Articles

Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.

2,246 results found
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Anterior pituitary

The anterior pituitary (or adenohypophysis) is by far the largest part of the pituitary gland, and is responsible for synthesis and release of most pituitary hormones (with the exception of oxytocin and antidiuretic hormone (ADH) which are released by the posterior pituitary). It consists of 3 ...
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Anterior ramus of the lateral sulcus

The anterior ramus of the lateral sulcus, is located at the very anterior end of the lateral sulcus (sylvian fissure), just anterior to the ascending ramus, and passes superiorly into the inferior frontal gyrus separating the pars orbitalis form the pars triangularis of the frontal operculum.  ...
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Anterior sacral meningocele

Anterior sacral meningocele is a congenital defect seen in the anterior aspect of the spine. It is defined as a meningeal cyst that occurs in the presacral space secondary to agenesis of a portion of the anterior sacrum. Pathology Associations In approximately 50% of cases, associated malform...
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Anterior spinal artery

The anterior spinal artery supplies the anterior portion of the spinal cord and arises from the vertebral artery in the region of the medulla oblongata. The two vertebral arteries (one of which is usually bigger than the other) anastamose in the midline to form a single anterior spinal artery at...
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Anterior spinal commissure

The anterior spinal commissure connects the left and right sides of the spinal cord anteriorly. It is located between the posterior-most extent of the anterior median fissure anteriorly and the ventral grey matter commissure posteriorly 1.  It is composed of anterior and lateral spinothalamic t...
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Anterior spinothalamic tract

The anterior spinothalamic tract, also known as the ventral spinothalamic fasciculus, is an ascending pathway located anteriorly within the spinal cord, primarily responsible for transmitting coarse touch and pressure.  The lateral spinothalamic tract (discussed separately), in contrast, primar...
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Anterior temporal artery

The anterior temporal artery is usually a branch of the M1 segment of the middle cerebral artery (MCA) that curves out of the Sylvian fissure and runs over the temporal lobe to supply the anterior third of the superior, middle and inferior temporal gyri.  Variant anatomy The temporopolar arter...
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Anterior temporal lobe perivascular spaces

Anterior temporal lobe perivascular spaces are recently recognised special variants of tumefactive perivascular spaces, which can mimic cystic tumours with surrounding oedema. Epidemiology A predilection for women has been reported 1. Age range is wide, from 24 to 86 years old reported 1. Cli...
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Anti-GQ1b IgG antibody syndrome

Anti-GQ1b IgG antibody syndrome refers to a number of conditions which share autoantibodies to the ganglioside complex GQ1b, and have overlapping clinical spectrums.  The conditions believed to represents various clinical manifestations of a common immunological disorder include 1:  acute opht...
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Anti-MOG associated encephalomyelitis

Anti-MOG associated encephalomyelitis represents a group of inflammatory demyelinating disorders united by the presence of IgG antibodies to myelin oligodendrocyte glycoprotein (MOG) that overlap with acute disseminated encephalomyelitis (ADEM), neuromyelitis optica spectrum disorder (NMOSD) and...
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Anti-N-methyl-D-aspartic acid receptor encephalitis

Anti N-methyl-D-aspartic acid (NMDA) receptor encephalitis is an autoimmune encephalitis with antibodies against the NMDA receptors. It is sometimes considered a form of autoimmune limbic encephalitis. It usually affects young patients particularly young females, in about 60% of whom ovarian ter...
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Antiphospholipid syndrome

Antiphospholipid syndrome is a systemic autoimmune disorder. It is usually defined as the clinical complex of vascular occlusion and ischaemic events occurring in patients who have circulating antiphospholipid antibodies. Clinical presentation Antiphospholipid syndrome is characterised by veno...
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Antonio Egas Moniz

Antonio Egas Moniz (1874-1955) 1 was a pioneering Portuguese neurologist that is notable in radiology history for his development of cerebral angiography in 1927. He is also known as the developer of prefrontal leucotomy (now better known as a lobotomy) ​for which he received a Nobel Prize in 1...
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Aphakia

