Neurology info

Question 1

Neurocystcicercosis: Organism

Answer 1

Pork Tapeworm: Taenia solium

Question 2

Neurocystcicercosis: Lesions

Answer 2

Lesions can be parenchymal, intraventricular, or within the subarachnoid spaces. When parenchymal, the cysts are most commonly located at the gray–white matter junction. When intraventricular, the cysts
are often solitary with predilection for the fourth ventricle. When subarachnoid, cysts tend to occur at the cortical sulci. When in the basilar cisterns, cysts may be racemose or “grape-like.”

Question 3

Neurocystcicercosis: Stages

Answer 3

There are four stages of the disease with distinct imaging findings. In the vesicular stage, the cyst is
thin walled and has signal characteristics similar to CSF without contrast enhancement or edema. An eccentric, discrete scolex can be seen. In the colloidal vesicular phase, the larva begins to degenerate creating an inflammatory response and resultant surrounding edema. The hyperintense cyst at this stage will demonstrate ring-like peripheral enhancement. In the granular nodular stage, the cyst decreases in size and the cyst wall retracts, surrounding edema decreases, and nodular or ring-like enhancement persists. Finally in the nodular calcified stage, the cyst is shrunken and calcified with hypointensity on T2
and gradient echo sequences

Question 4

Subdural empyema

Answer 4

The main differential diagnosis is an epidural empyema that is meniscal in shape.
Other extra-axial fluid collections containing blood products or cerebrospinal fluid should also be
considered. Subdural lymphoma may occasionally be a diagnostic challenge on imaging (restricted
diffusion), but clinical findings are very different from an acutely infected patient.

Question 5

Cryptococcal meningitis: Imaging

Answer 5

The histology of CNS involvement is primarily meningeal, less frequently parenchymal with typical distribution in the basal ganglia and midbrain, resulting in the three most common imaging patterns of meningitis, cryptococcoma, or gelatinous pseudocysts.

Question 6

Cryptococcal meningitis

Answer 6

Toxoplasmosis, tuberculosis

Question 7

Toxoplasmosis

Answer 7

On imaging, toxoplasmosis and lymphoma can look very similar in AIDS patients. Toxoplasmosis tends to reveal multiple ring-enhancing lesions in the basal ganglia and corticomedullary junction.
Lymphoma is usually a single, solid-enhancing periventricular lesion in immunocompetent patients but is more often multifocal and irregularly enhancing or rim enhancing in AIDS patients. Both can restrict diffusion; however, it has been shown that toxoplasmosis demonstrates greater restriction on average when compared to lymphoma.
Given the overlap of imaging findings, advanced MR imaging and nuclear medicine are both helpful
tools. On MR perfusion, lymphoma has increased perfusion and toxoplasmosis has decreased perfusion.
On MR spectroscopy, both can have lipid–lactate peaks, but lymphoma tends to have significantly
increased Cho/Cr ratio. On thallium 201 SPECT and 18F-FDG PET, lymphoma is hypermetabolic and
toxoplasmosis is hypometabolic

Question 8

TB:

Answer 8

The most common manifestation of CNS TB is meningitis and is most frequently seen in children. The radiologist should have a high index of suspicion for diagnosing the complications from the meningitis including hydrocephalus, vasculitis, infarct, and cranial nerve involvement.The other main imaging manifestation of CNS TB is intraparenchymal involvement with a tuberculoma, which can be solitary or multiple. Parenchymal tuberculomas can be isolated or be seen along with meningitis. When the two are seen together, it is highly suggestive of TB. Tuberculomas typically demonstrate heterogeneous hypointensity on MR with ring-like peripheral enhancement

Question 9

Basilar leptomeningeal enhancement ddx

Answer 9

Neurosarcoid, other infectious etiologies including fungal disease, and leptomeningeal carcinomatosis

Question 10

Stages of cerebral abscess formation

Answer 10

Early cerebritis: Ill-defined vasogenic edema with minimal or no enhancement
Late cerebritis: Central slow diffusion with ill-defined rim enhancement
Early capsule stage: More well-defined rim-enhancing capsule
Late capsule: Thicker rim enhancement, decreasing vasogenic edema

Question 11

Cerebral abscess findings

Answer 11

The medial wall of the abscess cavity may be thinner than lateral wall owing to differential blood supply, which predisposes to intraventricular rupture and satellite abscess formation. The abscess rim often shows low signal on T2-weighted and SWI images. On MR spectroscopy, there is a decrease in Nacetylaspartate (NAA), choline, and creatine, and elevated cytosolic amino acids and succinate.

Question 12

CJD: Imaging

Answer 12

On imaging, CJD classically demonstrates bilateral basal ganglia T2 and DWI hyperintense signal with the caudate and putamen affected more commonly than the globus pallidus. Cortical distribution is often asymmetric. The thalami are affected either with pulvinar involvement or with both pulvinar and dorsomedial thalamic nuclei involvement. T1-weighted imaging tends to be normal and withoutenhancement, which can help differentiate from other differential considerations. White matter is often spared. Cerebral atrophy is not a prominent finding in CJD in comparison to other dementias.

Question 13

CADASIL

Answer 13

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy.

Question 14

CADASIL: Clinical

Answer 14

CADASIL is a hereditary disease secondary to a mutation in NOTCH3 gene on chromosome 19 leading to strokes in young to middle age adults who are otherwise healthy without stroke risk factors. CADASIL typically presents at age 30 to 50 with TIA/stroke-like symptoms, and many patients also present with migraine headaches with aura. The disease is progressive with cognitive decline and early death. Lacunar infarct burden has been shown to have an important impact on cognitive function and disability

Question 15

CADASIL Findings

Answer 15

On imaging, CADASIL classically demonstrates relatively bilaterally symmetric FLAIR hyperintense signal abnormality within the paramedian superior frontal lobe subcortical white matter, anterior temporal lobes, and external capsules. The anterior temporal lobe involvement has been shown to be both highly
specific and sensitive for aiding in the diagnosis of CADASIL. Cerebral microbleeds on gradient echoimaging are often also seen

Question 16

CADASIL Ddx

Answer 16

Other vascular or demyelinating disease

Question 17

Hypertrophic olivary degeneration: Pathology

Answer 17

HOD is associated with lesions in afferent fibers to ION (first two limbs of the triangle). So, HOD is seen with lesions in contralateral dentate nucleus and ipsilateral brain stem. Transsynaptic degeneration is the proposed mechanism for HOD. Lesions of the olivodentate fibers can cause cerebellar atrophy.
During the first month or so following the ictus, generally, there won’t be any imaging changes in ION.

Question 18

Hypertrophic olivary degeneration: Stages

Answer 18

1. Acute stage with increased T2 signal without hypertrophy, first 6 months after ictus
2. Both increased signal and hypertrophy of ION, 6 months to 3 to 4 years after ictus
3. Disappearance of hypertrophy with some persistence of increased signal

Question 19

X-linked adrenal leukodystrophy: genetics

Answer 19

X-linked adrenal leukodystrophy (ALD) is caused by a pathogenic variant within the ABCD1 gene on chromosome Xq28 mutation. This gene codes for a peroxisomal membrane protein that plays a key role in the transport of very long chain fatty acids into the peroxisome, where they are normally metabolized. Hence, the analysis of very long chain fatty acids in plasma can be used as a diagnostic biomarker for ALD.

