Ch 12 CT/MRI Brain Flashcards
What is the main reason CT imaging of the caudal fossa can be challenging?
A) Low signal from brainstem structures
B) Motion artifacts due to respiratory movement
C) Beam hardening artifacts from adjacent dense bone
D) Inability of CT to detect fluid
C) Beam hardening artifacts from adjacent dense bone
Which of the following best describes the beam hardening artifact seen on CT?
A) Increased brightness of soft tissue adjacent to bone
B) Deformation of bone margins due to overexposure
C) Incomplete image acquisition from skipped slices
D) Streaks or dark bands caused by selective absorption of low-energy X-rays
D) Streaks or dark bands caused by selective absorption of low-energy X-rays
What percentage of English bulldogs have an intact septum pellucidum?
25%
Which type iof supracollicular fluid accumulation this?
Type 1
Which type iof supracollicular fluid accumulation this?
Type 2
Which type iof supracollicular fluid accumulation this?
Type 3
Fluid accumulations within the developing brain: Focal fluid accumulations are termed _________________
whereas extensive uid accumulations are termed ________________.
porencephaly
hydranencephaly
Dandy Walker syndrome is a developmental disorder
whereby there is failure of development of the __________________.
caudoventral aspect of the cerebellar vermis
_____________________ is a developmental disorder
whereby there is failure of development of the caudoventral aspect of the cerebellar vermis
Dandy Walker syndrome
Which type of holoprosencephaly is most commonly reported in dogs?
Which other change is associated with this?
Which dog breed is overrepresented?
What is the typical presentation/biochemical change?
Lobar HPE
Corpus callosum agenesis
Mini Schnauzers and SBTs
Hypodypsic hypernatremia
What is HPE (holoprosencephaly)?
failure of the cerebral hemispheres to bifurcate
What is lissencephaly?
Failure to develop gyri, resulting in smoother outer cortical surface
Which breed is overrepresented for lissencephaly?
Lhasa Apso
Dandy Walker variant
Lissencephaly
Corpus callosum dysgenesis
Which (location and pathophys) T1w hyperintensities could occur with hepatic insufficiency?
Manganese deposition in the lentiform nuclei
In An Alaskan Husky, Bull terrier or Yorkie, what would the following findings indicate?
Bilaterally symmetrical regions of T2/FLAIR hyperintensity within the central aspect of the thalamus +/- midbrain, medulla
Subacute necrotising encephalopathy
hypernatremia; T2w hyperintense white matter between internal capsule and thalamus
Which conditions fall under the category of MUE/MUO/MUA?
granulomatous meningoencephalomyelitis (GME)
necrotizing meningoencephalomyelitis (NME)
necrotizing leucoencephalitis (NLE)
Which non-infectious meningoencephalomyelitides can be confirmed without histopath?
steroid-responsive meningitis-arteritis (SRMA)
eosinophilic meningoencephalitis (EME)
Which breed is overrepresented for idiopathic hypertrophic pachymeningitis?
Greyhound
For which type of meningitis are Greyhound overrepresented?
idiopathic hypertrophic pachymeningitis
NCL
Cerebellar abiotrophy
What % of MRI studies in dogs with inflammatory CSF are normal? (study with 25 dogs)
24%
Which regions are most commonly affected by post-ictal changes?
Piriform and temporal lobes
Post-ictal changes are… enhancing or non-enhancing?
Non-enhancing
6y DSH
seizures, ataxia and vestibular
thiamine deficiency, T2w hyperintensities in thalamus and colliculi
T1w pre-con
cat with PSS, manganese deposition in basal ganglia and lentiform nuclei
Yorki
subacute necrotising encephalopathy, thalamus and brainstem
What kind of meningiomas are common in the optic chiasm and suprasellar regions?
basal and plaque-like
Which species can get multiple meningiomas?
cats
Which extracranial (not brain parenchyma) change is typical in cats with meningiomas?
adjacent hyperostosis
Describe classic meningioma findings
Broad-based
Peripheral
Strong CE
Dural tail
Hyperostosis
PPV of dural tail for meningioma?
94%
CPTs occur most commonly in which location?
3rd ventricle, lateral recess of 4th
meningioma or lymphoma?
lymphoma
What is the most common intravrentricular tumor? What are other types?
CPT (papilloma, carcinoma)
Less common
- Ependymoma
- Meningioma
- Glioma
What are some CPT secondary effects/ complications?
Haemorrhage
CSF overproduction
In which species are pituitary tumors more common?
Dogs
(rare in cats)
How does a functional pituitary tumor usually manifest clinically?
PDH - Cushing’s
What percentage of neuro-normal PDH dogs have a pituitary mass of 4-12mm height?
60%
What is the cut-off for the term micro- and macrotumor when talking about pituitary masses?
> 10mm height is a macrotumor
Gliomas arise from the____________.
neuropil (accuracy? don’t they originate from glial cells?)
Name the types of gliomas
Oligodendroglioma
Astrocytoma
Glioblastoma multiforma
Gliomas are prevalent in which type of dog?
Brachycephalics - bulldogs, Boston, Boxer
Which type of brain tumor is diffuse and results in relative preservation of the intracranial architecture?
