Quick stuff Flashcards
Classification of the traumatic primary hemorrhages caused directly and immediately by the impact
- Epidural hematoma (arterial/venous) , more acute
- Subdural hematoma (Extra-axial), more chronic
- Intracerebral hematoma
- Intraventricular hemorrhage
- Subarachnoid hemorrhage
What can epidural and subdural hematoma be classified as?
Primary extra-axial traumatic injury
What causes epidural hematoma?
Caused by the tearing of (arterial) vessels (more often middle meningeal artery caused by trauma on the temporal or fronto-parietal bone) by depressed bone planks
Which preceding event is associated with development of epidural hematoma?
Almost always associated with
fractures
Epidural hematoma incidence bilateral vs unilateral
Generally, it is monolateral but it can exceptionally be bilateral but there would need to be 2 fractures on each side
Where does blood collect in epidural hematoma?
Blood collects between the internal skull surface and the outer layer of the dura mater (endosteal layer)
Location of epidural hematoma
- Supratentorial in 95% of cases
- Temporoparietal: 60%
frontal: 20%
parieto-occipital: 20%
How does epidural hematoma appear on CT scan?
- Hyperdense, somewhat heterogeneous, and sharply demarcated
- Hypodense areas in hyper-acute stage are indicative of active bleeding (not yet coagulated
Shape of epidural hematoma
Typically biconvex in shape (biconcave lens)
Which imaging for epidural hematoma
Both CT and MRI (rarely necessary and done0 are suitable to evaluate EDHs
How does epidural hematoma appear on MRI?
- Acute EDH appears isointense on T1 and shows variable intensities from hypo- to hyperintense on a T2 sequence
- Early subacute EDH appears hypointense on T2 while late subacute and chronic EDH are hyperintense on both T1 and T2 sequences
What causes subdural hematoma?
- Caused by the tearing of cortical veins, which are the ones connecting the Dural sinuses, adjacent to bone, with the small veins inside the brain parenchyma
- The blood accumulates in the subdural space (normally virtual) between the dura mater and the arachnoid
What event leads to subdural hematoma?
Mainly due to head trauma
Imaging choice for subdural hematoma?
CT is usually sufficient to make diagnosis
Bilateral vs unilateral subdural hematoma incidence?
- Most are unilateral in adults
- Most are bilateral in infants
Site of subdural hematoma
- They are mainly supratentorial (like epidural ones), staying along the frontoparietal area
- Frontoparietal convexities and the middle cranial fossa
Subdural hematoma appearance on CT
- The appearance of SDHs on CT varies with clot age and organization.
- Shift of the midline can be seen
- Hyperacute (first hour or so): relatively isodense to the adjacent cortex, with a swirled appearance due to a mixture of the clot, serum and ongoing unclotted blood
Acute: Crescent-shaped homogeneously hyperdense extra-axial collection that spreads diffusely over the affected hemisphere
Up to 40% of SDHs have mixed hyper- or hypodense areas that reflect unclotted blood, serum extruded during clot retraction, or CSF within the subdural hematoma due to an arachnoid laceration.
Subacute
typically 10-14 days, the density become isodense to the adjacent cortex, making identification potentially tricky. Contrast-enhanced CT is often useful in this instance if MRI is unavailable
Chronic (at least 3 weeks old): The subdural collection becomes hypodense to the adjacent cortex with possibility of reaching isodensity to CSF, and mimic a subdural hygroma.
Acute on chronic
What is acute on chronic subdural hematoma?
Acute on chronic subdural hematomas refers to a second episode of acute hemorrhage into a pre-existing chronic subdural hematoma. It typically appears as a hypodense collection with a hematocrit level (located posteriorly). A similar appearance can be seen in patients with clotting disorders or on anticoagulants
MRI subdural hematoma
Hyperacute
T1: isointense to grey matter
T2: iso- to hyperintense
FLAIR: hyperintense to CSF
Acute
T1: iso- to hypointense to grey matter
T2: hypointense to grey matter
FLAIR: hyperintense to CSF
CT findings subarachnoid hemorrhage
acute blood is hyperdense (bright) on CT
blood in the basal cisterns and sulci
What is the most common tumor of the meninges?
Meningiomas
What are meningiomas?
Non-glial neoplasm that originates from the meningocytes or arachnoid cap cells
How many subtypes of meningiomas exist?
15 subtypes
How do meningiomas appear on imaging?
Typical meningiomas appear as dural-based masses isointense to grey matter on both T1 and T2 weighted imaging enhancing vividly on both MRI and CT
Location of meningiomas
- Can occur anyhwere along meninges
- Most are supratentorial
Choice of imaging for meningiomas and why?
- MRI is the investigation of choice for the diagnosis and characterization of meningiomas
- Best imaged with MRI with contrast as this most accurately delineates the tumor, presence of intra- and trans-osseous extension and relationship to the underlying brain
- CT, however, is useful if bony anatomy is required (e.g. at the base of skull), when patients cannot have MRI, and especially when the meningioma is entirely ossified/calcified
Appearance of meningiomas on MRI
- Extra-axial masses with a broad dural base
- They are usually homogeneous and well-circumscribed, although many variants are encountered
correlates with the histological subtypes - T1: usually isointense to grey matter (60-90%)
hypointense to grey matter (10-40%): particularly fibrous, psammomatous variants - T1 C+ (Gd): usually intense and homogeneous enhancement
- T2: It seems that the signal intensity of meningiomas on T2-weighted images correlates with the histological subtypes. usually isointense to grey matter (~50%),
hyperintense to grey matter (35-40%) (microcystic, secretory, cartilaginous (metaplastic), chordoid and angiomatous variants),
hypointense to grey matter (10-15%) - Dural tail is seen in 60-72% (note that a dural tail is also seen in other processes)
- white matter buckling sign
Which intracranial intra axial tumor is most common?
