Neuroradiology Flashcards
A 69-year-old lady was admitted 10 days ago following an acute intracerebral haematoma
diagnosed on CT. What are the most likely radiological findings on the follow-up MRI scan of
brain? [B1 Q4] {will repeat in parenchymal haemorrhage session}
A. Haematoma hypointense to grey matter on T1WI, hyperintense on T2WI.
B. Haematoma hyperintense to grey matter on both T1WI and T2WI.
C. Haematoma hyperintense to grey matter on T1WI, hypointense on T2WI.
D. Haematoma hypointense to grey matter on both T1WI and T2WI.
E. Haematoma isointense to grey matter on both T1WI and T2WI.
Haematoma hyperintense to grey matter on both T1WI and T2WI.
The MRI appearances of intracranial haemorrhage are determined primarily by the state of
the haemoglobin (Hb), which evolves with age. This can be staged as hyperacute (first few
hours), acute (1–3 days), early subacute (3–7 days), late subacute (4–7 days to 1 month), or
chronic (1 month to years).
A patient is having an MRI scan carried out to investigate a possible right frontal astrocytoma,
incidentally, detected on CT following a head injury. The MRI features are typical of an
astrocytoma, with no evidence of necrosis or callosal involvement to indicate glioblastoma
multiforme (GBM). MRS has been carried out to help assess the grade of this tumour. What
MRS features would indicate a high-grade lesion? [B1 Q17]
A. Elevated choline, reduced N-acetyl aspartate (NAA), choline/creatine (Cho/Cr) ratio of 1.
B. Elevated choline, reduced NAA, Cho/Cr ratio of 2.
C. Normal choline, elevated NAA.
D. Reduced choline, reduced NAA. Cho/Cr ratio of 1.2.
E. All normal, these are unaffected by tumour grade.
Elevated choline, reduced NAA, Cho/Cr ratio of 2.
NAA is thought to be a marker of neuronal integrity, choline indicates cell turnover, and
creatine indicates cell metabolism. Lactate is not detectable in normal brain spectra but is
elevated in inflammation, infarction, and some neoplasms. Most brain conditions, whether
neoplastic, vascular, or demyelinating, are associated with a reduction in NAA. A notable
exception is Canavan’s disease, which causes a rise in NAA. Choline is elevated in many
disorders but is markedly increased in high-grade neoplasms. It has been reported that the
ratio of choline to creatine can be used to help grade tumours, with a ratio over 1.5 indicating
high grade in most cases. A reduced choline and NAA in an area of tumour can indicate
necrosis.
A 34-year-old man undergoes MRI of brain after admission for head trauma. Which of the
following sequences is most sensitive for subarachnoid haemorrhage? [B1 Q30] {will repeat
in meningeal haemorrhage session}
A. T1WI.
B. T1WI with fat saturation.
C. T2WI.
D. FLAIR.
E. Proton density.
FLAIR.
Although CT is generally used for investigating acute subarachnoid haemorrhage (SAH), FLAIR
sequence on MRI has been suggested as being as sensitive as or more sensitive than CT. It is
particularly useful in regions where CT may be limited due to beam hardening artefacts or if
there is a very small amount of blood. Acute SAH appears as high intensity on FLAIR within
the cisterns and sulci. Subacute SAH may be better appreciated on MRI because of its high
signal intensity when the blood is isointense to CSF on CT. SAH differs from intra-parenchymal
haemorrhage in that the mix of blood with high-oxygen tension CSF delays generation of
paramagnetic deoxyhaemoglobin, and oxyhaemoglobin remains present longer than in intra-
parenchymal haemorrhage. This contributes to continued T2 prolongation. Beware that there
are other pathological (meningitis, leptomeningeal metastases, acute stroke, fat-containing
tumour/dermoid rupture) and benign (artefact, supplemental oxygenation) causes of FLAIR
hyperintensity in the subarachnoid space.
Chronic haemorrhage from SAH is best detected on GE sequences, resulting in marked
subarachnoid low signal (the blooming of superficial siderosis).
