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atheroscleroticvasculardisease,andmayaffectsmaller intramedullary arterial
brancheswithresultantsmallinfarcts,inwhichcasetheclinicalmanifestations
mayvary dependingupontheir sizeand location. Fibrocartilaginousembolism
(Figures3.5and3.6),whichmaybeobservedoneitherthearterialorthevenous
sideofthespinalcirculation,tendstooccurineitheryoungadulthoodorinlate
middle life. A sizable proportion of affected subjects have a history of minor
traumaticinjuryorofheavylifting.Ithasbeensuggestedthataxialstress,such
as that which is associated with heavy lifting, may result in herniation of
fibrocartilaginous disc material into the bone marrow (Schmorl’s nodes) and
hence into the venous (and, if pressure is high enough, into the arterial)
circulation (6,7). As is the case with atheromatous embolism, the neurologic
manifestations will vary according to the size and location of the ischemic
lesionsproduced.
Another form of spinal vascular embolism is that associated with
decompression,eitherfromascendingtooquicklyafteradeepdiveorfromloss
of aircraft cabin pressure. Approximately half of those afflicted have a patent
foramen ovale (8). For reasons not well understood, when neurological
manifestations appear, spinal cord signs and symptoms tend to predominate,
particularlythosereferabletothecervicothoracicregion.Inthosesubjectswho
have been examined postmortem there are multiple small infarcts within the
spinal gray and white matter. The pathogenesis of these lesions is poorly
understood, but one group of observers noted, in an experimental model of
decompression,thepresenceofgasbubbleswithinthespinalepiduralveins(9).
FIGURE3.1 Spinal cord atS5 in a subject who becameparaplegic
afteran episodeof cardiacarrestand whodied 9weekslater.Tissue
necrosisislimitedalmostexclusivelytothegraymatter.
SpinalVenousInfarction
Spinalvenous thromboembolic occlusion is distinctly uncommon and tends to
occurinhypercoagulable states.Epidural,leptomeningeal,orintraparenchymal
veins may be affected. Venous infarction of the spinal cord may be either
hemorrhagic or nonhemorrhagic. Hemorrhagic infarction is characterized by
sudden onset with back pain, rapid progression, and short survival, whereas
nonhemorrhagicinfarctionismoreinsidiousandprotracted,withoutbackpain,
andwithrelativelylongersurvival(10).
SpinalVascularMalformations
Arteriovenousmalformations,whichpresumablyareofvascularembryological
origin,mayinvolveeitheraportionofortheentirecross-sectionalextentofthe
spinal cord. They typically become manifest acutely (due to hemorrhage) in
youngadults.Pathologically,theparenchymaofthespinalcordisreplacedbya
network of abnormal, heavily collagenized vessels of greatly varying mural
thicknessthatcannotbeidentifiedaseitherarterialorvenousinnature.
FIGURE3.2Ischemicatrophyof theventralspinalcordatT12in a
manwhohadbecomeparaplegic4½yearsearlierfollowingresection
oftheleftninthandtenthribsforrepairofathoracoabdominalaortic
aneurysm.
FIGURE 3.3 Cavitary necrosis of the tissue adjoining the anterior
medianfissureatspinalL4inamanwhodevelopedsuddenparaplegia
followingatheromatousembolismtotheanteriorspinalarteryatspinal
T10.
Arteriovenous fistulas (AVFs) are acquired lesions that typically become
manifest in middle life as slowly progressive lower extremity weakness. The
fistulous communication is most frequently seen embedded within the dura
ensheathinganerverootinthethoracolumbarregion,althoughmyelopathymay
occasionally be associated with fistulas at other sites, such as the pelvic or
retroperitoneal region or within the cranial cavity.Pathologically,the walls of
leptomeningealveinsandofthespinalintraparenchymalvenocapillarynetwork
aregreatly thickened, an indicationofvenous hypertension and impairmentof
venousdrainageofthespinalcord.Thisresultsinavenocongestivemyelopathy,
inwhichthecross-sectionalareaofthespinalcordmaybereducedtoone-half
orlessofitsnormalsize(Figure3.7).Thepathologicalpictureisidenticaltothat
described by Foix and Alajouanine under the Heading of “Subacute Necrotic
Myelitis,” and it is generally accepted that the so-called Foix–Alajouanine
syndromerepresentsnothingmorethanthemyelopathyassociatedwithaspinal
duralAVF(3).
FIGURE3.4Atheromatousembolismtoadorsolateralspinalarterial
branch,fromthesamepatientdescribedinFigure3.3.
FIGURE3.5Coagulativenecrosiswithinthelateralcorticospinaltract
followingfibrocartilaginousembolismtothespinalcirculation.
