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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6022_Библиотеки_им_академика_М_И_Перельмана
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thelowerprotrusioncorrespondstoA,slightlycompressingthespinal
cord.
CSF,cerebrospinalfluid.
FIGURE 6.41 Axial FSE-T2 MR image shows a prominent disc
protrusion posterior to the L5 vertebra in the left lateral recess,
compressing and posteriorly displacing the traversing left L5 nerve
root. There is superb delineation between the CSF, disc, and nerve
roots.
Source: From Lee RR. Recent advances in spinal MRI. In: Lee RR, ed. Spinal Imaging.
Philadelphia,PA:Hanley&Belfus;1995:45–60.
Arachnoiditis has many causes but may be associated with a history of
pantopaque myelography or spinal surgery. On MRI, the nerve roots are
thickenedandclumpedandexhibitvariableenhancement.They mayadhere to
the periphery of the thecal sac. Intrathecal arachnoid bands or cysts may be
present(Figure6.44).
Another postoperative complication is improperly positioned spinal
hardware.Asdiscussedearlier,titaniumhardwareisbettervisualizedonCTand
MRI than stainless steel (Figures 6.3, 6.9, and 6.10). Occasionally, CT
demonstrates metal hardware directly impingingon spinal nerve roots (Figure
6.45).
INFLAMMATIONANDDEMYELINATION
Forpurposesof evaluating demyelinating disease of the spinal cord and other
inflammatory, intramedullary processes, MRI stands essentially alone as an
imagingtool.MyelographyandCTcanshowlittlemoreofthespinalcordthan
changein contour,whereas MRI revealsinformationabout the contentsofthe
spinal cord itself. However, the findings on MRI are often nonspecific,
especiallyforasolitarylesion.
The plaques of multiple sclerosis (MS) appear as areas of high signal
intensitywithinthespinalcordonT2-weightedimages.Theyoftenoccuratthe
dorsolateralmarginof the spinal cord but can be seen elsewhere in the spinal
cord.Asinthebrain,enhancementsometimesoccursinacuteplaques,butlack
ofenhancementdoesnotexcludeaplaque(75).Inthepresenceofacuteplaques,
the spinal cord can be enlarged, which can create concern for a possible
neoplasm.Forthisreason,whenalesionisidentifiedonMRIwithinthespinal
cord, even if it enhances, it is appropriate to consider MS in the differential
diagnosisandtoobtainMRIofthebraintolookforadditionalevidenceofMS.
FindingmultiplespinalcordlesionsincreasesthelikelihoodofMSandmakes
neoplasmmuchlesslikely(Figure6.46).
FIGURE6.42Cervicalspinalcordcompressionandgliosiscausedby
largediscprotrusionsina62-year-oldman.Sagittal(A)T1-weighted
and (B) T2-weighted MR images show large disc protrusions at
essentially all cervical levels with spinal cord compression and
flatteningatC3–C4andC5–C6.AsmallfocusofT2-brightgliosisis
presentwithinthespinalcord(B)associatedwiththecompressionat
C3–C4.
FSE,Fastspin-echo.
FIGURE6.43Ossificationofposteriorlongitudinalligamentina60year-old man. Axial CT image through C4 (A) and (B) sagittal CT
reconstruction show a calcified, thickened posterior longitudinal
ligament(blackarrow)compromisingthespinalcanal.
FIGURE 6.44 Pathologically proven arachnoiditis and central
intradural arachnoid cyst in a 61-year-old man with prior lumbar
surgery. Axial T2-weighted MR image at the L5–S1 level shows a
centralarachnoidcystwithnerverootsclumpedtogetheranddisplaced
lateraltothecyst.Oldlefthemilaminectomydefectnoted.
FIGURE 6.45 Sixty-four-year-old man with left S1 radiculopathy
afterspinal surgery. Axial imagefrompostmyelogram CTshows the
leftpediclescrewincorrectlypositionedwithintheleftS1neuralcanal
obliterating the left S1 nerve root and correlating with the patient’s
symptoms.Therightpediclescrewismalpositionedmedialtotheright
S1neuralcanal.TheblackarrowpointstotherightS1nerverootinits
neuralcanal.
