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47 Cards in this Set
- Front
- Back
What does a degenerated disk look like on MR?
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Loss of signal on T2
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A broad-based disk bulge=
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A bulging annulus fibrosus
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A focal disk bulge=
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Herniated nucleus pulposus
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What does disruption of the annular fibers look like on MR?
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High signal on T2— “high intensity zone”
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Most common cause of failed back surgery?
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Missed free fragment disk protrusion
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What is a free fragment?
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Disk protrusion that has broken off from the parent disk
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What does a free fragment look like?
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-On CT: soft tissue density with a higher attenuation than that of the thecal sac, located away from the disk space
-On MR: disk material that has moved away from the disk space -No documented preference for cephalad vs. caudal location. |
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What entities can look similar to a free fragment?
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-Conjoined root
-Tarlov cyst |
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What is a conjoined root?
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-Normal variant
-Two nerve roots exiting the thecal sac together -Has attenuation similar to the thecal sac |
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What is a Tarlov cyst?
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-Normal variant
-Dilated nerve root sleeve -Has attenuation similar to the thecal sac |
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Why is a free fragment important to surgeons?
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It means they have to explore more cephalad or caudally during surgery to remove the free fragment
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Which spinal nerve gets stretched by a lateral disk protrusion?
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-The nerve that has already exited the central canal
-Symptoms mimic disk protrusion one level cephalad |
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Define spinal stenosis:
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Encroachment of the bony or soft tissue structures in the spine on one or more of the neural elements
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Define central canal stenosis:
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-Compression of the thecal sac
-Described as mild, moderate, or severe |
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Most common cause of central canal stenosis?
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-Degenerative disease of the facets with associated bony hypertrophy that encroaches on the central canal
-When facets are degenerative, they often have some slippage, which results in buckling of the ligamentum flavum, termed ligamentum flavum hypertrophy |
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Less common causes of canal stenosis?
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Paget disease, achondroplasia, posttraumatic changes, severe spondylolisthesis
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Causes of neuroforaminal stenosis:
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-Facet hypertrophy (most common)
-Free disk fragments -Post-operative scar -Lateral disk protrusion |
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Is the exiting nerve above or below the disk space?
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It’s above
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Where are the lateral recesses?
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They are the bony canals in which the nerve roots lie after they leave the thecal sac and before they enter the neuroforamen
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Define spondylolysis:
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Defects in the bony pars interarticularis
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What does it look like?
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Seen better on CT
Identified on axial images through the midvertebral body as a break in the normally intact bony ring of the laminae |
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Causes of spondylolisthesis:
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-Slippage of vertebral bodies due to bilateral spondylolysis (can be severe)
-DJD of the facets with slippage (usually minimal) |
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How can you tell post-op scar tissue from disk material?
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Scar tissue enhances, disk material only has peripheral enhancement (presumably due to inflammation)
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Describe type 1 bony changes in DJD:
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T1: low signal bands that parallel the endplates
T2: these bands get brighter |
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Causes of type 1 bony changes?
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-They represent inflammatory or granulomatous response to degenerative disk disease
-Fibrovascular marrow replacement |
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Describe type 2 bony changes in DJD:
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T1: high signal bands that parallel the endplates
T2: these bands remain high signal |
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Causes of type 2 bony changes?
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They represent fatty marrow conversion
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How do you distinguish type 2 changes from disk space infection?
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In disk space infection, the disk should be bright on T2
A degenerative disk is not bright on T2 |
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Describe type 3 bony changes in DJD:
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Parallel bands of low signal adjacent to the endplates on both T1 and T2
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Causes of type 3 bony changes in DJD?
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They represent bony sclerosis with little residual marrow
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