Platybasia is characterised by abnormal flattening of the skull base as defined as a base of skull angle over 143º.
Platybasia alone does not usually cause symptoms unless it is associated with basilar invagination.
Persistent hypophyseal canal, also known as the craniopharyngeal canal when larger than 1.5 mm in diameter, is a rare congenital defect characterised by a communication through the central skull base between the nasopharynx and the pituitary fossa.
There are a number of terms whic...
The anterior lacrimal crest is a bony projection on the frontal process of the maxilla continuous with the orbital rim which creates the lateral margin of the lacrimal sac fossa. The medial palpebral ligament is attached to anterior lacrimal crest.
Immediately anterior to the anterior lacrimal ...
The internal palpebral arteries, or medial palpebral arteries, are branches of the ophthalmic artery, with superior and inferior medial palpebral branches arising opposite the trochlear of the superior oblique muscle.
The internal palpebral arteries enter the superior and inferio...
An oculomotor nerve palsy results in weakness of the muscles supplied by the oculomotor nerve, namely the superior rectus, inferior rectus, medial rectus, inferior oblique, and levator palpebrae superioris muscles. This leads clinically to an eye that is "down and out".
It has numero...
The spheno-occipital suture marks the spheno-occipital synchondrosis, containing the hyaline cartilage bridging the basisphenoid and basiocciput. It fuses at 12-13 years in girls and 14-15 years in boys and completely ossifies by 20-25 years.
Tornwaldt cyst (also spelled as a Thornwaldt cyst or Thornwald cyst) is a common incidental benign midline nasopharyngeal mucosal cyst.
The lesion is developmental and usually asymptomatic. In most cases it is found incidentally and as such age of diagnosis represents age of imagi...
The differential of a mass involving or arising from the clivus is a relatively narrow one and can be divided into whether the lesion arises from the skull base itself, the intracranial compartment above or the base of skull below.
When evaluating the clivus it is important to compare the marro...
Concha bullosa (plural: conchae bullosae) (also known as middle turbinate pneumatisation) is a common finding and although associated with deviation of the nasal septum, it is usually of little clinical importance.
Concha bullosa is a normal variant and is one of the most common v...
Asteroid hyalosis is a degenerative condition of the eye where there is an accumulation of calcium soaps in the vitreous chamber.
The prevalence increases with age from 0.2% in 43-54-year-olds to 2.9% in 75-86-year-olds. The overall prevalence is 1.2%. It is more commonly unilater...
Ocular metastases, also termed uveal metastases, account for over 80% of all ocular pathology, and need to be distinguished from extraocular metastasis, which are a quite different group of tumours.
This article will discuss metastatic lesions affecting the orbits. For other intracranial metast...
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...
Paranasal sinuses are air-filled cavities surrounding the nasal cavity proper which includes maxillary sinus, sphenoid sinus, frontal sinus and ethmoid sinus. Trauma to the superior and middle thirds of the face can often lead to in paranasal sinus fractures involving one or more paranasal sinus...
Frontal sinus fractures are facial fractures that involve the frontal sinus, either in isolation or more commonly as part of more complex facial fractures. They can result in cosmetic deformity, functional impairment, CSF leak, and/or intracranial infection (e.g. meningitis).
The sphenoid sinus is the most posterior paranasal sinus. It lies anteroinferior to the sella. It is important to look for the variable pneumatisation of this sinus and to report the relationship with neurovascular structures. The sinus is often divided by a central septum, and in this context s...
Vitreous haemorrhage refers to bleeding into the vitreous chamber.
Vitreous haemorrhage has an incidence of approximately 7 in 100000 1,2.
The most common clinical presentation is with sudden, painless visual loss to varying degrees of severity 2. Associated ...
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.
In nonfamilial cases it typically peaks in the 3rd to 4th decades.
Thought to arise from par...
The hiatus semilunaris is a semicircular shaped opening located on the lateral wall of the nasal cavity. It is a component of the ostiomeatal complex and serves as the opening for the frontal and maxillary sinuses and the anterior ethmoid air cells. It is inferior to the ethmoid bulla and the un...
