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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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FIGURE 6.52 A57-year-oldwoman with pyogenic spinal infection
and left psoas abscess with intradural extension. (A) Sagittal
postcontrast T1-weighted image shows diffuse thickening and
abnormalenhancement of the caudaequinaand enhancing intradural
exudate around the distal spinal cord (small white arrows). The
anteriorportionof theL4 vertebraisinfected.(B)Axial postcontrast
T1-weighted image again shows diffuse thickening and abnormal
enhancementofthe caudaequina (blackarrows).Whitearrowpoints
topusinleftpsoasabscess.
FIGURE6.53PyogenicspinalinfectioninanadultmalewithL5–S1
diskitis, osteomyelitis, and epidural abscess. Left. Sagittal T2-
weightedimageshowsT2-brightpuswithintheL5–S1disc,extending
posteriorly. T2-bright edema or infection is noted involving the
adjacent end-plates. Middle. T1-weighted image better shows the
associated epidural abscess compressing the distal thecal sac.Right.
PostcontrastT1-weightedimageagainshowsenhancingphlegmonous
tissuecompressingtheanterioraspectofthethecalsac.T1-darkpusis
notedcentrallyintheepiduralabscess(arrows).
Tuberculosis(87) differs from pyogenic bacterial infections, in which the
intervertebral disc is often relatively spared inearly disease (possibly because
mycobacterialackproteolyticenzymes).ItappearswithoutabnormalT2-bright
signal,more involvementofposterior aspects ofthevertebrae, involvementof
morethantwovertebralbodies,andlargerassociatedparaspinalmasses.CTmay
showthesmallsofttissuecalcificationssuggestiveoftuberculosis,whicharenot
reliably shown on MRI (88). Chronic tuberculosis infection may result in a
classickyphoticdeformity,knownasPott’sdisease,usuallyinthemid-thoracic
region.
Patients with AIDS may often present with polyradiculopathy caused by
viruses,mostcommonlycytomegalovirus(89).Gadolinium-enhancedMRIisby
farthebestmodalitytovisualizetheenhancingnerverootsofthecaudaequina,
which may appear normal on standard T1- and T2-weighted images;
occasionally,enhancementextendsdiffuselythroughoutthespinalsubarachnoid
space(Figure6.55).InfectionofthespinalcordbytheHIVvirushasbeenfound
tocausevacuolarmyelopathyinAIDSpatients.SpinalMRImaybenormalbut
usuallypresentswith spinalcord atrophyoroccasionallywithT2-bright signal
(90). Enhancement with IV contrast is not generally seen in AIDS-associated
myelopathy(90).
Acuteflaccidmyelitis(AFM)hasbeenreportedintemporalassociationwith
anoutbreakofenterovirusD68infection,andsomecasesofAFMhaveevidence
ofD68 infection.Imaging findingsinclude deepgray matterT2-hyperintensity
with anterior horn predominance and occasional pontine and cerebellar
involvement. Enhancement is sometimes seen in nerve roots. Similar findings
have been reported with West Nile virus, poliomyelitis, and enterovirus 71
infection(91). Infarction canalso manifest as T2-bright signal in central gray
matteronMRI,butisdistinguishedonclinicalgrounds(Figure6.56).
FIGURE 6.54 Twenty-one-year-old woman with autoimmune
hepatitis, chronically on steroids, with diffuse posterior epidural
cryptococcal abscess throughout her spine. Sequential postcontrast
sagittal T1-weighted images of the thoracolumbar spine show an
abscess with thin enhancing rind located posterior to the thoracic
spinal cord and cauda equina and compressing them. Note that the
vertebraeanddiscsarenormal.
FIGURE 6.55 Thirty-one-year-old man with AIDS, who presented
with bilateral leg pain and weakness and loss of bowel and bladder
control.Left. Sagittal T1-weightedMR images of the cervicalspine
are normal, as are sagittal T2-weighted images, Right. (Patient is
angulatedontheT2-weightedimages;thelowerspinalcordisoutof
view so that CSF, rather than cord, is imaged; note that spinous
processes are also out of field.) Middle. However, T1-weighted
images after IV administration of gadolinium-DTPA show diffuse
marked enhancement of inflammatory tissue throughout the spinal
subarachnoidspace(whiteandblackarrows).HerpessimplexIIvirus
wasculturedfromhisCSF,andcytomegaloviruswasculturedfromhis
blood.
CSF,cerebrospinalfluid;Gd-DTPA,gadolinium-DTPA.