Question 20

X-linked adrenal leukodystrophy: imaging

Answer 20

The most common neuroimaging pattern in the childhood cerebral form of ALD consists of symmetric and predominantly parietooccipital white matter abnormalities that typically start in the splenium of the corpus callosum. The U-fibers and the cerebellum are relatively spared in the early onset of the disease, whereas the geniculate bodies, the lateral inferior part of the thalamus, and the posterior limb of the
internal capsule may be affected early. In about 20% of the patients, the primary involvement involves the frontal white matter. After injection of contrast, a rim of enhancement may be noted surrounding the
abnormal white matter. Enhancement seems to be associated with clinical worsening of the disease.

Question 21

Metachomatic leukodystrophy: pathology

Answer 21

Metachromatic leukodystrophy is an autosomal recessive lysosomal disease caused by deficiency of arylsulfatase A activity leading to the accumulation of alactosylsulfatide in the white matter of the central and peripheral nervous system

Question 22

Metachomatic leukodystrophy: Imaging

Answer 22

MR images are nonspecific and may show areas of T2/FLAIR hyperintense signal in the deep and
periventricular cerebral white matter, whereas the subcortical white matter (U-fibers) is spared until late in the course of the disease. Stripes of affected and unaffected myelin (called a “tigroid” pattern) may be seen and represent relatively spared myelin and lipid-containing glial cells in the perivascular spaces.

Question 23

Metachomatic leukodystrophy: ddx

Answer 23

Periventricular predominance of white matter signal changes may be seen in several (hereditary and acquired) white matter diseases including Krabbe disease, Sjögren-Larsson disease, leukoencephalopathy with brainstem and spinal cord involvement and high lactate (LBSL), periventricular leukomalacia, and HIV leukoencephalopathy. The “tigroid pattern” may be seen in Krabbe disease and GM1 gangliosidoses. Hematopoietic stem cell transplant, if performed early in metachromatic leukodystrophy, can not only stabilize but even improve cerebral white matter
abnormalities

Question 24

MELAS

Answer 24

Mitochondrial encephalomyopathy with lactic acidosis and stroke like episodes

Question 25

MELAS: Genetics

Answer 25

point mutations within the mitochondrialDNA affecting transfer RNA genes. The A3243G mutation in the tRNAleu(uur) gene of the mitochondrial DNA is responsible for about 80% of MELAS cases

Question 26

MELAS: Findings

Answer 26

In the acute phase, MRI typically shows swelling and T2/FLAIR hyperintense signal and matchingrestricted diffusion in the affected areas, which usually involve the parietal and occipital cortex and subcortical white matter as well as the basal ganglia. Cerebellar atrophy typically develops over time.
Follow-up MR studies may show additional new lesions. The lesions are not restricted to a specific arterial distribution, and single lesions often cross vascular boundaries. 1H-MR spectroscopy shows high
lactate in affected areas of the brain.

Question 27

Canavan disease: Pathology

Answer 27

Canavan disease or spongiform leukodystrophy is an autosomal recessive disorder caused by a deficiency of spartoacylase. This enzyme is important for the hydrolysis of N-acetylaspartate (NAA)

Question 28

Canavan disease: Findings

Answer 28

MR images usually reveal diffuse, symmetric T1 hypointense, and T2/FLAIR hyperintense abnormalities of the cerebral white matter without any focal predominance. The subcortical white matter
is preferentially affected early in the course of the disease. The globi pallidi are nearly always affected
with sparing of the adjacent putamen. Thalami are frequently involved. The dentate nuclei may also be
affected. Proton spectroscopy shows increased NAA peak: this finding is strongly suggestive of Canavan
disease and is already present when the rest of the MRI is still normal (neonatal age)

Question 29

Canavan disease: ddx

Answer 29

Preferential involvement of the subcortical white matter may be also seen in l-2- hydroxy glutaricaciduria, Kearns-Sayre disease, propionic acidemia, and urea cycle disorders. Canavan disease occurs more frequently among patients of Ashkenazi Jewish descent.

Question 30

Wilson disease: genetics

Answer 30

inborn error of copper metabolism caused by a mutation to the copper-transporting gene ATP7B. The disease has an autosomal recessive mode of inheritance and is characterized by excessive copper deposition, predominantly in the liver and brain

Question 31

Wilson disease: imaging

Answer 31

MR imaging abnormality in patients with Wilson disease can be related to hepatic dysfunction manifested by increased T1 signal intensity in the globus pallidus, putamen, and mesencephalon. Increased T2 signal in the putamen, thalami, and brainstem reflects copper deposition in brain tissue, which can result in edema,
necrosis, and spongiform degeneration. The midbrain can show “face of the giant panda,” and dorsal
pontine abnormalities resemble the “face of a panda cub.

Question 32

Alexander disease: pathology

Answer 32

Alexander disease is an autosomal dominant disease caused by pathogenic variants within the gene encoding the glial fibrillary acidic protein (GFAP)

Question 33

Alexander disease: Imaging criteria

Answer 33

(a) extensive cerebral white matter changes (T1 hypointensity and T2 hyperintensity) with frontal predominance,
(b) a periventricular rim with hyperintense signal on T1-
weighted images and hypointense signal on T2-weighted images,
(c) abnormalities of the basal ganglia(particularly the caudate heads and anterior putamina) and thalami,
(d) brainstem abnormalities, and
(e) contrast enhancement of periventricular regions and lower brainstem

Question 34

NF1: Genetics

Answer 34

Neurofibromatosis 1 is an autosomal dominant inherited disease from a mutation in the NF1
gene located on chromosome 17

Question 35

NF1: diagnostic criteria

Answer 35

2 or more of the following: 6 or more café au lait spots, 2 or more neurofibromas, or 1 plexiform neurofibroma, axillary/inguinal freckling, optic glioma, distinctive osseous lesion (sphenoid wing dysplasia, bowing of long bone with or without pseudoarthrosis), and first-degree relative with NF1

Question 36

NF1: CNS characteristics

Answer 36

nonenhancing hyperintense T2/FLAIR lesions. These
lesions are often found in the deep gray matter, hippocampi, brainstem, and cerebellum with little to no
mass effect. They can increase in size and number as the child grows but tend to diminish in teenage years
and resolve by adulthood. Optic pathway gliomas in NF1 can occur anywhere from the optic nerve through the optic radiations. Plexiform neurofibromas course along peripheral nerves and are hyperintense on T2-weighted imaging with central hypointensity—“target sign.” Sphenoid wing dysplasia manifests by distortion or absence of the lateral orbital wall and often associated with an orbital plexiform neurofibroma. Rarely, NF1 patients can have a vascular dysplasia with moyamoya-like arteriopathy with vessel narrowing and collateral formation.