Aphakia (less commonly aphacia) is the absence of the lens from the ocular globe.  Pathology Aetiology surgical removal of a cataract (commonest cause) trauma congenital Treatment and prognosis Surgical insertion of an intraocular lens implant, in which case the aphakic appearance is call...
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Apraxia

Apraxia is the inability to perform tasks which the patient has perviously learned and has no physical impairment which would preclude them from performing them 1.  Typically apraxia stems from damage to the parietal lobes. 
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Aprosencephaly

Aprosencephaly is an extremely rare anomaly fetal cerebral development the derivatives of the telencephalon as well as the diancephalon are absent or dysplastic, while more caudal structures are normal or mildly deformed. It falls under the aprosencephaly / atelencephaly spectrum (AAS)  See als...
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Aquaporin

Aquaporin is a family of transmembrane water channels found throughout the body of both humans and many other species, facilitating the passage of water, cations and gasses 1.  At least 13 types of aquaporin have been described, and these are variably expressed.  Aquaporin 4 Aquaporin 4 (AQP4...
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Aqueduct stenosis

Aqueductal stenosis (AS) is a the most common cause of congenital obstructive hydrocephalus, but can also be seen in adults as an acquired abnormality.  Epidemiology Congenital aqueductal stenosis has an estimated incidence is at ~1:5000 births although the reported range varies greatly (3.7:1...
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Arachnoid cyst

Arachnoid cysts are relatively common benign and asymptomatic lesions occurring in association with the central nervous system, both within the intracranial compartment (most common) as well as within the spinal canal. They are usually located within the subarachnoid space and contain CSF.  On ...
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Arachnoid cyst (fetal presentation)

A fetal arachnoid cyst is term given when an arachnoid cyst is diagnosed in utero. For a general discussion of arachnoid cysts refer to the parent article. Pathology They can be classified as being primary or secondary 2. primary (congenital) arachnoid cysts: result from a benign accumulation...
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Arachnoid granulation

Arachnoid granulations, also known as a Pacchionian granulation, are projections of the arachnoid membrane (villi) into the dural sinuses that allow CSF entrance from the subarachnoid space into the venous system. Epidemiology They increase in size and number with age and are seen in approxima...
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Arachnoid hyperplasia

Arachnoid hyperplasia refers to an extensive thickening of meninges surrounding optic glioma often seen in patients with neurofibromatosis. It appears as high signal on T2 sequences surrounding the low signal glioma and resembles perineural CSF space.  
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Arachnoiditis

Arachnoiditis is a broad term encompassing inflammation of the meninges and subarachnoid space. Terminology Arachnoiditis affecting the cauda equina may be referred to as spinal/lumbar adhesive arachnoiditis.  Clinical presentation Lumbar spine arachnoiditis can result in leg pain, sensory c...
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Arachnoid mater

The arachnoid mater forms the middle layer of the meninges and together with the pia mater is sometimes referred to as the leptomeninges.  Gross anatomy The arachnoid mater is a membrane that comes into direct contact with the dura mater and is separated from the pia mater by a CSF-filled spac...
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Area postrema

The area postrema is one of the so-called circumventricular organs located on the dorsal inferior surface of the medulla oblongata at the caudal end of the fourth ventricle. The specialised ependymal cells in the area postrema detect toxins in the blood and act as a vomit-inducing centre, along...
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Argyll Robertson pupil

Argyll Robertson pupil is usually bilateral and presents as bilaterally miotic and irregular pupils, which constrict briskly with accommodation but do not react to bright light therefore displaying light-near dissociation 1.  It is a highly specific sign of late neurosyphilis, however can also ...
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Arnold's nerve

Arnold's nerve is the auricular branch, also known as the mastoid branch, of the vagus nerve (CN X). Origin and course Arnold's nerve originates from the superior ganglion of the vagus nerve and also has a small contribution from the inferior ganglion of the glossopharyngeal nerve. It ascends ...
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Arterial spin labelling MR perfusion

