neuroradiology Flashcards
Describe the transmantle sign and its diagnosis
High T2/FLAIR signal extending from the ventricle to the cortex. Seen in focal cortical dysplasia, almost always type 2.
joubert syndrome CNS findings and extra-CNS associations
CNS findings:
bat wing 4th ventricle - elongated appearance of 4th ventricle resembles bat with wings outstretched. due to absent vermis and apposed cerebellar hemispheres
molar tooth sign - elongated superior cerebellar peduncles give the midbrain a molar tooth appearance. Results from lack of normal decussation of superior cerebellar peduncular fiber tracts.
Small dysplastic or aplastic cerebellar vermis
Abnormal inferior olivary nucleus
Dysplasia and heterotopia of cerebellar nuclei
Associations:
coloboma retinal dysplasia (50%) nephronopthisis multicystic dysplastic kidneys (30%) hepatic fibrosis polydactyly (15%)
What is Ddx of cerebral ring enhancing lesions? (Mnemonic)
DR MAGIC L
D: demyelinating disease R: radiation necrosis or resolving haematoma M: metastasis A: abscess G: glioblastoma I: infarct (subacute phase) C: contusion L: lymphoma
Name the syndrome:
supranuclear vertical gaze disturbance cause by compression of the tectal plate.
Parinaud syndrome (dorsal midbrain syndrome)
most frequently due to a posterior commissure or pineal region mass
Contents of internal auditory canal
Facial nerve
Three components of the vestibulocochlear nerve:
Cochlear nerve
Superior vestibular nerve
Inferior vestibular nerve
Labyrinthine artery
Contents of foramen spinosum (3)
Middle meningeal artery
Middle meningeal vein
Meningeal branch of mandibular nerve
Key imaging feature of Chiari 2 malformation?
Extension of cerebellar tonsils/brainstem with small posterior fossa and myelomeningocele
What are the CNS imaging manifestations of NF1?
FASI: focal areas of signal intensity in deep white matter and basal ganglia or corpus callosum, areas of T2/FLAIR hyperintensity with no contrast enhancement
optic nerve glioma or optic pathway glioma (may manifest as enlarged optic foramen)
progressive sphenoid wing dysplasia
lambdoid suture defects
dural calcification at vertex
moya moya phenomenon (rare)
buphthalmos
Key imaging feature of Chiari 2 malformation?
Extension of cerebellar tonsils/brainstem with small posterior fossa and myelomeningocele
Describe the different types of focal cortical dysplasia (Blumcke classification)
Type I: focal cortical dysplasia with abnormal cortical lamination
a: radial cortical lamination
b: tangential 6-layer cortical lamination
c: radial and tangential cortical lamination
Type II: focal cortical dysplasia with dysmorphic neurons
a: without balloon cells
b: with balloon cells
Type III: architectural distortion of cortical layer
a: in temporal lobe with hippocampal atrophy
b: adjacent to glial or glioneuronal tumor
c: adjacent to vascular malformation
d: adjacent to other lesions acquired in early childhood
What are the MRI findings in limbic encephalitis
Most cases may not have positive imaging findings
Typical findings:
Bilateral (60%) medial temporal lobe and limbic system involvement.
Cortical thickening and hyperT2/FLAIR in these regions.
Patchy enhancement.
Diffusion restriction is uncommon (unlike herpes encephalitis)
What is the boundary between:
the parietal and temporal lobes the parietal/temporal and the occipital lobes?
The boundary between the parietal and temporal lobes lies on a line extended back from the lateral sulcus.
The parieto-occipital sulcus seperates parietal and occipital lobes however it is only present on the medial surface. On the lateral surface, the parietal/temporal lobes are seperated from the occipital lobe by a line between the superior border of the parieto-occipital sulcus and the preoccipital notch
Where is Broca’s area located?
In the pars opercularis and pars triangularis of the inferior frontal gyrus of the dominant hemisphere.
Brodmann 44 and 45
Where is the cingulate gyrus located (and what seperates it from adjacent structure)?
The cingulate gyrus extends along the medial surface of the frontal to parietal lobes.
