CNS Flashcards
CNS
A 75-year-old woman is admitted under the physicians with confusion and dementia. She has a history of spontaneous intracranial hemorrhage and has been diagnosed with amyloid angiopathy. The most specific MR sequence for diagnosis of multifocal intracranial cortical–subcortical micro-haemorrhages in cerebral amyloid angiopathy is:
A. T1W spin echo
B. STIR
C. T2W spin echo
D. Gradient echo
E. FLAIR
D. Gradient echo
Cerebral microbleeds are increasingly recognized neuroimaging findings, occurring with cerebrovascular disease, dementia, hypertensive vasculopathy, cerebral amyloid angiopathy and normal ageing.
Recent years have seen substantial progress in developing newer MRI methodologies for microbleed detection.
Hemosiderin deposits in microbleeds are super-paramagnetic and thus have considerable internal magnetization when brought into the magnetic field of MRI, a property defined as magnetic susceptibility. Among available pulse sequences, T2-star-weighted GRE MRI is most sensitive to the susceptibility effect.
CNS
A young man presents to the ENT clinic with deepening of the voice. Going through his history and clinical notes, the consultant reviews a recent plain radiograph report of his hands, which describes cystic changes in the carpal bones along with enlarged phalangeal tufts and metacarpals.
What is the next appropriate imaging investigation?
A. CT brain pre- and post-contrast
B. MRI brain
C. MRI pituitary pre- and post-contrast
D. Chest X-ray
E. Lateral view of the skull
C. MRI pituitary pre- and post-contrast
The clinical history along with the radiographic findings points towards acromegaly, and in this case evaluating the pituitary gland for the presence of an adenoma along with correlating biochemistry blood profile would be appropriate investigations. Osseous enlargement of the vertebrae with increased AP diameter can occur with premature loss of disc space. Expansion of the terminal phalangeal tufts and metacarpals contribute to the clinical finding of ‘spade like hands’. Other features include increased heel pad thickness >25 mm, premature OA, posterior vertebral scalloping, prognathism (elongated mandible), sellar enlargement and enlarged paranasal sinuses, mostly frontal sinus. In the case of pituitary macroadenomas, compression of the optic chiasm can often result in visual field defects.
CNS
A 77-year-old man with gradual onset dementia shows multifocal abnormalities on cranial CT and MRI. He has been recently diagnosed with amyloidosis. All of the following conditions may be present in central nervous system amyloidosis, except:
A. Occurrence in elderly patients
B. Multifocal subcortical intracranial hemorrhages
C. Cerebral and cerebellar atrophy
D. Non-communicating hydrocephalus
E. Typical occurrence in normotensive patients
D. Non-communicating hydrocephalus
Cerebral amyloid angiopathy (CAA) is an important cause of spontaneous cortical–sub cortical intracranial hemorrhages (ICH) in the normotensive elderly. On imaging, multiple cortical–subcortical hematomas are recognized. Prominence of the ventricular system and enlargement of the sulci representing generalized cerebral and cerebellar atrophy are non-specific imaging findings.
CAA should be considered in the broad differential diagnosis of leukoencephalopathy (high signal intensity of white matter at T2-weighted MRI), especially if associated with cortical–subcortical hemorrhage or progressive dementia. Leukoencephalopathy may or may not spare U-fibres.
CNS
A 33-year-old woman with recurrent episodes of optic neuritis with waxing and waning upper limb weakness is referred for an MRI brain with high suspicion of demyelination. All of the following are MR features of acute multiple sclerosis (MS) lesions of the brain, except:
A. High signal intensity on FLAIR
B. ‘Black hole’ appearance
C. Incomplete ring-like contrast enhancement
D. Increase in size of lesion
E. Mass effect
** B. ‘Black hole’ appearance**
MS lesions can occur anywhere in the central nervous system but are most common in the periventricular white matter. Typical lesions are ovoid, with the long axis perpendicular to the ventricles. They are better seen on PD and FLAIR than on T2-weighted images because of increased lesion–CSF contrast.
Lesions of the corpus callosum, at calloso-septal interface and subcallosal striations are characteristic. FLAIR is less sensitive than T2-weighted images to infratentorial lesions occurring in the brain stem and middle cerebellar peduncles. In the acute phase, lesions show increase in size and solid or ring enhancement with IV contrast, which can persist up to 3 months, but generally resolve in weeks. Large acute lesions, with associated oedema, mass effect and incomplete ring enhancement can mimic glioma (tumefactive MS).
