Views and Reviews Power of the Metaphor: Forty Signs on Brain Imaging Rahsan Gocmen, MD, Ezgi Guler, MD, Ilgaz Cagatay Kose, MD, Kader K. Oguz, MD From the Department of Radiology, Hacettepe University Faculty of Medicine, Sihhiye, Ankara 06100, Turkey
ABSTRACT We retrospectively reviewed neuroradiology database at our tertiary-care hospital to search for patients with metaphoric or descriptive signs on brain computed tomography or magnetic resonance imaging. Only patients who had clinical or pathological definitive diagnosis were included in this review.
Keywords: Brain, signs, magnetic resonance imaging, computed tomography. Acceptance: Received October 25, 2013. Accepted for publication November 23, 2013. Correspondence: Address correspondence to Rahsan Gocmen, Department of Radiology, Hacettepe University Faculty of Medicine, Sihhiye, Ankara 06100, Turkey. E-mail: [email protected] J Neuroimaging 2014;00:1-17. DOI: 10.1111/jon.12086
Introduction The history of the medicine is replete with metaphorical descriptions. Metaphors play an important role in medicine, particularly illustrative branches such as radiology, dermatology, microbiology, and pathology. Neuroradiology literature also encompasses a variety of interesting metaphoric and descriptive signs. We illustrate the characteristic 40 metaphoric or descriptive signs of a broad spectrum of conditions in neuroradiology. We retrospectively reviewed neuroradiology database from 2006 to 2013 at our tertiary-care hospital to search for patients with metaphoric/descriptive signs on brain computed tomography (CT) or magnetic resonance (MR) imaging. Only patients who had clinical or pathological definitive diagnosis were included in this review.
Findings A. Congenital Malformations
ages in patients with corpus callosum (CC) agenesis (Fig 2). The lack of supporting deep white matter fibers and associated the redirection of longitudinal callosal fibers (Probst bundles, arrows), result in bulging of the roof of the third ventricle into the interhemispheric fissure, widely separated and medially concaved frontal horns, with the frontal horns taking on a “steer or bull’s horn” appearance in the coronal view.2 3. “Bat-wing” sign: Joubert syndrome
Joubert syndrome is an autosomal recessive disorder where there is agenesis of the cerebellar vermis to varying degrees. There is an absence of decussation of the superior cerebellar peduncles (SCP) and pyramidal tracts. The absence of the vermis is responsible for a dilated, distorted, and rostrally deviated fourth ventricle; and it causes an appearance of a “bat-wing” or an umbrella3 (Fig 3A and B).
1. “Tectal beaking” sign: Chiari II malformation
“Tectal beaking” refers to the triangular (beaked) appearance of the tectum on the sagittal views in Chiari type-II (Arnold-Chiari) malformation.1 The midbrain is elongated caudally and posteriorly to overlie the midline cerebellum and the pons (Fig 1). Variable degrees of fusion of the colliculi and tectum result in a beaked tectum. 2. “Steer-horn” ventricles: Agenesis of the corpus callosum
The “steer-horn” sign refers to the abnormal shape of the frontal horns of the lateral ventricles on coronal MR im-
4. “Molar tooth” sign: Joubert syndrome
The deeper and wider interpeduncular cistern (Fig 4A; arrow) and thicker, elongated, and horizontal SCP (Fig 4B; arrows) give the shape of a “molar tooth” on MR axial images; this is one of the most consistent imaging finding in Joubert syndrome.4 Also note that a lack of “central red dot” sign (Fig 4C) corresponding to the decussating fibers of the SCP on axial colored-fractional anisotropy (FA) map image. The FA map in a normal individual shows “central red dot” sign (Fig 4D).
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Fig 1. 5. “Tram-track” sign: Sturge-Weber syndrome
“The tram-track” sign is caused by cortical calcifications in Sturge-Weber syndrome.5 This sign can be observed on plain radiograph, noncontrast CT (NCCT) scans (Fig 5A). On NCCT, “tram-track” calcification is usually seen before 2 years of age. The metaphor of the tram-track which is one of the most favorite radiologic descriptions also has been described in optic nerve meningioma. The tram-track sign is most evident on contrast–enhanced CT or fat-suppressed T1-weighted MR images of the orbit. On these images, the optic nerve appears
Fig 3.
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Fig 2.
as an unenhanced central linear structure (negative defect) in relation to the surrounding enhancement in the area of the optic nerve sheath on either side (Fig 5B). It is helpful in distinguishing dural diseases from optic nerve glioma. 6. “Pancake” sign: Holoprosencephaly
The “pancake” sign refers to the appearance of the cerebral parenchyma in patients with a lobar holoprosencephaly (AH).6 AH, is characterized by a mono-ventricle, small, contiguous brain tissue that may have a cup, ball, or a pancake
Fig 4.
Fig 5.
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Fig 6.
Fig 8.
The “corduroy” appearance refers to thick cerebellar foliar pattern that consists of alternating bands on T1- and T2W imaging in Lhermitte-Duclos disease (LDD).7 The maintenance of the overall cerebellar architecture in spite of the thickened, and hyperplastic folia is responsible for this characteristic imaging appearance (Fig 7). LDD (also known as dysplastic gangliocytoma) is a rare probably hamartomatous disorder involving the cerebellum. The debate on whether it represents a neoplasm, malformation, or hamartoma, still continues. 8. “Figure-eight” : Lissencephaly
“Figure of 8,” also known as “hourglass configuration” refers to the appearance of the brain in the type I lissencephaly.8 Type I lissencephaly is a migration disorder of the gray matter, with the formation of a smooth, thick but four-layered cortex. Sylvian fissures are shallow, verticalized, and the brain takes a “figure-eight” configuration because of a narrowing at its middle portion by the Sylvian fissures (Fig 8). 9. “Key-hole” sign: Dandy–Walker syndrome
Fig 7.
configuration, fusion of the thalami, and absence of the interhemispheric fissure, cavum septum pellucidum, CC, optic tracts, and olfactory bulbi (Fig 6). 7. “Corduroy” sign: Lhermitte-Duclos syndrome (aka dysplastic gangliocytoma)
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The key-hole appearance is caused by communication between cisterna magna and dilated 4th ventricle9 (Fig 9A and B). The Dandy–Walker malformation complex refers to a group of congenital central nervous system (CNS) malformations that primarily involves the cerebellum and surrounding structures. The diagnostic nomenclature in this field is confusing, in part because this complex may be regarded as a spectrum of posterior fossa abnormalities, which includes dilatation of the fourth ventricle, varying degrees of cerebellar vermis hypoplasia or aplasia, and elevation of the transverse sinuses and torcular herophili. The key-hole shaped 4th ventricle has also been described in rhombencephalosynapsis (Fig 9C).
