This document describes several classical radiological signs seen on various imaging modalities like CT, MRI, ultrasound and X-ray. It provides images and descriptions of signs such as the "ice cream cone sign" seen on CT of the temporal bone, "CT reversal sign" seen in diffuse cerebral anoxia, "Mount Fuji sign" seen in tension pneumocephalus on CT, and "lemon sign" seen in spina bifida on ultrasound. Many other signs seen in different neurological conditions are also described along with example images, including "pancake brain sign", "molar tooth sign", "figure eight sign", and "tram track sign".

1. Radiological Classical Signs and appearances in Neuroradiology.
Dr/ ABD ALLAH NAZEER. MD.

2. Ice-cream cone sign
It reflects normal appearance of
incudomalleolar joint formed by malleolar
head and body of the incus on axial
computed tomography (CT) sections.
Anatomical identification of this anatomic
structure is important in terms of ossicular
luxation especially in trauma cases. The
space between the ice-cream cone and the
scutum is called Prussak’s space

3. High resolution, axial CT image demonstrating the “ice-cream sign” of the temporal bone
(white arrow). The sign represents the typical appearance of the malleoincudal joint.

4. ICE CREAM CONE SIGN. Axial temporal bone CT. Picture and schematic drawing.

5. CT reversal sign
The reversal sign is associated with diffuse anoxic-
ischemic brain damage and almost always observed
in children. This sign is characterized by a relative
reversal of the attenuation between supra- and
infratentorial structures. The grey-white matter
distinction is lost and decreased, and there is a
diffuse decrease in density in the cerebral grey and
white matter. Thalami, brainstem, and cerebellum
have a relatively increased density. It is closely
related to child abuse, especially when
accompanying intracranial bleeding.

6. CT reversal sign” is observed due to diffuse cerebral anoxia
in non-contrasted CT examination.

7. Mount Fuji sign
This sign is observed in bilateral subdural
tension pneumocephalus. These air
accumulations lead to compression in the
frontal lobes and take a form of Mount Fuji
on axial CT sections. It is most commonly
seen after surgical decompression of chronic
subdural hematoma. However, it may also be
observed following a head trauma, otogenic
infections, nitrous oxide anesthesia, and
diving

8. ”Mount Fuji sign” due to tension pneumocephalus is observed in
axial CT sections (parenchymal and bone window, white arrows)

9. Lemon sign
The lemon sign is useful in identification of spina
bifida and is commonly associated with
hydrocephalus and Chiari II malformation. Loss of
normal convex contour of the frontal bones in
transverse fetal sonogram obtained at biparietal
diameter. It has a high sensitivity and specificity in
high-risk patients before the 24th gestational week.
However, it is not specific for spina bifida and may
be detected in encephalocele, Dandy-Walker
malformation, thanatophoric dysplasia, cystic
hygroma, corpus callosum agenesis,
hydronephrosis, and umbilical vein varices

10. ”Lemon sign” is seen in the frontal bones in a fetus with myeloschisis, as detected
in an obstetrical US performed at the 20th week of gestation (white arrows).

11. Axial sonogram of a fetal head demonstrating the lemon sign. Schematic drawing and picture.

12. Pancake brain sign
This sign defines the appearance of abnormal
brain tissue in cases with alobar
holoprosencephaly. Holoprosencephaly is an
anomaly caused by a prosencephalic division
defect and characterized by varying degrees of
fusion of cerebellar hemispheres,
diencephalon, basal ganglia, and thalami. The
pancake brain sign is formed by fusion of
cerebral hemispheres associated with the
presence of typical monoventricle at the center

13. ”Pancake brain appearance” formed by monoventricle cavity and cerebral hemispheric
fusion is seen in T1-weighted MR image in a case with alobar holoprozencephaly.

14. Molar tooth sign
Joubert syndrome is an autosomal recessive
disorder characterized by abnormal eye
movements, nystagmus, and difficulty in
following mobile objects with eyes, apnea-
tachypnea episodes, and motor retardation.
Molar tooth sign represents abnormal antero-
posterior orientation of superior cerebellar
peduncles in a way similar to stems of a molar
tooth on axial CT or magnetic resonance (MR)
images. It is mainly observed in patients with
Joubert syndrome.

15. Molar tooth sign” (star) at the level of pons and superior cerebellar peduncles coursing parallel to
each other (white arrows) is seen in a T1-weighted MR section in a case with Joubert syndrome.

16. Joubert's syndrome - The 'Molar Tooth'

17. Figure eight sign
Lissencephaly is a disorder caused by defective
neuronal migration between the 8–14th
gestational week and characterized by a lack of
development of gyri and sulci. Lissencephaly is
classified into two subgroups: complete (type 1 –
agyria) or partial (type 2 – pachygyria). Type 1
lissencephaly is characterized by shallow sylvian
fissures that are vertically oriented. In this type of
lissencephaly, brain takes on an hour-glass or
figure-8 appearance due to compression at the
middle part by sylvian fissures on axial imaging.

18. An appearance similar to “figure eight” due to lissencephaly in the axial plane on CT examination.

20. Face of the giant panda sign
This sign was first described by Hitoshi et al. in
Wilson’s disease in 1991. It consists of high
signal intensity in the tegmentum except for the
red nucleus, preservation of signal intensity at
the lateral portion of the pars reticulata of the
substantia nigra, and hypointensity of the
superior colliculus. The real pathology
responsible for this appearance is the
paramagnetic effect of the accumulation of
heavy metals such as iron and copper in
affected sites.

21. A “giant panda face” is observed in a T2-weighted axial
MR image in a case with Wilson syndrome.

22. Radial band sign
Radial bands are linear or curvilinear areas with an
abnormal signal intensity extending from the
periventricular region to the subcortical region,
that are best observed on T2-weighted (T2W) and
especially FLAIR MR images. It is believed that
radial band sign is indicative of abnormal
migration of dysplastic stem cells during the course
of radial glial-neuronal unit in patients with
tuberous sclerosis complex. Radial bands are hypo-
/isointense on T1-weighted images and
hyperintense on T2W and FLAIR images.

