15. CT / MR Spine Flashcards
1
Q
What do the longitudinal ligaments of the spine do?
A
Support discs (dorsal and ventral)
2
Q
Why is root signature more common in cervical spine?
A
Dorsal long. lig. WIDE and THICK in cervical spine - predisposes to LATERAL disc extrusion
3
Q
Where are the intercapital ligaments (in spine and in relation to long. lig.)?
A
T2-T11; Ventral to dorsal long. lig. Buttress dorsal asepct of disc.
4
Q
Interarcuate ligaments are also known as what?
A
Yellow ligaments, ligamentum flavum
5
Q
Where is the conus medullaris located in cats, small and large breed dogs?
A
- Cats / small breeds: caudal to L6
- Large breeds: cranial to L6
6
Q
Describe relationship of spinal cord segments to vertebral segments
A
- Numerically matched EXCEPT C8!!!
- Tend to be cranial to vertebra
7
Q
How does the spinal cord diameter : vertebral canal diameter vary between breeds?
A
- Higher in chondrodystrophic (e.g. dachs)
8
Q
Describe meninges, their relationships, and assocaited spaces
A
- Pia mater: tightly adhered to cord, vascular
- SUBARACHNOID SPACE: Arachnoid trabeculae, and CSF!!
- Arachnoid membrane: Closely assocaited with Dura
- SUBDURAL SPACE
- Dura Mater: Outermost, close association with arachnoid.
- EPIDURAL SPACE: Contains fat and vertebral venous plexus
9
Q
Where is spinal CSF located? Where does this compartment extend to / communicate with?
A
- SUBARACHNOID SPACE
Cranially: Intracranial SA space
Caudally: Terminates at filum terminale
- CENTRAL SPINAL CANAL
Cranially: 4th ventricle
Caudally: Terminates at conus medullaris
10
Q
Where is the basivertebral venous canal located?
A
- Midportion of vertebral body: y shaped lucency extending towards canal. Dorsal bony protrusion at this level.
11
Q
LIGAMENTS! See pic
A
12
Q
How much contrast is injected for CT myelo?
A
25% normal myelo dose
13
Q
What are the annulus and nucleus made out of?
A
Fibrocartilage
- Differr in amount of collagen and ground substance
Annulus: More collagen and less ground
14
Q
What is the principal component of the nucleus pulposus?
A
Water (bound to large proteoglycan molecules) = 80-88%
15
Q
Hansen type 1 vs type 2!
A
Type 1: Chondrodystrophic, loss of elasticity, inc collage / mineralisation -> Annulus rupture and extrusion
AGE: PEAK 4-5yrs
Type 2: Nonchondrodystrophic, Fibroid degeneration, annular protrusion and shifting of central nuclear material
AGE: 8-10yrs
16
Q
DISC CLASSIFICATION ALGORITH
A
17
Q
What imaging features make protrusion / extrusion more likely?
A
- Protrusion: Paritally degnerate, midline, multiple
- Extrusion: Degenerate, lateralised / dispersion, single
18
Q
What is a discal cyst?
A
- MISNOMER: NOW CALLED = COMPRESSIVE HNPE - hydrated nucleus pulposus extrusion, !
19
Q
What CT settings should be used to evaluate discs?
A
Thin slices (1-2mm), low pitch (<2) and medium freq algorithm
20
Q
What percentage of dachsunds have transitional vertebral anatomy?
A
10%
21
Q
On CT, how does extruded disk material appear in chondrodystrophic dogs?
A
- Large volume hyperattenuating (200HU)
- Small volume less hyperattenuating (60HU) -> corresponds to haemorrhage
- IF CHRONIC: material even more hyper (700HU) as continues to mineralise
22
Q
What is the bony ridge seen in the midportion of the vertebral body on CT?
A
- Most likely = small bony ridge between dorsal vertebral foramina
- Other suggestion: Mineralisation of dorsal long. lig.
