Brain 2 Flashcards
Imaging findings of an extra-axial mass
- Buckling of the white matter
- dural base
- expansion of adjacent subarachnoid spaces
- csf cleft sign
- displacement of vessels
is a meningioma intra or extra dural
extra-axial intra-dural
Imaging findings of an intra-axial mass
- expands cortex of brain
- no expansion of the subarachnoid space
- vessels seen peripheral to the mass
- spreads along well defined boundaries
90% of meningiomas occur _______
supratentorially. parasagittal dura and convexities most common locations
Typical MRI signal characteristics of meningioma
must be extra-axial hypo-iso T1, iso-hyper T2, avid contrast enhancement cleft sign dural tail MRS: High alanine, absent NAA
Meningioma vs pituitary adenoma: which one narrows the ICA?
Meningioma. A pituitary adenoma will surround the ICA but almost never narrow it.
Causes of intraparenchyma edema secondary to meningioma
- venous stasis
- compressive ischemia
- aggressive growth
- parasitization of pial vessels
- venous occlusion
meningiomas adjacent to brain parenchyma are more likely to cause edema
Typical location for intraventricular meningioma?
Trigone of the lateral ventricle (typically left) around the choroid plexus (80%)
15% third ventricle, 5% fourth ventricle
How to differentiate benign from malignant meningioma (3)
- Faster rate of growth
- Intraparenchymal invasion
- Increased diffusion restriction compared to benign meningiomas
What is the mean latency period for radiation induced meningioma?
Approximately 35 years
must arise in the radiation field
What is the effect of a hemangiopericytoma on the adjacent bone?
Bone erosion
No hyperostosis
How to distinguish meningioma from vestibular schwannoma (7)
- Meningioma has a dural tail
- Vestibular schwannoma has acute angle /w petrous bone (80%) vs obtuse for meningioma
- Vestibular schwannoma can be very bright on T2
- 7-10% vestibular schwannoma also has arachnoid cyst
- Vestibular schwannomas can show microhemorrhage of SWI, absent in meningioma
- Vestibular schwannomas expand the IAC, unusual for meningioma
- 90% of purely intracanalicular lesions are vestibular schwannomas
Typical MRI appearance of vestibular schwannoma (2)
- slightly hypo to isointense to pons on all sequences
- almost always enhance, homogeneous 70%
Calcification and dural tail extremely rare
cyst/necrosis uncommon (10%)
Which cranial nerve is most commonly affected by a schwannoma? Name the most common branch
CN VIII, superior vestibular branch
other common: inferior vestibular branch, CN VII, CN V
Imaging difference between jugular schwannoma and paraganglioma (glomus jugulare tumor)? Specifically bone and vascular (2)
- They both erode the adjacent bone but in jugular schwannoma it is smooth and sclerotic vs irregular and non-sclerotic
- jugular schwannoma compresses the vein, paraganglioma invades the vein
Typical primaries to give dural metastases? (5)
- breast most common purely dural
- Lung
- prostate
- melanoma
- lymphoma but sometimes dural lymphoma is primary
IN CHILDREN:
- adrenal neuroblastoma
- leukemia
Most common non-CNS malignancies to seed the CSF? (3)
- breast
- lung
- melanoma
Classification for cystic meningiomas? (4 types)
Type 1: cyst in center of meningioma
Type 2: cyst in periphery of meningioma (intra-tumoral)
type 3: cyst in adjacent brain
type 4: cyst between tumor and brain (arachnoid cyst)
What syndrome is subependymal giant cell astrocytoma associated with?
give WHO grade
Tuberous sclerosis
On pathology, SEGA and subependymal nodule of TS are indistinguishable
WHO grade 1
What is l’hermitte-duclos disease and what are the imaging findings?
What is the usual age of presentation?
give WHO grade
Dysplastic cerebellar gangliocytoma
Disorder of the normal cerebellar laminar cytoarchitecture
WHO grade 1
Cerebellar mass usually in hemisphere lowT1 highT2 in an alternating striated pattern (thickened cerebellar folia)
No enhancement
Usually non calcified but can have scattered calcification
Usually occurs in the third and fourth decades
What is the histological difference between gangliocytoma and ganglioglioma?
They both contain neoplastic neuronal cells.
They both also contain glial cells, which are anaplastic in gangliogliomas, whereas gangliocytomas contain normal nonneoplastic glial cells.
True or false:
Calcification and cyst formation is a frequent finding in gangliocytomas
give WHO grade
True
They also frequently enhance
They have variable T1 and T2 signal
WHO grade 1
Which phakomatosis is L’hermitte-Duclos disease associated with (describe it)?
Cowden Syndrome (multiple hamartoma syndrome)
Rare autosomal dominant inherited disorder characterized by multiple hamartomas
Other diseases associated with lhermitte-duclos disease:
- disorders of cortical formation (megalencephaly, grey matter heterotopia, polymicrogyria)
- polydactyly
- hydromyelia
- macroglossia
- localised gigantism
What is typical location of central neurocytoma?