Arterial spin labelling (ASL) MR perfusion is an MR perfusion technique which does not require intravenous administration of contrast (unlike DSC perfusion and DCE perfusion). Instead it exploits the ability of MRI to magnetically label arterial blood below the imaging slab. The parameter most c...
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Arterial supply of the head and neck

The arteries of the head and neck are branches of the common carotid and subclavian arteries. common carotid artery carotid body carotid bifurcation internal carotid artery (segments) caroticotympanic artery persistent stapedial artery ophthalmic artery supraorbital artery lacrimal arte...
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Artery of Adamkiewicz

The artery of Adamkiewicz, also known as the great anterior radiculomedullary artery or arteria radicularis anterior magna, is the name given to the dominant thoracolumbar segmental artery that supplies the spinal cord. Gross anatomy Origin The artery of Adamkiewicz has a variable origin but ...
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Artery of Percheron

The artery of Percheron is a rare variant of the posterior cerebral circulation characterised by a solitary arterial trunk that supplies blood to the paramedian thalami and the rostral midbrain bilaterally. Gross anatomy The term is used to refer to a solitary arterial trunk that branches from...
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Artery of Percheron territory infarct

Artery of Percheron territory infarct is rare, on account of the relative rarity of the artery of Percheron, and presents with a variety of signs and symptoms collectively termed the paramedian thalamic syndrome. It is a type of posterior circulation infarction. On imaging, it is classically ch...
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Ascending ramus of the lateral sulcus

Ascending ramus of the lateral sulcus, is located at the anterior end of the lateral sulcus (sylvian fissure), just posterior to the anterior ramus, and passes superiorly into the inferior frontal gyrus separating the pars triangularis from the pars opercularis of the frontal operculum.  Termin...
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Ascending transtentorial herniation

Ascending transtentorial herniation is a situation where space-occupying lesions in the posterior cranial fossa cause superior displacement of superior parts of the cerebellum through the tentorial notch.  Clinical presentation nausea and/or vomiting  rapid progression toward a decreased leve...
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ASIA impairment scale for spinal injury

The American Spinal Injury Association (ASIA) was developed by the American Spinal Injury Association in 2006, and at the time of writing (July 2016), remains the most widely used scale. This scale is part of the ASIA spinal cord injury classification. It divides spinal cord injuries into 5 cat...
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Astroblastoma

Astroblastomas are rare glial tumours usually found in the cerebral hemispheres of young adults and children.  Epidemiology They occur at all ages range from early childhood to 6th decade but are most commonly seen in children, adolescents, and young adults with a mean age between 10-30 years ...
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Astrocytes

Astrocytes are cells of the central nervous system which act as both physical and physiological support for the neurones that are embedded between them. They are particularly abundant in the grey matter, where they are the most abundant glial cells 1. They are highly branched and contribute to ...
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Astrocytic tumours

Astrocytic tumours are primary central nervous system tumours that either arises from astrocytes or appear similar to astrocytes on histology having arisen from precursor cells. They are the most common tumours arising from glial cells. They can be divided into those that are diffuse in growth ...
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Asymmetrically large jugular bulb

Asymmetrically large jugular bulbs are entirely normal and asymptomatic; its only significance is to distinguish it from pathology. The size of the jugular bulbs is variable, with the right side being significantly larger than the left in two-thirds of people. A normal but large bulb will have...
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Asymmetric fatty bone marrow of the petrous apex

Asymmetric pneumatisation of petrous apex results in asymmetric fatty bone marrow within the petrous apex. It is a common incidental finding on brain and skull base MRI. Clinical presentation Asymptomatic. Pathology Asymmetric pneumatisation of the petrous apex results in the presence of bon...
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Asymmetric ventriculomegaly, interhemispheric cyst and dysgenesis of the corpus callosum (AVID)