The columella is the most anteroinferior portion of the nasal septum. It is a single midline structure composed of cartilage and overlying skin, extending posteriorly from the tip of the nose. The lateral aspects form the medial wall of each nostril.
History and etymology
From the Latin word f...
Laryngeal cysts can occur in any part of the larynx, but are more frequent in supraglottic locations, such as the epiglottis and vallecula. The prevalence of each location varies on different studies.
The laryngeal cysts represent a rare group, about 5%, of benign laryngeal lesio...
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 vertical midline nasal septum is comprised primarily of a single cartilage and two bones. Ante...
Glomus vagale tumours are glomus tumours that occur along the path of the vagus nerve (CN X). They are a subset of extra-adrenal neuroendocrine tumours that are derived from the nonchromaffin paraganglion cells.
Typically presents as a painless mass behind the carotid ar...
Salt and pepper sign or pepperpot skull of the calvarium refers to multiple tiny well-defined lucencies in the skull vault caused by resorption of trabecular bone in hyperparathyroidism.
There is a loss of definition between the inner and outer tables of the skull and a ground-glass appearance ...
Transverse temporal bone fractures are orientated perpendicular to the long axis of the petrous temporal bone, with the line of force running roughly anterior to posterior. Although more current classifications of the extent of temporal bone fractures focus on the integrity of the otic capsule r...
Melanotic neuroectodermal tumour of infancy (MNTI) is a rare pigmented tumour that primarily affects the calvarium or facial skeleton of children, typically during infancy. It is usually a benign tumour, albeit locally aggressive.
Most cases are diagnosed during infancy, usually w...
A simple mnemonic to recall a list of commonly calcifying metastases is:
B: breast cancer
T: papillary thyroid cancer
O: ovarian cancer (especially mucinous)
M: mucinous adenocarcinoma (especially colorectal carcinoma)
Oro-antral fistula (OAF) is a pathological communication between the oral cavity and the maxillary sinus (antrum).
The term oro-antral fistula is similar to but not synonymous with the term oro-antral communication (OAC). An oro-antral fistula refers to an "epithelialised" patholog...
There is a wide differential diagnosis of petrous apex lesions:
petrous apex cephalocoele 4
cholesterol granuloma: most common cystic appearing lesion 3
mucocoele of petrous apex 2
Sarcoidosis is a non-caseating granulomatous multi-system disease with a wide range of clinical and radiographic manifestations.
Individual systemic manifestations are discussed individually:
pulmonary and mediastinal manifestations
Congenital cervical teratoma refers to a teratoma arising in the cervical region. They are thought to account for ~3% of teratomas in childhood/infancy 3.
The estimated occurrence in neonates is ~1:20,000-40,000 live births 8.
Most tumours are diagnosed at ...
Lingula (plural lingulae) can refer to a number of different anatomical structures:
lingula (sphenoid bone)
History and etymology
Lingula is the diminutive form of lingua, Latin for the tongue. Thus lingula is used for a small tongue-l...
Hyrtl's fissure (also known as tympanomeningeal fissure) is a congenital infra-labyrinthic fissure. It is a very rare cause of spontaneous CSF ottorhoea and meningitis.
This fissure is present in the developing fetal petrous temporal bone and is typically ossified by 24 weeks.
The hypoglossal canal is located between the occipital condyle and jugular tubercle and runs obliquely forwards (posteromedial to anterolateral) allowing the hypoglossal nerve (12th cranial nerve) to exit the posterior cranial fossa.
Its proximal portion is often divided by a fibrous (sometime...
The vestibular line of Lapayowker refers to a vertical line passing down the most lateral aspect of vestibular apparatus. The petrous part of internal carotid artery lies medial to this line but lies lateral to it in the case of an aberrant internal carotid artery which is the characteristic ang...
The persistent stapedial artery (PSA) is an abnormal small vessel arising from the petrous portion of the internal carotid artery and crossing through the middle ear. It results from the failure of regression of the embryonic stapedial artery.
The prevalence is thought to range f...
The globes or simply, the eyes are paired spherical sensory organs, located anteriorly on the face within the orbits, which house the visual apparatus.
The globe is suspended by the bulbar sheath in the anterior third of the bony orbit.
