20 -NONNEOPLASTIC DISORDERS of SPINE and SPINAL CORD .

C H A P T E R Nonneoplastic Disorders of the Spine and Spinal Cord Infection Spondylitis and Diskitis Epidural and Subdural Infections Meningitis, Myelitis, and Cord Abscess Demyelinating Diseases Multiple Sclerosis Acute Transverse Myelopathy Miscellaneous Myelopathies Vascular Diseases Normal Vascular Anatomy Aneurysms Vascular Malformations Infarction Degenerative Diseases Normal Aging and Disk Degeneration Spondylosis, Arthrosis, and Spinal Stenosis Disk Bulges and Disk Herniation Normal Postoperative Spine "Failed Back" Syndromes Back Pain in Children Trauma Mechanisms of Spine Injury Osseous Spine Injury Patterns Soft Tissue Injuries In this chapter we consider benign acquired disorders of the spine and spinal cord, beginning INFECTION Spondylitis and Diskitis Early diagnosis is crucial in the management spine infections because delayed treatment can lead to increased morbidity and mortality.1,2 We begin this section by focussing on pyogenic and tuberculous spondylitis and diskitis, then turn our attention to epidural abscess and meningitis We conclude by discussing spinal cord abscesses (see box) Pyogenic spondylitis Infective spondylitis involves one or more of the extradural components of the spine It most often affects the vertebral bodies (osteomyelitis), but the posterior elements, intervertebral disks, epidural spaces, and paraspinous soft tissues can also be affected.3 Etiology and pathology A spectrum of bacterial, fungal, or parasitic organisms can cause infectious spondylitis Staphylococcus aureus is the most common pyogenic organism in adults, accounting for approximately 60% of infections; Enterobacter, a frequent genitourinary pathogen, accounts for 30%.4 Other common organisms include Escherichia coli, Salmonella, Pseudomonas aeruginosa, and Klebsiella pneumoniae.3 Chapter 20 Spine Infections Spondylitis > diskitis > epidural abscess >> cord abscess Most common cause of infectious spondylitis: S aureus Incidence rising (drug abuse, immunocompromised patients) Usually hematogenous (arterial, not Batson's plexus) Initial site Children: disk space first, then vertebrae Adults: subchondral vertebral body, then disk space Imaging Plain films normal early in disease course "Hot" (hyperintense) disk on T2-weighted MR Disk, adjacent bone often enhance Soft tissue mass common; ±epidural abscess, meningitis gens Systemic bacteremia, typically from a cutaneous, urinary tract or pulmonary infection, is the most common source Hematogenous spread typically occurs via arteries; the vertebral veins (Batson's plexus) play a comparatively limited role.5 Contiguous spread from an adjacent soft-tissue infection (e.g., paraspinous muscle or retropharyngeal abscess) is less common Direct contamination from open wounds, penetrating foreign bodies, diagnostic procedures, or surgery is rare In adults, infection begins in the sulochondral portion of the vertebral body, then spreads to the disk space and further along the vertebral body in a subligamentous fashion.5 In children, the intervertebral disk is richly vascularized and may serve as the initial site, whereas, in adults, disk infection is invariably caused by direct spread from contiguous vertebrae or soft tissues.3,4 Incidence, age, and gender Infectious spondylitis is uncommon, accounting for only 5% of all cases of pyogenic osteomyelitis Bacterial vertebral osteomyelitis typically affects adults in the 6th and 7th decades Immunocompromised patients and drug abusers are at increased risk There has been a major increase in reported incidence of spinal osteomyelitis in the last decade.3,6 There is a slight male predominance.3,4 Location Although pyogenic spondylitis can occur anywhere, the lumbar spine is the most common site, followed by the thoracic spine The sacrum and cervical spine are less commonly involved.4 Clinical presentation and natural history Symptoms vary widely Pain and malaise are common The patient may be either febrile or afebrile The erythrocyte sedimentation rate and white blood cell Nonneoplastic Disorders of the Spine and Spinal Cord 821 are often mildly elevated.4 Neurologic deficit and signs of cord compression may occur, with infection spread into the epidural space.4 Imaging findings Plain