It is seperated from the corpus callosum by the callosal sulcus and from the medial surface of the frontal/parietal lobes by the cingulate sulcus
What are the structures of the mesial temporal lobe? (5)
amygdala hippocampus uncus dentate gyrus parahippocampal gyrus
True or false: The normal pineal gland enhances post contrast administration
True
It does not have a blood-brain barrier.
What is the normal thickness of the pituitary infundibulum?
Up to 3.8mm at the optic chiasm
Up to 2.7mm at the pituitary gland
What is the differential diagnosis of subependymal nodules? (4)
Tuberous sclerosis
Heterotopic gray matter
TORCH infection
Metastatic disease
What are MR characteristics of cortical tubers?
Prior to myelination:
T1 hyperintense
After myelination:
Variable T1
T2 hyper
What is PML?
Progressive multifocal leukoencephalopathy
Demyelinating disease which occurs due to the JC virus infecting oligodendrocytes.
Strongly associated with immunocompromised states.
What are the MR findings of PML?
Bilateral asymmetric periventricular andsubcortical multifocal demyelination.
U-fibers commonly involved. There is a predilection for the parieto-occipital regions.
No mass effect
T2 bright
T1 hypo
Enhancement uncommon
Diffusion restriction is present
Where is Broca’s area located?
Where is Wernicke’s area located?
Broca’s area is in the frontal operculum.
Wernicke’s area is in the superior posterior temporal lobe.
What are the major branches of the maxillary artery?
Middle meningeal artery Accessory middle meningeal artery Descending Palatine artery Facial, sinus and nasoorbital branches Sphenopalatine, infraorbital, posterior superior alveolar, artery of the vidian canal
What white matter disease distribution is characteristic of early CADASIL?
Anterior temporal lobe
External capsule
Which foramina contain each branch of CN5?
The ophthalmic, maxillary and mandibular branches leave the skull through three separate foramina: the superior orbital fissure, the foramen rotundum and the foramen ovale, respectively
What is the arterial supply of the medulla oblongata?
PICA supplies the lateral aspect of the medulla
anterior spinal artery supplies the entire medial aspect
direct branches of the vertebral artery supplies an area between the other two main arteries
What are the common causes of stroke in a young patient and in a child?
younger patient
Emboli
Arterial dissections
Vasculopathy (FMD, vasculitis)
Drug abuse
child
Emboli from congenital heart disease
Venous thrombosis
Blood dyscrasias (i.e., sickle cell disease)
What are the manifestations of NF2?
MIS ME:
Intracranial schwannomas (bilat IAC schwannomas are diagnostic of NF2)
Meningiomas
Spinal ependymomas
Can also be associated with syringomyelia and cataracts
Describe the McDonald diagnostic criteria
criteria for MRI diagnosis of multiple sclerosis
Dissemination in space:
requires ≥1 T2 bright lesions in two or more of the following locations 1:
periventricular
juxtacortical
infratentorial
spinal cord (exclude if pt has brainstem/spinal cord syndrome)
Dissemination in time:
A new lesion not present on prior MR
2 lesions, a symptomatic lesion with enhancement and another T2 bright lesion without enhancement.
What is the etiology of Wernicke encephalopathy?
Thiamine deficiency (vit B1), typically seen in alcoholics.
Can also be seen due to: starvation prolonged TPN w/o supplementation post bariatric surgery hyperemesis gravidum gastrointestinal malignancy chronic dialysis
What are the MR imaging findings of Wernicke encephalopathy?
Symmetric (bilateral) T2/FLAIR hyper in the: mamillary bodies dorsomedial thalami tectal plate periaqueductal area around the 3rd ventricle
these regions can show contrast enhancement and diffusion restriction.
What is the classic clinical presentation of Wernicke encephalopathy?
Triad of ophthalmoplegia, ataxia and confusion
Synchronous pineal and suprasellar masses strongly suggest what pathology?
Germinoma
What are the characteristic imaging findings of a germinoma (pineal)?
CT hyperattenuating
MRI:
T2 iso to gray matter
+ve diffusion restriction
pineal calcifications are engulfed by the tumor (as opposed to exploded)
Look for synchronous pineal and suprasellar masses, CSF dissemination and invasion of adjacent parenchyma.
