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.

199 results found
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Absent posterior limb sign

The absent posterior limb sign is one of the main MRI findings of prognostic significance in term neonates with suspected hypoxic-ischemic brain injury. An absent posterior limb sign is defined as loss of the normally distinct hyperintensity on T1-weighted images in the posterior part of the pos...
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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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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 confus...
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Arc sign (CARASIL)

The arc sign has been described in late-stage CARASIL and is seen on axial T2 weighted images. It describes high signal extending from one middle cerebellar peduncle, across the pons, to the contralateral middle cerebellar peduncle 1. 
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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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Astronomical inspired signs

Many signs in radiology have been inspired by astronomical phenomena: comet tail (disambiguation) comet tail artifact (ultrasound) color comet tail artifact comet tail sign (chest) comet tail sign (phleboliths) earth-heart sign galaxy sign (chest) loss of half-moon overlap sign milky wa...
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Ataxia (clinical sign)

Ataxia denotes the impaired coordination of voluntary muscle function. It is not a specific disease, but a clinical sign that can have diverse etiologies. It is typically caused by either cerebellar damage or impaired vestibular or proprioceptive afferent sensory input to the cerebellum. Clinic...
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Barbell sign (progressive multifocal leukoencephalopathy)

The barbell sign has been described in a short series of patients with progressive multifocal leukoencephalopathy (PML) 1. This describes confluent FLAIR / T2w parieto-occipital abnormalities with a thin continuation of signal abnormality across the splenium. Given the lack of mass effect typi...
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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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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 gives the fourth ventricle an appearance reminiscent of a bat with its wings outstretched. It is best demonstrat...
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Bifid postcentral gyrus sign

The bifid postcentral gyrus sign, also known as the pars deflection sign, is a landmark useful for identifying the central sulcus on cross-sectional imaging. The medial aspect of the postcentral gyrus splits in two before meeting the interhemispheric fissure. The two legs straddle the pars marg...
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Blend sign (brain)

The blend sign refers to a CT appearance of early intracranial hematoma growth. It is defined as blending of a hypoattenuating area and a hyperattenuating region with a well-defined margin.
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Boomerang sign (disambiguation)

Boomerang sign may refer to: boomerang sign (peroneus brevis tear) boomerang sign (medial meniscal tear) boomerang sign (splenium) History and etymology Boomerang is of course a curved projectile used originally by the Australian Aborigines, one of its various uses was as a hunting weapon 1.
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Boomerang sign (splenium)

The boomerang sign refers to a boomerang-shaped region of cytotoxic edema in the splenium of the corpus callosum typically seen in cytotoxic lesions of the corpus callosum (CLOCCs) 1-4.  See also boomerang sign in peroneus brevis split syndrome boomerang sign in horizontal meniscal flap tear
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Bracket sign (pars marginalis)

The bracket sign of the pars marginalis, also known as the pars bracket sign, refers to the appearances of the superior most extent of the pars marginalis of the cingulate sulcus on axial imaging. It forms two roughly symmetric brackets, open anteriorly. The next sulcus anteriorly is the central...
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Bracket sign (pericallosal lipoma)

The bracket sign refers to a radiographic appearance seen with the tubulonodular variety of pericallosal lipoma. It reflects calcification seen at the periphery of the midline lipoma. It is best seen on coronal imaging and historically was identified on frontal radiographs. It should not be con...
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Braid-like sign (spinal sarcoidosis)

The braid-like sign is an imaging pattern of sarcoidosis spinal cord involvement. It is characterized by a ventral subpial enhancement in the spinal cord.
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Bright rim sign (DNET)

The bright rim sign, also known as the hyperintense ring sign, has been described in dysembryoplastic neuroepithelial tumors (DNET). It is described as a well-defined rim of high signal around the DNET on FLAIR sequences. This T2/FLAIR hyperintense ring, whether complete or incomplete, is fairl...
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Brudzinski sign (meningism)

Brudzinski sign occurs in meningitis (of any etiology) or meningism where passive flexion of a patient's neck elicits reflexive bilateral knee and hip flexion; it was originally known as the "nape of the neck sign" and was one of several physical exam maneuvers concurrently described to be chara...
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Burst lobe

