Oro-antral fistula (OAF) is a pathological communication between the oral cavity and the maxillary sinus (antrum).
There is a slightly greater male predilection 2.
Oro-antral fistulas may be subtyped by location into:
T staging of oropharyngeal tumours is as follows:
The oropharynx includes the base of the tongue, the inferior surface of the soft palate and uvula, the anterior and posterior tonsillar pillars, the glossotonsillar sulci, the pharyngeal tonsils, and the lateral and posterior pharyng...
The oropharynx forms part of the pharynx, being the continuation of 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.
Oscillopsia (also known as Dandy syndrome or jumbling of the panorama) is the inability to maintain horizon while walking.
Since our heads bob up and down while walking, the otolithic system controls eye movement to maintain a constant horizon when walking. When there is bilateral absent vestib...
Ossicular chain disruption (or ossicular discontinuity) is loss of normal alignment between the three middle ear ossicles. The condition is a cause of conductive hearing loss.
Exact incidence and prevalence are not known. Hearing loss associated with temporal bone fractures in chi...
Ossicular chain fixation refers to the presence of fibrous tissue (chronic adhesive otitis media) which usually appears as noncalcified, soft-tissue density encasing some or all of the ossicular chain.
It may be present in the meso- and epitympanum yet it usually occurs in the niche of oval win...
Osteomas are benign mature bony growths, seen almost exclusively in bones formed in membrane (e.g. the skull).
When they arise from bone they may be referred to as a "homoplastic osteoma", and when they arise in soft tissue they may be referred to as a "heteroplastic osteoma".
The ostiomeatal complex (OMC) (or ostiomeatal unit (OMU)), sometimes less correctly spelled as osteomeatal complex, is a common channel that links the frontal sinus, anterior ethmoid air cells and the maxillary sinus to the middle meatus allowing airflow and mucociliary drainage.
A useful mnemonic to remember the five parts of the ostiomeatal complex is:
H: hiatus semilunaris
E: ethmoidal bulla
M: maxillary ostium
U: uncinate process
Emus have large beaks, and hence could have large ostiomeatal complexes (if they had paranasal sinu...
Some ostiomeatal complex anatomical variations, which do not characterise disease by itself, 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 Ostmann fat pads (also somewhat lewdly known as Ostmann fatty bodies) are located inferomedial to the Eustachian tubes and is thought to be important in normal closure, preventing transmission of nasopharyngeal pressure to the middle ear. Failure to visualize this thin triangular fat pad is ...
The otic capsule refers to the dense osseous labyrinth of the inner ear that surrounds the cochlea, the vestibule and the semicircular canals. It is surrounded by the less dense / pneumatised petrous apex and mastoid part of the temporal bone.
petrous temporal bone fractures...
The otic ganglion is one of four parasympathetic ganglia of the head and neck. It receives parasympathetic fibres from the glossopharyngeal nerve.
small and disc shaped
located in the infratemporal fossa
it lies immediately below the foramen ovale, medial to the mandibular divi...
Otitis externa refers to inflammation of the external ear.
It is quite a common condition and may affect up to 10% of people during their lifetime.
It can present in several forms:
acute otitis externa
chronic otitis externa
necrotising otitis externa
Otitis media refers to inflammation or infection of the middle ear cavity. It is commonly seen in children and is termed otomastoiditis when inflammation spreads to involve the mastoid.
Common complaints include otalgia, otorrhoea, headache, fever, and systemic upset. In ...
Otosclerosis (also known as otospongiosis) is an idiopathic slowly progressive primary disorder of the bony labyrinth. It is one of the leading causes of deafness in adults.
The term otosclerosis is somewhat of a misnomer. Much of the clinical course is characterised by lucent rat...
Otosyphyilis, otic syphilis or syphilitic labyrinthitis is a manifestation of neurosyphilis affecting the inner ear.
For a general discussion, and for links to other system specific manifestations, please refer to the article on syphilis.
The pathological features of syphilitic lab...
Oval window atresia or congenital absence of oval window shows absent cleavage plane between the lateral semicircular canal above and cochlear promontory below associated with anomalous stapes and malpositioned facial nerve (cranial nerve VII).
