Anatomy, Imaging, and Common Pain-Generating Degenerative Pathologies of the Spine

1. Anatomy, Imaging, and Common Pain-Generating Degenerative Pathologies of the Spine R2 김현석

2. ANTOMY • Osseous spinal column 7 cervical, 12 thoracic, 5 lumbar and 5 fused sacral segments C1 (atlas) : anterior arch, posterior arch, and paired lateral masses * C2 (axis) : bony projection which articulate with C1 (odontoid process or dens) C3 ~ C7 : dorsolateral margin of the superior endplate (uncinate process) • typical cervical, thoracic, and lumbar vertebra : anterior body, paired pedicles, articular pillars and laminae, and a single dorsal midline spinous process

3. Spinous process – serve as a attachment point for the posterior ligamentous structures • Pedicle, articular pillars, and lamina - serve to protect the spinal cord and nerve roots • Transverse process in the mid-cervical : vertebral artery가 통과하는 osseous transverse foramina을 형성 in the thoracic and lumbar spine : spinal column을 protect하고 stabilize시키는 muscle이 붙는 지점을 제공함.

6. Joints • atlanto-occipital : occipital condyle ~ lateral mass of C1 • Atlantoaxial : ventral dens ~ dorsal surface of C1 anterior arch • Uncovertebral : dorsolateral margin of the superior endplate of the C3~C7 • Costovertebra and Costotransverse : rib ~ vertebral body or transverse process of the thoracic spine • zygoapophyseal (facet) joints : the most prevalent joints , superior and inferior articular process *

7. Transverse foramen, Intervertebral foramen, and Nerve roots • Contents of Transverse foramen – vertebral artery, vertebral venous plexus, sympathetic chain • Intervertebral foramen bounded by the pedicle, vertebral body, disc and superior articular process * - Adamkiewicz artery : supply to the lower two-thirds of the spinal cord , enter the spinal canal via an intervertebral foramen -> transforaminal or periganglionic intervention시 damage에 주의 • Intervertebral Discs : thicker in the cervical and lumbar region and thicker anteriorly than posteriorly - axial loading 의 absorb, flexibility제공 - nucleus pulposus, annulus fibrosis, cartilaginous endplate

9. - nucleus pulposus : type II collagen, hyaluronic acid, glycoaminoglycan * - annulus fibrosis : outer dense circumferential fibrous band and inner fibrocartilagenous layer • Ligament – stability, flexion, extension, rotation - ALL, PLL, ligamentum flavum, interspinous ligament, supraspinous ligament - ALL : vertebral body and intervertebral disc - PLL : annulus fibrosis but does not contact the posterior vertebral margin - ligamentum flavum : laminar segment 사이로 extend, spinal canal의 dorsolateral margin을 define - interspinous ligament, supraspinous lig. : spinous process 사이를 연결

11. IMAGING OVERVIEW • Conventional Radiographs (X-rays) - quick, inexpensive, easy to perform, execellent spatial resolution - important information : alignment, structure, mineralization - unstable spine : dynamic, weight bearing upright flextion and extension view - foraminal stenosis, spondylolysis : oblique projection - vertebra alignment evaluate : lateral projection 에서 three longitudinal curve ( anterior and posterior spinal line = anterior and posterior longitudinal ligament 의 course , spinolaminar line = ligamentum flavum 의 course ) 과 pedicle의 관계에서 rotational malalignment가 보여짐. *

12. Myelography and postmyelography CT scan - non-ionic, water-soluble, radiographically dense iodinated contrast material을 subarachnoid space에 넣어서 spinal canal의 content를 evaluate하는 radiographic technique. - disc abnormality, ligament thickening, hypertrophic facet degenerative change, spinal stenosis, nerve root impingement, redundant thickened nerve root, arachnoiditis can be detected - postmyelography CT scan : better definition of anatomic relationship of the contents of the spinal canal to the surrounding structure - invasiveness and non-invasive imaging tool(CT, MRI)의 availability로 인해 사용이 줄어듬. - Cx. : positional headache(m/c), contrast-related seizure, infection *

14. Computer-assisted tomography (CAT or CT scan) - osseous structure의 definition에 가장 우수. - x-ray beam의 diffenrential attenuation에 기초한 것으로, bone, ligament, disc material, CSF 등의 radiographic density차이가 있으므로, disc herniation, ligamentous disorder등을 진단하는데 사용될 수 있다. - spinal rods, transpedicular screw, laminar wire/hook, intervertebral cage등의 surgical metallic implant에 의한 artifact가 생김. - children, pregnant female, other young adult에서 더 sensitive하므로 적절한 care하에 시행되야 함.

15. Magnetic resonance imaging(MRI) - hydrogen atom(proton)의 amount and state에 기초하여 tissue를 localize하기 위해 gradient field와 radiofrequency를 사용 - radiation은 없지만, electrical and metal implant에 의한 risk와 fetus에 대한 unknown risk가 있다. - soft tissue contrast resolution이 우수하여 spinal disorder의 diagnostic imaging modality로 유용함. - bone marrow, muscle, ligament, disc material, nerve root등의 tissue type의 구분이 우수하고, extradural, intradural, extramedullary, intramedullary pathology의 구분이 정확함. - medullary bone evaluation에도 우수하여 marrow edema나 marrow replacement를 일으키는 osseous condition을 알 수 있으나, dense cortical bone, sclerotic lesion, osteophyte에 대한 정확성은 CT에 비해 낮다.