A burst lobe is an uncommonly used description of traumatic lobar intraparenchymal hemorrhage of the brain that ruptures into the subdural space and communicates with subdural hemorrhage 1. As traumatic hemorrhages are more common in the frontal and temporal lobes, these lobes are the most affe...
Article

Butterfly glioma

Butterfly gliomas are a high grade astrocytoma, usually a glioblastoma (WHO grade IV), which crosses the midline via the corpus callosum. Other white matter commissures are also occasionally involved. The term butterfly refers to the symmetric wing-like extensions across the midline.  Most freq...
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Butterfly sign (choroid plexus)

The butterfly sign refers to the normal appearance of the choroid plexuses on axial imaging of the fetal brain, commonly observed on the antenatal ultrasound. Its absence may suggest holoprosencephaly 1. In the CNS, the term should not be confused with a butterfly glioma, which is a glioblastom...
Article

Callosal angle

The callosal angle has been proposed as a useful marker of patients with idiopathic normal pressure hydrocephalus (iNPH), helpful in distinguishing these patients from those with ex-vacuo ventriculomegaly (see hydrocephalus versus atrophy).  It should be noted that there is nothing magical abou...
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Caput medusae sign (developmental venous anomaly)

The caput medusae sign refers to developmental venous anomalies of the brain, where a number of veins drain centrally towards a single drain vein. The appearance is reminiscent of Medusa, a gorgon of Greek mythology, who was encountered and defeated by Perseus. The sign is seen on both CT and M...
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Central vein sign

The central vein sign is a marker for multiple sclerosis (MS) and is the imaging manifestation of the perivenular nature of demyelinating plaques. It is not pathognomonic but can be useful in helping differentiate multiple sclerosis from mimics, such as cerebral small vessel disease, neuromyelit...
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Cerebral paragonimiasis

Cerebral paragonimiasis refers to brain infection with a specific genus of flukes and is a serious manifestation of paragonimiasis, which is primarily a lung disease caused by trematodes of the genus Paragonimus. Epidemiology Paragonimiasis is endemic in Asia, West Africa, and Latin America. I...
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Cingulate island sign

The cingulate island sign is a highly specific radiological sign described in dementia with Lewy bodies. It refers to the pattern of metabolism seen on FDG-PET in patients with dementia with Lewy bodies 1-3. On FDG-PET, there is occipital hypometabolism with relative sparing of the posterior ci...
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Cingulate sulcus sign

The cingulate sulcus sign has been proposed as being useful as an MRI feature of idiopathic normal pressure hydrocephalus (NPH). It denotes the posterior part of the cingulate sulcus being narrower than the anterior part. The divider between the anterior and posterior parts of the sulcus being a...
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Claustrum sign

The claustrum sign refers to the bilateral claustral involvement seen in febrile infection-related epilepsy syndrome (FIRES). This sign is described in T2 and FLAIR sequences, seen as hyperintensity of both claustra during the acute phase and posterior hypointensity during the chronic phase if ...
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Claw sign (mass)

The claw sign is useful in determining that a mass arises from a solid structure rather than is located adjacent to it and distorts the outline. It refers to the sharp angles on either side of the mass, which the surrounding normal parenchyma forms when the mass has arisen from the parenchyma. ...
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Concentric target sign (cerebral toxoplasmosis)

The concentric target sign is a typical sign for cerebral toxoplasmosis. It is seen on T2 weighted MR imaging as a deep parenchymal lesion showing a series of concentric rings with hyperintense and hypointense/isointense signal alternatingly. Strong perifocal edema is usually visible on T2/FLAIR...
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Copper beaten skull

Copper beaten skull, also known as beaten silver skull or beaten brass skull, refers to the prominence of convolutional markings (gyral impressions on the inner table of the skull) seen throughout the skull vault. Clinical presentation The appearance of a copper beaten skull is associated with...
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Cord sign (dural sinus thrombosis)

The cord sign refers to cordlike hyperattenuation within a dural venous sinus on non-contrast enhanced CT of the brain due to dural venous sinus thrombosis. The sign is most commonly seen in the transverse sinus because along the origin of the tentorium it runs approximately in the axial plane s...
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Corkscrew sign (disambiguation)