Profound conductive hearin...
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.
P16 is a widely used immunohistochemical marker. It can be expressed in other neoplasms and in several normal human tissues. It can play an important role gynecological malignancy and is a surrogate marker for HSIL's (high-grade squamous intraepithelial lesions). It has been applied to facilitat...
The differential diagnosis of paediatric cervical lesions is commonly encountered in practice, unfortunately, the list is long.
Most lesions tend to be inflammatory 3:
infected branchial cle...
Tumours of the posterior fossa in children can be remembered using the mnemonic:
The mnemonic is not in order of prevalence; pilocytic astrocytomas are most common.
B: brainstem glioma
A: astrocytoma (pilocytic) (85%)
The palate is the partition between the oral and nasal cavities, forming the roof of the oral cavity and the floor of the nasal cavity. It is composed of the osseous fixed hard palate comprising the anterior 2/3rds of the palate and a mobile soft palate devoid of bone and with multiple functions...
The palatine bones are paired L-shaped bones joined at the midline. They form the hard palate with the maxillary bones. They also form part of the floor of the nasal cavity (the hard palate separates the oral cavity from the nasal cavity).
The palatine bones are located at the b...
The palatine tonsil, referred simply to as "the tonsils" when considered together bilaterally, is a collection of lymphoid tissue in the pharyngeal mucosa.
It is often described to have two borders, two poles and two surfaces:
anterior and posterior borders (described in relatio...
The palatoglossus muscle is one of the four extrinsic muscles of the tongue. The paired muscles create ridges of mucous membrane in the lateral pharyngeal wall called the palatoglossal arches (also know as the anterior pillars of the fauces). These form the lateral boundary between the oral cavi...
The palatopharyngeus is a muscle of the head and neck, and one of the inner longitudinal muscles of the pharynx. It is also referred to as one of the five paired muscles of the soft palate. The paired muscles create ridges of mucous membrane in the lateral pharyngeal wall called the palatophary...
The palatovaginal canal is a small short canal located at the articulation of the sphenoidal process of palatine bone and the vaginal process of the medial pterygoid plate of the sphenoid bone.
It transmits the pharyngeal nerve, a branch of the maxillary division of the trigeminal nerve (CN Vb)...
Papillary thyroid carcinoma (PTC) is the most common malignancy of the thyroid gland, and frequently has nodal metastases at presentation.
Papillary thyroid cancer (as is the case with follicular thyroid cancer) typically occurs in the middle-aged, with a peak incidence in the 3rd...
Paradoxical middle turbinate is a rare developmental cause of nasal obstruction. It refers to an inferomedially curved middle turbinate edge with theconcave surface facing the nasal septum, and usually occurs bilaterally.
Paradoxical middle turbinate is a rarely encountered anomal...
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 urinary bladder.
Paragangliomas are sometimes referred to as glomus tumours although this gi...
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 being ...
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
Paranasal sinuses mycetoma are indolent and non-invasive fungal colonisation of the paranasal sinuses.
Pathogenesis is thought to be a cascade of processes from insufficient mucociliary clearance leading to sinus colonisation and chronic inflammatory response. The patient may only ...
Osteoma of the paranasal sinuses is a common benign tumour, usually found incidentally.
Osteomas are commonly found in patients undergoing imaging of the sinuses, appearing in up to 3% of CT examinations of the paranasal sinuses 1. They are most frequently diagnosed in 20-50 years...
The paranasal sinuses usually consist of four paired air-filled spaces. They have several functions of which reducing the weight of the head is the most important. Other functions are air humidification and aiding in voice resonance. They are named for the facial bones in which they are located:...
Retention cysts of paranasal sinuses are usually discovered incidentally on a plain sinus radiograph or cross-sectional imaging of the head. They do not usually cause symptoms.
They are slow growing lesions, but mucosal and cortical integrity is preserved.
Parapharyngeal abscesses are deep neck abscesses involving the parapharyngeal space. It is a serious medical condition, potentially fatal, and requires prompt diagnosis treatment.
