The L sign is one of the features useful in identifying the central sulcus on cross-sectional imaging.
It relies on identifying the superior frontal sulcus which intersects the precentral sulcus in an "L" junction, thus defining the precentral gyrus. The central sulcus is the next posterior sul...
L-2-hydroxyglutaric aciduria is a rare organic aciduria but has characteristic MRI findings especially in the early stages 1. This can allow for early diagnosis, often prior to biochemical investigations.
As it is inherited in an autosomal recessive fashion, consanguineous marriag...
Labrune syndrome (LS) is a rare condition that consists of a triad of leukoencephalopathy, cerebral calcifications and cysts.
LS is an extremely rare condition, with no more than 10 cases reported in literature 2. The onset occurs from early infancy to adolescence; few cases have...
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 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 is inflammation of the membranous labyrinth.
Labyrinthitis can be divided according to aetiology.
Labyrinthitis is a potential complication of acute otomastoiditis with spread of infection or of toxins from the middle ear to the inner ear via either the r...
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 lacrimal apparatus consists of the lacrimal gland and the nasolacrimal drainage apparatus.
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 and is responsible for tear production.
The lacrimal gland is roughly almond sized, lies in the extraconal part of the orbit, and extends deep into the orbital septum. Its structure is similar to the salivary gland...
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 lateral to the te...
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 orbit between the posterior and anterior lacrimal crests. The lac...
The lacrimal sac fossa is an excavated fossa in inferior aspect of anteromedial orbital wall which contains lacrimal sac. It is bounded by anterior and posterior lacrimal crests of maxilla and lacrimal bones, respectively. In adults, it measures approximately 8-9mm anteroposteriorly and 10-17mm ...
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...
Lactate is one of the more important compounds assessed on MR spectroscopy, and resonates at 1.3 ppm chemical shift, with a characteristic double peak at long TEs. It is however superimposed on the lipid band, and using an intermediate TE (e.g. 144ms) will invert only lactate allowing it to be d...
Lactating adenomas are a benign breast tumour that typically occur in the peri-partum period, and are one of the most prevalent breast lesions during puerperium 4.
Lactating adenomas commonly present as painless breast masses late in pregnancy or in the postpartum period....
Lacuna magna (a.k.a. sinus of Guérin) is a congenital blind-ended pouch located dorsal to navicular fossa of penis separated by fold and both share an external common opening to external urethral meatus. This diverticulum is located above and parallel to urethra.
Although it may ...
Lacunar infarcts are small (<20 mm) infarcts in the distal distribution of deep penetrating vessels (lenticulostriate, thalamoperforating, and pontine perforating arteries, recurrent artery of Heubner). They result from occlusion of one of the small penetrating end arteries at the base of the br...
Lacunar stroke syndrome (LACS) is a description of the clinical syndrome that results from a lacunar infarct.
Each of the five classical lacunar syndromes has a relatively distinct symptom complex. Symptoms may occur suddenly, progressively, or in a fluctuating manner (e.g. the capsular warnin...
Ladd bands or Ladd´s bands are the most commonly encountered form of peritoneal bands in disarrangement of intestines, e.g. intestinal malrotation.
Classically they extend from the abnormally positioned caecum to peritoneum and liver, crossing the duodenum in their course. Extension,...
Lady Windermere syndrome refers to a pattern of pulmonary Mycobacterium avium complex (MAC) infection seen typically in elderly white women who chronically suppress the normal cough reflex. A fastidious nature and a reticence to expectorate are believed to predispose such persons to infections w...
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 ...
There are a number of lambda signs:
lambda sign of twin pregnancy
lambda sign of sarcoidosis
The lambda sign is seen on gallium-67 scans in the setting of thoracic sarcoidosis. Bilateral hilar and right paratracheal lymph nodes are typically involved which can resemble the lambda symbol (λ).
lambda sign of twin pregnancy
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.
Lambert-Eaton myasthenia syndrome (LEMS) is rare but is still the second most common neuromuscular junction disease after myasthenia gravis. Two-thirds of LEMS present as a paraneoplastic syndrome secondary to malignancy, most commonly lung cancer but is also associated with breast, ovarian and ...
The lamina terminalis forms the anterior wall of the third ventricle.
It is a thin membrane which stretches between the anterior commissure, the fornix and the rostrum of the corpus callosum. The dorsal surface of the optic chiasm is at the base of the lamina terminalis 1.