23
Q
When is CT myelography likely to be required for dx of spinal disease?
A
- Non-chondrodystrophic (less mineralisation)
- Chondro with concurretn extradural compression and cord swelling
24
Q
What features of IVDE are reported on MR?
A
- attenuation of epidural fat
- Extradural compression at level of disc space
- narrowing of disc space
- Degen of disc
25
What is the incidence of epidural haemorrhage / inflammation in thoracolumbar / lumbosacral disc herniation?
- Approx 5%
=\> Typically more caudal lumbar discs, and with migration of material
T2: Hyper or hetero
T1: Hyper, hypo or iso
T2\* signal void
Freq CE!
=\> No apparent difference in outcome if present
26
In what percentage of dogs with disc extrusion do we see CE of disc material / meninges?
- Disc material: 50%
- Meninges: 40%
27
What percentage of IVDD is cervical in dogs? Which dogs and where?
- 14-16%
- Small dogs typically (dachs, beagles): C2-C5
- Large dogs (Labs, GSDs): C4-5 and C6-7
=\> Thick dorsal long lig -\> often results in dorsolateral extrusion, and nerve root compression
28
Where does IVDD most commonly occur in TL spine? Which breed has unique distribution?
- T12-L1
- GSDs: Can have cranial thoracic discs (despite intercapital ligs!) -\> T2-5
29
Name imaging features associated with worse neuro grade and prognosis in TL IVDD?
- Length of compressed cord -\> associated with neuro grade (not outcome)
- Length of T2 IM hyperintensity \> L2 associated with poorer outcome in approx 50% patients
30
Name 4 characteristics that can be seen with LS stenosis
- Disc extrusion / protrusion
- New bone at endplates / articular processes
- Subluxation
- Thickening of lig flavum / joint capsule
31
Where is foraminal extrusion most commonly identiifed? What is ganglioneuritis?!
C5-C7, rarely reported in L6-S1
- Rarely, fragements induce mechanical / chemical damage to perineurium +- penetrate root =\> inflam, thickening. MAY BE MISTAKEN FOR NERVE SHEATH TUMOUR
32
MR differences between compressive and noncompressive ANPE?
ANNPE:
- Narrowed disc space
- IM hyper dorsal to space (typically non-enhancing)
- Tract
- T2w hyper extradural material
- Loss of NP volume
Compressive HNPE (C3-6 most common):
- Seagull sign: ventrally positioned extradural T2w hyper, may not suppress on FLAIR
- IM Hyper above space, non enhancing. Iso to hyper on T2\*
- Materrial may enhance
33
What % of patients with ANNPE have an unsuccessful outcome? Px features?
33%
Px:
- Severity of neuro signs at presentation
- CS area of IM hyper: If \>90%, 92% chance of unsuccessful outcome
34
What features have been described with dural tear?
- Tract crossing spinal cord contiguous with intervertebral disc space
- Myelography: Leakage from SA -\> epirdural space; into disc if traction applied; Into cord
35
Features of disc associated CSM
- Disc bulging / herniation
- Lig flav hyper (dorsal compression)
- IM inc signal (\* associated with clinically relevant cord compression\*, but not px)
- Vert body abnormalities / spndylosis
36
DDx for T2w IM hyperintensity in CSM? And if T1w hypo concurrently?
