The sagittal suture runs in the midline between the two parietal bones.
fusion of the sagittal suture results in scaphocephaly
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; i.e., the parotid gland tends to have benign neoplasm, the submandibular gland 50:50 and the sublingual glands and...
Only a minority of salivary gland tumour types show uptake on 99Tc scintigraphy
oncocytoma of salivary glands
haemangioendothelioma of salivary glands 1
The salivary glands within the head and neck secrete various enzymes useful for mastication and digestion. They can be divided into major and minor salivary glands:
Major salivary glands
The major salivary glands consist of the larger, paired salivary glands within the neck:
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 ...
Samter syndrome, also know as aspirin or analgesic-induced asthma refers to the constellation of 1-2:
allergy to aspirin
nasal polyposis / rhinosinusitis
Treatment and prognosis
Treatment is largely centred around avoiding aspirin, treating underlying asthma and if need be polypectom...
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
Head and neck manifestations of sarcoidosis can have three main forms:
orbital involvement: orbital sarcoidosis
parotid gland involvement
nodal involvement: cervical lymphadenopathy in sarcoidosis
Orbital manifestations of sarcoidosis are common among patients with systemic sarcoidosis and can involve the lacrimal gland, the orbit, soft tissues of the orbit, and the optic nerve. Uveitis is by far the most common manifestation and is typically bilateral 5.
For a general discussion of the...
The scalenus anterior (also known as anterior scalene) is a neck muscle and known as the "key" structure for the thoracic inlet as it is an important anatomical landmark.
origin: transverse processes of 3rd to 6th cervical vertebrae
insertion: inner border of first rib (s...
The scalenus medius (middle scalene) muscle is one of the three scalene muscles in the neck.
origin: transverse processes of lower six cervical vertebrae (C2-C7)
insertion: upper surface of first rib
action (similar to scalenus anterior muscle)
raises first rib (respiratory inspirat...
The scalenus posterior (posterior scalene) is one of the three scalene muscles in the neck.
origin: transverse processes of lower two or three cervical vertebrae (C5-C7)
insertion: outer surface of second rib
raises second rib (respiratory inspiration)
acting together: nec...
Schneiderian epithelium/membrane is the unique lining of the nasal cavity paranasal sinuses, and is a ectodermally derived ciliated columnar epithelium with goblet cells. It differs from the similarly appearing respiratory epithelium, which is endodermally derived.
Schneiderian papillomas are uncommon sinonasal tumours that arise from the sinonasal Schneiderian epithelium.
Schneiderian papillomas account for ~2.5% (range 0.4-4.7%) of sinonasal tumours 2.
There are three distinct histological types 1,2,3:
Scleritis refers to inflammation of the sclera. It has a wide range of causes.
It can affect age group but usually those between ages 30 and 50. There is a recognised increased female predilection (F:M of around 2:1).
Information on the pathogenesis of scleritis is lim...
Sclerosteosis is a rare autosomal recessive bone dysplasia resulting in sclerosis and hyperostosis, particularly of the skull, mandible and tubular bones. It is closely related to Van Buchem disease 1.
Sclerosteosis is a very rare disease, with only around 100 cases reported. Ther...
Sclerotic skull lesion can result from a number of causes. They include:
hyperostosis frontalis interna (normal variant)
lytic skull lesions
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's space.
acquired cholesteatoma: it is usually the first bony structure to be eroded by the e...
Second branchial cleft cysts are a cystic dilatation of the remnant of the 2nd branchial apparatus, and along with 2nd branchial fistulae and sinuses accounts for 95% of all branchial cleft anomalies.
Although a congenital abnormality, they tend to present in early adulth...
Second branchial cleft fistulae are congenital anomalies of embryonic development of branchial apparatus with the external cutaneous ostium in the lateral neck connecting to the tonsillar fossa. They can be diagnosed as a result of typical clinical presentation and the diagnosis can be confirmed...
The semicircular canals are components of the bony labyrinth along with the cochlea and vestibule.
