Sinonasal polyposis refers to the presence of multiple benign polyps in the nasal cavity and paranasal sinuses.
It is most commonly encountered in adults and rare in children. Polyps are the most common expansile lesions of the nasal cavity 8. Incidence increases in patients with ...
Sinonasal respiratory epithelial adenomatoid hamartoma (REAH) is a rare benign glandular neoplasm of the sinonasal cavities. It is most commonly encountered within the olfactory clefts.
It is most often encountered in middle-aged adults with no definite gender predilection 1,2.
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 lateralis is a general term used to described a space behind and/or superior to the ethmoid bulla. As it actually refers to both the suprabullar and retrobullar recesses, the use of these more specific terms is preferred.
Sinus pericranii 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 communication ...
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 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...
Skull radiography is the radiological investigation of the skull vault and associated bony structures. Seldom requested in modern medicine, plain radiography of the skull is often a last resort in trauma imaging in the absence of a CT. However, it is still utilised in the setting of skeletal su...
The Towne view is an angled AP radiograph of the skull, used to evaluate for fractures of the skull and neoplastic changes
the patient's nuchal ridge is placed against the image detector
the infraorbitomeatal line (IOML) is perpendicular to the image receptor
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-eye appearance refers to symmetric bilateral T1 hypointensity/T2 hyperintensity of the anterior horn of the grey matter on axial cervical MRI, evocative of a pair of snake's eyes.
It can be seen in late phase CT myelography, an all but forsaken technique, where it is also known as fried e...
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 can be very difficult to differentiate malignant lymphadenopathy from reactive nodal enlargement.
Several gray scale and colour Doppler features favour malignancy in a lymph node.
Gray scale parameters that favour malignancy
size: larger-more likely mal...
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 sphenoidal ridge is the sharp curving line along the superior border of the greater wing of the sphenoid bone, separating the horizontal posterior part of the anterior cranial fossa in front from the vertical anterior wall of the middle cranial fossa behind.
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.
location: the central body of the sphenoid bone anteroinferior to the sella turcica
blood supply: posterior ethmoidal and sphenopalatine arteries
innervation: posterior ethmoidal nerve and orbital branch of pterygopalatine gan...
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, containing the hyaline cartilage bridging the basisphenoid and basiocciput. It fuses at 12-13 years in girls and 14-15 years in boys and completely ossifies by 20-25 years.
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 the temporal bone in the middle cranial fossa. This fissure is located immediately posterior to the foramen ovale and 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. It is located l...
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...
Spinal stenosis is a condition in which a portion of the spinal canal narrows to the point at which it can exert pressure on the nerves that travel through the spine (spinal cord or cauda equina).
Spinal stenosis is not to be confused with foraminal stenosis which is the narrowing of the forami...
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: dorsal rami of the lower ce...
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 tumour 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, a...
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 ...
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 ...
Squamous odontogenic tumour is a rare, benign epithelial odontogenic neoplasm.
They generally occur in adults, but have a wide age range with cases reported from childhood to the 8th decade
It is considered to represent a proliferation of mature squamous epithelium and...
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...
Stab wounds are a form of penetrating trauma that may be self-inflicted or inflicted by another person either accidentally or intentionally. They may be caused from a variety of objects and may occur anywhere in the body.
Although commonly caused by a knife as well, slash injuries ...
Stafne cysts, also known as a static bone cavity of the mandible or lingual salivary gland inclusion defect, are cortical defects 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 findin...
The stapedius is the tiny muscle in the middle ear 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. The muscle is anchored within the petrous temporal bone and emerges into the tympanic cavity at...
The stapes is the smallest and most medial of the middle ear ossicles. It is the smallest bone in the standard human skeleton.
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 anterior and posterior a...
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 stellate ganglion is formed by the inferior cervical and first thoracic ganglia and is located just anterior to the head of the first rib. It receives input from the paravertebral sympathetic chain and provides sympathetic efferents to the upper limbs, head, neck, and heart.
The stellate ga...
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 infiltration of local anaesthetic/neurolytic around the 1 cm ganglion has been used to treat a variety of disorders.
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...
Steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT), also known as Hashimoto encephalopathy, is a rare and well-recognised neurological complication of autoimmune thyroid disease and occurs independently of the thyroid status. Patients exhibit neurological symptoms i...
A stuck disc refers to a temporomandibular joint (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.
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, and deep fibres of the ligament itself
insertion: merges with the hyoglossus and inferior longitudinal muscle of the tongue
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 one of the suprahyoid muscles of the neck. Its lower end divides allowing passage of the digastric tendon. Stylohyoid draws the hyoid bone backwards during swallowing.
origin: styloid process of temporal bone
insertion: hyoid bone
action: retracts and eleva...
