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Myelography

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sihirlifil's version from 2017-10-22 04:22

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Question Answer
Indications for myelography (5)Confirm spinal compressive lesion
Extent of lesion
ID of lesions that cant be seen on survey radiographs (soft tissue opacity)
Distinguish between surgical & non-surgical lesions
Exact localization of lesion (which vert segment), decide on best sx approach
What should you always do before contrast study?Survey radiographs (Lat and VD)
Myelography technique: where is the positive contrast medium going?Subarachnoid space (between pia & dura mater)
Myelography technique: what is the contrast medium?Non-ionic low osmolar iodinated contrast
Myelography technique: how to sedate?Trick q- NEED GA! And aseptic conditions
Myelography technique: Where is the injection?Dogs: Cisterna magna (cervical) or L5-L6 (lumbar)
Cats: Cisterna magna or lumbar at L6-L7
Myelography technique: before injecting contrast medium...Sample CSF (save some CSF when you puncture subarachnoid space)
Examples of contrast mediumIohexol (Omnipaque)
Iopamidol (Niopam, Isovue)
Dose of contrast medium0.15-0.3mL/kg
Size needle?21-23G spinal needle. Bevel orients cranially
What helps improve mixing contrast with CSF?Warm contrast medium prior to injection!
Explain what's going on here
Lumbar puncture
Needle advanced to the floor of the vertebral canal through the cauda equina
What do we actually see with myelography?2 radiopaque contrast columns on lateral, VD & oblique projections (=subarachnoid space filled with CSF & contrast medium)
What should the contrast columns look like?Even width
What are the orange arrows?
Natural enlargements of the spinal cord: Cervical and lumbar intumescences
These are the origins of the nerves for the brachial and lumbosacral plexus
(blue arrow = contrast in lumbar area)
What's noteworthy in this image?
Natural widening of caudal cervical spinal cord
No visible narrowing of the contrast columns
Examples of abnormal radiographic findingsDeviation of contrast column: dorsal/ventral/axial
Thinning
Widening
Interruption
Splitting
We can deduce whether there is something...On the outside pushing in (extradural extramedullary)
Swelling of cord (intramedullary)
Something disturbing/occluding contrast flow (intradural extramedullary)
List the myelographic patterns (5)Normal
Extradural extramedullary
Intramedullary
Intradural extramedullary
Intramedullary opacification
Myelographic pattern: normal
Myelographic pattern: ExtraduralIVD protrusion
Ligamentous hypertrophy
Hematoma/hge
Neoplasia (Vertebral or epidural)
Myelographic pattern: Intradural extramedullaryNeoplasia (neurofibroma, neurofibrosarcoma, meningioma)
Myelographic pattern: Intramedullary swellingSpinal cord edema (can be 2ry to disc protrusion)
Neoplasia (neural, metastatic)
Granulomatous meningoencephalitis
Ischemic myelopathy
Myelographic pattern: Intramedullary opacificationMyelomalacia
Hematomelia
Extramedullary extradural: Radiographic signsElevation/deviation and thinning/loss of contrast column(s)
Widening of cord at site of compression
Extramedullary extradural at L2-L3 (narrowed IVD space, typical myelographic finding for IVD protrusion)
Extramedullary extradural: DdxIVD protrusion
Ligamentous hypertrophy (dorsal longitudinal lig)
Hematoma/hge
Neoplasia (vertebral, epidural soft tissue)
Vertebral fracture/dislocation/callus
Extramedullary extradural IVD protrusion (Cervical injection, myelography)
T12-T13: ventral contrast column elevated & thinned, dorsal contrast column thinned, no longer visible caudal
Extramedullary extradural L1-L2
Extramedullary extradural (caudal thoracic)
Intramedullary: Radiographic signs+/- Intramedullary opacification
Intramedullary swelling = contrast columns divergent & thinned (don't mistake intumenscentia)
Intramedullary: DdxNeoplasia (neural, metastatic) (cord swelling without associate trauma)
Granulomatous meningoencephalitis
Cord edema (trauma, 2ry to IVD prolapse)
Ischemic myelopathy
Intramedullary (both projections: contrast moving away)
Intradual extramedullary: Radiographic signsWidening & interruption of contrast column
Golf-tee appearance
Often deviation & thinning/loss of contralateral contrast column
Intradural extramedullary: DdxNeoplasia (neurofibroma, neurofibrosarcoma, meningioma)
Granuloma
Abscess
Intradural extramedullary golf tee!
(can fill with contrast- subarachnoid cyst)
Spinal vertebral neoplasia at T12
Difference in shape, ventral contour, and bone opacity of T12 in comparison to the adjacent vertebral bodies
Spinal vertebral neoplasia at T12: CT myelography (improved diagnosis of vertebral lesions)
Transverse images of T12 (bone window WW=1137, WL=327)
Destructive and expansile nature of lesion affecting predominantly the right side of vertebral body & pedicle, dislpacing SC dorsally & left ((arrow)
What are the radiographically "invisible"lesions?Degenerative myelopathy
Ischemic myelopathy
Myelitis
Meningitis
Fibrocartilagineous embolus
How do you see radiographically "invisible" lesions?MRI
Excellent ST detail, surrounding bone
MRI of IVD prolapse L1-L2 T2 sagittal
Hypointense area at level of L1-L2 IVD space, cord elevated, hyperintense signal of central canal lost at this level
MRI of IVD prolapse L1-L2 SPIR dorsal (get idea of 3D)
MRI of IVD prolapse L1-L2 T2 transverse
MRI of IVD herniation L3-L4
Signal no longer hyperintense, pushes cord away & takes up space
MRI of spinal neoplasia T2 saggital
Filling defect in SC
MRI of spinal neoplasia SPIR dorsal
More gray tissue pushing over to opposite side
"MRI of spinal neoplasia transverse
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