The lamina cribrosa (rare plural: laminae cribrosae) is an anatomical term that is commonly used for two different structures in the head and neck region:
lamina cribrosa of the ethmoid bone
lamina cribrosa of the sclera
Also note that the macula cribrosa of the vestibule of the inner ear has...
The lamina cribrosa sclerae (also known as the lamina cribrosa of the sclera) is a net-like structure covering a small hole in the posterior sclera through which the optic nerve (II) and central retinal artery and vein pass.
The lamina papyracea, also known as the orbital lamina of the ethmoid bone, is the principal component of the medial wall of the orbit, and also the lateral surface of the ethmoid air cells.
superiorly with the orbital plate of the frontal bone
inferiorly with t...
Dehiscence of the lamina papyracea is an anomaly of the paranasal sinuses represented by a defect of the medial orbital wall. It is thought to be a benign congenital variant of no clinical significance.
Almost all patient tend to be asymptomatic, according to one study 2....
Large vestibular aqueduct syndrome (LVAS), also known as enlarged vestibular aqueduct (EVA) or large endolymphatic sac anomaly (LESA), refers to the presence of congenital sensorineural hearing loss with an enlarged vestibular aqueduct due to enlargement of the endolymphatic duct. It is thought ...
Laryngeal carcinoma staging refers to TNM staging of carcinomas involving the supraglottic, glottic, and subglottic larynx. The vast majority of applicable cases are squamous cell carcinomas, but other epithelial tumors are also included. The following article reflects the 8th edition published ...
The laryngeal cartilages form the "skeleton" of the larynx. There are three unpaired (midline) and three paired cartilages:
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...
The laryngeal saccule is a mucosa-lined pouch that arises from the anterior aspect of the roof of the laryngeal ventricle. It is most prominent in newborns but involutes during childhood.
medial: false vocal cords
lateral: thyroid cartilage
Dilatation of the lary...
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, dyspnea, and/or dysphagia. Also, stridor, hemoptysis, s...
The laryngeal ventricle is a slitlike, mucosa-lined, space located between the true and false vocal cords. It is often seen on lateral radiographs of the neck as an air-filled space between the true and false vocal cords. It should not be confused with the laryngeal vestibule.
The laryngeal vestibule is the part of the laryngeal cavity lying between the laryngeal inlet and vocal folds.
It is found within the supraglottis. It has a wedge-shaped cross-section, its base lying anteriorly, with its apex tapering posteriorly.
anterior: tubercle ...
Laryngocele refers to dilatation of the saccule of the laryngeal ventricle and is unilateral in the vast majority of cases 8.
On imaging, these lesions are generally characterized as well-defined, thin-walled, fluid or air-filled cystic lesions in the paraglottic space. The communication with t...
The larynx is an inferior continuation of the oropharynx. It 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 also forms part of the upper respirato...
The lateralized internal carotid artery is an anatomic variation of the course of the petrous segment of the internal carotid artery (ICA). It can be visualized on CT by its more posterolateral entrance to the skull base and protrusion into the anterior mesotympanum.
The lateral lamella (also known as the lamina lateralis) is the name given to the lateral boundary of the cribriform plate of the ethmoid bone. It runs vertically and joins the fovea ethmoidalis inferomedially. It is the thinnest part of the cribriform plate.
The lateral lamel...
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 extraocular 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 ± 0.6 mm.
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 hematoma.
C: connective tissue
A: (galea) aponeurosis
L: loose connective tissue
Maxillodental leave alone lesions are usually incidental findings that do not require treatment nor follow-up if the patient is asymptomatic.
This article includes findings from orthopantomogram, cone-beam CT, and sinus CT studies.
Do not touch:
Leave alone lesions are findings that are usually discovered incidentally and do not require any specific treatment or follow-up if the patient is asymptomatic.
This article includes findings from paranasal sinus CT and MRI studies.
Leave alone lesions of the skull base refers to incidental findings that do not require treatment nor follow-up.
This article includes findings from brain CT, HRCT of the temporal bone, and MRI studies.
Do not touch:
arrested pneumatization of the skull base - sphenoid benign fatty lesion 1
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 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 tumor and account for ~8% of malignant soft tissue tumors 10.
Lemierre syndrome (also known as postanginal septicemia) refers to thrombophlebitis of the internal jugular vein(s) with distant metastatic sepsis in the setting of initial oropharyngeal infection such as pharyngitis/tonsillitis with or without peritonsillar or retropharyngeal abscess.
Lenticonus is a rare congenital abnormality characterized by conical bulging of the posterior or anterior lens surface. If the bulging is global rather than conical, the condition is referred to as lentiglobus 1.
It produces a decrease in visual acuity and irregular refra...
Lentigo maligna, also known as Hutchinson freckle, is a non-familial precursor to lentigo maligna melanoma, which accounts for 5-15% of cases of malignant melanoma. It is most frequent in the head and neck.
It should not be confused with numerous other Hutchinson named entities including:
Leontiasis ossea is largely a historical term used to describe a number of conditions that result in the affected patient's face resembling that of a lion. Although it is most frequently associated with craniofacial fibrous dysplasia, it has a broader meaning encompassing other lesions that have...
