Central nervous and head & neck

Question 1

1. A 20 year old male presents with the inability to gaze upwards. CT brain shows
   moderate hydrocephalus and a rounded mass adjacent to the tectal plate. The mass
   demonstrates marked homogeneous enhancement and is not calcified. MRI confirms a
   well-circumscribed, relatively homogeneous mass that is isointense to grey matter on
   T2-weighted imaging. The mass is hyperintense on contrast-enhanced T1-weighted
   imaging. What is the most likely diagnosis?
   a. Germinoma
   b. Teratoma
   c. Pineoblastoma
   d. Pineocytoma
   e. Benign pineal cyst

Answer 1

1. a. Germinoma
   Germinomas are germ-cell tumours arising from primordial germ cells. They frequently
   occur in the midline, mostly in the pineal region but also in the suprasellar region.
   In men, 80% of pineal masses are germ-cell tumours, in contrast to 50% in women. They
   tend to occur in children or young adults (10–25 years old). Symptoms depend on the
   location but the case describes Parinaud syndrome – paralysis of upward gaze due to
   compression of the mesencephalic tectum. Germinomas may also cause hydrocephalus by
   compression of the aqueduct of Sylvius, thus patients may present with signs and symptoms
   of raised intracranial pressure. Germinomas are a known cause of precocious puberty in
   children under the age of ten years. They are malignant tumours and may show CSF
   seeding, making cytological diagnosis possible with lumbar puncture. They are, however,
   very radiosensitive and show excellent survival rates.
   Pineal teratomas tend to be heterogeneous masses containing fat and calcifications.
   Pineoblastoma is a highly malignant tumour which is more common in children and
   usually has poor tumour margins.

Question 2

2. A 40 year old female is investigated for worsening headaches. CT shows a well-defined
   hyperdense globular lesion within the trigone of the left lateral ventricle. There is
   intense contrast enhancement. The most likely diagnosis is:
   a. Choroid cyst
   b. Ependymoma
   c. Colloid cyst
   d. Meningioma
   e. Neurocytoma

Answer 2

2. d. Meningioma
   It is rare for meningiomas to occur intraventricularly (2–5% of all meningiomas) but they
   are the most common trigonal intraventricular mass in adulthood. They tend to occur in
   40 year old females

Question 3

3. A 40 year old female presents with bitemporal hemianopia. CT brain shows a large,
   slightly hyperdense suprasellar lesion. The mass contains several lucent foci and there is
   bone erosion of the sella floor. There is enhancement post-contrast. T1-weighted MR
   imaging shows a predominantly isointense mass causing sella expansion and compression
   of the optic chiasm. The mass contains foci of low and high signal intensity. What is
   the most likely diagnosis?
   a. Craniopharyngioma
   b. Meningioma
   c. Rathke’s cleft cyst
   d. Giant internal carotid aneurysm
   e. Pituitary adenoma

Answer 3

3. e. Pituitary adenoma
   Pituitary adenomas are divided into microadenomas (<1 cm) and macroadenomas
   (>1 cm). Macroadenomas may present with endocrine dysfunction but are generally less
   active than microadenomas. Thus, macroadenomas often present with symptoms of mass
   effect on the optic chiasm, or if there is lateral extension into the cavernous sinuses patients
   may present with other local cranial nerve palsies (III, IV, VI).
   The differential diagnosis of a suprasellar mass includes (‘SATCHMO’): Suprasellar
   extension of pituitary adenoma/sarcoid; Aneurysm/arachnoid cyst; TB/teratoma (other
   germ-cell tumours); Craniopharyngioma; Hypothalamic glioma or hamartoma; Meningioma/
   metastases (especially breast); and Optic/chiasmatic glioma.
   In this case, the sellar is widened and the floor is eroded suggesting the mass arises from
   the pituitary itself. Low-density/low-intensity regions on CT/T1 MRI correspond to necrotic
   areas and high-signal foci on T1 MRI (found relatively frequently) represent areas of
   recent haemorrhage.

Question 4

4. When on call you are asked to perform a CT head scan for a 17 year old male who
   presents with seizures. He is unable to provide a history. A look on the computer
   system shows that he has had previous regular abdominal ultrasounds and an echocardiogram
   as a child. Brain CT shows a hypodense, well-demarcated, rounded mass in the region of the foramen of Monro. It is partially calcified and it demonstrates uniform
   enhancement. What is the most likely diagnosis?
   a. Colloid cyst
   b. Giant cell astrocytoma
   c. Metastasis
   d. Lymphoma
   e. Haemangioblastoma

Answer 4

4. b. Giant cell astrocytoma
   The main differential for a mass at the foramen of Monro is between a colloid cyst and a
   subependymal giant cell astrocytoma. The latter is associated with tuberous sclerosis (TS).
   Renal involvement is also relatively common in TS and patients regularly have surveillance
   renal ultrasounds. The echocardiogram was performed to assess for cardiomyopathy/
   rhabdomyoma.
   Other central nervous system findings in patients with TS include:
5. Subependymal hamartomas – these are nodular and irregular and can be located anywhere
   along the ventricular walls but predominantly occur around the foramen of Monro or
   along the lateral ventricles. In infants, with unmyelinated white matter the lesions are
   usually hyperintense on T1 and hypointense on T2. The reverse is seen in adults.
6. Subcortical and cortical hamartomas (tubers) – these appear as broad cortical gyri with
   abnormalities in the adjacent white matter. They frequently calcify but enhancement is
   extremely rare.
7. Heterotopic grey matter islands in white matter. These may calcify and show contrast
   enhancement.
   Colloid cysts are typically hyperdense on CT and show border enhancement.

Question 5

5. A 35 year old male presents with ataxia and nystagmus. Blood tests reveal polycythaemia.
   CT head demonstrates a mass predominantly of CSF density in the posterior fossa.
   Subsequent MRI shows a largely cystic mass with an enhancing mural nodule. There is
   surrounding oedema but no calcification. The most likely diagnosis is:
   a. Metastasis
   b. Pilocytic astrocytoma
   c. Haemangioblastoma
   d. Choroid cyst
   e. Ependymoma

Answer 5

5. c. Haemangioblastoma
   Haemangioblastoma is the most common primary intra-axial, infratentorial tumour in
   adults. They are benign autosomal dominant tumours of vascular origin. Approximately
   20% occur with von Hippel–Lindau disease. Other associations include phaeochromocytomas,
   syringomyelia and spinal cord haemangioblastomas. About 20% of tumours cause
   polycythaemia. Typical CT and MRI appearances are of a largely cystic mass with an
   enhancing mural nodule. Oedema may be absent or extensive but calcification is rare.
   Prognosis is 85% post-surgical five-year survival rate.
   Infratentorial pilocytic astrocytomas may have very similar appearances to haemangioblastomas
   but some differences exist that can help differentiate the two. Pilocytic astrocytomas
   predominantly occur in children and young adults, are generally larger (>5 cm) than
   haemangioblastomas, may contain calcifications and are not associated with polycythaemia.

Question 6

6. A 50 year old woman presents with visual loss. Examination reveals retinal detachment
   and an ocular lesion. On MRI, the lesion is hyperintense on T1 and hypointense on
   T2 relative to the vitreous. The lesion enhances post-gadolinium injection. The most
   likely diagnosis is:
   a. Metastases from breast cancer
   b. Metastases from lung cancer
   c. Choroidal haemangioma
   d. Malignant melanoma
   e. Vitreous lymphoma

Answer 6

6. d. Malignant melanoma
   This is the most common primary intraocular neoplasm in adult Caucasians. The typical
   age range is 50–70 years old. They are almost always unilateral and located in the choroid,
   although ciliary body and iris melanomas are not uncommon.
   Presentation can be with retinal detachment, vitreous haemorrhage, astigmatism or
   glaucoma. MRI shows a sharply circumscribed hyperintense lesion on T1, due to the
   paramagnetic properties of melanin, and hypointense relative to the vitreous body on T2.

Question 7

7. A 35 year old previously well female consults an ophthalmologist with a history of
   progressive loss of visual acuity over several months. Retinal examination reveals
   papilloedema. Unenhanced CT shows tubular thickening of the optic nerve associated
   with dense calcifications. Post-contrast injection shows a non-enhancing optic nerve
   surrounded by a markedly enhancing soft-tissue mass. The remainder of the brain is
   normal. The most likely diagnosis is:
   a. Optic nerve glioma
   b. Perioptic meningioma
   c. Sarcoidosis
   d. Lymphoma
   e. Multiple sclerosis

Answer 7

7. b. Perioptic meningioma
   These tumours account for less than 2% of all intracranial meningiomas. They occur within
   the third to fifth decades and are more common in females. They are also associated with
   neurofibromatosis type 2. They typically present with progressive loss of visual acuity over
   several months due to optic atrophy.
   They are usually tubular in appearance although fusiform and excrescentic thickening of
   the optic nerve also exist. Tumour enhancement around a non-enhancing optic nerve
   (tram-track sign) and calcification are highly suggestive of meningioma.

