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.

2,278 results found
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14-3-3 protein

14-3-3 proteins are found in the cerebrospinal fluid (CSF), and are currently used to help identify patients with sporadic Creutzfeldt-Jakob disease (sCJD).  Seven distinct 14-3-3 proteins have been found in humans. In diagnosing sCJD, the sensitivity of 14-3-3 protein is 92% and its specifici...
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18q syndrome

18q syndrome is a rare chromosomal anomaly where there is a deletion of part of the long arm of chromosome 18. Associated symptoms and findings vary widely, as does their severity. Characteristic features include short stature, mental retardation and hypotonia, facial and distal skeletal abnorma...
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1p19q codeletion

1p19q codeletion stands for the combined loss of the short arm chromosome 1 (i.e. 1p) and the long arm of chromosome 19 (19q) and is recognised as a genetic marker predictive of therapeutic response to both chemotherapy and combined chemoradiotherapy and overall longer survival in patients with ...
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2-hydroxyglutarate

2-hydroxyglutarate is a metabolite that accumulates in the brains of patients with IDH-1 mutated (IDH-1 positive) brain tumours, particularly diffuse low-grade gliomas. Although not in widespread clinical use, it is likely that 2-hydroxyglutarate, which resonates at 2.25 ppm, will be able to be ...
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ABC/2

ABC/2 is a fast and simple method for estimating the volume of intracerebral haemorrhage (or any other ellipsoid lesion for that matter) which does not require volumetric 3D analysis or software. Intracerebral haemorrhage volume is an important predictor of morbidity and mortality (and thus tria...
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Abducens nerve

The abducens nerve is the sixth cranial nerve. It courses from its nucleus located in the dorsal pons to its innervation of the lateral rectus muscle and can be divided into four parts: nucleus and intraparenchymal portion cisternal portion cavernous sinus portion orbital portion Gross anat...
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Abducens nerve palsy

Abducens nerve palsies, or sixth nerve palsies, results in weakness of the ipsilateral lateral rectus muscle. Clinical presentation Patients present with horizontal diplopia with an inability to abduct the ipsilateral eye, thereby resulting in an esotropia. Pathology The abducens nerve has t...
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Aberrant arachnoid granulations

Aberrant arachnoid granulations are arachnoid granulations that penetrated the dura but failed to migrate normally in the venous sinus. They are most often located in the greater wing of the sphenoid bone. Occasionally, they are seen in the posterior temporal bone wall. Clinical presentation A...
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Aberrant internal carotid artery

Aberrant internal carotid artery is a variant of the internal carotid artery (ICA) and represents a collateral pathway resulting from involution of the normal cervical portion (first embryonic segment) of the ICA 5. There is consequent enlargement of the usually small collaterals which course t...
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Abscess

Abscesses are focal confined collections of suppurative inflammatory material and can be thought of as having three components 1: a central core consisting of necrotic inflammatory cells and local tissue peripheral halo of viable neutrophils surrounded by a 'capsule' with dilated blood vessel...
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Absent septum pellucidum

An absent septum pellucidum may rarely be an isolated finding, or more commonly be seen in association with a variety of conditions. Epidemiology The septum pellucidum is partly or entirely absent in 2 or 3 individuals per 100,000 in the general population.  Pathology An absent septum pelluc...
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Acaeruloplasminaemia

Acaeruloplasminaemia is an autosomal recessive type of neurodegeneration with brain iron accumulation and disorder of iron metabolism caused by a mutation in the caeruloplasmin (CP) gene resulting in the production of dysfunctional caeruloplasmin. Epidemiology Acaeruloplasminaemia is a very ra...
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Accessory middle cerebral artery

The accessory middle cerebral artery is a variant of the middle cerebral artery (MCA) that arises from the anterior cerebral artery (ACA). It is different from a duplicated middle cerebral artery, in which the duplicated vessel originates also from the distal end of the internal carotid artery (...
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Achondroplasia

