Abscesses are focal confined collections of suppurative inflammatory material and can be thought of as having three components 1:
central core comprised of necrotic inflammatory cells and local tissue
peripheral halo of viable neutrophils
surrounded by a 'capsule' with dilated blood vessels a...
Acute sinusitis is an acute inflammation of the nasal and paranasal sinus mucosa that last less than four weeks and can occur in any of the paranasal sinuses.
Fever, headache, postnasal discharge of thick sputum, nasal congestion and abnormal smell.
Amaurosis fugax is the transient mono-ocular loss of vision, normally lasting a few seconds to a few minutes, and is secondary to vascular ischaemia/insufficiency. Usually the cause is ascribed to occlusion of the central retinal artery there are a wide number of local and central causes.
The atlantodental interval (ADI), as the name suggests, is the horizontal distance between the anterior arch of the atlas and the dens of the axis, used in the diagnosis of atlanto-occipital dissociation injuries and injuries of the atlas and axis.
It is the distance (in mm) between the posteri...
Autoimmune thyroiditises (AIT) refers to a group of conditions where there is inflammation involving the thyroid gland related to thyroid antibodies.
They are most common thyroid disease group in the paediatric population 5.
Entities that fall under this category inclu...
The basion-axial interval (BAI), as the name suggests, is the horizontal distance between the basion and the posterior cortex of the axis, used in the diagnosis of atlanto-occipital dissociation injuries.
It is the distance (in mm) between the basion and the superior extension of the posterior ...
The basion-dens interval (BDI), as the name suggests, is the distance between the basion and the tip of the dens, used in the diagnosis of atlanto-occipital dissociation injuries.
It is the distance from the most inferior portion of the basion to the closest point of the superior aspect of the ...
Benign minor salivary gland pathology is a broad term that encompasses a number of relatively uncommon pathologies that affect the minor salivary glands of the head and neck:
salivary retention cysts
Bilateral thinning of the parietal bones (also known as biparietal osteodystrophy) is an uncommon, slowly progressive acquired disease of middle-aged people with slight female predilection. It is typically an incidental finding. The aetiology is unknown but is thought to be an age-related proces...
The bimastoid line has been described and used to evaluate basilar invagination on frontal skull plain film and coronal recontructed CT image.
The bimastoid line is drawn between right and left tip of mastoids. The tip of the odontoid process of C2 normally projects less than or equal to 10 mm...
Serum carcinoembryonic antigen (CEA) is a cell-adhesive glycoprotein that was discovered in colorectal cancer in 1965, and is hence one of the oldest and most used tumour markers. Its name derives from its normal expression in fetoembryonic liver, gut and pancreas tissue.
Normal range of CEA is...
Chamberlain line is a line joining the back of hard palate with the opisthion on a lateral view of the craniocervical junction.
It helps to recognise basilar invagination which is said to be present if the tip of the dens is >3 mm above this line.
McGregor developed a modifica...
Cleft palate is a type of facial cleft. It can occur in two main aetiologically different forms:
in association with a cleft lip: cleft lip +/- palate (much commoner)
on its own: isolated cleft palate (rarer)
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, from the intracranial compartment or from below the base of skull.
When evaluating the clivus it is important to compare the...
Cochlear implants (CI) are a surgically implanted electronic device that provides a sense of sound to a person who is profoundly deaf or severely hard of hearing. Unlike conventional hearing aids, the cochlear implant does not amplify sound, but works by directly stimulating any functioning audi...
Conductive hearing loss is caused by a range of developmental, congenital or acquired pathology to the external, middle or inner ear.
Essentially any process that obstructs or disrupts the passage of sound waves through the outer or middle ear can cause conductive hearing loss and th...
Convexal subarachnoid haemorrhages (SAH) are nontraumatic intracranial haemorrhages that occur within the surface sulci of the brain (c.f. basal cisternal distribution of aneurysmal SAH). There are various causes of convexal SAH, some of which include:
dural venous sinus thromboses
Cranial gun shot injuries are a form of penetrating traumatic brain injuries, which are much less common than blunt traumatic brain injuries.
Please see the main article "imaging of gun shot injuries" for a general description of imaging features.
Craniotomy is a surgical procedure where a piece of calvarial bone is removed to allow intracranial exposure. The bone flap is replaced at the end of the procedure, usually secured with microplates and screws. If the bone flap is not replaced it is either a craniectomy or cranioplasty.
CSF otorrhoea is defined as leakage of CSF from subarachnoid space into the middle ear cavity or mastoid air cells.
There are a number of underlying causes, and thus no specific demographic is affected.