23. Hyperintense radial bands (black arrow) extending linearly at the level of the right cerebral hemisphere and a
cortical tuber (short white arrow) located at the left parietal lobe in an axial FLAIR MR image in a case with
tuberous sclerosis complex. In addition, MRI showing a subependymal nodule (thin black arrow).

24. String sign/Tigroid (Leopard skin) appearance
This sign is characterized by multiple dark spots
or stripes (spared perivascular white matter) of
normal white matter intensity scattered within
the bright demyelinated periventricular white
matter on T2W images. Tigroid appearance of
the white mater has been found in some cases
with Pelizaeus-Merzbacher disease and
metachromatic leukodystrophy. However, it has
been recently reported that it may be observed in
cases with lissencephaly accompanied by
cerebellar hypoplasia.

25. STRIPE SIGN/TIGROID PATTERN. Linear hypointensities radiating from the
ventricular margins within hyperintense periventricular white matter and the
centrum semiovale on T2W MRI axial image. Schematic drawings and pictures.

26. A “tigroid appearance” is observed at periventricular white matter in axial T2-
weighted MR sections in a 2-year-old girl with metachromatic leukodystrophy.

27. Open circle sign
The open ring sign is a relatively specific sign
for demyelination, helpful in distinguishing
between ring enhancing lesions. It is observed
in patients with multiple sclerosis. It is observed
as a lesion showing contrast effect as a circle
that incompletely encircles a demyelinated
plaque. The lesion is a high-intensity one on
T2W images and it may be difficult to
distinguish from an abscess or astrocytoma in
this form.

28. Post-contrast T1-weighted MR image showing an incomplete ring
lesion enhancing in the right parietal region (black arrow).

29. Light bulb sign
Diffusion-weighted (DW) MR imaging is the method that
can delineate ischemic lesions in the brain at the earliest
stage. With the help of this method, this lesion can be
demonstrated after the onset of the event. The ischemic
area shines like a light bulb at this stage (it appears darker
on ADC images). This area forms the core of the infarcted
region. The brightness diminishes by the 2nd–3rd month. In
this way, acute and chronic infracts can be distinguished
or acute lesions can be defined in patients with multiple
lesions of varying age. The marked increase in DWI signal
in areas of acute ischemia, relative to unaffected brain, is
typically so striking that this finding has been referred to
as the “light bulb sign” of acute stroke.

30. The b=1000 s/mm2 DWI showing an acute infarct as “light bulb” bright.

31. Keyhole sign
The posterior fossa dimensions are normal in
Dandy-Walker variants. There is a mild
vermian hypoplasia and thus the vallecula
becomes widened between the cerebellar
hemispheres under the vermis. The fourth
ventricle and cisterna magna communicate
with each other through this wide vallecula.
This appearance on axial CT and MR images
is called “keyhole sign

32. Axial non-contrast CT image showing typical “key-hole” appearance
of cisterna magna communicating with a dilated 4th ventricle (star).

33. Dawson finger
It is detected on MR examination in multiple
sclerosis. Demyelinating plaques are
observed as focal signal areas on proton
density and T2W MR images. These plaques
are round or ovoid lesions limited
particularly to the periventricular region. The
appearance of periventricularly located
ovoid lesions in the extended form along the
ventricle is called Dawson finger.

34. Axial and parasagittal FLAIR MR images demonstrating multiple sclerosis
plaques extending up through the corpus callosum (thin black arrows).

35. Cortical vein sign
This was first described in MRI and also reported
later on US and CT. It is used to differentiate
extra-axial subarachnoid and subdural effusions
from each other. On both CT and MRI, bridging
veins extend from the cortical surface to the
arachnoid. Appearance of bridging veins
coursing in that manner in the extra-axial fluid
is called a positive cortical vein sign and
indicates that the fluid is located
subarachnoidally. The fluid is located subdurally
when these veins are invisible.

36. Post-contrast axial CT image showing the cortical veins (black arrows).

37. Caput medusa sign
The most common vascular malformation in the bran is
venous angiomas. They are most commonly observed in
the frontal lobe and the posterior fossa. It has been
suggested that they stem from a pause during brain
development, i.e. when the arterial system completes its
development but the venous system is not fully developed
yet. The caput medusa sign, also known as a palm tree
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 MRI when contrast is administered

38. Contrast-enhanced T1-weighted axial MR image confirming converging tubular structures that
represent a venous angioma (white arrow) in the medial aspect of the right cerebellar lobe.

39. Angel wing sign
Chiari type II is the most common type of Chiari
malformation. It is also known as Arnold-Chiari
malformation. In 90% of cases there is also
myelomeningocele, hydrocephalus, and corpus
callosum agenesis. In these cases, prepontine
migration of the cerebellum at the level of the
middle cerebellar peduncle gives the brainstem
an angel wing appearance on axial MR images

40. Axial T2-weighted MR image showing an “angel wing appearance” in the brainstem (black arrows).

41. Worm bag sign
Arteriovenous malformations are space-
occupying lesions formed by conglomerated
large vessels. There may sometimes be a very
small amount of brain tissue between the
vessels in intracranial arteriovenous
malformations. There is no brain tissue at all
in some cases. Thus, such an appearance of
large vessels resembles clustered worms and
is called a worm bag sign

42. Sagittal T2-weigted MRI images showing a nidus of compact vessel with a typical
appearance of “bag of black worms” in the left frontal region (white arrows).