Achondroplasia is a congenital genetic disorder resulting in rhizomelic dwarfism and is the most common skeletal dysplasia. It has numerous distinctive radiographic features.  Epidemiology It occurs due to sporadic mutations in the majority of cases but can be inherited as an autosomal dominan...
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Achondroplastic base of skull abnormalities

Achondroplasia is the most common cause of short-limb dwarfism. (For a general discussion, see the generic article on achondroplasia.) As the skull base forms by endochondral ossification whereas the skull vault by membranous ossification, there is a marked discrepancy in relative size as the s...
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Acoustic schwannoma

Acoustic schwannomas, also known as vestibular schwannomas, are relatively common tumours that arise from the vestibulocochlear nerve (CN VIII) and represent ~80% of cerebellopontine angle masses. Bilateral acoustic schwannomas are strongly suggestive of neurofibromatosis type 2 (NF2). On imagi...
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Acquired hepatocerebral degeneration

Acquired hepatocerebral degeneration is an uncommon irreversible extrapyramidal neurodegenerative condition encountered in patients with cirrhotic chronic liver disease, resulting in widespread cerebral, basal ganglia and cerebellar damage.  Terminology Acquired hepatocerebral degeneration is ...
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Acquired tonsillar ectopia

Acquired tonsillar ectopia is usually thought of as a subgroup of cerebellar tonsillar ectopia in which downward displacement of the cerebellar tonsils is secondary to another well defined and distinct pathological process. This is to distinguish it from Chiari I malformations and low-lying tons...
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Acquired tracheo-oesophageal fistula

An acquired tracheo-oesophageal fistula refers to a pathological communication between the trachea and oesophagus due to a secondary cause  Pathology Acquired causes of tracheo-oesophagal fistulae can be divided into those that are related to malignancy (common) and those from other causes (un...
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Acrania

Acrania is a rare lethal congenital anomaly characterised by an absence of the calvaria. Epidemiology The estimated incidence is at ~1:1000 pregnancies 4.  Pathology  The condition is thought to result from abnormal migration of mesenchymal tissue, which normally covers the cerebral hemisphe...
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Acrania anencephaly sequence

Acrania anencephaly sequence is the progression from a relatively normal-appearing exposed brain due to an absent cranium (acrania) to an amorphous brain mass (exencephaly) to no recognisable brain tissue (anencephaly) 1. Epidemiology The acrania anencephaly sequence begins with acrania, which...
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Acromegaly

Acromegaly is the result of excessive growth hormone production in skeletally mature patients, most commonly from a pituitary adenoma. The same excess of growth hormone in individuals whose epiphyses have not fused will result in gigantism (excessively tall stature).   Epidemiology Acromegaly ...
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Acute bacterial meningitis complications (mnemonic)

The complications of acute bacterial meningitis can be remembered using the mnemonic: HACTIVE Mnemonic H: hydrocephalus A: abscess C: cerebritis / cranial nerve lesion T: thrombosis I: infarct V: ventriculitis/vasculopathy E: extra-axial collection: empyema and hygroma Related articles...
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Acute basilar artery occlusion

Acute occlusion of the basilar artery may cause brainstem or thalamic ischaemia or infarction. It is a true neuro-interventional emergency and, if not treated early, brainstem infarction results in rapid deterioration in the level of consciousness and ultimately death. Epidemiology Occlusions ...
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Acute cerebellitis

Acute cerebellitis, also known as acute cerebellar ataxia, is a rare inflammatory process characterised by a sudden onset of cerebellar dysfunction usually affecting children. It is related as a consequence of a primary or secondary infection, or much less commonly as a result of a post-vaccinat...
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Acute disseminated encephalomyelitis (ADEM)

Acute disseminated encephalomyelitis (ADEM), as the name would suggest, is featured by a monophasic acute inflammation and demyelination of white matter typically following a recent (1-2 weeks prior) viral infection or vaccination 4,6. Grey matter, especially that of the basal ganglia, is also o...
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Acute haemorrhagic leukoencephalitis