film radiographs are usually normal for the first to 10 days following symptom onset Abnormalities such as disk-space narrowing and end plate erosions are often subtle and not detected until relatively late in the disease process (Fig 20-1, A) Radionuclide bone scans are sensitive but nonspecific indicators of early disease.6 CT scans may also be normal early in the disease course Disk-space narrowing, cortical bone loss, and paraspinous soft tissue mass can be seen but are usually present only after moderately severe changes have occurred.6 MR findings are characteristic Tl-weighted sequences typically show a narrowed disk space and low signal intensity in the adjacent vertebral bodies that reflects increased extracellular fluid within the marrow.3,6 Subligamentous or epidural soft tissue masses and cortical bone erosion are common (Fig 20-1, B) Postcontrast studies show enhancement of the infected disk space and osteomyelitic bone (Fig 20-1, B) Paraspinous abscess, epidural extension, and associated meningeal inflammation are easily delineated on these studies (Fig 20-2).1,2 T2-weighted sequences show high signal in the affected disk space and vertebral bodies The "nuclear cleft" that is typically seen as an area of decreased signal intensity in the middle of the disk is effaced.3 Differential diagnosis The differential diagnosis of pyogenic spondylitis includes granulomatous spondylitis (see subsequent discussion), intervertebral osteochondrosis, calcium pyrophosphate crystal deposition disease, and axial neuroarthropathy In rare circumstances, metastatic disease can cause changes that are virtually identical to those of infection.7 Occasionally, severe degenerative disk disease is accompanied by secondary spine changes that can also simulate infection.3 Granulomatous spondylitis and miscellaneous spondylitides Etiology and pathology Granulomatous reaction occurs with a spectrum of bacterial, viral, parasitic, and fungal infections, as well as some tumors, autoimmune diseases, and idiopathic disorders.3 Granulomatous spondylitis is most commonly caused by Mycobacterium tuberculosis (Fig 20-3) Other organisms that may be implicated include bacilli of the Brucella genus, typically B melitensis (Fig 20-4).8 Fungal spondylitis is uncommon but is increasing with the rising numbers of immunocompromised and debilitated patients.3 Some fungal infections such as blastomycosis and aspergillosis are indistinguishable from tuberculous 822 PART FIVE Spine and Spinal Cord Fig 20-1 Lateral plain film radiograph (A) and sagittal postcontrast T1-weighted MR scan (B) in a 44-year-old woman drug abuser show classic findings of vertebral osteomyelitis The C5-C6 interspace is narrowed, and the end plates of the vertebral bodies appear irregular (large arrow) The marrow enhances (B, small arrows), consistent with osteomyelitis Subligamentous prevertebral soft tissue mass (B, open arrows) and epidural phlegmon (B, curved arrow) are also present Subluxation secondary to ligamentous laxity is seen ers such as actinomycosis, cryptococcosis, and coccidiodomycosis cause patchy vertebral body destruction or sclerosis with relative disk sparing.3 Parasitic spondylitis is rare For example, only 1% of echinococcus infections involve bone; when they do, the spine is the common site.3 Incidence, age, and gender Although pulmonary tuberculosis has decreased, the incidence of bone and joint tuberculosis remains unchanged.9 Tuberculous spondylitis now accounts for 6% of new extrapulmonary tuberculosis cases.10 In developing countries, tuberculous spondylitis is a disease of children, whereas in North America and Europe it is most prevalent in middle-aged adults The mean age at diagnosis is between 40 and 45 years compared with pyogenic osteomyelitis where the peak incidence is in the sixth to seventh decades.9 Debilitation, immunosuppression, alcoholism, and drug addiction are predisposing conditions.3 There is no gender predilection Location The lower dorsal and lumbar spine are affected in nearly three quarters of all cases of tuberculous spondylitis; the cervical spine is an uncommon site.11 Nearly 90% of cases have at least two affected vertebral bodies; 50% have three or more levels affected.9,11 "Skip" lesions are common.3 Para- spinous abscesses are