Gliomas
Location of gliomas
1/2 are supratentorial, ¼ are infratent
Primary vs metastatic glioma incidence
60% or less are primary, 40% of them are metastatic.
WHO classification of gliomas
Four grades:
1- Pilocytic astrocytoma
2- Fibrillary astrocytoma
3- Anaplastic astrocytoma
4- Glioblastoma (glioblastoma multiforme represents 50% of all gliomas and 25% of primitive tumors of the brain
What can gliomas of the cerebral hemispheres be divided into?
Circumscribed (grade 1) and diffuse (or infiltrative)
What is included in circumscribed glioma?
Pilocytic astrocytoma, subependymal giant cell astrocytomas, and desmoplastic infantile ganglioma
What is included in the diffuse gliomas?
- Fibrillary astro-oligodendroglioma (and protoplasmic) grade II
- Anaplastic astro-oligodendroglioma (and gemistocytic) grade III
- Glioblastoma (GBM) grade IV (worse of all)
Purpose and targets of radiology in cerebral gliomas
Neuroradiological purpose and targets of cerebral gliomas are:
* Identification and localization for surgical treatment
* Extension evaluation
* Hypothesis on origin and grading
* Risk evaluation and neurosurgical options
* Follow-up after treatment. This is important to know whether the tumor remain stable
or there is evidence of regrowth.
Neuroradiological features of glioblastoma multiforme
- White matter localization (because it comes from the glial cells)
- Extremely heterogeneous MRI signal with central necrosis
- It shows hyperintense signal on T2-weighted image, but the peripheral portion shows
lower signal intensity. - It shows irregular margin and contrast enhancement, which tends to circumscribe the
necrosis. - Common features: various stages of hemorrhage (time framed), high vascularization,
and adjacent blood vessel dilation. - The use of PWI and DWI allow us to see increased cerebral blood volume and high
cellularity of solid components respectively. - The use of MRS shows elevated Choline and lactate/Lip (necrosis)
DTI usefulness in glioblastoma
see tumor’s influence on fiber tracts and plan for surgery
Differential diagnosis between grade 2 and 3 and 4 glioma
- The differential diagnosis between grade II astrocytoma and glioblastoma is easy and it’s based on: T2 signal, contrast enhancement and morphological characteristics. The difficult one is the differential diagnosis between grade II and grade III.
- We look for presence of contrast enhancement in tumors. When we find the glioma with contrast enhancement (as shown on the right), it’s generally grade III already.
- Up to 25% malignant gliomas without contrast enhancement can be seen. In some rarer cases low grade diffuse gliomas can show contrast enhancement.
- With the perfusion-weighted images, we see that blood uptakes on both sides are similar in benign tumor, but they are different in the malignant tumors (increased inner vascularization)
- Grade II gliomas perfusion will be stable over time.
Clinical importance of differentiating between grade 2 and 3 gliomas?
Important clinical impact: malignant gliomas need aggressive treatments, but low-grade gliomas, in young adult patients without neurologic signs, do not justify the risk for surgery.
Progressive supranuclear palsy
- The prevalent MRI finding is midbrain atrophy, with dilation and downwards expansion of the third ventricle.
- Flattening or concave outline to the superior aspect of the midbrain, which should be upwardly convex, and reduction of the roof thickness makes the “hummingbird” or “penguin” sign
- The prevalent MRI finding is midbrain atrophy, with dilation and downwards expansion of the third ventricle.
Flattening or concave outline to the superior aspect of the midbrain, which should be upwardly convex, and reduction of the roof thickness makes the “hummingbird” or “penguin” sign
Parkinson’s disease imaging findings
- Reduced thickness of substantia nigra pars compacta
- common finding is the reduction of thickness of the pars compacta of the substantia nigra (T2/T2*w)
- Absent swallow tail sign (SWI protocol)
Role of imaging in Parkinson’s disease
- In idiopathic forms usually there are not specific findings
- The role of neuroradiology consists mainly in the evaluation of atrophy and of the overall parenchymal vascular lesion load”,and in the exclusion of secondary forms
How much does schwannoma account for intracerebral tumors?
- Represent the vast majority (70%) of lesions in the
cerebellopontine cisterns and 5-10% of all intracerebral tumors - Most common extracranial tumors in
the posterior cranial fossa
Origin of schwannoma
In most cases originates from the vestibular branch of the eight cranial nerve, arising generally within the internal acoustic canal, and is centered on IAC
Age of occurence of Schwannoma
Mainly between 30 and 60 years and could be
bilateral.
Imaging characteristics of schwannoma
- Common to see an ice cream cone shape when the tumor is inside the IAC
- No hyperostosis or calcification
- Variable MRI signal: Sometimes it’s hypointense on T1 weighted images and hyperintense on T2-WI
Where would bilateral schwannomas be typically seen?
Neurofibromatosis 2
CPA cisternal tumors types
- Schwannoma 70%
- Meningioma 15-20%
CPA meningioma imaging
- It produces obtuse angles with the petrous part of the temporal bone. The common shape is “mushroom cap-shaped.”
- Generally, on CT, we look for the presence of calcifications inside the tumor or possible hyperostosis of the surface of the bone where benign tumor is located, while aggressive meningiomas (grade 2/3) tend to infiltrate. Isointense MRI signal in T1 and T2 weighted images
Location of CPA meningioma
It tends to be based on the petrous part of the
temporal bone or on tentorium or on petroclinoid ligament;