Corkscrew sign can refer to: corkscrew sign (midgut volvulus) corkscrew sign (tertiary esophageal contractions) corkscrew sign (corkscrew cochlea)
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Cortical vein sign

The cortical vein sign refers to the presence of superficial cortical veins seen on MRI and CT (particularly with contrast injection) traversing an enlarged subarachnoid space, differentiating it from the similar radiological appearance of a subdural hygroma. Although initially proposed as a me...
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Cotton wool appearance (bone)

The cotton wool appearance is a plain film sign of Paget disease and results from thickened, disorganized trabeculae which lead to areas of sclerosis in a previously lucent area of bone, typically the skull. These sclerotic patches are poorly defined and fluffy. See also Other Paget disease re...
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CSF cleft sign

The CSF cleft sign in neuroimaging can be used to distinguish an extra-axial lesion from an intra-axial lesion and is typically used in the description of a meningioma. Classically, the cleft was regarded as representing a thin rim of CSF between a tumor and brain parenchyma. However, it often ...
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CT angiographic spot sign (intracerebral hemorrhage)

The spot sign is a CTA sign in acute intracerebral hemorrhage and representing the focal accumulation/pooling/extravasation of contrast containing blood within the hematomas. It is an important feature to identify during the evaluation of acute intracerebral hemorrhage as it significantly increa...
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CT comma sign (head)

The CT comma sign is a characteristic sign seen in head trauma. It is the presence of concurrent epidural and subdural hematomas, which gives the characteristic appearance of this sign as a "comma" shape.
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Cyst with dot sign (neurocysticercosis)

The cyst with dot sign is seen in neurocysticercosis and represents the parasitic cyst with, usually eccentric, scolex. It can be seen on both MRI and CT at: the vesicular stage (CSF density / intensity cyst - denser / hyperintense scolex) and colloidal vesicular stage (enhancement of wall an...
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Dawson fingers

Dawson fingers are a radiographic feature of demyelination characterized by periventricular demyelinating plaques distributed along the axis of medullary veins, perpendicular to the body of the lateral ventricles and/or callosal junction. This is thought to reflect perivenular inflammation. They...
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Delta sign (disambiguation)

The delta sign has been described in several different pathologies: delta sign (brain) empty delta sign (brain) double delta sign (MSK)
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Dense vein sign

The dense vein sign refers to hyperattenuating thrombus within a cortical vein or dural venous sinus due to acute venous thrombosis. When located in the superior sagittal sinus, particularly posteriorly, it is sometimes referred to as the delta, triangle or pseudodelta sign. It is really the sa...
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Depth-of-fissure sign

The depth-of-fissure sign, also known as apex-of-fissure sign or bottom-of-fissure sign, is a radiographic sign that helps to recognize cerebellar infarcts in children as well as in adults 1-3. Usage  The 'depth-of-fissure' sign is recognized on cross-sectional imaging studies of the brain, es...
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Disappearing basal ganglia sign

The disappearing basal ganglia sign is one of the early signs of a middle cerebral artery (MCA) infarction. It is defined as the loss of delineation of the basal ganglia, due to blurring of their grey-white matter interface and hypoattenuation, consequent to cytotoxic edema at the time of an isc...
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Double density sign (berry aneurysm)

Double density sign of berry aneurysms refers to the angiographic appearance of a small intracranial aneurysm projecting in front or behind a vessel of similar caliber. As such, the border of the aneurysm cannot easily be seen, but the extra contrast within it can be seen as a rounded area of in...
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Double density sign (osteoid osteoma)

The double density sign, also sometimes clumsily referred to as the hotter spot within hot area sign, is a bone scan sign of an osteoid osteoma. It refers to a central focus of intense uptake (the nidus) within a surrounding lower, but nonetheless increased uptake, rim. See also double densit...
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Double panda sign

The double panda sign refers to the combination of the face of the giant panda and face of the miniature panda (cub of the giant panda) seen on T2 weighted images of midbrain and pons respectively in Wilson disease. The midbrain face of the giant panda sign consists of normal intensity of red n...
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Double skull sign (cephalohematoma)

The double skull sign is an eggshell calcification seen on CT in early cases of calcified cephalohematomas.
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Doughnut sign (orbit)

