Malignant salivary gland tumours are staged using the TNM staging system:
Tx: primary tumour cannot be assessed
T0: no evidence of primary tumour
less than or equal to 2 cm in maximal diameter
no extra-parenchymal extension
2-4 cm in maximal diameter
The malleus is the most lateral middle ear ossicle, located between the tympanic membrane and the incus.
The malleus has a head, neck, and three distinct processes (manubrium (handle), anterior and lateral processes).
The head is oval in shape, and articulates posteriorly with t...
The mandible is the single midline bone of the lower jaw. It consists of a curved, horizontal portion, the body, and two perpendicular portions, the rami, which unite with the ends of the body nearly at right angles (angle of the jaw). It articulates with both temporal bones at the mandibular fo...
The mandibular canal is located within the internal aspect of the mandible and contains the inferior alveolar nerve, artery and the vein. It starts at the mandibular foramen, on the lingual side of the ramus, continues on buccal surface of body of the mandible and ends at the mental foramen, adj...
The mandibular foramen or inferior alveolar foramen is located on the medial surface of the ramus of the mandible and is the entrance to the mandibular canal. It transmits the inferior alveolar nerve, a branch of the posterior division of the mandibular division of the trigeminal nerve that supp...
The mandibular fossa or glenoid fossa is the smooth concave articular surface formed by both the squamous and petrous parts of the temporal bone. It forms the superior articular part of the temporomandibular joint and lodges the condyle of mandible.
Mandibular fractures are relatively common especially among young men. Although traditionally the mandible and base of skull are thought to form a complete bony ring, interrupted only by the TMJs. This should mean that the mandible should fracture in two places (akin to the bony pelvis) making s...
Mandibular lesions are myriad and common. The presence of teeth results in lesions that are specific to the mandible (and maxilla) and a useful classification that defines them as odontogenic or non-odontogenic. While it may often not be possible to make a diagnosis on imaging alone, this classi...
Mandibular osteoradionecrosis (ORN) is more common after radiation therapy for head and neck malignancies due to the superficial position of the mandible, which exposes it to high radiation. The maxilla can also be involved, but this is less frequent.
Mandibular ORN may occur in ...
There are many causes for mandibular periostitis:
Langerhans cell histiocytosis
malignancy (both primary and metastatic)
necrosis, e.g. radiation osteonecrosis
Garre's sclerosing osteomyelitis
Mandibular tori are common benign outgrowths of bone from the inner surface of the mandible.
They are composed of compact bone, densely mineralized usually without medullary cavity, and arise from the inner surface of the mandible above the origin of mylohyoid. They are usually bilateral.
Marine-Lenhart syndrome refers to a variant of Graves disease where there are coexistent autonomous thyroid nodules. It is better described as Graves disease with coexistent multinodular goitre or nodular Graves disease 1.
The syndrome is rare with reported prevalence somewhere b...
Marjolin ulcers reflect malignant degeneration within pre-existing scars or areas of chronic inflammation such as burns, venous ulcers etc.
The Markowitz and Manson classification system categorises fractures of the naso-orbitoethmoid (NOE) complex as follows 1:
type I - in which the medial canthal tendon is intact and connected to a single large fracture fragment
type II - the fracture is comminuted, and the medial canthal tendon...
The Martini glass sign describes the appearance of the globe in persistent hyperplastic primary vitreous (PHPV).
On MRI the retrolenticular tissue characteristic of this condition has a triangular shape, like that of a martini glass appearing as low T2 low signal against the normal high T2 sign...
The masseteric artery is a small branch from the second part of the maxillary artery. It passes laterally through the mandibular notch to the deep surface of the masseter muscle. It supplies the muscle, and anastomoses with the masseteric branches of the external maxillary and with the transvers...
The masseteric nerve or nerve to masseter is a motor branch of the anterior division of the mandibular division of the trigeminal nerve.
The masseteric nerve divides off the anterior division and continues lateral to the lateral pterygoid muscle and then medially through the mand...
The masseter muscle is one of the muscles of mastication. It is rectangular shaped and consists of three layers of fibres, where the superficial layer is the largest.
origin: zygomatic arch
insertion: ramus and angle of mandible
innervation: masseteric nerve from the anterior divisio...
The masticator space is one of the deep compartments of the head and neck.
The masticator space are paired suprahyoid cervical spaces on each side of the face. Each space is enveloped by the superficial (investing) layer of the deep cervical fascia.
The superficial layer of dee...
The mastoid air cells (cellulae mastoideae) represent the pneumatisation of the mastoid part of the temporal bone and are of variable size and extent.