Patients typically present with conductive deafness a...
Cystic or necrotic appearing lymph nodes can be caused by a number of infectious, inflammatory or malignant conditions:
squamous cell carcinoma metastases
plasmacytoid T-cell leukemia
acute myeloid leukemia
herpes simplex lymphadenit...
The differential diagnosis cystic mass adjacent to the angle of mandible includes:
branchial cleft cyst
from metastatic squamous cell carcinoma
from metastatic papillary thyroid cancer
The differential for cystic parotid lesions includes:
bilateral cystic parotid lesions
benign lymphoepithelial lesions of HIV
unilateral cystic parotid lesion(s)
first branchial cleft cyst: parotid lymphoepithelial cy...
Dental (periapical) abscess is an acute infection of the periapical tissue around the root of the tooth.
Patients may present with pain, oedema and purulent discharged localised to the site of pathology with or without fever and tender cervical lymphadenopathy 1.
A deviated nasal septum is a common incidental finding seen on brain and paranasal sinus CT studies.
It can be congenital or acquired. The most common acquired cause is trauma from motor vehicle accidents, sports-related injuries, and altercations.
Differential diagnosis for calcified masses in the mandible includes:
calcifying odontogenic cyst (Gorlin cyst)
calcifying epithelial odontogenic tumour (Pindborg tumour)
Cervical lymphadenopathy in an adult can result from a vast number of conditions. They include:
from head and neck tumours
other neoplastic lesions
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
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.
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...
Ectopia lentis refers to subluxation or dislocation of the lens secondary to dysfunction or disruption of zonular fibers.
systemic and syndromic disorders
typically upwards and out
most common spontaneous cause 2
homocystinuria - typically do...
There is a short list of causes for enlarged extra-ocular muscles:
thyroid associated orbitopathy
amyloidosis (very rare) 2
Extraconal orbital lesions include lesions which arise within the extraconal orbital structures and those extending from adjacent structures into the orbits.
dermoid cyst: most common lesion in paediatrics
lacrimial gland lesions
Facial fractures are commonly caused by blunt or penetrating trauma sustained during motor vehicle accidents, assaults, and falls. The facial bones are thin and light making them susceptible to injury.
Males are affected more commonly than females and facial fractures are most com...
Facial palsy refers to the neurological syndrome of facial paralysis. It can result from a broad range of of physiological insult to the facial nerve or its central nervous system origins. The most common causes of this is Bell palsy.
While facial palsy refers to the clinical pres...
Frontal bossing is a calvarial radiographic feature where the front of the skull appears protruding anteriorly. It is best appreciated on a sagittal or lateral image.
This feature can be seen in many conditions (in alphabetical order):
Heterogeneous echogenicity of the thyroid gland is a non specific finding and has been associated with conditions diffusely affecting the thyroid gland. These include
High arched palates are a facial feature of many syndromes, although the classic association is Marfan syndrome. There are hundreds of conditions associated with high arched palates, with some of the radiologically-more important including:
Hyperattenuating paranasal sinus opacification can arise in a number of situations. These include
fungal sinus disease
acute haemorrhage into sinus
In some situations can consider early calcification within the sinus
The differential diagnosis for hyperostosis of the skull depends on whether it is focal or diffuse.
Paget's disease of bone
metastatic disease, especially prostate carcinoma
chronic, severe anaemia
Hyperparathyroidism is the effect of excess parathyroid hormone (PTH) in the body. It can be primary, secondary or tertiary. There are many characteristic imaging features predominantly involving the skeletal system.
Increased levels of the PTH lead to increased osteoclastic activity...
Hypotelorism refers to an abnormal decrease in distance between any two organs although some authors use the term synonymously with orbital hypotelorism meaning an abnormal decrease in the distance between the two eyes (the eyes appear too close together). The article mainly focuses on the latte...
Ingested bones that become lodged in the throat or gastro-intestinal tract are a common presentation to the emergency department. Recognition is important because these cases can be potentially fatal.
Patients may present with a 'foreign body' feeling in the throat after eating fish...
Intraconal orbital lesions are broadly divided to two main groups; those with or without involvement of the optic nerves:
Lesions with optic nerve involvement:
optic nerve glioma
optic nerve meningioma
lymphoma and leukaemia
Jugular fossa masses comprise a range of pathological lesions that arise from or extend into the jugular fossa in the skull base. Although not a common location for tumours it is not unusual for jugular fossa lesions to be discovered incidentally on cross sectional imaging.
Labyrinthitis is inflammation of the membranous labyrinth.