Acute haemorrhagic encephalomyelitis (AHEM), also known as acute haemorrhagic leukoencephalitis (AHLE), Hurst disease or Weston Hurst syndrome, is a very rare form of demyelinating disease. It occurs sporadically and may be considered as the most severe form of acute disseminated encephalomyelit...
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Acute necrotising encephalitis of childhood

Acute necrotising encephalitis of childhood (ANEC) is a rare type of encephalopathy characterized by multiple bilateral brain lesions, mainly involving the thalami, but also the putamina, internal and external capsules, cerebellar white matter, and the brainstem tegmentum. Epidemiology ANEC is...
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Acute spinal cord ischaemia syndrome

Acute spinal cord ischaemia syndrome (ASCIS) is uncommon, but usually presents with profound neurological signs and symptoms, and the prognosis is poor.  Epidemiology Acute spinal cord ischaemia syndrome represents only 5-8% of acute myelopathies 4,5 and <1% of all strokes 7. The demographic o...
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Acute vs chronic ischaemic stroke

Differentiating between acute and chronic infarction on a CT brain is an important skill for many health professionals particularly in the emergency setting: pathology acute: cytotoxic oedema chronic: encephalomalacia; Wallerian degeneration hypoattenuation acute: more dense than CSF chron...
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ADC pseudonormalisation

ADC pseudonormalisation is a normal phase encountered in the subacute stage of ischaemic stroke and represents an apparent return to normal healthy brain values on ADC maps which does not, however, represent true resolution of ischaemic damage. ADC pseudonormalisation is seen typically around 1...
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Adie pupil

Adie pupil (also known as tonic pupil) is caused by idiopathic degeneration of the ciliary ganglion, which sometimes occurs following a viral or bacterial illness. It is usually unilateral and typically affects young females 1. Adie pupil represents a large dilated "tonic pupil", which does not...
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Adie syndrome

Adie syndrome consists of a classic triad of: diaphoresis absent deep tendon reflexes, e.g. ankle jerk an Adie pupil: tonically dilated and responds poorly or not at all to light It is thought to result from damage to the ciliary ganglion and the dorsal root ganglion by viral or bacterial in...
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Adrenal vein sampling

Adrenal vein sampling (AVS) is a procedure where blood is collected from the adrenal veins via catheter to confirm autonomous hormone production, if it is unilateral or bilateral, and to guide further treatment. Indication AVS is commonly performed in primary aldosteronism, being indicated to ...
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Adrenoleukodystrophy

Adrenoleukodystrophy (ALD) is an X-linked inherited metabolic peroxisomal disorder characterised by a lack of oxidation of very long chain fatty acids (VLCFAs) that results in severe inflammatory demyelination of the periventricular deep white matter with posterior-predominant pattern and early ...
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Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia

Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP), also known as hereditary diffuse leukoencephalopathy with spheroids (HDLS) and pigmentary orthochromatic leukodystrophy (POLD), refers to a rare inherited autosomal dominant disease characterised by an adult-onset l...
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Ageing blood on MRI

The imaging characteristics of blood on MRI can be variable and change with the age of the blood. In general, five stages of haematoma evolution are recognised: hyperacute intracellular oxyhaemoglobin isointense on T1 isointense to hyperintense on T2 acute (1 to 2 days) intracellular deo...
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Ageing blood on MRI (mnemonic)

Ageing blood on MRI is dependent on the varying MRI signal characteristics of haemorrhagic collections with time and can be very useful in correlating the imaging findings with the clinical picture. However, as it can be complicated to recall the MRI features of ageing blood through the five sta...
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Agnosia

Agnosia is a neurological disorder characterised by an inability to identify an object despite both having knowledge of that object and functional sensory input. For example, a patient with posterior cortical atrophy who characteristically have visual agnosia, will be unable to identify a hammer...
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AICA-PICA dominance