A person of any age can develop a parapharyngeal abscess, but it is most commonly seen in children an...
The parapharyngeal space is one of the seven deep compartments of the head and neck. It consists largely of fatty areolar tissue and contains branches of the trigeminal nerve as well as deep vessels.
The parapharyngeal space is shaped like a pyramid, inverted with its base at the...
The parasympathetic ganglia are a group of 4 bilateral automonic ganglia in the head and neck which receive parasympathetic fibres from the autonomic components of the cranial nerves III, VII and IX. They are involved in parasympathetic control of the eye, major and lesser salivary glands and t...
Parathyroid adenomas are benign tumours of the parathyroid glands, and are the most common cause of primary hyperparathyroidism.
Patients present with primary hyperparathyroidism: elevated serum calcium levels and elevated serum parathyroid hormone levels. This results in...
The parathyroid glands are endocrine glands located in the visceral space of the neck. They produce parathyroid hormone, which controls calcium homeostasis.
There are normally two pairs of parathryoid glands, inferior and superior, although there can be up to twelve in number. T...
Parathyroid hormone (PTH), also known as parathormone, is secreted by the parathyroid glands in response to hypocalcaemia. Its main physiologic effects are to
increase osteoclastic activity in bone
increase renal reabsorption of calcium
inhibit renal absorption of phosphate and bicarbonate
Parathyroid hyperplasia is the diffuse enlargement of the parathyroid glands and is a less common cause of primary hyperparathyroidism.
There is a female predilection (M:F = 1:3).
Most commonly an incidental finding of hypercalcaemia in asymptomatic patie...
The parietal bone is a paired, irregular, quadrilateral skull bone that forms the sides and roof of the cranium.
The parietal bone has four borders, four angles, and external/internal surfaces.
Borders include: frontal, sagittal, occipital (half of lambdoid suture), and squamou...
The parietal foramen is a foramen on each side of the posterior aspect of the parietal bone near the sagittal suture. It transmits the emissary veins draining to superior sagittal sinus and occasionally a branch of the occipital artery. It has a variable appearance and is often absent 3. When bo...
Parietal foramina are a type of congenital calvarial defect. They result from delayed/incomplete ossification of the parietal bone.
They can occur as an isolated autosomal dominant trait or as part of a syndrome. Ossification along a midline bar may separate confluent parietal defect...
The parietotemporal/parietomastoid suture represents the articulation between the parietal and temporal bones posteriorly. Anteriorly, they articulate at the squamosal suture. The parietotemporal suture is considered the most posterior continuation of squamosal suture and is at times interrupted...
The parotid duct, also known as Stensen duct, drains saliva from the parotid gland into the oral cavity. It secretes primarily serous saliva.
The parotid duct is approximately 5cm long and passes anteriorly through the buccal fat superficial to the masseter muscle and over its an...
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.
The parotid gland is the largest of the salivary glands and secretes saliva via the parotid duct into the oral cavity to facilitate mastication and swallowing. It is located in the parotid space.
The parotid gland is wrapped around the mandibular ramus and extends to a position ...
The parotid space is one of the seven deep compartments of the head and neck and as the name suggests is mostly filled with the parotid gland. It is the most lateral major suprahyoid neck space.
The parotid space is a roughly pyramidal space, the broad elongated base facing later...
The pars flaccida is the flaccid portion of the tympanic membrane and represents a small portion of the membrane.
It extends upwards from the anterior and posterior malleolar folds at the level of the lateral process of malleus. Hence, it sits between the scutum and malleus.
The pars tensa is the tense portion of the tympanic membrane and refers to the main portion of the membrane.
It extends from the anterior and posterior malleolar folds at the level of the lateral process of malleus to the inferior extent of the tympanic membrane at its attachment.
The Passavant cushion is a small prominence in the posterior pharynx, formed from a focal bulge of the superior pharyngeal constrictor muscles during swallowing.
The "cushion" opposes the soft palate during the act of swallowing and is part of the seal between soft palate and pharynx that preve...
Recognising patterns of sinonasal obstruction is useful to help localise the area of pathology and narrow the differential diagnosis.