Labyrinthitis can be divided according to aetiology.
Labyrinthitis is a potential complication of acute otomastoiditis with spread of infection or of toxins from the middle ear to the inner ear via either the r...
Mass lesions involving the lacrimal glands can be classified into two broad groups - inflammatory (~50%) and neoplastic, either lymphoma (25%) or salivary gland type tumours (~25%).
affects ~25% of patients with systemic disease
orbital inflammatory pseud...
Laryngeal cysts can occur in any part of larynx, but are more frequent on supraglottic locations, such as epiglottis and vallecula. The prevalence of each location varies on different studies.
The laryngeal cysts represent a rare group, about 5%, of benign laryngeal lesions 1. Th...
Leukocoria (also spelled as leucocoria or leukokoria) refers to an abnormal white reflection from the retina. Despite its colour, the reflection is related to the familiar red-eye effect. Usually, when a light is shone through the iris, the retina appears red to the observer. In leukocoria, the ...
Longitudinal temporal bone fractures normally occurs parallel to the long axis of the petrous bone. A more current classification of the extent of temporal bone fractures describes the integrity of the otic capsule rather than the fracture orientation (see temporal bone fractures.)
The increased globe size or macrophthalmia may have many differentials:
buphthalmos (congenital glaucoma)
macrophthalmus in neurofibromatosis type 1 (NF1)
connective tissue disorders: Marfan syndrome, Ehlers-Danlos syndrome
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...
There are many causes for mandibular periostitis:
Langerhans cell histiocytosis
malignancy (both primary and metastatic)
necrosis, e.g. radiation osteonecrosis
Garre's sclerosing osteomyelitis
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...
This article contains a list of commonly used medical abbreviations and acronyms that may be encountered in medicine and radiology (please keep in alphabetic order).
AAA: abdominal aortic aneurysm
AAC: adenocystic carcinoma
AARF: atlantoaxial ro...
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
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...
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
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
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&...
Obstruction of nasolacrimal drainage apparatus results in epiphora, and can be primary or secondary, congenital or acquired. Obstruction can occur in canaliculi, lacrimal sac, or nasolacrimal duct (post saccular) levels.
Congenital obstruction is usually secondary to persistence of the membrane...
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...
Ocular pathology covers a wide range of conditions and therefore represents the cause of a wide range of symptoms, signs and radiographic features.
Ocular metastases account for over 80% of all ocular pathology. With regard to the remainder of ocular lesions, the primary differentiating factor ...
Ophthalmoplegia describes the abnormal eye movement that occurs because of paralysis of one or more of the six extraocular muscles involved in eye movements. Classification can be based on the cause of the ophthalmoplegia or the directions of the affected movements.
There are numerous causes of...
Enlargement of the optic nerves is uncommon and has a surprisingly broad differential:
optic nerve glioma
optic nerve meningioma
Several cystic and cyst-like orbital lesions may be encountered in imaging of the orbits:
developmental orbital cysts
dermoid: commonest benign orbital tumour in childhood
congenital cystic eye
Orbital infection can be a commonly encountered entity.
It is important to differentiate between orbital and periorbital cellulitis, as this has therapeutic and prognostic implications:
periorbital cellulitis (preseptal cellulitis) is limited to the soft tissues anterior to the orbital septum ...
The differential diagnosis of orbital inflammatory diseases (including orbital pseudotumours) can be divided based on their location into:
dacryoadenitis of lacrimal glands
myositis of extraocular muscles
perineuritis of optic nerve
An orbital mass carries a relatively wide differential:
lacrimal gland or duct tumours
rhabdomyosarcoma of the orbit
optic nerve meningioma
optic nerve glioma
optic nerve schwannoma
developmental orbital cysts 3:
Orbital vascular lesions may be difficult to distinguish on imaging. However, the following conditions have been described:
lymphangioma / lymphangiovenous malformation / venolymphatic malformation
orbital venous malform...
Oxalosis results in supersaturation of calcium oxalate in the urine (hyperoxaluria), which in turn results in nephrolithiasis and cortical nephrocalcinosis.
This article focus on the secondary oxalosis, please refer to primary oxalosis for a specific discussion on this entity.
Paragangliomas, sometimes called glomus tumours, are slow growing tumours arising from non-chromaffin paraganglion cells that are scattered throughout the body from the base of skull to the bladder.
Paragangliomas will be discussed separately depending on their location:
paragangliomas of the ...
Paragangliomas of the head and neck are rare tumours, representing <0.5% of all head and neck tumours.
For a general discussion of the pathology of these tumours please refer to the paraganglioma article.
