Radi Culo Path y

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    RADICULOPATHY

    -JOHN RIBU PARAMPILFinal Sem

    Fellowship In Ne!olo"i#al Reha$ili%a%ion

    Radiculopathy is a peripheral neurologic syndrome resulting

    from mechanical injury and chemical irritation of the

    spinal nerve roots. Mechanical injury to the nerve rootoccurs with compression, traction, or frictional forces.

    Chemical irritation occurs as a response to nerve root

    ischemia, vascular stasis, or nerve root exposure to inflammatory

    components released during tissue injury. The

    classic signs associated with radiculopathy include neck

    or back pain with spasm, mild to moderate peripheral

    numbness, shooting pain, or extremity weakness in the distribution

    of a nerve root. Radiculopathy is often seen in the

    posttrauma patient with intervertebral disk herniation.

    !irect compression of the nerve root is not necessary

    to produce radiculopathic symptoms. " radicular pattern

    of pain or deficit will fre#uently occur with any condition

    that produces inflammation in the nerve root area. $steophytic

    projections, degenerative disk disease, and lateral

    recess stenosis are common etiologies of radiculopathy in

    the degenerative spine.

    %ocali&ation of the neurologic deficit re#uires an

    understanding of the segmental innervation patterns in the

    body and extremities. There is considerable overlap of

    innervation from contiguous spinal levels to the skin, muscles,

    and skeleton, so that deficit locali&ation is sometimes

    difficult. $ccasionally, multiple nerve roots are involved,

    further complicating the locali&ation process. Confirmation

    of subtle or multilevel radiculopathy is based on the

    anatomic and functional correlatives between diagnostic

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    imaging and examination findings. Common correlative

    procedures include positive orthopedic tension or compression

    signs, neurologic indicators 'reflex changes,

    motor fatigue, sensory deficits, or pain patterns(, electrodiagnostic

    findings, and diagnostic imaging findings, including

    magnetic resonance 'MR(, computed tomography

    'CT(, and plain films. This chapter covers the relevant

    anatomy of the nerve root, the pathological processes, and

    the most common differential conditions seen with radiculopathy.

    SPINAL N&R'& ROOT ANATOMY

    REGIONAL CHARACTERISTICS

    The cervical nerve roots descend theequivalent of one neuromere (segmental cord level)beforehorizontally traversing their respective neural foramina.

    Thus, the C5C dis! "ill compress the C nerve root.This arrangement of nerve roots e#iting above the

    respectivenumbered vertebrae changes at the thoracic level asa result of the anatomic con$guration of the eightcervical nerve roots and seven cervical vertebrae

    %ensory input from peripheral and a#ial receptorsenters the dorsal aspect of the cord through acon$guration

    of nerve $bers called the dorsal rootlets. The cell bodiesof sensory a#ons are not found "ithin the gray matterofthe dorsal horn of the spinal cord& rather, they arelocated"ithin the dorsal root ganglia (') distal to the spinalcord "ithin the *+.

    The anterior and posterior rootlets merge -ust distal to

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    the ' to form the spinal nerve. 'orsal root $berscomprise the largest volume of the spinal nerve. t thepoint "here the convergence occurs, the sensory andmotor nerve components are no longer separate. Thecommingled rootlets inter"eave in a fascicular patternto form the mi#ed spinal nerve. The spinalnerve is usually only a fe" millimeters long and thendivides into the ventral and dorsal rami. *n the cervicaland lumbosacral spine, the ventral rami course anteriortothe spine and intermingle to form the ple#es and ma-ornerves of the e#tremitites. *n the thoracic spine, theventralrami form the intercostal nerves. The dorsal rami aremuchsmaller than the ventral rami. The dorsal rami branchintot"o or three branches that supply innervation to themuscles,ligaments, zygapophyseal -oints, and s!in overlying thespine.

    INTERVERTEBRAL FORAMEN ANATOMY

    The primary contents of the *+ include the spinalnerve,the ', connective tissue, fat, the radicular artery,theradicular vein, and t"o to four recurrent meningealnerves. This group of structures is referred to as thenerve root comple# .The nerve root typically occupiesappro#imately one quarter to one third of the volume ofthe *+. This can bereadily observed on sagittal / images. The nerve0to0*+ ratio "ill vary in the presence of pathologic osseous

    1 soft0tissue foraminal stenosis. 2erve root distensionor

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    enlargement "ill contribute to an abnormal nerve0to0*+ratio. The most common causes of an abnormal ratioinclude spondylosis and lateral dis! herniation. smallstudy of cervical *+ anatomy demonstratedthat nerve root compression occurred at the entrancezoneof the intervertebral foramina. *n the anterior aspect ofthe*+, compression of the nerve roots "as caused byprotrudingdiscs and osteophytes of the uncovertebral region,"hereas the superior articular process, the ligamentum3avum, and the periradicular $brous tissues a4ectedthenerve posteriorly.