FIGURE6.46Multiplesclerosis.Thisyoungadulthadlowerandthen
upperextremitynumbness.SagittalT2-weightedimageofthecervical
spinecord(A)showstwoseparateareasofhighsignalintensitywithin
thespinalcord(arrows).SagittalT2-weightedimageofthebrain(B)
showsaplaqueintheinferiormarginofthecorpuscallosum(arrow).
Devic’s disease, or neuromyelitis optica, usually lacks the typical brain
findings seen in MS. Spinalcord lesions in Devic’sdisease areusually larger
than MS plaques and have significantlongitudinalextent, often several spinal
segments(Figure6.47).Findingsofopticneuritishelpestablishthediagnosis.
Transverse myelitis is usually readily apparent on MRI as a region of
increased T2 signal intensity, often having an elongated or spindle shape on
sagittalimages(Figure6.48).Thetermencompassesinflammationofthespinal
cordfromavarietyofcauses,buttheimagingappearanceisusuallynonspecific
(76).
Imaging plays an ancillary role in the evaluation of the patient with
suspectedGuillain–Barrésyndrome.However,ifMRIofthespineisperformed,
the nerve roots often appear thickened, and they enhance after intravenous
contrastadministration(Figure6.49).Suchenhancementisnotspecificandcan
alsobeseenwithdropmetastasesorwithinfection.InGuillain–Barrésyndrome,
enhancementofbothventralanddorsalnerverootsoronlyventralnerveroots
canbeseen;thelatterismorespecific(77,78).
FIGURE 6.47 Devic’s disease. Sagittal T2-weighted (A) and
postcontrastT1-weighted(B)imagesofthelowerthoracicspineshow
a long segment of T2-prolongation, mild expansion, and contrast
enhancement within the lower thoracic spinal cord, extending over
several spinal segments. Postcontrast fat-saturated sagittal T1 of the
orbitand brain(C) showsmarkedenhancement ofthe opticnervein
theposteriororbit,representingopticneuritis.
FIGURE6.48Transversemyelitis.SagittalT2-weightedMRimageof
patient who developed urinary retention and a cervical spinal cord
sensory and motor deficit level 3 weeks after a respiratory illness
shows a region of high signal intensity in the cervical spinal cord.
Abnormalsignalcontinuedintothethoracicspine.
FIGURE6.49Guillain–Barré.Axial T1-weightedimage throughthe
lumbar spine after intravenous gadolinium-DTPA administration
showsintenseenhancementofthelumbarnerveroots.
Gd-DTPA,gadolinium-DTPA.
FIGURE6.50RAandbasilarinvagination.SagittalT2-weightedMR
image of a woman with RA shows erosion of the dens and basilar
invagination, with the dens nearly to the level of the pons.
SubluxationsatC2–C3andC4–C5typicalofRAarenoted.
RA,rheumatoidarthritis.
The spinal canal and cord can also be compromised by extradural
inflammatoryprocessessuchasRA.Avarietyofconditionscanaffectthespinal
cord,especiallyinthecervicalspine.Erosionscanleadtosubluxation.Pannusin
theregionofthesynovialspaceatthetransverseligamentcanleadtoweakening
or destruction of the ligament, with subsequent instability at C1–C2. The
softening of bone and ligament destruction can result in basilar invagination,
threateningthebrainstemitself.PlainfilmsandCTcandemonstratetheerosive
changesandsubluxation,andMRIcanshowthepannusandtherelationshipof
pannusandbonetothespinalcord(Figure6.50).
Patients with long-standing ankylosing spondylitis may develop cauda
equinasyndrome. Their lumbar MRImaydemonstrate a classic appearanceof
intrathecal arachnoiditis and a dilated thecal sac with erosion of the posterior
elements(79),obviatingtheneedformyelography(Figure6.51).
