Spinal Cord

Question 1

How are spinal tumors classified?

Answer 1

1. Extradural
   
   1. Fat suppresion is helpful both in pre- and post-contrast T1Wi
   2. Most lesions affecting the vertebral bone marrow then to have low signal on T1Wi
2. Intradural-extramedullary
   
   1. Golf-tee sign: focal dilation of the subarachonoic space along the caudal and cranial margins of the intradular mass, best seen on T2Wi
   2. Dural tail sign: focal thickening/infiltration of the minienges adjacent to a meningeal mass (e.g. meningioma)
   3. Tend to enhnce significantly on post-conrtast
   4. Fat saturation may be useful to determina the extent
3. Intramedullary
   
   1. Focal swelling of the spinal cord
   2. Circumferential attenuation of the bright CF signal +/- epidural fat on T2Wi

Question 2

In dogs, what category of spinal neoplasia is most common?

Answer 2

Extradural followed by intradural-extramedullary

Question 3

Spinal Cord Neoplasia (dogs)

• Extra-dural spinal cord tumors

.

Answer 3

1. Peripheral Nerve Sheath Tumors
2. Osteosarcoma
3. Synoval myxoma/myxosarcoma
4. Plasma cell tumor
5. Lymphoma
6. Metastatic neoplasia (in particular from porstatic carcinoma or TCC)
7. Solitary or disseminated hystiocytic sarcoma

Question 4

Spinal Cord Neoplasia (dogs)

• Intradural-extramedullary spinal cord tumors

Answer 4

1. Nerve Sheath Tumots
2. Meningioma
3. Nephroblastoma

Question 5

Spinal Cord Neoplasia (dogs)

• Intramedullary spinal cord tumors

Answer 5

1. Ependyoma
2. Metastatic neoplasia (in partiacular TCC and hemangiosarcoma)

Less common:

1. Asrtocytoma
2. Nephroblastoma
3. Chondroma
4. Oligodendroglioma

Question 6

In cats what is the most common neoplasia and where is it usually located?

Answer 6

• Lymphoma
• Extradural and mixed extradural-ontramedullary are the most common location

Question 7

Spinal Cord Neopalsia (cats)

• Extra-dural

Answer 7

1. Lymphoma - most common spinal neoplasia overall
2. Osteosarcoma - 2nd most common spinal neolasia in cats overall
3. Fibrosarcoma
4. Undifferentiated sarcoma
5. Plasma cell tumors

Question 8

Spinal Cord Neopalsia (cats)

• Intra-dural

Answer 8

1. Meningioma
2. Histiocytic neoplasia

Question 9

Spinal Cord Neopalsia (cats)

• Intra-medullary

Answer 9

1. Glial cell
2. Primitive neuroendocrine tumors

Question 10

Are metastatic spinal cord tumors in dogs or cats?

Answer 10

Metastatic vertebral tumors are common in dogs while they are uncommon in cats.

Question 11

What are some benign spinal cord tumors?

Question 12

What are imaging characterits of chondrosarcomas on MRI?

Answer 12

The MRI appearance of specific vertebral tumors has been rarely reported. For example, chondrosarcoma tends to form:

• lobulated masses
• often in the dorsal vertebral compartment
• markedly T2 hyperintense with few foci of hypointensity
• iso to hypointense on T1W images with mild to marked peripheral or heterogeneous contrast enhancement

Question 13

What are Osteochondromas?

Answer 13

• Osteochondroma is a cartilage-capped exostosis with a cortex and medulla that blend smoothly with those of the parent bone.
• The lesion generally arises prior to skeletal maturity from the metaphyseal or juxta-epiphyseal regions of the axial and appendicular skeleton.
• Although they can be clinically silent, signs associated with spinal osteochondromas may include pain and neurologic deficits as a result of spinal cord compression and impingement of adjacent nerves.

Question 14

What are locations of osteochondromas?

Answer 14

• long bones
• ribs
• vertebrae

Question 15

Osteochorndromas can undergo malignant transformation into what kind of tumor?

Answer 15

Malignant transformation into osteosarcoma and chondrosarcoma is described with both isolated osteochondroma and multiple cartilaginous exostoses.