Fig 9.
Fig 10.
Fig 11.
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Fig 12.
Fig 13.
Fig 14.
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Fig 15.
Fig 17.
Fig 16.
Fig 18.
B. Vascular/Stroke 10. Dense middle cerebral artery (MCA): Acute thrombosis
The dense MCA sign is one of the early signs of infarct (Fig 10A–D). This is due an increase in density of its proximal segments, secondary to thrombosis.10 The corresponding sign on susceptibility-weighted imaging (SWI) has been called as “MCA-susceptibility-sign.” False-positive results may
occur, in cases with vascular calcification, focal subarachnoid hemorrhage in the Sylvian fissure, and high haematocrit. The dense artery sign can also be seen in basilar artery thrombosis. 11. “Cord” sign: Cortical venous thrombosis
The “cord” sign is characterized as increased density of the cortical or deep veins on NCCT, originated from the
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Fig 19. thrombosed material inside the affected vessel.11 Diagnosis of the venous infarct is elusive because of the wide variety of clinical and radiologic manifestations, mimicking arterial infarct or other diseases. “Cord” sign is a rare, but an invaluable clue for diagnosis of the venous thrombus (Fig 11A and B). 12. “Spot” sign: Active bleeding within hematoma
The “spot” sign refers to tiny enhancing foci on CT angiography (CTA) source images and refers to active bleeding.12 It’s been regarded as a predictor of hematoma expansion. NCCT scan demonstrates spontaneous intracerebral hematomain the right thalamus (Fig 12A). Axial maximum intensity projection view of CTA reveals that small foci of enhancement consistent with the “spot sign” (Fig 12B, arrow). Marked hematoma expansion is demonstrated on follow-up CT scans (Fig 12C).
Fig 21.
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Fig 20.
13. Insular “ribbon” sign: Acute MCA infarct
This refers to hypodensity and swelling of the insular cortex13 (Fig 13A, arrow). It is a very indicative and subtle early CT-sign of infarct in the territory of the ipsilateral MCA. Figure demonstrates normal insular ribbon appearance on the right cerebral hemisphere (Fig 13B). 14. “Reversal” sign or white cerebellum: Diffuse cerebral hypoxic/anoxic injury
The “reversal sign” represents severe anoxic-ischemic brain injury resulting in irreversible brain damage and carries a poor prognosis. CT features of the “reversal” sign are diffusely decreased density of cerebral cortical gray and white matter with a decreased or lost gray/white matter interface, or reversal
Fig 22.
Fig 23.
of the gray/white matter densities and relatively increased density of the thalami, brainstem, and cerebellum14 (Fig 14A and B).
unless there is an associated hemorrhage or multiloculated cavernoma. Blooming on gradient echo images are due to paramagnetic effect of blood degradation products.
15. “Popcorn” sign: Cavernous malformation
The cavernous malformation, also known as cavernous hemangioma or cavernoma, is an abnormal vascular lesion. It has typically “popcorn” appearance T1 bright locules of methemoglobin with a low signal intensity hemosiderin rim on T2W images15 (Fig 15). Perilesional edema or mass effect is unusual
16. “Zebra” sign: Remote cerebellar hemorrhage
This sign refers to typical, streaky bleeding pattern due to blood spreading in the cerebellar folia in patients with remote cerebellar hemorrhage (RCH)16 (Fig 16). RCH is usually benign, self-limited complication of supratentorial craniotomies. Temporal lobe resection for epilepsy, vascular
Fig 24.
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Fig 25.
Fig 26.
neurosurgery, or spinal surgery may be associated. Although the exact mechanism accounting for RCH remains unclear loss of cerebrospinal fluid due to an interventional process leading to cerebellar sagging, with a consequent occlusion of the bridging veins have been accused for.
perior sagittal sinus thrombosis. The exact mechanism for this appearance is uncertain, with possibilities including recanalization around an organizing clot, enlargement of the peri-dural small veins, thickening of the dura with increased enhancement.
17. “Empty delta” sign: Dural sinus thrombosis
The “empty delta” sign consists of a triangular area of enhancement or high attenuation with a relatively lowattenuating center (filling defect of thrombus) on contiguous axial contrast-enhanced CT17 (Fig 17). It is apparent in su-
Fig 27.
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18. “Caput medusa” sign: Developmental venous anomaly
The “caput medusa” sign is indicative of developmental venous anomaly (DVA), and is identifiable on contrast-enhanced CT and MR18 (Fig 18). DVAs correspond to a network of dilated, abnormal medullary veins with a radial distribution,
images, is a tangle of tiny vessels that look like a puff of smoke19 (Fig 19). Moyamoya, a name also used to describe this angiographic sign, comes from the Japanese meaning puff of smoke or hazy foggy appearance. 20. “Ivy” sign: Moyamoya disease
The “ivy” sign refers to tiny leptomeningeal high signal intensity along the cerebral sulci or on the brain surface in moyamoya disease on unenhanced fluid-attenuated inversion recovery (FLAIR) MR imaging20 (Fig 20). This sign initially was described for collateral vessels on contrast-enhanced T1W MR imaging. 21. “Hot nose” sign: Loss of cerebral blood flow; brain death
Fig 28. converging into a wide single drainage vein. This appearance is reminiscent of Medusa, a gorgon of Greek mythology. Angiographically, the caput medusa appearance is seen only in the venous phase. DVAs may be associated with cavernous angiomas or one of the other types of CNS vascular malformations (i.e., arteriovenous malformation). 19. “Puff of smoke” sign: Moyamoya disease
The “puff of smoke” sign, characteristic of moyamoya disease, is caused by the formation of collateral vessel networks from the progressive bilateral supraclinoid stenoses of the internal carotid arteries. This sign, seen on cerebral angiographic
“Hot nose” sign refers to early and increased radiotracer activity in the nasopharyngeal region at nuclear scintigraphy.21 The phenomenon is a result of occlusion of the internal carotid artery with flow rerouted to the nose via the external carotid artery. Note lack of flow to the cerebral hemispheres and abnormal increased nasopharyngeal activity (Fig 21; arrows). C. Tumors and Tumor-like Lesions 22. Dural “tail” sign: Meningioma
The dural “tail” sign is seen on contrast-enhanced MR images as a thickening of the enhanced dura mater that resembles a tail extending from the meningiomas22 (Fig 22). It was initially thought to result from direct invasion of the dura; however, subsequent studies demonstrated it to be a more reactive process. This sign, which had been described as highly specific for meningiomas once, can also be seen in other extra- and intraaxial tumors that involve the dura mater.