The doughnut sign of optic nerve sheath meningioma refers to the appearance of this tumor on coronal CT/MRI. The meningioma forms a thick cuff of enhancing tumor around the central non-enhancing optic nerve, mimicking the appearance of a ring doughnut. It is the coronal equivalent of the tram-tr...
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Dual rim sign (brain abscess)

The dual or double rim sign is seen on MRI in approximately 75% of cerebral abscesses and is helpful in distinguishing an abscess from a glioblastoma.  On both susceptibility weighted imaging (SWI) and T2WI it consists of two concentric rims surrounding the abscess cavity, outer one of which is...
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Dumbbell appearance of spinal tumors

The dumbbell appearance of spinal tumors refers to a tumor which has both a component within the canal and a component in the paravertebral space contiguous with each other via a thinner tumor component traversing the neural exit foramen. The appearance can be seen in: spinal nerve sheath tumo...
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Dural tail sign

The dural tail sign occurs as a result of thickening and enhancement of the dura and is most often seen adjacent to a meningioma. Initially, the sign was felt to be pathognomonic of meningiomas, however as radiologist's experience grew, it has become increasingly noted to be present in many oth...
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Ears of the lynx sign (brain)

The ears of the lynx sign refers to abnormal T2/FLAIR cone-shaped hyperintensity at the tip of the frontal horn of the lateral ventricles in the region of forceps minor which resembles the tufts of hair crowning the ears of a lynx. This sign is seen in hereditary spastic paraplegia with thin co...
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Eccentric target sign (cerebral toxoplasmosis)

The eccentric target sign is considered pathognomonic for cerebral toxoplasmosis. It is seen on postcontrast MRI/CT as a ring enhancing lesion with an eccentrically located enhancing mural nodule. It is believed that this mural nodule is an extension from the abscess wall itself with inflamed ve...
Article

Empty delta sign (dural venous sinus thrombosis)

The empty delta sign is a CT sign of dural venous sinus thrombosis of the superior sagittal sinus, where contrast outlines a triangular filling defect, which represents thrombus. It is only described with CECT-scan or MRI, not with NECT nor non-contrast MRI. An equivalent appearance can be note...
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Empty light bulb sign (brain death)

In brain death, on Tc-99m HMPAO imaging there is absent or reduced flow in the internal carotid arteries and increased flow within the external carotid arteries. This leads to absent uptake in the brain with subsequent increased perfusion in the nasal region. This appearance has been called the ...
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Empty thecal sac sign

The empty thecal sac sign or empty sac sign is when the thecal sac appears empty on MRI of the lumbar spine, best seen on T2-weighted images. If the empty thecal sac sign is present, a diagnosis of adhesive arachnoiditis can be made.​ Radiographic features MRI There is usually no gadolinium c...
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Ependymal dot-dash sign

The ependymal dot-dash sign has been described as an early MRI imaging feature of multiple sclerosis before other more florid white matter changes (e.g. Dawson's fingers) become evident 1. It has also been suggested as a feature that can be used to distinguish multiple sclerosis from neuromyelit...
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État criblé

État criblé, also known as status cribrosum, is a term that describes the diffusely widened perivascular spaces (Virchow-Robin spaces) in the basal ganglia, especially in the corpus striatum on MRI. It is usually symmetrical, with the perivascular spaces showing CSF signal and without diffusion ...
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État lacunaire

État lacunaire is a term describing the presence of multiple lacunar infarcts, which are ischemic strokes due to occlusion of penetrating cerebral arterioles, especially in the basal ganglia. The term has been strongly described as a pathological substrate for a multi-infarct vascular dementia 4...
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Extracranial brain herniation

Extracranial or transcalvarial brain herniation refers to herniation of brain tissue external to the calvaria through a skull bone defect, which may be post-traumatic or post-surgical. Unlike encephaloceles, brain herniation is not surrounded by the meninges.  Craniectomy may be performed to de...
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Eye of the tiger sign (globus pallidus)

The eye of the tiger sign refers to symmetric bilateral abnormal low signal on T2-weighted MRI (due to abnormal accumulation of iron) in the globus pallidus with central high signal (due to gliosis and spongiosis). The eye of the tiger sign is most classically associated with pantothenate kinas...
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Face of the giant panda sign (midbrain)