Asymmetric ventriculomegaly, interhemispheric cyst and dysgenesis of the corpus callosum (AVID) is a triad of congenital cerebral anomalies. Radiographic features markedly asymmetric enlargement of the lateral ventricles may be the initial finding on routine fetal morphology ultrasound. inter...
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Asymmetry of the lateral ventricles

The lateral ventricles occasionally show small side to side differences in size on CT or MRI of the brain. This asymmetry of the lateral ventricles (ALV) is a normal anatomic variant in most cases. Epidemiology The prevalence of asymmetry in lateral ventricle size in those without evidence of ...
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Ataxia telangiectasia

Ataxia telangiectasia is a rare multisystem disorder which carries an autosomal recessive inheritance, sometimes classified as a phakomatosis. It is characterised by multiple telangiectasias, cerebellar ataxia, pulmonary infections and immunodeficiency.  On brain imaging, it usually demonstrate...
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Atelencephaly

Atelencephaly (also termed atelencephalic microcephaly) is a rare and extreme disorder with only a handful of published cases. In this anomaly, the derivatives of the telencephalon are absent or dysplastic, while more caudal structures are normal or mildly deformed. It falls under the aprosencep...
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Atlantodental interval

The atlantodental interval (ADI), as the name suggests, is the horizontal distance between the anterior arch of the atlas and the dens of the axis, used in the diagnosis of atlanto-occipital dissociation injuries and injuries of the atlas and axis. It is the distance (in mm) between the posteri...
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Atretic parietal cephalocele

Atretic parietal cephaloceles (APC), also known as atretic cephaloceles, are small subscalp lesions that consist of dura, fibrous tissue, and dysplastic brain tissue. Epidemiology Common presentation in infants and young children.  Clinical presentation Palpable midline parietal soft tissue ...
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Atypical callosal dysgenesis

Atypical callosal dysgenesis is a term used to denote an unusual pattern of dysgenesis of the corpus callosum. The development of the corpus callosum occurs between the 12th and 16-20th weeks of gestation 2-3. It begins with the genu and then continues posteriorly along the body to the splenium...
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Atypical choroid plexus papilloma

Atypical choroid plexus papillomas are WHO grade II tumours derived from choroid plexus epithelium with intermediate clinical and pathological features between the much more common, and more indolent, WHO grade I choroid plexus papilloma and the more aggressive WHO III choroid plexus carcinoma. ...
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Atypical meningioma

Atypical meningioma refers to a more aggressive form of meningioma and denotes a WHO grade II tumour (along with two histological variants, clear cell meningioma and chordoid meningioma). Atypical meningiomas account for 20-30% of all meningiomas 1,3.  It should be noted that epidemiology, clin...
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Atypical teratoid/rhabdoid tumour

Atypical teratoid/rhabdoid tumours (AT/RT) are an uncommon WHO Grade IV tumour, which in the vast majority of cases occurs in young children less than two years of age. It most frequently presents as a posterior fossa mass. AT/RT often resembles medulloblastoma by imaging and even H&E microscopy...
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Autoimmune encephalitis

Autoimmune encephalitis, also known as autoimmune limbic encephalitis, is an antibody-mediated brain inflammatory process, typically involving the limbic system, although all parts of the brain can be involved.  Autoimmune encephalitis can be divided broadly into two groups, based on whether or...
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Autophony

Autophony (or tympanophony) is the experience of finding that one's own voice sounds much louder than normal or is unpleasantly garbled.  Autophony has been described in several clinical entities including superior semicircular canal dehiscence syndrome and patulous Eustachian tube dysfunction....
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Autosomal recessive spastic ataxia of Charlevoix-Saguenay

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a rare autosomal recessive spastic ataxia unique to the region of Charlevoix-Saguenay, in the Province of Quebec, Canada. It is due to a mutation on the SACS gene locus q12 of chromosome 13. It has been reported in other regio...
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AVAglio criteria for glioblastoma