Question 37

PKAN

Answer 37

pantothenate kinase–associated neurodegeneration also known as HallervordenSpatz syndrome)

Question 38

PKAN: genetics

Answer 38

classified as a neurodegenerative disorder with brain iron accumulation (NBIA). It involves a mutation in the PANK2 gene on chromosome 20`

Question 39

PKAN: Imaging findings

Answer 39

On MRI, T2- weighted images demonstrate hypointense signal in the globus pallidus with an anteromedial
hyperintensity (“eye of the tiger” sign) and in the substantia nigra. Eye of the tiger appearance may
precede the development of clinical symptoms. The degree of iron deposition correlates incompletely
with symptoms.

Question 40

TS: Genetics

Answer 40

autosomal dominant inherited disease with mutations either in the TSC1 or TSC2

Question 41

TS: criteria

Answer 41

CNS major criteria include cortical dysplasias (including cortical tubers and radial migration lines), subependymal nodules, and SEGAs. Additional major criteria include multiple skin findings (hypomelanotic macules, angiofibromas, ungula fibromas, and shagreen patch), retinal hamartomas, cardiac rhabdomyomas, LAM, and renal AMLs

Question 42

TS: imaging findings

Answer 42

The CNS imaging findings of cortical tubers, subependymal nodules, radial migration lines, and
SEGA are classic for TS. Cortical tubers are T2/FLAIR hyperintense and are located most commonly
supratentorially with greatest predilection for the frontal lobe, although infratentorial lesions can occur.
Subependymal nodules tend to line the lateral ventricles, have lower T2-weighted signal intensity than
cortical tubers, and often calcify. Subependymal nodules can enhance, and thus, serial imaging to look for interval growth is key to diagnosing SEGAs. SEGAs are most commonly located at the foramen of Monroe with a peak age at 8 to 18 years of age. It is important to diagnose these lesions as patients can
present acutely with obstructive hydrocephalus and increased intracranial pressure if there is obstruction at the foramen of Monroe. White matter abnormalities include radial white matter bands that reflect altered migratory development of neurons and glial cells. They are thin curvilinear or straight T2 hyperintense lines extending from the ventricles to the deep surface of cortical tubers. White matter cystic spaces can also be seen and follow CSF on all imaging sequences.

Question 43

Progressive supranuclear palsy: pathology

Answer 43

Pathologically, the disease is characterized by

neurofibrillary tangles and/or neuropil threads in the basal ganglia and brainstem

Question 44

Progressive supranuclear palsy: Imaging

Answer 44

MRI is performed to exclude other diagnoses like stroke, tumor, and hydrocephalus. Findings supportive of PSP include T2 hyperintensity and atrophy of the midbrain, thinning of the substantia nigra, and atrophy of the putamen and globus pallidus.
The hummingbird or penguin sign in PSP patients is seen on a midsagittal plane as atrophy of the midbrain tegmentum and preserved profile of the pons. The decreased ratio of the area of the midbrain tothe area of pons has also been shown to differentiate patients with PSP from normals and multisystem atrophy.
Hot cross bun sign seen in patients with MSA (multisystem atrophy) refers to cruciform hyperintensity
through the pons on axial T2-weighted image, representing the selective loss of myelinated transverse pontocerebellar fibers and neurons in the pontine raphe with sparing of the pontine tegmentum and corticospinal tracts (see below). It has also been described in patients with parkinsonism, CJD, and
spinocerebellar atrophy.

Question 45

Mesial temporal sclerosis

Answer 45

esial temporal sclerosis (MTS) is the most common cause of partial complex seizures in the adult population. MTS is best diagnosed with MRI with thin cut coronal T2 and coronal FLAIR imaging through the temporal lobes and hippocampi. Primary signs of MTS on imaging include hippocampal atrophy, T2/FLAIR hyperintensity, and loss of normal hippocampal internal architecture.
Secondary signs of MTS include dilatation of the ipsilateral temporal horn as well as volume loss of the
ipsilateral fornix and mammillary body. MTS is most often unilateral but can be bilateral approximately
20% of the time

Question 46

Sturge Weber syndrome:

Answer 46

SturgeWeber is a rare disease affecting approximately 1 in 50,000 to 230,000 people. Unlike the other
phakomatoses, Sturge-Weber is felt not to be hereditary and rather results from a somatic mutation the
GNAQ gene on chromosome 9q21

Question 47

Sturge Wever findings

Answer 47

gyral and subcortical calcifications, cerebral atrophy, ipsilateral choroid plexus enlargement, and leptomeningeal enhancement with pial angiomatosis all within the same cerebral hemisphere. The distribution tends to progress from posterior to anterior with the
occipital and parietal lobes involved greater than the frontal and temporal lobes. Infratentorial involvement is not classic but does occur as well.

Question 48

ALS:

Answer 48

Conventional MR imaging in ALS patients demonstrates increased signal on T2-weighted, proton
density-weighted, and FLAIR sequences in the cortical spinal tracts, a finding that is reported to be
approximately 60% sensitive. This finding is not very specific and has been described in healthy subjects.
Corticospinal tract signal intensity changes do not correlate with clinical scores of the disease.
Additionally, a characteristic low signal intensity of the precentral cortex on T2-weighted images has
been observed; again, this finding is neither very sensitive nor specific. Advanced imaging techniques
including MR spectroscopy (decrease in the NAA level and NAA to creatinine ratio), diffusion tensor
imaging (decrease in fractional anisotropy), and functional MRI may be helpful for prognostication.

Question 49

Normal pressure hydrocephalus

Answer 49

In addition, memory loss with gait difficulties and urinary incontinence may be seen with normal pressure hydrocephalus. The presence of moderate ventriculomegaly without commensurate increase in sulcal volume may be seen with normal pressure hydrocephalus. It has been reported that in infarct-free older individuals from a population-based cohort, those in the highest quartile of ratio of ventricular
volume/sulcal volume were more likely to have impaired gait and cognition. Specific regional patterns of atrophy are reported with other entities such as Alzheimer dementia (medial temporal/hippocampal, parietooccipital), frontotemporal lobar degeneration (frontotemporal), and progressive supranuclear palsy (infratentorial). However, early changes from these entities may remain occult on structural
imaging; therefore, despite lack of a specific pattern of neurodegeneration on these images, these other
entities remain considerations in the appropriate clinical setting

Question 50

Oligodendroglioma: epidemiology

Answer 50

Oligodendroglioma is a tumor of neuroglial origin with variable prognostic features, ranging from relatively low aggressive potential relative to a similar-grade astrocytoma to very aggressive behavior similar to higher grade glial neoplasms. It is the third most common glioma, accounting for 5% to 18% of all glial neoplasms.

Question 51

Oligodendroglioma: Imaging features

Answer 51

Calcification within oligodendroglioma may range from 20% to 90%; occasionally cystic degeneration and hemorrhage may also be seen. On MR, most commonly heterogenous signal intensity is noted; vasogenic edema although present is typically not as striking or common as the higher grade astrocytoma, and the ADC values on diffusion-weighted imaging might be low, such as seen with other higher grade glial neoplasm, purported to have resulted from lowered extracellular hyaluronic acid.