43. Tectal beaking
Chiari type II is the most common type of Chiari
malformation. It is also known as Arnold-Chiari
malformation. In 90% of cases there is also
myelomeningocele, hydrocephalus, and corpus
callosum agenesis. Variable degrees of fusion of
the colliculi and tectum result in prominent
beaking and inferior displacement of the tectal
plate. In these cases, the appearance of the
pointed tectum is called tectal beaking

44. Sagittal T1-weighted MRI demonstrating a small posterior fossa with a low-lying tentorial attachment
posteriorly. The tectum is beaked (white arrow) and partial corpus callosum agenesis is present.

45. Double cortex appearance
Because of the early arrest of neuronal
migration, a symmetric circumferential band
of heterotopic grey matter is separated from
the overlying cortex by a thin band of white
matter. On MRI, the brain appears to have a
“double cortex” appearance. The condition is
quite rare, found predominantly in females,
and is occasionally associated with an X-
linked dominant inheritance pattern.

46. Axial T2-weighted MR image showing four layers consisting of cortex, thin
outer white matter, diffuse subcortical heterotopia, and inner white matter
around the lateral ventricles, giving the appearance of a “double cortex”

47. Banana cerebellum sign
The banana cerebellum sign is one of the many notable
fruit-inspired signs, such as the “lemon sign”. In neural
tube defects, folding of the cerebellum around the
posterior brain stem due to inferior traction of the spinal
cord causes the cerebellum to take the form of a banana.
It has been reported that it may be present in 57% of
fetuses with neural tube defect. In fetal hydrocephalus, a
cerebellar deformation is observed in conjunction with
ventriculomegaly and deletion of cisterna magna. In these
cases, the cerebellum loses its normal central convexity
and becomes compressed parallelly to the occipital bone,
resembling a banana.

48. Transverse US image showing small posterior fossa and banana-shaped cerebellum (“banana sign”) (black arrows.

49. Viking helmet appearance
The “Viking helmet” appearance refers to the
lateral ventricles in the coronal projection in
patients with dysgenesis of the corpus
callosum. The cingulate gyrus is everted into
narrowed and elongated frontal horns.
Dysgenesis of the corpus callosum may be
complete (agenesis) or partial and represents
an “in utero” developmental anomaly.

50. Coronal view of MRI head of the patient demonstrating the lateral ventricles forming a “Viking
helmet” appearance (white arrows) due to the absence of corpus callosum (black arrow).

51. The Tram-Track sign
The tram-track sign is seen on skull radiographs as
gyriform, curvilinear, parallel opacities that have the
appearance of calcifications. A similar appearance can be
seen on CTs. Sturge-Weber syndrome is a rare
neurocutaneous syndrome that includes a facial port-wine
stain and is associated with leptomeningeal angiomatosis.
Weber demonstrated the characteristic gyriform
intracranial calcifications. Calcifications are often gyriform
and curvilinear and are most common in the parietal and
occipital lobes. Calcifications can be more extensive but
with frontal lobe and/or bilateral involvement. CT scans
show calcifications in the areas of atrophy.

52. Lateral skull radiograph in a patient with Sturge-Weber syndrome showing parallel cortical
calcifications (thin-white arrows). Contrast-enhanced axial T1-weighted MRI showing
gyriform contrast enhancement in the right cerebral hemisphere (white arrows). There is
brain atrophy on the right side. The cranial vault is asymmetric as secondary to brain atrophy.

53. Diamond-shaped fourth ventricle
This appearance is seen in rhombencephalosynapsis.
Rhombencephalosynapsis is a rare condition with
most cases found in newborns and infants.
Morphological findings are predominantly
characterized by fusion of the cerebellar
hemispheres and absence of the vermis, often
accompanied by supratentorial anomalies. The size
of the fourth ventricle is variable and in its axial
plane it usually has a “keyhole or diamond shape”.
This appearance is a result of dorsal and rostral
convergence of the dentate nuclei, cerebellar
peduncles and inferior colliculi

54. Axial T2-weighted MRI at the level of the posterior fossa showing antero-posterior
elongation of the fourth ventricle giving it a “diamond shaped” appearance (arrows).

55. 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 the vermis with apposed
cerebellar hemispheres give the fourth
ventricle an appearance reminiscent of a
bat with its wings outstretched. It is best
demonstrated in axial imaging and could be
easily missed in sagittal and coronal images

56. Axial T2-weighted MRI image at the level of the pontomedullary junction
demonstrating the 4th ventricle that is shaped like a “bat wing” (arrow). In
addition, axial T2-weighted MR image showing molar tooth sign (arrow).

57. Bat wing appearance of sylvian fissures
Glutaric aciduria type 1 (GA-1) is an autosomal
recessive inborn error of lysine, hydroxylysine
and tryptophan metabolism that results from a
deficiency of glutaryl-CoA dehydrogenase. The
most striking finding on brain imaging is the
presence of very wide CSF spaces anterior to the
temporal lobes and within the sylvian fissures
(giving a “bat wing” appearance). Widening of
the sylvian fissures is a very characteristic
finding in glutaric aciduria type I

58. Axial T1-weighted and T2-weighted images demonstrating widened
sylvian fissures producing “bat-wings” appearance (arrows and stars).

59. Frog eye appearance
Anencephaly is the most severe form of cranial
neural tube defects (NTD) and is characterized by
the absence of cortical tissue (although the
brainstem and the cerebellum may be present) or
cranial vault. Morphological spectrum within
anencephaly ranges from holocrania (severest
form) to merocrania (mildest form). Anencephaly
may be radiologically detectable as early as at 11
weeks. A “frog eye” appearance may be seen in
the coronal plane of US or MR images due to an
absent cranial bone or brain, and bulging orbits

60. Fetal MR images demonstrating absent cranial bone/brain and
bulging orbits (arrows). In addition, polyhydramnios is seen (star).