Babbel et al described five pattern of sinonasal obstruction 1, which are readily apparent on CT:
Patulous tube syndrome (PTS), is a form of Eustachian tube dysfunction. Whereas the normal dysfunction of failure of the tube to open normally, in PTS the tube remains abnormally open allowing transmission of nasopharyngeal pressure to the middle ear.
During strong inspiration (i.e 'sniff') t...
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
Pendred syndrome is an autosomal recessively inherited disorder characterised by a euthyroid goitre associated with sensorineural hearing loss.
It is considered the most common form of syndromic hearing loss and accounts for upwards of 10% of hereditary deafness.
Penetrating traumatic neck injury can be a potentially devastating injury due to the high density of crucial anatomical structures within the neck.
Young males are highly represented in patients with a traumatic neck injury. In one study, 11:1 ratio of males to females were ident...
Periapical cysts, also known as radicular cysts, are the most frequent cystic lesion related to teeth (see mandibular lesions) and result from infection of the tooth.
On imaging, they generally appear as a round- or pear-shaped, unilocular, lucent lesion in the periapical region, measuring <1 c...
Perilymph is a one of two type of cochlear fluids, the other being endolymph. It is located in the scala vestibuli and scala tympani of the cochlea.
It is very similar to cerebrospinal fluid as the scala tympani and scala tympani communicate directly with the subarachnoid space.
It has a high ...
A perilymphatic fistula (PLF) (also known as a labyrinthine fistula) is a pathologic communication between the fluid-filled space of the inner ear and the air-filled space of the middle ear, most commonly occurring at either the round or oval window.
The primary manifestations of perilymphatic...
Perineural spread of tumour is a form of local invasion in which primary tumours cells spread along the tissues of the nerve sheath. It is a well-recognised phenomenon in head and neck cancers.
An important distinction has to be made between perineural invasion (PNI) and Perineural spread (PNS...
Peritonsillar abscess or quinsy is the most common deep neck infection.
Peritonsillar abscesses are most common in 20-40 year olds with a predominance for males and for smokers. It is less common in children but immunosuppression increases the risk of development 2-3.
The perivertebral space is one of the seven deep compartments of the head and neck.
The perivertebral space is a cylinder of soft tissue lying posterior to the retropharyngeal space and danger space surrounded by the prevertebral layer of the deep cervical fascia and extends from...
Persistent hyperplastic primary vitreous (PHPV), also known as the persistent fetal vasculature, refers to a rare congenital developmental malformation of the eye.
Clinically, this condition usually manifests as unilateral or bilateral leucocoria. Patients may also have p...
Persistent hypophyseal canal, also known when larger than 1.5mm in diameter as the craniopharyngeal canal, 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 which...
The ossiculum terminale appears as a secondary ossification centre of the dens between 3-6 years and normally fuses by 12 years. Failure of fusion results in a persistent ossiculum terminale (also called Bergmann's ossicle or ossiculum terminale of Bergmann) and is considered a normal anatomical...
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 petroclival suture is a short cranial suture between the medial tip of petrous temporal bone and the superolateral border of the clivus of the occipital bone. It is seen in continuation with the petro-occipital groove and the carotid canal is immediately anterior to this suture.
Petromastoid canal or subarcuate canal joins the mastoid antrum to the posterior cranial fossa 1 and contains the subarcuate vein and artery.
type I - invisible
type II - less than 0.5 mm width
type III - 0.5-1 mm width
type IV - greater than 1 mm width 1
Petrosquamous suture is a shallow bony fissure between the medial horizontal petrous part and lateral vertically oriented squamous part of the temporal bone.
At times, this cranial suture may house a small emissary vein which can bleed at the time of surgeries.
The petrotympanic fissure is a small fissure in the temporal bone. It divides the mandibular fossa anteriorly by the articular tubercle and posteriorly by the tympanic part of the temporal bone. The chorda tympani runs through the fissure into the infratemporal fossa.
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
Petrous apicitis, also known as apical petrositis, is infection with involvement of bone at the very apex of the petrous temporal bone.