Each globe is an approxim...
The buccal space (or buccinator space) is one of the seven suprahyoid deep compartments of the head and neck.
The buccal spaces are paired fat contained spaces on each side of the face forming cheeks. Each space is enveloped by the superficial (investing) layer of the deep cervi...
Cutis verticis gyrata is a rare progressive dermatological condition characterised by excessive skin folds in the scalp, resembling the surface of the cerebral cortex.
It occurs more commonly in males, with a male-to-female ratio of approximately 5:1 1.
Proliferating trichilemmal cysts are dermal or subcutaneous tumours with squamoid cytologic features and trichilemmal-type keratinisation usually arising in the scalp.
A variety of names have been used for this pathology, including proliferating epidermoid cyst, pilar tumour of the...
Orbital dermoid cysts are congenital lesions representing closed sacs lined by an ectodermal epithelium and comprising the most common orbital tumour in children. They are typically divided into deep (within the orbit) and superficial (adjacent to the orbital rim).
They comprise ~...
Benign enhancing foramen magnum lesions have been anecdotally seen by radiologists for years but only recently described as an incidental finding in a typical location in the foramen magnum just behind the vertebral artery. Although the precise nature of this finding has not been entirely elucid...
The epitympanum, also known as the attic or epitympanic recess, is the most superior portion of the tympanic cavity. It is that portion of the tympanic cavity superior to the axial plane between the tip of the scutum and the tympanic segment of the facial nerve 1,3.
Posteriorly the epitympanum ...
Temporomandibular joint dislocation represents the condyle of the mandible being abnormally displaced, with a loss of the normal articulation with the glenoid fossa.
Dislocations of the temporomandibular joint (TMJ) are common and occur in as many as 7% of the entire population, a...
Superior semicircular canal dehiscence syndrome (SCDS) is a recently described inner ear abnormality, where a clinical disequilibrium phenomenon is associated with the absence of the bony covering of the superior semicircular canal (SSC).
Notably, this CT finding has also been described in ~10%...
The inner ear refers to the bony labyrinth, the membranous labyrinth and their contents. It is divided into three main parts:
The organ of Corti, also known as the spiral organ, is the receptor organ for hearing, located in the cochlea (housed inside the scala media). It is a strip of sensory epithelium made of hair cells which act as the sensory receptors of the inner ear.
This is a gross oversimplification...
Endolymph is a one of two type of cochlear fluids, the other being perilymph. It is located in the scala media of the cochlea.
It is secreted by the stria vascularis (colloquially called 'battery of the cochlea') on the outer wall of the scala media.
It has a high level of potassium (K+) and g...
The round window is one of two openings in the middle ear, localised at the level of the cochlea, allowing communication between the middle and inner ear. It vibrates with opposite phase to vibrations from the inner ear, producing movement of perilymph in the cochlea.
It is locat...
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...
Some ostiomeatal complex anatomical variations, which do not cause disease by themselves, can promote narrowing and even obstruction 1:
concha bullosa ~10% (range 4-15%) - aerated middle turbinate
intralamellar cell: air cell within vertical portion of the middle turbinate
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...
The oculomotor nerve is the third of the cranial nerves and arises from the midbrain. It is responsible for the movements of four of the six extra-ocular muscles, the other two being innervated by the trochlear and abducens nerves.
Nucleus and cisternal portion
The oculomotor nu...
The oropharynx forms part of the pharynx, being the continuation of the oral cavity and nasopharynx superiorly, and the larynx and hypopharynx inferiorly.
The oropharynx is the posterior continuation of the oral cavity and the inferior continuation of the nasopharynx.
Waldeyer's ring is a ring of lymphoid tissue located in the nasopharynx and oropharynx at the entrance to the aerodigestive tract.
The structures composing this ring are:
palatine tonsils (also called the faucial tonsils)
adenoid tonsils (nasopharyngeal tonsils)
the lateral ba...
PET-CT is a combination of cross-sectional anatomic information provided by CT and the metabolic information provided by positron emission tomography (PET).
PET is most commonly performed with 2-[F-18]fluoro-2-deoxy-D-glucose (FDG). Fluorine-18 (F-18) is an unstable radioisotope and has a half-...