There are three semicircular canals on each side:
superior semicircular canal: vertical plane
posterior semicircular canal: vertical plane
lateral semicircular canal: 30 degrees...
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...
A short maxillary length can result from many congenital and acquired causes. If seen in an antenatal ultrasound scan it is often considered to have a high association with trisomy 21 1.
Many conditions that can cause a mid face hypoplasia will result in a short maxillar...
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...
Sialectasis (siadochiectasis) is the cystic dilatation of the ducts within salivary glands. It is most commonly seen in the parotid gland and is associated with ascending infections and gland destruction.
Isolated, diffuse swelling of the affected salivary gland.
A sialocoele refers to a cystic space (usually saliva containing) arising within a salivary gland.
They are essentially post- traumatic or iatrogenic in nature. The proposed mechanism includes laceration of the salivary glad duct or ductal stenosis with subsequent dilatation.
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 have also been described.
suspected sialolithiasis or...
Sialolithiasis refers to formation of concrements (sialoliths) inside the ducts or parenchyma of salivary glands, and most commonly occurs in the submandibular glands and their ducts.
Sialolithiasis is most common disease of salivary glands, accounting for approximately 50% of all...
Sialosis refers to diffuse, non-inflammatory, non-neoplastic recurrent enlargement of the major salivary glands. It is uncommon and has a variety of systemic causes.
The commonest causes are diabetes mellitus and alcoholism. Other causes include malnutrition, hormonal insufficiency and radiatio...
Cerebral manifestations of sickle cell disease (SCD) contribute significantly to the overall morbidity of the disease. SCD is among the most common causes of stroke in paediatric population.
For a general discussion of sickle cell disease, please refer to sickle cell disease.
The sigmoid plate is variously described as the thin plate of bone between a high riding jugular bulb and the middle ear cavity (as shown in first image) or more generally as the thin bone separating the sigmoid sinus from adjacent structures (especailly mastoid air cells).
The wall of th...
The silent sinus syndrome represents maxillary sinus atelectasis that results in painless enophthalmos, hypoglobus and facial asymmetry 1-3. Some authors restrict the term to patients with no history of sinusitis, trauma or surgery 2.
Silent sinus syndrome usually presents in the ...
Sincipital encephalocoeles are congenital herniations of cerebral parenchyma through a cranial defect. There are three main types 1,2:
frontonasal encephalocoele (~50%) - more common in Asia and Latin America4
naso-ethmoidal encephalocoele (30%) - more common in North America4
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
Sinonasal lymphoma refers to the involvement of the nasal cavity and/or paranasal sinuses with lymphoma. It can be primary or secondary.
Presenting symptoms of sinonasal lymphoma are are variable but are usually similar to those of benign inflammatory diseases. The clinic...
Sinonasal mucosal melanoma (SNMM) is a very rare and unique subtype of malignant melanoma.
SNMMs account for ~1% of malignant melanomas and <4% of head and neck cancers 1,2. They affect older patients (60-90 years old) 2. There is a higher incidence in Japan 5.
Sinonasal polyposis refers to the presence of multiple benign polyps in the nasal cavity and paranasal sinuses. It causes a particular pattern of chronic sinusitis.
Clinical symptoms may include 3
progressive nasal stuffiness
Sinonasal undifferentiated carcinoma (SNUC) is a rare and highly aggressive neoplasm arising in the paranasal sinuses. It has recently been characterised as a distinct pathologic entity.
Tumours tend to be rather advanced at presentation.
Sinus pericranii (SP) is a cranial venous anomaly in which there is an abnormal communication between intracranial dural sinuses and extracranial venous structures, usually via an emissary transosseous vein.
It is considered a type of low flow vascular malformation. It occurs in close communica...
The sitting duck appearance denotes the normal anatomical configuration of the jugular foramen:
the head of the duck (pointing backwards on the right side) represents the anteromedial pars nervosa
the body of the duck representing the pars vascularis
Sjögren syndrome is an autoimmune condition of exocrine glands that produce tears and saliva.