Fig 29.
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Fig 30.
Fig 31. 23. “Spoke-wheel” sign: Meningioma
The “spoke-wheel” sign refers to the typical angiographic appearance found in meningiomas. This sign corresponds to multiple small arteries radially distributed from dominant feeding artery.23 This figure demonstrates spoke-wheel within the meningioma mass on the axial T2W MR image (Fig 23). 24. “Butterfly” sign: Glioblastoma multiforme, lymphoma, tumefactive demiyelinating lesion
“Butterfly” sign is most commonly described in glioblastoma multiforme (GBM) syndrome, and refers to the symmetric wing like extensions across the midline through the CC.24 This appearance, however, is not pathognomonic of GBM (Fig 24A),
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and has also been reported in lymphoma and tumefactive demyelinating lesions (Fig 24B) which can involve CC. 25. “Soap bubble” sign: Dysembriyoblastic neuroepithelial tumor
Dysembryoplastic neuroepithelial tumor (DNET) is a benign tumor arising from the cortical or deep gray matter. DNET radiologically manifests as cortical masses that are hypointense on T1- and hyperintense on T2W images (Fig 25) without surrounding vasogenic edema. The “soap bubble” appearance and bright rim on FLAIR images are characteristic.25 Calcification and remodeling of the adjacent inner table of the skull may be seen.
Fig 32.
26. “Ice-cream” sign: Vestibular schwannoma
The schwannomas are the most common cerebellopontine angle (CPA) masses, while meningiomas are the second most common. They expand the internal auditory canal (IAC), as a matter of their size. The tumor resembles classic “ice-cream” appearance on axial imaging plane (Fig 26), while the component involving IAC and extension into the CPA cistern constitute ice-cream-cone and -scoop, respectively.26 D. Metabolic/Degenerative Disorders
Fig 33.
27. “The giant panda” sign: Wilson’s disease
This sign refers to a combination of signal intensity changes at midbrain on axial T2W MR imaging (Fig 27A). The pathologic high signal intensity of tegmentum represents white face of a panda while preserved intensity of red nuclei forms the eyes, pars reticulata the ears and superior colliculus represents the nose.27 At caudal sections, increased signal within the dorsal pons is called “giant panda cub” in patients with Wilson disease (Fig 27B).
Fig 34.
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Fig 35.
Fig 37.
Fig 36.
Fig 38.
28. “Eye of the tiger” sign: Pantothenate kinase-associated neurodegeneration (aka Hallervorden-Spatz syndrome)
tral high signal intensity is attributed to gliosis, increased water content, and neuronal loss.
This sign refers to symmetrical low signal intensity circumscribing a central region of high signal intensity in the internal globus pallidus on T2W MR images28 (Fig 28). The ring of marked hypointensity involving the globus pallidus on T2W MR images is due to excessive iron accumulation, and the cen-
29. “Tigroid pattern” or “leopard skin”: Metachromatic leukodystrophy
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Metachromatic leukodystrophy (MLD) is an autosomal recessive disorder caused by a deficiency of the lysosomal enzyme
30. “Hot cross bun” sign: Multisystem atrophy-cerebellar type
“Hot cross bun” sign represents the changes of the brainstem in the multiple system atrophy of the cerebellar type on axial T2W MR imaging.30 The name derived from a sweet spiced bun baked by the Christian church and marked with a cross on the top. The sign is characterized by a cruciform pontine hyperintensity due to selective loss of myelinated transverse pontocerebellar fibers and neurons, with preservation of the pontine tegmentum and the fibers of the corticospinal tract (Fig 30A and B). Note bilateral atrophy and increased T2 signal in the middle cerebellar peduncles. 31. “Tadpole” sign: Alexander disease
“Tadpole” sign is a quite peculiar feature: marked atrophy of the medulla oblongata and cervicothoracic cord with an intact pontine base, just like a “tadpole” on sagittal MR images31 (Fig 31A). Other imaging features of the Alexander disease are present in these patients, such as symmetrical frontoparietal hyperintense lesions (Fig 32A) and significantly increased myoinositol concentrations in white matter lesions at MR spectroscopy (TE = 30 msecond; Fig 32C).
Fig 39.
32. “Penguin” or “hummingbird” sign: Progressive supranuclear palsy
“Penguin” sign, also known as “hummingbird” sign refers to the atrophy of the midbrain tegmentum, with a relatively preserved pons on midsagittal T1W images in patients with progressive supranuclear palsy32 (Fig 32). The atrophy of the midbrain results in a profile of the brainstem in which the preserved pons forms the body of the bird, and the atrophic midbrain the head, with beak extending anteriorly toward the optic chiasm. Note preservation of medulla width which differs from the above “tadpole” sign. 33. “Morning glory” sign: Progressive supranuclear palsy
“Morning glory” sign refers to peculiar atrophy of the midbrain characterized by a concavity of the lateral margin of its tegmentum on the axial images.33 Also, note the marked increase in signal intensity of the periaqueductal gray region (Fig 33). E. Infection and Demyelinating Disease 34. “Trident” sign: Central pontine myelinolysis
Fig 40. arylsulfatase. The diminished activity of arylsulfatase A enzyme accounts for failure of myelin breakdown and reutilization, thus resulting in dysmyelination. On T2W MR imaging, MLD manifests as symmetric confluent areas of high signal intensity in the periventricular white matter typically sparing the subcortical U fibers during the early stages.29 The sparing of the perivascular white matter within the centrum semiovale is responsible for the characteristic “leopard skin” (Fig 29A) and “tigroid” (Fig 29B) pattern.