Laminar heterotopia is a form of diffuse grey matter heterotopia, resulting in heterotopic grey matter, deep to the cortex, within the centrum semiovale 2.
There appears to be some disagreement or confusion in regards to whether or not laminar heterotopia is synonymous with band heterotopia wit...
Lane-Hamilton syndrome (LHS) refers to the rare concurrent association of idiopathic pulmonary haemosiderosis and coeliac disease 1.
It is typically seen in children under the age of 15 but can occasionally be seen in adults.
History and etymology
It was originally described by ...
Langer-Giedion syndrome (LGS), also known as trichorhinophanageal syndrome type II, is an extremely rare autosomal dominant genetic disorder.
The effects are seen mainly on the skeletal system and primarily involves
digits of the hands and feet: phalangeal...
The Langer Saldino syndrome or achondrogenesis type II is a sub type of achondrogenesis. It is an extremely rare fatal skeletal dysplasia.
Majority of cases are sporadic. Autosomal dominant inheritance is also another mode. There is mutation in the collagen type II gene (CO...
Langerhans cells are dendritic cells of monocyte-macrophage lineage, containing large granules called Birbeck granules. They are normally found in epithelial surfaces, lymph nodes and other organs, and can also be found elsewhere, particularly in association with Langerhans cell histiocytosis.
Langerhans cell histiocytosis (LCH) is a rare multi-system disease with a wide and heterogeneous clinical spectrum and variable extent of involvement.
The disease is more common in the paediatric population, with a peak incidence between one and three years of age 5. Incidence is...
The skeleton is the most commonly involved organ system in Langerhans cell histiocytosis (LCH) and is by far the most common location for single-lesion LCH, often referred to as eosinophilic granuloma (EG) (the terms are used interchangeably in this article). For a general discusion of this dise...
LaPlace's law is useful in thinking about dilated tubular structures, such as the bowel or vessels (e.g. aortic aneurysms). The relationship between wall tension and radius shows why more dilated regions of a tube develop more wall stress and therefore are at higher risk for perforation:
Large bowel (colorectal) lymphoma is a very rare tumour, accounting for < 0.5% of primary colorectal malignancies, ~1.5% of all lymphomas, and ~15% of gastrointestinal lymphoma. Large bowel lymphoma differs from gastric and small bowel lymphoma in clinical presentation, management and prognosis....
Large bowel obstruction (LBO) are often impressive on imaging, on account of the ability of the large bowel to massively distend. This condition requires prompt diagnosis and treatment.
Large bowel obstructions are far less common than small bowel obstructions, accounting for onl...
Large bowel obstruction (LBO) occurs when there is mechanical obstruction of the large bowel and is often impressive on imaging on account of the ability of the large bowel to massively distend. This condition requires prompt diagnosis and treatment.
This is a summary articl...
Large cell carcinoma of the lung is one of the histological types of non-small cell carcinomas of the lung.
It is thought to account for approximately 10% of bronchogenic carcinoma 1.
Patient presents with dyspnea, chronic cough and haemoptysis.
Large cell neuroendocrine carcinoma (LCNEC) of the lung is classified as a subtype of large cell carcinoma of the lung. It is also classified as a pulmonary neuroendocrine tumour.
The incidence peaks around the 6th decade 6. There is an increased male predilection 7.
A large for date uterus is a clinical observation based on uterine fundal height, which may result in referral for ultrasound assessment, usually in mid to late pregnancy.
Causes include :
constitutionally large fetus
The large intestine (or large bowel) is a 1.5 metre muscular tube that extends from the caecum to the rectum. It has three outer longitudinal muscular layers called taenia coli, which are about 30 cm shorter than the length of the large bowel causing characteristic sacculations interrupted by in...
Large joint dislocation is a not uncommon presentation to emergency rooms. Described in order of comonality:
posterior dislocation of the hip
Large loop excision of the transformation zone (LLETZ) is a gynaecological procedure. It is currently one of the most commonly used approaches to treat high grade cervical dysplasia - cervical intraepithelial neoplasia.
Large rod like calcifications are benign calcifications seen within ectatic ducts.
plasma cell mastitis
>1 mm in diameter
may have lucent centres (if calcium is only in walls of ducts)
branching pattern may be seen
radiation towards the nipple...
When a pleural effusion is large and unilateral, concern for an underlying abnormality should be raised. Causes include:
extension from sub-diaphragmatic primary infection
The term large vessel vasculitis (LVV) usually denotes the spectrum of primary vasculitides that causes chronic granulomatous inflammation predominantly involving the aorta and its major branches.
