A useful mnemonic to remember the branches of the internal jugular vein is:
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From inferior to superior:
M: middle thyroid vein
S: superior thyroid vein
L: lingual vein
F: facial vein
P: pharyngeal vein
I: inferior petrosal sinus
The internal palpebral arteries, or medial palpebral arteries, are branches of the ophthalmic artery, with superior and inferior medial palpebral branches arising opposite the trochlear of the superior oblique muscle.
The internal palpebral arteries enter the superior and inferio...
The internasal suture is a single, midline cranial suture between the two nasal bones. It meets the frontonasal suture to form the nasion 1.
The interscalar septum is a thin bony plate that separates each turn of the cochlea 1.
It radiates from the modiolus laterally to the spiral ligament 2. Vessels (venules, arterioles and capillaries) run within the septum through bony canals 2.
Partial absence of the intersca...
The intraconal orbital compartment or intraconal space is the conical space within the orbit and musculofascial cone, the base of which is anterior and is formed by the posterior half of the globe. The sides are formed by the extraocular muscles and their surrounding fascia which pass posteriorl...
Intraconal orbital lesions are broadly divided into two main groups; those with or without involvement of the optic nerves:
Lesions with optic nerve involvement:
optic nerve glioma
optic nerve meningioma
lymphoma and leukaemia
Intracranial dermoid cysts are uncommon lesions with characteristic imaging appearances. They can be thought of as along the spectrum: from epidermoid cysts at one end (containing only desquamated squamous epithelium) and teratomas at the other (containing essentially any kind of tissue from all...
Intraductal papilloma of salivary gland (also known as an inverted ductal papilloma or sialadenoma papilliferum) is a benign relatively rare salivary gland tumour. '
They typically arise in adulthood and there may be a slight male predilection.
They may show a characte...
Intraosseous meningioma, also referred as primary intraosseous meningioma, is a rare subtype of meningioma that accounts for less than 1% of all osseous tumours. They fall under the subgroup of primary extradural meningiomas.
It is important to note that it has been argued by some ...
The intrinsic muscles of the larynx can be considered in two groups:
muscles that control the inlet of the larynx
muscles that move the vocal ligaments
Muscles of the inlet
aryepiglottic muscle: lies within the aryepiglottic fold, runs from the side of the epiglottis and inser...
The intrinsic muscles of the tongue are a group of 4 muscular bands in the tongue. In comparison to the extrinsic muscles of the tongue, they are entirely within the tongue with no external attachments. They act to alter the shape of the tongue where as the extrinsic tongue muscles alter the pos...
Inverted papillomas are a type of Schneiderian papilloma. They are uncommon with distinctive pathological and imaging features.
The term inverted papilloma is also used to describe a urothelial lesion. For a discussion of that entity, please refer to inverted papilloma of the urin...
Iodine123 (I123) is a radioisotope of the element iodine (atomic number 53) used in nuclear medicine imaging including to scan the thyroid gland.
Uses, dosages, and time of Imaging
routine scan: 100-400 microCi po, image at 4-6 or 24 hours
thyroid cancer scan: 1.5 mCi po, image at 4-6 or 24 ...
An isolated cleft palate is a type of facial cleft. This is a much rarer occurrence than a cleft lip +/- palate and is thought to represent a different pathological entity.
The estimated incidence is at ~1 per 2000-2500 pregnancies 4-5. There may be a slight female predilection 4....
Jaffe-Campanacci syndrome is characterised by:
multiple non-ossifying fibromas of the long bones and jaw
café au lait spots
hypogonadism or cryptorchidism
giant cell granuloma of the jaw
Jod-Basedow phenomenon is hyperthyroidism following iodine intake in a person with long term underlying thyroid disease.
Jod-Basedow phenomenon occurs due to either overactivation of the entire thyroid gland or, more commonly, autonomous nodules within the gland after iodine repletio...
The jugular foramen courses anteriorly, laterally, and inferiorly as it insinuates itself between the petrous temporal bone and the occipital bone.
The jugular foramen is usually described as being divided into two parts by a fibrous or bony septum, called the jugular spine, into...
The jugular fossa is a depression situated on the inferior surface of petrous temporal bone posterior to the inferior opening of carotid canal. It lodges the jugular bulb. Anteriorly, lies the jugular foramen.
glomus jugulare is the most common tumour of jugular fossa
Jugular fossa masses comprise a range of pathological lesions that arise from or extend into the jugular fossa in the skull base. Although not a common location for tumours it is not unusual for jugular fossa lesions to be discovered incidentally on cross sectional imaging.
