The sagittal suture is the midline that joins the two parietal bones.
fusion of the sagittal suture results in scaphocephaly
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:
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 neoplasms, the submandibular gland 50:50, and the sublingual glands a...
Only a minority of salivary gland tumour types show uptake on 99Tc scintigraphy
oncocytoma of salivary glands
haemangioendothelioma of salivary glands 1
The salpingopharyngeus is a muscle of the head and neck, and one of the inner longitudinal muscles of the pharynx. The paired slender muscles create vertical ridges of mucous membrane in the posterior pharyngeal wall descending from the medial ends of the Eustachian tubes to the called the salpi...
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 ...
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...
Scala media, also known as cochlear duct, is an endolymph filled cavity in the cochlea located between the scala vestibuli (upper) and the scala tympani (lower). It is separated from the scala vestibuli by Reissner's membrane (vestibular membrane). It houses the organ of Corti.
The scala tympani, also known as tympanic duct, is the inferiormost duct of the cochlea. It is filled with perilymph and communicates directly with the subarachnoid space.
It is separated from the scala media and scala vestibuli by the spiral lamina.
The scala vestibuli, also known as vestibular duct, is the superiormost duct of the cochlea. It is filled with perilymph and communicates directly with the subarachnoid space.
It is separated from the scala media by Reissner's membrane (vestibular membrane) and from the scala tympani by the spi...
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 (scalene tuberc...
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...
The scalp is the skin and subcutaneous tissue covering the neurocranium. It is composed of five layers and has a rich vascular supply which explains why it bleeds profusely and heals well.
The scalp is composed of five layers which are easily remembered with this mnemonic. From external...
Schneiderian epithelium/membrane is the unique lining of the nasal cavity and paranasal sinuses, and is an 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...
Sclerosing osteomyelitis of Garré is a specific type of chronic osteomyelitis. It mainly affects children and young adults. It typically affects the mandible and is commonly associated with an odontogenic infection resulting from dental caries.
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 space.
acquired cholesteatoma: it is usually the first bony structure to be eroded by the enl...
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...
Semicircular canal dysplasia is relatively common of the labyrinthine anomalies. About 40% of patients with a malformed cochlea will have associated lateral semicircular canal (SCC) dysplasia.1 The other two common labyrinthine anomalies include SCC aplasia and SCC dehiscence.
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 othe...
Shock thyroid is an uncommon part of the hypovolemic shock complex.
It was initially described in 2016 as heterogenous thyroid contrast enhancement and fluid surrounding the thyroid in trauma CT of shocked patients without evidence for direct thyroid injury 2. Only 7 cases have been described ...
The short ciliary nerves are a group of nerves that branch from the nasociliary nerve in the intraconal space via the ciliary ganglion. Along with the long ciliary nerves, they supply sensation to the entire globe excluding the conjunctiva. The nasociliary nerve provides a small sensory componen...
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 midfacial 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 has also been described.
suspected sialolithiasis or s...
Sialolithiasis refers to the 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 the most common disease of salivary glands, accounting for approximately 50%...
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 the 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 the ve...
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 America 4
naso-ethmoidal encephalocoele (30%): more common in North America 4
Sinonasal adenocarcinomas are an uncommon form of head and neck cancer with squamous cell carcinomas more common.
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 Sistrunk procedure consists of removing a thyroglossal duct cyst and surrounding tissues.
The rationale for this procedure is that cure of the thyroglossal duct cysts will be unsuccessful unless the epithelium-lined tract (extending from the cyst to the foramen caecum) is completely remove...
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.
Sjögren 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 sagittal images from MRI or CT.
Angle formed by:
line joining the nasion with the centre of the pituitary fossa
line joining the anteri...
A useful mnemonic to remember the six skull bones is:
STEP OF 6
6: number of skull bones
The Caldwell view is a caudally angled PA radiograph of the skull, designed to better visualise the paranasal sinuses, especially the frontal sinus.
the patient is seated in front of the upright detector
the patient's forehead is placed against the image detector
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 ...
