Chapter Introduction - Assetsassets.cambridge.org/97805218/89414/excerpt/... · A recent study of estimated healthcare ... often look for an easy answer and quick treatment ... sacrum

Chapter

1 Introduction

Spine-related disease is, both literally and figuratively,a painful proposition. Pain in the neck, mid back, andlow back is one of the most common medical condi-tions in adults. Other conditions affecting the spinedo not cause pain (e.g., myelopathy) but contribute tocost and disability. Low back pain alone is said to bethe most common cause of disability for personsunder the age of 45 in the United States; at any onetime, 1% of the U.S. population is chronically disabledand another 1% temporarily disabled by their backpain. In any given 3-month period, about 25% of U.S.adults report low back pain, and nearly 15% reportneck pain. About 2% of all physician office visitsrelate to low back pain alone. Low back problemsare reported to be the second-most common causefor absenteeism from work (after upper respiratorytract infections) and the most common cause foroffice visits to orthopedic surgeons, neurosurgeons,and occupational medicine physicians. Low backoperations are said to rank third among all surgicalprocedures in the United States. A recent study ofestimated healthcare expenditure for spine problemsamong U.S. adults when adjusted for inflation showeda 65% increase from 1997 to 2005; the total expendi-ture in 2005 was about $85 billion. The estimates donot include indirect costs such as lost wages, disabilitypayments, or “suffering.” Despite the increase inexpenditures, self-reported measures of mental health,physical functioning, and limitations at work, school,and in social situations were worse in 2005 than in1997. It is discouraging that we are spending more onspine problems in the United States but helping peopleless over time.

Scope of the problemThe scope of spine-related problems is reflected by thegreat number of different kinds of healthcare pro-viders who treat patients with cervical, thoracic, andlumbar spine conditions (see Table 1.1). In addition,there is a very long list of different treatments that

are given to patients for their spine conditions (seeTable 1.2).

Why do so many different kinds of providers treatspine patients with so many different therapies? Thereare four chief reasons. The first is that spine-relatedconditions, especially those due to spondylosis andthose associated with pain, are very common. Thesecond reason is that there are many different causesfor the same clinical presentation. Because of the manypotential causes for the same complaint and the lack ofaccurate diagnostic tests for the different conditions,the third reason is that providers have great difficultymaking an accurate diagnosis. For example, healthcareproviders can accurately diagnose only about 15% ofpatients with acute low back pain. The fourth and lastreason is that whether or not we can diagnose thepatient’s problem, we have great difficulty effectivelytreating their symptoms, in particular their pain, espe-cially if it is chronic, and pain is often the spinepatient’s chief complaint. Our inability to provide anaccurate diagnosis and specific, promptly effectivetreatment spawns confusion and a multitude of poten-tial therapies. The natural history for many patientsis one of gradual improvement or, at the least, stabilitywith fluctuation. As a result, any and all treatmentsmay seem to be effective. The spine patient is notcertain if they need a chiropractic manipulation or anoperation on their back, and providers have honestdisagreements about which course of treatment hasthe best outcome. The commonness of spine problemsand their chronicity attract large numbers of practi-tioners who typically favor one avenue of treatmentwhich may be of substantial help to a minority ofpatients or very modest benefit to a large number ofpatients. Patients desperately want to get better andoften look for an easy answer and quick treatmentand sometimes benefit from a very genuine placeboeffect. In truth, formany patients, the goal of treatmentof their back condition is to keep their symptomsunder control rather than to cure them. For manypatients with chronic spine problems, especially those 1

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involving pain, a combination of different therapiesis more likely to be helpful than searching for a singlemagic bullet.

EpidemiologyAccurate assessment of the incidence (the rate atwhich people develop a new symptom or disease overa specified time period) and prevalence (measureof the number of people in a population who have asymptom or disease at a particular time) for spinepain is difficult to ascertain because of different def-initions, collection methods, and populations studied.The following discussion relates mostly to spine andlimb pain due to spondylosis. By spondylosis wemean the degenerative wear and tear changes that

Table 1.1. Healthcare providers who treat spine-relatedproblems

Anesthesiologists

Chiropractors

Homeopaths

Internal medicine specialists

Massage therapists

Naprapaths

Neurologists

Neurosurgeons

Occupational medicine specialists

Occupational therapists

Orthopedic surgeons

Pain medicine specialists

Physical medicine and rehabilitation specialists

Physical therapists

Primary care providers (MDs, osteopaths, physician assistants,nurse practitioners)