present in 55% to 95% of cases.9 Occasionally, tuberculous spondylitis affects only one vertebral body, sparing the adjacent disk Tuberculosis can affect only part of a vertebral body The transverse processes and posterior elements are sometimes also involved.3 Brucellar spondylitis can be focal or diffuse In focal disease, osteomyelitis is localized to the anterior aspect of an end plate Lower lumbar involvement is common in brucellar spondylitis, whereas tuberculous spondylitis is most common in the lower thoracic and upper lumbar spine.8 Clinical presentation and natural history Tuberculous spondylitis is typically more indolent than pyogenic osteomyelitis Onset is often insidious, and symptom duration frequently ranges from months to years.9 Untreated patients develop progressive vertebral collapse with anterior wedging and gibbus formation.10 Imaging findings Plain film findings in tuberculous spondylitis include bone destruction in nearly all cases and associated soft tissue masses in most Reactive sclerosis is not a feature on initial presentation in Caucasian patients but early sclerosis is seen in approximately 50% of non-Caucasian patients Loss of disk height is present in more than three quarters of Chapter 20 Nonneoplastic Disorders of the Spine and Spinal Cord Fig 20-2 A 65-year-old man with an infected IV site had a 10-day history of fever and chills followed by an increasing sensory deficit that proceeded to paraplegia A, Postcontrast sagittal T1-weighted MR scan shows a frank epidural abscess with enhancing borders (large arrows) and central low density nidus (open arrows) B, Sagittal T2-weighted sequence shows the abscess (open arrows) Focal high signal (solid arrows) at the cervicomedullary junction is probably secondary myelitis Loculated pus was removed at surgery Fig 20-3 Sagittal (A) and axial (B) contrast-enhanced T1-weighted MR scans in a 32year-old man with tuberculous discitis, spondylitis, and psoas abscesses The affected disk and end plates enhance intensely and homogeneously (A, arrows) Multiloculated psoas abscesses are present (B, arrows) 823 824 PART FIVE Spine and Spinal Cord Fig 20-4 Axial CECT scan in a 52-year-old man shows bilateral psoas abscesses (large arrows) Bone windows (not shown) disclosed osteomyelitis Note irregular anterior, lateral end plates (small arrows) Brucella abscesses were drained at surgery patients; vertebral body fusion eventually occurs in most cases.10 CT scans characteristically show extensive bony destruction and large paraspinous abscesses that are relatively disproportionate to the amount of bone destruction Epidural extension and subligamentous spread are also frequently present.3,9 MR scans invariably show loss of cortical definition of the affected vertebrae However, affected vertebrae are often at least partially maintained in pyogenic spondylitis (Fig 20-3, C) T1WI often shows infection spread beneath the longitudinal ligaments to involve adjacent vertebral bodies.9 The disks are sometimes relatively spared, particularly in relationship to the degree of bone destruction The posterior elements are commonly involved.9 Differential diagnosis The major differential diagnosis of tuberculous spondylitis is pyogenic vertebral osteomyelitis or other spondylitides such as brucellosis, actinomycosis, and hydatid disease (Fig 20-4) Tumor is also a diagnostic consideration when a paraspinal mass is associated with bone destruction.9 there is thickened inflamed tissue with granulomatous material and imbedded microabscesses This represents a "phlegmonous" stage (see Fig 20-1, B).13 In the second stage a collection of liquid pus forms a frank abscess (Fig 20-5, see Fig 20-2).12 Incidence, age, and gender Spinal epidural abscesses are uncommon, representing approximately one case per 10,000 hospital admissions in tertiary institutions.13 However, the incidence of SEA is now increasing significantly.14 All ages are affected; the mean age is 50 to 55 years.14,15 There is a moderate male predominance in reported cases of SEA.12-15 Location All areas of the spine are affected SEAs are often extensive; in one third of cases the infection extends over more than six vertebral segments.12 Concomitant diskitis or osteomyelitis is seen in 80%.12 Clinical presentation and natural history