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.
the patient is erect
the patient's forehead is placed against the image detector allowing for the nose to be in...
The Towne view is an angled AP radiograph of the skull.
the patient's nuchal ridge is placed against the image detector
dorsum sella overlies the foramen magnum
image size: 24 x 30 cm
X-ray beam features
the beam travels anterior to posterior (AP) direction, with ~30-40° o...
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 occipitomental (OM) or Waters view is an angled PA radiograph of the skull, with the patient gazing slightly upwards. It can be used to assess for facial fractures, as well as for acute sinusitis. Skull radiographs, in general, are rapidly becoming obsolete, being replaced by much more sensi...
The small communicating branch of the ciliary ganglion is a small branch of the nasociliary nerve which supplies sensory fibres through the ciliary ganglion. These fibres do not synapse in the ganglion but pass directly into the short ciliary nerves to supply sensation to the sclera, cornea, iri...
Snake eyes is a term used to refer to the appearance of the facial nerve on coronal CT within its canal in the petrous temporal bone as the tympanic segment doubles back next to the labyrinthine segment adjacent to the cochlea. Anteriorly, these two segments converge at the geniculate ganglion.
The soft palate is the posterior part of the palate that is a mobile fold of soft tissue attached to the posterior border of the hard palate which laterally fuses with the lateral wall of the oropharynx. On its inferior oral surface it is lined by oral mucosa (which contains innumerous palatine ...
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 (also known as traumatic bone cyst of the 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 l...
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...
Sphenoethmoidal air cell, also commonly known as the Onodi air cell, is an anatomical variant of the paranasal sinuses, important due to its close proximity to the optic nerve and internal carotid artery.
The sphenoethmoidal air cell is generally defined as the posteriormost ethmoi...
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. The sinus is often divided by a central septum, and in this context ...
A sphenoid sinus mucocele is a location-specific subtype of a paranasal sinus mucocele.
Sphenoid sinus mucoceles are uncommon and only account for around 1-2 % of all paranasal sinus mucoceles 1-7.
Can be variable and range from deep-seated headaches to cr...
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 sphenomandibular ligament is one of the 2 extrinsic ligaments of the mandible. It descends from the spine of the sphenoid bone onto the medial surface of the mandibular ramus, attaching to the lingula. It is the primary passive support of the mandible, along with the muscles of mastication.
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.
The sphenopalatine artery, formerly known as the nasopalatine artery, is the terminal branch of the maxillary artery that is the main supply to the nasal cavity. It is colloquially know as the artery of epistaxis given its common involvement in cases of nose bleeds. It is a major contributor to ...
The sphenopalatine foramen connects the nasal cavity and the pterygopalatine fossa, transmitting the nasopalatine nerve, posterior superior nasal nerves, and sphenopalatine artery and vein.
It is formed at the junction of the sphenopalatine incisure (palatine bone) with the sphen...
The sphenopetrosal suture is the cranial suture connecting the greater wing of sphenoid with the petrous part of temporal bone in the middle cranial fossa. This fissure forms part of the posterior wall of the 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 spiral ganglion is a group of nerve cells located in the modiolus that enables the sense of hearing by sending a representation of sound from the cochlea to the brain.
The body of these nerve cells emits a peripheral process that contacts acoustic receptors in the organ of Corti and a centr...
The cochlear spiral lamina is a thin bone structure that projects from the modiolus, separating the cochlear canal in two main components or scala, the scala tympani (lower portion) and the scala vestibuli (upper portion).
At the cochlear apex, the spiral lamina ends in a hook-shaped process ca...
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: spinous processes of T3-T6
insertion: transverse processes of C1-C3
innervation: dorsalrami of the lower cer...
The squamomastoid suture represents the articulation between the squamous and mastoid portion of the temporal bone. It may form a ridge.
The squamosal or squamous 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, ...
Squamous cell carcinomas (SCC) 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...
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...
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...
Squamous cell carcinoma of the oral cavity is 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 ...