16. - standard MRI protocol : sagittal and axial with T1- and T2- weighted sequence - T1 high signal intensity – fat (fatty bone marrow, subcu. Fat) low signal intensity – fluid (CSF, bone marrow edema, normal nucleus pulposus) * - STIR(short-tau inversion recovery): fat depressed T2-weighted sequence로 fluid에 sensitive하여 traumatic injury, malignancy, infection등에서 edema를 detect하는데 유용 - GRE(gradient recalled echo) T2-weighted imaging은 blood product and calcium에 sensitive하여 spinal trauma에 유용 - infection, multiple sclerosis, intramedullary neoplasm, metastatic disease, postoperative scarring evaluation – IV gadolinium contrast material administration sagittal and axial T1-weighted image

17. - C/Ix. : cardiac pacemaker, metallic foreign body, metallic surgical implant(ex. cerebral aneurysm clip and heart valve) - MRI시행시 m/c problem은 claustrophobia이고 sedation에 의해overcome되지만, 마취과가 필요한 경우도 있음.

18. DEGERATIVE DISC DISEASE • Overview • Acute or chronic back pain을 일으키는 uncertain etiology, aging에 의한 pathologic process • Conventional radiographic finding : disc space narrowing, vacuum disc, endplate sclerosis, ostephyte formation • MRI : excellent soft tissue contrast and multiplanar capability -> disc degeneration evaluate의 modality of choice • Disc dehydration and Narrowing • T1 : hydrated and nonhydrated disc : homogenous T2 : disc의 water content가 bright signal -> central bright nucleus pulposus and dark annular fibrosis

20. Degenertive disease -> disc desiccation -> disc signal감소 -> intradiscal gas accumulation -> proton 이 없어서 T1- and T2-에서 hypointense sequense (vacuum disc phenomenon) • Disc height는 normal or diminished이어서 disc degeneration의 indicator가 못되나, decreased height는 intervertebral foramina size의 감소이고 nerve root의 compression과 관련됨. • Annular fissure / tears -On T2-weighted image, linear hyperintense signal • Three type of annular degeneration – concentric fissuring, transverse tear, radial tear - concentric fissuring : collagen fiber delamination – T2에서 disc margin에 parellel한 high signal intensity

22. - transverse tear : vertebral body ring apophyses와 Sharpey’s fiber의 junction에서 small foci of T2 hyperintensity - radial tear : primary failure of the annulus and full-thickness disruption of the annulus * outer third of annulus fibrosis and PLL are innervated by nociceptive nerve ending -> discogenic back pain • Subchondral marrow changes - vertebral end plate degenerative disease의 three type : T1- and T2- weighted signal charateristic에 따라 - Type I change : T1감소, T2증가 – vascularized marrow - Type II change : T1증가, T2증가 or isointense – bone marrow의 fatty replacement - Type III change : T1, T2 both low signal – subchondral sclerosis

23. DISC HERNIATION • Overview - disc herniation evaluation : imaging modality of choice is MRI (due to its excellent soft tissue resolution) • Disc contour • Disc herniation : Intervertebral disc space를 넘어선 localized disc material displacement • Circumferential bulge : vertebral body’s ring apophysis edge의 50~100%를 넘어서는 disc material bulging - 25% 넘지않는 localized herniated disc material은 “focal” , 25~50% 는 “broad-based”라는 term - vertebral endplate로 focal disc herniation : Schmorl’s node

24. Disc margin과 herniated disc fragment의 shape에 따라 protrusion and extrusion으로 describe. - protrusion : base가 wider than apex - extrusion : base에서 width보다 herniated fragment가 더 away - sequestated or free-fragment disc herniation : parent disc에서 completely seperated • Disc migration in the cranial or caudal direction is best evaluated in the sagittal plane - 주로 posterior extrusion은 PLL 내에 있고, inferiorly migrate됨

26. Disc herniation position • Disc herniation의 위치는 anatomic landmark를 사용하여 describe. - extraforaminal zone : pedicle의 lateral aspect의 parasagittal line을 넘어서는 zone. - lateral recess : pedicle의 medial border를 따르는 area, disc level and superior vertebral endplate의 이하 • On sagittal image - suprapedicular level : pedicle의 바로 위 ~ superior end plate - pedicle level : pedicle의 superior and inferior edge사이 - infrapedicle level : pedicle의 inferior edge아래 ~ inferior end plate • Herniated disc의 위치에 따라 compress하는 nerve root결정 - in the Cervical spine : central or paramedian herniation -> descending nerve root ex) C3-4 paramedian disc extrusion -> C5 nerve root