Question 16

What are MRI features of vertebral osteochondrfomas?

Answer 16

• A well-defined mass arising from the surface of the affected vertebra and of similar signal intensity to the adjacent normal bone.
• Presence of a thin cartilaginous cap recognized as:
  
  • a curvilinear T2 hyperintense, T1 iso- to hypointense structure conforming to the surface of the mass.
• Variable degrees of spinal cord compression or foraminal impingement
• There can be variable degrees of mineralization of the cap as the lesion matures, which can also alter the MRI signal intensity (T2W hypointense).

Question 17

In humans what risk factor has been identified to predict malignant transformation for vertebral osteochondromas?

Answer 17

In people, it was shown that increased thickness of the cartilaginous cap might be associated with malignant transformation, although this has not been demonstrated with dogs and cats.

Question 18

What are chondromas and what locations are common?

Answer 18

• Chondromas are rare benign tumors characterized by the formation of mature cartilage, more common in flat bones and ribs.
• In the spine, they may originate from the vertebral body, lamina, pedicles, or transverse or spinous processes, or could evolve from hyperplastic immature spinal cartilage or from metaplastic connective tissue in contact with the spine

Question 19

What are MRI features of synovial myxoma/myxosarcoma?

Answer 19

• A lobulated mass
• Associated with an articular process joint
• Causing distortion/lysis of the adjacent articular processes and possibly widening of the joint space
• The mass typically invades into the adjacent muscles (extends along the fascial planes) and into the vertebral canal, causing variable degrees of spinal cord compression
• Markedly hyperintense on T2W images, with signal intensity similar to that of the CSF
• On T1W images the mass is hypointense and there is moderate to strong enhancement on post-contrast images, which can be diffuse, patchy, or rim-like
• Central non-enhancing areas are common, corresponding to pockets of mucinous substance

Question 20

What are MRI features of infitrative lipomas?

Answer 20

• Hyperintense on T1W and T2W (turbo or fast spin echo) images with a signal intensity similar to that of normal subcutaneous fat.
• Fat-suppression techniques are useful
• A key feature is the local invasiveness into adjacent muscles and, depending on the case, into the vertebral canal, either through the intervertebral foramina and/or through direct invasion of the vertebrae
• Areas of bony lysis/invasion are typically well marginated
• There is typically no contrast enhancement, although mild enhancement of the muscles infiltrated by the mass may be present, presumably due to associated myositis

Question 21

What are myelolipomas?

What are common locations of them?

Answer 21

• Myelolipoma is a benign tumor consisting of mature fat interspersed with myeloid and erythroid elements, resembling bone marrow tissue. These lesions are typically asymptomatic; however, large tumors may cause clinical signs as a result of the mass effect. When developing adjacent to the spinal cord, they can cause neurologic deficits and pain.
• They are reported in dogs and cats in the:
  
  • spleen
  • adrenal glands
  • liver

Their etiology and classification into the neoplasia group are controversial, and some consider them as being ectopic proliferations, hamartomas, or choristomas

Question 22

What signalment is and location common for epidural myelolipomas?

Answer 22

There are a few reports of myelolipomas in the dog in an epidural location, causing spinal cord compression resulting in proprioceptive ataxia and spinal hyperesthesia.

All the dogs were:

• older male
• sled dogs (a Siberian Husky, an Alaskan Malamute, and a Husky-cross)

And all the lesions were in the:

• thoracolumbar junction area

Question 23

What are MRI features of epidural myelolipomas?

Answer 23

• Relatively well-marginated lesion in the epidural space, causing spinal cord compression
• Mixed signal intensity with a bulk of T1 hyperintense and T2 hyperintense tissue compared with the spinal cord, interspersed with more hypointense areas, conferring overall a heterogeneous appearance
• On fat suppression pulse sequences, suppression of the hyperintense signal is consistent with fatty components within the mass
• No contrast enhancement

Question 24

What are peripheral primitive neuroectodermal tumors?

