Magnetic resonance imaging diagnosis of brain tumors in dogs

Question 1

Differential diagnosis for masses associated with the pituitary gland or nearby optic chiasm.

Answer 1

• Pituitary adenoma or adenocarcinoma
• Germ cell tumor
• Craniopharyngioma
• Ependymoma
• Meningioma, lymphoma, granular cell tumor…

Question 2

T/F. Contrast-enhancement of extra-axial tumors is almost universal.
(Bentley 2015)

Answer 2

True (bc pachymeninges are outside of the BBB).

Question 3

A dural tail is a linear enhancement of (thickened / thin) dura mater adjacent to an (extra / intra) axial mass on (T1 / T2W) post-contrast images.
(Bentley 2015)

Answer 3

A dural tail is a linear enhancement of THICKENED dura mater adjacent to an EXTRA-AXIAL mass on T1W POST-contrast images.

Question 4

T/F. The dural tail sign occurs in brain tumors only.

Answer 4

False. It has occurred in fungal and protozoal granulomas too.

Question 5

T/F. Broad-based dural contact and the dural tail sign may confirm that a lesion is extra-axial.
(Bentley 2015)

Answer 5

True, but do not allow a definitive diagnosis.

Question 6

T/F. Meningiomas do not typically cause mass effect.

Answer 6

False, they do.

Question 7

What is the second most common solitary meningeal-based contrast-enhancing mass lesion?
(Bentley 2015)

Answer 7

Histiocytic sarcoma.

Question 8

T/F. The absence of extra-neural disease does not rule out histiocytic sarcoma.
(Bentley 2015)

Answer 8

True.

Question 9

Can meningiomas be cystic or polycystic?
(Bentley 2015)

Answer 9

Yes, around one-quarter of them are, in contrast with histiocytic sarcoma.

Question 10

Name 3 non-neoplastic extra-axial cystic lesions.
(Bentley 2015)

Answer 10

Arachnoid diverticula, epidermoid cyst, ependymal cyst.

Question 11

T/F. Fungal lesions frequently have sharply defined borders.
(Bentley 2015)

Answer 11

False. They frequently have indistinct or poorly defined borders.

Question 12

T/F. 90% of meningiomas have sharply defined borders.
(Bentley 2015)

Answer 12

True. Smooth or irregular, but sharply defined.

Question 13

T/F. Around 3/4 of meningiomas are infratentorial, especially front-olfactory.
(Bentley 2015)

Answer 13

False! Supratentorial!

Question 14

T/F. Granular cell tumors are usually plaque-like meningeal growths.
(Bentley 2015)

Answer 14

True! They are also T1-hyperintense.

Question 15

Meningiomas are usually T1-_______ and T2-_______.
(Bentley 2015).

Answer 15

T1-iso or HYPOintense, and T2-iso or HYPERintense.

Question 16

If the lesion is T2-hypointense, what should we include in the list of ddx?

(Bentley 2015)

Answer 16

Benign hematoma or hemorrhage.

Question 17

Can granulomas be a differential diagnosis for a solitary contrast-enhancing meningeal mass?
(Bentley 2015)

Answer 17

Yes!

Question 18

What is the most important differential diagnosis for solitary enhancing intra-axial lesion?
(Bentley 2015)

Answer 18

Glioma.

Question 19

Where are choroid plexus tumors more common?
(Bentley 2015)

Answer 19

In the fourth ventricle.

Question 20

What are the 2 types of choroid plexus tumors?
(Bentley 2015)

Answer 20

Papillomas and carcinomas.

Question 21

Which one of the 2 types of choroid plexus tumors can display ‘drop metastasis’?
(Bentley 2015)

Answer 21

Carcinomas. They can even cause meningeal carcinomatosis.

Question 22

T/F. As CPTs are more abundant, any mass replacing the normal choroid plexus is more likely to be a CPT than ependymoma.
(Bentley 2015)

Answer 22

True, especially if sited in the fourth ventricle.

Question 23

T/F. If a normal choroid plexus can be identified as a small contrast enhancing area on T1W images, separate from a solitary ventricular mass, that mass is probably a CPT.
(Bentley 2015)

Answer 23

False, is NOT a CPT. Ependymoma most likely.

Question 24

T/F. Ependymomas are derived from the ependymal cell lining of the ventricle system and spinal cord central canal, and are common in domestic animals.
(Atalay Vural 2006)

Answer 24

False. They are rare.

Question 25

CPTs are T1-______ much more often than other brain tumors. (Bentley 2015)

Answer 25

Hyperintense. Can also be iso or hypointense.

Question 26

CPTs are typically T2-_________ with/without peri-humoral edema. (Bentley 2015)

Answer 26

HYPERintense, WITH edema (non-specific features).

Question 27

Meningiomas are rarely or infrequently T1-________. (Bentley 2015)

Answer 27

HYPERintense, contrary to CPTs.

Question 28

Name 2 non-neoplastic differential diagnoses for a solitary ventricular mass. (Bentley 2015)

Answer 28

1. Choroid plexus cyst 2. Cholesterol granuloma 3. Epidermoid cyst

Question 29

Is it common to see mass effect associated with gliomas? (Bentley 2015)

Answer 29

Yes, it's seen in over 90% of astrocytomas and oligodendrogliomas.

Question 30

T/F. Astrocytomas usually distort ventricles. (Bentley 2015)

Answer 30

False. Oligodendrogliomas do.

Question 31

T/F. Lymphoma and GC may infiltrate without mass effect. (Bentley 2015)

Answer 31

True.