Overall there is a 3:1 female predominance, with two-thirds of cases bei...
Parotid enlargement has a wide differential given the significant breadth of pathology that can affect the parotid gland. These can be separated by the standard surgical sieve approach into infective, inflammatory, immune, neoplastic, infiltrative and congenital causes.
A predunculated intratracheal mass has a variety of differential diagnoses:
benign tumour, e.g. hamartoma, chrondroma, lipoma
metastasis to tracheal mucosa, e.g. renal cell carcinoma, melanoma
polyp, e.g. inflammatory, antrochoanal
Platybasia is characterised by abnormal flattening of the skull base as defined by measuring the base of skull angle >143º.
Platybasia alone does not usually cause symptoms unless it is associated with basilar invagination.
Pneumoparotid refers to air in the parotid gland and can cause unilateral/bilateral parotid swelling. In severe cases it can be associated with subcutaneous emphysema.
Any profession or recreation that increases oral positive pressure can cause air to reflux up the parotid ducts int...
Powers ratio is a measurement of the relationship of the foramen magnum to the atlas, used in the diagnosis of atlanto-occipital dissociation injuries.
The ratio, AB/CD, is measured as the ratio of the distance in the median (midsagittal) plane between the:
basion (A) and the posterior spinola...
There are a number of primary malignancies of the nasopharynx:
nasopharyngeal carcinoma (squamous cell carcinoma): 70%
lymphoma (sinonasal lymphoma): 20%
adenoid cystic carcinoma
Proptosis refers to forward protrusion of the globe with respect to the orbit. There are many causes of proptosis which can be divided according to location and it is worth remembering that it is not just orbital disease processes that cause proptosis.
Exophthalmos also describes f...
Pulsatile exophthalmos or pulsatile proptosis is a clinical symptom characterized by protrusion and pulsation of the eyeball that can occur due to various causes:
neurofibromatosis type 1 (with sphenoid wing dysplasia)
trauma (orbital roo...
Lucent lesions of the mandible are not uncommon and may be the result of odontogenic or non-odontogenic processes. Lucency may be conferred by a cystic process (e.g. periapical cyst) or a lytic process (e.g. mandibular metastases).
periapical (radicular) cyst ...
Ranawats line is the perpendicular distance between centre of the sclerotic ring of C2 and a line drawn along the axis of C1 vertebra
Normal value is 17mm in males and 15mm in females. It is deceased in basilar invagination .
Radiological manifestations of recreational drug use are not infrequently seen as the use of recreational drugs is widespread.
Interestingly, recent reports have suggested a decreasing incidence of reported drug use in the general population over the past decade, but it remains th...
Salivary gland tumours are variable in location, origin and malignant potential.
In general, the ratio of benign to malignant tumours is proportional to the gland size; ie: the parotid gland tends to have benign neoplasm, the submandibular gland 50:50 and the sublingual glands and a...
Head and neck manifestations of sarcoidosis can have three main forms:
orbital involvement: orbital sarcoidosis
parotid gland involvement
nodal involvement: cervical lymphadenopathy in sarcoidosis
Sensorineural hearing loss (SNHL) refers to deafness secondary to conditions affecting the inner ear, internal acoustic canal, cerebellopontine angle, or vestibulocochlear nerve.
Conditions that cause SNHL can be divided by location
otosclerosis (and other...
Sincipital encephalocoeles are congenital herniations of cerebral parenchyma through a cranial defect. There are three main types 1,2:
frontonasal encephalocoele (~50%)
naso-ethmoidal encephalocoele (30%)
naso-orbital (nasolateral) encephalocoele
History and etymology
Sincipital is a deriva...
The nasal passage and paranasal sinuses (collectively sinonasal) plays host to a number of diseases and conditions, which can be collectively termed sinonasal disease. One way of classifying separate entities is as follows:
inflammatory and infective conditions
The skull base angle allows the diagnosis of platybasia and basilar kyphosis. There are several different techniques that may be used on sagital images from MRI or CT.
Angle formed by:
line joining the nasion with the centre of the pituitary fossa
line joining the anterio...
Skull tumours can be (as with tumours anywhere else) both primary and secondary, and benign or malignant.
giant cell tumour (GCT)
aneurysmal bone cyst (ABC)
epidermoid and dermoid cysts
On coronal cross-sectional imaging the facial nerve within its canal in the petrous temporal bone classically takes on a "snake eyes" appearance as the tympanic segment doubles back next to the labyrinthine segment adjacent to the cochlea. Anteriorly, these two segments converge at the...