Petrous apicitis is less common than it once was, on account of the widespread and early use of antibiotics for acute otomastoiditis 3-4.
The petrous part of the temporal bone (or more simply petrous temporal bone, PTB) forms the part of skull base between the sphenoid and occipital bones.
The petrous temporal bone has a pyramidal shape with an apex and a base as well as three surfaces and angles:
The pharyngeal (or superficial) mucosal space is one of the seven deep compartments of the head and neck. It consists of the mucosa and structures deep to the mucosa of the nasopharynx, the oropharynx, and the laryngopharynx.
The pharyngeal mucosal space is the most internal comp...
The pharyngeal nerve is a branch of the maxillary division of the trigeminal nerve and contributes to the pterygopalatine ganglion.
The pharyngeal nerve divides off the maxillary division just after emerging from the foramen rotundum to enter the pterygopalatine fossa. At the pte...
The pharyngeal plexus lies on the posterolateral wall of the pharynx, mainly over the middle pharyngeal constrictor and is the main motor and sensory nerve supply to the muscles of the pharynx and soft palate and acts to coordinate swallowing and speech 1-7.
location: within the extern...
The pharynx is the superior dilated part of the alimentary tract that connects the nasal and oral cavities to the oesophagus.
It is composed of three parts:
nasopharynx: posterior to the nasal choanae and superior to the soft palate
communicates with the nasal cavity anteriorly...
The phrenic nerve is a mixed motor/sensory nerve that courses through the neck and thorax to innervate the diaphragm.
Arises from the ventral rami of the C3, C4 and C5 nerve roots, part of the cervical plexus.
In the neck, the phrenic nerve lies on the anterior s...
Phthisis bulbi, also known as end-stage eye, is an atrophic scarred and disorganised globe that may result from a variety of severe ocular insults.
The globe is reduced in size (usually < 20 mm) with a thickened/folded posterior sclera. Dystrophic calcification is common, and osseou...
A pilomatricoma is an uncommon, benign neoplasm thought to arise from hair cortex cells. It was formerly referred to as pilomatrixoma or calcifying epithelioma of Malherbe.
the reported incidence ranges between 1 in 500-2000
they make up 0.12% of cutaneous neoplasms and 20% of al...
A useful mnemonic for remembering the differentials for pituitary region masses is:
S: sarcoid, sellar tumour (pituitary adenoma)
T: teratoma or tuberculosis (and other granulomatous diseases)
C: craniopharyngioma, cleft cyst (Rathke), ...
Platybasia is characterised by abnormal flattening of the skull base as defined as a base of skull angle over143º.
Platybasia alone does not usually cause symptoms unless it is associated with basilar invagination.
Platysma muscle is a broad superficial fascial sheet of thin muscle covering the superior anterior chest, anterior and anterolateral neck and anterolateral mandibular region.
The muscle consists of three parts: pars mandibularis, pars labialis and pars modiolaris.
origin: the fa...
Pleomorphic adenomas, also known as benign mixed tumours (BMT's), are the most common salivary gland tumours.
On imaging, they commonly present as well circumscribed rounded masses, most commonly located within the parotid gland, showing to be hypoechogenic on ultrasound and with bright T2 sign...
Plummer-Vinson syndrome, also known as the Paterson-Brown-Kelly syndrome, predisposes to hypopharyngeal squamous cell carcinoma and consists of four features:
oesophageal webs or hypopharyngeal webs
The condition is more common in women.
Pneumatisation of the dorsum sella is not uncommon, but needs to be remembered as an unusual site of sinus disease, which otherwise may be mistaken for intracranial of pituitary disease.
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...
Pneumosinus dilatans is a term given to enlarged paranasal sinus air cells (hyperpneumatisation), which may cause pneumocephalus either by rupturing or because of a defect. It was initially described in the frontal sinuses, but may involve any of the paranasal sinus.
The presence of pneumosinus...
Pöschl projection is used in imaging the temporal bone. The plane of projection is perpendicular to the long axis of the temporal bone. In the Pöschl projection the temporal bone is imaged from its anteromedial to posterolateral aspects.