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THRALL - Thom > 12. MRI Brain > Flashcards

12. MRI Brain Flashcards

1
Q

How does Gadolinium work?

A

Shortens T1 relaxation time of effected tissues -> Hyperintense

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2
Q

What specific adverse reaction / disease is associated with Gad administration?

A

Nephrogenic Systemic Fibrosis

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3
Q

What are general features of Proton Density weighted images?

A
  • Intermediate between T1 and T2
  • Good for anatomic detail, particulalry grey / white matter
  • Acquired during T2 dual echo sequence
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4
Q

What is Gradient Echo useful for?

A
  • Identification of inhomogeneities in the field

=> CHRONIC haemorrhage (2-3 days) - presence of ferrous / ferric ions

  • Susceptibility artefact -> extremely sensitive indicator of haemorrhage

=> Void typically larger due to BLOOMING

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5
Q

What is the most common intracranial developmental anomaly?

A

Hydrocephalus

=> Congenital form most common

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6
Q

List three mechanisms by which hydrocephalus may develop

A
  • Obstruction to outflow
  • Increased CSF production / decreased absorption
  • Brain atrophy
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7
Q

Agenesis of the septum pellucidum is seen in which breeds most frequently? How freq is it considered intact in dogs?

A
  • Large brachycephalics
  • 25% of dogs have intact
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8
Q

Describe the three patterns of supracollicular fluid accumulation. What does the membrane represent?

A

1) Enlargement of caudodorsal recess of third ventricle -> Displacement of membrane caudodorsally
2) FLuid in caudodorsal recess and quadrigeminal cistern -> Membrane visible seperating them
3) Quadrigeminal fluid only -> Membrane displaced rostrally.

MEMBRANE = Likely Third ventricular wall. Where pia mater joins ependymal layer forming the tela choroidea of 3rd ventricle

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9
Q

Define differenes between hydrancephaly and porencephaly? List 3 causes of porencephaly

A

Hydrancephaly = extensive fluid accumulations within developing brain

Porencephaly = focal fluid accumulations

“Encephaloclastic porencephaly” broad term -> loss from e.g. ischaemia, infection, trauma

=> Usually involve lateral ventricles OR subarachnoid space

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10
Q

What is Dandy Walker syndrome?

A
  • Absence of caudoventral aspect of cerebellum -> occurs to varying degress, with resultant effect on CS
  • Number of manifestations -> “Dandy Walker variant” should be used
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11
Q

What is holoprosencephaly? Name three types. What associated malformation is described? What associated clinical signs / breed for this anomaly?

A

Holoprosencephaly: Failure of normal bifurcation of cerebral hemispheres

1) ALOBAR
2) SEMILOBAR
3) LOBAR (described in dogs)

* Associated corpus callosal agenesis/dysgenesis -> Mini schnauzers

Hypodipsic hypernatraemia

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12
Q

List 4 uncommon intracranial cystic lesions due to defects of neural tube closure

A
  • Dermoid cyst
  • Epidermoid cyst
  • Rathkes cleft cyst
  • Craniopharyngioma
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13
Q

Where are epidermoid / dermoid cysts most commonly located (x2)? MRI features?

A
  • 4th ventricle
  • Cerebellopontine angle

MR: If lipid - T1w hyper and T2w hyper; may contain hair (dermoid) hypo foci; usually do not enhance, althoigh can enhance peripherally. Do not FLAIR null if lipid

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14
Q

Where are Rathkes cleft cysts / craniopharyngiomas identified?

A

Sella turcica -> Pituitary anomalous development

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15
Q

Classic features of Caudal Occipital Malformation syndrome

A
  • Crowding of caudal fossa
  • Herniation of cerebellar vermis
  • CKCS overrepresented (up to 95% breed demonstrate this)
  • 2ry syringohydromyelia
  • Some association between syndrome and formation of dorsal Atlanto-axial bands
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16
Q

What is lissencephaly? Which breed is over-represented?