What is the typical MR imaging appearance of Lhermitte-Duclos disease?
A.K.A. dysplastic cerebellar gangliocytoma
Rare mass-like lesion in the cerebellar hemispheres.
Well circumscribed, T1 hypo, T2 hyper with parallel striated of gyriform architecture to the thickened folia (best on T2)
Enhancement and calcification rare
No restriction
What is the distribution of signal abnormality in heroin leukoencephalopathy?
Symmetric T2 hyper +/- restriction in:
posterior cerebral white matter splenium of corpus callosum posterior limb of internal capsule extending inferiorly into the pontine corticospinal tracts (characteristic) cerebellar peduncles cerebellar white matter
predilection for the corticospinal tract and medial lemniscus.
What is the typical location of a hypothalamic hamartoma?
Hypothalamic hamartomas arise from the tuber cinereum (floor of third ventricle).
Lack of enhancement and long-term stability favors this diagnosis.
They’re associated with gelastic seizures (uncontrollable laughter).
What is the differential diagnosis for basal ganglia T1 hyperintensity?
Mostly from deposition of T1hyper elements in the basal ganglia:
1- Calcium (idiopathic, calcium and phosphate abnormalities)
2- hepatic failure (wilson’s disease, hepatocerebral degeneration)
3- Toxins/ischemia (CO, long-term TPN [manganese], hyperglycemia, gadolineum chelates, global hypoxia)
4- Blood (methaemoglobin)
5- Japanese encephalitis
6- Hamartoma in NF1
7- kernicterus in neonates
What is the differential diagnosis for basal ganglia T2 hyperintensity?
LINT
1- Lymphoma
2- Ischemia (hypoxia, venous infarct)
3- Neurodegen/metabolic (wilson, huntington, Creutzfeldt-Jakob, methylmalonic acidaemia, mitochondrial diseases, extrapontine myelinolysis)
4- Toxins (CO, cyanide, hypoglycemia, methanol)
What is the etiology of progressive multifocal leukoencephalopathy and what group of patients are affected?
PML is a demyelinating process caused by the JC polyomavirus.
The virus is active in severely immunocompromised patients (AIDS, lymphoproliferative/myeloproliferative dissorders, immunosuppressive therapy, congenital immunodeficiency).
True of false:
MRI lesions due to progressive multifocal leukoencephalopathy involve primarily the white matter, are usually symmetric and nonenhancing.
FALSE
MRI lesions due to progressive multifocal leukoencephalopathy involve primarily the white matter, are usually ASYMMETRIC and nonenhancing.
Some involvement of grey matter structures is present in 50% of cases.
What finding involving the ventricles differentiates congenital cerebral enlargement (hemimegalencephaly) and acquired cerebral enlargement (edema, gliomatosis)?
In hemimegalencephaly, the ipsilateral ventricle is enlarged as well.
What MRI findings can be present in hemimegalencephaly?
Asymmetrically enlarged cerebral hemisphere and ipsilateral ventricle.
White matter abnormalities: advanced myelination, focal heterogeneous T1 signal.
Neuronal migration abnormalities (polymicrogyria, pachygyria, heterotopia)
Calcifications
May have secondary brain atrophy in later stages due to prolonged seizures.
Which pathology is the hot cross bun sign associated with?
Give other MRI findings
Multiple system atrophy
Other findings:
Cerebellar, middle cerebellar peduncle and pontine atrophy
Lateral putaminal linear t2 hyperintensity
Putaminal atrophy
What are the abnormalities and imaging findings of Sturge-Weber Syndrome?
It is a sporadic congenital syndrome consisting of:
- facial nevus flammeus (port wine stain)
- choroidal angiomas
- pial angiomatosis (ipsilateral to facial abnormalities)
Imaging findings:
- Gyriform calcifications
- pial angiomatosis
- Ipsilateral choroid plexus enlargement
- Eventually, progressive atrophy and gliosis due to chronic venous ischemia.
What is the differential diagnosis of bilateral symmetric striopallidodentate calcinosis in an adult?
Fahr disease
Hypoparathyroidism
Pseudohypoparathyroidism
Hyperparathyroidism
What is the most common type of low grade astrocytoma?