61. Boxcar ventricle sign
Huntington’s disease is an autosomal dominant
neurodegenerative disease, especially common in
young adults. It has a course characterized by
cognitive, behavioral, and muscle coordination
disorders. In these cases, there may be an atrophy
in basal ganglia, particularly in the caudate nucleus.
Consequently, a widening may be seen in the
frontal horns of the lateral ventricle. This particular
appearance of frontal horns on multiplanar MR
sections is called boxcar ventricle sign

62. Axial T2-weighted MR image showing bilateral atrophy of caudate nuclei and compensatory
dilatation of lateral ventricles, a finding known as “boxcar ventricle” (black arrow).

63. "Cord sign" in cerebral venous thrombosis
Cerebral venous thrombosis (CVT) is a rare entity, with variable clinical
presentations. Seventy-five percent of the CVT occur in young women,
between 20 and 40 years of age, with the superior sagittal sinus (SSS)
being most frequently affected (62% of cases). Such increased incidence
can be explained by pregnancy, puberty and use of oral contraceptives.
The diagnosis can be achieved by means of CT (the most readily
available), magnetic resonance imaging (MRI) (the method of choice)
or by conventional angiography (CA) (the most invasive method). In
20% of cases, CT scans are normal. CVT findings can be classified in
direct and indirect. The cord sign and the empty delta sign are direct
signs of CVT. Indirect signs include: edema, infarction and hemorrhage.
The cord sign is characterized as increased density of the sinuses or of
the cortical or deep veins, originated from the thrombosed material
inside the affected vessel. The cord sign is most frequently identified
within two weeks after the first symptoms onset. With time, the
thrombus becomes isodense and subsequently, hypodense.

65. "Empty delta sign" in venous sinuses thrombosis
The empty delta sign may occur in cases of CVT,
characteristically involving the SSS. On contrast-enhanced
CT/MRI, the sign is characterized by a non-enhancing
central triangular shaped area (the thrombus itself),
limited by enhancing dura mater. Numerous factors may
lead to CVT, as follows: inflammatory processes, infection,
fibrosis of the venous sinuses walls, direct tumoral
compression or/and extension, and hypercoagulable
states. The empty delta sign is usually not identified at the
first week (the material is isodense) as well as in chronic
cases (more than two months), due to thrombus
recanalization.

66. EMPTY DELTA SIGN. Note empty triangle on contrast-enhanced CT
of the brain (thrombus in the dural sinus). Schematic drawing.

68. "Arrow sign" in ruptured middle cerebral artery aneurysm
In ruptured aneurysms the pattern of
distribution of subarachnoid hemorrhage can
indicate its most likely location. In cases of
bifurcation middle cerebral artery (MCA)
aneurismal rupture the bleed may present
the shape of an arrow, with the shaft and the
tip representing blood in the horizontal
segment of the Sylvian fissure and in the
frontotemporal opercular area, respectively

70. "Dense artery sign" in acute middle cerebral artery infarction
The dense MCA sign is one of the early signs of
infarct. This is due an increase in density of its
proximal segments, secondary to thrombosis.
False-positive results may occur, particularly in
cases of parietal calcification. It is important to
observe that the distal branches of the MCAs rarely
present parietal calcifications. Focal subarachnoid
hemorrhage may simulate an abnormally dense
MCA especially when located at the Sylvian fissure
and constitute an additional cause for false
positive results.

72. "Dot sign" in acute middle cerebral artery infarction
The dot sign is one of the early signs of acute
infarction and corresponds to a punctate
hyperdensity in the Sylvian fissure. The signal
represents thrombosis in the M2 and M3 segments
of the MCA on plain CT scans. The presence of a
thrombus/clot within the vessel alters and
increases its density. The dot sign has a high
specificity and high positive predictive value, but
has low sensitivity.

74. "Hot nose sign" at brain death
The hot nose sign can be seen in cases of brain
death and it is defined by the presence of early and
increased radiotracer activity in the
nasopharyngeal region. It may also be seen as an
intense blush (hyperemia) at CA examinations. The
phenomenon is a result of a reduced blood flow in
the internal carotid artery and increased flow in
the external carotid branches. Such signal is not
exclusive of brain death and may be found in
different situations that lead to intracranial flow
reduction in one or both internal carotid arteries

76. "Caput medusae sign" in developmental venous anomaly
The caput medusae sign is indicative of developmental
venous anomaly (DVA), and is identifiable at CA, CT and
MRI. DVAs correspond to a network of dilated, abnormal
medullary veins with radial distribution, converging into a
dominant, calibrous transparenchymal vein, which may
drain into a cortical vein, dural sinuses or into the deep
venous system. DVAs are the most frequent intracranial
vascular abnormalities, which are associated with
cavernomas in around 30% of cases. Despite being
considered incidental findings, in some cases these may
lead to intracranial hemorrhage, thrombosis and venous
infarction(11). Hemorrhages secondary to DVA are rarely
found, with an annual risk of 0.7%

78. "Spoke wheel sign" in meningioma
The spoke wheel sign refers to the typical
angiographic appearance found in meningiomas. This
sign corresponds to multiple small arteries radially
distributed from a dominant feeding artery.
Meningiomas are the most common primary
intracranial tumors in adults. They are extra-axial,
slow-growing, well-vascularized lesions with a benign
behavior (grade I, according to the World Health
Organization). Another remarkable and very common
characteristic of meningiomas is the presence of a
dural tail and, in 25% of cases, hyperostosis of the
adjacent bone