AICA-PICA dominance refers to the principle that the cerebellar vascular territory supplied by the anterior inferior cerebellar artery and posterior inferior cerebellar artery have a reciprocal arrangement. That is the size of the AICA and the subsequent territory it supplies is inversely propor...
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Aicardi syndrome

Aicardi syndrome is a rare severe developmental disorder. It results from an X-linked genetic defect that is fatal in males and therefore only manifests in females (except for rare 47-XXY cases). Clinical features The typical presentation in infancy is with a triad of: infantile spasms: salaa...
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AIDS-defining illness

AIDS-defining illnesses are conditions that in the setting of a HIV infection confirm the diagnosis of AIDS, and do not commonly occur in immunocompetent individuals 2. According to the CDC surveillance case definition 1, they are: Infectious bacterial infections: multiple or recurrent candid...
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AIDS-related diffuse large B-cell lymphoma

AIDS-related diffuse large B-cell lymphomas are one of the immunodeficiency-associated CNS lymphomas, and in western countries represented a dramatic increase in primary CNS lymphoma during the HIV/AIDS epidemic of the 1980s, although the incidence is likely lower in patients treated with HAART ...
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Air bubble sign (tension pneumocephalus)

The air bubble sign is seen on CT of the brain and represents multiple small foci of air within the subarachnoid space, especially the Sylvian fissure.1 Although described as a sign of tension pneumocephalus it is also seen in pneumocephalus without elevated pressures.2   It should not be con...
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Alanine peak

Alanine is one of the compounds examined in MR spectroscopy. It resonates at 1.48 ppm chemical shift. It is elevated in meningiomas.
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Alberta stroke program early CT score (ASPECTS)

The Alberta stroke programme early CT score (ASPECTS) 1 is a 10-point quantitative topographic CT scan score used in patients with middle cerebral artery stroke. It has also been adapted for the posterior circulation (see below).  Scoring system Segmental assessment of the MCA vascular territo...
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Alexander disease

Alexander disease (AD), also known as fibrinoid leukodystrophy, is a rare fatal leukodystrophy, which usually becomes clinically evident in the infantile period, although neonatal, juvenile and even adult variants are recognised. As with many other diseases with variable age of presentation, the...
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Alien limb syndrome

Alien limb syndrome is a rare neurological phenomenon in which a patient has the impression that their limb does not belong to them and is controlled by some external force 1.  It can occur in a number of neurodegenerative diseases, typically those with cortical involvement, including: cortico...
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Allodynia

Allodynia refers to pain due to a stimulus which does not normally provoke pain. Temperature or physical stimuli can provoke allodynia, and it often occurs after injury to a site. Etymology The word allodynia is derived from the Greek words άλλος (állos) meaning "other" and οδύνη (odýni) meani...
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Alobar holoprosencephaly

Alobar holoprosencephaly is a subtype of holoprosencephaly and is the most severe of the classical three subtypes, with both semilobar and lobar holoprosencephaly having less severe clinical manifestations. For a general discussion of epidemiology, clinical presentation, and pathology, please r...
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Alpha thalassemia/mental retardation syndrome X-linked (ATRX)

Alpha-thalassemia/mental retardation syndrome X-linked (ATRX) gene is an important genomic marker of gliomas and is either intact (ATRX wild-type) or mutated (ATRX-mutant) and is correlated with other important genomic markers including IDH, 1p19q codeletion and p53 expression 1,2.  ATRX and ID...
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Alport syndrome

Alport syndrome is an X-linked dominant disease characterised by progressive sensorineural hearing loss, renal disease and, at times, ocular lesions. Clinical presentation haematuria sensorineural hearing loss: typically high frequency 2 ocular abnormalities  anterior lenticonus: most commo...
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Alzheimer disease

Alzheimer disease (AD) is a common neurodegenerative disease, responsible for 60-80% of all dementias, and imposing a significant burden on developed nations. It is the result of accumulation and deposition of cerebral amyloid-β (Aβ) and is the most common cerebral amyloid deposition disease.  ...
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Alzheimer type I glia