Central pontine myelinolysis (CPM), also known as osmotic demyelination, is an acute demyelinating condition of the brainstem and is a recognized complication of the rapid correction of chronic hyponatremia. Symptoms of CPM include tetraplegia, pseudobulbar palsy, and acute changes in mental status leading to coma or death without intervention. Typically, trident shaped central pontine hyperintense signal abnormality reveals on T2W MR images.34 The peripheral fibers (ventrolateral longitudinal fibers and corticospinal tracts) as well as the periventricular and subpial regions are typically spared (Fig 34A and B).
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35. “Horse-shoe” sign: Multiple sclerosis
The enhancement pattern in multiple sclerosis or tumefactive demyelinating lesions is not uncommonly in the form of an open ring (“horse-shoe” shaped) enhancement, with the incomplete portion of the ring facing the cerebral cortex35 (Fig 35). The enhancing segment of the ring is thought to represent the zone of active demyelination (leading edge) accordingly favoring the white matter side of the lesion. The nonenhancing central part represents a more chronic phase of demyelination. Given the size of the lesion, accompanying edema and mass effect are disproportionately less than expected. 36. “Onion-skin” sign: Balo’s ´ concentric sclerosis
Balo’s ´ concentric sclerosis presents a peculiar pattern of concentric lamellae of myelin and demyelinated layers around a central focus (“onion-skin”)36 (Fig 36). Balo’s ´ concentric sclerosis may occur as an isolated phenomenon or precede the development of multiple sclerosis. 37. “Hockey-stick” sign: Creutzfeldt-Jacob disease
“Hockey-stick” sign refers to symmetrical pulvinar and dorsomedial thalamic nuclear hyperintensity in patients with variant Creutzfeldt-Jacob disease (vCJD). This sign is highly sensitive and specific for vCJD37 (Fig 37). 38. “Water-Lily” sign: Hydatid cyst
Hydatid disease of CNS is rare and most frequently supratentorial, involving the territory of the MCA. The signal intensity of the cysts is identical to CSF unless infected. Hydatid cysts are classified into five types, and these can be determined by any imaging modality. In type 2 hydatid cyst, detachment of inner germinal layer results in a floating membrane with characteristically convex serpiginous margin on the surface of the remaining cyst, creating an appearance known as “water-lily” sign or “floating lily” sign38 (Fig 38). F. Others 39. Reverse cupping sign: Increased intracranial pressure
The globe at its junction with the optic nerve can be indented (reverse “cupping”) by the transmitted raised intracranial pressure, clinically manifested as papilledema39 (Fig 39). 40. “En coup de sabre”: Parry-Romberg syndrome/linear scleroderma
Linear scleroderma appears as an indented, vertical, colorless, line of skin on the forehead. The condition is described by the French word “en coup de sabre” or “sword stroke.” ParryRomberg syndrome, also known as progressive facial hemiatrophy, overlaps with a condition known as linear scleroderma and is a neurocutaneous syndrome. But, the relationship between the two entities is still controversial. Neurological involvement is frequently described in Parry-Romberg syndrome, including migraine, facial pain, and epilepsy. The focal linear atrophy of the skin and subcutaneous tissues can be seen on MR images40 (Fig 40).
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References 1. Adeloye A. Mesencephalic spur (beaking deformity of the tectum) in Arnold-Chiari malformation. J Neurosurg 1976;45:315320. 2. Davidson HD, Abraham R, Steiner RE. Agenesis of the corpus callosum: magnetic resonance imaging. Radiology 1985;155:371373. 3. Shen WC, Shian WJ, Chen CC, et al. MRI of Joubert’s syndrome. Eur J Radiol 1994;18:30-33. 4. Maria BL, Quisling RG, Rosainz LC, et al. Molar tooth sign in Joubert syndrome: clinical, radiologic, and pathologic significance. J Child Neurol 1999;14:368-376. 5. Akpınar E. The tram-track sign: cortical calcifications. Radiology 2004;231:515-516. 6. Poe LB, Coleman LL, Mahmud F. Congenital central nervous system anomalies. Radiographics 1989;9:801-826. 7. Shinagare AB, Patil NK, Sorte SZ. Case 144: dysplastic cerebellar gangliocytoma (Lhermitte-Duclos disease). Radiology 2009;251:298303. 8. Ghai S, Fong KW, Toi A, et al. Prenatal US and MR imaging findings of lissencephaly: review of fetal cerebral sulcal development. Radiographics 2006;26:389-405. 9. Wolfson BJ, Faerber EN, Truex RC Jr. The ‘keyhole’: a sign of herniation of a trapped fourth ventricle and other posterior fossa cysts. AJNR Am J Neuroradiol 1987;8:473-477. 10. Giroud M, Beuriat P, Becker F, et al. Dense middle cerebral artery: etiologic significance and prognosis. Rev Neurol (Paris) 1990;146:224-227. 11. Ford K, Sarwar M. Computed tomography of dural sinus thrombosis. AJNR Am J Neuroradiol 1981;2:539-543. 12. Wada R, Aviv RI, Fox AJ, et al. CT angiography ‘spot sign’ predicts hematoma expansion in acute intracerebral hemorrhage. Stroke 2007;38:1257-1262. 13. Truwit CL, Barkovich AJ, Gean-Marton A, et al. Loss of the insular ribbon: another early CT sign of acute middle cerebral artery infarction. Radiology 1990;176:801-806. 14. Han BK, Towbin RB, De Courten-Myers G, et al. Reversal sign on CT: effect of anoxic/ischemic cerebral injury in children. AJNR Am J Neuroradiol 1989;10:1191-1198. 15. Rigamonti D, Drayer BP, Johnson PC, et al. The MRI appearance of cavernous malformations (angiomas). J Neurosurg 1987;67:518524. 16. Brockmann MA, Nowak G, Reusche E, et al. Zebra sign: cerebellar bleeding pattern characteristic of cerebrospinal fluid loss. Case report. Neurosurg 2005;102:1159-1162. 17. Buonanno FS, Moody DM, Ball MR. CT scan findings in cerebral sinovenous occlusion. Neurology 1979;29:1433-1434. 18. Truwit CL. Venous angioma of the brain: history, significance, and imaging findings. AJR Am J Roentgenol 1992;159:12991307. 19. Suzuki J, Takaku A. Cerebrovascular ‘moyamoya’ disease. Disease showing abnormal net-like vessels in base of brain. Arch Neurol 1969;20:288-299. 20. Yoon HK, Shin HJ, Chang YW. ‘Ivy sign’ in childhood moyamoya disease: depiction on FLAIR and contrast-enhanced T1-weighted MR images. Radiology 2002;223:384-389. 21. Mishkin FS, Dyken ML. Increased early radionuclide activity in the nasopharyngeal area in patients with internal carotid artery obstruction: ‘hot nose’. Radiology 1970;96:77-80. 22. Wallace EW. The dural tail sign. Radiology 2004;233:56-57. 23. Campbell BA, Jhamb A, Maguire JA, et al. Meningiomas in 2009: controversies and future challenges. Am J Clin Oncol 2009;32: 73-85. 24. Rees JH, Smirniotopoulos JG, Jones RV, et al. Glioblastoma multiforme: radiologic-pathologic correlation. Radiographics 1996;16:1413-1438; quiz 1462–1463. 25. Brant WE, Helms CA. Fundamentals of Diagnostic Radiology. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2007: 134.