A

Lack / absence of normal gyral formation

LHASA APSO

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17
Q

List 4 “common” storage diseases (Inborn errors of brain metabolism)

A
  • Mucopolysaccharoidosis
  • Neuronal cell Lipofuscinosis
  • Cerebellar abiotrophy
  • Globoid cell leuckodystrophy
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18
Q

Describe features of mucopolysaccharoidosis / lipofuscinosis

A

BOTH:

  • Progressive juvenile cerebral atrophy -> hydrocephalus
  • Small Corpus callosum

**LIPOFUSCINOSIS -> often SEVERE peripheral meningeal thickening and enhancement**

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19
Q

Describe features of cerebellar abiotrophy

A
  • Progressive cerebellar atrophy -> Increased conspicuity of cerebellar folia
20
Q

Describe features of Globoid cell leukodystrophy

A
  • Symmetrical, white matter disease
  • Mild hydrocephalus
  • Symmetrical contrast enhancement of CC, internal capsule and corona radiata
21
Q

List a common NUTRITIONAL brain disorder, and associated features

A

THIAMINE DEFICIENCY

  • Bilaterally symmetric, multifocal
  • Nuclei of brain and brainstem:

LATERAL GENICULATE, CAUDAL COLLICULI, VESTIBULAR NUCLEI and others

22
Q

What intracranail change may be seen with PSS? What other conditions have been associated with these changes?

A
  • T1 hyperintensity of lentiform nuclei (manganese deposition)
  • IN PEOPLE ALSO: Hepatic insufficiency, parenteral nutrition
23
Q

Describe features of subacute necrotizing encephalopathy

A
  • ALASKAN HUSKY, Yorkie, Bull terrier
  • Ultimately fatal neurodegen disorder
  • Bilaterally symmeterical T2/FLAIR hyper centrally within Thalamus. May extend to colostrum / putamen

May also have focal T2w hyper in midbrain and medulla

24
Q

What MR features may be seen with hyperNa (not associated with holoencephaly / CC anomalies)?

A
  • Bilaterally symmetrical increase in T2 at junction of internal capsule and lateral margin of thalamus
25
Q

Which breeds are effected by necrotizing encephalitis? What features are seen?

A

YORKIES, PUGS

  • Usual inflam….

Patchy T2/FLAIR hyper, variable CE, no. mass effect

If chronic -> parenchymal atrophy and “compensatroy hydrocephalus”

26
Q

Breeds / features of GME

A

Young and middle aged small breeds.

Normal inflam….

Patchy T2w/FLAIR hyper +- patchy CE

27
Q

Features / spp associated with parasitic encephalitis?

A
  • Serpentine or linear distribution

+ appropriate hx!

NE US: Cuterebra larvae -> association with Feline ischaemic encephalopathy (transnasal aberran migration )

=> Parenchymal and middle cerebral artery injury

28
Q

What % of patients have normal MR with inflammatory brain disease?

A

24%

29
Q

What are the typical features of post ictal changes?

A
  • Temporal and piriform lobes (may effect elsewhere inc cingulate gyrus)
  • T2/FLAIR hyper, no CE or mass effect
  • USUALLY bilateral, can be unilateral
30
Q

Greyhound meningeal disease??

A

Idiopathic hypertrophic pachymeningitis

  • Thickening of pachymeninges (Dura
  • without extension into sulci), without specific cause
31
Q

Features of meningioma

A
  • Associated with dural elements
  • Extraaxial, broad based, single / multiple (more in cats)
  • SHAPE: … CAN BE PLAQUE LIKE, more common in floor of cranial cavity
  • Less common locations: Cerebellpontine angle, retrobulbar
  • May be mineralised, cystic
  • MR: CE, dural tail

IMPORTANT DDx = ROUND CELL (lymphoma or histiocytic sarcoma)

32
Q

What is the predictive value of dural tail for meningioma?

A

94%

33
Q

Features of choroid plexus tumours? Location? Behaviour? DDx

A
  • Intraventricular: Most commonly 3rd ventricle or lateral recess of 4th.
  • Mineralisation or haemorrhage common -> Drop metastasis with benign / malig variants
  • May overproduce CSF
  • MR: Intraventricular location, marked CE, secondary obstructive hydrocephalus

DDx: Ependymomas -> SIMILAR APPEARANCE, but rarer

34
Q

Features of canine pituitary tumours?