The jugular spine is a small sharp bony ledge which separates the two parts of the jugular foramen - pars nervosa anteriorly and pars vascularis posteriorly. It is an important landmark, as masses of the jugular foramen (e.g. glomus jugulare) will erode this spine, helping distinguish them from ...
Juvenile nasopharyngeal angiofibromas (JNA) are a rare benign but locally aggressive vascular tumour.
Juvenile nasopharyngeal angiofibromas occur almost exclusively in males and usually in adolescence (~15 years). They account for only 0.5% of all head and neck tumours 2, but are ...
Staging of juvenile nasopharyngeal angiofibromas is performed with cross-sectional imaging and relies on the 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.
Kartagener syndrome is a subset of primary ciliary dyskinesia, an autosomal recessive condition characterised by an abnormal ciliary structure or function, leading to impaired mucociliary clearance.
The prevalence of primary ciliary dyskinesia is approximately 1 in 12,000-60,000 ...
Keratocystic odontogenic tumours (KCOT or KOT), previously known as odontogenic keratocysts, are benign cystic neoplasms involving the mandible or maxilla and are believed to arise from dental lamina. They are locally aggressive and tend to recur after excision.
On imaging, they typically appe...
Keratosis obturans (KO) is a rare external auditory canal disease characterised by abnormal accumulation and consequently occlusion and expansion of the bony portion of the EAC by a plug of desquamated keratin. It can be confused by EAC cholesteatoma but they are completely different entities re...
The Keros classification is a method of classifying the depth of the olfactory fossa.
The ethmoid labyrinth is covered by the fovea ethmoidalis of the frontal bone and separates the ethmoidal cells from the anterior cranial fossa.
The very thin, horizontal cribriform plate (lamina cribrosa) of...
Kiesselbach's plexus (Kiesselbach's area or Little's area) is a vascular region of the anteroinferior nasal septum that comprises four arterial anastomoses:
anterior ethmoidal artery
a branch of the ophthalmic artery
a branch of the maxillary artery
greater palatine ar...
Kimura disease is a rare benign inflammatory disease that characteristically manifests as enlargement of cervical lymph nodes and salivary glands.
Kimura disease typically affects males (80%) between 20 and 40 years of age (80% of cases) 1-2, and is most frequently seen in Asia. S...
The term kissing carotids refers to tortuous and elongated vessels which touch in the midline. They can be be found in:
within the pituitary fossa
within sphenoid sinuses
within sphenoid bones
The significance of kissing carotids is two-fold:
may mimic intr...
Koerner's septum is a thin bridge of bone which divides the petrous and squamous portion of the mastoid air cells at the level of the mastoid antrum. It is commonly eroded by middle ear cholesteatomas.
Küttner tumour (KT) refers to a chronic sclerosing sialadenitis of the salivary glands. Despite the term tumour, it is a non neoplastic condition. It is classically described in relation the submandibular gland but less commonly can also affect other salivary glands 9 and occassionally as well ...
The labyrinthine artery, also known as the auditory artery or internal auditory artery, is a long and slender artery that is the main arterial supply to the vestibular apparatus and cochlea.
It usually originates from the AICA (~85%), although it can also branch from the basilar artery (~15%), ...
Labyrinthitis ossificans (LO), also known as labyrinthine ossification, represents pathological ossification of the membranous labyrinth as a response to an insult to the inner ear.
It is usually associated with profound sensorineural hearing loss.
It most co...
The labyrinth or lateral mass of the ethmoid bone consists of a number of thin-walled cellular cavities, the ethmoidal cells, arranged in three groups, anterior, middle, and posterior, and interposed between two vertical plates of bone; the lateral plate forms part of the orbit, the medial, part...
The lacrimal apparatus consists of the lacrimal gland and the nasolacrimal drainage apparatus.
The gland produces tears secreted into the lateral aspect of the superior fornix. The serous fluid washes over the eye and is drained at the medial canthus by the superior and inferior lacrimal canal...
The lacrimal artery is a branch of the ophthalmic artery that supplies the lacrimal gland.
The lacrimal artery travels along the upper border of the lateral rectus muscle with the lacrimal nerve to supply the lacrimal gland as well as the eyelids and conjunctiva.
The lacrimal bones are paired craniofacial bones forming anterior aspect of the medial orbital walls.
The lacrimal bones have two surfaces and four borders. The lateral orbital surface is divided by a vertical posterior lacrimal crest with an anterior fossa for lacrimal sac and ...