Sjogren syndrome is the second most common autoimmune disorder after rheumatoid arthritis. There is a recognised female predilection with F:M ratio of ≈ 9:1. Patients typically present a...
The skull AP view is a nonangled AP radiograph of the skull. This view provides an overview of the entire skull rather than attempting to highlight any one region.
the back of patient's head is placed against the image detector
the petrous ridge will overlap the lower 1/3 of ...
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...
A useful mnemonic to remember the six skull bones is:
STEP OF 6
6: number of skull bones
Skull landmarks of anatomic importance exist, located where there is a palpable bony protuberance or where sutures join:
They are surgical landmarks and craniometric points, used for radiological or ...
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
The Caldwell view is a caudally angled PA radiograph of the skull, designed to better visualize the paranasal sinuses, especially the frontal sinus.
patient is seated in front of the upright detector
the patient's forehead is placed against the image detector
forehead and no...
The skull PA view is a non angled PA radiograph of the skull. This view provides an overview of the entire skull rather than attempting to highlight any one region.
patient is erect
the patient's forehead is placed against the image detector allowing for the nose to be in con...
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...
Soft-tissue sarcomas are a heterogeneous group of malignant tumours of mesenchymal origin (sarcoma) that originate from the soft tissues rather than bone. They are classified on the basis of tissue seen on histology. The commoner sarcomas in the adult and paediatric population are listed below.
Solitary bone cysts of the mandible (a.k.a. traumatic bone cyst of jaw, haemorrhagic cyst of the mandible, extravasation cyst, progressive bone cavity or unicameral bone cyst) are an uncommon nonepithelial lined lucent mandibular lesion. It is one of a myriad of potential mandibular lesions.
Solitary median maxillary central incisor (SMMCI) is a rare dental anomaly. It is usually considered as a minor manifestation (variant) of holoprosencephaly (HPE).
It is estimated to occur in 1:50,000 live births.
It is a complex disorder consisting of multiple, mainly...
Lymphadenopathy is quite common, and it is many a time very difficult to differentiate malignant lymphadenopathy from reactive lymphadenopthy.
Several gray scale and colour doppler features favour malignancy in a lymph node.
Gray scale parameters that favour malignancy
size: larger-more likel...
The spheno-occipital suture marks the spheno-occipital synchondrosis, hosts 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.
Sphenoethmoidal air cell, also commonly known as the Onodi air cell, is an anatomical variant of the paranasal sinuses, important due to close proximity to optic nerve and internal carotid artery.
The sphenoethmoidal air cell is generally defined as the posterior most ethmoidal air...
The sphenoethmoidal recess drains the posterior ethmoid air cells and sphenoid sinuses into the superior meatus of the nasal cavity.
patterns of sinonasal obstruction
The sphenoethmoidal suture marks the osseous union between the crest of sphenoid bone and the perpendicular and cribiform plates of ethmoid bone.
The sphenofrontal suture is a cranial suture where the frontal bone meets the sphenoid bone bilaterally. From an anterior perspective of the skull, this suture appears in the roof of the bony orbits. From a lateral perspective, it appears as the meeting of the inferoposterior edges of the fronta...
The sphenoid bone is located at the base of skull.
Parts of the sphenoid bone include:
process and plates
The sphenoid bone articulates with twelve bones. Unpaired bones include: frontal, ethmoid, vomer, and occipital. Paired bone...
The sphenoid sinus is the most posterior paranasal sinus. It lies antero-inferior to the sella. It is important to look for the variable pneumatisation of this sinus and to report the relationship with neurovascular structures.
Pneumatisation starts at around 2 year of age and it develops more ...
Sphenoid wing dysplasia is a characteristic but not pathognomonic feature of neurofibromatosis type 1 (NF1), it can also occur in isolated cases.
Sphenoid wing dysplasia is seen in 5-10% of cases of NF1 and is one of the diagnostic criteria of NF1 5,6.
