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.

1,956 results found
Article

14-3-3 protein

14-3-3 protein is found in the cerebrospinal fluid (CSF), and is currently used to help identify patients with sporadic Creutzfeldt-Jakob disease (sCJD).  In diagnosing sCJD, the sensitivity of 14-3-3 protein is 92% and its specificity is 80% 1. A negative 14-3-3 assay may be helpful in reducin...
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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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Aberrant arachnoid granulations

Aberrant arachnoid granulations (AbAG) 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 at the posterior temporal bone wall. Clinical presenta...
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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 comprised of necrotic inflammatory cells and local tissue peripheral halo of viable neutrophils surrounded by a 'capsule' with dilated blood vessels...
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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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AC-PC line

The anterior commissure - posterior commissure line (AC-PC line), also referred 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 imag...
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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). These tu...
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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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Acrania

Acrania is a rare lethal congenital anomaly characterised by an absence of the calvarium. 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 hemisph...
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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).   It is most commonly diagn...
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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 articl...
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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 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 necrotizing 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 resolution of ischemic damage. ADC pseudonormalisation is seen typically between around 1...
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Adie syndrome

Adie syndrome was named after the British physician and neurologist William John Adie (b. 1886 - d. 1935).  It consists of a classic triad of: diaphoreseis 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 ...
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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 characterized by an adult-onset l...
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Ageing blood on MRI

The imaging characteristics of blood on MRI are 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 deoxyh...
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Ageing blood on MRI (mnemonic)

Ageing blood on MRI is dependent on the varying MR 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 stag...
Article

Agnosia

Agnosia is a neurological disorder characterised by an inability to identify an object despite both having knowledge of that object and sensory input that is functional. For example a patient with posterior cortical atrophy, which characteristically has visual agnosia, will be unable to identify...
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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...
Article

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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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.
Article

Alberta stroke program early CT score

The Alberta stroke programe early CT score (ASPECTS) 1 is a 10-point quantitative topographic CT scan score used in patients with middle cerebral artery (MCA) stroke. Segmental assessment of the MCA vascular territory is made and 1 point is deducted from the initial score of 10 for every region ...
Article

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. Historical context The word allodynia is derived from from the Greek words άλλος (állos) meaning "other" and οδύν...
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Alobar holoprosencephaly

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

Alpha-thalassemia/mental retardation syndrome X-linked (ATRX) is an important genomic marker of gliomas. Loss/mutation of ATRX is almost never seen in patients with 1p/19q co-deletion (i.e. they are essentially mutually exclusive). Oligodendrogliomas will, therefore, have intact ATRX and 1p19q c...
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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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Ambient cistern

The ambient cistern is part of the subarachnoid cisterns. 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 quadrigeminal cist...
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Ameloblastic fibroma

Ameloblastic fibromas, appear as unilocular lucent mandibular lesions, most frequently in the posterior mandible and are usually associated with impacted teeth, centred on the un-erupted crown. They therefore appear very similar to unilocular ameloblastomas. They are composed of enamel and embry...
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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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Amyloidosis

Amyloidosis is a heterogeneous disease or even considered a constellation of diseases resulting in a deposition relatively similar proteins. It has many causes and can affect essentially any organ system. Epidemiology  There may be male predilection. Typically affects middle-aged individuals a...
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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 neuron disease 1,4 resulting in progressive weakness and eventual death. Epidemiology ALS typically is diagnosed in middle age. There is a recognised male predilection 1. ...
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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 ependymoma) 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 ependymomas is questionable, and molecular subgrou...
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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 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. General anatomy Neuroanatomy Head and neck anatomy Thoracic anatomy Abdominal and pelvic anatomy Spinal anatomy Lower limb anatomy Upper limb anato...
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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 absence of cortical tissue (although brainstem and cerebellum may be variably present) as well as absence of the cranial vault. The morphological spectrum within anencephaly ranges from holocrania (mo...
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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.  On imagin...
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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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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...
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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...
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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...
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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...
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Anterior cord syndrome

Anterior cord syndrome (also known as Beck's syndrome or anterior spinal artery syndrome) is a clinical subset of spinal cord injury syndromes, due to ischaemia/infarction of the anterior two-thirds of the spinal cord, typically sparing posterior third. Clinical presentation Patient present wi...
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 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 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 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 ...
Article

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.  ...
Article

Anterior sacral meningocoele

Anterior sacral meningocoele 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 malfo...
Article

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 arteries (one of which is usually bigger than the other) anastamose in the midline to form a single anterior spinal artery at the level...
Article

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...
Article

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...
Article

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...
Article

Anti NMDA 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...
Article

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...
Article

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. Pathology Patients have circulating antiphospholipid antibodies cross-re...
Article

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. 
Article

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...
Article

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...
Article

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...
Article

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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