At the superior and anterior part of the mastoid process the air cells are large and irregular and contain air, but toward the i...
Ths mastoid canaliculus arises from pars vascularis of foramen jugulare and runs to the mastoid segment of facial nerve canal and contains Arnold nerve (auricular branch of vagus nerve).
Mastoidectomy is a fairly frequent procedure performed for a variety of temporal bone pathologies including mastoiditis and cholesteatoma. It involves removing part of the bony wall of the mastoid to aid in drainage and surgical excision.
Types of mastoidectomy
A number of procedures have been...
The mastoid foramen is a variably present foramen as well as being variable in its size, number and position. Most commonly, it is located near the posterior margin of the mastoid process, within the temporo-occipital suture.
It transmits the emissary veins connecting to the sigmoid sinus and a...
The mastoid part of the temporal bone is its posterior component.
The mastoid part is normally pneumatised by the mastoid air cells and is perforated by the mastoid foramen. The roof of the mastoid antrum, which separates the mastoid from the cranial cavity, is called the tegment...
The maxilla (or maxillary bones) is a pair of symmetrical bones joined at the midline, which forms the middle third of the face. It forms the floor of the nasal cavity and parts of its lateral wall and roof, the roof of the oral cavity, contains the maxillary sinus, and contributes most of the i...
Maxillary antral carcinomas are an uncommon head and neck malignancy. They usually present late despite growing large since they remain confined to the maxillary sinus and produce no symptoms.
Most commonly affects patients over 45 and has a strong male predilection (M:F = 5:1). M...
The (internal) maxillary artery is the larger of the two terminal branches of the external carotid artery.
Origin and course
The maxillary artery's origin is behind the neck of the mandible, at first, it is embedded in the substance of the parotid gland. From there it passes anterior between ...
The maxillary line is a mucosal projection along the lateral nasal wall corresponding to lacrimomaxillary suture externally. The midportion of the line is called "M point". During endoscopic sinus and orbital procedures the maxillary line and M-point are very important and useful landmarks in pa...
The maxillary ostium or maxillary hiatus is an opening that forms the drainage channel of the maxillary sinus and is also one of the components of the ostiomeatal unit. It is located posteriorly and medially near the roof of the maxillary sinus measuring approximately 2-4 mm. It drains into the ...
The maxillary sinus (or antrum of Highmore) is a paired pyramid-shaped paranasal sinus within the maxillary bone which drains via the maxillary ostium into the infundibulum, then through hiatus semilunaris into the middle meatus. It is the largest of the paranasal sinuses.
Maxillary tori are analogous to mandibular tori and are composed of densely mineralised bone usually devoid of a medullary cavity. Unlike in the mandible, where they arise on the inner surface, when arising from the maxilla they may project both inwards (in which case they arise from the midline...
The McGill Thyroid Nodule Score (MTNS) is a scoring system developed to estimate the risk of malignancy of thyroid nodules.1
The MTNS is based on 22 parameters:
eight clinical or laboratory parameters
gender (male): 1 point
age (>45 years old): 1 point
palpable nodule (prese...
McRae line is a radiographic line drawn on a lateral skull radiograph or midsagittal section of CT or MRI, joining the basion and opisthion.
Normal position of the tip of dens is 5mm below this line. If the tip of the dens migrates above this line it indicates the presence of basilar invaginati...
Meckel cave lesions are numerous. The aim of this article is to list them in an easy way for revision and assessment of differential diagnosis.
Meckel cave tumours account for only 0.5% of all intracranial tumours. The most common histologies include:
trigeminal schwannoma: most c...
Medial canal fibrosis is characterised by fibrous tissue formation in the medial part of the bony external auditory canal.
Patients can present with conductive hearing loss, otorrhea and/or a history of chronic otitis.
a thickened tym...
The medial pterygoid muscle is one of the muscles of mastication.
The medial pterygoid muscle is a thick and square shaped muscle. It has two heads of origin. The deep head is the major component of the origin and is attached to the medial aspect of the lateral pterygoid plate o...
The medial rectus muscle is one of the 6 extra-ocular muscles that control eye movements.
innervation: inferior branch of the oculomotor nerve (CN III)
origin: Annulus of Zinn (tendinous ring)
insertion: globe (anterior, medial surface)
primary function: one of three ocular adductor...
A useful mnemonic to remember the bones forming the medial wall of the orbit is:
My Little Eye Sits (in the orbit)
M: maxilla (frontal process)
E: ethmoid (lamina papyracea)
S: sphenoid (body)
Medical devices in the neck are regularly observed by radiologists on plain film and CT reporting. They include devices which pass through the neck onto the chest and stomach.