Answer 24

Primitive neuroectodermal tumors are rare embryonal undifferentiated tumors of neural crest origin, which in dogs and cats:

• Most commonly develop in the central nervous system (CNS), in particular the cerebellum where they are referred to as ‘medulloblastomas’, which is mostly seen in young dogs and calves
• The ‘peripheral’ form of the disease develops outside of the CNS; other terminology found in the literature includes ‘neuroblastoma’. It is derived from germinal neuroepithelial cells of the neural crest that are known to differentiate into autonomic ganglia, dorsal root gan- glia, adrenal medulla, skin melanoblasts, and parts of the peripheral nervous system.

Question 25

What are the two chategoties (based on location) of peripheral primitive neuroectodermal tumors?

Answer 25

* **CNS:** * **Medulloblastoma -** cerebellum * **Peripheral** forms: * **Neuroblastoma** - these tumors can develop in various locations: * bone marrow * subcutaneous tissue with visceral metastases * cranial nerves * paraspinal location (adrenl medulla, autonomic ganglia, peripheral nerves) can cause spinal cord compression

Question 26

What are **neuroendocrine tissues**? Given examples of neuroendocrine tumors.

Answer 26

Neuroendocrine tissues are tissues that have **both nervous system and hormone-producing** functions. These cells are located throughout various tissues throughout the body. Pancreas: * Insulinoma * Gastrinoma * Glucanomas Adrenal gland: * Pheochromocytoma - arise in the medulla of the adrenla gland Chemoreceptor cells - detect very small changes in the carbon dioxide and oxygen content and pH of the blood, and they help regulate breathing and circulation. * Carotid body - neck * Aortic body - heart base Thyroid * C-Cell Tumors (uncommon)

Question 27

What are paraganglionic cells?

Answer 27

A paraganglion (pl. paraganglia) is a group of **non-neuronal cells** derived of the **neural crest**. They are named for being generally in **close proximity to sympathetic ganglia**. They are essentially of two types: 1. **Chromaffin** or **sympathetic** paraganglia made of chromaffin cells * Pheochromocytomas 1. **Non-chromaffin** or **parasympathetic** ganglia made of glomus cells * Paraganglioma The paraganglionic system is made up of the: * Adrenal medulla * Chemoreceptors * Vagal body * Small groups of cells associated with the thoracic, intra-abdominal, and retroperitoneal ganglia Tumors of the paraganglionic tissues are known as **paragangliomas**, though this term tends to imply the **nonchromaffin** type, and can occur at a number of sites throughout the body. **Chromaffin paragangliomas** are issued from chromaffin cells, and are **known as pheochromocytomas.**

Question 28

Give some examples of **paragangliomas**?

Answer 28

* **Pheochromocytomas** - arise from *chromafifn* cells of the *sympathetic* nervous system * Adrenal gland * Extra-adrenal * **Chemodectomas** - arise from *non-chromoffin* type of cells of the *parasympathetic* nervous system that are located in various parts of the body * Aortic chemoreceptors - heart base * Carotid chemoreceptors - neck

Question 29

What are some imaging characteristics of **parangangliomas** that develop from paraganglion in the **mediastinum** or **retroperitoneal** space?

Answer 29

MRI apperance have not been reported: * May be locally invasive * May extend into the vertebral canal * Causing spinal cord compression CT changes in a dog with invasive mediastinal paraganglioma causing: * Vertebral lysis * Vertebral canal invasion * Cord compression

Question 30

**Differentials** for **soft tissue tumors** arising from the paraspinal soft tissue causing **secondary invasion** of the vertebral column. What are MRI features of these tumors?

Answer 30

* Fibrosarcoma * Rhabdomyosarcoma * Other soft tissue sarcomas MRI features: * Locally invasive mass in the paravertebral tissues * Extension into the vertebral canal * Vertebral destruction - disruption of the hypointense cortex, abnormal intravertebral signal * Spinal cord compression will be noted. * Signal intensity will be variable, but commonly the lesions are iso- to hypointense on T1W images, hyperintense on T2W images, and contrast enhancing

Question 31

What are the most common **intradural-extramedullary** spinal tumors in **dogs**? Less common?

Answer 31

Most common: * Meningioma * Peripheral Nerver Sheath Tumor Less common: * Nephroblastoma

Question 32

What is the most common **intradural-extramedullary** tumor in cats?

Answer 32

* Lymphoma, although most of these of have an extradural component * Meningioma - second most common spinal tumor after lymphoma

Question 33

What are Peripheral Nerve Sheath Tumor?