What is CT/MR appearance?
give WHO grade
WHO Grade 2
Typically located in the lateral ventricles near the foramen of Monro with characteristic attachment to the septum pellucidum
inhomogeneously T1 isointense
Iso-hyper T2
about half contain calcium. Can contain cysts, hemorrhage and vessels
enhances
iso to hyperdense on CT
What is imaging ddx of central neurocytoma?
other intraventricular tumors that occur in young adults:
oligodendroglioma
SEGA
low-grade/pilocytic astrocytoma
ependymoma
What is a ganglioneurocytoma?
give WHO grade
rare variant of central neurocytoma that is characterized by differentiation toward ganglion cells.
WHO grade 2
Frequently forms a cystic lesion, frequently arises extraventricularly
What is the classical appearance of a ganglioglioma?
Also give other imaging findings
give WHO grade
Ganglioglioma is rare but remains most frequent of the neuronal-glial CNS neoplasms. WHO grade 1
Cystic mass with a mural nodule (40%). Temporal lobe is most affected region
Most gangliogliomas occur in children and young adults
other imaging findings:
calcification (30%)
scalloped pressure erosion of the overlying calvaria (slow growth)
variable enhancement (nonenhancing, ringlike, intense homogeneous)
usually little mass effect/vasogenic edema
What is DNET? Give WHO grade
Imaging appearance?
Dysembryoplastic neuroepithelial tumour
mixed neuronal-glial neoplasm characterized by multinodular architecture and predominantly intracortical location
WHO grade 1
Hypodense cystlike lesion
hypoT1
markedly hyperT2 with soap bubble apperance
enhancement is not a prominent feature but can be present
calcification
What is typical location and appearance of oligodendroglioma
Give WHO grade
WHO grade 2 glial tumor (grade 3 if anaplastic)
85% are supratentorial, involving white matter and cortex. Most commonly in frontal lobes.
hypo/isodense
hypoT1
hyperT2
no diffusion restriction
70-90% contain calcification
50% enhance, variable degree
What happens to the calcification of a pineal gland in a pineal parenchymal tumor?
Pineal parenchymal tumors expand and obliteral pineal architecture, “exploding” the normal pineal calcification towards the periphery
What is typical CT/MR appearance of pineocytoma? Give WHO grade
WHO grade 1
Well demarcated, usually
When a pineoblastoma is present or suspected, what other imaging is required?
CSF dissemination is a common finding (most common cause of death) and necessitates imaging of the entire craniospinal axis.
For pineoblastoma:
1- What is most common age of presentation?
2- WHO grading?
3- What differentiates it from pineocytoma on imaging?
1- first 2 decades of life, but can occur at any age
2- WHO grade IV
3-
Typically >3cm
poorly circumscribed
solid portion on MR similar to pineocytoma
heterogeneous in appearance because of necrosis and hemorrhage (hemorrhage rare in pineocytoma)
heterogeneous enhancement
extensive cystic change is rare
may restrict on DWI
CSF dissemination common (rare in pineocytoma)
almost all have hydrocephalus
parenchymal involvement
What are the typical locations of an intracranial ependymoma?
Usually in the posterior fossa (60%), arising from the floor of the fourth ventricle and insinuating itself into the foramen of luschka and magendie.
In 40% of cases it is supratentorial, with half of those being intraparenchymal.
What is the orbital septum?
The orbital septum is a thin sheet of fibrous tissue that originates from the orbital rim periosteum and blends with the tendon of the levator palpebrae superioris superiorly and inserts into the tarsal plate inferiorly.
The orbital septum separates the intra-orbital fat from eyelid fat and orbicularis oculi muscle, and also provides a barrier against spread of infection between the preseptal space to postseptal space.
What is the most common cause of orbital cellulitis?
Paranasal sinusitis
TRUE OR FALSE
Bone destruction is not usually seen in orbital cellulitis secondary to spread of paranasal sinusitis.
TRUE
The infection spreads to the orbit via a perivascular pathway, not direct spread through the bone.
When assessing a patient with orbital cellulitis, what complications should you look for?
Orbital subperiosteal abscess (intraconal abscess)
venous sinus thrombosis
- cavernous sinus
- superior ophthalmic vein
bacterial meningitis
epidural/subdural abscess
parenchymal brain abscessWhat are the imaging findings of CMV induced retinitis
Presents in patients with UNTREATED HIV
Uveal enhancement
Retinal detachment
Calcifications in the retina
Starts in 1 eye and progresses to the contralateral eye
If untreated, leads to blindness.
Name this pathology:
Complication of acute sinusitis characterised by subperiosteal abscess and osteomyelitis, usually related to the frontal sinus but sometimes also related with the mastoid.
Pott’s puffy tumor.
Forehead swelling is seen, which explains the name of this pathology.
Other rare causes, besides sinusitis, are trauma, intranasal cocaine/methamphetamine abuse and craniotomy.
What are the imaging findings in Graves ophthalmopathy?