Vascular access devices
peripherally inserted central catheters (PICC)
central venous catheters
Medication-related osteonecrosis of the jaw (MRONJ) describes the bony destruction of the jaw with exposed bone present for greater than eight weeks in the presence of current or previous antiresorptive and/or antiangiogenic medication use, and in the absence of radiation therapy to the head and...
Medullary thyroid carcinoma (MTC) is a subtype of thyroid cancer which accounts for 5-10% of all thyroid malignancies. It occurs both sporadically (80%) and as a familial form (see associations).
In non-familial case, it typically peaks in the 3rd to 4th decades.
Melanotic neuroectodermal tumour of infancy (MNTI) is a rare pigmented tumour that primarily affects the calvaria or facial skeleton of children, typically during infancy. It is usually a benign tumour, albeit locally aggressive.
Most cases are diagnosed during infancy, usually wi...
Melioidosis is an infectious disease caused by Burkholderia pseudomallei (previously known as Pseudomonas pseudomallei) and is a multisystem disorder which may affect the lungs, brain, visceral organs, or musculoskeletal system.
Melioidosis is a disease of the monsoon season in th...
Melkersson-Rosenthal syndrome (MRS), also known as cheilitis granulomatosa or Miescher-Melkersson-Rosenthal Syndrome, is a rare condition of unknown aetiology characterised by:
granulomatous inflammation of the face and lips (non-caseating)
facial nerve (CN VII) paralysis (involvement of crani...
Ménière disease (or idiopathic endolymphatic hydrops) is an inner ear disorder and as such can affect balance and hearing.
One or both ears can be affected. The chief symptoms are:
vertigo (often attacks which can be incapacitating)
a sensation o...
The mental artery is a terminal branch of the inferior alveolar artery which itself is a branch of the first part of the maxillary artery. It emerges onto the face from the mandibular canal with the mental nerve at the mental foramen, and supplies muscles and skin in the chin region. The mental ...
The mental foramen is a small foramen on the anterior surface of the mandible, typically adjacent to the root of the mandibular second premolar tooth. Normal variants have the forman located anywhere between the canine and 1st molar.
The mental nerve, a terminal branch of inferior alveolar nerv...
The mental nerve is one of the two terminal branches of the inferior alveolar nerve, a branch of the posterior division of the mandibular division of the trigeminal nerve. It emerges from the mandibular canal anteriorly through the mental foramen and supplies the labial gingiva of the lower lip ...
A mesiodens is the most common supernumerary tooth and is located in the palatal midline between the two maxillary central incisors.
It is rare with an estimated prevalence of ~1% (range 0.09 to 2.2%) 3. There is an increased male predilection with a M F ratio of ~2.5:1.
The mesotympanum forms the main compartment of the tympanic cavity and contains most of the important structures of the middle ear, including most of the ossicular chain.
The mesotympanum is found in the middle ear.
Superiorly it is arbitrarily separated f...
Metastases to the thyroid are an uncommon cause of thyroid malignancy.
Metastases to the thyroid represent 1.4-3% of all malignancies 5. In autopsy series, the incidence is ~10% (range 2-24%) 1,5.
The most common sites of primary malignancy include (note these will v...
Meth mouth is the name given to the overt dental disease that is one of the signs of methamphetamine use.
Clinical examination often reveals blackened, stained, rotting or crumbling teeth. Serial studies only a few years apart may show a striking deterioration in the pati...
The metopic suture (also known as the median frontal suture) is a type of calvarial suture. It is often associated with frontal sinus agenesis or hypoplasia 7.
This suture runs through the midline across the frontal bone from the nasion to the bregma, although it may often be in...
MIBG scan is a scintigraphic study that uses metaiodobenzylguanidine labeled to iodine-123 or iodine-131. It is indicated in the investigation of phaeochromocytoma.
MIBG is positive in:
olfactory neuroblastoma 1
carcinoid tumour 4
Michel aplasia, also known as complete labyrinthine aplasia (CLA), is a congenital abnormality of the inner ear and is characterised by bilateral absence of differentiated inner ear structures with resultant anacusis. It should not be confused with Michel dysplasia.
Michel aplasia i...
Microgenia is a term meaning a small chin. It is somewhat related to but distinct from the term micrognathia which means a small mandible.
Microgenia can be isolated or be associated with a numer of anomalies which include
camptomelic dysplasia 1
Microphthalmia essentially means small eyes. It is characterised by a small eye within a small orbit. It can be unilateral or bilateral. It is sometimes defined as a globe with a total axial length (TAL) that is at least two standard deviations below the mean for age.