Radiologists

Others

Table 1.2. Treatment options for back pain

Medications

Botulinum toxin injections

Disk injections

Epidural injections

Facet blocks

Herbal medicines

Homeopathy

Medications, both prescription and over-the-counter given byvarious routes and including analgesics, muscle relaxants, localanesthetics, and centrally acting drugs such as tricyclic agentsand serotonin-norepinephrine reuptake inhibitors

Nerve blocks

Trigger point injections

Surgical

Anterior discectomy and fusion with instrumentation

Anterior discectomy and fusion without instrumentation

Anterior fusion without discectomy

Anterior and posterior fusion

Discectomy with placement of artificial disk

Intrathecal pump placement for purposes of medicationadministration

Laminectomy with discectomy

Laminectomy without discectomy

Microdiscectomy

Posterior fusion with instrumentation

Posterior fusion without instrumentation

Radiofrequency lesioning of nerves especially the medialbranches of dorsal rami

Spinal cord stimulator placement

Physical treatments

Acupuncture

Bed rest

Connective tissue massage

Corsets

Crutches

Electrotherapy

Exercises

Magnet therapy

Massage

Multimodal rehabilitation

Stretching

Traction and distraction

Transcutaneous electrical nerve stimulation, high and lowfrequency

Ultrasound

Cognitive and behavioral

Back school

Behavioral therapy

Biofeedback

Holistic therapy

Meditation

Relaxation techniques

Chapter 1: Introduction

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affect the intervertebral disks and facet joints and theassociated pain arising from these structures and theadjacent bones, ligaments, and muscles of the spinalcolumn.

Cervical levelNeck pain is less common than low back pain and lessstudied. The lifetime prevalence of significant neckpain is about two-thirds to three-fourths of all indi-viduals, and about 20% of adults experience neck painover a 1-year period. About 5% of patients reportsignificant disability from their neck pain. Neck painoccurs in about 15%–30% of adolescents. The inci-dence and prevalence of neck pain increase fromadolescence until around the age of 50 and are slightlymore frequent in women than men. After the age of70, neck pain is about two-thirds as common aslow back pain. Although not as common as lumbarradiculopathy, the annual incidence of cervical radicu-lopathy is about 1 in 1000 per year. About 18% ofthe population visits a healthcare provider each yearfor neck pain. The frequency of neck pain decreasessomewhat after the age of 50.

Risk factors for neck pain include certain occupa-tions (e.g., dentists). Risk factors in the workplaceinclude time pressure demands, low co-worker sup-port, working in a seated position with the neckflexed, and working with arms above the shoulders.Degenerative joint and disk changes on cervical spineimaging are also probably associated with increasedrisk of neck pain and cervical radiculopathy.

One of the main risk factors for persisting neckpain is a whiplash-type injury. Lighter individualsmay be more susceptible to acute neck injury thanheavier people, and there is a positive correlation withheight where taller individuals are more susceptible toneck injury. Age does not seem to be a significantfactor in injury-provoked neck pain. Litigation andemotional issues may complicate neck pain followinginjury. Neck pain is relatively less common in childrenand adolescents.

Thoracic levelThoracic spine disease is less common than cervical,which in turn is less common than lumbar spinedisease. It is estimated that only 1% of all disk herni-ations affect the thoracic spine. While there are fewerdata, it is likely that many of the risk factors that leadto neck and low back pain are also associated withmid back pain. Thoracic pain commonly followstrauma from sports, leisure activities, and accidents.

Thoracic pain is relatively common in childhoodand fairly common in adolescence. Osteoporosis is amajor risk factor for vertebral compression fracturein the thoracic and lumbar spine.

Lumbar levelTwo-thirds to three-fourths of people will experiencelow back pain during their lifetime; half of Americansreport at least 1 day of low back pain in the pastyear; and many international surveys report a pointprevalence of low back pain of between 15% and 30%of the studied population. Sciatica is less commonwith a lifetime prevalence of 14%–40%, and lower yetfor significant sciatica secondary to disk herniation(4%–5% lifetime prevalence, higher in men thanwomen). Low back pain begins in adolescence as a ruleand gradually increases in frequency, then levels off,and may decline in the very elderly, over the age of 85.

In children and adolescents, the following factorshave been linked with a possible increase in the risk oflow back pain: genetic predisposition, lower socio-economic status, athletic activities, presence of scoli-osis, rapid growth, and increased height.