The two major entities in this group are
giant cell arteritis (GCA) - affects older individuals ...
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...
A large yolk sac is one measuring >5-6 mm in pregnancies between a gestational age of 5-10 weeks. One study had shown that a yolk sac diameter of >5 mm can be associated with an increased risk of spontaneous miscarriage although few other authors have mentioned the existence of a very large yolk...
The Larmor frequency and equation are named after the Irish Physicist and Mathematician Joseph Larmor (1857-1942).
Protons and neutrons pair up in nuclei causing the cancellation of their individual angular momentum. All nuclei also have a spin; those with an odd number of protons and/or neutro...
Larsen syndrome (LS) is an extremely rare disorder, often classified as a type of osteochondrodysplasia.
The estimated incidence is thought to be at ~ 1 in 100,000 people. There may be an increased female predilection.
It is characterised by many features i...
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 larynx, but are more frequent on supraglottic locations, such as epiglottis and vallecula. The prevalence of each location varies on different studies.
The laryngeal cysts represent a rare group, about 5%, of benign laryngeal lesions 1. Th...
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, larygneal 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 Lasjaunias classification, at the time of writing (mid 2016), is one of the two commonly used systems for classifying vein of Galen malformations. It relies on dividing the entity into choroidal or mural types, depending on the number and origin of feeding arteries.
The Latarjet procedure is an orthopaedic procedure in the shoulder where a coracoid bone block is positioned flush with the anterior-inferior border of the glenoid (often with one or more screws). It can be performed either and an open or arthroscopic procedure. It is usually perfomed for antero...
A late mediolateral projection is an additional view that can be used whenever,in the presence of rounded calcifications of probable intracystic nature, the standard ML view does not allow the recognition of the characteristic tea cups appearance due to the density of milk of calcium.
A second ...
The lateral (radial) collateral ligament (LCL/RCL) complex is a major lateral stabiliser of the elbow joint and resists varus stress.
The LCL is a Y-shaped ligamentous complex composed of three parts 1, 2:
from sigmoid notch to supinator crest of the ulna bone
The lateral apertures (of Luschka) are two of the foramina in the ventricular system and link the fourth ventricle to the cerebellopontine cistern. Together with the median aperture (of Magendie) they comprise two of the three ways that CSF can leave the fourth ventricle and enter the subarachno...
The appearance of a Segond fracture on conventional radiographs as an elliptic fragment of bone parallel to the tibia, just distal to the lateral tibial plateau.
The lateral circumflex femoral artery (LCFA) is a branch of the profunda femoris that arises soon after the medial circumflex femoral artery. While the medial circumflex runs posteriorly around the femoral neck, the lateral circumflex courses laterally from its origin and anterior to the femoral...
The lateral collateral ligament (complex) of the ankle is a set of three ligaments that resist inversion of the ankle joint. They are more commonly injured than the medial collateral (deltoid) ligament of the ankle. They run from the lateral malleolus of the fibula to the talus and calcaneus.
The lateral (fibular) collateral ligament is a cord-like ligament on the lateral aspect of the knee and forms part of the posterolateral corner.
It originates from the lateral femoral epicondyle and has an oblique course, is joined by the biceps femoris tendon forming the conjoi...
The lateral compartment of the leg, also know as the peroneal compartment, is one of the four compartments in the leg between the knee and foot. Muscles within this compartment primarily produce ankle and foot eversion.
The leg is separated into anterior, lateral, superficial posterior and deep...
The lateral corticospinal tract is a descending neural pathway primarily concerned with motor function. There are separate lateral and anterior corticospinal tracts as fibres decussate at the cevicomedullary junction.
Corticospinal fibres arise from neurons i...
Lateral crescent sign is a useful diagnostic sign of a direct inguinal hernia on CT scan, the hernia causing compression and lateral displacement of the inguinal canal contents (ductus deferens, testicular vessels, fat, etc) to form a semicircle of tissue that resembles a moon crescent seen late...
The lateral cuneiform is one of the tarsal bones located between the intermediate cuneiform and cuboid bones.
The lateral cuneiform is a wedge shaped bone. It is smaller than the medial cuneiform and larger than the intermediate cuneiform. It lies edge downward, betwee...
Lateral epicondyle fractures are rare epicondylar fractures. They are much rarer than medial epicondyle fractures and represent avulsion of the lateral epicondyle. They are usually seen in the setting of other injuries 1-3.