Prussak space is a subcomponent of the lateral epitympanic space and extends from the level of the scutum to the umbo. This space is best demonstrated on the oblique coronal image.
lateral: pars flaccida of the tympanic membrane
medial: neck of the malleus
The galea aponeurotica (also called the Galeal or epicranial aponeurosis or the aponeurosis epicranialis) is a tough fibrous sheet of connective tissue that extends over the cranium, forming the middle (third) layer of the scalp.
Le Fort fractures are fractures of the midface, which collectively involve separation of all or a portion of the midface from the skull base. In order to be separated from the skull base, the pterygoid plates of the sphenoid bone need to be involved as these connect the midface to the sphenoid b...
The Biffl scale or grade illustrates the spectrum of blunt cerebrovascular injury (BCVI) seen on angiography (both CTA and DSA). Some authors refer to the grading scale as the Denver scale, which is not to be confused with the Denver criteria, a series of clinical indications and risk factors fo...
Ossicular chain fixation refers to the presence of fibrous tissue (chronic adhesive otitis media) which usually appears as a non-calcified, soft tissue density encasing some or all of the ossicular chain.
It may be present in the mesotympanum and/or epitympanum yet it usually occurs in the nich...
The mastoid air cells (cellulae mastoidae) 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 in...
The ethmoidal air cells (or less commonly, the ethmoidal sinuses) form one of the four pairs of paranasal sinuses. They are located within the single, midline ethmoid bone. They are present at birth, and they develop rapidly from 0-4-year-old; they further mature from 8-12-year-old during pubert...
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...
The anterior epitympanic recess, also known as the supratubal recess, is a small discrete space in the epitympanum anterior to the malleus. It is separated from the epitympanum proper by the anterior attic bony plate, also known as the cog, which has its orientation in the coronal anatomical pla...
The tympanic annulus is the thickened edge of the pars tensa of the tympanic membrane, anchoring it in the tympanic sulcus 3.
The tympanic annulus is formed by a fibrocartilaginous thickening of the edge of the pars tensa and has a horseshoe-shaped configuration. It is deficient ...
Choroidal detachment is a detachment of the choroid from the underlying sclera due to the accumulation of fluid in the suprachoroidal space generally due to increased intraocular pressure (IOP), as observed in some settings:
exudative: fluid accumulatin...
Sialadenitis refers to inflammation of the salivary glands. It may be acute or chronic and has a broad range of causes.
Patients may present with painful swelling of the concerned salivary gland, after eating (salivary colic). In bacterial sialadenitis, there may be a pu...
The scutum is a sharp bony spur that is formed by the superior wall of the external auditory canal and the lateral wall of the tympanic cavity. It forms the lateral margin of Prussak space.
acquired cholesteatoma: it is usually the first bony structure to be eroded by the enl...
The tensor tympani is a short muscle in the middle ear that arises from the superior surface of the cartilaginous part of the Eustachian tube, the greater wing of the sphenoid, and the petrous part of the temporal bone. It passes across the tympanic cavity and inserts into the upper end of the h...
The tympanic membrane is a thin membrane that separates the external ear from the middle ear. It acts to transmit sound waves from air in the external auditory canal (EAC) to the ossicles of the middle ear.
The tympanic membrane is shaped like a flat cone pointing into the middle...
The hypotympanum refers to the portion of the tympanic cavity lying inferior to the level of the inferior margin of the external acoustic canal (EAC).
The hypotympanum is the smallest of the three compartments that make up the tympanic cavity and is a shallow depression in the fl...
Paranasal sinus mucoceles represent complete opacification of one or more paranasal sinuses by mucus, often associated with bony expansion due to obstruction of the nasal sinus drainage.
Clinical presentation depends on two factors:
location and direction of expansion
Accessory parotid glands are a normal variant and represent ectopic salivary tissue separate from, but usually in close proximity to, the main parotid glands 1. Occasionally the accessory tissue is contiguous with the main glands.
Accessory parotid glands are commonly picked up in...
Zuckerkandl tubercle is a normal variant of the thyroid and may be mistaken for a thyroid nodule, mass or lymph node. It is a projection of normal thyroid tissue from the posterior aspect of the lateral lobes of the thyroid gland.