Question 52

Oligodendroglioma: Differentials

Answer 52

Other primary CNS glial neoplasm, metastasis, or less likely meningioma. Although other primary CNS glial neoplasms and metastasis cannot be excluded, the presence of calcification, peripheral cortical location, and lack of significant vasogenic edema are most typical for oligodendroglioma. Meningioma is not likely because this is a peripheral but intra-axial lesion instead of an extra-axial lesion

Question 53

Glioblastoma: Epidemiology

Answer 53

It is the most common primary CNS neoplasm (~15% of all intracranial neoplasms).
In distribution, it is frequently supratentorial, predominantly involving ages 40 to 70 years. When it is
rarely found in children, it may be more commonly infratentorial compared to adults.
The majority of these lesions have a rapid clinical course, have an abrupt presentation, and arise de
novo within the brain, that is, without a preexisting lower grade precursor lesion. However, a few lesions
may result from de-differentiation of a preexisting lower grade glial neoplasm; typically, the latter is seen in younger population (mean age, 40 years) and has a longer clinical course.

Question 54

Glioblastoma: Imaging features

Answer 54

Proton MR spectroscopy typically demonstrates elevation of choline (3.2 ppm) and lactate peak (1.3
ppm). MR perfusion (either DSC or DCE) shows elevated CBV within the lesion, as would have been the case with any other aggressive neoplasm and occasionally with aggressive emyelination/inflammation.
However, it is noteworthy that both MR perfusion and proton MR spectroscopy, are nonspecific in isolation and should be interpreted in conjunction with lesion morphology on other sequences and clinical
presentation.

Question 55

Glioblastoma: Differentials

Answer 55

Metastasis, primary CNS lymphoma, herpes encephalitis, are differential consideration; however as explained above, the most likely diagnosis will be primary CNS glial neoplasm.
There has been a recent update in the glial neoplasm classification as of June 2016 with incorporation
of the specific molecular profile. This was necessary because the histopathologic classification alone did
not accurately predict clinical course or treatment response. For example, presence of IDH mutation, and
ATRX loss are associated with a favorable prognosis.

Question 56

Haemangioblastoma: Epidemiology

Answer 56

Hemangioblastoma is a benign slow-growing tumor of vascular origin. Its pathogenesis and cell of origin are not known. About two-thirds of these are sporadic, and the rest are seen in association with von Hippel-Lindau syndrome (VHL). Multiple tumors are almost always associated with VHL. A rare non-VHL form of multiple hemangioblastomas has been reported, known as leptomeningeal hemangioblastomatosis. Metastasis is extremely rare, but has been reported.
They are primarily seen in third to fifth decade of life; the presentation is earlier by a decade in VHL associated tumors. They account for about 2% of intracranial tumors and 10% of posterior fossa tumors.
They are the most common primary brain tumor of the posterior fossa in an adult. Most are located in the
posterior fossa (cerebellum, vermis, and medulla in that order), followed by the spinal cord.
Supratentorial location is rare, seen in about 5% to 10%. The growth pattern can be “stuttered” with periods of quiescence and growth.
The most common tumor morphology is peritumoral cyst with an intensely enhancing tumor nodule,
seen in about 60%. About 30% of tumors are purely solid. Solid tumors, intratumoral cysts, and tumors
with intra- and peritumoral cyst are rare patterns.

Question 57

Haemangioblastoma: Imaging features

Answer 57

On CT, the cyst is hypodense and the nodule is almost isodense to the parenchyma. On MRI, the cyst
shows fluid signal on T2 images. The solid nodule shows moderate hyperintensity on T2 and
hypointensity on T1. Intense contrast enhancement of the nodule is typical. Tortuous vessels can be
demonstrated in the vicinity of the tumor in precontrast, postcontrast, and CTA/MRA images. The
surrounding edema is variable and can be disproportionately large compared to the nodule size. In larger nodules and solid masses, the enhancement can be heterogeneous. The cyst wall either shows no
enhancement or minimal thin enhancement.

Question 58

Haemangioblastoma: Differentials

Answer 58

In children, pilocytic astrocytoma.
In adults, metastatic disease. In patients with VHL, metastasis from renal cell cancer can be hypervascular and may pose diagnostic difficulty

Question 59

Vestibular Schwannoma: Epidemiology

Answer 59

Vestibular schwannoma is the most common mass in the CP angle, accounting for 85% of CPangle masses. Schwannoma is a benign, slowly growing neoplasm. CP angle schwannomas most commonly involve the inferior division of the vestibular nerve (vestibular branch of CN VIII). A majority of the intracranial schwannomas are sporadic. Less than 20% of these may be associated with neurofibromatosis type 2. Intracranial schwannomas most commonly occur along sensory nerve fibers, of which CN VIII is most common, followed by trigeminal nerve.
Patients commonly present with hearing loss, rarely with vertigo and imbalance. Management of such
lesions can include observation, Gamma Knife surgery, or microsurgical resection. Various factors
influence the treatment choices, and therefore further subspecialty consultation will be warranted to better
understand treatment options.

Question 60

Vestibular Schwannoma: Imaging features

Answer 60

The most likely explanation for this enhancing mass without restricted diffusion will be a vestibular schwannoma. Neurofibroma, also a nerve sheath tumor, has greater risk of malignant transformation but is exceedingly rare as a primary intracranial lesion, even in patients with type 1 neurofibromatosis, making this a very unlikely diagnosis for CP angle masses. CP
angle meningioma is a differential possibility and cannot be reliably excluded on imaging alone.
However, meningioma typically presents with a dural tail and adjacent reactive osseous hyperostosis and
may also have restricted diffusion due to high cellularity, not seen in this case. Epidermoid lesion
typically follows CSF appearance on both CT and MRI; however, it also demonstrates restricted
diffusion. Enhancement if any is typically peripheral in nature.

Question 61

Vestibular Schwannoma: Differentials

Answer 61

Mengingioma (a dural tail, reactive hyperostosis in the underlying bone, and potentially restricted diffusion due to higher cellularity may be seen as differentiating features; however oftentimes this is difficult to definitively differentiate, particularly because meningiomas may have canalicular AND labyrinthine extension); epidermoid (follows CSF signal and shows restricted diffusion); metastasis (rare in isolation; typically seen with leptomeningeal disease, prior history of a primary).

Question 62

Ependymoma: Epidemiology

Answer 62

Ependymoma is a type of primary CNS neoplasm that arises from the ependymal lining. They are within the subtype of neuroepithelial neoplasms unlike astrocytomas, which are primary neuroglial
subtype of tumors.
These tumors can be seen at any age. Typically, younger patients tend to have posterior fossa and
older patients tend to have supratentorial ependymoma. These can be found in the fourth, lateral, and third ventricles. These can also be extraventricular in location particularly when seen in a supratentorial
location in children. These are classified as WHO grade II lesions. Variant of higher grade or anaplastic
ependymomas have also been reported (WHO grade III).