80. "Onion skin sign" in Baló's concentric sclerosis
The onion skin sign is considered pathognomonic for Baló's
concentric sclerosis(14). According to the first reports on such
disorder, most patients had an unfavorable history with progression
either to death or disability. Recent cases however, have presented
a less dramatic course. Baló's concentric sclerosis may occur as an
isolated phenomenon or precede the development of multiple
sclerosis. The lesions present a peculiar pattern of concentric
lamellae of demyelination alternated with lamellae of myelinating
or remyelinating white matter. Such lesions are most frequently
found in the frontal lobes, but may be seen in the whole neuroaxis.
Magnetic resonance imaging (MRI) is the best method for the
disease diagnosis and follow-up. In spite of the high sensitivity of
T2-weighted images to demonstrate demyelinating lesions, the
concentric rings are better identified on T1-weighted images. The
enhancement following contrast administration is variable and
probably represents active areas of demyelination

82. "Eccentric target sign" in toxoplasmosis
The eccentric or asymmetrical target sign is
highly suggestive of central nervous system
toxoplasmosis. The sign represents a ring
enhancing abscess associated with an
enhancing mural nodule. This finding is highly
specific, but has low sensitivity, being found in
approximately 30% of cases. The pathological
correlation of such sign is not completely
understood, but it is believed to represent
internal folds and invaginations of the abscess
walls

84. "Salt and pepper sign" in paraganglioma
The appearance of salt and pepper is a highly
sensitive and specific sign for head and neck
paragangliomas. On T2weighted images, the salt-
like appearance can be explained by the tumor
matrix that appears hyperintense due to the
presence of slow intratumor flow and hemorrhage
and, on post-contrast T1-weighted images, by the
presence of avid enhancement. The pepper-like
appearance, can be explained in both on T1- and
T2-weighted images by the presence of flow-voids
of small vessels within these masses

85. SALT AND PEPPER SIGN. Axial MRI demonstrates the salt and pepper
appearance due to the hypervascularity of this right mass (paraganglioma).

87. "Pancake brain sign" in alobar holoprosencephaly
Pancake brain sign represents the appearance of the
cerebral parenchyma in case of alobar holoprosencephaly.
Holoprosencephaly is a malformation caused by a
prosencephalic cleavage defect. Basically,
holoprosencephalies are categorized into three major
groups as follows: lobar holoprosencephaly, semilobar
holoprosencephaly and alobar holoprosencephaly. Alobar
holoprosencephaly is the most severe form of this
malformation and presents a single ventricular cavity,
fusion of frontal lobes, corpus callosum dysgenesis,
alteration of the third ventricle, olfactory bulb and tracts,
absence of interhemispheric fissure, besides fused thalami
and basal ganglia.

89. "Hot cross bun sign" in C-type multiple systems atrophy
The hot cross bun sign can be observed in multiple systems atrophy type C. Such sign is
characterized by a cruciform pontine hyperintensity due to selective loss of neurons of the
transverse pontocerebellar fibers, with preservation of the pontine tegmentum and of the
fibers of the corticospinal tract. Multiple systems atrophy is a neurodegenerative disorder
with varying degrees of involvement of the basal ganglia and the olivopontocerebellar
complex.

90. The "face of the giant panda" sign in Wilson's disease
The face of the giant panda pattern may be
present in Wilson's disease. Such disease is
characterized by hepatocellular degeneration
caused by a genetic disorder of the copper
metabolism with its consequential accumulation in
tissues, particularly liver and brain. On MRI
T2weighted sequences, one can observe
hyperintensity in the pontine tegmentum,
hypointensity of the periaqueductal gray matter
and partially preserved signal in the red nuclei, in
the lateral aspect of the substantia nigra pars
reticulata and of the upper colliculus

92. "High heel foot print sign" in the skull base
The high heel foot print sign is useful in the
understanding of the intricate anatomy of the skull base
and represent two relevant foramina. The anterior
aspect of the high heel footprint represents the foramen
ovale (FO), and the posterior aspect (the heel itself) the
foramen spinosum (FS). The mandibular nerve, one of
the three branches of the trigeminal nerve, is the main
FO component(1). Also, the otic ganglion, the accessory
meningeal artery, the lesser petrosal nerve and the
emissary veins are found in this foramen. The middle
meningeal artery is in the FS, and the absence of such
artery is related to the persistent stapedial artery

94. "Dural tail sign" in meningiomas
Dural tail corresponds to a thickened and
abnormally enhancing segment of dura mater
adjacent to a lesion whose shape is similar to a tail.
Dural tail signs, which had been described as highly
specific for meningiomas, can also be seen in other
pathologies such as extra- and intra-axial tumors. It
may correspond to isolated vascular changes, tumor
invasion, adjacent non-continuous tumor growth,
and tumor like micronodules. The dural tail sign is
poorly specific for meningiomas, but presents good
sensitivity, ranging from 50% and 80%

96. DURAL TAIL. Coronal T1-WI MR shows enhancement of the dura
mater in continuity with a mass. Meningioma (arrows).

98. "Martini glass sign" in persistent hyperplastic primary vitreous
Persistent hyperplastic primary vitreous (PHPV) is
characterized by the presence of congenital embryonic
remnants of hyaline vessels. The primary vitreous is supplied
by the embryonal hyaloid circulation, which regresses at birth.
In the posterior form of PHPV (the most common) a connective
fibrovascular tissue is seen attached to the lens, connecting
laterally to abnormally elongated ciliary process. At MRI a
retrolental soft tissue and vascular mass is observed in
association with a central, low-signal linear image
corresponding to the remnant hyaloid vasculature that
connects the crystalline lens to the optic nerve head,
resembling the image of a martini glass. Associatedly, the
vitreous may present high signal intensity because of
hemorrhage, besides the presence of a small ocular globe

100. "Tram-track sign" in optic nerve sheath meningioma
Optic nerve sheath meningiomas correspond to approximately two
thirds of the primary tumors in the optic nerve-sheath complex,
and are most frequently found in women between their third and
fifth decade of life. The tram-track sign is better visualized in the
axial plane of enhanced CT or MRI, and corresponds to a central
linear hypodensity/hypointensity (optic nerve) delimitated by the
contrast uptake of the optic nerve sheath at each of the sides
affected by the meningioma itself. The tram-track sign is extremely
useful in the differentiation between optic nerve sheath
meningiomas and optic nerve gliomas. The optic nerve may be
thickened and infiltrated by the glioma, but its sheath generally
does not demonstrate contrast uptake. The tram-track pattern, in
spite of being a characteristic sign, is not specific of optic nerve
sheath meningiomas, and may occur in orbit pseudotumors,
perioptic neuritis, sarcoidosis, leukemia and lymphoma.