26. Som PM, Curtin HD. Head and Neck Imaging. 4th ed. St Louis: Mosby Year Book, 2003:1279-1280. 27. Hitoshi S, Iwata M, Yoshikawa K. Mid-brain pathology of Wilson’s disease: MRI analysis of three cases. J Neurol Neurosurg Psychiatry 1991;54:624-626. 28. Sethi KD, Adams RJ, Loring DW, et al. Hallervorden-Spatz syndrome: clinical and magnetic resonance imaging correlations. Ann Neurol 1988;24:692-694. 29. Journel H, Roussey M, Gandon Y, et al. Magnetic resonance imaging in Pelizaeus-Merzbacher disease. Neuroradiology 1987;29:403405. 30. Schrag A, Kingsley D, Phatouros C, et al. Clinical usefulness of magnetic resonance imaging in multiple system atrophy. J Neurol Neurosurg Psychiatry 1998;65:65-71. 31. Namekawa M, Takiyama Y, Honda J, et al. Adult-onset Alexander disease with typical ‘tadpole’ brainstem atrophy and unusual bilateral basal ganglia involvement: a case report and review of the literature. BMC Neurol 2010;10:21. DOI: 10.1186/14712377-10-21 32. Oba H, Yagishita A, Terada H, et al. New and reliable MRI diagnosis for progressive supranuclear palsy. Neurology 2005;64:20502055.
33. Adachi M, Kawanami T, Ohshima H, et al. Morning glory sign: a particular MR finding in progressive supranuclear palsy. Magn Reson Med Sci 2004;3:125-132. 34. Miller GM, Baker HL, Okazaki H, et al. Central pontine myelinolysis and its imitators: MR findings. Radiology 1988;168:795802. 35. He J, Grossman RI, Ge Y, et al. Enhancing patterns in multiple sclerosis: evolution and persistence. AJNR Am J Neuroradiol 2001;22:664-669. 36. Caracciolo JT, Murtagh RD, Rojiani AM, et al. Pathognomonic MR imaging findings in Balo concentric sclerosis. AJNR Am J Neuroradiol 2001;22:292-293. 37. Collie DA, Sellar RJ, Zeidler M, et al. MRI of Creutzfeldt-Jakob disease: imaging features and recommended MRI protocol. Clin Radiol 2001;56:726-739. 38. Beggs I. The radiology of hydatid disease. AJR Am J Roentgenol 1985;145:639-648. 39. Greenfield DS, Siatkowski RM, Glaser JS, et al. The cupped disc: who needs neuroimaging? Ophthalmol 1998;105:1866-1874. 40. Appenzeller S, Montenegro MA, Dertkigil SS, et al. Neuroimaging findings in scleroderma en coup de sabre. Neurology 2004;62(9):1585-1589.
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ABSTRACT We retrospectively reviewed neuroradiology database at our tertiary-care hospital to search for patients with metaphoric or descriptive signs on brain computed tomography or magnetic resonance imaging. Only patients who had clinical or pathological definitive diagnosis were included in this review.
Keywords: Brain, signs, magnetic resonance imaging, computed tomography. Acceptance: Received October 25, 2013. Accepted for publication November 23, 2013. Correspondence: Address correspondence to Rahsan Gocmen, Department of Radiology, Hacettepe University Faculty of Medicine, Sihhiye, Ankara 06100, Turkey. E-mail: [email protected] J Neuroimaging 2014;00:1-17. DOI: 10.1111/jon.12086
Introduction The history of the medicine is replete with metaphorical descriptions. Metaphors play an important role in medicine, particularly illustrative branches such as radiology, dermatology, microbiology, and pathology. Neuroradiology literature also encompasses a variety of interesting metaphoric and descriptive signs. We illustrate the characteristic 40 metaphoric or descriptive signs of a broad spectrum of conditions in neuroradiology. We retrospectively reviewed neuroradiology database from 2006 to 2013 at our tertiary-care hospital to search for patients with metaphoric/descriptive signs on brain computed tomography (CT) or magnetic resonance (MR) imaging. Only patients who had clinical or pathological definitive diagnosis were included in this review.
Findings A. Congenital Malformations
ages in patients with corpus callosum (CC) agenesis (Fig 2). The lack of supporting deep white matter fibers and associated the redirection of longitudinal callosal fibers (Probst bundles, arrows), result in bulging of the roof of the third ventricle into the interhemispheric fissure, widely separated and medially concaved frontal horns, with the frontal horns taking on a “steer or bull’s horn” appearance in the coronal view.2 3. “Bat-wing” sign: Joubert syndrome
Joubert syndrome is an autosomal recessive disorder where there is agenesis of the cerebellar vermis to varying degrees. There is an absence of decussation of the superior cerebellar peduncles (SCP) and pyramidal tracts. The absence of the vermis is responsible for a dilated, distorted, and rostrally deviated fourth ventricle; and it causes an appearance of a “bat-wing” or an umbrella3 (Fig 3A and B).