    BLOOD SUPPLY OF THE SPINAL NERVE ROOT

    The t"o primary nutrient path"ays to the spinal nerveroot occur through vascular supply and di4usion fromtheC%.The blood supply to the vertebrae and the nerveroots arise from the segmental artery. The segmentalarterygives o4 a dorsal branch, "hich further branches tosupplythe vertebral arch, "ith an additional branch supplyingtheposterior vertebral body, and a smaller longitudinallyorientedarterial branch that supplies the nerve root. Theartery that supplies the posterior intervertebral bodyperforatesthe posterior longitudinal ligament. The longitudinal

    radicular artery provides several collateral radicular

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    arteries, "hich may lie anterior and posterior to thenerveroot, branching to provide perforating interfasciculararteries. The interfascicular arteries are redundant,oftencoiled in appearance, allo"ing for nerve root translationand stretch, "ithout compromising blood 3o" to thenerveroot. The interfascicular arteries supply precapillaryarterioles,"hich in turn supply intraneuronal capillaries.2erve roots receive their blood supply from both ends.

    The nerve root has adequate vasculature to prevent a"atershed zone in most cases of slo" onsetcompression&ho"ever, a large intradural or e#tradural lesion mayreducethe blood supply to the nerve root and inhibit C% 3o"to the nerve root sleeve, thus reducing nutrientdelivery.

    PATHOPHYSIOLOGY OF NERVE ROOT

    COMPRESSION

    nerve $ber begins physically deforming "hen thee#ternalpressure e#ceeds the intraneuronal hydrostaticpressure.lectrophysiologic conduction bloc! occurs at di4erentdegrees of e#ternal pressure, depending on the a#ondiameter. complete compression bloc! of theperipheralnerve occurs at the nerve trun! "hen appro#imately6570mm8g pressure is applied.%pinal nerve roots have demonstrated conduction bloc!

    at only 97 mm8g of pressure.:hen compression of the nerve root comple#

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    occurs, direct mechanical e4ects include conductionbloc!, interruption of a#onal 3o", and vascularsequelaethat include hypo#ia and metabolic byproductaccumulation,"hich compromise impulse propagation .2erve root compression contributes to a loss ofimpulse propagation via impairment of a#onaltransport. no#ia and hypo#ia may compromise fastand slo" anterogradea#onal transport as "ell as retrograde a#onal transport.#onal transport is required for the replenishmentof neurotransmitter comple#es. #onal transportmay be impaired in various pathologic conditions suchas ischemia,compression, infection, immunologic cascades, anda#onal degeneration and regeneration./oderate tosevere compression of a nerve root comple# mayinducedirect pathomechanical e4ects on the nerve $bers,suchas deformation of the nodes of anvier andinvaginationof the paranodal myelin sheaths.2eurologic function is highly dependent on theavailabilityof o#ygen. classic study of the frog nerve byrundfest sho"ed that a nerve can function under highe#ternal loads as long as there is a high concentrationofavailable o#ygen. ven at normal e#traneural pressurelevels, if the intraneural o#ygen level decreases, thenerve"ill become more susceptible to compressive loads.Conversely,

    even "ith an adequate systemic circulatory capacityto ma!e o#ygen available to the nerve root comple#,

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    focal vascular insu;ciency "ithin the comple# "illrenderit hypo#ic. The combination of vascular insu;ciencyanddiminished arterial o#ygen saturation "ill result ingreatersusceptibility to intraneural hypo#ia.2erve root compression often results in impairmentof intraneural blood 3o".

    The endoneurial vessels ofnerve roots, in particular the ', are more permeableto plasma proteins than the endoneurial vessels ofperipheralnerves.

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    beds and a brea!do"n of the capillary -unctions.This contributes to e#udation and e#travascularintraneuraledema formation.apid spinal nerve root compressionin3uences thedegree of clinical de$cit and recovery characteristics.apid0onset compression (bet"een 7.75 and 7.67 sec)causes a more pronounced e4ect than slo"0onsetcompression(over a ?70sec interval) "ith similar level pressures.apid0onset as "ell as sustained compressive insultresults in pronounced intraneural edema, impairedvascular 3o", conductive changes, and reducedcapacityfor nerve conduction recovery.This is an importantconsideration relative to intermittent and slo"0onsetcompression syndromes compared "ith rapid0onsetdis! herniationand spine in-uries after motor vehicle collisions.