Question 63

Ependymoma: Imaging features

Answer 63

Imaging features on MR are typically hyperintensity on T2-weighted images and isointensity on T1-
weighted images with intense contrast enhancement within the soft tissue components. Calcification,
hemorrhage, and cystic components are commonly seen that lead to morphologic heterogeneity within this
lesion. These lesions are classically defined as soft or plastic lesions; when seen in the fourth ventricle,
these can squeeze through the foramen of Luschka, foramen of Magendie, and foramen magnum.
Postoperative imaging is key in determining survival rate with residual disease associated with a
lower overall survival.

Question 64

Central neurocytoma: Epidemiology

Answer 64

Central neurocytomas are WHO grade II lesions that are commonly seen in young adults and
adolescents within the intraventricular location, predominantly in the lateral ventricle attached to the wall or septum pellucidum. Rarely, extraventricular occurrences of neurocytoma have been reported; however, the term “central” neurocytoma is reserved for the former. Complete surgical excision is standard
management with role of postsurgical radiation therapy in selected cases such as incomplete resection.
Given the propensity of this lesion to attach to the septum pellucidum adjacent to the Monro foramen,
these lesions are associated with obstructive hydrocephalus and typically need ventriculostomy catheter for extraventricular CSF drainage for decompression along with gross total resection. Although extremely rare, central neurocytomas can occur in the spinal cord as a primary intramedullary lesion

Question 65

Central neurocytoma: Imaging features

Answer 65

On Imaging, these are lobulated masses with frequent cystic foci giving it a bubbly appearance. About half of these lesions may also have calcifications. These are isointense to gray matter on T1w and hyperintense on T2w sequences. On postcontrast T1w, these lesions can show moderate to intense heterogenous enhancement. Periventicular T2 hyperintensity and prominent flow voids may also be present.

Question 66

Brainstem glioma: Epidemiology

Answer 66

Brainstem gliomas (BSG) are a heterogeneous group of tumors with distinct subtypes with variable prognosis. They account for 10% to 20% of all intracranial tumors in children. They canuncommonly be seen in adults (median age of 30 to 35 years). In adults, the behavior and prognosis are similar to those of supratentorial gliomas. The rest of the discussion here is focused on pediatric BSG.
They are broadly classified into diffuse infiltrating type (about 80% of BSG) and focal gliomas. The prognosis largely depends on the site of origin. Also, BSG that are associated with NF1 have better prognosis.
Midbrain gliomas (tectal or tegmental) are generally low grade (pilocytic/grade II astrocytoma or ganglioglioma) and tend to be indolent. The treatment is often just shunting and imaging surveillance.
Tumor-specific treatment is pursued in the unlikely event of tumor growth.
Most pontine gliomas are infiltrating fibrillary astrocytomas with poor prognosis. Irrespective of
histologic grading, these have an aggressive course with a mean survival of 4 to 15 months. They tend to
show extension into the midbrain superiorly and medulla inferiorly and through the middle cerebellar
peduncle into the cerebellar hemisphere.
Less commonly, focal tumors can arise in the pons, and they show a good prognosis. Medullary tumors commonly show lower grade and better prognosis and have a higher incidence of exophytic growth compared to pontine tumors.

Question 67

Brainstem glioma: Imaging features

Answer 67

On CT, one-third of pontine tumors are hypodense, one-third are isodense, and most of the remainder
show mixed density. In case of hemorrhage, tumors can have high density. Smaller midbrain tumors may
not be well seen on CT. On MRI, BSGs are hypointense on T1 and hyperintense on T2/FLAIR. Patchy, focal, or ring enhancements within pontine tumors are common (either at presentation or developing during the course of the disease) as is hemorrhage; these features suggest an aggressive tumor. But enhancement in focal tumors and medullary tumors do not necessarily mean bad prognosis. Expanded brainstem that obliterates the prepontine cistern, compresses the fourth ventricle, and envelops the basilar artery is a strong indicator for BSG. Obstructive hydrocephalus occurs commonly with midbrain and medullary tumors and less commonly with pontine tumors. In case of aqueductal pattern of hydrocephalus, MRI is the investigation of choice to evaluate for midbrain tumors as smaller tumors may not be evident on CT and the patient may carry a diagnosis of just “aqueductal stenosis” instead. Midbrain tumor is
better demonstrated with thin slices through this region, preferably a 3D T2 or steady-state sequence in
sagittal plane.

Question 68

Brainstem glioma: Ddx

Answer 68

Demyelinating disease: Clinical picture is usually distinct with often multiphasic episodes; often
multifocal in involvement with supra- and infratentorial lesions.
Infection (abscess and cerebritis): Tuberculosis
Neuro-Behcet syndrome: Generally in young adult population

Question 69

Intracranial epidermoids: Epidemiology

Answer 69

Intracranial epidermoids are congenital tumor-like inclusion cysts and constitute about 1% of
intracranial tumors. They are believed to be the result of sequestration of ectodermal element within the
neural tube during the 3rd to 5th week of embryonic development. Acquired epidermoid is rare in the
brain.
They are well-marginated lesions with irregular nodular surface and composed of a wall made up ofstratified keratinized squamous epithelium surrounded by connective tissue. The cyst content is mainly
derived from desquamated epithelial cells and includes debris, keratin, water, and cholesterol. These
lesions do not contain dermal appendages.
The clinical presentation depends on the location and the degree of mass effect on adjacent neural
structures. There may also be chemical meningitis secondary to leakage of cyst contents into subarachnoid space. The common locations are CP angle cistern (40% to 50% of lesions), fourth ventricle, sellar region, and less commonly intraparenchymal. Ten percent of tumors are extradural.

Question 70

Intracranial epidermoids: Imaging features

Answer 70

On imaging, they are thinly marginated, but irregular lesions, insinuating within the CSF space encasing and surrounding adjacent vessels and nerves. Calcification can be seen in 10% to 25% of cases.
Rarely, intralesional hemorrhage can be present. On CT, the lesions are well circumscribed and hypodense and often show near CSF density, similar in appearance to arachnoid cyst. MRI is the investigation of choice. On T1 and T2 images, they look somewhat similar to an arachnoid cyst showing near CSF intensity or slight hyperintensity relative to CSF. On FLAIR images, these show incomplete signal suppression and can show some degree of heterogeneity. Diffusion images show restriction, which is the most useful MR imaging feature for diagnosis. Most of the lesions show no contrast enhancement; about a quarter show minimal rim enhancement.
Epidermoid can be hyperdense on CT because of hemorrhage or proteinaceous content (white
epidermoid). These lesions can be hyperintense on T1 images and show variable signal on T2 images.
Diffusion restriction is typically present. Malignant degeneration of epidermoid is extremely rare, but
reported

Question 71

Intracranial epidermoids: Ddx

Answer 71

Arachnoid cyst: especially on CT. On MRI, the differentiation is easy as epidermoids show incomplete
FLAIR suppression and diffusion restriction unlike arachnoid cysts