SPINALCORDENTRAPMENT/COMPRESSION
IdiopathicAnteriorHerniationoftheSpinalCord
The spinal cord may herniate anteriorly through a defect in the ventral dura,
usuallyinthethoracicspine,withresultantentrapmentandstrangulationofthe
anteriorly herniated cord tissue. Sagittal T2-weighted MRI demonstrates a
characteristicfocallykinkedappearanceofthedorsalspinalcordandwidening
of the corresponding segment of dorsal CSF (92) (Figure 6.57). Surgical
reductionoftheanteriorlyherniatedcordtissue,andsurgicalrepair/closure of
the ventral dural defect, stops progression of symptoms, and often results in
someimprovementofsymptoms.
DorsalThoracicArachnoidWeb
Intradural-extramedullary bands of arachnoid tissue may compress the dorsal
aspect of the spinal cord, usually in the upper thoracic region, causing cordcompressive symptoms. On sagittal T2-weighted images, they have a
characteristic appearance: focal widening of the dorsal CSF space and
compressionof thedorsal spinalcord(93)(Figure6.58). An associated syrinx
may be present in the spinal cord adjacent to the region of compressed cord.
Surgicalresectionofthewebgenerallyresultsinsomeimprovementofpatient
symptoms. Differential diagnosis includes intrathecal dorsal arachnoid cyst or
anteriorherniationofthespinalcord(describedearlier).
FIGURE 6.56 MRI of 3-year-old who presented with right upper
extremity flaccid paralysis after a respiratory illnessshows highT2signalintensityincentralgraymatterofthespinalcord.(A,sagittal,B,
axial)
FIGURE6.57Sagittalreconstructionof axialCT-myelogramimages
shows the characteristic kinked superior and inferior borders of the
thinanteriorly herniatedspinal cordwithwidening oftheCSF space
dorsaltotheanteriorlyherniatedcord(betweenthewhitearrows).
CSF,cerebrospinalfluid.
VASCULARLESIONSANDISCHEMIA
Suspectedvasculardiseaseofthespinecanbeparticularlychallengingtoverify
with imaging. The spinal cord itself is best visualized with MRI, but
angiographycanhaveanimportantroleinsomecases.
FIGURE 6.58 (A) Sagittal T2 MRI demonstrating a focal dorsal
indentation (arrow) in the thoracic spinal cord. (B) Intra-operative
image after opening of the dura demonstrating an intradural white
arachnoidband(betweenarrowheads)passingtransverselyacrossand
compressingthedorsal surfaceof thespinalcord.(C)Intra-operative
image of the cord after the band of arachnoid tissue has been cut.
(Positionmarkedbyarrowheads).
Source:ReardonMA,RaghavanP,Carpenter-BaileyK,etal. Dorsalthoracicarachnoidweb
and the “scalpel sign”: a distinct clinical-radiologic entity. AJNR Am J Neuroradiol.
2013;34:1104–1110.ReprintedwithpermissionfromAJNR.
Spinal cord infarction appears on MRI as a region of increased T2 signal
intensity (Figure 6.59). This appearance is nonspecific, especially because the
vascularterritoriesareusuallynotasobviousinthespinalcordasinthebrain.
Distinction of spinal cord infarction from other entities, such as infectious or
demyelinating processes, is therefore often more dependent on clinical
informationthanondifferencesinimagingappearance.
Vascular malformations of the spine have been divided into four types:
intramedullaryglomus-typearteriovenousmalformation(AVM),juvenileAVM,
duralAVfistula,andperimedullaryAVfistula(94).Patientageandtheclinical
presentationsof thesetendto differ. Symptoms canresultfrom hemorrhageor
fromischemiacausedbyvenoushypertensionorsteal.
Hemorrhage within the spinal cord has an appearance similar to blood
elsewhereintheCNSanddependsontheageofthehemorrhage.Acutespinal
intramedullary hemorrhage (blood) has low T2 signal intensity; subacute
hemorrhage with methemoglobin has T1-shortening (bright on T1-weighted
images) and initially low, then high T2 signal intensity, followed by
hemosiderin,whichismostnotableforlowT2signalintensity(alsodarkonT1).
However,thepatterninacutehemorrhageissometimesdifficulttoidentify,and
hemorrhagein thespinal cordtendsto spreadin alongitudinalmanner,unlike
the brain. Extra-axial, including extradural, hemorrhage is more variable in
signal intensity, and a high level of suspicion is necessary in the setting of
traumaorotherhigh-riskmechanisms.
FIGURE 6.59 Spinal cord infarct in a 68-year-old man sustained
during surgical repair of abdominal aortic aneurysm. Sagittal T2weighted image shows T2-bright edema (white arrows) within the
distal thoracic spinal cord and conus with small amount of dark
intramedullaryhemorrhage(blackarrowheads)distally.