101. OPTIC NERVE TRAM-TRACK SIGN. Contrast-enhanced CT scan and MRI images demonstrate
tram-track sign (two enhancing areas of tumor separated from each other by the negative
defect of the optic nerve)in two different cases of optic nerve sheath meningioma.

103. "Boxcar ventricle sign" in Huntington's disease
The boxcar ventricle sign represents the prominent
aspect of the lateral ventricles observed in the
coronal plane in cases of Huntington's disease,
secondary to atrophy of the basal nuclei,
particularly the caudate nuclei. Huntington's
disease is an autosomal dominant
neurodegenerative disease, which affects
particularly young adult individuals. Huntington's
disease causes muscles discoordination and
cognitive and behavioral alterations. The finding
of ventricular dilatation, as well as basal ganglia
atrophy, is very sensitive, but poorly specific

105. "Empty orbit sign" in neurofibromatosis type 1
Neurofibromatosis type 1 is an autosomal
dominant disease with variable presentation, with
cerebral and spinal changes seen in one third of
the patients. Among the possible alterations, café-
au-lait spots, Lisch nodules, plexiform fibromas and
optic nerve gliomas are highlighted. The empty
orbit sign represents the appearance of the orbit
on plain films of the skull and on CT scan because
of the lack of the innominate line due to dysplasia
of the greater wing of the sphenoid, shortening of
the lateral wall of the orbit and flattening of the
orbital angle.

107. "En coup de sabre" sign in localized scleroderma
Localized scleroderma is characterized by the presence of
sclerotic lesions on the skin and subcutaneous tissues. This is
different from systemic sclerosis because of the absence of
significant systemic involvement; and generally presents a
better prog-nosis(29). Localized scleroderma invariably affects
the head, presenting as a linear, usually frontoparietal lesion
(scleroderma "en coup de sabre“), with progressive facial
hemiatrophy or Parry-Romberg syndrome where the atrophy
extends beyond the skin to involve the subcutaneous cellular
tissue, muscles and bones. Abnormal MRI findings are observed
in 90% of cases and include hyperintensity on T2weighted
images of the corpus callosum, subcortical regions, deep gray
matter and brainstem; and most of times are ipsilateral. Focal
atrophy that is the main dermatological finding may also be
observed in the cerebral parenchyma.

109. Medusa head sign
The medusa head sign is seen in a developmental
venous anomaly (DVA), where multiple tributaries
arranged in a radial fashion drain into a larger vein.
This sign is best seen on gadolinium-enhanced T1W
images. DVAs are usually located in the juxtacortical
and periventricular regions and are commonly seen in
the frontal and parietal lobes and in the brachium
pontis. DVA is considered a non pathologic variation of
venous drainage and, by itself, is usually not of any
clinical significance. However, it can occur in
association with a cavernoma ; it is seen in
approximately 25–30% of cavernomas

110. Medusa head sign. Postcontrast axial T1W MRI image of the brain (A) shows a developmental
venous anomaly (arrow), with multiple, small, radiating veins forming a ‘Medusa head’ in the left
cerebellar hemisphere. Postcontrast axial T1W MRI image of the supratentorial brain (B) shows a
large developmental venous anomaly with multiple radiating veins (arrows) draining into it.
Postcontrast axial T1W image of the brain (C) shows a large developmental venous anomaly and
a round hyperintense lesion with a dark rim (arrow), suggestive of a cavernoma, anterior to it

111. MEDUSA HEAD SIGN. MR shows venous malformation. Multiple
tributaries arranged in a radial fashion drain into a larger vein (arrows).

112. Contrast-enhanced T1-weighted axial MR image confirming converging tubular
structures that represent a venous angioma in medial aspect of right cerebellar lobe.

113. Moya moya appearance
Moya moya is a Japanese term that means ‘puff of smoke.’ It represents
the angiographic appearance of basal telangiectasias, which consist of
dilated collateral branches of the lenticulostriate and thalamostriate
arteries. It is usually seen in the anterior circulation in association with
internal carotid artery stenosis. When the moya moya appearance is seen
along with idiopathic occlusion of the internal carotid arteries it is called
moya moya disease; when the occlusion is secondary to some other disease
it is called moya moya syndrome. Causes of moya moya syndrome include
NF1, sickle cell disease, bacterial meningitis, polyarteritis nodosa, radiation
therapy, tuberculosis, and atherosclerosis. Histopathology of occluded
arteries in moya moya disease shows endothelial hyperplasia and fibrosis
without inflammatory reaction. Children with moya moya usually have
ischemia or infarction, while adults with moya moya usually have
hemorrhage. The treatment of moya moya includes anticoagulation,
hypertransfusion, encephalo-duro-arterio-synangiosis (EDAS), anastomosis
of the superficial temporal artery with the intracranial arteries, and
sympathectomy or cervical ganglionectomy.