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 preganglionic parasympathetic fibers to the parotid gland. It is considered a branch of the glossopharyngeal nerve although it receives contributions from two further sources 3:
tympanic plexus: glossopharyngeal nerve via Jacobson's nerve (main contribution)
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 color, 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 leukoc...
The levator claviculae or cleidocervical muscle is an uncommon accessory muscle in the neck that may be mistaken for a neck mass.
origin: transverse process of upper cervical vertebra
insertion: middle or lateral third of the clavicle
innervation: branches of the cervical plexus
The levator glandulae thyroideae muscle (a.k.a. musculus levator glandulae thyroideae or levator glandulae thyroideae of Soemmerring) is an anatomic variant, consisting of a band of fibrous/fibromuscular tissue, connecting the pyramidal lobe of the thyroid to the hyoid bone. When muscle fibers a...
Levator labii superioris alaeque nasalis (LLSAN) muscle is traditionally thought of as a muscle of the mouth, but is also a crucial muscle of the nose, a subset of the muscles of facial expression 1.
origin: maxilla, nasal bone, medial canthus
insertion: nasal base
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 extraocular muscles; it does not insert on the globe and therefore does not produce eye movements. It is composed of skeletal striated muscle fibers ...
The levator veli palatini muscle 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 two sites of origin:
inferior surface of petrous temporal bone
medial rim of the audito...
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.
Linear scleroderma, also known as scleroderma en coup de saber, is a very focal form of scleroderma classically characterized by a linear band of atrophy involving the frontal or frontoparietal scalp and subjacent thinned calvaria associated with ipsilateral focal brain abnormalities.
In the b...
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 supplying sensation (both gustatory (taste) and non-gustatory) to the anterior two-thirds of the tongue.
The lingual nerve divides off the posterior division and des...
A lingual thyroid is a specific type of ectopic thyroid and results from the lack of normal caudal migration of the thyroid gland.
NB: Location at the base of the tongue aside, the information in this article can relate to any ectopic thyroid tissue.
The condition is congenital a...
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...
The lingual vein is formed by the sublingual, deep lingual, and dorsal lingual veins 1. It is a paired vein draining the tongue.
The lingual veins accompany the lingual artery between the hyoglossus and genioglossus and enters the internal jugular vein near the greater horn of th...
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-...
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
Lipedematous scalp is a rare condition characterized by the accumulation of fatty tissue in the subcutaneous layer of the scalp, resulting in soft enlargement of the head. If it is associated with loss of hair then the term lipedematous alopecia is used.
Histology demonstrates incre...
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 is one of the brainstem stroke syndromes and can occur as a result of a pontine stroke that damages the ventral brainstem, pyramidal bundles and corticobulbar tracts 5.
Individuals who are "locked-in" are conscious with preserved cognitive function but ...
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 refers to abnormal lymph nodes that on CT appear to have lower attenuation than other soft tissues. This category can be split into two types:
cystic (necrotic) lymph nodes
metastatic carcinoma (or lymphoma)
infections (tuberculous or fungal)
Ludwig angina (cellulitis) refers to rapidly progressive inflammation 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. Immu...
The Lund-Mackay score is a widely used method for radiologic staging of chronic rhinosinusitis 1.
When reading a CT scan of the paranasal sinuses and ostiomeatal complex, the reader assigns each sinus a score of:
0 (no abnormality)
1 (partial opacification) or
2 (complete opacification)
Lymph node enlargement (rarely lymphadenomegaly) 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; ...
The lymph nodes in the neck have historically been divided into at least six anatomic neck lymph node levels for the purpose of head and neck cancer staging and therapy planning. Differing definitions exist across specialties 1-4. The following is a synthesis of radiologically useful boundaries ...
Lymphoscintigraphy is a nuclear medicine technique to visualize regional lymphatic drainage, especially for mapping sentinel lymph nodes, from a site of radiopharmaceutical injection.
Colloidal agents are used as these particles enter lymphatic channels and migrate to lymph...
The lyre sign refers to the splaying of the internal and external carotid by a carotid body tumor. 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...
Macroglossia means an enlarged tongue. It may be absolute (greater than the 95th centile) or relative (enlarged compared with oral cavity).
Recognized associations include:
tends to be a relative macroglossia
may also have intermi...
The increased globe size or macrophthalmia may have many differentials:
buphthalmos (congenital glaucoma)
macrophthalmus in neurofibromatosis type 1 (NF1)
connective tissue disorders: Marfan syndrome, Ehlers-Danlos syndrome
The macula cribrosa is part of the vestibule of the inner ear, located medially between it and the lateral most part of the internal acoustic meatus. It represents clusters of small foramina that permit the passage of vestibular nerve fibers from the internal acoustic foramen into the vestibule....
Madelung disease, also known as Madelung-Launois-Bensaude syndrome or neck lipomatosis or multiple symmetric lipomatosis, is a rare benign entity clinically characterized by the presence of multiple and symmetric, non-encapsulated masses of fatty tissue, usually involving the neck and the upper ...