Question 8

8. Routine first-trimester antenatal ultrasound scan reveals a large posterior fossa cyst
   and ventriculomegaly. Fetal MRI demonstrates dysgenesis of the corpus callosum, a
   large posterior fossa and hypoplasia of the cerebellar vermis. What is the most likely
   diagnosis?
   a. Dandy–Walker malformation
   b. Dandy–Walker variant
   c. Megacisterna magna
   d. Arachnoid cyst
   e. Porencephaly

Answer 8

8. a. Dandy–Walker malformation
   Dandy–Walker malformation is characterised by an enlarged posterior fossa (not seen in
   Dandy–Walker variant) with high-rising tentorium cerebelli, dys/agenesis of the cerebellar
   vermis (intact in megacisterna magna) and cystic dilatation of the fourth ventricle (normal
   in arachnoid cyst). Ventriculomegaly is also common

Question 9

9. 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 pallucidum. What is the most
   likely site for an intracerebral aneurysm?
   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

Answer 9

9. 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.

Question 10

10. A 68 year old male attends the emergency department after being found slumped in
    his chair at home by a carer. CT head shows an intraparenchymal bleed. On MRI
    the lesion is hyperintense on T1 and hypointense on T2-weighted imaging. Which of
    the following stages of haemorrhage best correlates with the MRI findings?
    a. Oxyhaemaglobin
    b. Deoxyhaemoglobin
    c. Intracellular methaemoglobin
    d. Extracellular methaemoglobin
    e. Haemosiderin

Answer 10

10. c. Intracellular methaemoglobin

Question 11

11. A middle-aged female presents with unilateral proptosis. CT of the orbits reveals an
    intraconal mass with involvement of the lateral rectus muscle to its point of tendinous
    insertion. The lesion enhances post-contrast injection. MRI shows a mass which is
    hypointense to fat on T2. What is the most likely diagnosis?
    a. Thyroid opthalmopathy
    b. Lymphoma
    c. Cavernous haemangioma
    d. Capillary haemangioma
    e. Pseudotumour

Answer 11

11. e. Pseudotumour
    Pseudotumour is the commonest cause of an intra-orbital mass lesion in adults. It is an
    idiopathic inflammatory condition and about 10% of cases occur in association with
    autoimmune conditions such as retroperitoneal fibrosis.
    It usually presents with unilateral painful opthalmoplegia. It can be acute (more
    common) or chronic. The former has a more favourable prognosis as it is responsive to
    steroids. In contrast, the chronic type frequently requires chemotherapy and radiotherapy.
    On MRI, pseudotumour is hypointense to fat on T2, whereas true tumours are
    hyperintense.
    Grave’s disease is the most common cause of uni/bilateral proptosis in adults (85%
    bilateral, 15% unilateral). However, involvement of extra-ocular muscles tends to maximally
    affect the midportion with relative sparing of the tendinous insertions. This gives rise to the
    so-called ‘Coke-bottle’ sign.

Question 12

12. Which of the following best represents the decline in positive CT findings for a
    clinically suspected subarachnoid haemorrhage from scanning at 12 hours post-ictus
    to 3 days post-ictus?
    a. 90% positive at 12 hours to 70% positive at 3 days
    b. 90% positive at 12 hours to 60% positive at 3 days
    c. 98% positive at 12 hours to 90% positive at 3 days
    d. 98% positive at 12 hours to 75% positive at 3 days
    e. 90% positive at 12 hours to 50% positive at 3 days

Answer 12

12. d. 98% positive at 12 hours to 75% positive at 3 days

Question 13

13. A 20 year old female is under investigation for periodic halitosis. A CT scan reveals a
    well-defined, hypodense mass located between the longus colli muscles. There is no
    enhancement post-contrast injection. MRI demonstrates a midline cystic structure in
    the posterior roof of the nasopharynx. It shows high signal intensity on both T1 and
    T2 sequences. The most likely diagnosis is:
    a. Benign polyp
    b. Rathke’s pouch cyst
    c. Ranulas
    d. Tornwaldt’s cyst
    e. Thyroglossal duct cyst

Answer 13

13. d. Tornwaldt’s cyst
    Tornwaldt’s cyst is a benign mass typically located in the midline, between the longis colli
    muscles, in the posterior nasopharynx. They arise as a result of a focal adhesion between the
    ectoderm and regressing notochord. This causes the creation of a pouch but when the
    communication with the pouch is lost, a cyst develops.
    Tornwaldt’s cysts are usually asymptomatic and are picked up as incidental findings.
    Periodically, the pressure within the cyst increases causing the release of its contents into the
    nasopharynx. This leads to presentations including halitosis, foul taste in the mouth and
    persistent nasopharyngeal drainage. Peak age at presentation is 15–30 years.
    Imaging features can vary depending on the protein content within the cyst but typical
    features are of a well-delineated, thin-walled, midline cystic lesion measuring 2–10mm in
    diameter. They are hypodense on CT, rarely calcify and do not enhance. They can be high
    or low on T1 (depending on protein content) but are high on T2-weighted imaging.
    Rathke’s pouch cysts are located anterior and cephalad to Tornwaldt’s cysts.

Question 14

14. You are called by a paediatrician to perform a cranial ultrasound on a term neonate
    who requires intensive therapy following delivery. Ultrasound demonstrates a welldefined
    area of increased parenchymal echogenicity over the periphery of the right
    parietal lobe. What is the most likely diagnosis?
    a. Germinal matrix haemorrhage
    b. Venous infarction
    c. Middle cerebral artery infarction
    d. Periventricular leukomalacia
    e. Subarachnoid haemorrhage

Answer 14

14. c. Middle cerebral artery (MCA) infarction
    Vascular occlusive disease is rare in the neonatal period. When present, it is more common
    in the term infant and usually results from thrombosis rather than embolism. The MCA is
    most commonly involved. Aetiology includes: traumatic delivery, vasospasm due to meningitis
    and emboli secondary to congenital heart disease. Ultrasound demonstrates echogenic
    parenchyma in the distribution of the arterial territory.

Question 15

15. A 14 year old boy presents with a progressive history of gait and speech disturbance.
    On both T1- and T2-weighted MR imaging, the globus pallidi are markedly hypointense
    except for a small central region of high signal intensity. The findings are more
    pronounced on T2-weighted imaging. What is the most likely diagnosis?
    a. Leigh’s disease
    b. Hallervorden–Spatz syndrome
    c. Wilson disease
    d. Mytochondrial encephalomyelopathy
    e. Parkinson’s disease

Answer 15

15. b. Hallervorden–Spatz (HS) syndrome
    The finding described on MRI is the ‘eye-of-the-tiger’ sign. This is closely associated with
    HS. HS is a progressive neurodegenerative metabolic disorder characterised by extrapyramidal
    and pyramidal signs. The condition (for which the pathophysiology is unclear)
    results in the accumulation of iron within the globus pallidi and brainstem nuclei. Two
    clinical entities exist: familial and sporadic. The familial (classic) form shows earlier onset
    and rapid progression. The sporadic (atypical) form is characterised by a later onset, often
    in teenage years, with slower progression.
    Although the ‘eye-of-the-tiger’ sign is closely associated with HS, it has been demonstrated
    in other rare extrapyramidal parkinsonian disorders including cortical-basal
    ganglionic degeneration, early-onset levodopa-unresponsive parkinsonism and progressive
    supranuclear palsy.

Question 16

16. A 45 year old woman undergoes investigation for conductive hearing loss. History
    reveals several previous ear infections. Direct visualisation with an otoscope shows
    a mass behind an intact tympanic membrane. Coronal CT imaging demonstrates
    a soft-tissue mass located between the lateral attic wall and the head of the malleus.
    There is blunting of the scutum. The mass does not enhance post-contrast. What is
    the most likely diagnosis?
    a. Chronic otitis media
    b. Cholesterol granuloma
    c. Cholesteatoma
    d. Rhabdomyosarcoma
    e. Squamous cell carcinoma

Answer 16

16. c. Cholesteatoma
    A cholesteatoma consists of a sac lined with stratified squamous epithelium and filled with
    keratin – essentially ‘skin growing in the wrong place’.
    They can be acquired (98%) or congenital (2%). Most acquired cholesteatomas arise in
    the superior portion of the tympanic membrane (pars flaccida) and extend into Prussak’s space where they can cause medial displacement of the head of the malleus and erosion of
    the bony scutum.
    The characteristic imaging feature of a cholesteatoma is bone erosion associated with a
    non-enhancing soft-tissue mass.
    Complications can be intratemporal and intracranial:
    Intratemporal: ossicular destruction, facial nerve paralysis, labyrinthine fistula, complete
    hearing loss, automastoidectomy.
    Intracranial: meningitis, sinus thrombosis, abscess, CSF rhinorrhea.