Question 72

Primary CNS Lymphoma: Epidemiology

Answer 72

Primary CNS lymphoma (PCNSL) is an extranodal non-Hodgkin lymphoma that affects the brain and is rarely isolated to the spinal cord, meninges, and orbit. It is usually of the large B-cell variety, which represents 5% to 7% of all primary brain tumors. By definition, extra-CNS disease is absent at the time of diagnosis.
Cerebral hemispheres are the commonest site with predilection of periventricular region and corpus
callosum, followed by basal ganglia, thalami, and rarely posterior fossa. Lymphoma is a differential
consideration for “butterfly” tumor. Leptomeningeal involvement occurs in about 12% tumors; dural
involvement is rare. They tend to show angiocentric growth pattern. Most of the tumors tend to abut the
CSF surface (either ventricular margin or the pia) with a tendency for subependymal spread. The mass
effect is less pronounced for their size.
Over half of the tumors are solitary. The internal imaging characteristics depend on the immune status.
In immunocompetent patients, the tumors occur in older age group with a mean age of about 60 years.

Question 73

Primary CNS Lymphoma: Imaging features

Answer 73

The most common presentation is solid uniformly enhancing lesion showing high cellularity and
prominent perilesional edema. The high cellularity results in hyperdensity of CT, iso- to only mildhypointensity on T1-weighted images, intermediate to low signal on T2-weighted images, and restricted diffusion. Untreated lesions do not show calcification. Less commonly, they can be infiltrative and rarely
can show necrosis, hemorrhage, and even no enhancement.
In immunocompromised patients, the lesions tend to occur at an earlier age (mean age of about 40
years). They show a higher incidence of necrosis, hemorrhage, and inhomogeneous enhancement.
Secondary lymphomas tend to involve dura and leptomeninges and only rarely present as isolated
parenchymal mass.
PCNSL show increase in CBV on perfusion studies, but less than what is seen with glioblastomas.
Reduction in ADC is more dramatic than what can be seen with tumefactive demyelination. Spectroscopy
shows “tumor signature.” They are FDG avid.

Question 74

Primary CNS Lymphoma:

Answer 74

Glioblastoma: hemorrhage and necrosis are the hallmark, which are rare in PCNSL of
immunocompetent patients. Abutment of CSF surface is more common with lymphoma. Uniform restricted diffusion is rare with glioblastoma.
Metastases: History and multiplicity are helpful. Diffusion restriction is less common with metastatic
disease. They tend to be located at gray-white junction as opposed to near the CSF surface with
lymphoma. Mass effect is disproportionately less for lesion site with lymphomas, as opposed to
metastasis.
Tumefactive demyelination: Enhancement is more commonly peripheral, incomplete ring shaped, or
comma shaped. Concentric rings of differing signal on T2-weighted images favor demyelination.
Diffusion restriction can occasionally be seen with acute demyelination, but tends to be more pronounced with lymphoma. In difficult cases, follow-up is the key.
Toxoplasmosis: This is a differential consideration in the immunocompromised. Eccentric target sign favors toxoplasmosis. As opposed to lymphoma, toxoplasmosis is non-avid on PET and on thallium scan.

Question 75

DNET: Epidemiology

Answer 75

Dysembryoplastic neuroepithelial tumor (DNET) is a benign grade I glial–neuronal neoplasm, commonly seen in the second and third decades of life with male preponderance and presenting with intractable seizures.
It is peripherally located in the cortex with gyral expansion. Underlying white matter is often involved. Temporal lobe is the most common location followed by frontal lobe. Deeper location is uncommon and includes the basal ganglia, thalamus, pons, and cerebellum. Clinicoradiologic criteria for diagnosis include seizure onset before 20 years of age, absence of neurologic deficit, cortical location of the lesion and absence of mass effect/peritumoral edema.

Question 76

DNET: Imaging features

Answer 76

Typical radiologic features include a corticalbased wedge-shaped well-demarcated mass pointing toward the ventricle, presence of internal septations,
absence of contrast enhancement, and scalloping of the overlying bone. On CT, these lesions are hypo- to isodense. On MRI, these lesions are T2 hyperintense, are generally T1 hypointense, and show “bubbly” appearance. Up to a third of lesions can show enhancement, generally nodular in morphology. Thin hyperintense rim on FLAIR images (seen in nearly three-fourths of cases) and high ADC values are other useful imaging features. Cystic changes are occasionally seen. Calcification can be seen but is rare.
Associated cortical dysplasia is common.
These tumors generally do not show growth. Surgical resection is for seizure control and is curative.
The histologic picture can occasionally be confusing; it is important to suggest the diagnosis based on
preoperative imaging

Question 77

DNET: Ddx

Answer 77

Ganglioglioma: Cystic lesion with enhancing nodule is typical. Unlike DNET, calcification is common. Contrast enhancement is also more common in ganglioglioma.
Cortical dysplasia: Relatively non–mass-like appearance, cystic foci are unusual.
Low-grade astrocytoma: Tend to be centered in the white matter. Overlying bony change is unusual.
May appear ill defined.

Question 78

Medulloblastoma: Epidemiology

Answer 78

Medulloblastoma is the most common malignant pediatric brain tumor, but may also occur in adults. It is considered a primitive neuroectodermal tumor of the posterior fossa. Together with pilocytic astrocytoma, it forms the bulk of posterior fossa tumors in children. A majority of the tumors are seen in the first decade, the peak being 5 to 7 years of age. A small percentage of these tumors is seen with genetic tumor syndromes (Gorlin syndrome, Turcot syndrome, Li-Fraumeni syndrome, ataxia telangiectasia, Coffin-Siris syndrome).
Several histologic subtypes of medulloblastoma have been identified, the most common type being classic medulloblastoma. The other subtypes include desmoplastic/nodular medulloblastoma,
medulloblastoma with extensive nodularity, large cell medulloblastoma, anaplastic medulloblastoma, and
much rarer variants of medullomyoblastoma and melanotic medulloblastoma.
The majority of the tumors are in the midline involving the vermis. The inferior medullary velum thought to be the primary site of origin. Hemispheric location is more commonly seen in the older age group and shows a higher incidence of desmoplastic variety. Less commonly, the tumor can be purely intraventricular. Most of the tumors appear fairly circumscribed with surrounding edema. Hydrocephalus is a common feature.

Question 79

Medulloblastoma: Imaging features

Answer 79

On CT, these tumors are hyperdense related to high cellularity. On MRI, the lesions are T1 isointense
and generally show intermediate to low signal on T2. Diffusion restriction is a key feature and is seen in
95% of tumors. Cysts if present are smaller in size, as opposed to pilocytic astrocytoma. About twothirds show moderate to intense contrast enhancement. In rest, the enhancement can be streaky, marginal,
or minimal.
Over a third of patients have CSF dissemination at the time of initial diagnosis. Contrast-enhanced MRI with diffusion-weighted imaging is the investigation of choice. Screening of the spine is routinely done at initial presentation.
If prominent dural calcifications are present, the patient should be investigated for Gorlin syndrome, which has treatment implications, and radiation may be avoided. Spectroscopy shows elevated choline to NAA ratio, occasionally elevated lipid/lactate and characteristic taurine peak at 3.35 ppm in short TE spectrum.
The combination of surgery and radiotherapy is the common treatment. Survivors have an increased
risk for secondary malignancies (meningioma, basal cell carcinoma, glioblastoma, thyroid cancer,
cervical cancer, uterine cancer, and acute leukemia) attributable to radiotherapy/chemotherapy.