114. Moya moya appearance. Lateral anterior oblique view (A) of an internal carotid artery
(thick short arrow) angiogram shows multiple, small, tortuous collateral vessels in the
distribution of the middle cerebral artery (arrows), suggestive of the moya moya (puff of
smoke) appearance. Axial view of the MRI angiogram (B) shows complete occlusion of the
middle cerebral arteries bilaterally. Arrows indicate the internal carotid arteries

115. Moyamoya angiographic pattern. Schematic drawing and picture.

116. Eye-of-the-tiger sign
This sign represents marked low signal intensity of the globus palladi on T2W
MRI images. This low signal surrounds a central, small hyperintense area,
producing the eye-of-the-tiger appearance. The sign is seen in what was once
known as Hallervorden-Spatz (HS) syndrome but is now called
neurodegeneration with brain iron accumulation (NBIA) or pantothenate
kinase II (PANC2)-associated neurodegeneration. The marked low signal
intensity of the globus palladi is a result of excessive iron accumulation and
the central high signal is attributed to gliosis, increased water content, and
neuronal loss with disintegration, vacuolization, and cavitation of the
neuropil. Iron levels in blood and CSF are normal. The HS syndrome is a
neurodegenerative disorder associated with extrapyramidal dysfunction and
dementia. It is a neuroaxonal dystrophy, with the pathologic triad of iron
deposition, axonal spheroids, and gliosis in the globus pallidi. MRI is
important for differentiating HS syndrome from infantile axonal dystrophy,
which does not show iron deposition. Mutation of the gene for pantothenate
kinase 2 is the cause for the syndrome. The sign can be seen in other extra-
pyramidal Parkinsonian disorders such as cortical-basal ganglionic
degeneration, Steele-Richardson-Olszewski syndrome, and early-onset
levodopa-responsive Parkinsonism.

117. EYE-OF-THE-TIGER SIGN. Axial T2-WI MR shows low signal surrounding a
central, small hyperintense area, producing the eye-of-the-tiger appearance
in the globus pallidus bilaterally (arrows). Hallervorden-Spatz disease.

118. The eye-of-the-tiger sign. Axial T2W MRI image of the brain shows hypointensity of the globus
palladi (arrows). There is relative hyperintensity of the central part, giving the globus palladi the
appearance of the eyes of a tiger. This appearance is seen in Hallervorden-Spatz syndrome

119. Tau sign
The tau sign represents the appearance of the pre-sellar internal
carotid artery (ICA) when a persistent trigeminal artery (PTA)
originates from it, on a T1W sagittal MRI image . The configuration of
the flow void in the presellar segment of the ICA with the PTA arising
from it, resembles the Greek letter ‘τ’ (tau). The sign is suggestive of a
PTA. The PTA arises from the ICA as it exits the carotid canal and
enters the cavernous sinus. It joins the distal third of the basilar artery
between the origins of the anterior, inferior, and superior cerebellar
arteries. A PTA can be of two types: 1) the artery may supply the entire
vertebrobasilar system distal to the anastomosis or 2) the anastomosis
may mainly supply the superior cerebellar arteries bilaterally. PTA can
be associated with aneurysms, arteriovenous malformations, moya
moya disease, and other persistent carotid-vertebrobasilar
anastomosis. Other persistent arteries that are responsible for
communications between the carotid and vertebrobasilar systems are
persistent hypoglossal and otic arteries.

120. Tau sign. Sagittal T1-W image of
the brain shows (A) flow voids of
the internal carotid artery (ICA) in
the precavernous segment (thick
short arrow), in the cavernous
segment (medium-sized arrow),
and a persistent trigeminal artery
(thin long arrow). Together, these
flow voids form the Greek letter
‘τ’ (tau). Sagittal view of the MRI
angiogram shows the persistent
trigeminal artery (arrow) arising
from the ICA and joining the
basilar artery in its mid segment

121. Harlequin appearance
Harlequin appearance of the orbit represents the
elevation of the superolateral angle of the orbit
along with a flat frontal bone on a plain
radiograph. It is seen in coronal craniosynostosis,
where the anteroposterior growth of the skull is
limited. There is also relative increase in the
transverse diameter of the skull, which is called
brachycephaly. The orbit is shallow, the lesser wing
of the sphenoid is elevated, and the greater wing is
expanded. The innominate line (superior border of
the greater wing of the sphenoid) appears as a
dense ridge. The sign can be unilateral or bilateral.

122. Harlequin appearance. Frontal view of the skull (A) in a child with Apert syndrome
shows elevated superolateral angles of both orbits giving the appearance of a
‘harlequin mask.’ Frontal (B) and lateral (C) surface-shaded display 3D CT views of the
skull show the harlequin appearance of the orbits. The sagittal suture (arrow in B) and
the lambdoid suture (black arrows in C) are wide open. The coronal suture (thin
arrows in C) is fused, which is suggestive of coronal craniosynostosis

123. Skull AP radiograph shows HARLEQUIN APPEARANCE. Schematic drawing and picture of a mask.

124. Central pontine myelinolysis (CPM) is a non-inflammatory
demyelinating disease of the white matter tracts traversing the
pons. Since the peripheral pontine fibers are typically spared it is
referred to as central pontine myelinolysis. The predominant
involvement of the transverse pontine fibers and relative sparing of
the descending corticospinal tracts results in a characteristic "Owls-
eye" appearance on axial T2- weighted MR imaging. If the areas of
demyelination coalesce, axial T2- weighted MR images resemble
"Face of the Piglet". This sign was first reported by Wagner et al.
The pons with its characteristic appearance resembles the snout,
while the internal carotid arteries and the fourth ventricle
constitute the eyes and mouth of the piglet respectively.
Corresponding T1-weighted MR images may show this
characteristic pattern of signal alteration in the basal pons as
resembling the face of a monkey - also referred to as the "Monkey
sign" of CPM

128. "Butterfly Glioma" refers to a high grade astrocytoma, usually a
glioblastoma multiforme, which crosses the midline via the corpus callosum.
The term butterfly refers to the symmetric wing like extensions across the
midline. Mostly butterfly gliomas occur in the frontal lobes crossing via the
genu of the corpus callosum, but posterior butterfly lesions (crossing through
the splenium) are also encountered. The differential diagnoses include
primary cerebral lymphoma and tumefactive demyelination .