    The magnitude of compression is also important inthe development of symptoms. Changes in spinal nerveroot conduction occur at pressures bet"een 65 and@5 mm8g. /otor conduction velocity recovers morerapidlythan sensory conduction "hen nerve root compressionpressures reach 677 to ?77 mm8g.%pinal nerve root compression can be present "ithoutovert symptoms.*n such cases, ho"ever, there isinvariablyan absence of trauma, but the presence of alongstandingcondition, such as osteophytosis or lateral recessstenosis,producing a slo"0onset of compression.

    SITES OF NERVE ROOT VULNERABILITY

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    The spine contains many osteoligamentous spaces thataccommodate and protect delicate neurovascularstructures.

    These spaces include the central vertebral canal, the*+, and the foramen transversarium. The morphologicrelationshipsof these osteoligamentous spaces di4er in variousintravertebral and intervertebral locations . Thespatial relationship of the nervous tissue to osseousandnonosseous elements of the spinal canal and the *+ isan important consideration in the development ofradicularcompression.

    The dynamic properties of these spaces arestrongly dependent on the anatomic characteristics andrelationships of the tissues ma!ing up their margins.

    Thedynamics of the intervertebral motion segment a4ecttherelative instantaneous size and volume of the intrinsicosteoligamentous canals and foramina.

    The volume of the *+ increases slightly during 3e#ionand decreases during e#tension. These changes aremore pronounced in the cervical spine. Aoo andcolleagues found that, in the neutral position and ate#tremes of 3e#ion and e#tension in the cervical spine,?7B of a#ial rotation produced a decrease in the meansizeof the foramen on the ipsilateral side and an increaseonthe contralateral side. Compared "ith themeasurement atneutral position, 97B of e#tension caused a 69.?decrease

    in the cervical foraminal dimensions, and 97B of 3e#ion

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    caused a 67. increase.This *+ narro"ing e#plainsone of the mechanismsinvolved in reproducing radicular pain "ith %purlingDsclinical maneuver. This orthopedic test is performed byturning the patientDs head to the side of complaint ande#tending it bac!"ard "ith gradual do"n"ard pressure. controlled do"n"ard blo" to the verte# of the headcanalso be used to reproduce symptoms.

    PATHOMECHANICS AFFECTING THE NERVE ROOT

    COMPLEX

    Ereig demonstrated that "hen the spine moves there isno signi$cant a#ial displacement of the spinal nerverootrelative to the canal. 'uring e#tension, ho"ever, thenerveroot increases in cross0sectional diameter, andconsequentlythere is a slac!ening and "idening of the nerveroot sleeve. 'uring for"ard 3e#ion, the dural sleevesandnerve roots "ere found to straighten gradually. Thisadaptabilityof the nerve roots greatly reduces friction bet"eenthe nerve roots and their ad-acent sheaths duringmovement.%evere $brotic adherence of the nerve roots andtheir perineural structures results in e#cessive tractionatthe nerve root attachment to the spinal cord.%ome of the signs and symptoms of radiculopathydevelop from irritation created by immobilization of thenerve root and dural sleeve. Eecause the dura mater ismechanosensitive, traction of the dura over a space0

    occupyinglesion, such as a herniated dis! or osteophyte, may

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    result in pain originating from the dura.

    The nerve root near a dis! herniation is sensitive tomechanical deformation,as observed in patients under epidural anesthesiaduring laminectomy and dis! e#cision.or patients "ith paresthesia secondary toneuroforaminalcompression, e#tension0induced narro"ing maymagnify symptoms. Concomitant adduction of thepainfularm and contralateral lateral 3e#ion may causestretchingof the nerve root "ithin the narro"ed foramen, thereby"orsening symptoms. Conversely, shoulder abductionandcervical 3e#ion may lessen symptoms.2erve root tension signs are common in cervical andlumbosacral radiculopathy. Cervical motions thatreduceforamen size also tend to elicit symptoms associated"ithneuropathology at the *+.*n lumbosacral radiculopathies, a positive straight legraise test is highly correlative to nerve rootcompression.