Risk factors for low back pain in adults include ahistory of low back pain in adolescence, lower socio-economic status, lower level of education, poor phys-ical conditioning, certain physical activities usuallyexperienced in work (heavy lifting, bending andtwisting, static work positions such as prolonged sit-ting or standing, exposure to whole body vibration),certain psychological and psychosocial work factors(monotony at work, job dissatisfaction, and poor rela-tions with co-workers), depression, obesity, cigarettesmoking, some congenital spine abnormalities (scoli-osis, transitional vertebra), and prior episodes of lowback pain as an adult. Low back pain is very commoneven in people without any of these risk factors.

Spinal anatomyThe vertebral columnThe vertebral column consists of seven cervical verte-brae, twelve thoracic vertebrae, five lumbar vertebrae,the sacrum which consists of five fused segments, andthe coccyx which is a small triangular bone consistingof three to five fused, rudimentary vertebrae (seeFigure 1.1). The mature vertebral column has severalcurves. The cervical spine from the first cervicalthrough the second thoracic vertebra is convex for-ward, the thoracic curve from the second to thetwelfth vertebra is convex backward, the lumbar


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curve from T12 to the lumbosacral junction is convexforward, and the sacrum and coccyx are concaveforward (and convex backward) and help to formthe posterior wall of the pelvis. The twelve paired ribsarticulate with the thoracic vertebrae, and the sacrumis wedged between the ilium of the innominate boneon each side.

The typical vertebra consists of an anterior part,the vertebral body, and a posterior arch enclosing thevertebral (or spinal) foramen. The foramina of theindividual vertebrae line up to form a vertebral (orspinal) canal which contains the spinal cord from theupper border of the atlas (the first cervical vertebra)usually to the lower end of the first lumbar vertebral

Figure 1.1. Anterior, posterior, and lateral views of the vertebral column showing the cervical, thoracic, and lumbar levels and thesacrum and coccyx.


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body in adults, and below that level, the vertebralcanal contains the bundle of lumbosacral nerve rootstermed the cauda equina (see Figure 1.2). In adults,the end of the spinal cord may be as high as thetwelfth thoracic vertebra or as low as the interspacebetween the second and third lumbar vertebrae. In thenewborn, the spinal cord ends at the level of the upperborder of the third lumbar vertebra. As we grow, thespine grows more rapidly than the spinal cord and,as a result, the spinal cord is at a higher level withinthe spine in the adult compared to the infant andchild. The usual vertebral body is roughly cylindricalbut flattened posteriorly. The vertebral bodies changein shape and size at different levels. From the secondcervical to the first sacral level, each vertebra is con-nected to the next by fibrocartilaginous complexestermed intervertebral disks between the vertebralbodies, synovial joints between the posterior arches,and various ligaments. The intervertebral disks lacksynovium, are termed symphyses, and do permitlimited motion.

The intervertebral disks are about the same size asthe apposing vertebral bodies and vary in thickness atdifferent spinal levels, being thicker at levels where thevertebral bodies are taller. The disks are thicker inthe front than in the back in the cervical and lumbarregions and thus contribute to the spinal curvatures atthese levels. Conversely, in the thoracic region, theintervertebral disks are fairly uniform in thickness,and the posterior convexity is due to the shape ofthe vertebral bodies, which are narrower in the frontthan in the back. When compared to their associatedvertebral bodies, the cervical and lumbar disks arerelatively thicker than the thoracic disks.

The intervertebral disks consist of an outer annu-lus fibrosus, which does receive some blood supplyfrom adjacent vessels, and an inner nucleus pulposuswhich is avascular. The annulus fibrosus is outwardlyconvex and heavily laminated. Within each lamina,the majority of the collagenous fibers run in parallel,but fibers in adjacent laminae run in different direc-tions such that overlapping fibers are at obliqueangles to one another (see Figure 1.3). The disks arecontained superiorly and inferiorly by cartilaginousplates which are firmly fixed to the bony end plates ofthe adjacent vertebral bodies.