27. foraminal disc -> 같은 level의 nerve root ex) C3-4 foraminal disc -> C4 nerve root - in the thoracic and lumbar spine(existing root is associated with superior level) : paramedian disc T3-4 -> T4 root foraminal disc T3-4 -> T3 root • Neural compression의 정도는 herniated disc에 의한 normally round or oval configuration의 spinal cord, nerve root, root ganglion의 변화의 정도에 따라 graded. - mild compression : normal diameter의 75~99% 유지 - moderate : 50~74%, severe : <50%

29. FACET JOINT • Overview - low back pain의 source가 되지만, clinically primary cause인지 감별하기는 어렵다. - facet joint syndrome : degenerative facet joint와 해부학적으로 관련된 focal or referred pain을 말하는 controversial diagnosis • Imaging - facet joint arthropathy : hypertrophic osteophytic overgrowth, subchondral sclerosis, bone marrow edema, joint space narrowing/widening, joint stiffness, periarticular soft tissue edema… - osteophytosis and subchondral sclerosis : T1- and T2- 에서 hypointense - bone marrow and periarticular soft tissue edema : T1에서 hypointense and T2-에서 hyperintense보임. - joint space widening : joint space의 effusion, T2-hyperintense

30. - facet joint arthropathy는 intrinsic abnormality로 pain일으킬 수 있고, lateral recess에서 descending nerve root나 intervertebral foramen에서 existing nerve root를 compression하여 pain만듬. - facet joint osteoarthritis : CT scanning으로 정확히 진단. cervical spine에서 애매한 sclerotic change and osteophyte는 MRI보다 더 쉽게 진단.

31. INTRASPINAL FACET CYSTS • Overview - intraspinal facet cyst : facet joint 에서 origin한 smooth border의 fluid-filled rounded structure - lining of cyst : synovial epithelial cell(synovial cyst) or fibrous wall surrounding myxoid material(ganglion cyst) - radiologically both type이 같게 보이고, treatment도 감압술로 같아서 type의 감별이 임상적으로 중요치 않다. * - synovial cyst(통칭)는 거의 항상 degenerated facet joint에서 생기고, joint의 dorsal surface에서 나온 것은 soft tissue로 protruding하지만 neural structure를 compression하지는 않고, ventral surface에서 생기고 intervertebral joint, lateral recess, lateral spinal canal로 protruding한 것은 location에 따라 existing nerve root(in the foramen) or descending nerve root(in the lateral recess or lateral spinal canal)를 compression 함 - nociceptive synovial lining -> intrinsically painful할 수도 있음.

32. Imaging - on CT, uncomplicated synovial cyst : isodense to CSF, occasionally has a calcified wall proteinaceous material or blood within cyst : isodense to muscle or ligament - mass effect or stenosis related to intraspinal or foaminal synovial cyst : CT myelography * - MRI : T1- and T2- prolongation, isodense to CSF proteinaceous or hemorrhagic material : T1 hyperintensity : wall은 fibrous material로 구성, calcified - juxta-articular cyst와 disc extrusion D/Dx. : short term follow up MRI에서 disc fragment는 resolution되고, cyst는 no change - treatment : conservative management, percutaneous decompression, sugical removal -> successful outcome

33. SPINAL STENOSIS • Overview - CT는 bony abnormality, bulging or herniated disc로 인한 spinal stenosis를 효과적으로 evaluation - MRI : GRE T2 image in the cervical spine and conventional or fast spin echo T2-weighted image in the T-L spine -> canal내에서 CSF flow로 인한 artifact없이 central canal and intervertebral foramen을 evaluation할 수 있다. - surgical hardware있는 경우엔, conventional T2-weighted image로 artifact를 최소화 할 수 있다. • Grading spinal stenosis - AP dimension에 의해 mild stenosis는 normal level의 spinal canal의 AP diameter의 75~99%유지, moderate and severe는 50~74%, <50% - intervertebral foramen의 AP and craniocaudal dimension으로 evaluate

34. - mild foraminal stenosis는 bulging disc or hypertrophic superior articular process에 의해 foramen의 inferior part의 narrowing - moderate narrowing은 nerve root를 따르는 fat이 줄어듬. - severe stenosis은 no fat, nerve root clearly compressed + 이런 변화는 sagittal T1-weighted sequence에서 most sensitive

35. SPONDYLOLYSIS AND SPONDYLOLISTHESIS • Overview - spondylolysis : articular pillar의 pars intra-articularis에서의 discontinuity, 원인은 불확실하지만, chronic microtrauma와 관련된걸로 보임. - bilateral pars fracture있으면, vertebral body는 앞으로 slip -> spondylolisthesis - mild and moderate slip : canal이 not narrow, paradoxically enlarge - severe spondylolisthesis : spinal canal의 AP diameter elongate and sagittal plane에서 spinal canal narrowing시킴. • Imaging - CT : test of choice to diagnose, pars의 sclerosis and fracture - MRI : 유사한 소견이지만, actual fracture를 파악하기 어려운 때가 있다.

36. - MRI는 foraminal stenosis와 nerve root compression은 잘 보임 pars fracture부위에서의 cartilagenous overgrowth 보임. - plain film은 oblique projection에서 spondylolisthesis를 쉽게 진단할 수 있고, bone detail과 MRI exam의 관계보는데도 효과적