The AVAglio criteria were developed to assess response to first-line treatment of glioblastoma, treated with radiotherapy and temozolomide with or without bevacizumab 1-2. These were adapted from the older Macdonald criteria, but have since been superseded by they RANO criteria (2010) 1.  The A...
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Azygos anterior cerebral artery

An azygos anterior cerebral artery is uncommon to rare variant of the circle of Willis where the two A1 segments of the anterior cerebral artery (ACA) join to form a single trunk. As a result, there is no anterior communicating artery. This organisation is similar to that seen in lower primates ...
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Babinski-Nageotte syndrome

Babinski-Nageotte syndrome is thought to be a brainstem stroke syndrome in between that of the hemimedullary syndrome (Reinhold syndrome) and the lateral medullary syndrome (Wallenberg syndrome) 1,2.  Terminology In many texts this eponymous syndrome is incorrectly attributed to actually being...
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Balint syndrome

The Balint syndrome is characterised by: simultanagnosia (inability to perceive more than one object at a time) optic ataxia oculomotor apraxia It typically results from damage to the parieto-occipital regions, and has been associated with 1-3: corticobasal degeneration posterior cortical ...
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Balo concentric sclerosis

Balo concentric sclerosis is a rare and severe monophasic demyelinating disease, considered a subtype of multiple sclerosis, appearing as a rounded lesion with alternating layers of hyper and hypoattenuation giving it a characteristic 'bullseye' or 'onion bulb' appearance 1,9. Epidemiology It ...
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Band heterotopia

Band heterotopia, also known as double cortex syndrome, is a form of diffuse grey matter heterotopia affecting almost only women. Refractory epilepsy is present in nearly all affected patients, with partial complex and atypical absence epilepsy being the most common syndromes. On imaging, this ...
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Band of Giacomini

The band of Giacomini, also known as the tail of the dentate gyrus is the anteromedial continuation of the dentate gyrus, which in turn is part of the hippocampal formation, along with the hippocampus, subicular complex and entorhinal cortex. It is an important anatomical landmark of the inferio...
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Bannayan–Riley–Ruvalcaba syndrome

Bannayan–Riley–Ruvalcaba syndrome (BRRS or BRR syndrome) is a very rare autosomal dominant hamartomatous disorder caused by a mutation in the PTEN gene. It is considered in the family of hamartomatous polyposis syndrome. There are no formal diagnostic criteria for this disease, but characterist...
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Bannayan-Zonana syndrome

Bannayan-Zonana syndrome is a rare hamartomatous disorder.  Epidemiology Inheritance is by autosomal dominant transmission with few reported sporadic cases. Male predominance is reported. 1 Presentation Bannayan-Zonana syndrome characterised by  : macrocephaly  multiple lipomas haemangiom...
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Bardet-Biedl syndrome

Bardet-Biedl syndrome (BBS), previously known as the Laurence-Moon-Bardet-Biedl syndrome (LMBBS), is a rare autosomal recessive hereditary condition. Clinical presentation The clinical spectrum includes: retinal anomalies: similar to that of retinitis pigmentosa mental retardation renal str...
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Bare orbit sign (sphenoid wing)

The bare orbit sign, is described as a characteristic appearance of the orbit, seen when the innominate line is absent. The innominate line is a projection of the greater wing of the sphenoid, and its absence or destruction is responsible for this appearance. It is the classical frontal radiogr...
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Barkovich classification of focal cortical dysplasia

Barkovich classifies focal cortical dysplasias among the his extensive classification system for malformations of cortical development, distributing them as follows: Type I and type IIb (transcortical dysplasia - Taylor type with balloon cells) as non-neoplastic malformations due to abnormal ne...
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Barrow classification of caroticocavernous fistulae

Barrow caroticocavernous fistula classification divides caroticocavernous fistulas into direct (type A) or indirect (types B-D). This classification was proposed by Barrow et al. in 1985 1 and at the time of writing (mid 2016) remains the most widely used system for describing caroticocavernous ...
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Basal ganglia