ItisimportanttoconsidertheeffectoftheMRItechniqueontheappearance
of hemorrhage. FSE techniques which are widely used for spine imaging
becauseoftheadvantagesinacquisitiontimeandartifactreductionalsoreduce
thesusceptibilitychangesofblood.Thiscanmakebloodlessconspicuouswith
FSE techniques. GRE techniques, on the other hand, exaggerate magnetic
susceptibilitydifferencesbetweenbloodandsurroundingtissues.Althoughthis
canincreasesomeartifacts,
The differential diagnosis of hemorrhage within the spinal cord includes
trauma,whichwouldusuallybeobviousbyhistory,vascularmalformation,and
neoplasm. The presence of multiple areas of flow-void on MRI provides
additionalevidenceofahigh-flowvascularmalformation.Thesemaybepresent
withinthespinalcordinthe caseof intramedullaryAVMs(Figure6.60)oron
the surface of the spinal cord,or moreperipherally in the case of AV fistulas
(Figure 6.61). Tortuous draining veins are usually more conspicuous than the
feedingarteries.Superficialvessels, especially enlarged draining veins, can be
shownonmyelography.
Angiography plays an important role in the diagnosis of spinal vascular
malformations.Itdefinesthelocationandnumberoffeedingarteries,thesizeof
thecentralnidusinthecase of AVMs, and the locationofthedirectfistulous
connectioninfistulas (Figure6.61B); italsoshows theextentand directionof
venous drainage. Depending on the nature and location of the malformation,
endovascular therapy, such as embolization, can be used either alone or in
combination with surgery to treat the condition. In some cases of suspected
fistula,anexhaustivesearchofspinalarteriesmaybenecessary,fromthelowest
lumbosacral branches up through the vertebral, cervical, and external carotid
arteries.
FIGURE 6.60 Intramedullary spinal AVM in a 29-year-old man
presenting with hemiparesis and difficulty breathing. Sagittal T2weightedMRimageshowsdiffuseswellingandedemathroughoutthe
cervical spinal cord. Serpiginous linear flow-voids of the
intramedullaryAVMand itsdrainingvein extend fromthe C4 toC7
levels (small white arrows). The AVM was successfully
endovascularlyembolizedviaarightvertebralarteryapproach.
AVM,arteriovenousmalformation.
Cavernousmalformationscanoccurinthespinalcordaswellinthebrain,
andtheimagingcharacteristicsaresimilar.Typically,bloodproductsofvarying
age are present with a surrounding rim of dark T2-signal intensity from
hemosiderin. Larger lesions often have a reticulated appearance because they
contain pockets of methemoglobin, but small lesions may be seen only as
hemosiderin scars. Acute hemorrhage within a cavernous malformation has a
less-specificappearanceunlessthesurroundingolderbloodproductsarevisible.
SPINALTUMORS
AnestimatedoneinfourorfiveCNStumorsarelocatedinthespine(95–97).A
studybyKurland(98)estimatedtheincidenceofprimaryspinetumorstobe2.5
per100,000peopleperyear.MRIisthebestsinglemodalityforimagingspine
tumors(99). Its unsurpassed soft tissue differentiation(including the ability to
differentiate between CSF and neural tissue without the use of intrathecal
contrast),absence of beam-hardening artifact, and ability to image in multiple
planes make it clearly superior to CT, myelography, plain films, and
ultrasonographyinevaluatingepiduralandintraduraldisease.Forbonydisease
andprimarybonetumors,plainx-raysandCTarestillessential.
Technique
ThescreeningMRItechniqueweuseforthespineissagittalTR500–600,TE11
and FSE sagittal TR 3000–4000, TE 102 which allow us to obtain a quick
“myelogram”inabout4minutes.AxialFSE–T2-weightedimagesareobtained
in a stacked fashion, rather than using oblique axials through the disc spaces
only,whichcouldresultinmissingportionsofthetumor.Slicethicknessshould
bepreferably3mmonthesagittalimages,and4mmaxially,witha1-mmgap
tominimizepartial-volumeerrors.
T1-weightedgadolinium-enhanced images(insagittal andaxial planes) are
recommended to evaluate intradural tumors (100). Generally, intraduralextramedullary tumors enhance significantly; enhancement of intramedullary
tumorsismorevariable.However,inimagingvertebralmetastases,gadolinium
enhancementis notonlynot helpful, butmay be detrimental,because T1-dark
marrowmetastasesenhanceandbecomeisointensetonormalT1-brightmarrow,
unlessfat-saturationisemployed.
To minimizeCSFpulsation and othermotionartifacts, flowcompensation,
cardiac gating, respiratory gating, and phase-frequency direction swappingare
useful.However,inmanysystems,flowcompensationisnotyetavailablewith
FSE,andmotionartifactscanbeaproblemforthoseinexperiencedinreading
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