Incidence typically peaks in the paediatric age group (6...
Lateral epicondylitis, also known as “tennis elbow,” is an overuse syndrome of the common extensor tendon and predominantly affects the extensor carpi radialis brevis (ECRB) tendon.
Lateral epicondylitis occurs with a frequency seven to ten times that of medial epicondylitis. As w...
The lateral femoral cutaneous nerve, also known as the lateral cutaneous nerve of the thigh, is a sensory branch of the lumbar plexus arising from the posterior divisions of the anterior rami of L2 and L3 spinal nerves. The nerve supplies the skin on the anterior and lateral aspects of the thigh...
The (deep) lateral femoral notch sign describes a depression on the lateral femoral condyle at the terminal sulcus, a junction between the weight bearing tibial articular surface and the patellar articular surface of the femoral condyle.
The likely mechanism is a hyperextension or im...
The lateral fossae are concave depressions of peritoneum in the paravesical space that lie between the lateral umbilical folds and the lateral parietal peritoneum. The lateral fossae are the smallest of the anterior paravesical fossae, and typically partially contain the cecum and/or sigmoid col...
A lateral hemivertebra is a form of hemivertebra which occurs when one of the two chondrification centre fails to develop. They can be single or multiple. and a usually associated this a resultant scoliosis.
Various subtypes have been descrbied
Lateral humeral condyle fractures are relatively common elbow fractures that predominantly occur in children. They represent ~12.5% (range 5-20%) of elbow fractures in children and are the second most common paediatric elbow fracture after supracondylar fractures.
They occur in sc...
The lateral lenticulostriate arteries arise from the proximal middle cerebral artery (MCA) and supply the lateral portion of the putamen and external capsule as well as the upper internal capsule.
They are longer (almost twice the diameter) and more numerous than the medial lenticulostriate art...
Lateral medullary syndrome, (or Wallenberg syndrome) is an acute ischemic infarct due to occlusion of the vessels supplying the lateral medulla oblongata; most commonly occlusion of intracranial portion of the vertebral artery followed by PICA and it's branches. This syndrome is characterised by...
Lateral meningocoele syndrome is a rare hereditary connective tissue disorder characterized by multiple lateral lumbar meningocoeles, distinctive facial features, joint hypermobility, hypotonia, skeletal abnormalities, congenital cardiovascular malformations, urogenital anomalies and neurologic ...
The lateral parietotemporal line is an imaginary boundary between the temporal lobe and occipital lobe and forms the posterior boundary of the former.
The line has a superior and inferior end:
superior - superolateral end of the parieto-occipital fissure
inferior - preoccipital notch
Lateral patellar dislocation refers to lateral displacement followed by dislocation of patella due to disruptive changes to the medial patellar retinaculum.
Patellar dislocation accounts for ~3% of all knee injuries and is commonly seen in those individuals who participate in spor...
The lateral pectoral nerve, also known as the lateral anterior thoracic nerve, arises from the lateral cord of the brachial plexus and supplies the pectoralis major muscle.
The lateral pectoral nerve arises from the lateral cord of the brachial plexus with fibres from the...
The lateral plantar nerve is an important motor nerve in the foot because it innervates all intrinsic muscles in the sole, except for the muscles supplied by the medial plantar nerve (abductor hallucis, flexor digitorum brevis, flexor hallucis brevis, and first lumbrical).
Lateral pontine syndrome, also known as Marie-Foix syndrome, refers to one of the brainstem stroke syndromes which occurs due to occlusion of perforating branches of the basilar and anterior inferior cerebellar (AICA) arteries. This results in infarction of the lateral aspect of the pons which p...
The lateral posterior choroidal artery may be a singular structure or exist as multiple lateral posterior choroidal arteries. In both cases, they arise from the P2 segment of the PCA, just distal (and lateral) to the medial posterior choroidal arteries. In some cases, they may arise from one of ...
The lateral posterior superior nasal nerves, also known as the short sphenopalatine nerves, are branches of the pterygopalatine ganglion.
exits the pterygopalatine ganglion in the pterygopalatine fossa
passes through the sphenopalatine foramen to enter the back of the n...
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 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 ± 0.6mm.
innervation: abducens nerve (CN VI)
The lateral sacral artery is one of three branches of the posterior division of the internal iliac artery.
origin: from the posterior division of the internal iliac artery in the pelvis
branches: superior and inferior sacral arteries
supply: sacral meninges, pirifor...