The lacrimal canaliculi form the first part of the nasolacrimal drainage apparatus that drains tears produced by the lacrimal gland.
There are two lacrimal canaliculi - superior and inferior on each side. They commence at the superior and inferior lacrimal puncta, which drain te...
The lacrimal gland lies in the superolateral aspect of the orbit. It is part of the lacrimal apparatus and is responsible for tear production.
The lacrimal gland is roughly almond-sized and located anteriorly in the superolateral aspect of the extraconal space of the orbit. It h...
Lacrimal gland masses can be classified into two broad groups - inflammatory (~50%) and neoplastic, either lymphoma (25%) or salivary gland type tumours (~25%).
affects ~25% of patients with systemic disease
orbital inflammatory pseudotumour
The lacrimal nerve is the smallest branch of the ophthalmic division of the trigeminal nerve (V1).
The lacrimal nerve divides off the ophthalmic division of the trigeminal nerve (V1) just before entering the orbit through the superior orbital fissure outside and superolateral to ...
The lacrimal (or nasolacrimal) sac forms part of the nasolacrimal drainage apparatus. It is located in the preseptal part of the orbit.
The lacrimal sac lies in the lacrimal fossa on the inferomedial aspect of the bony orbit between the posterior and anterior lacrimal crests. Th...
The lacrimal sac fossa is an excavated fossa in the inferior aspect of the anteromedial orbital wall which contains the lacrimal sac. It is bounded by the anterior and posterior lacrimal crests of the maxillary and lacrimal bones, respectively. In adults, it measures approximately 8-9mm anteropo...
The lacrimomaxillary suture is a syndesmotic suture between frontal process of the maxilla and lacrimal bone in inferior aspect of anteromedial wall of the orbit approximately half way between the anterior and posterior lacrimal crests. It corresponds, internally, to the maxillary line in later...
Lagophthalmos refers to the inability of an individual to completely close the eyelids and can result in drying of the eyes and irritation and even permanent damage.
It is most commonly encountered in patients with facial nerve palsies (e.g. Bell's palsy) but can also result from scarring of th...
The lambda is the midline bony landmark where the lambdoid sutures and sagittal suture meet, between the occipital and two parietal bones. It may be a depression and therefore palpable. Accessory occiptal bones are common near the lambda, usually associated with the lambdoid sutures.
It is the ...
The lamdboid suture is the junction between the superior border of the occipital bone and the posterior borders of the right and left parietal bones.
Large vestibular aqueduct syndrome (LVAS) refers to the presence of congenital sensorineural hearing loss with an enlarged vestibular aqueduct. It is thought to be one of the most common congenital causes of sensorineural hearing loss (SNHL).
SNHL starts in childhood and...
The laryngeal cartilages form the "skeleton" of the larynx, of which there are a number:
arytenoid cartilage (paired)
cuneiform cartilage (paired)
corniculate cartilage (paired)
Laryngeal cysts can occur in any part of the larynx, but are more frequent in supraglottic locations, such as the epiglottis and vallecula. The prevalence of each location varies on different studies.
The laryngeal cysts represent a rare group, about 5%, of benign laryngeal lesio...
Laryngeal squamous cell carcinoma staging uses the TNM staging system and actual staging is subsite (see laryngeal subsites) specific for T1-3. A rough approximation for all subsites is
T1: limited to one subsite and normal cord mobility
T2: more than one subsite and impaired cord mobility (bu...
Laryngeal trauma is uncommon in the setting of external blunt or penetrating trauma. The larynx may also be injured internally, for example during endotracheal intubation.
Symptoms include hoarseness, laryngeal pain, dyspnoea, and/or dysphagia. Also, stridor, haemoptysis,...
Laryngocoeles refer to dilatations of the laryngeal ventricular saccule located in paraglottic space of supraglottis.
On imaging, these lesions are generally characterised as well-defined, thin-walled, fluid or air-filled cystic lesions in the paraglottic space. The communication with the laryn...
The larynx is a continuation of the oropharynx, and extends from the epiglottis (namely the glossoepiglottic and pharyngoepiglottic folds) to the inferior aspect of the cricoid cartilage. Inferiorly, it continues as the cervical trachea.
The larynx consists of a cartilage "skele...
The lateralised internal carotid artery is an anatomic variation of the course of the horizontal internal carotid artery (ICA). It can be visualised on CT by its more posterolateral entrance to the skull base and protrusion into the anterior mesotympanum. It may result in pulsatile tinnitus.
