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What projections do we need at a minimum for the spine of small animals? For large animals?
- SA: lateral and VD
- LA: standing laterals
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Which cervical vertebra has an elongated caudal transverse process?
C6
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How do we use myelography? How is it achieved?
- used to localize the site of spinal cord compression
- neuroanatomical localization
- involves general anesthesia (in LA and SA) and instilling nonionic, iso-osmolar, iondinated contrast medium in the subarachnoid space at the cerebellomedullary cistern or at L5-L6 space
- must remove a volume of CSF and replace with same amount of contrast material
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What is an important precaution to take prior to myelography? Why?
- 22G spinal needle--> collect CSF
- if suggestive of meningoencephalitis, DO NOT PERFORM MYELOGRAPHY
- because we could potentially cause more inflammation in meninges with contrast
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How do you know you have injected contrast into the proper location for myelography? (2)
- sharp definition of ventral aspect of contrast material over the dorsal aspect of the vertebral body; if this line doesn't exist, you've probably put contrast in the epidural space
- linear filling defects (streaks) within contrast material; these are nerve rootlets in the subarachnoid space
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What are complications of myelography? (3)
- general anesthesia risks
- can damage spinal cord (this is why we like to inject contrast at L5-L6 in dogs b/c there is no more cord here)
- seizures (large dogs, large dose, cerebromedullary cistern puncture)
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Describe interpretation of myelography based on location. (3)
- extradural: lesion outside cord, but withing spinal canal
- Intradural/ extramedullary: lesions within subarachnoid space
- Intramedullary: lesion within the spinal cord
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What are differentials for extradural lesions on myelography? (5)
- IVD protrusion
- ligamentous hypertrophy
- hematoma
- vertebral neoplasia
- fracture/ subluxation
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What do extradural lesions look like on myelography? (2)
attenuation of contrast and displacement of cord
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How do intradural/ extramedullary lesions appear on myelography? (3)
- filling defect in subarachnoid space
- displacement of the cord
- golf tee sign (negative black golf ball (filling defect) sitting on a white golf tee; the filling defect is the lesion expanding the subarachnoid space)
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What are differentials for intradural/ extramedullary lesions on myelography? (2)
- nerve root tumor
- meningioma
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How do intramedullary lesions appear on myelography? (2)
- attenuation of subarachnoid space
- increased diameter of spinal cord
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What are differentials for intramedullary lesions on myelography? (3)
- spinal cord edema
- spinal cord hemorrhage
- spinal cord neoplasia
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What aresome congenital anomalies seen in the spine? (6)
- block vertebrae: smooth fusion of vertebrae with no discernible disc space b/w them
- hemivertebrae: vertebra is too short or not proper shape
- spina bifida: failure of fusion of vertebra on midline; often incidental
- scoliosis: lateral deviation of spine
- alignment anomalies: kyphosis (dorsal deviation), lordosis (ventral deviation)
- atlantoaxial subluxation: incomplete dens or ligaments, allowing movement of C2 relative to C1
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Describe cervical malformation/ malarticulation in dogs. (7)
- young danes and older dobermans
- misshapen vertebrae
- subluxation
- narrowed disc spaces
- extradural cord compression
- often dynamic
- Caudal cervical spine most common location (C4-C7)
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Describe cervical malformation/ malarticulation in horses. (6)
- narrow spinal canal
- remodeling of dorsal caudal endplates
- subluxation
- articular process remodeling
- extradural compression on flexion and extension (always do flexion and extension images b/c they often have dynamic compression)
- Cranial cervical spine most common location (C3-C5)
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Describe lumbosacral stenosis. (3)
- larger dogs
- caudal equina syndrome: narrow L7-S1 disc space with wedging, sacral subluxation, secondary spondylosis
- contrast study or CT/MRI necessary: cauda equina dorsally displaced and compressed
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What is spondylosis deformans?
- smooth proliferation arising from the end plates and tends to bridge the ventral and/or lateral aspects of the vertebrae
- can means instability at this location but is not always clinically significant (take clinical picture into account)
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How does IVDD appear on radiographs? (4)
- [disc degeneration leading to disc protrusion]
- narrowed disc space
- small intervertebral foramen
- mineral opacity in canal
- myelography- extradural compression
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Describe the radiographic appearance of discospondylitis. (3)
- [infection in the disc and adjacent vertebral bodies]
- wide disc space
- lytic vertebral end plates
- sclerosis of vertebral bodies
- (DO NOT confuse with spondylitis deformans)(lytic tells you its an aggressive dx- DDx are infection and neoplasia and we know neoplasia doesn't occur at the disc space)
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