Mean age of presentation and most common presentation?
Imaging findings?
Fibrillary astrocytoma
Mean age of 35, 75% present with seizures
Imaging:
Majority located in supratentorial brain.
T1hypo T2hyper no significant enhancement
cysts and calcification are rare
What is the classic imaging appearance characteristic of cerebellar hemangioblastomas?
Cystic mass with an enhancing mural nodule
What is the boundary between the intra-axial and extra-axial space?
The pial surface
What is the cell of origin of meningioma
Arachnoid cap cell
What are the findings in a Chiari III malformation?
Chiari II
low occipital and/or high cervical meningo-encephalocele
TRUE OR FALSE
The presence of irregular vessels, with flow voids, allows you to differentiate a hemangiopericytoma (solitary fibrous tumor) from a meningioma
FALSE
Although helpful in differentiating the two, it is not sufficient to exclude a meningioma.
Give 3 findings that differentiate hemangiopericytoma from meningioma
No calcification
No hyperostosis
Tends to be lobulated
What are the imaging findings of idiopathic intracranial hypertension?
AKA pseudotumor cerebri
Posterior globe flattening (most specific) Optic nerve sheath distention Optic nerve tortuosity Pituitary deformity Empty sella Slit like ventricles Acquired tonsillar ectopia
(several other findings)
What are the complications of an intracranial abscess?
Choroid plexitis
Intraventricular rupture
- Abscess capsule is thinnest near the ventricle
- Often fatal
Leptomeningitis/Ependymitis
Development of daughter abscessesWhat MRI features allow differentiation between GBM and intracranial abscess?
A cystic lesion that markedly restricts centrally is an abscess until proven otherwise, although GBM can sometimes centrally restrict.
Other findings:
GBM has thick nodular capsule
Abscess has thin regular capsule
Intermediate to low T2 signal capsule favors abscess
Restricted diffuse of enhancing wall favors GBM
Multiple similar rounded lesions at the grey-white matter junction favors abscess
irregular mass with adjacent secondary lesions embedded in the same region of ‘oedema’ favours GBM
Extensive edema to lesion size favors abscess
TRUE OR FALSE
Lentiform nuclei involvement is typical of early HSV encephalitis
FALSE
The lentiform nuclei are usually spared
What is the causative agent in progressive multifocal leukoencephalopathy?
In immunocompromised patients, it is caused by reactivation of the JC (John Cunningham) virus.
TRUE OR FALSE
In cases of progressive multifocal leukoencephalopathy, there is mass effect on the adjacent sulci because of the edema.
FALSE
PML is a demyelinating process and there is no mass effect on the adjacent sulci. When evaluating white matter abnormality in immunocompromised patients, it is important to assess the adjacent sulci for the presence of mass effect.
What are the MRI features of neurotoxoplasmosis?
Presents in immunocompromised patients
Multifocal ring-enhancing masses at the gray matter-white matter junction
involvement of the basal ganglia and thalami
periventricular involvement
generous surrounding vasogenic edema
T1: iso-hypo
T2: iso-hyper
G+: ring enhancement
What are the imaging findings of progressive multifocal leukoencephalopathy?
Presents in immunocompromised patients
Confluent, bilateral, asymmetric supratentorial white matter and thalamic involvement.
Also involves U-fibers.
T1 hypo T2 hyper No mass effect No enhancement Restricts on DWI
How do you differentiate retinal from choroidal detachment on imaging?
In retinal detachment, the detachment is limited anteriorly by the ora serrata, compared to the choroidal detachment that is not limited and extends beyond it.
The ora serrata marks the junction between the retina and the ciliary body. It is located anteriorly bilaterally, approximately 10 and 2 o’clock
In retinal detachment, the detachment converges posteriorly on the optic disc, compared to the choroidal detachment that diverges at the disc.
What is the most common etiology of leukocoria in children?
Retinoblastoma, almost all present <6 years of age
What is Tolosa-Hunt syndrome?
Tolosa-Hunt syndrome (THS) is an idiopathic inflammatory condition that involves the cavernous sinus and orbital apex, and is essentially a clinical diagnosis of exclusion.