SPINALINFECTIONS
The incidence of central nervous system (CNS) infections, including spinal
involvement,hasincreasedinrecentdecadeslargelybecauseofAIDS(80).The
mostcommonsiteofspinalinfectionisthevertebralbodiesanddiscs,whichcan
then exert mass effect on the thecal sac, spinal cord, and nerve roots. Direct
involvement of the epidural space is also common. Spinal infectionscan also
involvetheintraduralspace(Figure6.52),beingeitherextramedullary,involving
the meninges, as in arachnoiditis, or intramedullary, involving the spinal cord
andcaudaequinadirectly(asinparenchymalmyelitis,granuloma,orabscess).
FIGURE 6.51 Cauda equina syndrome in a 59-year-old man with
long-standing ankylosing spondylitis. Axial T2-weighted image
through the upper lumbar spine shows a patulous thecal sac with
scalloped, eroded posterior elements. The inflamed, scarred nerve
rootsadheretothewallsofthethecalsac.
Diagnostic imaging is essential in the diagnosis and treatment of patients
with spinal infections. Conventional radiographs may be useful in initial
evaluation of spinal infection involving the vertebrae and discs and can
classicallydemonstratethelossofheightofthedisc,erosionoftheadjacentendplates,andlossofvertebralbodyheight.Themostcommonbacterialorganism
is Staphylococcus; others are Enterobacter, Salmonella, Pseudomonas, and
Serratiaspecies(81). However,although associated softtissuemasses may be
demonstrated on plain films, only the bony cortical structures are well
demonstrated.
CTdemonstratesboth thebonyanatomy andsoft tissueanatomyon crosssectionalimages.However,the spinal cord is not delineated unless intrathecal
contrast is introduced (myelography)—an invasive procedure. Computergenerated sagittal (and/or coronal) reconstructions are necessary to appreciate
theabnormalitiesofalignmentandthe3Danatomyoftheinfectedspine.
MRI is the modality of choice in imaging spinal infections because it
noninvasively and clearly demonstrates soft tissue anatomy and pathology
includingspinalcordornerverootinvolvementinadditiontothebonyanatomy
demonstrated on plain x-rays. MRI can directly image in the sagittal (or any
other)planeinadditiontotheaxialplane.
Pyogenicinfectionsgenerallyinvolvetheintervertebraldiscandtheadjacent
portionsofthevertebralbodieswithlossofdemarcationoftheend-platecortex.
ThediscandvertebraedemonstratedecreasedsignalonT1-weightedimagesand
increasedsignalonT2-weightedimages(82)(Figure6.53).AstudybyModicet
al.(82)reportedthatMRIhasasensitivityof96%,aspecificityof93%,andan
accuracy of 94% in the evaluation of osteomyelitis, equaling the results of
combined bone and gallium scanning, but with the added benefits of superb
anatomic resolution as well as visualization of the soft tissues including the
spinalcord,thecalsac,andparaspinaltissues.
Epidural abscesses are often found in association with bony osteomyelitis
and diskitis (Figure 6.53) but also may be an isolated finding (Figure 6.54).
Again, MRI is the imaging modality of choice, especially with the use of
intravenous gadolinium-DTPA. Staphylococcus aureus is the most common
causativeorganism(occurringinabout60%ofcases).Another13%ofcasesare
caused by other gram-positive cocci, and 15% are caused by gram-negative
organisms(80,83,84).MostepiduralabscessesenhancehomogeneouslywithIV
Gd-DTPA, suggesting that they are largely phlegmonous, but nonenhancing
frankpusmayalsoberecognizedasacentralcollectionoffluidlikeT1-dark,T2brightsignalsurroundedbyanenhancingsofttissuerim(Figures6.53and6.54).
Brucellosispresentswithbonylyticlesionsofthevertebralbody,usuallyinthe
lowerlumbarspine(85,86).
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