MS lesions show reduced magnetization transfer ratio (MTR), reflecting decreased myelin content. MTR is also reduced in normal-looking white matter, representing occult tissue damage. Such occult tissue damage is also detected by diffusion tensor imaging, showing reduced fractional anisotropy. Low-signal lesions on T1-weighted MRI (black holes), brain and spinal cord atrophy are seen in established MS.
CNS
A 34-year-old woman with previous history of upper limb weakness that resolved spontaneously and optic neuritis was referred for an MRI brain. MRI confirms the presence of bilateral periventricular hyperintensities on FLAIR with abnormal signal in the corpus callosum and middle cerebellar peduncles. MRI also shows signal abnormality in the right optic nerve. Which portion of the optic nerve does Multiple sclerosis (MS) most commonly affect?
A. Intra-orbital.
B. Intra-canalicular.
C. Intracranial.
D. Chiasmatic.
E. All portions are equally susceptible.
A. Intra-orbital
Typically, findings of optic neuritis in MS are seen in the retrobulbar intra-orbital segment of the optic nerve, which appears swollen, with high T2 signal. High T2 signal persists and may be permanent; chronically the nerve will appear atrophied rather than swollen. Contrast enhancement of the nerve is best seen with fat-suppressed T1-weighted coronal images, in >90% of patients if scanned within 20 days of visual loss.
CNS
A newborn baby has US of the spine. At which level is the conus expected to be?
A. Above L1
B. Above T12
C. L2 to L3
D. L3 to L4
E. S2
C. L2 to L3
The conus normally lies at or above the L2 disc space. A normal conus located at the mid-L3level may be identified, especially in preterm infants; this position is considered the lower limits of normal but is usually without clinical consequence. However, in a preterm infant with a conus that terminates at the L3 mid-vertebral body, a follow-up sonogram can be obtained once the infant attains a corrected age between 40 weeks’ gestation and 6 months of age. In contrast, the thecal sac terminates at S2.In the preterm group, more than 90% of conus medullaris cases lie above L2; in the term group, more than 92% lie above L2.
CNS
A 36-year-old woman with resolving limb weakness and previous history of optic neuritis is diagnosed as having relapsing remitting multiple sclerosis (RRMS). Which of the following statements concerning MS imaging is incorrect?
A. Black holes correlate well with clinical outcome.
B. Brain atrophy is higher in MS than normal ageing.
C. The pattern of brain atrophy can mimic Alzheimer’s disease.
D. Diffusion tensor imaging demonstrates structural damage to the white matter.
E. MS lesions have low MTR (Magnetization Transfer Ratio) representing myelin loss.
C. The pattern of brain atrophy can mimic Alzheimer’s disease
The T1 lesion load including enhancing lesions or black holes is correlated more closely than T2 lesion load with clinical outcome. Another imaging hallmark of MS is brain atrophy. Brain atrophy in MS usually appears as enlarged ventricles and reduced size of the corpus callosum. The rate of brain atrophy is higher in MS than in the normal ageing process. Significant loss of white matter rather than grey matter is seen in the early stage of MS, suggesting a different mechanism of atrophy
compared to neurodegenerative diseases such as Alzheimer’s disease. MS lesions show reduced Magnetization transfer ratio (MTR), reflecting decreased myelin content. MTR is also reduced in normal-looking white matter, representing occult tissue damage. MS lesions usually have a more reduced MTR as compared with ischemic lesions in small vessel diseases. Such occult tissue damage is also detected by diffusion tensor imaging, showing reduced fractional anisotropy (representing microstructural damage).
CNS
A known MS patient has presented to the neurologist with clinical features of involvement of the spinal cord. An MRI of the whole spine has been requested with a view towards assessment of the cord for possible multiple sclerosis (MS) plaques. MS lesions in the spinal cord occur most commonly in the
A. Cervical segment.
B. Thoracic segment.
C. Lumbar segment.
D. Sacral segment.
E. All segments are equally affected.
A. Cervical segment
MS can show multiple lesions in the spinal cord. Typical spinal cord lesions in MS are relatively small and peripherally located.
They are most often found in the cervical cord and are usually less than two vertebral segments in length.