T2w hyper: Gliosis, oedema, nerve cell loss. In white matter, demyelination, oedema and wallerian degen
w/ T1w hypo: MORE SEVERE CHANGES MAY BE PRESENT -\> necrosis, myelomalaxia, spongiform change
37
Osseus associated CSM features:
- NOTE YOUNG dobermans get this too!!! And other large breeds e.g. G Dane
- Disc degen +- protrusion (occasional)
- Osteoarthritis of articular process joints and dorsal long lig hyper (C3 - T1; worse at C4-7) -\> dorsal compression
- Synovial cysts
NB: High incidence of features in clinically normal dogs. G Danes can have severe foraminal stenosis without CS, and occasional spinal cord compression
38
List three common cystic lesions of spine; and one uncommon
Common:
- Arachnoid cysts
- Dermoid / epidermoid cysts
- Synovial / ganglion cysts
Uncommon:
- Perineural (Tarlov) -\> originate from dorsal nerve root and ganglion sheath. EXTRADURAL (unlike arachnoid diverticula), filled with CSF and contain neural structures
39
List 4 causes of arachnoid diverticula
1) Congenital
2) Trauma
3) Arachnoiditis
4) IVDD
IN SUBARACHNOID SPACE -\> Communicate freely with CSF
40
Common locations and breeds for SAD?
PUGS: Thoracic (typically caudal). A familial type of cervical SAD reported.
ROTTIS: Cervical (typically cranial)
\*\* can be single or multiple\*\*
Located in subarachnoid space, lined by pia and arachnoid
41
MR Features of SAD
- Teardrop shape continguous with SA
- T1 hypo, T2 hyper and typically null on FLAIR
- Compression (usually dorsal)
- IM hyper (Oedema)
- Syrinx
42
Difference between dermoid and epidermoid cyst / sinus?
- Cyst vs sinus: Discrete if cyst, tract to skin surface if sinus
- DERMOID = Contain sweat glands, hair follicles, sebaceous glands
- Epidermoid = Lined by squamous epithelium, contains cholesterol, keratin, epithelial cells. Can cause chemical meningitis if ruptured!
43
Six types of dermoid cyst / sinus (attached Vet Clinics pic - first 4 types)
Which 2 types are associated with neuro abnormalities?
See image\*
Type 5: True dermoid cyst - closed capsule, no deeper connection or communication with skin
Type 6: Deep tract extends to supraspinois or nuchal lig and contineus deeper as fibrous strand that connects to dura mater
NEURO SIGNS: only 4 and 6 as involve dura mater
44
List 4 causes of neuro signs in association with dermoid cyst
1) Infection (abscessation, meningomyelitis etc)
2) Compression
3) Tethered cord
4) Syringomyelia
45
MR features of dermoid cyst
- Invagination of cut tissue
- Focal roudned or lenticular SC lesion, and tubular tract (variable signal depending on content)
- Thick capsule if absecess
...MOre depending on appearance. Be familar with diagrams and likely can figure out MR appearance!
46
Name 4 vertebral anomalies associated with dermoid cyst / sinus
1) Spina bifida
2) Block vertebrae
3) Incompletel dorsal lamina
4) Fusion of spinous processes
47
MR features of dural connection with dermoid sinus
- Dorsal tenting of meninges
- Triangular subarachnoid space - point of tether dorsally
- Dorsal displacement of cord at site of tethering
48
Where are articular process cysts typically located, and in which breed categories?
- Typically cervical and multiple in young GIANT breeds
- Typically thoracolumbar or lumbosacral in adult and older LARGE breeds
49
In general terms, which tumours are found at extradural, intradural-extramedullary and intramedullary locations?
- Extradural: Vertebra soft tissue tumours
- Intradural-extramedullary: Nerve sheath or meningioma
- Intramedullary: Glial, round cell or metastatic (e.g. HSA)
50
List extradural tumours
Most common: OSA, CSA IN DOGS; LSA in cats
- Histio SA
- MM
- Mets: TCC, prostatic C
- Soft tissue: STS, Infiltrative lipoma
No specific CT or MR features with tumour type (except lipoma!)
51
List intradural-extramedullary
- 33% of spinal tumours!
- Nerve S
- Meningioma
- Cats: Lymphoma (most common) -\> often have extradural component
- Rare: Neprhoblastoma
52
Ct features of nerve sheath tumour?
- Muscle atrophy
- ST mass, iso to muscle
- CE: uniform, patchy or rimlike
- May track into foramen /invade canal
- \> Can identify as small as 1cm.