The face of the giant panda sign in neuroimaging refers to the appearance of the midbrain, when the red nucleus and substantia nigra are surrounded by high T2 signal in the tegmentum. It is classically seen in Wilson disease, although whenever the white matter is diffusely abnormal in the regio...
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Figure of eight appearance

The following lesions may resemble a figure of eight (sometimes referred to as snowman shaped): supracardiac variety of total anomalous pulmonary venous return 1 pituitary macroadenoma with suprasellar extension 2 intraspinal neurofibroma with extraspinal extension through neural foramina di...
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Flame sign (spinal cord metastasis)

The flame sign has been described as a helpful MRI sign of spinal cord metastases, enabling them to be distinguished from other enhancing spinal cord lesions (e.g. ependymoma, astrocytoma and hemangioblastoma) 1.  Radiographic features MRI The flame sign is seen on sagittal post contrast T1 w...
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Flat floor of fourth ventricle sign

The flat floor of fourth ventricle sign is useful in detecting a pontine mass and is a sign of mass effect. The normal floor of the fourth ventricle (remember that the floor is anterior) normally slopes upwards towards the midline, with the facial colliculi visible on either side.  It is a non-...
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Fogging phenomenon (cerebral infarct)

The fogging phenomenon is seen on non-contrast CT of the brain and represents a transient phase of the evolution of cerebral infarct where the region of cortical infarction regains a near-normal appearance.  During the first week following a cortical infarct, hypoattenuation and swelling become...
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Hematocrit effect

The hematocrit effect with fluid-fluid levels is the result by layering of heavier cellular elements of blood located dependent to a liquid supernatant. It can be seen on CT or MRI. It is most frequently seen in the setting of anticoagulation therapy or coagulopathy. See also signal flare phen...
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Hemosiderin cap sign

The hemosiderin cap sign refers to an MR imaging feature in some spinal tumors where a cap of T2 hypointense hemosiderin is above and/or below the tumor due to previous hemorrhage.  It is most often associated with spinal cord ependymomas (20-33% of cases) 1. It may also be seen in hemangioblas...
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Hair on end sign (mnemonic)

The hair on end sign refers to a radiographic appearance of the diploic space of the skull vault which results from a thickening of trabeculae as the diploic space expands. These trabeculae are perpendicular in orientation, interspersed by radiolucent marrow hyperplasia along with skull vault. ...
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Harlequin eye deformity

The harlequin eye deformity is characterized by elevation of the superolateral corner of the orbit. It may be seen in unilateral (plagiocephaly) or bilateral (brachycephaly) coronal suture synostosis. History and etymology The term harlequin eye derives from the appearance of the eyes on a har...
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Hockey stick sign (Creutzfeldt-Jakob disease)

The hockey stick sign refers to the hyperintense signal involving the pulvinar and dorsomedial thalamic nuclei bilaterally on FLAIR, in cases of variant Creutzfeldt-Jakob disease, which has the shape of a hockey stick. See also pulvinar sign (Creutzfeldt-Jakob disease) hockey stick sign (thyr...
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Hockey stick sign (disambiguation)

The hockey stick sign can refer to a variety of different signs and appearances: hockey stick sign (thyroid hemiagenesis) hockey stick sign (Creutzfeldt-Jakob disease) hockey stick sign (ureters)
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Hot cross bun sign (pons)

The hot cross bun sign refers to the MRI appearance of the pons when T2 hyperintensity forms a cross on axial images, representing selective degeneration of transverse pontocerebellar tracts and median pontine raphe nuclei. It has been described in a variety of neurodegenerative diseases 1: mul...
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Hot nose sign

The hot nose sign refers to increased perfusion in the nasal region on nuclear medicine cerebral perfusion studies in the setting of brain death. The absent or reduced flow in the internal carotid arteries is thought to lead to increased flow within the external carotid arteries and subsequent i...
Article

Hummingbird sign (midbrain)

The hummingbird sign, also known as the penguin sign, refers to the appearance of the brainstem in patients with progressive supranuclear palsy (PSP).  The atrophy of the midbrain results in a profile of the brainstem (in the sagittal plane) in which the preserved pons forms the body of the bir...
Article