The styloid apparatus, found within the parapharyngeal space, refers to the structures derived from the 2nd branchial arch along with associated ligaments and muscles:
styloid process of the temporal bone
lesser horn of the hyoid bone
The styloid process (or styloid part of the squamous temporal bone) is a slender pointed part of the temporal bone. It projects anteroinferiorly from the inferior surface of the temporal bone.
It serves as an anchor point for several muscles associated with the tongue and larynx:
The stylomandibular ligament is a cord-like condensation of the deep cervical fascia that extends from the apex of the styloid process of the temporal bone to the angle of the mandible. It is one of the 2 extrinsic ligaments of the mandible. The ligament separates the masseter and parotid gland ...
The stylomandibular tunnel is a space between the mandibular ramus and the styloid process / stylohyoid ligament. It separates the (prestyloid) parapharyngeal space from the carotid space (a.k.a. poststyloid parapharyngeal space).
When there is a mass in the region of the par...
The stylomastoid foramen is a rounded opening on the inferior surface of the petrous temporal bone, between the base of styloid and the mastoid process of the temporal bone. It transmits the facial nerve.
The stylopharyngeus is a muscle of the head and neck, and one of the inner longitudinal muscles of the pharynx.
origin: styloid process of the temporal bone
insertion: thyroid cartilage
innervation: glossopharyngeal nerve (CN IX)
action: elevates the larynx and pharynx; swallowing
Subacute lymphocytic thyroiditis or silent thyroiditis is a thyroid inflammatory condition.
Usually characterised by recent onset of symptoms and there is usually an absence of thyroidal pain or tenderness. On examination there can be a normal to modestly enlarged and fi...
Subclavius posticus is an accessory muscle in the root of the neck, lying between the subclavius muscle and the inferior belly of omohyoid. It has an incidence of ~ 7.5% 2,4.
origin: first costal cartilage
insertion: superior margin of scapula
nerve supply: nerve to subclavius or sup...
Subconjunctival fat prolapse is an acquired herniation of intraconal fat due to the weakening of the Tenon capsule by normal aging, surgery, or trauma. It presents clinically with a fat-containing epibulbar mass in the lateral canthal area.
Subconjunctival fat prolapse occurs mai...
Subgaleal haematoma describes scalp bleeding in the potential space between the periosteum and the galea aponeurosis. It is a rare but possibly lethal emergency.
Moderate to severe presentations occur in 1.5 of 10 000 live births. It most commonly occurs after vacuum-assisted and ...
Subgaleal lipomas are benign adipose-containing tumours that occur between the periosteum and the galea aponeurosis of the scalp.
They comprise 2% of all lipomas. They are more common in middle-aged patients and have a male predilection
Subgaleal lipomas pr...
The subglottis is the anatomical region caudal to the true vocal cords and is a subsite of the larynx.
The inferior arcuate line of the vocal cord marks the cranial border whilst the lower margin of the cricoid cartilage marks the caudal border of the subglottis 1. The inferior arcuate line is ...
The sublingual glands are salivary glands that lie in the floor of the mouth anterior to the submandibular glands. They secrete predominantly mucous saliva that is drained by a collection of 8-20 excretory ducts collectively termed the duct of Rivinus. The largest of these ducts, the major subli...
The sublingual space is one of the suprahyoid deep spaces of the head and neck.
It is like an inverted V with its apex pointing anteriorly and is located between:
tongue musculature superiorly
and the anterior one-third of the mylohyoid muscle inferolaterally which separates it...
The submandibular duct (also known as Wharton's duct) allows the passage of saliva from the submandibular gland to the sublingual papilla located anteriorly.
The duct extends anteriorly from the submandibular gland superior to the lingual nerve and submandibular ganglion curving over the poster...
The submandibular ganglion is one of four parasympathetic ganglia of the head and neck. It receives parasympathetic fibres from the facial nerve.
small ganglion suspended from the undersurface of the lingual nerve
inferior to submandibular duct sitting on the hyoglossus muscle
The submandibular glands are paired salivary glands located behind and below the ramus of the mandible in the submandibular triangle. They secrete mixed serous and mucous saliva that is excreted into the oral cavity via the submandibular duct that connects the gland to the floor of the mouth.
The submandibular space is a U-shaped compartment of the suprahyoid neck.
The superficial layer of the deep cervical fascia encloses the submandibular space.
medially: anterior belly of digastric muscles (separating it from the submental sp...
The submental space lies in the midline below the chin, medially to the U-shaped submandibular space with which it freely communicates.
superiorly: mylohyoid muscle
inferiorly: superficial layer of the deep cervical fascia
laterally: anterior bellies of the digastr...