soft tissue ridge forming the posterior margin of the anterior naris. It also forms the caudal margin of the nasal vestibule.
The nasal sill forms part of the nasal base, which is defined as the inferior third of the nose when viewing the nose from below with the neck exte...
The nasal vestibule forms the small area just inside the anterior naris. It is formed by the columella medially, the nasal ala lateral and anteriorly and the nasal sill posteriorly.
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.
The nasociliary nerve is the intermediate branch of the ophthalmic division of the trigeminal nerve.
The nasociliary nerve divides off the ophthalmic division just before entering the orbit through the superior orbital fissure and through the tendinous ring between the inferior a...
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...
The nasolacrimal (drainage) apparatus consists of:
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 ...
The nasolacrimal duct is the terminal part of the nasolacrimal apparatus.
The 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 the nasolacrima...
Nasolacrimal tumours, in other words tumours involving the nasolacrimal drainage apparatus, are uncommon, and have a variety of histologies.
Clinical presentation of nasolacrimal tumours are typically fairly non-specific, often resulting in delayed diagnosis 1. Typical pr...
This suture forms the fissure between the frontal process of maxilla and the lateral border of the nasal bone. The nasomaxillary sutures are paried.
The naso-orbital-ethmoid (NOE) region or interorbital region simply refers to the space between the orbits.
anterior: frontal process of the maxilla, nasal process of frontal bone, nasal bone
posterior: sphenoid sinus
lateral: medial orbital wall
Naso-orbitoethmoid (NOE) fractures (also known as orbitoethmoid or nasoethmoidal complex fractures) are fractures which involve the central upper midface.
Naso-orbitoethmoid fractures are caused by a high-impact force applied anteriorly to the nose and transmitted posteriorly through...
The nasopalatine nerve (also known as the long sphenopalatine nerve) is a branch of the maxillary division of the trigeminal nerve and contributes to the pterygopalatine ganglion.
The nasopalatine nerve divides off the maxillary division just after emerging from the foramen rotun...
Nasopharyngeal carcinomas (NPC) are the most common primary malignancy of the nasopharynx. It is of squamous cell origin, some types of which are strongly associated with the Epstein-Barr virus (EBV).
Nasopharyngeal carcinoma accounts for ~70% of all primary malignancies of the na...
Nasopharyngeal carcinoma staging uses the TNM staging system with derived stage groupings.
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 ti...
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.
A mnemonic for causes of nasopharyngeal masses is:
S: squamous cell carcinoma
A: antrachoanal polyp
I: inverted papilloma
L: lethal midline granuloma
The nasopharynx forms part of the pharynx, being the continuation of the nasal cavity superiorly, and the oropharynx inferiorly.
anteriorly: posterior nares and posterior margin of nasal septum 1,2
inferiorly: soft palate 2
superiorly: basi-sphenoid and basi-occipu...
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...
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.
Predisposing conditions for NOE include...
Necrotising sialometaplasia is a benign inflammatory condition of the salivary gland remnants or elements, which is usually self-limiting. It is most commonly found in the palate.
Most patients are more than 40 years of age, with a male:female ratio of 2:1. It is rarely seen in ...
The nerve to medial pterygoid or medial pterygoid nerve is a branch of the mandibular division of the trigeminal nerve.
The nerve to medial pterygoid divides off the mandibular division just below the foramen ovale and just before it branches into anterior and posterior divisons....
The nerve to mylohyoid or mylohyoid nerve is a motor branch of the inferior alveolar nerve, a branch of the mandibular division of the trigeminal nerve.
The nerve to mylohyoid arises from the inferior alveolar nerve just before it enters the mandibular foramen. It does not enter ...
The nerve to stapedius arises from the facial nerve to supply the stapedius muscle. The branch is given off in the facial nerve's mastoid segment, as it passes posterior to the pyramidal process.
Damage to this branch with resulting paralysis of stapedius leads to hypersensitivity to loud noise...
The nervus spinous (also known as the meningeal branch of the mandibular nerve) is a branch of the mandibular division of the trigeminal nerve which innervates the dura of the middle cranial fossa.
The nervus spinosus divides off the mandibular division just below the foramen ova...
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.
periorbital ecchymosis "raccoon eyes"
palpable calvarial masses
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.
NF1 manifests in the orbit in the following ways 1-5:
Neurosyphilis results from infection of the central nervous system by the spirochete Treponema pallidum, subspecies pallidum. The disease has a heterogeneous spectrum of early and late manifestations.
For a general discussion, and for links to other system specific manifestations, please refer ...
NEXUS (National Emergency X-Radiography Utilization Study) is a set of validated criteria used to decide which trauma patients do not require cervical spine imaging.
Trauma patients who do not require cervical spine imaging:
alert and stable
no focal neurologic deficit
no altered level of co...
The node of Rouviere is the most superior of the lateral group of the retropharyngeal lymph nodes. It is found at the base of the skull.
History and etymology
Henri Rouvière (1876–1952) was an anatomy professor from Le Bleymard in France. His seminal work, "Anatomy of the Human Lymphatic Syst...
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...
Nonsteroidal anti-inflammatory drug (NSAID) exacerbated respiratory disease or previously known as Samter syndrome or aspirin or analgesic-induced asthma refers to the constellation of 1-2:
allergy to aspirin
nasal polyposis / rhinosinusitis
In adults, prevalence can ran...
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...
This article lists examples of normal imaging of the head and neck and surrounding structures, divided by region and modality.
For normal spinal imaging, please see: normal spinal imaging
soft tissue: example 1
soft tissue: example 2
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.
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.
facial artery (from external cartoid artery) with anastomoses ...
A helpful mnemonic to remember the expected direction of nystagmus during a caloric test is:
Following ear stimulation with water (left ear):
cold water (cooler than body temperature), a right-beating nystagmus (directed toward the opposite ear) result...