Question 32

Strong/weak contrast-enhancement significantly predicts neoplasia over inflammatory and vascular. (Bentley 2015)

Answer 32

STRONG.

Question 33

T/F. Gliomas are generally T1-HYPOintense and T2-HYPERintense. (Bentley 2015)

Answer 33

True. Frequently heterogeneous in T2.

Question 34

The causes of T1-hyperintensity within tumors are narrow, and include m_______ and h______. (Bentley 2015)

Answer 34

Melanoma and hemorrhage.

Question 35

T/F. Hemorrhage or T2W gradient echo (GRE) signal voids occur in 70-80% of gliomas. (Bentley 2015)

Answer 35

False. 30-40%.

Question 36

Name 3 other lesions with hemorrhage or GRE signal voids. (Bentley 2015)

Answer 36

- Hemangiosarcoma. - Hemorrhagic CVA. - Melanoma. Others: hemangioma, hamartoma, cerebellar medulloblastoma.

Question 37

Peri-lesional edema is more common in glioma or in CVA? (Bentley 2015)

Answer 37

Glioma.

Question 38

Where are oligodendrogliomas usually located? (Bentley 2015)

Answer 38

Prosencephalon.

Question 39

T/F. The majority of caudal fossa gliomas are astrocytic. (Bentley 2015)

Answer 39

True.

Question 40

Within gliomas, surface contact and ventricular distortion are more common for ... (Bentley 2015)

Answer 40

Oligodendroglioma.

Question 41

Name 4 tumors that can metastasize as solitary enhancing intra-axial lesions. (Bentley 2015)

Answer 41

- Hemangiosarcoma - Round cell tumor - Carcinoma - Melanoma

Question 42

What are the 3 most common neoplastic ddx for a solitary meningeal-based mass? (Bentley 2015)

Answer 42

Meningioma Histiocytic sarcoma Choroid plexus tumor

Question 43

What are the 3 most common neoplastic ddx for solitary ventricular mass? (Bentley 2015)

Answer 43

Choroid plexus tumor Ependymoma Meningioma

Question 44

What are the 3 most common neoplastic ddx for solitary enhancing intra-axial lesions? (Bentley 2015)

Answer 44

Glioma, metastasis, primary CNS lymphoma

Question 45

T/F. All the solitary enhancing intra-axial lesions can appear non-enhancing, the difference is the order in the ddx list. (Bentley 2015)

Answer 45

True! Low-grade glioma, cerebellar meduloblastoma, and gliomatosis cerebri are going to be more likely.

Question 46

T/F. Minimal contrast-enhancement is characteristic of glioma. (Bentley 2015)

Answer 46

False! Gliomatosis cerebri.

Question 47

T/F. Ischemic strokes are a major differential diagnosis for non-enhancing lesions. (Bentley 2015)

Answer 47

True. Strong enhancement occurs in only 5% of vascular lesions.

Question 48

T/F. Contrast-enhancement rules out hemorrhagic cerebrovascular accident. (Bentley 2015)

Answer 48

False. It is possible during peripheral revascularization.

Question 49

The 2 MRI sequences critical in distinguishing neoplasms from infarcts are d_____ w_____ i_____ and a_____ d____ c____ maps. (Bentley 2015)

Answer 49

Diffusion weighted imaging (DWI) Apparent diffusion coefficient maps.

Question 50

Hyperintensity on apparent diffusion coefficient is significantly more common for glioma/infarcts. (Bentley 2015)

Answer 50

Glioma, as is mass effect.

Question 51

W____-shaped lesions predict cerebrovascular accidents. (Bentley 2015)

Answer 51

Wedge-shaped.

Question 52

T/F. Inflammatory lesions including GME and distemper are always enhancing. (Bentley 2015)

Answer 52

False, they can be non-enhancing.

Question 53

What are the 3 most common neoplastic ddx for a solitary non-enhancing intra-axial lesion? (Bentley 2015)

Answer 53

Low-grade glioma, gliomatosis cerebri, cerebellar medulloblastoma.

Question 54

What are the 4 most common neoplastic ddx for multifocal lesions (intra and extra)? (Bentley 2015)

Answer 54

Lymphoma, metastasis, gliomatosis cerebri, and choroid plexus carcinoma.

Question 55

Although lymphoma can produce any of the 5 patterns considered, which 2 are not typical? (Bentley 2015)

Answer 55

Non-enhancing lesions and ventricular involvement.

Question 56

Lymphoma has no characteristic MRI appearance, but the most repeatable characteristic is _________ _________. (Bentley 2015)

Answer 56

Contrast enhancement.

Question 57

T/F. MRI might be within normal limits with lymphoma, gliomatosis cerebri, or multifocal oligodendroglioma. (Bentley 2015)

Answer 57

True.

Question 58

T/F. Lymphoma and glioma are archetypal examples of diffuse infiltration of neoplastic cells with negligible mass effect. (Bentley 2015)

Answer 58

False. Lymphoma and gliomatosis cerebri.

Question 59

T/F. Diffuse multifocal meningeal enhancement, with or without other lesions, can increase the suspicion of round cell tumors and inflammatory disease. (Bentley 2015)

Answer 59

True.

Question 60

Name some non-neoplastic causes for multifocal lesions. (Bentley 2015)

Answer 60

Inflammatory (GME, NLE, NME) Infectious (fungal, neosporosis, viral, tick-borne) Thiamine deficiency

Question 61

Post-ictal changes may overlap in appearance with infiltrating neoplasia, occurring uni or bilaterally in the __________ lobe and elsewhere. (Bentley 2015)

Answer 61

Pyriform-temporal lobe.