Microtia refers to a small pinna of the ear, when is it completely absent it is termed anotia.
The estimated incidence at around 1:9000 live births. It is more common in males and there is a recognised right sided predilection.
Microtia can be associated ...
The middle cranial fossa is a butterfly-shaped depression of the skull base, which is narrow in the middle and wider laterally. It houses the temporal lobes of the cerebrum.
The middle cranial fossa can be divided into medial and lateral parts. In the medial part, the following s...
The middle ear (a.k.a. tympanic cavity or tympanum) is an air-filled chamber in the petrous part of the temporal bone. It is separated from the external ear by the tympanic membrane, and from the inner ear by the medial wall of the tympanic cavity. It contains the three auditory ossicles whose p...
Middle ear effusions are frequent in children due to prominent adenoids and horizontal Eustachian tubes. These do not require imaging, and can be treated expectantly / medically / surgically with gromits. Eustachian tube dysfunction is the accepted aetiology, with resorption of air and extravasa...
Development of granulation tissue in the middle ear cavity is a generalised response to injury/inflammation, chronic otomastoiditis. It can either be typical or go down the pathway of becoming a cholesterol granuloma.
Typical granulation tissue is common, more so than cho...
There are three ossicles (from lateral to medial):
Their role is to mechanically amplify the vibrations of the tympanic membrane and transmit them to the cochlea where they can be interpreted as sound. They are located in the middle ear cavity and articulate with each ot...
There are a range of middle ear tumours, which are more likely to be benign than malignant.
The three most common middle ear tumours are (not in any particular order as there are differences in the literature) 1-3:
glomus tympanicum paraganglioma
The middle meatus is an air passage of the lateral nasal cavity located between the middle nasal concha and lateral nasal wall. The anterior ethmoid air cells, maxillary and frontal sinuses all drain into the middle meatus.
The middle meningeal artery branches off the first part of the maxillary artery. It passes vertically through the roots of the auriculotemporal nerve and enters the middle cranial fossa via the foramen spinosum. Here it gives off two branches - superior tympanic branch and ganglionic branch - be...
The middle nasal conchae or turbinates are one of the pairs of conchae in the nose.
The middle nasal concha consists of the medial surface of the labyrinth of ethmoid which is a thin lamella that descends from the undersurface of the cribriform plate and ends in a free, convolute...
The middle pharyngeal constrictor muscle is one of the pharyngeal constrictor muscles. Its primary action is constricting of the pharynx (in coordination with the superior pharyngeal constrictor and the inferior pharyngeal constrictor muscles) to deliver a bolus of food into the oesophagus.
The middle superior alveolar nerve, also known as the middle superior dental nerve, is the second branch of the infra-orbital nerve, from the maxillary division of the trigeminal nerve. It is the smallest of the superior alveolar nerves and contributes to the superior dental plexus.
The middle thyroid vein is a tributary of the internal jugular vein.
Origin and course
The middle thyroid vein arises from the lateral surface of the thyroid. It traverses laterally to the internal jugular vein, passing anterior to the common carotid artery and posterior to the ...
The middle meningeal nerve (which is also known as the meningeal branch of the maxillary nerve) is a branch of the maxillary division of the trigeminal nerve which supplies the dura of the middle cranial fossa.
The nerve divides off the maxillary division just before the foramen ...
Midfacial hypoplasia is a type of congenital facial anomaly and can be feature of a number of congenital syndromic anomalies. These include:
chromosome 1p36 deletion syndrome 2
chromosome 18q deletion syndrome
fetal alcohol syndrome
fetal valproate s...
A variety of congenital midface anomalies occur in children. Although rare, these disorders are clinically important because of their potential for connection to the central nervous system. Lesions presenting as a midline nasal mass include:
nasal dermoid cyst...
Midline neck masses have a relatively narrow differential, as few structures are present in the midline. Dividing the causes according to structure of origin is a useful schema.
lymph node(s): Delphian node(s)
thyroglossal duct cyst
Mikulicz syndrome was considered a form of Sjögren syndrome (type 1) however more recently it is considered in IgG4 related disease spectrum. It is a non-specific inflammatory enlargement of at least two or more of the salivary and lacrimal glands with xerostomia.
It may also be referred to b...
Minor salivary glands are a subset of the salivary glands. They are small and unnamed salivary glandular tissue scattered throughout the oral cavity and oropharynx as well as more widely in the mucosa of the aerodigestive tract.