Question 80

Pilocytic astrocytomas: Epidemiology

Answer 80

Pilocytic astrocytoma (PA) is the most common pediatric primary brain tumor. They are grade I tumors with excellent prognosis and mostly manifest in the first two decades of life. In children, the cerebellum, optic nerve chiasm, and hypothalamic regions are the most common locations, in that order. In adults, the tumor is more common in cerebral hemispheres.
Optic–hypothalamic pilocytic astrocytomas have known association with NF1.

Question 81

Pilocytic astrocytomas: Imaging features

Answer 81

Imaging features vary with tumor location.Posterior fossa PA commonly arises from the vermis or the hemisphere, and typical morphology is cystic lesion with solid enhancing portion (size can vary from a small mural nodule to being the predominant component). They are generally well circumscribed, and the enhancing nodule tends to be away from the pial surface (unlike hemangioblastoma). Surrounding edema is generally absent or small.
The nodule is T1 hypointense, T2 hyperintense, and mildly hypodense on CT and shows intense
enhancement. The enhancement in cyst wall varies from none to moderate.
Optic–hypothalamic and tectal PAs are generally solid, infiltrating, and less well marginated; the contrast enhancement is variable. The tumors anterior to the chiasm tend to be iso- to less T2 hyperintense and show no/minimal enhancement, and chiasmal and posterior optic pathway tumors tend to be T2
hyperintense and show more intense enhancement and these occur in adolescent and young adults. The
tectal PAs are nonenhancing.
Though these are grade I tumors and curable whenever the surgery is feasible, they sometimes show
alarming imaging features, but still with a benign course.

Question 82

Pilocytic astrocytomas: ddx

Answer 82

Posterior fossa PA:
Medulloblastoma—generally more solid tumor. Diffusion restriction is a key feature.
Ependymoma—located in the region of the fourth ventricle and has “toothpaste” morphology extruding
through the outlet foramina. Calcification and hemorrhage are common.
Hemangioblastoma—the enhancing nodule is generally based on the pia. This is an adult tumor. Also, nown association with von Hippel-Lindau disease.
Hypothalamic PA:
Pilomyxoid astrocytoma; tends to occur in younger children; hemorrhage is common and shows a more
aggressive appearance.
Hemispheric PA:
Other lesions with cystic–solid morphology (ganglioglioma, pleomorphic xanthoastrocytoma)

Question 83

SEGA: Epidemiology

Answer 83

Subependymal giant cell astrocytoma (SEGA) is a grade I localized tumor that happens in about 15% of tuberous sclerosis (TSC) patients. It can rarely be seen on non-TSC patients as well.
Subependymal giant cell tumor is probably a better term as these are of mixed glioneuronal lineage.
The classic location is caudothalamic groove at the foramen of Monro, thought to arise from the
subependymal nodule of TSC. These tumors can be asymptomatic or present with obstructive
hydrocephalus. There is a wide range for age of presentation, the mean being 11 years. They tend to show slow growth. There is an intact ependymal lining, which makes CSF seeding unlikely.
The major differential is hamartomatous subependymal nodule of TSC. Size of over a centimeter favors SEGA. Enhancement and calcification are seen in both the entities. Growth is an indicator of tumor. The enhancing nodules at the foramen of Monro need to be followed up to assess growth, the presence of which would indicate SEGA

Question 84

SEGA: imaging

Answer 84

The mass is iso- to hypodense on CT, hypointense on T1 images, and hyperintense on T2 images.
Calcification is common. The tumor shows avid contrast enhancement. Circumscribed tumor is the rule; rarely, there can be invasion of adjacent structures. Gradient sequence helps in visualization of calcified
subependymal nodules, and FLAIR sequence is extremely useful in demonstrating the rest of TSC
stigmata

Question 85

Signs of extra-axial lesions

Answer 85

The definitive signs of extra-axial location are
- CSF cleft between the mass and the brain
- Superficial vessels between the mass and the brain
- Dura between the mass and the brain
Multiplanar or 3D T2-weighted sequences are extremely helpful in demonstrating these definitive
signs.
Suggestive signs are as follows:
- Broad base toward the calvarium/dura
- Changes in the overlying bone
- “Dural tail” sign
- Apparent brain displacement from the calvarium/dura
Caution should be exercised while making the distinction solely based on these suggestive signs.
Many of the superficial intraaxial masses can exhibit these signs

Question 86

Choroid plexus papilloma: Epidemiology

Answer 86

Choroid plexus papillomas (CPP) and carcinomas (CPC) constitute 0.4%–0.6% of all intracranial neoplasms, most commonly seen in the pediatric population. The most common sites for CPP and CPC are in the lateral ventricles (50%), fourth ventricle (40%), and third ventricle (5%), with 5% in more than one location. Rarely, CPP and CPC may be found in an extraventricular site. The age range for fourth ventricle location is wide, 0 to 50 years of age, most commonly in males. Similar to the ones in other locations, they usually present as avidly enhancing lobulated masses with a cauliflower-like appearance, with associated cysts, and hemorrhage. Parenchyma invasion and necrosis may suggest CPC over CPP; however, this diagnosis is many times difficult even on histology. Some reports support that MR spectroscopy demonstrating increased choline, decreased N-acetylaspartate (NAA), and increased lactate should support carcinoma. CPP and CPC may produce CSF, which contributes to hydrocephalus.

Question 87

Choroid plexus papilloma: ddx

Answer 87

Ependymoma is typically seen in children with a mean age of 6 years. It arises from the floor or roof of the fourth ventricle and frequently extends through the foramina of Luschka andMagendie with a “toothpaste” appearance. Blood products and calcifications are often associated. They may be WHO grades II or III and are prone to recurrence. The majority of subependymoma are WHO grade I, occur in the fourth ventricle, occur in males older than 15 years, and are commonly asymptomatic.
They are usually slow-growing, avascular neoplasms, in which gross surgical resection is usually curative. Subependymoma may be associated with cysts, calcifications, or hemorrhage, and may present
variable behavior postcontrast, from absent to minimal to intense enhancement. Metastasis to the choroid plexus is rare, with incidence between 0.9% and 4.6%, most commonly secondary to renal cell carcinoma and lung cancer, followed by melanoma, gastric and colon carcinoma, and lymphoma. Intraventricular
meningiomas are rare, even more so when arising in the fourth ventricle. On MR spectroscopy, decreased
N-acetylaspartate (NAA) and creatinine, increased choline, and variable lactate and lipids may be seen,
with the presence of alanine thought to be more characteristic