Question 17

17. A 52 year old man with known chronic myeloid leukaemia complains of left-sided
    facial pain. Plain radiographs show a poorly defined lytic lesion centred over the left
    maxilla. Further imaging with CT and MR demonstrates an enhancing, homogeneous
    mass with infiltrative margins, which returns intermediate signal on T1 and T2
    sequences. The most likely diagnosis is:
    a. Granulocytic sarcoma
    b. Lymphoma
    c. Osteomyelitis
    d. Myeloma
    e. Neuroblastoma

Answer 17

17. a. Granulocytic sarcoma
    Granulocytic sarcoma is a rare complication of acute and chronic myeloid leukaemia (AML
    & CML), occurring in approximately 3% of patients. It is a soft-tissue infiltrate of immature
    myeloid elements. The mean age at presentation is 48 years and most patients present with a
    solitary lesion. In the head and neck, they have been reported in the skull, face, orbit and
    paranasal sinuses. Extramedullary lesions have been reported in the tonsils, the oral and
    nasal cavities and within the lacrimal, thyroid and salivary glands.
    They are also referred to as chloromas, a term used to describe their green colour seen on
    sectioning.
    The prognosis of patients with AML does not change in the presence of a chloroma,
    however, in patients with CML it may represent worsening of the disease as their presence is
    associated with the acute or blastic phase. Approximately 30% of patients with chloromas
    have no haematological disease at the time of presentation.

Question 18

18. A 28 year old woman presents with a mass in her neck. She gives a history of multiple
    parotid abscesses which have been refractory to drainage and antibiotics. The mass
    is located at the anteromedial border of her right sternocleidomastoid muscle. Ultrasound
    demonstrates a compressible mass with internal debris which is devoid of
    internal flow on Doppler imaging. MRI shows a cystic mass consisting of a curved rim of tissue pointing medially between the internal and external carotid arteries. There is
    slight capsular enhancement. What is the most likely diagnosis?
    a. Cervical abscess
    b. Necrotic neural tumour
    c. Submandibular gland cyst
    d. Necrotic inflammatory lymphadenopathy
    e. Second branchial cleft cyst

Answer 18

18. e. Second branchial cleft cyst
    Failure of involution of branchial clefts can lead to branchial cleft cysts, fistulae and/or
    sinuses. Second branchial cleft cysts account for 95% of all branchial cleft anomalies. Male
    and female incidence is equal and the typical age of presentation is 10–40 years.
    Second branchial cleft cysts are classified into four types depending on their location. The
    most common is type II, which occurs along the anterior surface of the sternocleidomastoid
    muscle, lateral to the carotid space and posterior to the submandibular gland adhering to
    the great vessels.
    On CT/MR the ‘beak sign’ is pathognomonic. This is a curved rim of tissue pointing
    medially between the internal and external carotid arteries.

Question 19

19. A 72 year old man from a nursing home presents to the accident and emergency
    department. Nurses have noticed increasing confusion following a fall six days earlier.
    His inflammatory markers are normal. A non-contrast CT scan of the head demonstrates
    a crescent-shaped collection in the left fronto-parietal region. The collection is
    isodense to CSF and there is no midline shift, nor hydrocephalus. On T1-weighted MR
    imaging the lesion is isointense to CSF. The most likely diagnosis is:
    a. Subdural hygroma
    b. Brain atrophy
    c. Subdural empyema
    d. Chronic subdural haematoma
    e. Enlarged subarachnoid space

Answer 19

19. a. Subdural hygroma
    This is a traumatic subdural effusion which shows up as a localised CSF-fluid collection
    within the subdural space. They present in the elderly or in young children usually 6–30
    days following trauma. The majority are asymptomatic but patients may present with
    increasing confusion or headaches. They are devoid of blood products on imaging, unlike
    chronic subdural haematomas. Subdural haematomas are also more likely to cause effacement
    of the ventricular system and loss of the normal sulci-gyral pattern.
    Normal inflammatory markers and lack of pyrexia lessen the probability of an empyema

Question 20

20. A 40 year old man undergoes investigation for seizures. Head CT with and without
    contrast shows a large, round, sharply marginated, hypodense mass involving the
    cortex and subcortical white matter of the left frontal lobe. The mass contains large
    nodular clumps of calcification. There is surrounding oedema and ill-defined enhancement.
    MRI demonstrates a heterogeneous mass which is predominantly isointense to
    grey matter on T1 and hyperintense on T2. There is moderate enhancement. What is
    the most likely diagnosis?
    a. Astrocytoma
    b. Ganglioglioma
    c. Ependymoma
    d. Glioblastoma
    e. Oligodendroglioma

Answer 20

20. e. Oligodendroglioma
    This is an uncommon glioma which usually presents as a large mass at the time of
    diagnosis. Mean age is 30–50 years and they are more common in men than women. The
    majority are located in the frontal lobe (60%), although they can occur anywhere within
    the central nervous system, including the cerebellum, brainstem, spinal cord, ventricles and
    optic nerve.
    Large nodular clumps of calcifications are present in up to approximately 90% of
    tumours. Cystic degeneration and haemorrhage are uncommon. Prognosis depends on
    the grade of the tumour. High-grade tumours show 20% ten-year survival whereas lowgrade
    tumours show 46% ten-year survival.
    Although astrocytomas can calcify, the calcifications are rarely large and nodular.
    Glioblastomas rarely calcify. Gangliogliomas are more common in the temporal lobes
    and deep cerebral tissues and the majority of them (80%) occur below the age of 30 years.
    Ependymomas often demonstrate fluid levels due to internal haemorrhage.

Question 21

21. A 52 year old man presents following collapse. He was previously fit and well,
    describing only a relatively recent history of dull back pain. Initial CT scan of the
    head reveals a 1.5 cm hyperdense mass at the corticomedullary junction of the right
    cerebral hemisphere. The mass shows surrounding oedema which exceeds the volume
    of the lesion. There is strong lesional enhancement following contrast injection. What
    is the most likely diagnosis and subsequent management?
    a. Glioblastoma multiforme with subsequent MRI of the brain
    b. Prostatic cancer metastasis with digital rectal examination and measuring of the
    prostatic specific antigen
    c. Acute haemorrhagic contusion with referral to the neurosurgeons for active
    monitoring
    d. Renal cell metastasis with subsequent CT staging
    e. Brain abscess with subsequent intravenous antibiotics

Answer 21

21. d. Renal cell metastasis with subsequent CT staging
    Brain metastases account for approximately a third of all intracranial tumours and are the
    most common intracranial neoplasm. They characteristically occur at the corticomedullary
    junction of the brain and have surrounding oedema that typically exceeds the tumour
    volume. Multiple lesions are present in approximately two-thirds of cases and should be
    searched for with administration of intravenous contrast. Most are hypodense on CT unless
    haemorrhagic or hypercellular, hence the lesion in this case is haemorrhagic. This lends
    itself to a differential of primary neoplasms which includes melanoma, renal cell carcinoma,
    thyroid carcinoma, bronchogenic carcinoma and breast carcinoma. The history of back
    pain also suggests bone metastases.
    Glioblastoma multiforme usually appears as an irregular, heterogeneous, low-density
    mass. Abscesses typically demonstrate ring enhancement post-contrast and may show
    loculation and specules of gas. The patient’s history describes collapse rather than headache
    or confusion following a fall, which moves the differential away from traumatic contusion.
    Although prostate cancer typically metastasises to the vertebrae, it is an uncommon
    primary site for brain metastases, especially as the lesion described is haemorrhagic

Question 22

22. Which of the following best describes the appearance of an acute ischaemic infarct of
    the brain?
    a. Hypointense on diffusion-weighted (DW) MRI and low apparent diffusion
    coefficient (ADC) values.
    b. Hyperintense on DW MRI and low ADC values
    c. Hypointense on DW MRI and high ADC values
    d. Hyperintense on DW MRI and high ADC values
    e. Isointense on DW MRI and low ADC values

Answer 22

22. b. Hyperintense on DW MRI and low ADC values
    Diffusion-weighted imaging is dependent on the motion of water molecules and provides
    information on tissue integrity. It is thought that interruption of cerebral blood flow results
    in rapid breakdown of energy metabolism and ion exchange pumps. This causes a shift of
    water from the extracellular compartment into the intracellular compartment, giving
    cytotoxic odema. This produces the hyperintensity on DW MR images.
    ADC values tend to be low within hours of stroke and continue to decline for the next
    few days. They remain reduced through the first four days and then show pseudonormalisation
    between four and ten days. After ten days the ADC tends to rise.
    Hyperintensity on diffusion-weighted (DW) MRI and low ADC values are not pathognomonic
    of acute infarction but sensitivities and specificities of 94% and 100% have been
    reported. Other conditions including haemorrhage, abscesses, lymphoma and Creutzfeldt–
    Jacob disease have been described.