Answer 33

Peipehral nerve sheath tumors are **spindle cell tumors** that arise from: * Schwan cells * Perineural cells * Firbroblast cells

Question 34

Are PNST malignant or benign in dogs?

Answer 34

Most commonly malignant

Question 35

What are the **common locations** of the **PNST**?

Answer 35

They can arise anywhere from the nerve roots to the most distal portions of the nerves, and for this reason can be found in: * **Intraspinal locations** - most commonly affect of the **nerve roots** of: * Caudal cervical spine * Cranial thoracic spine * **Paravertebral** locations * Brachial plexus * **Various regions** of the body such as the limbs or the head

Question 36

What are MRI characteristics of PNST?

Answer 36

MRI features of **intradural–extramedullary** peripheral nerve sheath tumors include: * Well-marginated mass * Typically iso- to hypointense to the spinal cord on T1W images and hyperintense to the cord on T2W images, with **moderate to marked contrast enhancement** on T1W post-contrast images. Contrast enhancement may be homogeneous or heterogeneous. * The intradural component of the lesion causes **focal expansion** of the **subarachnoid space**; as described earlier, this is more easily seen on T2W images owing to the hyperintense signal of the CSF outlining the intradural mass. The focal expansion of the subarachnoid space along the cranial and/or caudal margins of the intradural component of the lesion can form a **‘golf-tee’ sign**, similar to that observed on myelographic images, particularly on sagittal or dorsal plane images depending on the location of the lesion relative to the spinal cord. The combined **intradural–extradural** location: * Following the **proximal path of the nerve** * Closely associated with the corresponding **intervertebral foramen**, is the more common presentation * The shape of the lesion varies but owing to its origin within the nerve sheath, an **elongated, tubular, or fusiform** shape is common * The classic appearance is that of a tubular mass extending from the intradural compartment across the intervertebral foramen and into the paravertebral soft tissues. The lesion may be **mildly constricted** at the level **where the nerve traverses the dura mater or where it crosses the intervertebral foramen,** which may confer on the lesion a **dumbbell appearance.**

Question 37

What is the **most common** type of **primary spinal cord tumor** (not metastatic) in a **dog**?

Answer 37

Meningioma

Question 38

What are the common **localization** of **meningiomas**? Less common?

Answer 38

Most commonly: * **Intradural– extramedullary** Less commonly: * They occasionally can grow in the **epidural space** Rarely: * Rarely, meningiomas arising from the **leptomeninges** can infiltrate and efface the underlying spinal cord parenchyma thereby **giving the impression of an intramedullary mass**

Question 39

What are **common MRI** features of **Meningiomas**?

Answer 39

* A **well-defined** focal mass * **Extradural–intradural** compartment causing variable degrees of spinal cord compression * **Broad-based dural margin** seen on at least one of the imaging planes * Gradual expansion of the subarachnoid space cranial and caudal to the mass, which can be detected on T2W images, especially in the dorsal or sagittal plane, creating a **‘golf tee’** sign similar to that observed with conventional myelography or CT myelography; heavily T2W MR pulse sequences (‘T2-myelograms’) can be useful in recognizing this sign. * **Extension** of the lesion into the **adjacent intervertebral foramen** along with the nerve roots can occasionally be seen, and may mimic the appearance of a **PNST** * The mass is usually hyperintense to the spinal cord on T2W images or, less commonly, isointense; **ill-defined areas of spinal cord parenchyma** **T2 hyperintensity around the margins of the mass** are occasionally seen, and may represent **edema**. * **_Spontaneous hyperintensity on pre-contrast T1W images_**, ranging from mild to marked, has been reported quite frequently with meningiomas and may be a distinctive feature of this tumor in dogs; however, its cause has not been elucidated. The lesion can also be iso- to hypointense on T1W pre-contrast images. * **Strong, homogeneous contrast enhancement**, commonly with a **‘dural tail’ sign,** seen as strong linear enhancement of the border of the tumor confluent with the adjacent meninges.

Question 40

What are **uncommon MRI** characteristics of **spinal cord meningiomas**?