Gliomatosis cerebri; there may be T2w and FLAIR hyperintensity with some mass effect
Gliomatosis cerebri is classifed as a ___________ tumor of __________ (cell) origin.
Neuroepithelial
Astrocytic
Trigeminal nerve PNST dysfunction cause atrophy of which muscles?
temporal
masseter
pterygoid
digastricus
Trigeminal nerve arises from the:
pons and caudal mesencephalon
Which of the following best explains how trigeminal nerve neoplasia can lead to noninfectious middle ear effusion in dogs?
a. Direct extension of the tumor into the tympanic bulla
b. Overproduction of cerumen by the external auditory canal
c. Loss of tensor veli palatini function leading to Eustachian tube dysfunction
d. Obstruction of the external auditory canal by the tumor mass
c. Loss of tensor veli palatini function leading to Eustachian tube dysfunction
Explain how a tumor affecting the trigeminal nerve can result in sterile fluid accumulation in the middle ear.
The mandibular branch (V3) of the trigeminal nerve innervates the tensor veli palatini muscle, which is responsible for intermittently opening the Eustachian tube. This tube normally drains mucus and fluid secreted by the middle ear lining. When a trigeminal nerve tumor disrupts innervation to this muscle, the Eustachian tube fails to open properly, leading to passive fluid accumulation in the middle ear without infection
__________________ is an uncommon extra-axial
tumor that has imaging characteristics similar to meningioma,
including a dural tail.
Histiocytic sarcoma
Histiocytic sarcoma is an ________-axial
tumor
extra or intra
Which tumors are associated with a dural tail?
meningioma, also histiocytic
In which tumors is meningeal enhancement remote from the tu-
mor epicenter not an uncommon finding?
Histiocytic sarcoma
Which is the most common metastatic lesion in the brain?
hemangiosarcoma
Brain tumors do not
commonly extend rostrally through the cribriform plate into
the nasal cavity. A rare neural tumor that does traverse the
cribriform plate is an ______________.
olfactory neuroblastoma
Infarcts occur most commonly in the _____________ (which part of the brain)
cerebellum
Which of the following is most characteristic of an acute cerebral infarct compared to a glioma?
a. Avid contrast enhancement
b. Prominent mass effect within hours of onset
c. Initial absence of mass effect
d. Heterogeneous T1 hyperintensity
c. Initial absence of mass effect
Explanation: In acute infarction, mass effect is usually absent early but may develop over 3–5 days due to vasogenic edema. Gliomas often have mass effect from the outset due to tumor volume and edema.
there is usually ill-defined T2 hyperintensity, T1 hypointensity, no mass effect, and little to no initial contrast enhancement
Diffusion-weighted MRI helps differentiate infarcts from tumors by assessing which of the following?
a. Electrical conductivity of axons
b. Water molecule temperature
c. Directionality of cerebrospinal fluid flow
d. Brownian motion of water molecules in tissue
Correct Answer: ✅ d. Brownian motion of water molecules in tissue
Explanation: DWI quantifies the random motion (Brownian motion) of water molecules. Restricted diffusion (e.g., in cytotoxic edema from infarct) appears bright on DWI and dark on ADC.
When Might Mass Effect Develop in an Infarct? In a cerebral occlusive / ischemic infarct, mass effect due to vasogenic edema typically develops:
a. Within 1–2 hours
b. After 12 hours
c. Between 3 to 5 days
d. Only if hemorrhage occurs
c. Between 3 to 5 days
Explanation: Vasogenic edema develops in the subacute phase, usually peaking between days 3–5 post-infarct.
Approx. age of this haemorrhage - T1w pre and post
at least 3 days, less than 14 days (when methemoglobin turns into hemosiderin)
fracture with epi/sub-dural haemorrhage
In which haemorrhage phase is it T2w hyperintense?
Hyperacute <24h
Late subacute 7-14days
Age this haemorrhage (T2 and GRE)
either hyperacute (<24h) or late subacute (7-14days)
T2, ADC, T1w pre and post
R caudate nucleus, ischemic event
How and when can you use DWI to differentiate a tumor from an ischemic infarct? What else can you use?
A tumor will have more facilitated diffusion, while an infarct while have restricted (at first, up to 3-5 days).
A tumor will also usually have mass effect, which is absent in an infarct (for the first 3-5 days) until it d.
Most common underlying causes of haemorrhagic infarcts
hypertension
coagulopathy e.g. thrombocytopenia
Differences in MRI appearance between ischemic and haemorrhagic infarct
Hemorrhagic - more heterogenous, larger volume
Low signal in T2-weighted spin-echo and GRE images is not specific
for hemorrhage and may also be seen with _________________.
mineralization
gas
fibrous tissue
iron deposits
Acute hemorrhage is _________________ (hyper/hypo) to brain tissue in precontrast CT imaging due to the ______________. The average HU of hemorrhage is between __________, whereas those of
gray and white matter are ________________ and _______________,
respectively.
hyperattenuating, high hemoglobin content.
Haemorrhage: 60 and 100
grey: 30 to 40
white: 20 to 30