A
  • Functional or nonfunctional
  • Up to 60% of dogs with PDH but without neuro signs have tumour between 4-12mm (vertical)
  • MR: Well defined, uniform CE++, minimal peritumoural oedema, cystic regions / haemorrhage
35
Q

How are canine pituitary tumours characterised by size ?

A

Microtumour = 3-10mm

Macrotumour = >10mm

<3mm, may not be detected on MR

36
Q

MR features of Glioblastoma cerebri?

A
  • Mimics more common conditions
  • MR: Diffuse T2 and FLAIR signal throughout cerebrum. Some mass effect, but overall relative preservation of neural morphology. Minimal CE.
37
Q

Features of glioma?

A
  • Tumours arising from Neuropil: Astrocytomas, oligodendrocytomas, and glioblastoma multiforme
  • Brachys: Boxers, Bostons, Bulldogs
  • MR: lll defined, variable perilesional oedema, variable CE
  • > Difficult to differentiate from abscess, inflamm, or large infarct
38
Q

Name three types of peripheral nerve sheath tumour

A
  • Schwannoma
  • Neurilemmoma
  • Neurofibroma

=> NERVE SHEATH IS OVERARCHING TERM -> BEST USED THOUGH as cannot distinguish

39
Q

Where does the trigeminal nerve arise?

A
  • Pons and caudal aspect of mesencephalon
40
Q

MR features of nerve TRIGEMINAL nerve sheath tumours?

A
  • Muscle atrophy: Muscles of mastication -> masseter, temporalis, medial pterygoid, ROSTRAL portion of digatricus (NB: caudal portion innervated by facial)
  • Foraminal enlargement
  • T2 iso or hyper and +++CE
  • Middle ear effusion - TENSOR veli palatini

=> Fat suppression may make more conspicuous

41
Q

List three LESS COMMON brain tumours (e.g not gliomas). Which is most common metastatic tumour?

A
  • Histiocytic: Like meningioma, may have dural tail. Can be intraxial.
  • Lymphoma: Extra or intraaxial, variably appearance, CE
  • HSA: MOST COMMON MET
42
Q

MR features of idiopathic peripheral vestibular disease?

A

NORMAL!!!!!

43
Q

MR features of ischaemic infarction?

A
  • T2/FLAIR hyper
  • Triangular / territorial shape
  • INITIAL LACK OF MASS EFFECT (may develop with oedema after 3-5 days)
  • Restricted diffusion (LOW ADC, HIGH DWI SIGNAL) in initial 3-5 days

***HYPERCOAGULABLE STATE e.g. cushings, loss of antrithrombin 3

44
Q

What does DWI / ADC demonstrate? Describe pathophys in infarction vs neoplasia

A
  • Restricted BROWNIAN MOTION - water molecules normally move randomly and constantly -> Rate of diffusion depends on kinetic energy and temp
  • Infarction: Cells overhydrated due to failure of ATP pump -> restricted motion
  • Neoplasia: Movement less restricted
45
Q

MR features of haemorrhagic infarction

(seperate question with mnemonic / table)

A
  • Similar to ischaemic -> but varies as haematoma matures
  • Associated with: Hypertension, thrombocytopaenia or other coagulopathies
46
Q

List 5 DDx for T2* signal void

A

Haemorrhage

Mineralisation

Gas

Fibrous tissue

Iron deposits

47
Q

Mnemonic for haemorrahge and table!! LEARN THIS!!

A

I Bleed, I Die, Bleed Die, Bleed Bleed, Die Die

(Hyperacute) I Bleed: T1 = Iso, T2 Bright

(Acute) I Die: T1 = Iso, T2 Dark

(Early Subacute) Bleed, Die: T1 = Bright; T2 = Dark

(Late Subacute) Bleed, Bleed: T1 = Bright, T2 = Bright

(Chronic) Die, Die: T1 = Dark, T2 = Dark

THRALL - Thom (40 decks)

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