The basal ganglia are a group of grey matter nuclei in the deep aspects of the brain that is interconnected with the cerebral cortex, thalami and brainstem. In a strict anatomical sense, it contains three paired nuclei that together comprise the corpus striatum: caudate nucleus putamen globu...
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Basal ganglia and thalamus signal abnormalities

Basal ganglia and thalamus signal abnormalities occur in a wide variety of conditions. Ischaemia/hypoxia, metabolic disorders and toxins, particularly those that affect the respiratory chain, have a predilection for affecting the basal ganglia as they are highly metabolically active.  They can ...
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Basal ganglia calcification

Basal ganglia calcification is common and is seen in approximately 1% of all CT scans of the brain, depending on the demographics of the scanned population. It is seen more frequently in older patients and is considered a normal incidental and idiopathic finding in an elderly patient but should ...
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Basal ganglia haemorrhage

Basal ganglia haemorrhage is a common form of intracerebral haemorrhage, and usually as a result of poorly controlled long-standing hypertension. The stigmata of chronic hypertensive encephalopathy are often present (see cerebral microhaemorrhages). Other sites of hypertensive haemorrhages are ...
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Basal ganglia T1 hyperintensity

There are many causes of basal ganglia T1 hyperintensity, but the majority relate to deposition of T1-intense elements within the basal ganglia such as: calcium idiopathic calcification calcium and phosphate abnormalities hepatic failure acquired non-wilsonian hepatocerebral degeneration W...
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Basal ganglia T1 hypointensity

Hypointensity on T1 weighted images of the basal ganglia, as a general rule is in itself of limited value, and should be correlated with T2 signal, which is usually more informative. Most causes of T2 hyperintensity in the basal ganglia will result in T1 hypointensity (most are afterall due to o...
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Basal ganglia T2 hyperintensity

The causes of basal ganglia T2 hyperintensity can be remembered using the mnemonic LINT: lymphoma ischaemia hypoxia venous infarction (internal cerebral vein thrombosis) neurodegenerative / metabolic autoimmune encephalitis (e.g. anti-D2 dopamine antibody encephalitis) Creutzfeldt-Jakob d...
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Basal ganglia T2 hypointensity

Basal ganglia T2 hypointensities can be caused by any of the following and is commonly remembered using the mnemonic ChOMP. childhood hypoxia old age multiple sclerosis Parkinson disease: more in globus pallidus Parkinson-plus syndrome: more in putamen deoxyhemoglobin of hemorrhage haemos...
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Basal nucleus of Meynert

The basal nucleus of Meynert, also known as the nucleus basalis of Meynert, is formed by a group of cells that lies in the substantia innominata. It is rich in acetylcholine and its degeneration has been correlated to Alzheimer disease. It lies anterior to the anterior commissure. 
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Basal vein of Rosenthal

The basal veins, also known as the veins of Rosenthal, are paired, paramedian veins which originate on the medial surface of the temporal lobe and run posteriorly and medially. It passes lateral to the midbrain through the ambient cistern to drain into the vein of Galen with the internal cerebra...
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Base of skull fracture

Basilar fractures of the skull, also known as base of skull fractures, are a common form of skull fracture, particularly in the setting of severe traumatic head injury, and involve the base of the skull. They may occur in isolation or often in continuity with skull vault fractures or facial frac...
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Base of the skull

The base of the skull (or skull base) forms the floor of the cranial cavity and separates the brain from the structures of the neck and face. Gross anatomy The base of the skull is a bony diaphragm composed of a number of bones - from anterior to posterior: frontal bone ethmoid bone sphenoi...
Article

Basilar artery

The basilar artery is part of the posterior cerebral circulation. It artery arises from the confluence of the left and right vertebral arteries at the base of the pons as they rise towards the base of the brain. Summary origin: vertebral artery confluence course: ventral to pons in the pontin...
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Basilar artery aneurysm

Basilar artery aneurysms are less common than anterior circulation aneurysms, and rupture less frequently, but their critical location necessitates careful evaluation. Radiographic features CT may present as a lobulated hyperattenuating structure anterior to the mid brain rupture of a basil...
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Basilar artery fenestration