1. “Tectal beaking” sign: Chiari II malformation
“Tectal beaking” refers to the triangular (beaked) appearance of the tectum on the sagittal views in Chiari type-II (Arnold-Chiari) malformation.1 The midbrain is elongated caudally and posteriorly to overlie the midline cerebellum and the pons (Fig 1). Variable degrees of fusion of the colliculi and tectum result in a beaked tectum. 2. “Steer-horn” ventricles: Agenesis of the corpus callosum
The “steer-horn” sign refers to the abnormal shape of the frontal horns of the lateral ventricles on coronal MR im-
4. “Molar tooth” sign: Joubert syndrome
The deeper and wider interpeduncular cistern (Fig 4A; arrow) and thicker, elongated, and horizontal SCP (Fig 4B; arrows) give the shape of a “molar tooth” on MR axial images; this is one of the most consistent imaging finding in Joubert syndrome.4 Also note that a lack of “central red dot” sign (Fig 4C) corresponding to the decussating fibers of the SCP on axial colored-fractional anisotropy (FA) map image. The FA map in a normal individual shows “central red dot” sign (Fig 4D).
Copyright
◦ 2014 by the American Society of Neuroimaging C
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Fig 1. 5. “Tram-track” sign: Sturge-Weber syndrome
“The tram-track” sign is caused by cortical calcifications in Sturge-Weber syndrome.5 This sign can be observed on plain radiograph, noncontrast CT (NCCT) scans (Fig 5A). On NCCT, “tram-track” calcification is usually seen before 2 years of age. The metaphor of the tram-track which is one of the most favorite radiologic descriptions also has been described in optic nerve meningioma. The tram-track sign is most evident on contrast–enhanced CT or fat-suppressed T1-weighted MR images of the orbit. On these images, the optic nerve appears
Fig 3.
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Fig 2.
as an unenhanced central linear structure (negative defect) in relation to the surrounding enhancement in the area of the optic nerve sheath on either side (Fig 5B). It is helpful in distinguishing dural diseases from optic nerve glioma. 6. “Pancake” sign: Holoprosencephaly
The “pancake” sign refers to the appearance of the cerebral parenchyma in patients with a lobar holoprosencephaly (AH).6 AH, is characterized by a mono-ventricle, small, contiguous brain tissue that may have a cup, ball, or a pancake
Fig 4.
Fig 5.
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Fig 6.
Fig 8.
The “corduroy” appearance refers to thick cerebellar foliar pattern that consists of alternating bands on T1- and T2W imaging in Lhermitte-Duclos disease (LDD).7 The maintenance of the overall cerebellar architecture in spite of the thickened, and hyperplastic folia is responsible for this characteristic imaging appearance (Fig 7). LDD (also known as dysplastic gangliocytoma) is a rare probably hamartomatous disorder involving the cerebellum. The debate on whether it represents a neoplasm, malformation, or hamartoma, still continues. 8. “Figure-eight” : Lissencephaly
“Figure of 8,” also known as “hourglass configuration” refers to the appearance of the brain in the type I lissencephaly.8 Type I lissencephaly is a migration disorder of the gray matter, with the formation of a smooth, thick but four-layered cortex. Sylvian fissures are shallow, verticalized, and the brain takes a “figure-eight” configuration because of a narrowing at its middle portion by the Sylvian fissures (Fig 8). 9. “Key-hole” sign: Dandy–Walker syndrome
Fig 7.
configuration, fusion of the thalami, and absence of the interhemispheric fissure, cavum septum pellucidum, CC, optic tracts, and olfactory bulbi (Fig 6). 7. “Corduroy” sign: Lhermitte-Duclos syndrome (aka dysplastic gangliocytoma)
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The key-hole appearance is caused by communication between cisterna magna and dilated 4th ventricle9 (Fig 9A and B). The Dandy–Walker malformation complex refers to a group of congenital central nervous system (CNS) malformations that primarily involves the cerebellum and surrounding structures. The diagnostic nomenclature in this field is confusing, in part because this complex may be regarded as a spectrum of posterior fossa abnormalities, which includes dilatation of the fourth ventricle, varying degrees of cerebellar vermis hypoplasia or aplasia, and elevation of the transverse sinuses and torcular herophili. The key-hole shaped 4th ventricle has also been described in rhombencephalosynapsis (Fig 9C).
Fig 9.
Fig 10.
Fig 11.
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Fig 12.
Fig 13.
Fig 14.
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Fig 15.
Fig 17.
Fig 16.
Fig 18.
B. Vascular/Stroke 10. Dense middle cerebral artery (MCA): Acute thrombosis
The dense MCA sign is one of the early signs of infarct (Fig 10A–D). This is due an increase in density of its proximal segments, secondary to thrombosis.10 The corresponding sign on susceptibility-weighted imaging (SWI) has been called as “MCA-susceptibility-sign.” False-positive results may
occur, in cases with vascular calcification, focal subarachnoid hemorrhage in the Sylvian fissure, and high haematocrit. The dense artery sign can also be seen in basilar artery thrombosis. 11. “Cord” sign: Cortical venous thrombosis
The “cord” sign is characterized as increased density of the cortical or deep veins on NCCT, originated from the
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Fig 19. thrombosed material inside the affected vessel.11 Diagnosis of the venous infarct is elusive because of the wide variety of clinical and radiologic manifestations, mimicking arterial infarct or other diseases. “Cord” sign is a rare, but an invaluable clue for diagnosis of the venous thrombus (Fig 11A and B). 12. “Spot” sign: Active bleeding within hematoma
The “spot” sign refers to tiny enhancing foci on CT angiography (CTA) source images and refers to active bleeding.12 It’s been regarded as a predictor of hematoma expansion. NCCT scan demonstrates spontaneous intracerebral hematomain the right thalamus (Fig 12A). Axial maximum intensity projection view of CTA reveals that small foci of enhancement consistent with the “spot sign” (Fig 12B, arrow). Marked hematoma expansion is demonstrated on follow-up CT scans (Fig 12C).
Fig 21.
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Fig 20.
13. Insular “ribbon” sign: Acute MCA infarct
This refers to hypodensity and swelling of the insular cortex13 (Fig 13A, arrow). It is a very indicative and subtle early CT-sign of infarct in the territory of the ipsilateral MCA. Figure demonstrates normal insular ribbon appearance on the right cerebral hemisphere (Fig 13B). 14. “Reversal” sign or white cerebellum: Diffuse cerebral hypoxic/anoxic injury
The “reversal sign” represents severe anoxic-ischemic brain injury resulting in irreversible brain damage and carries a poor prognosis. CT features of the “reversal” sign are diffusely decreased density of cerebral cortical gray and white matter with a decreased or lost gray/white matter interface, or reversal
Fig 22.