    SPINAL DEGENERATION AND RADICULOPATHY

    %pondylosis and posterolateral e#ostosis are commoncauses of *+ stenosis, lateral recess stenosis, orcentralspinal canal stenosis. outine radiographs or CT scansoften demonstrate dis!0spur comple#es or isolatedosteophytosis.>steophytic changes are more prevalent "ithin

    particular segmental levels of the spine. The levels ofthe

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    cervical spine most frequently a4ected are C5C andCC@. *n the thoracic spine, the TF level is mostvulnerable.*n the lumbar spine, the =G=5 and =5%6 levels arethe regions most often involved.The larger theosteophyticbar or pro-ection, the greater the potential for amass e4ect on neural structures and their blood supply.

    Theosteoarthritic spine is particularly vulnerable to trauma.

    The four general classi$cations of compressionsyndromesassociated "ith spondylosis are lateral or radicularsyndrome, medial or spinal syndrome, combinedmediallateral syndrome or myeloradiculopathy, and vascularsyndromes.=ateral recess stenosis has four subcategoriesH(6) lateral stenosis from hypertrophic enlargement ofthesuperior facet, (?) subarticular stenosis, (9) dynamicstenosis that occurs from increased intersegmentalmotionor clinical instability, and (G) $#ed stenosis that occurs"hen degeneration and stenosis are severe.>steophytosis is more prevalent "here %harpeyDs$bers attach to the vertebral body.This transitionalregion of bone and periosteum is usually severalmillimetersfrom the discovertebral -unction. *n this region,osteophytesgenerally begin as cla"li!e, horizontal, calci$cpro-ections o4 the vertebral body. s the spur develops,it begins to pro-ect in a vertical or inferior direction,forming

    an osseous bar as both vertebral margins fuse.

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    osteophytosis results in an e#pansile mass e4ect onneighboringneurovascular tissues.

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    or traction and cause pain syndromes.:hen $brotictissue compartmentalizesthe peridural space in the region of the descending ore#iting nerve root, the nerve root is immobilized andsusceptibleto compression from acute or recurrent dis!. pathology.*f a nerve root cannot move out of the path ofa mass e4ect, it is rendered more susceptible tocompressionand is also at ris! for traction0type in-uries becauseof loss of elasticity. The elastic limit of a normal nerveroot is appro#imately 65 of its resting length, and anystress beyond ?6 of its resting length may bringaboutcomplete failure./ild compressive lesions may onlyslightly decreasethe e#tent of movement bet"een the nerve root sleeveandnerve root. chronic compressive lesion may induce$brotic adherence and mechanical appro#imation thatseverely impairs nerve root movement.This results innerve root traction microin-uries against the pedicles,vertebralarches, andIor posterior vertebral body pro-ections.ibrosis of the nerve root sleeve results in cumulativemicroin-ury and a vicious cycle of scar0tissue formation.

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    %pinal trauma may lead to nerve root in-ury secondarytoavulsion, contusion, stretch, andIor compressive in-ury.2erve root contusion and stretch in-uries representtransientphysical pathomechanisms. Compressive insult maybe transient or may persist after the original trauma.%ignsof root compression may occur as a result of neuralin-uryany"here from the rootlets on the spinal cord to thespinalnerve in the distal portion of the *+. Common causes ofpersistent post0traumatic nerve root compressionincludehematoma, dis! herniation, displaced vertebralfracture,or vertebral dislocation. ny condition that distorts andnarro"s the dimensions of the *+ may result in nerveroot compromise. Jnilateral facet dislocation, vertebralbody fracture, and ligamentous disruption "ith a shiftofbony elements may produce transient, partial, orcompleteocclusion of the *+ or cause a traction in-ury of thenerveroot.

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    from reduced gliding capacity of the nerve duringvertebralmotion.

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    regarding the very de$nition of "hiplash, including itsmechanism of onset, prevalence, e#tent of relatedin-uries,and ho" to name this comple# trauma disorder.*n-uriesto the body result from rapid acceleration ordecelerationforces transmitted through the head, nec!, and body"ithin a fe" hundred milliseconds after vehicle impact.ear0end collisions are responsible for appro#imatelyF5 of reported "hiplash in-uries./+s are one of themost frequent causes of radiculopathy. lthough morethan one third of patients acutely complain ofparesthesiasfollo"ing an /+, neurogenic thoracic outlet syndromeis more commonly the cause than cervicalradiculopathy.%ymptoms associated "ith "hiplash can be classi$edin a loose time frame of acute and late "hiplashsyndromes./) orlateralizing pain symptoms. >blique pro-ections and3e#ione#tension plain $lms are essential for evaluating theposttraumaticpatient "ith mild radicular symptoms.