Question 23

23. A 30 year old female complains of increasing headaches, episodic vomiting and
    drowsiness. Fundoscopy reveals papilloedema. Non-contrast CT of the head demonstrates
    hydrocephalus and a globular lesion within the lateral ventricle. There are
    several small internal foci of calcification. MR shows the mass to be attached to the
    septum pallucidum. It is isointense to grey matter on T1 and T2. It densely enhances
    after intravenous gadolinium. What is the most likely diagnosis?
    a. Ependymoma
    b. Subependymoma
    c. Central neurocytoma
    d. Heterotopic grey matter
    e. Meningioma

Answer 23

23. c. Central neurocytoma
    Central neurocytoma is an intraventricular WHO grade II neuroepithelial tumour with
    neuronal differentiation. This rare neoplasm tends to occur between the ages of 20–40
    years. Patients typically present with symptoms and signs of hydrocephalus.
    Imaging typically demonstrates a globular lesion attached to the septum pellucidum.
    Calcification is considered characteristic, however it may be absent in approximately half
    the cases. On MRI, the lesions are usually isointense to grey matter and show dense contrast
    enhancement. It is extremely uncommon to see peritumoural oedema.
    Heterotopic grey matter should not enhance, contain calcium, nor be attached to the
    septum pellucidum. Intraventricular meningiomas are typically located at the trigone.
    Subependymomas are hyperintense to grey matter on T2 while ependymomas tend to be
    heterogeneous, childhood lesions that occur in and around the fourth ventricle.

Question 24

24. Which is the preferred sequence to use when attempting to identify posterior fossa
    lesions on MRI in patients with multiple sclerosis?
    a. T1-weighted spin-echo
    b. T2-weighted spin-echo
    c. FLAIR
    d. Gradient-echo
    e. Proton density

Answer 24

24. b. 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 periventricularly.
    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

Question 25

25. A 35 year old man attends the accident and emergency department complaining of episodic lower back pain radiating down the legs. History and clinical examination also suggest pelvic sphincter dysfunction. MRI shows a spinal cord mass located at the conus medullaris. The mass is isointense on T1 and hyperintense on T2. It demonstrates contrast enhancement. The most likely diagnosis is: a. Astrocytoma b. Intradural lipoma c. Haemangioblastoma d. Myxopapillary ependymoma e. Ganglioglioma

Answer 25

25. d. Myxopapillary ependymoma This is a variant of ependymoma and is the most common neoplasm of the conus medullaris. It originates from ependymal glia of the filum terminale. Average age at presentation is 35 years and it is more common in men. T1-weighted imaging shows an isointense or occasionally hyperintense (due to the mucin content) mass. It is hyperintense on T2 and almost always shows enhancement postcontrast. Intradural lipomas are hyperintense on T1-weighted imaging but they should not enhance. They also tend to occur in younger individuals and usually have an associated, clinically apparent lumbosacral mass. Haemangioblastoma can also demonstrate high signal on T1 but is also highly vascular, can show signal voids and approximately half of them will have an intratumoural cystic component. Gangliogliomas are much more common at the cervical and thoracic levels.

Question 26

26. A 13 year old boy is investigated for chronic headache and visual disturbance. CT shows a well-defined mass in the left middle cranial fossa. It is isodense to CSF. There are no calcifications, no surrounding oedema and no contrast enhancement. There is erosion of the underlying calvarium. You suspect this is an arachnoid cyst but your consultant suggests the possibility of an epidermoid cyst. What MR imaging sequence would best differentiate the two? a. Diffusion-weighted MR imaging b. Gadolinium-enhanced T1-weighted imaging c. Proton density imaging d. MR spectroscopy e. Perfusion-weighted MR imaging

Answer 26

26. a. Diffusion-weighted MR imaging Epidermoid and arachnoid cysts can look very similar on CT and standard MRI T1- and T2-weighted imaging. Both demonstrate signal intensity similar to CSF. Arachnoid cysts and the majority of epidermoid cysts do not calcify nor enhance. Arachnoid cysts are typically found in the floor of the middle cranial fossa near the tip of the temporal lobe (50%). Although intracranial epidermoid cysts are more commonly found at the cerebellar pontine angle, they may be found in the middle cranial fossa. Both arachnoid and epidermoid cysts may have associated bone erosion indicating their chronicity. Diffusion-weighted imaging is useful at distinguishing between the two as epidermoids appear bright indicating the marked restriction of water diffusion. Arachnoid cysts appear dark in keeping with signal from CSF.

Question 27

27. A three year old girl undergoes a CT scan of her head following trauma. No acute pathology is demonstrated but there is basal ganglia calcification. Which of the following can be excluded as a cause of the calcification? a. Down’s syndrome b. Neurofibromatosis c. Birth hypoxia d. Wilson disease e. Congenital rubella

Answer 27

27. d. Wilson disease Causes of basal ganglia calcification include:  Physiological aging.  Infections/inflammatory: TORCH, TB, cysticercosis, measles, chickenpox, pertussis, Coxsackie B virus, AIDS, SLE.  Toxins: lead, carbon monoxide, birth anoxia/hypoxia, chemotherapy/radiotherapy, nephrotic syndrome.  Congenital: Cockayne’s, Fahr’s and Down’s syndromes, neurofibromatosis, tuberous sclerosis, methaemaglobinopathy.  Endocrine: hypothyroidism, hypoparathyroidism, pseudhypoparathyroidism, pseudopseudohypoparathyroidism, hyperparathyroidism.  Metabolic: Leigh disease, mitochondrial cytopathies.  Trauma: infarction.

Question 28

28. The husband of a 33 year old woman takes her to the local accident and emergency department, stating that she is becoming acutely confused and is not her normal self. Her past medical history is unremarkable apart from a flu-type illness a few days earlier. Her GCS is 13 (E – 4, V – 3, M – 6). Initial non-contrast-enhanced CT of the brain shows low-density change within the left temporal lobe. MRI demonstrates abnormal low signal on T1 and high signal on T2 within the left temporal cortex. The insula is involved but there is sparing of the putamen. There is mild mass effect with partial effacement of the lateral ventricles. What is the most likely diagnosis? a. Herpes simplex encephalitis b. Low-grade glioma c. Brain abscess d. Post-viral leukoencephalopathy e. Dural sinus thrombosis leading to cerebral infarction

Answer 28

28. a. Herpes simplex encephalitis (HSE) There are two main types of herpes simplex virus (HSV) – HSV type I and HSV type II. Type I (oral herpes) tends to affect older infants, children and adults whereas type II (genital herpes) is the usual cause of HSE in neonates. HSE is a necrotising meningoencephalitis which has a predilection for the limbic system (temporal lobes, insula, cingulated gyri). Characteristically, there are poorly defined areas of low attenuation in one or both temporal lobes/limbic system on unenhanced CT, low signal on T1 (gyral oedema) and high signal on T2. The T2 high signal typically spares the putamen and forms a sharply defined border. Changes may initially appear unilateral but contralateral disease invariably follows. This sequential bilaterality is characteristic of HSE. Haemorrhage is typically a late finding. Mortality ranges from 30% to 70% but is reduced with early antiviral therapy

Question 29

29. A 58 year old man presents with impaired vision and intractable headaches. He has a past history of recurrent sinusitis. Examination reveals left-sided proptosis and a palpable mass in the superomedial aspect of the orbit. CT demonstrates a soft-tissue mass causing expansion and erosion of the left frontal sinus. There is peripheral enhancement post-contrast injection. The next radiological step should be: a. Referral to an appropriate clinician – you have made a confident diagnosis of a benign aetiology b. MRI of the head and neck – you have made a confident diagnosis of a malignant aetiology and wish to stage its local spread c. MRI of the head and neck – you are unsure of the nature of the aetiology and want to further characterise it d. Perform a staging CT – you are concerned this may be metastatic disease e. Perform an ultrasound scan of the orbit – to further characterise the lesion

Answer 29

29. a. Referral to an appropriate clinician – you have made a confident diagnosis of a benign aetiology This is almost certainly a mucocoele. Mucocoeles represent the end stage of a chronically obstructed sinus. They most commonly affect the frontal sinus (60%), with ethmoid (30%), maxillary (10%) and sphenoid (rare) following respectively. Patients present with symptoms as described in the question. Increased intrasinus pressure results in expansion and erosion of the sinus walls. There may be a surrounding zone of bone sclerosis. Contrast injection typically reveals rim enhancement, which helps to differentiate from the more solid enhancement pattern of neoplasms.