Fig 23.
of the gray/white matter densities and relatively increased density of the thalami, brainstem, and cerebellum14 (Fig 14A and B).
unless there is an associated hemorrhage or multiloculated cavernoma. Blooming on gradient echo images are due to paramagnetic effect of blood degradation products.
15. “Popcorn” sign: Cavernous malformation
The cavernous malformation, also known as cavernous hemangioma or cavernoma, is an abnormal vascular lesion. It has typically “popcorn” appearance T1 bright locules of methemoglobin with a low signal intensity hemosiderin rim on T2W images15 (Fig 15). Perilesional edema or mass effect is unusual
16. “Zebra” sign: Remote cerebellar hemorrhage
This sign refers to typical, streaky bleeding pattern due to blood spreading in the cerebellar folia in patients with remote cerebellar hemorrhage (RCH)16 (Fig 16). RCH is usually benign, self-limited complication of supratentorial craniotomies. Temporal lobe resection for epilepsy, vascular
Fig 24.
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Fig 25.
Fig 26.
neurosurgery, or spinal surgery may be associated. Although the exact mechanism accounting for RCH remains unclear loss of cerebrospinal fluid due to an interventional process leading to cerebellar sagging, with a consequent occlusion of the bridging veins have been accused for.
perior sagittal sinus thrombosis. The exact mechanism for this appearance is uncertain, with possibilities including recanalization around an organizing clot, enlargement of the peri-dural small veins, thickening of the dura with increased enhancement.
17. “Empty delta” sign: Dural sinus thrombosis
The “empty delta” sign consists of a triangular area of enhancement or high attenuation with a relatively lowattenuating center (filling defect of thrombus) on contiguous axial contrast-enhanced CT17 (Fig 17). It is apparent in su-
Fig 27.
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18. “Caput medusa” sign: Developmental venous anomaly
The “caput medusa” sign is indicative of developmental venous anomaly (DVA), and is identifiable on contrast-enhanced CT and MR18 (Fig 18). DVAs correspond to a network of dilated, abnormal medullary veins with a radial distribution,
images, is a tangle of tiny vessels that look like a puff of smoke19 (Fig 19). Moyamoya, a name also used to describe this angiographic sign, comes from the Japanese meaning puff of smoke or hazy foggy appearance. 20. “Ivy” sign: Moyamoya disease
The “ivy” sign refers to tiny leptomeningeal high signal intensity along the cerebral sulci or on the brain surface in moyamoya disease on unenhanced fluid-attenuated inversion recovery (FLAIR) MR imaging20 (Fig 20). This sign initially was described for collateral vessels on contrast-enhanced T1W MR imaging. 21. “Hot nose” sign: Loss of cerebral blood flow; brain death
Fig 28. converging into a wide single drainage vein. This appearance is reminiscent of Medusa, a gorgon of Greek mythology. Angiographically, the caput medusa appearance is seen only in the venous phase. DVAs may be associated with cavernous angiomas or one of the other types of CNS vascular malformations (i.e., arteriovenous malformation). 19. “Puff of smoke” sign: Moyamoya disease
The “puff of smoke” sign, characteristic of moyamoya disease, is caused by the formation of collateral vessel networks from the progressive bilateral supraclinoid stenoses of the internal carotid arteries. This sign, seen on cerebral angiographic
“Hot nose” sign refers to early and increased radiotracer activity in the nasopharyngeal region at nuclear scintigraphy.21 The phenomenon is a result of occlusion of the internal carotid artery with flow rerouted to the nose via the external carotid artery. Note lack of flow to the cerebral hemispheres and abnormal increased nasopharyngeal activity (Fig 21; arrows). C. Tumors and Tumor-like Lesions 22. Dural “tail” sign: Meningioma
The dural “tail” sign is seen on contrast-enhanced MR images as a thickening of the enhanced dura mater that resembles a tail extending from the meningiomas22 (Fig 22). It was initially thought to result from direct invasion of the dura; however, subsequent studies demonstrated it to be a more reactive process. This sign, which had been described as highly specific for meningiomas once, can also be seen in other extra- and intraaxial tumors that involve the dura mater.
Fig 29.
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Fig 30.
Fig 31. 23. “Spoke-wheel” sign: Meningioma
The “spoke-wheel” sign refers to the typical angiographic appearance found in meningiomas. This sign corresponds to multiple small arteries radially distributed from dominant feeding artery.23 This figure demonstrates spoke-wheel within the meningioma mass on the axial T2W MR image (Fig 23). 24. “Butterfly” sign: Glioblastoma multiforme, lymphoma, tumefactive demiyelinating lesion
“Butterfly” sign is most commonly described in glioblastoma multiforme (GBM) syndrome, and refers to the symmetric wing like extensions across the midline through the CC.24 This appearance, however, is not pathognomonic of GBM (Fig 24A),
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and has also been reported in lymphoma and tumefactive demyelinating lesions (Fig 24B) which can involve CC. 25. “Soap bubble” sign: Dysembriyoblastic neuroepithelial tumor
Dysembryoplastic neuroepithelial tumor (DNET) is a benign tumor arising from the cortical or deep gray matter. DNET radiologically manifests as cortical masses that are hypointense on T1- and hyperintense on T2W images (Fig 25) without surrounding vasogenic edema. The “soap bubble” appearance and bright rim on FLAIR images are characteristic.25 Calcification and remodeling of the adjacent inner table of the skull may be seen.
Fig 32.
26. “Ice-cream” sign: Vestibular schwannoma
The schwannomas are the most common cerebellopontine angle (CPA) masses, while meningiomas are the second most common. They expand the internal auditory canal (IAC), as a matter of their size. The tumor resembles classic “ice-cream” appearance on axial imaging plane (Fig 26), while the component involving IAC and extension into the CPA cistern constitute ice-cream-cone and -scoop, respectively.26 D. Metabolic/Degenerative Disorders
Fig 33.
27. “The giant panda” sign: Wilson’s disease
This sign refers to a combination of signal intensity changes at midbrain on axial T2W MR imaging (Fig 27A). The pathologic high signal intensity of tegmentum represents white face of a panda while preserved intensity of red nuclei forms the eyes, pars reticulata the ears and superior colliculus represents the nose.27 At caudal sections, increased signal within the dorsal pons is called “giant panda cub” in patients with Wilson disease (Fig 27B).
Fig 34.
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Fig 35.
Fig 37.
Fig 36.
Fig 38.