    INTERVERTEBRAL DISK HERNIATION AND

    RADICULOPATHY

    'is! herniation is "ell documented as one of the most

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    common etiologies of radiculopathy.or e#ample,in a study by /odic and colleagues,@? of patients"ith acute radiculopathy had a herniated nucleuspulposus.'irect correlation among the size of the dis! lesion,clinical presentation, and treatment outcome is notal"aysclear./any patients older than 7 years may have oneor more relatively asymptomatic herniations. *t shouldbenoted, ho"ever, that intermittent pain and loss offunctionalcapacity accompany virtually all relativelyasymptomaticherniations. normal intervertebral dis! has a high capacity foraccepting a#ial loads. /any studies have beenperformed on the behavior of the dis! under variablestressors. >ne of these sho"ed that the normalintervertebral dis! losesabout 7. mm of vertical height and bulgesappro#imately7.9G mm in a radial"ard direction under a compressivea#ial load of 6@77 2.This study determined that thedis!"ithstands a ma#imum compressive force of @777 2before failure& by comparison, the ma#imum forceneededto produce failure of the endplate "as ?577 2.These$ndings indicate that compression alone does notproducedis! prolapse in the e#perimentally prepared spine.dams and 8utton "ere able to e#perimentallyproducedis! herniation in a t"o0vertebrae specimen by

    applying

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    sudden compression to the specimen "ithsimultaneouslateral and full for"ard 3e#ion. The dis! prolapseoccurredon the open dis! "edge side opposite the side of lateral3e#ion. Clinically, dis! herniation is often seen after aliftingin-ury or motor vehicle accident in "hich lateral 3e#ionandfor"ard 3e#ion positions of the spine occur at the timeoftraumatic compression or shear. The classi$cation ofdis! herniations is often confusing and imprecise. Theterm disk herniation implies that a rupture or tear ofannular $bers occurs allo"ing the migrationof nuclear material beyond the vertebral margin. Thenuclear material may protrude out and cause adistentionof the outer annulus $brosis or rupture through theannulusand e#trude behind the posterior longitudinal ligament.dditionally, in cases "ith a greater degree ofe#trusion,the nuclear material may become separated from thedis!of origin and migrate into the epidural space or lateralrecess as a free fragment. The confusion in describingthepreviously mentioned lesions stems from the limitedresolutionof diagnostic imaging technology and the poorstandardization of terminology. This resolutioninadequacyis most problematic in con$rming small0to0moderatesized subannular herniations and con$rming "hether

    an e#trusion has separated from the dis! as a freefragment.

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    The second problem is the plethora of terms usedto describe a dis! herniation. %ome of the termsencounteredare dis! herniation, protrusion, e#trusion, nucleare#trusion, prolapse, bulging dis!, slipped dis!, ruptureddis!, and sequestered dis!.*t is classi$ed dis! lesions into four main groupsbased on their appearance on / imaging. They areannularbulge& protrusion (herniation)& e#trusion& and free dis!fragment (sequestration). These categories can beappliedto the description of dis! lesions throughout the spine.

    The ne#t consideration in describing a dis! lesion is"hether the herniation is contained by the annulus oruncontained and in a subligamentous position undertheposterior longitudinal ligament (

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    spinal cord is described as mild, moderate, and severe.4acement of the thecal sac, nerve root, or cord is alsoclinically signi$cant because of compression of thesurroundingvasculature and contact "ith the in3ammatoryinterface of discal material.

    SPONDYLOLISTHESIS AND RADICULOPATHY

    adiculopathy and spondylolisthesis are relativelyuncommon, as compared to nerve root compressionfromdis! herniation in the lumbar spine. 8o"ever, in casesofspondylotic spondylolisthesis, radiculopathy occurs in7to @7 of patients.%pondylolisthesis refers to theanteriordisplacement or listhesis of a vertebral body inrelationshipto the vertebral body immediately belo". The termlisthesis refers to slippage or displacement "ithoutreferenceto direction. %pondylolisthesis may occur "ithout adefectin the neural arch or secondary to a defect in the neuralarch.*f there is a defect in the neural arch, the termspondyloticspondylolisthesis should be applied. :ith an intactneuralarch, the term non0spondylotic spondylolisthesis shouldbe used.Cervical spondylolisthesis is rare, but "hen present, itis often found at the C level.

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    REFERENCES

    55. Eland, K.8., Disorders of the Cervical Spine: Diagnosisand Medical Management, ?nd ed.,

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    equina anatomy.