The vertebral arch is composed of two short,round, rod-like bones called pedicles which projectbackward from the upper, dorsal surface of the verte-bral body. Each pedicle meets a broad, vertical lamina.The two laminae are angled posteriorly and medially

and meet in the midline behind the vertebral foramenwhere they fuse with the posteriorly projecting spinousprocess. The spinous processes vary considerably insize, shape, and direction throughout the spine. In thecervical spine, the spinous processes are rather shortand nearly horizontal, and usually have bifid tips.In the thoracic region, they are directed obliquelydownward, and in the lumbar region are nearly hori-zontal. At the junctions of the pedicles and laminae,there are paired superior and inferior articularprocesses termed zygapophyses. The superior articularprocess projects upward, and the inferior processdownward. Each process has a synovium-coveredarticular surface, and the superior process of onevertebra articulates with the inferior process of thevertebra above, forming a zygapophyseal or facet joint(see Figure 1.4). These paired facet joints permit alimited amount of movement while restricting exces-sive motion.

There are variably sized transverse processeswhich project laterally from the junction of eachpedicle and lamina. They are rather diminutive inthe cervical region and larger in the thoracolumbarspine. In the region of the transverse process of thecervical vertebrae is a foramen transversarium on eachside through which passes a vertebral artery. In thethoracic spine, these transverse processes articulatewith the ribs. The transverse processes and posteriorlyprojecting spinous processes serve as attachment sitesfor the strong paraspinal muscles.

Each pedicle has concave notches on its inferiorand superior surfaces. The inferior notch is larger anddeeper than the superior notch. The inferior notch ofthe pedicle of the vertebra above, the superior notchof the pedicle of the vertebra below, the intervertebraldisk and vertebral body anteriorly, and the zyga-pophyseal joint posteriorly form the intervertebralforamen. The intervertebral foramina, also calledneural foramina, are paired structures at each spinallevel through which the spinal nerves and bloodvessels travel (see Figure 1.4).

The anterior longitudinal ligament extends alongthe anterior surfaces of the vertebral bodies and inter-vertebral disks; the posterior longitudinal ligament iswithin the vertebral canal and runs along the pos-terior aspect of the vertebral bodies and intervertebraldisks. Running along the posterior aspect of the ver-tebral canal and connecting the laminae of adjacentvertebrae are the ligamenta flava. The ligamentumnuchae in the neck, the supraspinous ligament inthe thoracolumbar spine, and the interspinous


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Figure 1.2. Sagittal view of the vertebral (spinal) canal showing the various segments of the spinal cord and spinal nerves which exit throughthe intervertebral foramina. The spinal cord ends at about the level of the L1 vertebral body, and below that is a bundle of nerve rootscalled the cauda equina which leave the vertebral canal in pairs at the appropriate level.


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ligaments connect adjacent spinous processes. Theseligaments also connect with deep paraspinal muscles.

The first and second cervical vertebrae, the atlasand axis respectively, merit special mention. The atlaslacks a typical vertebral body and consists of a ring-type structure. It supports the skull. Interlocking withthe anterior aspect of the vertebral foramen at thelevel of the atlas is a small, hard cylindrical bonyprocess, called the dens or odontoid process, whichprojects upward from the axis (the second cervicalvertebra). The front of the dens forms a small jointwith the back of the anterior arch of the atlas. Thedens is kept in place by a transverse ligament. Theatlas has two rather large lateral masses, and the upperaspect has a superior articular facet on each sidewhich articulates with an occipital condyle on thebottom of the skull on each side. The articulationsbetween the skull and atlas and between the atlas andaxis facilitate rotational and nodding movements ofthe head and upper neck (see Figure 1.5). There is nointervertebral disk between the atlas and axis.

The lower five cervical vertebrae (C3–C7) have aunique lateral connection to the vertebra above. Theupper surface of each of these vertebrae is concavefrom side to side, and this concavity is formed in largepart by lateral uncinate processes on each side of theupper surface of C3–C7 (see Figure 1.6). The bonyprotuberance which extends upward along the lateralaspect of the upper surface of each of these vertebrae

interfaces with a beveled edge of the cervical vertebraabove and helps to prevent posterolateral disk pro-trusions. It is unclear whether this cleft is a fibro-cartilaginous connection or a true synovial joint, butthese articulations are termed uncovertebral joints orthe joints of Luschka. Whether or not there is a truejoint present, these “joints” can degenerate and hyper-trophy and, given their posterolateral location, theyare in a position to compress exiting cervical nerveroots (see Figure 1.6).