Surfer’sMyelopathy
Surfer’s myelopathy is a recently recognized condition that affects novice
surfers,typicallyhealthymalesintheir20s,who,duringorshortlyafterhaving
maintained prolonged hyperextended positions, develop back pain progressing
relativelyrapidly into a complete or incomplete myelopathy. Since its original
descriptionin2004 (11),it has becomemore widely recognized, and a recent
review(12) refers to 64 cases in the published literature. Sensory loss affects
both pain and temperature perception and posterior column sensation in twothirdsofsubjects,andinapproximatelyhalf,thereiscompletemotorloss(ASIA
ImpairmentScale[AIS]AorB).Thosewhorecovertendtodosowithin24to
72 hours. In patients with AIS A lesions, there is typically no recovery. T2-
weighted MRI most often demonstrates longitudinally extensive, centrally
placedsignalhyperintensities(13).
Althoughtherearenodetaileddescriptionsofspinalcordhistopathology,the
clinical and imaging characteristics are strongly suggestive of an ischemic
process.Theoriginalreportsuggestedthepossibilityofwatershedinfarction,but
thereis controversyasto precisely whatconstitutes a watershedinfarct within
thespinalcord. Furthermore,watershed infarctioninthebraintypically occurs
in a setting of profound systemiccirculatoryimpairment or markedly reduced
aorticperfusion,neitherofwhichhasbeendescribedinassociationwithsurfer’s
myelopathy. The suggestion has been made that fibrocartilaginous embolism
resulting from prolonged hyperextension may alsoplaya role in pathogenesis
(14).
FIGURE 3.6 Same patient as in Figure 3.5 showing fibrocartilage
emboluswithinaspinalvein.
FIGURE3.7SpinalcordatT12inapatientwithanuntreateddural
AVFshowingischemicatrophyandmarkedthickeningofthewallsof
spinalleptomeningealveins.
TRAUMATICINJURYTOTHESPINALCORD
PatternsofInjury
Thevariedclinicalexpressionsoftraumaticspinalcordinjury(SCI)reflectthe
distributionand mechanism of damage(3).Theanteriorspinalcordsyndrome
(Figure3.8)istypicallytheresultofhyperflexioninjuryandischaracterizedby
spastic weakness and loss of pain and temperature perception with relative
preservation of posterior column (proprioceptive) sensation. The central cord
syndrome(Figure3.9)isordinarilyaconsequenceofhyperextensioninjury(e.g.,
adivingaccident)andischaracterizedbyspasticweakness(greaterintheupper
extremities), loss of pain and temperature perception, and a variable loss of
posterior column sensation. The Brown–Séquard syndrome classically results
froma stab wound and is characterized by ipsilateral motor weakness (due to
damagetotheipsilaterallateralcorticospinaltract),contralaterallossofpainand
temperature perception (due to damage to the ipsilateral lateral spinothalamic
tract, which receives fibers from the opposite side), and ipsilateral loss of
posterior column sensation (due to damage to the ipsilateral posterior column
fibers). The complete spinal cord syndrome results from crush injury or
transection and is characterized by spastic weakness and by complete sensory
lossbelowthelevelofthelesion.
FIGURE3.8VentrallypredominantdamagetothespinalcordatL2in
asubjectwhohadbecomeparaplegicfollowingahyperflexioninjury
inamotorvehicleaccident44yearsearlier.
Lesionsdevelopingdirectlyasaresultoftheprimaryinjury(e.g.,laceration
or crush) are typically segmental and hemorrhagic. Damage developing
secondarilycanbesubdividedintoearlyanddelayedcomplications.Within8to
24hours,thewhite matterandtheascendinganddescendinglongspinaltracts
containedthereinshowmassiveedemaanddiminishedvascularperfusion.Other
factors that contribute to the spread of tissue damage includes the release of
excitotoxicneurotransmitters, calcium, and potassium ion shifts; generation of
oxygenfreeradicals;andactivationofthearachidonicacidcascade(3).
Weeks,months,oryearsaftertheinjury,anumberofadditionalmorphologic
alterations may appear. Traumatic neuroma formation (Figure 3.9) may be
massiveattheprimarysiteofinjuryandispresumedtorepresentsproutingfrom
dorsalspinalafferents.Visibleevidenceofwalleriandegenerationofascending
tracts above and of descending tracts below the level of the lesion does not
appear until approximately 6 to 8 weeks have elapsed. Chronic adhesive
arachnoidopathyisaninvariableconsequenceoftraumaticSCI.