CNS
A patient recently diagnosed with MS has been sent for an MRI of the whole spine to detect possible spinal plaques. All of the following are MR features of spinal cord lesions
in MS, except
A. The sole site of involvement (in some cases).
B. Imaging features similar to those of MS lesions in the brain.
C. Most lesions are centrally located.
D. The length rarely exceeds two vertebral segments.
E. Dorsal column involvement.
C. Most lesions are centrally located.
Occurrence of spinal cord abnormalities is largely independent of brain lesions in MS. Both focal and disuse lesions affecting the cord arc described, though multiple focal lesion (median 3) is the most common finding. Patients with focally involved spinal cords mostly show multiple small lesions. Focal lesions have an elongated configuration along the axis of the spinal cord and affect the peripheral part of the cord. Cervical cord is the most commonly affected segment and the lesions usually extend over fewer than two vertebral segments in length.
CNS
A 54-year-old man who developed brain metastases almost 9 years after resection of an acral lentiginous melanoma of the distal thumb shows two peripheral nodules in the right frontal lobe. All of the following are features of CNS metastatic melanoma, except
A. Moderate to intense enhancement post-contrast administration
B. Cystic components
C. Subependymal nodules
D. Multiple lesions at the gray white matter junction
E. Miliary pattern
B. Cystic components
Metastatic malignant melanoma is a commonly encountered neoplasm in the head. Typical appearance of a lesion is high signal intensity on T1-weighted images and low signal on T2-weighted images (melanotic pattern). The other described pattern is the amelanotic pattern. In this pattern, the lesion is hypointense or isointense to the cortex on T1-weighted images and hyperintense or isointense to the cortex on T2-weighted images. Metastatic melanoma presents as multiple brain metastasis, which are located predominantly in the cortex and at the grey matter- white matter junction. They can also present in miliary form or as subependymal nodules. The lesions often appear hyperdense on unenhanced CT. The lesions show moderate to intense contrast enhancement, although larger lesions can show non-enhancing or hypoenhancing necrotic areas. Prominent perilesional oedema is seen.
CNS
A 1-month-old baby presents with difficulty in feeding and shortness of breath. Chest X-ray shows cardiomegaly. She has an episode of seizure and undergoes cranial US, which shows a median tubular cystic space with high-velocity turbulent flow on Doppler. The ventricles are also mildly dilated. These findings are consistent with
A. Pineal tumour
B. Arachnoid cyst
C. Colloid cyst
D. Vein of Galen aneurysm
E. Ventriculitis
D. Vein of Galen aneurysm
Vein of Galen aneurysmal malformations (VGAMs) are rare congenital vascular malformations characterized by shunting of arterial flow into an enlarged cerebral vein dorsal to the tectum. Most of these malformations present in early childhood, often causing congestive heart failure in the neonate.
Antenatal ultrasound scans demonstrate the venous sac as a sonolucent mass located posterior to the third ventricle. Ultrasonic demonstration of pulsatile flow within it helps in differentiating
VOGMs from other midline cystic lesions. Associated venous anomalies can often be visualized. Evidence of hydrocephalus and cardiac dysfunction can also be obtained on antenatal ultrasonography. Contrast enhanced axial CT scan of the brain usually demonstrates a well-defined, multilobulated, intensely enhancing lesion located within the cistern of velum interpositum. Dilatation of the ventricular system and periventricular white matter hypodensities, as well as diffuse cerebral atrophy, are the commonly associated findings.
CNS
An 18-month-old child is brought in by her mother with complaints of visual problems; on examination, the left eye is of normal size with a whitish mass behind the lens. US shows
a heterogeneous hyperechoic solid intra-ocular mass with retinal detachment. There are fine focal calcifications with acoustic shadowing. The appearances suggest
A. Persistent hyperplastic primary vitreous
B. Coats disease
C. Retinoblastoma
D. Toxocara endophthalmitis
E. Retrolental fibroplasia
C. Retinoblastoma
Retinoblastoma, a small round-cell tumour arising from neuroepithelial cells, is the most common childhood intra ocular malignancy. Diagnosis is typically by ophthalmologic examination, prompted by leukocoria or ‘white reflex’.
Retinoblastoma appears as an echogenic soft-tissue mass with various degrees of calcification. The vascularity indicates tumour activity; that is, lesions are hypervascular at diagnosis and when active. Vascularity regresses with treatment. CT detects intra-ocular, extra-ocular and intracranial disease extension; excels at delineation of bony abnormalities; and readily depicts tumoural calcifications. On CT, retinoblastoma is characterised by an intermediate-density enhancing soft-tissue mass or masses, with varying degrees of calcification; calcification increases with therapeutic response. The vitreous may be abnormally dense from debris, haemorrhage, or increased globulin content. Retinoblastoma is a heterogeneously enhancing soft-tissue mass with various degrees of calcification on MRI. Lesions are typically hyperintense to vitreous on T1 -weighted sequences and hypointense to vitreous on T2-weighted sequences. The vitreous may be abnormally bright on T1-weighted sequences because of increased globulin content and a decreased ratio of albumin to globulin that occurs with malignancy.