Alzheimer type I glia are a type of glial cell. They are large multinucleated astrocytes encountered in glial tumours and progressive multifocal leukoencephalopathy (PML) 1. 
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Alzheimer type II glia

Alzheimer type II glia are a type of glial cell. They are a pathological reactive astrocyte seen in the brain, unrelated to Alzheimer disease. They are seen most frequently in Wilson disease, but also in other systemic metabolic disorders, particularly those with elevated ammonia levels, typical...
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Amaurosis fugax

Amaurosis fugax is the transient monocular loss of vision, normally lasting a few seconds to a few minutes, secondary to vascular ischaemia or insufficiency.  Epidemiology It has an incidence of 50,000 per year in the United States.  Clinical presentation Patients present with transient mono...
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Ambient cistern

The ambient cistern is part of the subarachnoid cisterns, filled with CSF. Gross anatomy The ambient cistern is a thin, sheet-like extension of the quadrigeminal cistern that extends laterally surrounding around the midbrain and posterior to the thalami. It acts as the connection between the q...
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Amygdala

The amygdala is a very well studied part of the limbic system and forms part of the mesial temporal lobe.  Gross anatomy The amygdala is a complex structure, located dorsomedially in the temporal lobe, forming the ventral superior, and medial walls of the inferior horn of the lateral ventricle...
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Amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig disease or Charcot disease, is the most common form of motor neurone disease 1,4 resulting in progressive weakness and eventual death due to respiratory insufficiency. Epidemiology ALS typically is diagnosed in middle age. There is ...
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Anaplastic astrocytoma

Anaplastic astrocytomas are WHO grade III lesions, with imaging appearances and prognosis between those of diffuse low-grade astrocytomas (WHO grade II) and glioblastomas (WHO IV), and similarly, they are classified on the basis of IDH mutation as IDH-mutant, IDH-wild-type and NOS (when IDH stat...
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Anaplastic ependymoma

Anaplastic ependymomas (WHO grade III ependymomas), in comparison to lower grade ependymomas, are characterised by a higher proliferative rate and a greater tendency to infiltrate surrounding brain or disseminate into cerebrospinal fluid causing drop metastases 1. The relevance of grading ependy...
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Anaplastic ganglioglioma

Anaplastic gangliogliomas are uncommon aggressive variants of the far more common low-grade ganglioglioma (WHO grade I). The aggressive component is the glial (usually astrocytic) component, which demonstrates nuclear pleomorphism, increased mitotic rate and increased cellularity, as well as mic...
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Anaplastic meningioma

Anaplastic meningiomas (also known as malignant meningiomas) are uncommon, accounting for only ~1% of all meningiomas 1. Along with rhabdoid meningioma and papillary meningioma are considered WHO grade III tumours and demonstrate aggressive local growth and high recurrence rate.  It should be n...
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Anaplastic oligodendroglioma

Anaplastic oligodendroglioma is a WHO grade III diffuse infiltrating glioma that has histological features of anaplasia, and molecular markers consistent with an oligodendroglioma (1p19q co-deletion and IDH mutation) as per the current (2016) WHO classification of CNS tumours 1. They make up 20-...
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Anaplastic oligodendroglioma NOS

Anaplastic oligodendroglioma NOS (not-otherwise-specified) is a diagnosis in the current (2016) WHO classification of CNS tumours denoting a diffuse infiltrating glioma that has histological features of anaplastic oligodendroglioma, but without 1p19q co-deletion status or IDH mutation status bei...
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Anaplastic pleomorphic xanthoastrocytoma

Anaplastic pleomorphic xanthoastrocytomas are a more aggressive and less common version of pleomorphic xanthoastrocytoma (PXA).  In the current (2016) WHO classification of CNS tumours, they are considered WHO grade III lesions (whereas pleomorphic xanthoastrocytomas are WHO grade II tumours) 1...
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Anatomy curriculum