Question 30

30. Regarding radionuclide imaging of thyroid cancers, which radiological finding best fits the diagnosis? a. Usually concentrates radioiodine – follicular carcinoma b. Usually concentrates pertechnetate – papillary carcinoma c. Usually concentrates pertechnetate and radioiodine – papillary carcinoma d. No radioiodine or pertechnetate uptake but frequently concentrates thallium-201 – medullary carcinoma e. No radioiodine or pertechnetate uptake but frequently concentrates thallium-201 – anaplastic carcinoma

Answer 30

30. d. No radioiodine or pertechnetate uptake but frequently concentrates thallium- 201 – medullary carcinoma Types of thyroid carcinoma in order of worsening prognosis are papillary, follicular, medullary and anaplastic. Papillary tumours usually concentrate radioiodine, follicular tumours concentrate pertechnetate but fail to accumulate radioiodine, and anaplastic tumours show no radioiodine uptake

Question 31

31. A patient known to have AIDS presents with increasing malaise and confusion. CT brain shows multiple cerebral hypoattenuating nodular lesions with varying degrees of surrounding oedema and mass effect. There is lesional enhancement post-contrast administration. Which of the following conditions can be confidently removed from the differential diagnosis? a. Tuberculosis b. Pyogenic abscesses c. Progressive multifocal leukoencephalopathy d. Lymphoma e. Toxoplasmosis

Answer 31

31. c. Progressive multifocal leukoencephalopathy Progressive multifocal leukoencephalopathy affects about 4% of AIDS patients and is caused by reactivation of ubiquitous JC papovavirus. This causes lysis of oligodendrocytes resulting in demyelination. CT shows single or multiple hypoattenuating white matter lesions without oedema/mass effect. There may also be grey matter lesions in the thalamus/ basal ganglia from involvement of traversing white matter tracts. The majority of patients show mild cortical atrophy. The condition carries a poor prognosis with death within two to five months. All the other conditions listed will have various amounts of surrounding oedema/mass effect and enhance post-contrast. Toxoplasmosis is the most common cerebral mass lesion in AIDS and is two or three times more frequent than lymphoma (the second most common cause of a CNS mass in AIDS). Multiple lesions suggest toxoplasmosis over lymphoma, however when there is a solitary lesion the probability of lymphoma is at least equal to that of toxoplasmosis.

Question 32

32. Which of the following neurological imaging findings would offer a clear differential diagnosis between tuberous sclerosis and neurofibromatosis Type I? a. Basal ganglia calcification b. Optic nerve glioma c. Cerebral astrocytoma d. Enhancing heterotopic grey matter e. Multiple foci of hyperintensity on T2-weighted imaging

Answer 32

32. d. Enhancing heterotopic grey matter All of the other features may be found in either condition. Giant cell astrocytomas located in the region of the foramen of Monro in tuberous sclerosis may degenerate into high-grade astrocytomas. Cortical tubers show as multiple nodules which are hyperintense on T2/FLAIR imaging. CNS hamartomas (occurring in up to 75–90% of NF1) also display these characteristics – they are often termed ‘unidentified bright objects’.

Question 33

33. A 65 year old woman is investigated for enophthalmos and headache. She is cachetic, anaemic and you suspect a metastatic process. CT head demonstrates an infiltrative retrobulbar mass. What is the most likely site of primary disease? a. Breast b. Lung c. Renal d. Melanoma e. Ovarian

Answer 33

33. a. Breast Most retrobulbar metastases are extraconal (outside the muscle cone). Neuroblastoma and Ewing’s sarcoma are the most common in children and produce smooth extraconal masses related to the posterior lateral wall of the orbit. In adults, an infiltrative retrobulbar mass and enophthalmos is characteristic of scirrhous carcinoma of the breast (invasive ductal carcinoma). Enophthalmia is also considered to be one of the earliest signs of metastatic breast cancer.

Question 34

34. A 40 year old man with no previous medical history or medication attends the accident and emergency department. He was the driver of a car that was involved in a car-on-car vehicle collision at approximately 40 mph. He was wearing a seat belt and his airbag deployed appropriately. According to NICE guidelines for head injury, which one of the following criteria alone does not warrant an acute head CT scan? a. GCS <15 when he was assessed in the emergency department two hours after the accident b. Haemotympanum c. Amnesia of events <30 minutes after impact d. Seizure following the accident e. More than one episode of vomiting following the accident

Answer 34

34. c. Amnesia of events <30 minutes after impact NICE defines head injury as ‘any trauma to the head, other than superficial injuries to the face’. All of the other criteria listed are requisites for an acute head CT scan. Haemotympanum implies a basal skull fracture which should be investigated by CT. Amnesia of events >30 minutes before impact would require an acute head CT. Any amnesia or loss of consciousness since the injury requires a CT scan if the patient is equal to or older than 65 years, has a coagulopathy (including warfarin treatment) or if there is a history of dangerous mechanism of injury, which is listed as:  Pedestrian or cyclist struck by a motor vehicle.  Occupant ejected from a motor vehicle.  Fall from over one metre or five stairs.

Question 35

35. 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? 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

Answer 35

35. d. T2 fat-suppressed in the axial plane

Question 36

36. A 30 year old man presents with an orbital frontal headache and visual disturbance. CT head shows a large mass arising from the region of the spheno-occiput and extending into the pontine cistern and towards the hypothalamus. The mass contains amorphous calcification and is seen to cause bone destruction. There is no reactive bone sclerosis. On MRI the mass exhibits mixed heterogeneous signal and a soapbubble appearance. The solid components show marked contrast enhancement. What is the most likely diagnosis? a. Meningioma b. Metastasis c. Chordoma d. Plasmacytoma e. Sphenoid sinus cyst

Answer 36

36. c. Chordoma Chordomas originate from malignant transformation of notochordal cells. They are typically located in the sacrum (50%), clivus (35%) and vertebrae (15%). They may rarely be found in the mandible, maxilla and scapula. Spheno-occipital chordomas typically affect males and females in equal incidence and the average age ranges from 20 to 40 years. The majority of them demonstrate bone destruction and amorphous calcification. The solid components show variable but often marked contrast enhancement and MRI may show a ‘soap-bubble’ appearance. Bone sclerosis is rare. The description given is that of a malignant process. Meningiomas typically affect older females and only rarely (<1%) arise from the clivus. Plasmacytomas tend to occur in an older age group, are more common in the thoracic/lumbar spine and are often osteolytic and grossly expansile lesions. Metastasis is a possibility, although from the description given – particularly the calcification and amount of tumour extension – chordoma remains the most likely diagnosis.

Question 37

37. A 50 year old woman presents with a palpable lump in her neck. Imaging demonstrates a malignant-looking mass in the thyroid gland. Which of the following findings would direct you towards a confident diagnosis? a. Complex mass with areas of necrosis – papillary carcinoma b. Calcified lymph nodes – medullary carcinoma c. Osteosclerotic bone metastases – follicular carcinoma d. Intratumoural calcifications – anaplastic carcinoma e. Regional lymphadenopathy – anaplastic carcinoma

Answer 37

37. b. Calcified lymph nodes – medullary carcinoma Lymph node calcification accompanied by a thyroid tumour is highly suggestive of medullary carcinoma. This tumour arises from parafollicular C-cells and can cause elevated calcitonin levels. The familial form of medullary carcinoma is associated with MEN II (parathyroid hyperplasia, phaeochromocytoma). All four carcinomas may demonstrate calcification within the tumour and may also show various amounts of necrosis. Follicular carcinoma typically shows early haematogenous spread and metastases to bone are almost always osteolytic. Although rare, papillary carcinoma can also spread to bone and the lungs. Approximately 75% of anaplastic carcinomas have associated regional lymphadenopathy, however, papillary (40% but almost 90% in children) and medullary (50%) also show regional lymphatic spread.

Question 38

38. A 38 year old gentleman presents with a dull ache in his jaw. There is minor swelling over the left mandible. Plain radiographs demonstrate an expansile, multilocular, radiolucent lesion with internal septations involving the left body of the mandible. It is associated with an impacted tooth. CT shows infiltration of the adjacent soft tissues. There are no discernable foci of calcification. What is the most likely diagnosis? a. Odontogenic myxoma b. Dentigerous cyst c. Odontogenic keratocyst d. Ameloblastoma e. Periapical cyst

Answer 38

38. d. Ameloblastoma Ameloblastoma (adamantinoma of the jaw) is a benign, locally aggressive lesion that occurs mainly in patients between 30 and 50 years of age. They are found in the mandible (75%) and the maxilla (25%) and are often associated with an impacted/unerupted tooth. When in the mandible, they typically occur in the region of the molars/angle of the mandible. Typically ameloblastomas are radiolucent lesions that contain septa or locules of variable size, which produce a honeycombed appearance. The margin is usually well defined but when large it can produce jaw expansion with perforation of the cortex. They may infiltrate adjacent soft tissues and show local recurrence following excision. Ameloblastomas may be unicystic but these tend to occur around the age of 20 years and there is also a very rare malignant variety which can cause lung metastases. Odontogenic keratocysts, dentigerous cysts, odontogenic myxomas and periapical cysts are invariably unilocular