Answer 40

Location in both the **intradural and extradural** compartments has been reported Atypical presentations are possible: * **Cyst-like** mass lesion associated with the **dorsal subarachnoid space** in the **cranial cervical spine**, with signal intensity **similar to that of CSF** (T2 hyperintense, T1 hypointense, suppressed on T2-FLAIR, and non-enhancing) has been reported in one case of a spinal cystic meningioma. The myelographic and MRI appearance was similar to that of a *spinal arachnoid diverticulum.* * Very rarely, **leptomeningeal meningiomas** can infiltrate and efface the underlying spinal cord parenchyma and g**ive the impression of an intra-medullary mass lesion.** If **adjacent meningeal enhancement** is present, the appearance *may be confused with other neoplasms such as histiocytic sarcoma*.

Question 41

What are **nephroblastomas** and how are they formed? What are **common locations?**

Answer 41

* Nephroblastoma is a rare embryonic tumor arising from the **primitive metanephric blastema**. During embryonic development, this tissue normally differentiates into epithelial and stromal components to form the nephrons and connective tissue of the **kidneys**. * Cells that do **not differentiate** comprise the ‘**nephrogenic rest**’ and **eventually undergo apoptosis.** * A nephroblastoma is thought to arise from **neoplastic transformation of persistent nephrogenic rest** that did not undergo apoptosis. This can develop in the: * **Kidney** * **Spine** * When embryonic tissue becomes trapped in the **dura** during development. * The tumor is most commonly **intradural–extramedullary** and located consistently **between T9 and L3** * Spinal nephroblastomas typically have histomorphometric features of **malignant** lesions, although **metastatic disease is rare.**

Question 42

Do **spinal nephroblastomas** usually **metastasize**? What is the common **signalment**?

Answer 42

* Spinal nephroblastomas typically have histomorphometric features of malignant lesions, although **metastatic disease is rare** * Spinal nephroblastoma occurs typically in **young (less than 3 years** old) dogs. * Some studies have suggested a predisposition in **German Shepherd** Dogs, although other series did not observe this predisposition.

Question 43

MRI features of **spinal nephroblastomas?**

Answer 43

* A focal rounded, oval-shaped or lobulated mass * **Intradural–extramedullary** compartment or, less commonly, intramedullary location (rarely extradural). * The mass is typically **_isointense to the cord on T2W images_** or, occasionally, has a T2 heterogeneous signal or a T2 hyperintense peripheral rim. * Areas of **T2 hyperintensity in the spinal cord parenchyma adjacent** to the mass lesion may be present, and could represent **edema or gliosis.** * The mass is **_isointense to the cord on T1W_** images * **Moderate to strong, often homogeneous, contrast enhancement** after gadolinium injection. * Transverse and dorsal images typically show the **peripheral location** of the mass in the dural sac * Often with a **broad base towards the meninges** * Widening of the subarachnoid space cranial or caudal to the mass can be present and help in determining the intra-dural location of the mass; however, this sign is not consistently seen and it can be difficult to determine the intradural–extramedullary versus intramedullary origin of the mass, especially when the tumor focally invades the cord or arises from the pia mater.

Question 44

What MRI feature of **nephroblastoma** indicates **poor prognosis**?

Answer 44

The only MRI criterion that may be associated with prognosis is the **location** of the lesion: * intradural extramedullarylesions having a better prognosis than **intramedullary** lesions

Question 45

What is the most common type of **primary** intramedullary spinal cord tumors in dogs? Where are they commonly **located**?

Answer 45

In dogs, intramedullary tumors account for about **15% of all spinal tumors:** Most common primary (in order): * **Ependymoma** * Astrocytoma * Nephroblastoma, Chordoma, oligodendroglioma, and teratoma. * Gliomatosis cerebri is a diffuse glial CNS neoplasia where neoplastic cells reminiscent of astrocytes, oligodendrocytes, or cells with a transitional appearance insinuate among normal structures with minimal damage to neurons and axons. It is a widespread disease that frequently involves multiple divisions of the CNS, including the spinal cord * Hemangioblastoma * Hemangioma In dogs, intramedullary tumors overall tend to be more common in the **T3-L3 segment**, although **primary tumors** tend to be more common in the **cervical spine**

Question 46

What are **less common intradural spinal cord tumors** in dogs?