Themostdramaticlateconsequenceoftraumaticinjurywithtetheringofthe
spinalcord is delayed traumatic syringomyelia,in which, usually afterseveral
yearshaveelapsed,oneormorecavitiesappearwithinthespinalcordaboveor
below(withoutnecessarily beingdirectlycontiguouswith)theinjurysite (15).
Episodic elevation of venous back-pressure, such as that which may occur
during Valsalva maneuvers or while coughing, sneezing, or straining at stool,
maycauseupwardordownwardextensionofthesecavitieswithinanimmobile
spinal cord. This may in turn cause progression of the neurologic deficit (see
Chapter 33). Pathologically the cavity, which is typically asymmetrical and
sometimesmultiple, contains noepitheliallining andisbordered by a zoneof
gliosis(Figure3.10).
FIGURE3.9CentrallypredominantdamagetothespinalcordatC7
ina manwhohad become quadriplegicfollowing a divinginjury27
yearsearlier.Notethelargetraumaticneuroma.
FIGURE3.10Delayedtraumaticsyringomyeliawithinthespinalcord
at C8 in a man who developed C5 quadriplegia after chiropractic
manipulation-associated vertebral osteomyelitis. Note the adhesive
arachnoidopathycharacterizedbyproliferation ofcollagen withinthe
subarachnoidcompartment.
MYELOPATHYDUETOVERTEBRALCOLUMN
DISEASE
CervicalSpondylosis
Themostimportantvertebralcolumndiseaseleadingtostructuraldamagetothe
spinalcordiscervicalspondylosis.Withadvancingage,theintervertebraldiscs
losewaterandelasticity,especiallywherespinemobilityisgreatest(i.e.,atthe
C5–C6andC6–C7 interspaces),and adjoiningvertebralbodiesmaycome into
direct contact with each other, leading to the formation of bone spurs or
osteophytes. When these bone spurs form along the posterior margins of the
vertebral bodies they may project into the spinal canal, thereby narrowing it.
Narrowing of the spinal canal in this manner will not necessarily lead to
symptomatic neurologic dysfunction in and of itself, but it may increase an
individual’s vulnerability to spinal cord damagewhenthereisa superimposed
stressfulevent,suchashyperextensionoftheneckafterarear-endmotorvehicle
collision.
Thepatternof spinalcord damagethatdevelopswillvary accordingto the
locationof the bone spurs. For example, if they are laterallyplaced they may
encroachupontheneuralforamina,resultinginaradiculopathy.Atypicalpattern
of damage that is seen relatively commonly is associated with a posteriorly
directedbonespurthatissituated nearthemidline. Inthissituation,thespinal
cord,asseenintransversesection,assumesanovoidshapewitha “butterfly”
distributionofdamagethataffectsbothlateralcorticospinaltracts(withresultant
spastic lower extremity weakness and Babinski signs), the lateral spinal gray
matter,and theventralportionsoftheposteriorcolumns(Figure3.11)(3).The
mechanism by which this pattern of damage develops is unclear, but there is
imaging evidence to suggest that buckling of the ligamenta flava during
hyperextensionresultsinaxonaldisruption(16).
FIGURE3.11CervicalspondyloticmyelopathyatspinalC5showing
pallorofmyelinstainingwithinthelateraland,toalesserdegree,the
dorsalwhitematter.Notetheovoidcontourofthespinalcord.
RheumatoidDisease
Myelopathymaydevelopinsubjectswithrheumatoiddiseaseeitherasaresult
ofdirectinvolvementofthespinalcordoritscoveringsbythediseaseprocess
(i.e., in the form of vasculitis or of rheumatoid nodule formation) or, more
commonly, as a result of disease of the cervical spine (17). Vertebral column
disease is typically the result of subluxation, most frequently atlantoaxial but
sometimessubaxial.Atlantoaxialsubluxationmayoccureitherinaforwardorin
anupwarddirection;intheformercircumstance,thespinalcordmaybepushed
againsttheanteriorwallofthespinalcanal,resultinginatriangularspinalcord
contourasseenintransversesections,withacentralpatternofdamage(Figure
3.12).
FIGURE 3.12 Spinal cord at C1 in a man with rheumatoid disease
whobecamequadriplegicafter C1/C2 vertebral subluxation showing
flattening of the ventral surface and damage within both gray and
whitematter.
DEGENERATIVEANDDEMYELINATIVESPINAL
CORDDISEASE
Friedreich’sAtaxia
Friedreich’sataxiaisthemostcommonformofautosomalrecessiveataxia.Itis
duetoamutationofageneonchromosome9q13thatleadstomarkedlyreduced
expressionofaprotein(frataxin)thatappearstoparticipateintheregulationof
mitochondrialironefflux(18).Inthevastmajorityofinstances,thereisaGAA
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