The anatomy curriculum is one of our curriculum articles and aims to be a collection of articles that represent the core anatomy knowledge for radiologists and imaging specialists. General anatomy Neuroanatomy Head and neck anatomy Thoracic anatomy Abdominal and pelvic anatomy Spinal anat...
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Ancient schwannoma

Ancient schwannomas are long-standing, benign (WHO grade I) slow growing schwannomas with advanced degeneration. These can have calcification, hyalinization, and cystic cavitation that can be identified on imaging. The term “ancient” has been traditionally used to describe schwannomas showing de...
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Anencephaly

Anencephaly is the most severe form of cranial neural tube defect (NTD) and is characterised by an absence of cortical tissue (although the brainstem and cerebellum may be variably present) as well as an absence of the cranial vault. The morphological spectrum within anencephaly ranges from holo...
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Angiocentric glioma

Angiocentric gliomas are rare superficial slow-growing brain tumours typically presenting in young patients with intractable partial epilepsy 1-6. They were first introduced in the 2007 (4th) edition of the WHO brain tumour classification, and are classified as WHO grade I tumours 1.  For a gen...
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Angiolipoma

Angiolipomas (also sometimes known as haemangiolipomas, vascular lipomas, and fibromyolipomas) are rare soft tissue tumours composed of mature adipocytes and vessels. They can occur essentially anywhere and can be subclassified into infiltrating and non-infiltrating variants 1.  Please refer to...
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Angiomatous meningioma

Angiomatous meningiomas are a rare histological variant of WHO grade I meningiomas and account for only 2.1% of all meningiomas 1,3.  The epidemiology and clinical presentation of these tumours does not clearly deviate from that of more common histological variants of meningiomas and is thus no...
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Angular gyrus

The angular gyrus is a portion of the parietal lobe of the brain. It is one of the two parts of the inferior parietal lobule, the other part being the supramarginal gyrus. It plays a part in language and number processing, memory and reasoning 1. Gross anatomy Relations It lies as a horseshoe...
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Anorexia nervosa

Anorexia nervosa is a psychiatric disorder characterised by distorted self-perception of body weight leading to starvation, obsession with remaining underweight, and an excessive fear of gaining weight. One in five patients with anorexia dies, due to complications of the disease. Epidemiology ...
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Anorexia nervosa (CNS manifestations)

CNS manifestations of anorexia nervosa are common but varied with most of the imaging features non-specific in their own right.  For a general discussion, and for links to other system specific manifestations, please refer to the article on anorexia nervosa. Epidemiology Studies have identifi...
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Anoxic brain injury

Anoxic brain injury, also known as global hypoxic-ischaemic injury, is seen in all age groups (from antenatal to the elderly) as a result of numerous aetiologies. The pattern of injury depends on a number of factors including: age of the patient (brain maturity) neonatal hypoxic-ischaemic ence...
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Anterior cerebral artery

The anterior cerebral artery along with the middle cerebral artery forms at the termination of the internal carotid artery. It is the smaller of the two, and arches anteromedially to pass anterior to the genu of the corpus callosum, dividing as it does so into its two major branches; pericallosa...
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Anterior cerebral artery (ACA) infarct

Anterior cerebral artery (ACA) territory infarcts are much less common than either middle or posterior cerebral artery territory infarcts.  Epidemiology ACA territory infarcts are rare, comprising ~2% of ischaemic strokes 1,2.  Clinical presentation ACA stroke syndrome presents as 1,2,3: dy...
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Anterior choroidal artery

The anterior choroidal artery (AChA) supplies several crucial anatomical structures of the brain important for vision and motor control. Identification of AChA is important because of its strategic and extensive area of supply as well as large variations in the territorial distribution. Gross a...
Article

Anterior choroidal artery syndrome

Anterior choroidal artery syndrome is a rare entity characterised by the triad of hemiplegia, hemianaesthesia and contralateral hemianopia as a result of cerebral infarction in the anterior choroidal artery territory. The syndrome may also be associated with neuropsychological disorders, includ...
Article