Question 39

39. A middle-aged gentleman is diagnosed on imaging with suspected laryngeal carcinoma. Which of the following factors would favour a diagnosis of adenoid cystic carcinoma over squamous cell carcinoma? a. A history of long-term smoking b. Involvement of regional neck lymph nodes c. Invasion through laryngeal cartilage d. Supraglottic extension e. Propensity for nerve invasion

Answer 39

39. e. Propensity for nerve invasion Laryngeal adenoid cystic carcinoma accounts for approximately 1% of all malignant laryngeal tumours (cc. laryngeal carcinoma – 98%). Typically, there is an absent history of smoking and regional lymph nodes are hardly ever involved. Eighty per cent of them are subglottic (around the junction with the trachea) but they may spread through the entire larynx. Their characteristic feature is their propensity to invade nerves leading to paralysis

Question 40

40. Which of the following statements best describes the features of amyloid angiopathy? a. Solitary, peripheral haemorrhagic focus in a hypertensive elderly patient b. Solitary, central haemorrhagic focus in a normotensive young patient c. Multiple, peripheral haemorrhagic foci in a normotensive elderly patient d. Multiple, central haemorrhagic foci in a normotensive elderly patient e. Multiple, central haemorrhagic foci in a hypertensive young patient

Answer 40

40. c. Multiple, peripheral haemorrhagic foci in a normotensive elderly patient Multiple peripheral haemorrhages (corticomedullary junction) in normotensive elderly patients are suggestive of amyloid angiopathy. Hypertensive haemorrhage tends to occur centrally around the basal ganglia (putamen, external capsule), thalamus and pons.

Question 41

41. A seven year old boy presents with pain in his neck. His mother thinks she can feel a lump. Ultrasound shows a thick-walled cyst with internal echoes. It has a paramedian location within the strap muscles. MRI shows a heterogeneous cystic mass measuring 3 cm in diameter. It demonstrates high signal on T1 and contains areas of low signal on T2. There is marked enhancement of the wall after administration of gadolinium. What is the most likely diagnosis? a. Infected thyroglossal duct cyst b. Fibroma c. Branchial cleft cyst d. Teratoma e. Lymphangioma

Answer 41

41. a. Infected thyroglossal duct cyst Thyroglossal duct cysts arise from the remnants of the embryonic thyroglossal duct and account for up to 70% of congenital neck masses in children. Typically, children present with a non-tender mass that elevates on swallowing. If infected there may be pain, local tenderness and recent increased growth. Most are midline, although they become more paramedian below the level of the hyoid. Approximately 20% are suprahyoid, 15% occur at the level of the hyoid and 65% are infrahyoid. Generally they are thin-walled cysts and show typical cystic imaging characteristics. If infected or if the cyst has haemorrhaged, high signal may be seen on T1 and low signal may be present on T2-weighted MR images. Haemorrhage and infection may also cause thickening and marked enhancement of the wall.

Question 42

42. A three week old girl is investigated for a right orbital mass. CT shows a diffuse, poorly marginated mass in the superior temporal quadrant of the orbit. It is separate from the globe and the mass shows diffuse enhancement post-contrast injection. On MRI, the mass is hypointense to fat on T1 but hyperintense on T2. On both sequences, low-signal curvilinear foci are seen within it. What is the most likely diagnosis? a. Lymphangioma b. Rhabdomyosarcoma c. Cavernous haemangioma d. Retinoblastoma e. Capillary haemangioma

Answer 42

42. e. Capillary haemangioma Capillary haemangiomas are the most common vascular orbital masses in children. They typically present at birth or shortly after. CT shows a diffuse, usually poorly marginated mass which shows diffuse contrast enhancement. On MRI the mass is hypointense to fat on T1, and on T2 it is hyperintense to muscle and fat but hypointense compared to fluid. Curvilinear flow voids representing blood vessels are typical within the mass. They tend to grow rapidly over the first six months of life, stop growing during the second year and then slowly involute over subsequent years

Question 43

43. An eight year old boy with skin hyperpigmentation presents with deteriorating vision and hearing loss. CT shows large symmetric low-density lesions in the parietaloccipital white matter. T2-weighted MR imaging demonstrates confluent symmetric hyperintensity within the parietal-occipital white matter extending across the splenium of the corpus callosum. There is relative sparing of the frontal lobes. Follow-up MRI six months later shows cerebral atrophy and more extensive white matter change with involvement of the frontal lobes and cerebellum. At this point the patient had developed spastic quadriplegia. What is the most likely diagnosis? a. Multiple sclerosis b. Lymphomatoid granulomatosis c. Acute disseminated encephalomyelitis d. Adrenoleukodystrophy e. Autoimmune vasculitis

Answer 43

43. d. Adrenoleukodystrophy (ALD) ALD is an inherited metabolic disorder characterised by progressive demyelination of cerebral white matter. It is commonly X-linked recessive and boys present between the ages of 3 and 12 years with ataxia, deteriorating vision, hearing loss, altered behaviour and mental deterioration. It is associated with adrenal insufficiency (Addison’s disease). Predominantly, there is posterior white matter involvement with the disease advancing toward the frontal lobes and cerebellum. Imaging shows CT hypodensity, MR T1 hypointensity and T2 hyperintensity. Administration of contrast shows enhancement of the lateral margins of the lesions, indicating areas of active demyelination. Acute disseminated encephalomyelitis is an autoimmune reaction against the patient’s white matter. It may present within days or weeks following an exanthematous viral reaction or vaccination. Imaging demonstrates multifocal hypodense (CT)/hyperintense (T2 MRI), usually asymmetrical, white matter abnormalities. Corticosteroids result in dramatic improvement and follow-up scans show no additional lesions.

Question 44

44. A 49 year old woman with AIDS presents with increasing headache. T1-weighted MR imaging demonstrates a hypointense lesion in the periventricular white matter of the left parietal lobe. The lesion is hypointense on FLAIR sequencing and is seen to cross the splenium of the corpus callosum. There is peripheral enhancement post-contrast injection. The most likely diagnosis is: a. Toxoplasmosis b. Progressive multifocal leukoencephalopathy c. Primary CNS lymphoma d. Cryptococcosis e. Tuberculosis

Answer 44

44. c. Primary CNS lymphoma (PCNSL) PCNSL is the second most common cause of a CNS mass in patients with AIDS (behind toxoplasmosis). Typical features include periventricular location with subependymal spread and crossing of the corpus callosum. Non-contrast CT may show a hyperdense lesion due to dense cellularity (for this reason it may also be hypointense on T2/FLAIR). There is often a paucity of oedema and frequent ring enhancement due to central necrosis (note this is in contrast with the solid homogeneous enhancement seen with lymphoma in the immunocompetent patient). Cryptococcosis is the most common cause of fungal infection in AIDS patients. CT is frequently normal and MRI shows low T1 and high T2 signal intensities without enhancement in the lenticulostriate region. Progressive multifocal leukoencephalopathy typically shows bilateral white matter lesions in the periventricular region, centrum semiovale or subcortical white matter, which are hypointense on T1 and hyperintense on T2/FLAIR. There is typically no oedema nor mass effect and no contrast enhancement.

Question 45

45. A homeless adult male is admitted with a change in mental state and a metabolic abnormality. CT shows a focus of reduced attenuation in the pons. On MRI the focus is hypointense on T1 and hyperintense on T2. There is restricted diffusion on diffusionweighted imaging and there is no enhancement post-contrast. What is the most likely diagnosis? a. Brainstem glioma b. Metastasis c. Infarction d. Tuberculosis e. Osmotic myelinolysis

Answer 45

45. e. Osmotic myelinolysis Osmotic myelinolysis is also referred to as central pontine myelinolysis or osmotic demyelination syndrome. It is classically seen in an alcoholic, hyponatraemic patient in which rapid correction of sodium releases myelinotoxic compounds leading to destruction of myelin sheaths. The pons is the commonest site, although extra-pontine areas such as basal ganglia, cerebellar white matter and thalami may also be involved. Some patients completely recover but the six-month survival rate is only 5–10%. Brainstem gliomas tend to occur in children and young adults. Typically the brainstem is asymmetrically expanded with displacement/compression of adjacent cisterns. Local vessels may also be displaced. Enhancement is variable. Pontine/medulla infarcts account for approximately 2% of all brain infarcts. They may show similar appearances to those described in the question but may also demonstrate enhancement. One would expect enhancement with metastasis

Question 46

46. A 33 year old male with no significant past medical history presents with headache, drowsiness and confusion. CT shows a hypodense lesion with a smooth regular wall centred over the left lentiform nucleus. There is surrounding oedema and mass effect with effacement of the ipsilateral Sylvian fissure. On T2-weighted MR imaging, the lesion is hyperintense and is surrounded by a hypointense rim and hyperintense oedema. There is peripheral enhancement post-contrast injection, and diffusion-weighted imaging demonstrates restricted diffusion within the lesion. What is the most likely diagnosis? a. Glioblastoma multiforme b. Pyogenic abscess c. Toxoplasmosis d. Lymphoma e. Metastasis

Answer 46

46. b. Pyogenic abscess The differential diagnosis for a solitary ring-enhancing lesion of the brain includes (‘MAGICAL DR’): Metastasis; Abscess; Glioma/Glioblastoma multiforme; Infarction; Contusion; AIDS (toxoplasmosis); Lymphoma (often AIDS-related); Demyelinating disease; Resolving haematoma/Radiation necrosis. Classically, abscesses are located at the corticomedullary junction in the frontal and temporal lobes. The most common causative organism is Streptococcus. The wall is generally smooth and regular with relative thinning of the medial wall secondary to a poorer blood supply from white matter (neoplastic lesions usually have a thick, nodular, irregular rim). In this scenario, the enhancing, T2-hypointense rim suggests abscess. Restricted diffusion is also highly suggestive of an abscess. Lymphoma may be hyperdense on CT due to a high nuclear-to-cytoplasmic ratio and typically shows solid homogeneous enhancement in immunocompetent patients.