129. The "Target sign" or "Bull's
eye" is a favorite radiologic
descriptor of everything from
bowel intussusception to
cerebral tuberculoma. CT
target sign, although
uncommon, is considered
nearly pathognomonic for
cerebral tuberculoma when
it is seen. The three zone T2-
weighted target (bull's eye)
sign at MR imaging has not
been described in any other
condition other than Cerebral
Toxoplasmosis [9]. The T2-
weighted target or bull's eye
sign is characterized by a
hypointense core, an
intermediate hyperintense
region, and a peripheral
hypointense rim.

130. "Batwings dilatation"
of sylvian fissures and wide CSF
spaces anterior to temporal
lobes in a child should alert the
radiologist of the possibility of
Glutaric acidemia type-I. Glutaric
acidemia type-I is a rare
autosomal recessive disorder
caused by the deficiency of a
mitochondrial enzyme glutaryl-
CoA dehydrogenase. This
enzyme deficiency is responsible
for the improper breakdown of
the amino acids resulting in an
elevated plasma and urine level
of glutaric acid. Glutaric acid
accumulation in the body is
responsible for neurotoxicity in
the basal ganglia and fronto-
temporal cortex.

131. "Steer-horn" lateral
ventricles refer to the
abnormal shape of the
frontal horns of the lateral
ventricle on coronal MR
images in patients with
corpus callosum agenesis.
The lack of supporting
deep white matter fibers
and associated redirection
of longitudinal callosal
fibers (Probst bundles),
result in alteration in the
configuration of the
ventricles, with the frontal
horns taking on a "steer or
bull's horn" appearance in
the coronal plane

132. Tectal "Beaking" refers
to the triangular ("beaked")
appearance of the tectum
in Arnold Chiari type-II
malformation (Fig. 32, 33).
The tectum is abnormal in
virtually all patients with
Chiari -II malformation.
The quadrigeminal plate
is partially or completely
fused. The midbrain is
elongated caudally and
posteriorly to overlie the
midline cerebellum and
pons. Variable degrees of
fusion of the colliculi and
tectum result in a
triangular ("beaked")
tectum.

133. The "Zebra" sign
refers to the streaky
pattern of
hemorrhage along the
cerebellar folia in
patients with remote
cerebellar hemorrhage
(RCH). Remote
cerebellar hemorrhage
or cerebellar
hemorrhage distant
from the site of
surgery is a rare,
usually benign,
complication that
most often occurs
after supratentorial
craniotomy.

134. "Rodent facies" refers to the
oro-facial manifestations of
thalassemia major which include
abnormally prominent maxillary
and cheek bones and a depressed
nasal bridge. Erythroid hyperplasia
and extramedullary hematopoiesis
in thalassemic patients results in
hypertrophy of osseous structures
and a consequent prominence of the
malar eminences. Proliferation of
marrow within the frontal and facial
bones impedes pneumatization of
the paranasal sinuses. Radiographs
and CT examination show dilatation
of marrow spaces with coarse
osseous trabeculations. A
generalized loss of bone density
accompanies thinning of the cortex
of maxillary and mandibular bones
with obliterated paranasal sinuses.

135. "Penguin" sign on brain
MRI is an interesting radiological
sign seen in patients with
progressive supranuclear palsy
(PSP). It refers to atrophy of the
midbrain tegmentum, with a
relatively preserved pons on
mid-sagittal T1-weighted
images. The "penguin" sign
can be helpful in distinguishing
progressive supranuclear palsy
from multisystem atrophy and
Parkinson disease. Patients with
Parkinson disease, multisystem
atrophy & corticobasal
degeneration have no midbrain
atrophy & hence do not show
this sign. The penguin sign is
useful for establishing the
diagnosis of PSP; and is reported
to have a sensitivity of nearly
100%.

136. Normally the upper border of the midbrain is convex.
The atrophy of the midbrain in PSP results in a concave upper border
of the midbrain with the typical 'humming bird sign' (figure).

137. Multi System
Atrophy (MSA)
MSA is also one of the
atypical parkinsonian
syndromes. MSA is a rare
neurological disorder
characterized by a
combination of
parkinsonism, cerebellar
and pyramidal signs, and
autonomic dysfunction.

138. Metachromatic leukodystrophy
(MLD) is an autosomal recessive
disorder caused by a deficiency of
the lysosomal enzyme
arylsulfatase. The decreased
activity of arylsulfatase enzyme
accounts for failure of myelin
breakdown and reutilization, thus
resulting in dysmyelination. At T2-
weighted 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. The
sparing of the perivascular white
matter within the periventricular
white matter and centrum
semiovale is responsible for the
characteristic "Tigroid" and
"Leopard skin" pattern.

139. A "Tiger-striped"
cerebellar foliar pattern
that consists of
alternating bands on T1-
and T2-weighted images
is considered almost
pathognomonic of
Lhermitte-Duclos disease.
The maintenance of the
overall cerebellar
architecture in spite of
the thickened, and
hyperplastic folia is
responsible for this
characteristic imaging
appearance . Lhermitte-
Duclos disease (LDD)
(also known as dysplastic
gangliocytoma).

140. Up to 50 percent of tumefactive
demyelinating lesions
demonstrate abnormal contrast
enhancement, often in the form
of ring enhancement. Commonly
the enhancement pattern is in
the form of an "open ring (Horse-
shoe enhancement)", with the
incomplete portion of the ring
facing the cerebral cortex. The
enhancing segment of the ring is
thought to represent the zone of
active demyelination accordingly
favouring the white matter side
of the lesion. The nonenhancing
central part represents a more
chronic phase of demyelination.

141. Thank You.