53
What is the golf-tee sign a hallmark of?
Intradural-extramedullary lesion
54
Features of nephroblastoma?
- YOUNG dogs (\<3)
- Typically T10-L2 (region of kidneys??)
- Usually a single mass, although mets reported
- Enhancing
- Features of intradural, extramedullary location.....
-
55
List 6 PRIMARY intramedullary tumours of the dog
- EPENDYMOMA (Most common)
- Astrocytoma (next)
- Nephroblastoma, chordoma, oligodendroglioma, teratoma
56
List metastatic intramedullary tumours
Most common:
- TCC
- HSA
Other:
- Carcinomas (prostatic, mammary, pancreatic)
- Sarcoma
Even less common in cats -\> glial cell usually. More likely cervical spine
57
List three spinal tumours that effect multiple locations
HSA
LSA
Histio
58
Describe features of CNS histiocytic sarcoma
- Disseminated vs primary neoplasia
- Retrievers and Pembroke corgis may be predisposed, with latter suspected to be specifucally preodiscposed to primary form
- May arise from vertebra, soft tissues around bone, or directly within CNS
- EXTRADURAL, INTRADURAL / EXTRAMEDULLARY or INTRAMEDULLARY
- Multiple non specific MR features, but may include meningeal enhancement and dural tail (may be only feature)
59
What is the most common neoplasia of the spinal cord in cats?
Lymphoma!
Most commonly extradural, but may be intra or mixed
60
Features of canine spinal lymphoma
- 80% cases multicentric
- Commonly effects multiple spinal compartments (epidural , paraspinal ST, vertebrae, nerve roots, less commonly cord)
- MR features....non-specific, however occasionally CAN BE T1w HYPER!
-
61
Features of spinal HSA
- Intramedullary or extraudral (and in 2-3% originating from vertebra)
- Rarely primarily in epidural space alone
- May be metastatic, more likely if intramedullary
- MRI features.... as would expect. T2\* void!
62
What percentage of dogs develop myelomalacai after IVDE?
10% deep pain neg
63
Features of myelomalacia?
- Cord swelling (length effected may be suggestive)
- IM Hyper
- T2\* void -\> haemorrhage
- May have T2 hypo on high-field = deoxyhaemoglobin
64
Features of Ischaemic myelopathy
- T2 hyper
- Usually assymetric
- Usually grey matter
- Variable CE
- May have T2\* void with haem
- AVERAGE Length of T2 hyper:
1. 8 x C6 or 2.2x L2
=\> 20% cases have normal MRI!
65
What two metrics have been associated with poor outcome in ischaemic myelopathy (both 100% sn)?
Lesion length : vert ratio \> 2
CSA \> 67%
66
MR features of disco?
- T1/T2 hypo endplates and bone marrow ; STIR hyper
- Hyper disc
- CE of disc, endplates and STs
- Endplate erosion, or in early stages T2 hyper marrow
- Compression
Subluxation
67
What feature of syrinx is the strongest predictor of clinical signs?
Syrinx WIDTH!
95% CKCS with max width **\> 0.64cm -\> clinical signs**
68
Causes of meningomyelitis
Infectious
- Viral: distemper, FIP
- Bacterial: Staph, pasteurella, actinomyces, nocardia)
- Fungal: Crypto, blasto, histoplasma, coccidiodes
- Rickettsiae: Ehrlicia, rickettsia ricketsiae
Parasites: Dirofilaria, angio, toxo
Algae: Prototheca
Noninfecitous
- GME, pyogranulometsous, SRMA
69
Know your IM HYPER: px features in ANNPE vs ISCHAEMIC vs TL IVDE?
**ANNPE**
\>90% CSA -\> 92% poor px
**Ischaemic - BOTH 100% sensitive for poor outcome**
\>67% CSA -
\>2x vertebral body length -
**TL IVDE**
Length of T2 IM hyperintensity \> L2 associated with poorer outcome in approx 50% patients