The combination of the intervertebral disk system,the ligaments which attach the vertebrae to oneanother, the facet joints, and the muscles which attachthe vertebrae and adjacent structures permits amodest amount of movement between any twoadjoining vertebrae. The intervertebral disks whichbind the vertebrae together allow movement betweenadjoining vertebrae by virtue of their compressibilityand slight ability to rotate. The summation of mul-tiple small movements at multiple spinal levels gives

Figure 1.3. Diagram of intervertebral disk showing the outerannulus fibrosus and the inner nucleus pulposus. The annulusfibrosus has multiple layers or laminae. Within each lamina, the fibersrun in parallel and usually at an oblique angle. Fibers in adjacentlaminae run in different directions, helping to limit movement andstrengthen the attachment between adjacent vertebrae. Individuallaminae are much smaller than is shown in this diagram.

Figure 1.4. Lateral (lower) and mid sagittal (upper) views of thevertebral column show the component parts and relationships.The apposition of the synovium-covered articular surfaces of theinferior and superior articular processes form the paired facet(zygapophyseal) joints found at each spinal level. The intervertebral(neural) foramina through which the spinal nerves exit the vertebralforamen are formed by the undersurface of the pedicle above,the vertebra and intervertebral disk in front, the facet jointposteriorly, and the upper surface of the pedicle of the next lowervertebra below.


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rise to a fairly substantial range of motion for thevertebral column as a whole. Greater movement ispossible in the cervical and lumbar regions becausethe disks are thicker at these levels.

The spinal cord is not round but oval, being widerthan it is deep, more so in the cervical levels thanelsewhere. The spinal cord and exiting nerve rootsare covered by three membranes or meninges whichare, from outside in, the dura mater, the arachnoidmater, and the pia mater (see Figure 1.7). The duramater extends from the foramen magnum to the

second sacral vertebral level and has tubular pro-longations along the nerve roots and spinal nervesas they pass through the intervertebral foramina toleave the spine. The space between the dura and theperiosteum and ligaments within the vertebral canalcontains a plexus of veins, loose fat, and areolar tissue.Local anesthetics, infection, and tumors can spreadthrough this epidural space. Beneath the dura materis the arachnoid, a delicate membrane that is looselyattached to the dura and envelops entering andexiting nerves and blood vessels. Between the dura

Figure 1.5. The image on the left shows the relationship between the atlas (the first cervical vertebra or C1) and the axis (the second cervicalvertebra or C2) from above and behind. The three images on the right show separate views of the atlas and axis. The atlas articulates withthe base of the skull above and with the axis below. The dens (odontoid process) is a peg which extends up from the axis and articulates withthe back of the anterior arch of the atlas. A ligament behind the dens helps to keep it in place. There is no intervertebral disk between theatlas and axis.


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and the arachnoid mater is a potential subdural spacewhich also ends at the second sacral level. The piamater covers the spinal cord and also invests the nerveroots. Between the arachnoid and pia mater is thesubarachnoid space which contains spinal fluid. Thearachnoid and dura can expand such as when spinalfluid pressure is increased. The ability to expand candampen transmitted spikes in spinal fluid pressuresuch as accompany the pulse-driven production ofcerebrospinal fluid in the choroid plexus within theventricles intracranially.

There are two areas of enlargement of the spinalcord: the cervical enlargement which extends fromabout the third cervical to the second thoracic spinalcord segment, and the somewhat smaller lumbarenlargement from the first lumbar to the third sacralspinal cord segment. The cervical and lumbarenlargements relate to the increased number of nervecells and nerve fibers required for innervation of the

upper and lower limbs respectively. The cervical nerveroots travel downward only slightly before leavingthe spinal canal and never more than one vertebrallevel from the corresponding spinal segment. Thus,the cervical spinal cord enlargement is only slightlyhigher than the corresponding vertebral levels. How-ever, because the spinal cord typically ends at aboutthe level of the first lumbar vertebral body, the lumbarenlargement lies at the ninth through twelfth thoracicvertebral levels, and, as a result, the lumbosacral nerveroots descend for some distance within the vertebralcanal before exiting. As noted above, the spinal cordusually ends at the lower end of the first vertebralbody but can be as high as the twelfth thoracic verte-bra or as low as the disk below the second lumbarvertebra (see Figure 1.2).

The termination of the spinal cord is called theconus medullaris. Below the conus medullaris is abundle of nerve roots termed the cauda equina (horse’stail) which descend within the lumbosacral spinalcanal to exit in pairs through the appropriate inter-vertebral foramina. Within the cauda equina the sacralsegments are located most medially and the firstexiting, upper lumbar segments are located more lat-erally. From the bottom of the conus medullaris thereis a connective tissue filament, the filum terminale,which extends all the way to the bottom of the vertebralcanal into the sacrum and attaches to the coccyx.