They number in the hundreds and are important because salivary gl...
Minor salivary gland tumours are a subtype of salivary gland tumours originating from the minor salivary glands, which are found in the lips, tongue, hard palate, and the mucosa of the oropharynx and larynx, among other locations.
MSGTs account for ~15% of all salivary gland tumou...
Mixed temporal bone fractures are a combination of longitudinal and transverse fracture types, and are probably the most common type. They frequently involve the otic capsule, and are associated with both conductive and sensorineural hearing loss.
The modified Memphis criteria are a set of screening criteria for blunt cerebrovascular injury (BCVI) in trauma. The presence of one or more of these criteria makes necessary a complementary CTA or DSA study to exclude a BCVI.
The screening protocol criteria for BCVI are:
base of skull fractur...
The modified Stenvers view is an oblique radiographic projection used to demonstrate the petrous temporal bone, IAM and bony labyrinth. It is primarily used to assess electrode placement following the insertion of a cochlear implant. Specifically it assesses the:
integrity, positioning, and dep...
The cochlear modiolus is a conical-shaped structure that consists of spongy (porous) bone located in the center of the cochlea which contains the spiral ganglion.
The spiral lamina projects from the modiolus.
Abnormality of the modiolus results in sensorineural hearing loss.
History and etymo...
Mondini malformation is a historical term used to described incomplete partition type II anomaly with large vestibular aqueduct.
The term is often used inappropriately to describe any cochlear abnormality, rather than a specific type of cochlear hypoplasia. Thus, most would favour ...
Morning glory disc anomaly (MGDA),also known as morning glory syndrome, is a rare congenital malformation of the optic nerve which is frequently associated with midline abnormalities of the brain and skull 1.
Morning glory disc anomaly is rare and is more commonly found in females...
A mucocele simply refers to accumulation and expansion of a structure by mucus. It occurs in a variety of locations which are discussed separately:
paranasal sinus mucocele
oral cavity e.g. ranula, mucous retention cysts
mucocele of the appendix 1
mucocele of the gallbladder
mucocele of the...
Mucoepidermoid carcinoma is a tumour that usually occurs in the salivary glands. It can mimic most other tumours of the glands, and therefore is often considered in the differential.
Mucoepidermoid carcinomas are seen throughout all adult age groups, but are most common in middle...
Multinodular goitre (commonly abbreviated to MNG) is defined as an enlarged thyroid gland (i.e. goitre) due to multiple nodules which may have normal, decreased or increased function.
When increased activity and hyperthyroidism are present then the condition is referred to a toxic...
Multiphase CT angiography is an evolving imaging technique in acute ischaemic stroke. The technique aims to quickly and reliably identify brain which is potentially salvageable with intervention. Brain tissue viability depends on many factors, with this technique assessing collateral leptomening...
The differential diagnosis for multiple cystic neck lesions is different to that for a solitary cystic neck mass.
Cystic neck lesions are seen in:
necrotic metastatic SCC nodes: older patient, M>F
papillary thyroid carcinoma metastases: usually a younger patient, F>M
Multiple endocrine neoplasia (MEN) syndromes are a collection of syndromes characterised by the presence of, as the name would suggest, multiple endocrine tumours. They are autosomal dominant in inheritance.
MEN1 (Wermer syndrome)
MEN2 (multiple endocrine adenomatosis)
MEN2a (Sipple syndrome)...
Multiple endocrine neoplasia type I (MEN1), also known as Wermer syndrome, is an autosomal dominant genetic disease that results in proliferative lesions in multiple endocrine organs, particularly the pituitary gland, islet cells of the pancreas and parathyroid glands.
There are other multiple...
Multiple endocrine neoplasia type II (MEN2) is also known as mucosal neuroma syndrome or multiple endocrine adenomatosis. It is a collection of syndromes characterised by the presence of multiple endocrine tumours.
They are autosomal dominant in inheritance, and share medullary thyroid carcino...
Multiple endocrine neoplasia (MEN) type IIa, also known as Sipple syndrome, accounts for most cases of MEN2 and is characterised by:
pheochromocytomas: in 50% of patients, often bilateral, and can be extra-adrenal
medullary thyroid cancer: 100% of patients, aggressive, and may secrete calciton...
Multiple endocrine neoplasia (MEN) type IIb, also known as MEN type 3 (MEN3) 3 or mucosal neuroma syndrome 2, accounts for only 5% cases of MEN2 and is characterised by:
pheochromocytoma(s): in 50% of patients, often bilateral, and can be extra-adrenal
medullary thyroid cancer: 100% of patient...