The tubercle is also an important surgical landmark due to its ...
Brachycephaly refers to a calvarial shape where the bi-parietal diameter to fronto-occipital diameter approaches the 95th percentile. It can result from a craniosynostosis involving the coronal and lambdoid sutures.
Brachycephaly can be associated with numerous syndrom...
The ice cream cone sign may refer to:
the appearance of the head of malleus and the body and short process of the incus on axial CT scan: failure of this normal configuration suggests incudomalleolar dysarticulation
the ball of the ice cream is formed by the head of the malleus and cone is for...
The crista galli is a thick, midline, smooth triangular process arising from the superior surface of the ethmoid bone, projecting into the anterior cranial fossa. It separates the olfactory bulbs, which lie either side of it in the olfactory fossae of the cribriform plate. It serves as an anteri...
Retropharyngeal abscess is a potentially life-threatening infection involving the retropharyngeal space which requires prompt diagnosis and aggressive therapy.
Retropharyngeal abscesses are most frequently encountered in children, with 75% of cases occurring before the age of 5 ye...
Temporal bone fractures are usually a sequela of significant blunt head injury. In addition to potentially damaging hearing and the facial nerve, associated intracranial injuries, such as extra-axial haemorrhage, diffuse axonal injury and cerebral contusions are common. Early identification of t...
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.
Low attenuation lymphadenopathy suggests underlying necrosis and can be seen in:
metastatic carcinoma (or lymphoma)
infections (tuberculous or fungal)
low attenuation lymphadenopathy
high attenuation lymphadenopathy
The term kissing carotids refers to tortuous and elongated vessels which touch in the midline. They can be be found in:
within the pituitary fossa
within sphenoid sinuses
within sphenoid bones
The significance of kissing carotids is two-fold:
may mimic intr...
Thyroglossal duct cysts (TGDC) are the most common congenital neck cyst. They are typically located in the midline and are the most common midline neck mass in young patients. They can be diagnosed with multiple imaging modalities, including ultrasound, CT, and MRI.
TIRADS is a risk stratification system for classifying thyroid lesions and was recently recognized in an American College of Radiology (ACR) white paper1. Its use is being advocated similar to BIRADS category for breast lesions.
In 2017, a white paper2 was released by the ACR committee on thyr...
Widening of diploic space refers to expansion of the spongy or cancellous bone between the inner and outer tables of the calavarium. The diploic space is the medullary cavity of the skull, and a location of normal physiologic hematopoiesis in adults. Thus, expansion of this structure most common...
The Holman-Miller sign (also called the antral sign) is seen in juvenile nasopharyngeal angiofibroma; it refers to the anterior bowing of the posterior wall of the maxillary antrum as seen on a lateral skull radiograph or cross-sectional imaging 1,2.
This is a non-specific sign that can be prod...
Frontonasal dysplasia, also known as median cleft face syndrome, is a rare disorder characterised by midline defects involving the face, head, and central nervous system.
Frontonasal dysplasia is considered to be a very rare condition, with approximately 100 cases having been repo...
Sialography is the imaging of the salivary glands, most commonly the parotid gland. The salivary ducts are conventionally examined fluoroscopically with high sensitivity, though cross-sectional imaging with CT or MR sialography has also been described.
suspected sialolithiasis or s...
The Bolger classification of maxillary sinus hypoplasia proposed by Bolger et al. in 1990 1 takes into account associated anomalies of the uncinate process, which are of utmost importance for planning functional endoscopic sinus surgery (FESS).
Maxillary sinus hypoplasia in itself is asymptomat...
The skull base angle allows the diagnosis of platybasia and basilar kyphosis. There are several different techniques that may be used on sagittal images from MRI or CT.
Angle formed by:
line joining the nasion with the centre of the pituitary fossa
line joining the anteri...
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 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 ...
The mylohyoid muscles form a paired muscular sling that forms part of the floor of the mouth. It also separates the sublingual space (and oral cavity) from the submandibular space.
origin: mylohyoid line/ridge on the medial surface of the mandible
insertion: midline raphe that extend...