28. “Eye of the tiger” sign: Pantothenate kinase-associated neurodegeneration (aka Hallervorden-Spatz syndrome)
tral high signal intensity is attributed to gliosis, increased water content, and neuronal loss.
This sign refers to symmetrical low signal intensity circumscribing a central region of high signal intensity in the internal globus pallidus on T2W MR images28 (Fig 28). The ring of marked hypointensity involving the globus pallidus on T2W MR images is due to excessive iron accumulation, and the cen-
29. “Tigroid pattern” or “leopard skin”: Metachromatic leukodystrophy
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Metachromatic leukodystrophy (MLD) is an autosomal recessive disorder caused by a deficiency of the lysosomal enzyme
30. “Hot cross bun” sign: Multisystem atrophy-cerebellar type
“Hot cross bun” sign represents the changes of the brainstem in the multiple system atrophy of the cerebellar type on axial T2W MR imaging.30 The name derived from a sweet spiced bun baked by the Christian church and marked with a cross on the top. The sign is characterized by a cruciform pontine hyperintensity due to selective loss of myelinated transverse pontocerebellar fibers and neurons, with preservation of the pontine tegmentum and the fibers of the corticospinal tract (Fig 30A and B). Note bilateral atrophy and increased T2 signal in the middle cerebellar peduncles. 31. “Tadpole” sign: Alexander disease
“Tadpole” sign is a quite peculiar feature: marked atrophy of the medulla oblongata and cervicothoracic cord with an intact pontine base, just like a “tadpole” on sagittal MR images31 (Fig 31A). Other imaging features of the Alexander disease are present in these patients, such as symmetrical frontoparietal hyperintense lesions (Fig 32A) and significantly increased myoinositol concentrations in white matter lesions at MR spectroscopy (TE = 30 msecond; Fig 32C).
Fig 39.
32. “Penguin” or “hummingbird” sign: Progressive supranuclear palsy
“Penguin” sign, also known as “hummingbird” sign refers to the atrophy of the midbrain tegmentum, with a relatively preserved pons on midsagittal T1W images in patients with progressive supranuclear palsy32 (Fig 32). The atrophy of the midbrain results in a profile of the brainstem in which the preserved pons forms the body of the bird, and the atrophic midbrain the head, with beak extending anteriorly toward the optic chiasm. Note preservation of medulla width which differs from the above “tadpole” sign. 33. “Morning glory” sign: Progressive supranuclear palsy
“Morning glory” sign refers to peculiar atrophy of the midbrain characterized by a concavity of the lateral margin of its tegmentum on the axial images.33 Also, note the marked increase in signal intensity of the periaqueductal gray region (Fig 33). E. Infection and Demyelinating Disease 34. “Trident” sign: Central pontine myelinolysis
Fig 40. arylsulfatase. The diminished activity of arylsulfatase A enzyme accounts for failure of myelin breakdown and reutilization, thus resulting in dysmyelination. On T2W MR imaging, MLD manifests as symmetric confluent areas of high signal intensity in the periventricular white matter typically sparing the subcortical U fibers during the early stages.29 The sparing of the perivascular white matter within the centrum semiovale is responsible for the characteristic “leopard skin” (Fig 29A) and “tigroid” (Fig 29B) pattern.
Central pontine myelinolysis (CPM), also known as osmotic demyelination, is an acute demyelinating condition of the brainstem and is a recognized complication of the rapid correction of chronic hyponatremia. Symptoms of CPM include tetraplegia, pseudobulbar palsy, and acute changes in mental status leading to coma or death without intervention. Typically, trident shaped central pontine hyperintense signal abnormality reveals on T2W MR images.34 The peripheral fibers (ventrolateral longitudinal fibers and corticospinal tracts) as well as the periventricular and subpial regions are typically spared (Fig 34A and B).
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35. “Horse-shoe” sign: Multiple sclerosis
The enhancement pattern in multiple sclerosis or tumefactive demyelinating lesions is not uncommonly in the form of an open ring (“horse-shoe” shaped) enhancement, with the incomplete portion of the ring facing the cerebral cortex35 (Fig 35). The enhancing segment of the ring is thought to represent the zone of active demyelination (leading edge) accordingly favoring the white matter side of the lesion. The nonenhancing central part represents a more chronic phase of demyelination. Given the size of the lesion, accompanying edema and mass effect are disproportionately less than expected. 36. “Onion-skin” sign: Balo’s ´ concentric sclerosis
Balo’s ´ concentric sclerosis presents a peculiar pattern of concentric lamellae of myelin and demyelinated layers around a central focus (“onion-skin”)36 (Fig 36). Balo’s ´ concentric sclerosis may occur as an isolated phenomenon or precede the development of multiple sclerosis. 37. “Hockey-stick” sign: Creutzfeldt-Jacob disease
“Hockey-stick” sign refers to symmetrical pulvinar and dorsomedial thalamic nuclear hyperintensity in patients with variant Creutzfeldt-Jacob disease (vCJD). This sign is highly sensitive and specific for vCJD37 (Fig 37). 38. “Water-Lily” sign: Hydatid cyst
Hydatid disease of CNS is rare and most frequently supratentorial, involving the territory of the MCA. The signal intensity of the cysts is identical to CSF unless infected. Hydatid cysts are classified into five types, and these can be determined by any imaging modality. In type 2 hydatid cyst, detachment of inner germinal layer results in a floating membrane with characteristically convex serpiginous margin on the surface of the remaining cyst, creating an appearance known as “water-lily” sign or “floating lily” sign38 (Fig 38). F. Others 39. Reverse cupping sign: Increased intracranial pressure
The globe at its junction with the optic nerve can be indented (reverse “cupping”) by the transmitted raised intracranial pressure, clinically manifested as papilledema39 (Fig 39). 40. “En coup de sabre”: Parry-Romberg syndrome/linear scleroderma
Linear scleroderma appears as an indented, vertical, colorless, line of skin on the forehead. The condition is described by the French word “en coup de sabre” or “sword stroke.” ParryRomberg syndrome, also known as progressive facial hemiatrophy, overlaps with a condition known as linear scleroderma and is a neurocutaneous syndrome. But, the relationship between the two entities is still controversial. Neurological involvement is frequently described in Parry-Romberg syndrome, including migraine, facial pain, and epilepsy. The focal linear atrophy of the skin and subcutaneous tissues can be seen on MR images40 (Fig 40).
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