Its exact aetiol...
The sphenopalatine foramen is formed at the junction of the sphenopalatine incisure (palatine bone) with the sphenoid bone.The sphenopalatine foramen opens from the superior nasal meatus to the pterygopalatine fossa. It transmits the posterior superior nasal nerves and sphenopalatine vessels.
The sphenopetrosal suture is the cranial suture connecting the greater wind of sphenoid with the petrous part of temporal bone in the middle cranial fossa. This fissure forms part of the posterior wall of foramen lacerum.
The sphenosquamosal suture is a vertical cranial suture between the sphenoid and temporal bones bilaterally. It is formed by the articulation between the posterior border of the greater wing of the sphenoid bone and the anterior border of the squamous part of the temporal bone 1.
The sphenozygomatic suture is one of the paired cranial sutures formed by the junction of the sphenoid and zygomatic bones. Medially, it forms part of the lateral wall of the orbit. Laterally, it forms part of the anterior temporal fossa 1.
The spinal accessory nerve, also called accessory nerve, is the eleventh cranial nerve (CN XI) and is composed of two parts, the cranial part and the spinal part.
Connections and course
The cranial part (accessory portion) is the smaller of the two. Its fibers arise from the cells of the nucle...
The splenius capitis is a strap-like muscles that, along with the splenius cervicis, comprise the superficial layer of intrinsic back muscles.
origin: ligamentum nuchae, and the tips of the spinous processes and associated supraspinous ligaments of C7 and the upper t...
The splenius cervicis is part of the superficial layer of the intrinsic back muscles. It is one of the two muscles in this group, the other being the splenius capitis.
origin: transverse process of the atlas, tip of the transverse process of the axis, and posterior t...
The squamous/squamosal suture is the cranial suture between the temporal and parietal bones bilaterally. From the pterion, it extends posteriorly, curves inferiorly and continues as the parietotemporal suture.
Along with growth of the pterion, the asterion and at the frontozygomatic suture, gro...
Squamous cell carcinomas of the head and neck are common, being the sixth most common cancer. They can have a cutaneous or mucosal origin. As such there is a wide array of clinical and radiographic manifestations, and are separated into:
squamous cell carcinoma of the skin of the head and neck
Squamous cell carcinoma of the larynx is the most common primary malignant tumor that affects the laryngeal framework (98%). Typically it is categorised by the laryngeal subsite affected, which affects presentation, treatment and prognosis.
Male are more affected than females, an...
Squamous cell carcinoma of the oral cavity are the most common (by far) of the malignant lesions affecting this region.
As they share epidemiology, pathology and general principles with other squamous cell carcinomas of the upper aerodigestive tract, those topics are covered there. Below are a...
Squamous cell carcinoma of the tongue has tobacco smoking and alcohol ingestion as major risk factors and spans two regions: the anterior two-thirds (oral tongue) is a common subtype of squamous cell carcinoma of the oral cavity whereas the posterior third (base of tongue) is considered part of ...
The squamous part of the temporal bone (or squamous temporalis/squamous temporal bone) is a very thin bone and forms the anterosuperior aspect of the temporal bone.
The squamous temporal bone's outer convex surface provides attachment to the temporalis muscle and forms a boundary...
Stafne cyst (also known as a static bone cavity of the mandible or lingual salivary gland inclusion defect 4) is a cortical defect near the angle of the mandible below the mandibular canal. Strictly speaking, it is not a cyst since it does not contain any fluid. It is usually an incidental findi...
Staging of juvenile nasopharyngeal angiofibromas is performed with cross-sectional imaging, and relies on identification of local tumour extent, and invasion of adjacent spaces. For a discussion of this entity please refer to the parent article: juvenile nasopharyngeal angiofibroma.
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
A number of systems have been devised to stage retinoblastoma, with various end-points, and multiple systems are often used concurrently.
The Reese Ellsworth classification is assessed with fundoscopy and aims at predicting the chance of preserving the eye with external beam radiotherapy 3.