A 60-year-old female presents with a history of facial pain and diplopia. Clinical examination
reveals palsies of the III, IV, and VI cranial nerves, Horner’s syndrome, and facial sensory loss
in the distribution of the ophthalmic and maxillary divisions of the trigeminal (V) cranial nerve.
Where is the causative abnormality located? [B1 Q44]
A. Dorello’s canal.
B. Cavernous sinus.
C. Superior orbital fissure.
D. Inferior orbital fissure.
E. Meckel’s cave
Cavernous sinus.
Cranial nerves III, IV, and VI, and ophthalmic (V1) and maxillary (V2) divisions of the V cranial
nerve course through the cavernous sinus along with the internal carotid artery. The V2
division of the trigeminal nerve passes through the inferior portion of the cavernous sinus
and exits via the foramen rotundum. The remainder of the cranial nerves mentioned above
enter the orbit via the superior orbital fissure.
The cavernous sinus location accounts for these features. Palsies of cranial nerves III, IV, and
VI result in ophthalmoplegia. Involvement of V1 and V2 divisions of the trigeminal nerve
produces facial pain and sensory loss, involvement of sympathetic nerves around the internal
carotid artery results in Horner’s syndrome. This cluster of findings is found in Tolosa Hunt
syndrome, an idiopathic inflammatory process involving the cavernous sinus.
You are asked to protocol an MRI scan that is specifically being performed to look for vertebral
metastatic disease. The radiographer complains that you have asked for too many sequences.
Which of the following sagittal sequences is likely to be least helpful for the purposes of your
examination? [B1 Q50]
A. STIR.
B. T2 fast SE with fat saturation.
C. T2 fast SE.
D. T1 fast SE.
E. T1 GE out of phase
T2 fast SE.
T2 fast SE is probably the least useful sequence when specifically looking for vertebral marrow
deposits because the metastases are less conspicuous, typically being high signal on a
background of high-signal fatty marrow. On STIR and T2 fast SE with fat saturation, the
metastases typically stand out as being of increased signal on a background of dark marrow
because of the fat saturation techniques. On T1 fast SE sequences, the metastases typically
stand out as being low signal on a background of high-signal fatty marrow.
Finally, T1 GE out–of-phase imaging is also good for looking for vertebral metastatic disease.
This is a sequence with a specific echo time corresponding to the time it takes for water and
fat protons to move exactly 180° out of phase. In the normal adult human, the medullary
bone of the vertebral bodies contains approximately equal amounts of water and fat protons.
In out-of phase conditions, the signal of both will cancel out, leaving the vertebrae completely
black. In the case of vertebral pathology, however, the signal will increase and, as such,
vertebral metastases (or other lesions) will clearly stand out.
A 32-year-old woman of 38 weeks’ gestation presents with seizure following a headache. She
is referred for CT querying venous thrombosis. Unenhanced CT brain demonstrates bilateral
low attenuation change within the thalami. Given this location, where is the most likely site of
thrombosis? [B1 Q61] {will repeat again in Venous Sinus Section}
A. Superior sagittal sinus.
B. Transverse sinus.
C. Sigmoid sinus.
D. Straight sinus.
E. Cavernous sinus.
Straight sinus.
Pregnancy is a risk factor for both venous sinus thrombosis and hypertensive haemorrhage
secondary to eclampsia. Hyperattenuating thrombus within the occluded sinus is classical on
the unenhanced CT but is seen in only 25% of cases. On the contrast-enhanced study, a central
filling defect surrounded by enhancing dura (empty delta sign) is present in over 30%. Most
of the superior cerebrum is drained by the superior sagittal sinus. The transverse sinuses
receive blood from the temporal, parietal, and occipital lobes. The transverse sinuses drain
into the sigmoid sinuses and on into the internal jugular veins. The straight sinus forms from
the confluence of the inferior sagittal sinus and vein of Galen. The vein of Galen is part of the
deep venous system, which drains the corpus callosum, basal ganglia, thalami, and upper
brainstem. Cavernous sinus thrombosis presents with proptosis and cranial nerve palsies
(usually cranial nerve VI first). The cavernous sinus receives the petrosal sinuses and middle
cerebral veins
A 24-year-old male boxer is admitted with concussion following a head injury. His admission
CT does not demonstrate any evidence of intracranial injury, but the A&E physician asks you
about a midline CSF space. You explain that this is a cavum velum inter-positum. What
distinguishes this CSF space from cavum velum inter-positum and cavum vergae? [B1 Q72]
{will repeat again in ventricles and CSR section}
A. Position between the frontal horns of the lateral ventricles.
B. Posterior extension between the fornices.
C. Does not extend anterior to foramen of Monro.
D. Mildly hyperdensity to CSF in lateral ventricles.
E. Absent septum pellucidum.
Does not extend anterior to the foramen of Monro.