Basilar artery fenestration (or more simply, basilar fenestration) is the most common intracranial arterial fenestration. It refers to duplication of a portion of the artery, thought to occur due to failed fusion of plexiform primitive longitudinal neural arteries 4. Its reported prevalence is h...
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Basilar artery hypoplasia

Basilar artery hypoplasia is a rare vascular anomaly of the basilar artery. Pathology Associations Basilar artery hypoplasia is usually accompanied by one or more fo the following: persistent carotid-vertebrobasilar anastomoses hypoplastic V4 segments of the vertebral arteries unilateral o...
Article

Basilar invagination

Basilar invagination, also called basilar impression, is a congenital or acquired craniocervical junction abnormality where the tip of the odontoid process projects above the foramen magnum.  Terminology The terms basilar invagination and basilar impression are often used interchangeably becau...
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Basilar invagination (mnemonic)

A mnemonic to help recall the causes of basilar invagination is: PF ROACH Mnemonic P: Paget disease of bone F: fibrous dysplasia R: rheumatoid arthritis, rickets O: osteogenesis imperfecta, osteomalacia A: achondroplasia C: Chiari I and Chiari II, cleidocranial dysostosis H: hyperparath...
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Basilar venous plexus

The basilar venous plexus lies between the endosteal and visceral layers of the dura on the inner surface of the clivus. It connects the: inferior petrosal sinuses cavernous sinuses intercavernous sinuses superior petrosal sinuses internal vertebral venous plexus marginal sinus (around the...
Article

Basion

The basion is the median (midline) point of the anterior margin of the foramen magnum. The apical ligament attaches to it. It is one of the skull landmarks, craniometric points for radiological or anthropological skull measurement. Clinical importance Various lines and measurements using the ...
Article

Basion-axial interval

The basion-axial interval (BAI), as the name suggests, is the horizontal distance between the basion and the posterior cortex of the axis, used in the diagnosis of atlanto-occipital dissociation injuries. It is the distance (in mm) between the basion and the superior extension of the posterior ...
Article

Basion-dens interval

The basion-dens interval (BDI), as the name suggests, is the distance between the basion and the tip of the dens, used in the diagnosis of atlanto-occipital dissociation injuries. It is the distance from the most inferior portion of the basion to the closest point of the superior aspect of the ...
Article

Battle sign (base of skull fracture)

Battle sign is an eponymous term given to mastoid ecchymosis (bruising of the scalp overlying the mastoid process) and is strongly suggestive of a base of skull fracture, most commonly a petrous temporal bone fracture.  History and etymology Mr William Henry Battle (1855-1936) was an English s...
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Bat wing 4th ventricle

Bat wing 4th ventricle sign refers to the morphology of the fourth ventricle in the Joubert anomaly and related syndromes. The absence of a vermis with apposed cerebellar hemispheres give the fourth ventricle an appearance reminiscent of a bat with its wings outstretched. It is best demonstrate...
Article

Behavioural variant frontotemporal lobar degeneration

Behavioural variant frontotemporal lobar degeneration (bvFTLD), also known as behavioural variant frontotemporal dementia, is one of the clinical neurodegenerative diseases associated with frontotemporal lobar degeneration (FTLD).  In the older literature, it is also referred to as Pick disease...
Article

Behçet disease

Behçet disease is a multisystemic and chronic inflammatory vasculitis of unknown aetiology. Epidemiology The mean age at which Behçet disease occurs is 20-30 years. The disease is most prevalent in the Mediterranean region, Middle East and East Asia. The highest incidence has been reported in ...
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Behçet disease (CNS manifestations)

CNS manifestations of Behçet disease, also known as neuro-Behçet disease, corresponds to the neurological involvement of the systemic vasculitis Behçet disease and has a variety of manifestations.  For a discussion of the disease in general please refer to Behçet disease article.  Epidemiology...

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