Answer 46

* Spinal metastatis from intracranial choroid plexus carcinomas * Intradural lumbosacral choiroid plexus papilloma (1 report in Shar-Pei) * Diffuse spinal meningeal oligodendrogliomatosis (2 boxers and 1 Stafford Bull Terrier)

Question 47

What is the most common type of **metastatic** intramedullary spinal cord tumors in dogs?

Answer 47

Most common: * Transitional cell carcinoma * Hemangiosarcoma Less common: * Pheochromocytoma * Mammary/pancreatic/prostatic carcinoma * Sarcoma of unknown origin

Question 48

What is the **most common location** of **intramedullary spinal cord** tumors? What about **primary** intramedullary spinal cord tumors?

Answer 48

* In dogs, intramedullary tumors overall tend to be more common in the **T3-L3** segment * Although **primary tumors** tend to be more common in the **cervical spine**

Question 49

What are the most common types of intramedullary spinal cord neoplasia in **cats**? What **location** do they usually arise?

Answer 49

Intramedullary neoplasia is even less common in cats, and most are glial cell tumors. Most most commonly (in order): * **Astrocytomas** * Ependymomas * Oligodendrogliomas They seem to be more common in the **cervical spinal** cord.

Question 50

What are **general** **MRI features** of **intramedullary spinal cord tumors**?

Answer 50

* Thinning or attenuation of the subarachnoid space +/− epidural fat, best appreciated on T2W images * Swelling of the cord in all planes * Variable amounts of intraparenchymal contrast enhancement

Question 51

What are MRI features of **spinal cord ependyomas**?

Answer 51

* Ependymomas can form **fusiform or oval-shaped**, **focal, or multifocal** lesions on *sagittal images* * On *transverse images* the lesions are **centrally located** (due to their association with the **ependymal lining the central canal**) * They are iso- or hypointense on T1W images, heterogeneously hyperintense on T2W images, with **marked contrast enhancement**, * Can contain **cyst-like components** **(T2 hyperintense, T1 hypointense, non-enhancing, or ring-enhancing).**

Question 52

What are MRI features of spinal cord **astrocytomas and oligodendrogliomas**?

Answer 52

Astrocytomas and oligodendrogliomas form: * **Ovoid or elliptica**l mass lesions * **Well marginated** * Located **_eccentrically_** in the spinal cord on transverse images * tVariable degrees of spinal cord expansion * he lesions are iso- or hypointense on T1W images, hyperintense on T2W and STIR images, with **moderate enhancement** on T1W images post contrast injection * **Mucinous oligodendroglioma** may form extensive lesions replacing the normal cord parenchyma; this variant is formed of neoplastic cells separated by mucin causing a discontinuous patchy enhancement pattern

Question 53

What are MRI features of **intramedullary** spinal cord **metastatic** disease from **TCC**?

Answer 53

* **Intramedullary** masses that are T1 isointense, T2 hyperintense, with **mild uniform enhancement** on T1W post-contrast image * Enlargement of the caudal **sublumbar lymph nodes** (such as the medial iliac lymph nodes), which appear **T2 and STIR hyperintense** secondary to metastatic infiltration * Concurrent **lytic vertebral lesions** may also be present. The appearance of intramedullary metastatic disease is likely varia- ble depending on the nature of the primary tumor

Question 54

What are the MRI features of **metastatic intramedullary** spinal cord **hemangiosarcoma**?

Answer 54

* Variable signal intensity on T1W images * Hyperintense on T2W images * Marked diffuse contrast enhancement or ring-like enhancement * Areas of **low signal** secondary to **hemorrhagic foci** may be present on **T2W images** and **T2\*W images**

Question 55

What are the MRI features of spinal cord **hemangioblastoma**?

Answer 55

The appearance of spinal cord hemangioblastoma has been rarely reported. * A **well-defined intramedullary** mass is seen * **_T2 hypo-_ or hyperintense** * **_Mildly hyperintense on T1W_** pre-contrast images * On T1W post-contrast images, there is either diffuse strong contrast enhancement or rim enhancement.

Question 56

What are MRI features of intramedullary **spinal cord hemangioma**?