Staging of oral cavity squamous cell carcinoma uses the TNM staging system.
Primary tumour staging (T)
Tx - tumour cannot be assessed
T0 - no evidence of primary tumour
Tis - carcinoma in situ
T1 - tumour 2 cm or less in greatest dimension
T2 - tumour greater than 2 cm and less than 4 cm i...
Stapedius is a tiny muscle that attaches to the posterior aspect of the neck of the stapes, which when contracted dampens vibrations passed to the cochlea via the oval window. It is supplied by a small branch from the facial nerve. The muscle is anchored within the petrous temporal bone and emer...
The stapes is the smallest and most medial of the middle ear ossicles.
It has a base (foot piece / footplate) which seals the oval window and conducts vibrations to the cochlea. The base is attached to the neck via an anterior and posterior arch (also called anterior and posterior crura). On to...
Stapes prosthesis are used in the stapedectomy surgery procedure which aims to improve conductive hearing loss due to oval window closure secondary to otosclerosis or post inflammatory conditions. The procedure is also performed to correct congenital abnormalities or discontinuity or fracture re...
Staphyloma is the term given to an eye whose scleral-uveal coats are stretched with uveal protrusion. This most commonly occurs posteriorly, although anterior staphyloma also is recognised. As opposed to coloboma, staphyloma defect is located off-center from the optic disc, typically temporal to...
The steeple sign, also called wine bottle sign, refers to the tapering of the upper trachea on a frontal chest radiograph reminiscent of a church steeple. The appearance is suggestive of croup, which should be obvious clinically. A corresponding lateral x-ray would show narrowing of the subglott...
A stellate ganglion block can be used to treat a number of conditions by reducing stimulation of the stellate ganglion which is part of the sympathetic network.
The ganglion is formed by the inferior cervical and first thoracic ganglia and is located just anterior to the head of the first rib. ...
Stenvers view is a oblique radiographic projection used to demonstrate the petrous temporal bone, IAM and bony labyrinth. Fine slice multi-detector CT of the petrous bone has replaced the Stenver view due to far superior anatomic detail. It was also used to assess electrode placement following t...
The sternocleidomastoid (SCM) is a muscle of the neck. It has two heads that meld to form one insertion. SCM, along with the trapezius muscle, is invested by the superficial layer of the deep cervical fascia, which splits around it. SCM divides the neck into anatomical anterior and posterior tri...
The sternohyoid muscle is an infrahyoid muscle of the neck that is innervated by the ansa cervicalis of the cervical plexus receiving fibres from the ventral rami of C1-C3 spinal nerves. The sternohyoid is a paired, flat strap of muscle that serves to fix the hyoid bone as well as depressing the...
The sternothyroid muscle is an infrahyoid muscle of the neck that is innervated by the ansa cervicalis of the cervical plexus receiving fibres from the ventral rami of C1-C3 spinal nerves. The sternothyroid is a paired, flat strap of muscle that serves to fix the hyoid bone as well as depressing...
A stuck disc refers to a TMJ disc which does not translate anteriorly out of the mandibular fossa onto the articular eminence, but rather remains (thus "stuck") in the fossa. It is a form of TMJ dysfunction and is typically associated with restricted range of motion.
Treatment is wit...
The styloglossus muscle is one of the extrinsic tongue muscles.
origin - the apex of the styloid process adjacent to the origin of the stylomandibular ligament
insertion - merges with the hyoglossus and inferior longitudinal muscle of the tongue
nerve supply - hypoglossal nerve
The stylohyoid ligament forms part of the styloid apparatus. The origin is at the styloid process of the temporal bone and it inserts into lesser horn of the hyoid bone.
The stylohyoid ligament provides part of the origin for the middle pharyngeal constrictor muscle and styloglossus muscle. It ...
The stylohyoid muscle is a muscle in the neck.
origin: styloid process of temporal bone
insertion: hyoid bone
action: draws hyoid bone backward and elevates tongue
nerve supply: facial nerve (CN VII)