Question 47

47. A 15 year old girl presents with suspected optic neuritis. Post-contrast T1-weighted imaging shows enhancement and mild enlargement of the right optic nerve. Several months later the girl re-presents with symptoms of myelitis. Sagittal T2-weighted imaging of the spine demonstrates intramedullary T2 hyperintensity and cord expansion extending from C1 to T1. At the time of the initial and subsequent presentations, brain imaging was normal. What is the most likely diagnosis? a. Multiple sclerosis b. Sarcoidosis c. Devic syndrome d. Neurofibromatosis e. Ependymoma

Answer 47

47. c. Devic syndrome (DS) Devic syndrome (neuromyelitis optica (NMO)) is a severe demyelinating syndrome characterised by optic neuritis and acute myelitis. There is substantial evidence that DS is distinct from multiple sclerosis (MS). DS may spare the brain, the spinal lesions are much larger than in MS and the serum autoantibody NMO-IgG is greater than 90% specific for DS patients and is not detected in classical MS patients. The proposed diagnostic criteria for Devic syndrome are optic neuritis and acute myelitis plus at least two of three supporting criteria: 1. Contiguous spinal cord MRI lesion extending over greater than or equal to three vertebral segments. 2. Brain MRI not meeting diagnostic criteria for multiple sclerosis. 3. NMO-IgG seropositive status.

Question 48

48. A five year old boy presents with visual fixation. The ophthalmologist suspects optic nerve hypoplasia. Brain CT confirms optic nerve hypoplasia, an absent septum pellucidum and a third cerebral abnormality. What is the third abnormality likely to be? a. Schizencephaly b. Cortical dysplasia c. Polymicrogyria d. Agenesis of the corpus callosum e. Type II Chiari malformation

Answer 48

48. a. Schizencephaly The combination of absent septumpellucidumand optic nerve hypoplasia is indicative of septooptic dysplasia (SOD). Most patients present in infancy with visual disturbance, seizures or endocrine abnormalities (pituitary dysfunction is seen in approximately 50% of cases). Additional abnormalities are often present with schizencephaly being the most common (50%). (Ref: Miller SP et al. Septo-optic dysplasia plus: a spectrum of malformations of cortical development.

Question 49

49. A 29 year old woman undergoes a brain CT for severe worsening headache. She is 20 weeks pregnant. No acute pathology is demonstrated. However, an incidental finding of a small right parietal arteriovenous malformation is noted. This is confirmed on subsequent MRI. You are asked to counsel the patient. What is the most appropriate advice? a. Normally the risk of haemorrhage is 2–3% per year but this increases by a factor of 10 during pregnancy. Recommend monthly follow-up with brain MRI b. Normally the risk of haemorrhage is 10% per year but haemorrhage is likely during labour. Recommend angiography with a view to coil embolisation c. Normally the risk of haemorrhage is 10% per year but there is no significant increase in risk during pregnancy. Recommend annual brain MRI for surveillance d. Normally the risk of haemorrhage is 2–3% per year but there is no significant increase in risk during pregnancy. Recommend review after delivery to discuss treatment options e. Normally the risk of haemorrhage is 15% per year but there is no significant increase in risk during pregnancy. Recommend review after delivery to discuss treatment options

Answer 49

49. d. Normally the risk of haemorrhage is 2–3% per year but there is no significant increase in risk during pregnancy. Recommend review after delivery to discuss treatment options Arteriovenous malformations (AVMs) are congenital lesions consisting of multiple arteries and veins, connecting as a fistula without an intervening normal capillary bed. The majority are solitary lesions except when associated with hereditary haemorrhagic telangiectasia. Approximately 90% occur in the supratentorial region (parietal > frontal > temporal). About half of AVMs present with haemorrhage (intracerebral > subarachnoid > intraventricular), approximately 25% present with focal or generalised seizures and 15% present with headache. The overall risk of haemorrhage for an unruptured AVM is about 2–3% per year. This increases to 6–17% in the first year following first haemorrhage and then decreases to a baseline level by the third year. Following a second haemorrhage, the annual risk of re-bleed rises to 25% in the following year. An approximate lifetime risk for patients with previously unruptured AVMs can be calculated as 105 minus the patient’s age in years. Current data suggests that pregnancy does not increase the risk of an AVM haemorrhage, however when possible AVMs should be treated before pregnancy. If the lesion is noted during pregnancy and there is no haemorrhage, treatment risks should be considered higher than the risk of haemorrhage, and treatment may be deferred until after pregnancy

Question 50

50. A 36 year old female presents following a tonic-clonic seizure. Over the preceding months she had suffered with progressive, severe headaches. Contrast-enhanced CT brain shows lateral displacement of the internal capsules by enlarged thalami but no abnormal enhancement. T2-weighted MRI demonstrates a diffuse, contiguous area of hyperintensity involving the thalami, caudate and lentiform nuclei, the splenium of the corpus callosum and the periventricular white matter. There is only minimal mass effect. T1-weighted gadolinium imaging shows no enhancement. What is the most likely diagnosis? a. Multiple sclerosis b. Gliomatosis cerebri c. Viral encephalitis d. Adrenoleukodystrophy e. Vasculitis

Answer 50

50. b. Gliomatosis cerebri (GC) GC is a diffusely infiltrative glioma that may be present with or without a dominant mass. It must, however, involve two or more lobes and usually involves contiguous areas. It affects all age groups and can be of varying histological grade. Presentation may be enigmatic as the normal cerebral architecture is usually preserved. Alternatively, patients present with seizures, headache and personality disorders. Prognosis is poor. MRI findings include diffuse T2 (and proton density) hyperintensity throughout the white matter that usually extends to involve the deep grey nuclei with enlargement of cerebral structures. It is often bilateral and symmetric with minor mass effect and absence of necrosis. The differential diagnosis of symmetric white matter lesions includes microvascular change, encephalitis, demyelinating disease, vasculitis and leukoencephalopathy. GC is the most likely diagnosis in this scenario as there is involvement of the corpus callosum and the pattern is infiltrative with enlargement of the thalami (cerebral structures).

Question 51

51. A neurologist requests an MRI scan of a patient with longstanding temporal lobe epilepsy. He suspects mesial temporal sclerosis. What imaging plane would you pay particular attention to and what would you expect to find in this condition? a. Axial plane demonstrating volume loss and reduced signal intensity of the parahippocampal gyrus on T2-weighted imaging b. Coronal plane demonstrating volume loss and increased signal intensity of the hippocampus on T1-weighted imaging c. Coronal plane demonstrating volume loss and increased signal intensity of the parahippocampal gyrus on T2-weighted imaging d. Axial plane demonstrating volume loss and reduced signal intensity of the hippocampus on T1-weighted imaging e. Coronal plane demonstrating volume loss and increased signal intensity of the hippocampus on T2-weighted imaging

Answer 51

51. e. Coronal plane demonstrating volume loss and increased signal intensity of the hippocampus on T2-weighted imaging Mesial temporal sclerosis (hippocampal sclerosis) is the most common lesion associated with temporal lobe epilepsy. Acquisition in the coronal plane is mandatory for its detection. MRI typically shows volume loss and increased signal on T2-weighted imaging.

Question 52

52. A male patient presents with severe back pain following surgery seven months previously. MRI shows extensive clumping of roots of the cauda equina to the right of the midline, suggesting an intrathecal mass. There is no enhancement post-gadolinium administration. What is the most likely diagnosis? a. Intrathecal metastases b. Nerve root sheath tumour c. Arachnoiditis d. Extradural haematoma e. Prolapsed intervertebral disc

Answer 52

52. c. Arachnoiditis Arachnoiditis is an intrathecal inflammatory reaction which usually results from iatrogenic injury. Previously, it was associated with the injection of contrast agents during myelography. Now, it is most commonly seen following lumbar surgery. Intradural infections (TB, fungal, parasitic) are rare causes. Radiologically, arachnoiditis appears as nerve root adhesion. Commonly the nerves are clumped together simulating a solid mass, although the nerves may also adhere to the dura, giving the appearance of an ‘empty thecal sac’. In severe cases, the thecal sac may become loculated and compartmentalised. Clumped nerve roots suggest arachnoiditis and the lack of enhancement makes tumours unlikely.