Answer 56

_A capillary hemangioma_ formed an: * Intramedullary mass * Heterogeneous but mostly hyperintense on T2W images * **_Mildly hyperintense on T1W_** images * Strong homogeneous contrast enhancement except for a central area. _A cavernous hemangioma_ formed a focal: * Intramedullary mass * **Target-like** appearance: * On T2W images there was a small isointense center surrounded by a large hyperintense area and a peripheral hypointense region * On T1W images there was a large hypointense center surrounded by a small hyperintense periphery and a peripheral hypointense region * **No contrast enhancement**

Question 57

What **breeds** are **predisposed** to **hystiocytic sarcomas**? What are the **two forms** of it and what are the common **locations**?

Answer 57

Breeds: * Bernese Mountain Dog * Rottweiler * Golden Retriever * Flat-coated Retriever * Labrador Retriever Retrievers and Pembroke Welsh Corgis may be predisposed to CNS involvement with histiocytic sarcoma, with **Corgis** possibly predisposed to the **primary CNS** form. _Classification:_ * **Localized:** * Most commonly a soft tissue mass along the **limbs** * CNS * **Disseminated:** * Spleen * Liver * Lungs * Lymph nodes * Bone marrow * CNS

Question 58

What are MRI features of **spinal cord hystiocytic sarcomas**?

Answer 58

* **Focal or multifocal** **intramedullary and/or intraduralextramedullary** mass lesion(s), most commonly isointense (less commonly hypo- or hyperintense) on T1W images, hyperintense or of mixed signal intensity on T2W images, hyperintense on STIR, with moderate to marked contrast enhancement after gadolinium injection * **Ill-defined** diffuse intramedullary T2 hyperintensity with l**oss of the epidural fat and gray/white matter definition**, moderate parenchymal contrast enhancement after gadolinium injection, and **mild diffuse meningeal enhancement.** * Meningeal enhancement in the vicinity of focal mass lesions, **sometimes with a dural tail sign.** * **Meningeal enhancement often extends over long distances** from the mass lesion, and isolated areas of meningeal enhancement **distant and separate** from the mass lesion are also possible, suggestive of metastatic spread of the condition through the subarachnoid space. * In some cases, the only abnormality may be meningeal enhancement without a mass lesion (‘leptomeningeal histiocytic sarcoma’). * MRI features of spinal histiocytic sarcoma, such as focal mass lesions, meningeal thickening, and enhancement, can also be seen with other neoplasms such as *lymphoma* or rare tumors such as *meningeal oligodendrogliomatosis*, and are therefore **non-specific.** * Intradural–extramedullary masses with dural tail can also be seen with *meningioma.*

Question 59

What are the most common **organs** that are also affected in **cats** that have **spinal cord lymphoma**?

Answer 59

* Bone marrow * Kidneys * In some reported case series, affected **cats** had lesions in multiple regions of the CNS including the brain, while in other series, **single epidural lesions were more common**

Question 60

What are MRI features of **spinal cord lymphoma** in **dogs**?

Answer 60

* **Multifocal** disease more common than focal disease * Regional involvement of _multiple compartments:_ * **Vertebrae** (none, one, several, or all vertebrae uinvolved) -with possible cortical involvement, seen as patchy **T2W and STIR hyperintense** signal with **enhancement** on T1W post-contrast images, **disrupting the normal hypointense signal of the cortex**. * **Paraspinal soft tissues** - often ill-defined * **Epidural space** - cause variable spinal cord compression * **Leptomeningeal** involvement with enhancement on post-contrast images is also reported, as well as involvement of the **nerve roots and spinal cord parenchyma**. * The vertebral canal and paraspinal components may be seen to communicate through the **intervertebral foramina** Signal characteristics are similar for the lesions in the paraspinal and vertebral canal areas: * T1 iso- to hypointense, T2 and STIR hyperintense, moderately to strongly contrast enhancing. * **In some** cases, the lesions can be **_hyperintense on T1W_** pre-contrast images. * Heterogeneous signal on T2W images, with hypo- and hyperintense areas, is also reported, as well as isointensity to surrounding muscles. Additional lesions that can be seen in the FOV include: * Lymphadenopathy * Hepatomegaly * Splenomegaly * Splenic nodules