Question 88

ATRT

Answer 88

A hyperdense mass on CT with associated restricted diffusion should lead to the differential diagnosis
of small blue cell tumor. This is a result of hypercellularity, with big nuclei and scant cytoplasm leading resulting in high nuclear-to-cytoplasmic ratio. For the same reasons, there is commonly associated T2 hypointensity. This category of tumors include lymphomas, germinomas, medulloblastomas, Ewing
sarcoma, rhabdomyosarcoma, neuroblastoma, and ATRT. Small cell lung cancer and meningioma can alsopresent with restricted diffusion. Glioblastomas may present with restricted diffusion in areas of
hypercellularity.
ATRT are typically pediatric tumors, of embryonal origin, usually diagnosed before age 5. This is a highly aggressive malignant neoplasm, rarely seen in adults. Ninety-five percent of the tumors occur in the
posterior fossa of children; however, they may be found in any location throughout the brain and spine.
When large tumors are seen in the supratentorial compartment, a thick, wavy heterogeneously enhancing wall surrounding cystic portions of the mass has been described. When small, they may be circumscribed.
MR spectroscopy reports describe increased choline and decreased N-acetylaspartate (NAA). Described cases in the literature are usually case reports or small series, and there has been suggestion for a distinct clinicoradiologic entity involving cranial nerve III in young infants.
Prognosis is dismal despite radiation, when feasible, and chemotherapy

Question 89

ATRT: Ddx

Answer 89

Lymphomas rarely present with hemorrhage prior to treatment.
Schwannoma of the third cranial nerve is usually well circumscribed and slow growing.

Question 90

Lhermitte Duclos: Imaging features

Answer 90

Lhermitte-Duclos disease (LDD) or dysplastic gangliocytoma is considered a WHO grade I
dysplastic gangliocytoma of the cerebellum. It may be part of Cowden syndrome, which is an autosomal
dominant neoplastic syndrome associated with mucocutaneous lesions, systemic hamartoma, and
malignant neoplasms of the breast, thyroid, and genitourinary and gastrointestinal tracts. It is associated with phakomatoses, multiple congenital malformations including hamartoma in the brain or body, malformations of cortical development, and meningiomas. LDD was described in 1920; however, it has been called by different names since then, such as ganglioneuroma of the cerebellar cortex, purkinjoma, and cerebellar hamartoma. It presents in young adults, but may be seen at any age

Question 91

Lhermitte Duclos: Imaging findings

Answer 91

Symptomatic cases may present with ataxia, nausea, vomiting, and hydrocephalus. A T1-hypointense,
T2-hyperintense nonenhancing expansile mass is seen, which may infiltrate the brainstem and cause mass
effect on the fourth ventricle with hydrocephalus. A tigroid pattern is very typical and should lead to the
diagnosis.

Question 92

Lhermitte Duclos: ddx

Answer 92

Low-grade glioma, although the striated pattern is very unusual for this entity.
Additional consideration is, pseudotumoral hemicerebellitis (PTHC) is a transitory inflammatory process of with T1-hypointense and T2-hyperintense signal abnormality of the involved unilateral cerebellar hemisphere with associated mass effect. The characteristic foliar pattern, infiltration of the brainstem, and presence of other malformations of cortical development or hamartoma in the brain or body favor LDD.
Pial enhancement outlining the cerebellar folia favors PTHC. Enhancement of vessels in between the cerebellar folia may be seen in LDD. Increased choline levels are described in PTHC; however, choline levels are normal or decreased in LDD. Lactate may be present in LDD. Follow-up with resolution of T2 hyperintensity and atrophy in PTHC is seen over weeks or months.

Question 93

Subependymoma: Epidemiology

Answer 93

Subependymoma is a benign slow-growing WHO grade I neoplasm of ependymal origin; the
majority are intraventricular in location, commonly seen in patients who are older than 15 years of age.
These lesions may be incidentally discovered in asymptomatic patients or be symptomatic usually
because of obstruction to CSF flow.
Rarely, these are extraventricular parenchymal in location. Those lesions are very difficult to
differentiate from low-grade glioma and often misdiagnosed as such.
These can be managed with surgical total or partial resection with microsurgical techniques with
excellent prognosis. Typically, the surgical goal is restoration of CSF flow because these lesions do not
have an aggressive or invasive nature.

Question 94

Subependymoma: Imaging features

Answer 94

On CT, these lesions are iso- to hypoattenuating, well circumscribed, with most of them having a
cystic component. Occasionally, they may have calcification or hemorrhage although not as common as the microcysts. These lesions show variable, but typically mild to no enhancement on postcontrast T1w MRI.
Occasionally, moderate heterogeneous enhancement may be seen.

Question 95

Subependymoma: Ddx

Answer 95

Ependymoma; although both may have cystic foci, ependymoma tends to havemore intense heterogeneous enhancement with frequent coarse calcifications. Unlike subependymoma, these lesions can invade adjacent parenchyma, are prone to CSF seeding, and may be associated with vasogenic edema within adjacent brain.
Central neurocytoma; these can also be seen around the Monro foramen but tend to have a speculated
peripheral margin, bubbly lobulated appearance, and moderate to intense enhancement.
Low-grade glioma; these lesions show none to minimal enhancement similar to subependymoma; however, microcystic pattern is less common in these lesions.
Medulloblastoma; this is a differential for lesions in the fourth ventricle; however, typically more intense enhancement and restricted diffusion are seen in medulloblastoma.

Question 96

PXA: Epidemiology

Answer 96

Pleomorphic xanthoastrocytoma (PXA); the lesion shown here is PXA, a rare WHO grade II neoplasm with primarily astrocytic differentiation and limited neuronal differentiation. It has a relativelygood prognosis and is seen commonly in children and young adults. It is commonly cortical superficial (subpial, with commonly pial contact seen) supratentorial lesion, most commonly seen in the temporal lobe.

Question 97

PXA: Imaging features

Answer 97

On MRI, this can be cystic, solid, or mixed in morphology with intense enhancement of the solid
component on postcontrast T1-weighted sequences. The degree of peritumoral edema is variable, with
most slow-growing lesions showing none to little peritumoral edema. It is notable here that presence of
peritumoral edema alone does not necessarily confer an aggressive nature to the tumor

Question 98

PXA: ddx

Answer 98

Differential Diagnosis includes ganglioglioma, gangliocytoma, and DNET and pilocytic astrocytoma.
Both ganglioglioma/gangliocytoma are more likely to have little to no peritumoral edema and more likely to have macroscopic calcification compared to PXA.
Other than the optic chiasm location of pilocytic astrocytoma, it is frequently infratentorial as opposed
to PXA, which is most commonly supratentorial and hemispheric in nature.
DNET may also have a similar appearance; presence of associated cortical dysplasia may help in differentiating it from PXA.
Complete surgical resection is the mainstay for treatment with favorable prognosis and low rate of recurrence. Adjuvant postoperative chemotherapy may be considered for patients with subtotal or partial
resection.