Mainzer-Saldino syndrome (also known as conorenal syndrome (CRS)) is a rare condition and is one of the ciliopathies. It is due to mutations in the IFT140 gene, whose protein product is one of the six parts of the intraflagellar transport complex A.
The syndrome's key characteristics are:
Major salivary gland cancer staging refers to TNM staging of malignant tumors of the major salivary glands (parotid, submandibular, and sublingual glands). In contrast, tumors arising from minor salivary glands are staged according to their site of origin. The following article reflects the 8th ...
The major salivary glands are the largest and most important of the salivary glands and comprise:
paired parotid glands
paired submandibular glands
paired sublingual glands
salivary gland tumors
Malignant mixed tumors of salivary glands, according to the WHO classification, comprise three tumors:
carcinoma ex pleomorphic adenoma
arises from pre-existing pleomorphic adenoma
carcinosarcoma (true mixed tumor of the salivary glands)
true malignant mixed tumor
99% also aris...
The malleus (plural: mallei) is the most lateral middle ear ossicle, located between the tympanic membrane and the incus.
The malleus has a head, neck, and three distinct processes (manubrium (handle), anterior and lateral processes).
The head is oval in shape, and articulates p...
The mandible is the single midline bone of the lower jaw. It consists of a curved, horizontal portion, the body, and two perpendicular portions, the rami, which unite with the ends of the body nearly at right angles (angle of the jaw). It articulates with both temporal bones at the mandibular fo...
The mandibular canal, also known as the inferior alveolar canal (IAC), is located within the internal aspect of the mandible and contains the inferior alveolar nerve, artery and the vein. It starts at the mandibular foramen, on the lingual side of the ramus, continues on buccal surface of body o...
The mandibular foramen or inferior alveolar foramen is located on the medial surface of the ramus of the mandible and is the entrance to the mandibular canal. It transmits the inferior alveolar nerve, a branch of the posterior division of the mandibular division of the trigeminal nerve that supp...
The mandibular fossa or glenoid fossa is the smooth concave articular surface formed by both the squamous and petrous parts of the temporal bone. It forms the superior articular part of the temporomandibular joint and lodges the condyle of mandible.
Mandibular fractures are relatively common especially among young men. Although traditionally the mandible and base of skull are thought to form a complete bony ring, interrupted only by the TMJs. This should mean that the mandible should fracture in two places (akin to the bony pelvis) making s...
Mandibular lesions are myriad and common. The presence of teeth results in lesions that are specific to the mandible (and maxilla) and a useful classification that defines them as odontogenic or non-odontogenic. While it may often not be possible to make a diagnosis on imaging alone, this classi...
Mandibular osteoradionecrosis (ORN) is more common after radiation therapy for head and neck malignancies due to the superficial position of the mandible, which exposes it to high radiation. The maxilla can also be involved, but this is less frequent.
Mandibular ORN may occur in ...
There are many causes for mandibular periostitis:
Langerhans cell histiocytosis
malignancy (both primary and metastatic)
necrosis, e.g. radiation osteonecrosis
Garre's sclerosing osteomyelitis
Mandibular tori, analogous to maxillary tori, are common benign outgrowths of bone from the inner surface of the mandible and are usually bilateral.
They are usually asymptomatic but may cause issues with eating and drinking.
They are composed of compact bone,...
Marine-Lenhart syndrome refers to a variant of Graves disease where there are coexistent autonomous thyroid nodules. It is better described as Graves disease with coexistent multinodular goiter or nodular Graves disease 1.
The syndrome is rare with reported prevalence somewhere b...
Marjolin ulcers reflect malignant degeneration within pre-existing scars or areas of chronic inflammation such as burns, venous ulcers etc.
The Markowitz and Manson classification system categorizes fractures of the naso-orbitoethmoid (NOE) complex as follows 1:
type I - in which the medial canthal tendon is intact and connected to a single large fracture fragment
type II - the fracture is comminuted, and the medial canthal tendon...
The Martini glass sign describes the appearance of the globe in persistent hyperplastic primary vitreous (PHPV).
On MRI the retrolenticular tissue characteristic of this condition has a triangular shape, like that of a martini glass appearing as low T2 signal against the normal high T2 signal o...
The masseteric artery is a small branch from the second part of the maxillary artery. It passes laterally through the mandibular notch to the deep surface of the masseter muscle. It supplies the muscle, and anastomoses with the masseteric branches of the external maxillary and with the transvers...
The masseteric nerve or nerve to masseter is a motor branch of the anterior division of the mandibular division of the trigeminal nerve.
The masseteric nerve divides off the anterior division and continues lateral to the lateral pterygoid muscle and then medially through the mand...
The masseter muscle is one of the muscles of mastication. It is rectangular shaped and consists of three layers of fibers, where the superficial layer is the largest.
origin: zygomatic arch
insertion: ramus and angle of mandible
innervation: masseteric nerve from the anterior divisio...
The masticator space is one of the deep compartments of the head and neck.
The masticator space are paired suprahyoid cervical spaces on each side of the face. Each space is enveloped by the superficial (investing) layer of the deep cervical fascia. The superficial layer of deep...