Hutchinson pupil

Hutchinson pupil is a fixed and dilated pupil caused by compression of the oculomotor nerve (CN III) as a result of uncal herniation. It should not be confused with any of the following: Hutchinson triad Hutchinson freckle Hutchinson teeth Hutchinson sign Hutchinson syndrome History and e...
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Hutchinson sign (disambiguation)

The Hutchinson sign can refer to two clinical signs.  Hutchinson sign (ophthalmology) Relates to involvement of the tip of the nose from facial herpes zoster. It implies involvement of the external nasal branch of the nasociliary nerve (branch of the ophthalmic division of the trigeminal nerve...
Article

Hyperdense MCA sign (brain)

The hyperdense MCA sign refers to focal hyperdensity of the middle cerebral artery (MCA) on non-contrast brain CT and is the direct visualization of thromboembolic material within the lumen. It is thus the earliest visible sign of MCA infarction as it is seen within 90 minutes after the event 1....
Article

Hypomelanotic macules

Hypomelanotic macules are otherwise known as ash-leaf spots due to their resemblance to Sorbus aucuparia, or mountain-ash, leaves. These macules have a strong association with tuberous sclerosis and are often multiple and present in the vast majority of individuals with the condition (up to 97% ...
Article

Ice cream cone sign (disambiguation)

The ice cream cone sign may refer to: ice cream cone sign (middle ear ossicles) ice cream cone sign (vestibular schwannoma)
Article

Imaging psoas sign (spondylodiscitis)

The imaging psoas sign is an MRI finding specific for spondylodiscitis and is seen as T2 hyperintensity in the psoas major muscle. The sign has a high sensitivity (92%) and specificity (92%) for spondylodiscitis and in the clinical context of a suspected infective process of the spine supports c...
Article

Infundibulum sign (pituitary)

The infundibulum sign is helpful in distinguishing an empty pituitary sella from a cystic lesion of the pituitary region 1.  In the former, although the sella is enlarged, there is no mass as such and the pituitary infundibulum traverses the enlarged sella to its floor where residual pituitary ...
Article

Interpeduncular angle

The interpeduncular angle is defined as the angle formed by the posterior half of the cerebral peduncles on axial images. The interpeduncular angle has been proposed as a sensitive and specific measure of intracranial hypotension (reduced) and progressive supranuclear palsy (PSP) (increased)1,2....
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Intracranial arterial beading

Intracranial arterial beading represents alternating areas of constriction in the intracranial arteries that gives the appearance of beads strung together. Differential diagnosis The various conditions where this may be seen are: cerebral vasculitis radiation therapy cerebral vasospasm post...
Article

Inverted V sign (disambiguation)

The inverted V sign has been described in several different pathologies: inverted V sign (pneumoperitoneum) inverted V sign (spinal cord)
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Inverted "V" sign (spinal cord)

The inverted "V" sign, also known as the inverted rabbit ears sign, is a radiological sign described in subacute combined degeneration of the spinal cord​. It refers to the appearance of the spinal cord on axial MRI slices 1-3. On these slices in a patient with subacute combined degeneration of...
Article

Iris sign

The iris sign is the imaging appearance of deep medullary venous thrombosis/congestion-related white matter injury in neonates created by fan-shaped, outwards radiating hemorrhages or cytotoxic edema in the subcortical and periventricular cerebral white matter. The appearance resembles the flowe...
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Ivy sign (brain)

The ivy sign refers to the MRI appearance of patients with moyamoya disease or moyamoya syndrome. Prominent leptomeningeal collaterals result in vivid contrast enhancement and high signal on FLAIR due to slow flow. The appearance is reminiscent of the brain having been covered with ivy. Differe...
Article

J-shaped sella

A J-shaped sella is a variant morphology of the sella turcica, whereby the tuberculum sellae is flattened, thus forming the straight edge of the "J". The dorsum sellae remains rounded and forms the loop of the "J". Differential diagnosis Differential diagnosis for a J-shaped sella includes 1,2...
Article

Kernohan phenomenon

Kernohan notch phenomenon is an imaging finding resulting from extensive midline shift due to mass effect, resulting in the indentation in the contralateral cerebral crus by the tentorium cerebelli. This has also been referred to as Kernohan-Woltman notch phenomenon and false localizing sign. C...

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