The lateral posterior inferior nasal nerve is a branch of the greater palatine nerve that supplies the posteroinferior nasal lateral wall.
The nerve branches off the greater palatine nerve in the greater palatine canal and exits the canal though a tiny un-named foramen in the pal...
The lateral pterygoid muscle, also known as pterygoideus externus or external pterygoid muscle, is one of the muscles of mastication.
The lateral pterygoid is a short, thick muscle, somewhat conical in form, which extends almost horizontally, posteriorly and laterally between th...
The lateral pterygoid nerves or nerves to lateral pterygoid muscle are a pair of motor branches of the anterior division of the mandibular division of the trigeminal nerve.
The two nerves divide off the anterior division and course along side the buccal nerve. Each nerve then pie...
The lateral rectus muscle is one of the 6 extra-ocular muscles that control eye movements. It is responsible for abduction and is the only muscle that is innervated by the abducens nerve (CN VI). It should normally measure 2.9 ± 0.6mm.
innervation: abducens nerve (CN VI)
A mnemonic for the layers of the scalp is:
This is particularly helpful when considering the location of a scalp haematoma.
C: connective tissue
A: (galea) aponeurosis
L: loose connective tissue
Le Fort fractures are fractures of the midface, which collectively involve separation of all or a portion of the midface from the skull base. In order to be separated from the skull base, the pterygoid plates of the sphenoid bone need to be involved as these connect the midface to the sphenoid b...
Leiomyosarcomas (LMS) are extremely rare malignant neoplasms that originate from smooth muscle cells and may be considered the malignant counterpart of a leiomyoma. They are classified as a soft tissue tumour and account for ~8% of malignant soft tissue tumours 10.
Lemierre syndrome refers to thrombophlebitis of the jugular veins with distant metastatic sepsis in the setting of initial oropharyngeal infection such as pharyngitis/tonsillitis with or without peritonsillar or retropharyngeal abscess.
Patients typically present unwell...
The lentiform nodule (also known as the lenticular process) is the inferior most part of the incus which articulates with the head of the stapes.
Leptomeningeal cysts, also known as growing skull fractures, are an enlarging skull fracture that occurs near post-traumatic encephalomalacia. The term cyst is actually a misnomer, as it is not a cyst, but an extension of the encephalomalacia. Hence, it is usually seen a few months post-trauma.
The lesser occipital nerve, also known as the small occipital nerve, is a cutaneous branch of the cervical plexus that innervates the skin of the neck and scalp posterior and superior to the auricle.
The lesser occipital nerve arises from the ventral ramus of C2, although...
The lesser palatine foramina are 2 small foramina representing the openings in the hard palate of the lesser palatine canal (which is a small accessory canal arising form the greater palatine canal). They are located in the posterior palatine bone posterior to the greater palatine foramen and po...
The lesser palatine nerves (or posterior palatine nerves) are a group of 2 to 3 nerves (usually 2 nerves) that arise of the maxillary division of the trigeminal nerve and contributes to the pterygopalatine ganglion.
The lesser palatine nerves divide off the maxillary division jus...
The lesser petrosal nerve carries parasympathetic (secretory) fibers from both the tympanic plexus and the nervus intermedius, to the parotid gland. The tympanic plexus arises from glossopharyngeal nerve (CN IX) via Jacobson's nerve.
The lesser petrosal nerve originates at the geniculate gangli...
The lesser wing of the sphenoid bone, or orbito-sphenoid, is a sharp, pointed triangular plate arising laterally from the upper anterior portion of the sphenoid body.
The lesser wing features both superior and inferior surfaces:
the superior surface is flattened and is in conta...
Leukocoria (also spelled as leucocoria or leukokoria) refers to an abnormal white reflection from the retina of the eye. Despite its colour, the reflection is related to the familiar red-eye effect. Usually, when a light is shone through the iris, the retina appears red to the observer. In leuko...
The levator palpebrae superioris muscle is a small muscle of the superior orbit that elevates and retracts the upper eyelid. It is not part of the extra-ocular muscles; it does not insert on the globe and therefore does not produce eye movements. It is mostly composed of skeletal muscle but ther...
The levator veli palatini is one of the 5 paired muscles of the soft palate. It is a cylindrical muscle which together form a V-shaped sling behind and above the soft palate.
origin: it has 2 sites of origin:
inferior surface of petrous temporal bone
medial rim of the auditory tube
The Lillie-Crowe sign is used in the diagnosis of unilateral sinus thrombophlebitis. Digital compression of the opposite internal jugular vein causes dilatation of the retinal veins.