Cavum septum pellucidum (CSP), cavum vergae (CV), and cavum vellum inter-positum (CVI)
are all considered normal variants, although CSP is possibly more prevalent in boxers due to
repeated head trauma, most famously referred to in Rocky V. CSP is universal in foetuses but
decreases with age. CSP is an elongated finger-shaped CSF collection between the frontal
horns of the lateral ventricles. Posterior extension between the fornices is referred to as CV.
CV almost never occurs in the absence of CSP. CVI, however, is a triangular-shaped CSF space
between the lateral ventricles that does not extend anterior to the foramen of Monro.
Absent septum pellucidum can look like CSP/CV on sagittal imaging. It is commonly associated
with other congenital anomalies
A 42-year-old male is admitted with first presentation of a seizure. There is no significant past
medical history. CT demonstrates a mass lesion within the right frontal lobe. He is further
investigated via MRI, which includes MR perfusion and spectroscopy. The neurosurgical team are keen to biopsy this lesion if there is radiological suspicion of a high-grade lesion. Which
of the following radiological findings is most consistent with a high-grade lesion? [B1 Q73]
A. Relative cerebral blood volume (rCBV) 1.5 on MR perfusion.
B. Lactate peak on MRS.
C. Elevated ADC on DWI.
D. Peritumoral hyperintensity on T2WI.
E. Nodular enhancement on T1WI post gadolinium.
Lactate peak on MR spectroscopy.
Neuroepithelial tumours are either low grade (WHO I and II) or high grade (WHO III and IV).
The classification relies on pathology, but as this requires brain biopsy it is not without
significant risk. Advanced MRI techniques play an increasing role in helping to differentiate
these lesions, as low-grade lesions may be managed via a ‘watch and wait’ approach.
Conventional MRI is poorly sensitive for glioma grading, as low-grade gliomas can enhance (in
up to 20%) and up to 30% of non-enhancing gliomas are malignant.
MR perfusion can help differentiate, as rCBV tends to increase with tumour grade. A threshold
of 1.75 is commonly utilized to separate low- from high-grade gliomas, but low-grade
oligodendrogliomas can give misleadingly elevated rCBV values.
The classic MR spectroscopy features of high-grade lesions are elevated choline and reduced
NAA. In addition, an elevated lactate signal is typical of high-grade lesions secondary to the
anaerobic environment.
ADC is usually lower in high-grade lesions, but there is considerable overlap and so ADC maps
are insufficient on their own for predicting tumour grade.
A 36-year-old woman with known polycystic kidney disease presents with a history of sudden
onset headache and has signs of meningism. A CT brain reveals subarachnoid haemorrhage
with haematoma within the septum pellucidum. What is the most likely site for an intracerebral
aneurysm? [B2 Q9]
a. Anterior communicating artery
b. Posterior communicating artery
c. A2 segment of an anterior cerebral artery
d. Tip of the basilar artery
e. Middle cerebral artery
A
Anterior communicating artery
A clot in the septum pallucidum is virtually diagnostic of an aneurysm of the anterior
communicating artery. Aneurysms of the distal anterior cerebral artery are less common.
Which is the preferred sequence to use when attempting to identify posterior fossa lesions on
MRI in patients with multiple sclerosis? [B2 Q24]
a. T1-weighted spin-echo
b. T2-weighted spin-echo
c. FLAIR
d. Gradient-echo
e. Proton density
T2-weighted spin-echo
Multiple sclerotic plaques can be located anywhere in the central nervous system but typically
they form at the junction of the cortex and white matter and peri ventricularly.