Question 53

53. You are asked to provide an opinion on skull and facial radiographs of an infant. The history provided is recent fall, known dwarfism. The radiographs show brachycephaly, widened sutures, relatively large sella, wormian bones, delayed dentition, decreased pneumatisation of the paranasal sinuses and hypertelorism. No fracture is demonstrated. What is the most likely diagnosis? a. Cleidocranial dysostosis b. Hypophosphatasia c. Hypothyroidism d. Achondroplasia e. Pyknodysostosis

Answer 53

53. c. Hypothyroidism Many of the features listed may be seen in any of the differential conditions provided. However, large sella and hypertelorism favour a diagnosis of hypothyroidism

Question 54

54. A three year old girl undergoes further investigation for refractory seizures. Contrast-enhanced T1-weighted imaging shows diffuse pial enhancement of variable thickness over the parieto-occipital region of the right cerebral hemisphere. There is atrophy of the underlying cerebrum and the right choroid plexus is enlarged. Several hypointense foci are seen within the gyri and adjacent white matter. There is also bilateral well-defined orbital choroidal enhancement. T2-weighted imaging demonstrates prominent superficial cortical veins. What is the most likely diagnosis? a. Klippel–Trenaunay syndrome b. Sturge–Weber syndrome c. Wyburn–Mason syndrome d. Neurofibromatosis e. Tuberous sclerosis

Answer 54

54. b. Sturge–Weber syndrome Sturge–Weber syndrome is a congenital disease characterised by capillary venous angiomas involving the face (port-wine stain, usually ophthalmic division of trigeminal nerve), choroid of the eye and leptomeninges. Clinical manifestations include focal seizures (80% in the first year of life), developmental delay, hemiparesis and homonymous hemianopia. Seizures typically become refractory to medication. Leptomeningeal angiomas are confined to the pia mater and occur primarily within the parieto-occipital region. There is cortical hemiatrophy beneath the angioma due to local anoxia and usually after the age of two years there is cortical calcification manifesting as low signal intensity on T1 post-contrast images. Other findings include enlargement of the ipsilateral choroid plexus, dilatation of the transparenchymal veins that communicate between the superficial and deep cerebral venous systems, and orbital choroidal haemangiomas.

Question 55

55. A 35 year old female presents with worsening headache and facial droop. Her chest radiograph is abnormal. Non-contrast-enhanced CT brain is unremarkable. MRI demonstrates leptomeningeal thickening and enhancement, particularly around the basal cisterns. Enhancement extends along the right seventh cranial nerve and along the optic nerves. There are several small superficial parenchymal enhancing lesions found bordering the basal cisterns. What is the most likely diagnosis? a. Sarcoidosis b. Tuberculosis meningitis c. Carcinomatous meningitis d. Lymphoma e. Behcet syndrome

Answer 55

55. a. Sarcoidosis Neurologic manifestations of sarcoidosis occur in 5% of patients. In over 80% of established cases, the chest radiograph is abnormal. Sarcoidosis can involve any part of the nervous system, however it has a predilection for the leptomeninges (arachnoid and pia mater). The most common sites for the disease are the basal meninges and the basal midline structures including the hypothalamus, optic chiasm and pituitary. Sarcoidosis also commonly involves the cranial nerves, which may reveal abnormal enhancement on contrast-enhanced T1-weighted imaging. The facial nerve is the most common cranial nerve involved clinically, whereas radiologically, the optic nerves are most commonly abnormal. Dural thickening/dural-based masses may also be present. Parenchymal sarcoidosis can be seen as enhancing granulomas usually located superficially in the brain parenchyma bordering the basal cisterns. Non-enhancing lesions in the periventricular white matter and brainstem are common. Hydrocephalus occurs in approximately 10% of cases.

Question 56

56. A 60 year old man presents with back pain and progressive paraparesis. T1-weighted MR imaging shows loss of T9–T10 disc space with hypointense signal involving multiple contiguous vertebral bodies. Skip involvement of T3 and L1 vertebral bodies is evident. T2-weighted imaging shows a large paraspinal and prevertebral mass. An anterior epidural collection is seen compressing the cord. On post-contrast T1-weighted imaging the vertebral bodies show inhomogeneous enhancement and the paraspinal mass shows peripheral enhancement with central necrosis. What is the most likely cause? a. Pyogenic infection b. Lymphoma c. Sarcoidosis d. Tuberculosis e. Metastases

Answer 56

56. d. Tuberculosis The vertebral column is the most common site of osseous involvement of tuberculosis (TB), usually as the result of haematogenous spread from pulmonary involvement. The lower thoracic and upper lumbar vertebrae are the most frequently affected. It can be difficult to differentiate between pyogenic and TB spondylodiscitis on imaging but several features favour a diagnosis of TB: multilevel involvement/skip lesions, relative sparing of the disc spaces, large pre/paravertebral collections which are more likely to calcify, subligamentous spread and meningeal involvement.

Question 57

57. A four month old male undergoes investigation for microcephaly and hearing loss. Unenhanced CT brain shows several periventricular subependymal cysts and multiple coarse periventricular and parenchymal white matter calcifications. There is diffuse hypoplasia of the cerebellum. What is the most likely diagnosis? a. Tuberous sclerosis b. Sturge–Weber syndrome c. Cytomegalovirus infection d. Venous sinus thrombosis e. Congenital rubella

Answer 57

57. c. Cytomegalovirus infection This is the most common intrauterine infection and the leading cause of brain disease and hearing loss in children. Typical imaging findings include periventricular subependymal cysts representing focal areas of necrosis and glial reaction, periventricular postinflammatory calcifications, scattered calcifications in basal ganglia and brain parenchyma, microcephaly due to disturbance of cell proliferation and hypoplasia of the cerebellum. There may also be lissencephaly, cortical dysplasia, polymicrogyria and schizencephaly due to disturbed neuronal migration.

Question 58

58. A 40 year old unkempt male is admitted with disorientation and ataxia. FLAIR, T2 and diffusion-weighted MR imaging reveal abnormal high signal in both medial thalami, the hypothalamus and peri-aqueductal gray matter. There is atrophy of the right mamillary body. What is the most likely diagnosis? a. Lymphoma b. Viral encephalitis c. Creutzfeldt–Jacob disease d. Wernicke’s encephalopathy e. Venous thrombosis

Answer 58

58. d. Wernicke’s encephalopathy (WE) WE refers to an acute or subacute syndrome characterised by disorientation, gaze paralysis, ataxia and nystagmus. It invariably occurs in chronic alcoholics but it is caused by thiamine deficiency. Involvement of the medial thalami is characteristic and typically the mamillary bodies, peri-aqueductal grey matter and hypothalamus are also involved. In the acute stages of the disease, haemorrhage, necrosis and oedema are encountered, whereas in the latter stages these regions tend to atrophy, particularly the mamillary bodies.

Question 59

59. A 48 year old female presents with tinnitus. CT shows a soft-tissue mass in the region of the hypotympanum. There is irregular bone demineralisation in the region of the carotid canal and jugular foramen, making their margins irregular and partially indistinct. On proton density MR imaging, the mass has mixed hyper- and hypointensity signal. The tumour shows strong enhancement after gadolinium administration. What is the most likely diagnosis? a. Glomus tympanicum tumour b. Glomus jugulare tumour c. Carotid body tumour d. Glomus vagale tumour e. Cholesteatoma

Answer 59

59. b. Glomus jugulare tumour All of the tumours listed in the differential (apart from cholesteatoma) are paragangliomas. They grow slowly and rarely metastasise. Glomus jugulare tumours originate from the adventitia of the jugular vein. CT demonstrates a soft-tissue mass in the region of the jugular bulb/hypotympanum/middle ear space. Local bone destruction is common, particularly of the jugular plate or the lateral portion of the caroticojugular spine. A unique ‘salt-and-pepper’ pattern of hyper- and hypointensity on T1- and T2-weighted images is also seen. This represents multiple small tumour vessels. They are highly vascular lesions, usually deriving a blood supply from branches of the external carotid artery.

Question 60

60. A 62 year old female presents with symptoms of amaurosis fugax. Ultrasound Doppler of her right internal carotid artery reveals a peak-systolic velocity of 2.4 m/s. What is the likely degree of stenosis? a. 0–24% b. 25–49% c. 50–69% d. >70% e. >90%

Answer 60

60. d. >70% Although variation may exist between different hospitals, a suggested relationship between peak-systolic velocity (m/s) and degree of stenosis (%) is shown below.