Anterior cingulate cortex

The anterior cingulate cortex (ACC), previously known as the precingulate, is a region of the brain surrounding the anterior corpus callosum. It is involved in the limbic system and the prefrontal cortex. Summary location: it is located superior to the anterior corpus callosum, more specifical...
Article

Anterior commissure

The anterior commissure (AC) is a transversely oriented commissural white matter tract that connects the two cerebral hemispheres along the midline. It is a very important anatomical landmark that connects different parts of the limbic system on both sides and plays a role in the interhemispheri...
Article

Anterior commissure - posterior commissure line

The anterior commissure - posterior commissure line (AC-PC line), also known as the bicommissural line, has been adopted as a convenient standard by the neuroimaging community, and in most instances is the reference plane for axial imaging in everyday scanning. The creation of a standard image p...
Article

Anterior communicating artery

The anterior communicating artery (ACOM) arises from the anterior cerebral artery and acts as an anastomosis between the left and right anterior cerebral circulation. Approximately 4 mm in length, it demarcates the junction between the A1 and A2 segments of the anterior cerebral artery. Branche...
Article

Anterior corticospinal tract

The anterior corticospinal tract is formed at the level of the of the medullary pyramids, where the majority (90%) of descending corticospinal tract fibres decussate to form the lateral corticospinal tract. The majority of the remaining non-decussating 10% of fibres form the much smaller anterio...
Article

Anterior epitympanic recess

The anterior epitympanic recess, also known as the supratubal recess, is a small discrete space in the epitympanum anterior to the malleus. It is separated from the epitympanum proper by the anterior attic bony plate, also known as the cog, which has its orientation in the coronal anatomical pla...
Article

Anterior ethmoidal foramen

The anterior ethmoid foramen is a small opening in the ethmoid bone. It is the anatomical border of anterior and posterior ethmoid air cells. It transmits the anterior ethmoidal artery, vein and nerve. The anterior ethmoid foramen is situated 25 mm away from the lacrimal crest, 12 mm anterior t...
Article

Anterior ethmoidal nerve

The anterior ethmoidal nerve is an extraconal branch of the nasociliary nerve, a branch of the ophthalmic division of the trigeminal nerve. Some authors describe it as either the terminal branch or a direct continuation of the nasociliary nerve.  It branches off distal to the infratrochlear nerv...
Article

Anterior fontanelle

The anterior or frontal fontanelle (or fontanel) is the diamond-shaped soft membranous gap at the junction of the coronal and sagittal sutures. It persists until approximately 18-24 months after birth, after which it is known as the bregma. The fontanelle normally measures between 0.6-3.6 cm (me...
Article

Anterior horn syndrome

Anterior horn syndrome is a fairly generic term used to refer to flaccid paralysis and areflexia due to involvement of the anterior grey matter horns of the spinal cord. Sensation is typically preserved.  Causes of anterior horn syndrome include:  anterior spinal artery ischaemia  poliomyelit...
Article

Anterior inferior cerebellar artery

The anterior inferior cerebellar artery (AICA) is one of three vessels that provides arterial blood supply to the cerebellum. It has a variable origin, course and supply, with up to 40% of specimens not having an identifiable standard AICA. The amount of tissue supplied by the AICA is variable (...
Article

Anterior inferior cerebellar artery (AICA) infarct

Anterior inferior cerebellar artery (AICA) territory infarcts are much less common than posterior inferior cerebellar artery (PICA) infarcts. Epidemiology AICA territory infarcts are rare, comprising ~1% of ischaemic cerebellar strokes 2.  Clinical presentation AICA stroke syndrome presents ...
Article

Anterior perforated substance

The anterior perforated substance, or substantia perforata anterior, is an area in the basal forebrain that plays an important role with regards to the blood supply of deep grey matter structures of the brain. Gross anatomy Located within the basal forebrain, the anterior perforated substance...

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