FLAIR is particularly good at locating periventricular lesions as CSF signal is suppressed. In the
posterior fossa, however, FLAIR detects fewer lesions than T2-weighted spin-echo.
A 48-year-old woman presents with symptoms of hyperparathyroidism. Radionuclide and
ultrasound imaging suggest the cause is a solitary parathyroid adenoma. The surgeon requests
further localisation with MRI prior to surgery. Which imaging sequence and plane would you
choose as the most sensitive for detection of the adenoma? [B2 Q35] {will repeat again in
thyroid and parathyroid section}
a. T1-weighted in the axial plane
b. T2-weighted in the coronal plane
c. FLAIR in the coronal plane
d. T2 fat-suppressed in the axial plane
e. Gradient-echo in the axial plane
T2 fat-suppressed in the axial plane
Degenerative spinal vertebral body endplate changes, as seen on MRI, may have which of the
following appearances? [B4 Q11]
a. type I– high T1W and low T2W signal
b. type I– low T1Wand low T2W signal
c. type II– high T1W and high T2W signal
d. type II– low T1W and high T2W signal
e. type II– high T1W and low T2W signal
Type II – high T1W and high T2W
The endplates in degenerative disc disease have three described appearances during their
evolution, which are also known as Modic changes. Type I (marrow oedema) changes show
low signal on T1W and high signal on T2W sequences. Type II (fatty marrow) changes show
high signal on both T1W and T2W sequences. Type III (sclerosis) changes are low signal on
both T1W and T2W sequences
An elderly male patient presents with signs suggesting acute middle cerebral artery infarction.
Around 21 2hours after symptom onset, an unenhanced CT of the brain is performed. Among
other subtle signs, the basal ganglia are obscured. Reduced perfusion through which of the
following vessels best explains this sign? [B4 Q33]
a. lenticulostriate arteries
b. anterior choroidal artery
c. calloso-marginal artery
d. recurrent artery of Heubner
e. angular artery
Lenticulostriate arteries
The lenticulostriate arteries are vessels arising from the M1 segment of the middle cerebral
artery; there are medial and lateral groups. Collectively, they supply the thalamus, caudate
and lentiform nuclei. The calloso-marginal artery and the recurrent artery of Heubner are
anterior cerebral artery branches. The latter provides some supply to the anterior limb of the
internal capsule, and parts of the caudate nucleus and globus pallidus. The angular artery is a
cortical branch of the middle cerebral artery. The anterior choroidal artery also supplies parts
of the internal capsule and basal ganglia but is a branch of the internal carotid artery. The
nuclei of the basal ganglia are the amygdala, claustrum, lentiform and caudate nuclei, with
the internal, external and extreme capsules being associated white matter tracts.
A 17-year-old boy presents with headache and is found to have paralysis of upward gaze
(Parinaud’s syndrome) on examination. MR scan of the brain identifies an abnormality. What
is the most likely site of the lesion? [B4 Q46]
a. thalamus
b. occipital lobe
c. optic chiasm
d. pineal gland
e. cerebellar vermis
Pineal Gland
Parinaud’s syndrome (also known as dorsal midbrain syndrome) is characterized by
supranuclear paralysis of upward gaze. It results from injury or compression of the dorsal
midbrain, in particular the superior colliculi, and is most seen in young patients with tumours
of the pineal gland or midbrain, with pineal germinoma being the most common lesion
producing the syndrome. Young women with multiple sclerosis and elderly patients with
brain-stem stroke may also present with Parinaud’s syndrome
Which of the following represents an appropriate window width and level for viewing the bony
structures on a CT scan of the brain? [B4 Q48]
a. width 80, level 35
b. width 400, level 40
c. width 250, level 70
d. width 2000, level 500
e. width 1500, level–500
Width 2000, level 500
CT images are displayed with different window levels and widths to highlight differences in
CT attenuation between the structures of interest. Narrow window widths (80–400 HU) and
lower levels (20–80 HU) are used to emphasize differences between soft tissues, whereas
wide widths (2000–3000 HU) and higher levels (300–600 HU) are used for optimal
visualization of bony structures. Images are usually also reconstructed using specific bone
algorithms to accentuate the bone–soft tissue interface.