The lingual artery is one of the branches of the external carotid artery and supplies the oral floor and tongue.
origin: branch of the external carotid artery at the level of the C3
course: towards hyoid bone, then loops down towards the tongue
supply: oral floor and tongue
The lingual nerve is a sensory branch of the posterior division of the mandibular division of the trigeminal nerve.
The lingual nerve divides off the posterior division and descends anterior to the inferior alveolar nerve to course between the lateral pterygoid and tensor veli pa...
A lingual thyroid is a specific type of ectopic thyroid and results from the lack of normal caudal migration of the thyroid gland.
The condition is congenital and there is a female predilection 1-3.
Many patients are asymptomatic and the diagnosis is made i...
The lingual tonsils are aggregations of lymphoid follicles that mediate B- and T-cell lymphocytes, which serve a role in formulating the immune system. They are covered by stratified squamous nonkeratinized epithelium and contain deep crypts and mucosal glands. They form a part of the Waldeyer r...
Lingula (plural lingulae) can refer to a number of different anatomical structures:
lingula (sphenoid bone)
History and etymology
Lingula is the diminutive form of lingua, Latin for the tongue. Thus lingula is used for a small tongue-l...
The lingula of the mandible (also known as Spix spine) is a triangular bony projection or ridge on the medial surface of the ramus of the mandible, immediately superior to the mandibular foramen. It provides attachment for the sphenomandibular ligament 1,2.
History and etymology
The parotid gland consists of a superficial and deep lobe. Determining the location and extent of the lesions affecting the gland is an essential aspect of imaging and vital information which needs to be conveyed to the surgeon.
Method of evaluation
The following lines are proposed for differe...
Locked in syndrome (LIS) is a condition that can occur as a result of a stroke involving the brainstem; the stroke damages the ventral brainstem, corresponding to the pyramidal bundles.
The infarct is pontine; the midbrain is preserved. The oculomotor nerve III is intact ...
The long ciliary nerves are a group of nerves that branch from the nasociliary nerve in the intraconal space. Along with the short ciliary nerves, they supply sensation to the entire globe excluding the conjunctiva. Unlike the short ciliary nerves however, they bypass the ciliary ganglion and he...
Longitudinal temporal bone fractures are petrous temporal bone fractures that occur parallel to the long axis of the petrous temporal bone. Although more current classifications of the extent of temporal bone fractures focus on the integrity of the otic capsule rather than the fracture orientati...
Petrous temporal bone fractures are classically divided into longitudinal, transverse or mixed fracture patterns depending on the direction of fracture plane with respect to the long axis of the petrous temporal bone. Some features may aid in distinguishing them.
The longus capitis muscle is a prevertebral muscle of the neck that is innervated by muscular branches of the cervical plexus. In isolation longus capitis acts to laterally flex and rotate the head.
origin: anterior tubercles of C3-C6 transverse processes
insertion: inferior surface o...
The longus colli muscle is a prevertebral muscle of the neck that is innervated by the anterior rami of C2–C6 from the cervical plexus. Longus colli is a weak flexor the cervical spine and when contracting unilaterally it tilts and rotates the cervical spine to the ipsilateral side. Longus colli...
Low attenuation lymphadenopathy suggests underlying necrosis and can be seen in:
metastatic carcinoma (or lymphoma)
infections (tuberculous or fungal)
low attenuation lymphadenopathy
high attenuation lymphadenopathy
Ludwig angina refers to rapidly progressive inflammation (cellulitis) of the floor of mouth, which is potentially life threatening due to the risk of rapid airway compromise.
Largely due to the advent of antibiotics the condition is uncommon in present day modern societies. Immun...
Lymph node enlargement is often used synonymously with lymphadenopathy, which is not strictly correct.
Lymphadenopathy (or adenopathy) is, if anything, a broader term, referring to any pathology of lymph nodes, not necessarily resulting in increased size; this includes abnormal num...
Lymph nodes in the neck have been divided into seven levels, generally for the purpose of squamous cell carcinoma staging. This system is not inclusive of several important groups, however, such as the supraclavicular, parotid, retropharyngeal space, and occipital nodes.
The lyre sign refers to the splaying of the internal and external carotid by a carotid body tumour. Classically described on angiography it is also visible on CT angiography.
The MacEwen triangle (also called the suprameatal triangle or mastoid fossa) is a small triangular depression affecting the inner table of the temporal bone.
The lines forming the triangle are:
anterior: posterior border of the external acoustic meatus
superior: posterior root of the zygomati...