Detailed spinal cord anatomySuperimposing an H over an oval can separate ageneric spinal cord level into the following sections(see Figure 1.8). The upper (posterior or dorsal) armsof the H surround paired funiculi or white columnswhich transmit ascending first-order sensory infor-mation dealing mostly with proprioception (vibra-tion, joint precision sense, pressure, and touch). Theascending fibers in these columns are uncrossed andmost have their cell bodies in the ipsilateral spinal(dorsal root) ganglia. Each of the paired dorsal fun-iculi is further divided into a lateral fasciculus cunea-tus and a medial fasciculus gracilis. The fasciculuscuneatus carries fibers from the upper thoracic andcervical nerves, and the fasciculus gracilis carriesnerve fibers from the lumbosacral and lower thoracicsegments. Sacral level nerve fibers are medial tolumbar, which are medial to thoracic, which aremedial to cervical level fibers. The ascending sensorynerves in the two fasciculi synapse in the nucleuscuneatus and the nucleus gracilis in the medullaoblongata after which the second-order neurons

Figure 1.6. The C3–C7 vertebrae have uncinate processes whichare upward projections of the lateral edges of the vertebral body oneach side. Each uncinate process contacts the disk and beveledinferolateral surface of the vertebra immediately above. Theseso-called uncovertebral joints (joints of Luschka) can degenerate andhypertrophy. Such hypertrophy can cause cervical nerve rootimpingement, especially if it occurs posteriorly.


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decussate and ascend to the thalamus in the mediallemniscus. Lateral to the uprights of the H are twolarge lateral funiculi or white columns (one on eachside) which include both ascending and descendingtracts. The ascending tracts include anterior and pos-terior spinocerebellar tracts, the lateral spinothalamictract which is the predominant pathway for pain andtemperature sensation, and several other lesser tracts.The most important descending tract is the lateralcorticospinal tract which carries motor signals to thespinal cord. The lateral corticospinal tract containsmostly fibers from the contralateral hemispherewhich have crossed in the lower ventral medullaoblongata (pyramidal decussation). The lateral cortico-spinal and lateral spinothalamic tracts are organizedsuch that fibers serving the lower limbs are moreperipheral within the spinal cord than those servingthe upper extremities. Between the two legs of theH are small anterior funiculi or white columns whichcontain a small but variable descending anteriorcorticospinal tract which has motor function and isuncrossed, and an ascending anterior spinothalamictract which is close to the lateral spinothalamic tract.

The H itself has thick lower (anterior or ventral)legs and somewhat thinner (posterior or dorsal) arms

which contain mostly gray matter. These are termedanterior or ventral and posterior or dorsal graycolumns or horns. In the thoracic spinal cord, thereis a lateral gray column which projects from each sideof the H at the level of the crossbar of the H. Theanterior gray columns contain important motorneurons which control movement and muscle tone.They are comparatively broad and short and do notreach the anterior surface of the spinal cord. Thelateral gray columns in the thoracic and upper lumbarspinal cord segments contain preganglionic sympa-thetic nerve cells. In the sacral cord there are similarparasympathetic gray columns that do not have aclear lateral projection. The posterior gray columnsconsist of several layers of nerve cells chiefly relatedto sensory function. Nerve cells in the posterior graycolumns receive input from neurons in the ipsilateraldorsal root ganglia and elsewhere within the spinalcord. After ascending one or two segments ipsilater-ally, much of the output from the posterior graycolumns crosses to the opposite side through a whitecommissure in the crossbar of the H. These second-order sensory fibers ascend in the contralateral anter-ior spinothalamic tract (touch and pressure morethan pain sensation) and the contralateral lateral

Figure 1.7. The meninges are shown covering the spinal cord, nerve roots, and spinal nerves. The pia mater (red) is closely attached to thespinal cord and nerve roots. The pia is separated from the arachnoid mater (purple) by spinal fluid. The arachnoid layer is loosely attachedto the dura mater. The dura mater (teal) has tubular extensions or sleeves lined with arachnoid which cover the nerve roots and spinalnerves as they pass through the intervertebral foramina. The dura becomes continuous with the epineurium of the spinal nerves.


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Chapter Introduction - Assetsassets.cambridge.org/97805218/89414/excerpt/... · A recent study of estimated healthcare ... often look for an easy answer and quick treatment ... sacrum