The other choices are all differentials for white reflex, but do not show a solid mass with calcification.
CNS
A 58-year-old man with facial fractures shows deformity of the globe on unenhanced axial CT, but it is unclear if there is an open-globe injury. All of the following CT findings suggest an open-globe injury, except
A. Intra-ocular air
B. Lens dislocation
C. Scleral discontinuity
D. Flat tire sign
E. Deep anterior chamber
B. Lens dislocation
In blunt traumas, ruptures are most common at the insertions of the intra-ocular muscles where the sclera is thinnest. CT findings suggestive of an open globe injury include a change in globe contour, an obvious loss of volume, the ‘flat tire sign, scleral discontinuity, intra-ocular air and intra-ocular foreign bodies. A deep anterior chamber has been described as a clinical finding in patients with a ruptured globe and can also be a clue on CT.
CNS
A 67 year-old man has been rushed to the stroke unit with features of acute stroke. All of the following are true about acute stroke imaging, except
A. CT source images correlate with infarct volume.
B. Matched CBV (Cerebral blood volume) and CBF (Cerebral blood flow) represent salvageable brain.
C. Diffusion-weighted MR imaging assesses the infarct core.
D. Mismatch between PWI (Perfusion weighted imaging) and DWI (Diffusion weighted imaging) volumes represents salvageable brain.
E. T2 shine through is seen as bright on DWI.
B. Matched CBV (Cerebral blood volume) and CBF (Cerebral blood flow) represent
salvageable brain.
An important advance in stroke imaging is the development of CT perfusion imaging. CT angiography source images (CTA-SI) represent cerebral blood volume that is reduced in the core infarct and correlates with infarct volume as seen on DWI (Diffusion Weighted Imaging).
CBF (cerebral blood flow), CBV (cerebral blood volume), and MTT (mean transit time) are three parameters that can distinguish infarcted tissue from potentially salvageable penumbra. Ischemic but non infarcted tissue will have decreased CBF, elevated MTT, and normal or high CBV (mismatch). Once infarcted, there will also be a persistent decrease in CBV (matched defect). Sensitivity and specificity of DWI for stroke detection is very high. DWI bright signals do not necessarily represent irreversibly infarcted tissue but reflect redistribution of water from the extracellular to the intracellular space in ischaemic tissue. It is necessary to analyse maps of ADC (apparent diffusion coefficient) to distinguish the effects of reduced water diffusibility (dark on ADC) from T2 ‘shine-through’ (bright on ADC). Both features lead to the DWI bright signals seen
in ischaemia. The volumetric mismatch between the FWI and DWI volumes is a marker of potentially salvageable tissue at risk. Overall DWI provides the best estimate of infarcted core.
CNS
Neck US of a previously well 2-year old girl shows a 3-cm thin-walled cystic structure with multiple septae of variable thickness in the left posterior triangle with extension into the mediastinum. The diagnosis is:
A. Third branchial cleft cyst
B. Cervical meningocoele
C. Cystic teratoma
D. Lymphangioma
E. Second branchial cleft cyst
D. Lymphangioma
A cystic hygroma is the most common form of lymphangioma and constitutes about 5% of all benign tumours of infancy and childhood. On US scans, most cystic hygromas manifest as a multilocular predominantly cystic mass with septa of variable thickness. The echogenic portions of the lesion correlate with clusters of small, abnormal lymphatic channels. Fluid-fluid levels can be observed with a characteristic echogenic, haemorrhagic component layering in the dependent portion of the lesion. Prenatal US may demonstrate a cystic hygroma in the posterior neck soft tissues. On CT images, cystic hygromas tend to appear as poorly circumscribed, multiloculated, hypoattenuated masses. They typically have characteristic homogeneous fluid attenuation. Usually, the mass is centred in the posterior triangle or in the submandibular space.
A third branchial cleft cyst most commonly appears as a unilocular cystic mass centred in the posterior cervical space on CT and MRI. At US, a second branchial cleft cyst is seen as a sharply marginated, round to ovoid, centrally anechoic mass with a thin peripheral wall that displaces the surrounding soft tissues. The ‘classic’ location of these cysts is at the anteromedial border of the sternocleidomastoid muscle. The first branchial cleft cyst appears as a cystic mass either within, superficial to, or deep to the parotid gland