Bilateral involvement (unilateral poss.) Enlargement of the extra-ocular muscles with sparing of the tendinous insertions (IM SLO) Increased orbital fat Lacrimal gland enlargement Eyelid edema Stretching of the optic nerve Tenting of the posterior globe
On MRI, what is the difference between acute and chronic optic neuritis?
Acute optic neuritis: T2 hyperintense, enlarged and enhancing nerve.
Chronic optic neuritis: T2 hyperintense, atrophic non-enhancing nerve.
Name this pathology:
Thickening and enhancement of the optic nerve sheath on MRI
Perineuritis: Inflammation of the optic nerve sheath.
What are the MRI findings of cavernous sinus fistula?
Proptosis
Enlarged superior ophthalmic vein
Cavernous sinus distention
Cavernous sinus flow voids
What is the most common benign orbital tumor in adults?
Cavernous hemangioma
What underlying pathology should you search for in patients with retinal/choroidal detachment?
An underlying ocular mass such as:
- retinoblastoma in childrens
- uveal melanoma in adults
- metastases
What is a trochlear calcification?
It is an aging related normal finding. Superomedial location within the orbit. It represents calcification of the trochlea of the superior oblique.
What are scleral plaques?
They are typically seen in elderly patients. Incidental finding.
They are scleral calcifications located at the insertion sites of the medial and lateral rectus muscles.
What is optic drusen?
Benign incidental finding.
Punctate calcification near the optic disc.
What is phthisis bulbi?
Shrunken globe with ocular calcification or ossification. It is a sequela of infection, inflammation or trauma.
What is the key CT finding in corneal laceration?
Decreased volume of the anterior chamber, which appears as a diminished anterior-posterior dimension.
Carefully assess the position of the lens to ensure it is not an anterior lens subluxation.
What is nontraumatic lens dislocation associated with?
Systemic connective tissue disorders such as:
- Marfan syndrome
- Ehlers Danlos
Homocystinuria
Suspect a systemic cause if there is bilateral lens dislocation
What is a coloboma?
Focal congenital defect of the eye which can involve several structure such as the iris, lens, optic nerve insertion, etc.
A deep anterior chamber in the setting of trauma should raise the possibility of what kind of ocular injury?
Globe rupture. The finding is secondary to posterior dislocation of the lens, which can happen in the setting of a globe rupture.
An intracranial lesion with incomplete ring enhancement suggests what type of pathology?
Tumefactive demyelinating lesion
What is Devic’s disease?
Neuromyelitis optica (NMO), also known Devic’s disease, is a severe demyelinating disease caused by an autoantibody to aquaporin-4 water channel.
Classic presentation is with the triad of optic neuritis, longitudinally extensive myelitis and positive NMO-IgG.
What is ADEM?
Acute disseminated encephalomyelitis (ADEM) is featured by a monophasic acute inflammation and demyelination of white matter typically following a recent (1-2 weeks prior) viral infection or vaccination.
The imaging appearance can be identical to MS, but it is monophasic, not multiphasic like MS. ADEM most often presents in children and adolescents.
What causes Wernicke-Korsakoff syndrome?
Vitamin B1 deficiency (alcoholism most common)
What are the imaging findings of Wernicke encephalopathy?
T2/FLAIR: symmetrically increased signal intensity in mamillary bodies, dorsomedial thalami, tectal plate, periaqueductal area and around third ventricle.
Gado: contrast enhancement can also be seen in the same regions, most commonly of the mamillary bodies.
DWI/ADC: restricted diffusion can also be seen in the same regions
Mamillary body atrophy
What is the DDx of a long segment of demyelination of the posterior spinal column?
B12 vitamin deficiency
HIV myelopathy
Nitrous Oxide abuse
TRUE OR FALSE
Heroin leukoencephalopathy is caused by heroin inhalation, not injection.
TRUE
What is the bearded skull sign?
Demyelination of descending cortico-spinal tracts and bilateral cerebellar hemispheres. It is associated with heroin leukoencephalopathy
What is the characteristic distribution of heroin induced toxic leukoencephalopathy
AKA chasing the dragon. There is widespread white matter T2 hyper. Characteristic distribution:
- Symmetrical involvement of the posterior limb of the internal capsules extending inferiorly into the pontine corticospinal tracts, and superiorly into the peri-rolandic subcortical white matter
- Subcortical U-fibers are also usually spared
- Symmetrical butterfly wing pattern involvement of the cerebellar white matter
- Sparing of adjacent grey matter structures
What is the most common location of supratentorial ependymoma?
Intraparenchymal
What is the difference on imaging between ependymoma and subependymoma?
Ependymoma enhances more, subependymoma shows little enhancement
Ependymoma 0-20yr, subependymoma >40yr
Both arise most commonly in fourth ventricle
What percentage of developmental venous anomalies are associated with cavernous malformations?
30-50%
TRUE OR FALSE
Pial arteriovenous malformations are congenital
TRUE
What is the bleed risk per year of a pial arteriovenous malformation?
3% bleed risk per year