Fever and localized tenderness are common early Symptoms but symptoms are often nonspecific.13 Predisposing conditions include diabetes mellitus, intravenous drug abuse, multiple medical illnesses, and trauma.14 If left untreated, severe neurologic deficits, and death may occur.13 EpiduraI and Subdural Infections Epidural abscess Etiology and pathology Spinal epidural abscess (SEA) typically results from direct hematogenous seeding of the epidural space from a cutaneous, pulmonary, or urinary tract source.5 Staphylococcus aureus is by far the most common organism responsible for spine infections of all types.12 Two basic stages are observed in SEA Initially, Imaging findings Plain spine radiographs may disclose osteomyelitis and disk space narrowing (see Fig 20-1, A) Myelography or CT-myelography demonstrates an extradural soft tissue mass with blockage of normal CSF flow.14 MR scans typically show an extradural, soft tissue mass that is iso- to hypointense compared to spinal Chapter 20 Nonneoplastic Disorders of the Spine and Spinal Cord 825 Fig 20-5 A, Sagittal postcontrast T1-weighted MR scans in this 37-year-old drug abuser show a large, enhancing epidural phlegmon (arrows) Cephalad extension into the cisterna magna is present B, Axial scans show thin enhancing rims (arrows) surrounding hypointense fluid collections Phlegmon and frank abscesses were found at surgery cord on T1WI and hyperintense on proton density and T2-weighted sequences (see Fig 20-2, B).13 Coexisting low signal changes in adjacent vertebral bodies are often seen on T1WI with high signal intensity in the intervertebral disks and vertebral bodies on T1weighted sequences.14 Three patterns are observed following contrast administration Diffuse homogeneous or slightly heterogeneous enhancement is seen in 70% of cases (see Fig 20-1, B).14 This most likely represents the phleg- monous stage of SEA The second most frequent finding is a thick or thin enhancing rim that surrounds a liquefied low signal pus collection, seen in 40% of cases (see Fig 20-2, A) This represents a frank necrotic abscess.14 In some cases, a combination of both patterns is observed (see Fig 20-5).13 Subdural abscess Spinal subdural abscesses (SSA) are rare The relative paucity of reported cases of SSA compared to intracranial subdural abscesses 826 PART FIVE Spine and Spinal Cord has been ascribed to absence of venous sinuses in the spine, the wide epidural space acting as a "filter," and the centripetal direction of spinal blood flow.16 Clinical presentation is nonspecific; symptoms may mimic those of acute transverse myelitis, spinal epidural abscess, epidural hematoma, pyogenic spondylitis, and neoplasm.16 Imaging studies disclose an intraspinal space-occupying mass, often without features that would localize the lesion to the subdural compartment.16 Meningitis, Myelitis, and Cord Abscess Intradural spinal inflammatory disease includes meningitis and myelitis The diagnosis of uncomplicated meningitis is typically established by lumbar puncture, whereas imaging studies may be more helpful in diagnosis myelitis Meningitis Spinal meningitis can be caused by bacterial (pyogenic, granulomatous), fungal, parasitic, or viral organisms.3 Pyogenic leptomeningitis is the most common bacterial infection of the spinal axis The majority of these cases occur as a manifestation of cerebral meningitis.3 Granulomatous, pyogenic, and aseptic meningitides are all seen as contrast-enhancing tissue that surrounds the spinal cord and nerve roots.17 Three patterns are seen,17 as follows: Delicate, smooth, linear enhancement outlining the cord, nerve roots, or meninges (Fig 20-6) Discrete nodular foci on the surface of these structures Diffusely thickened soft tissue that appears as an intradural filling defect There is no correlation between enhancement pattern and disease severity or specific responsible organism.18 Myelitis The term myelitis should be restricted to inflammatory diseases of the spinal cord, whereas "myelopathy" is a more general term that is applied to cord dysfunction from noninflammatory sources (e.g., spondylitic or compressive myelopathy, radiation myelopathy).18 Several infectious agents can cause myelitis Viral infections typically affect the gray matter Herpes, coxsackie, and polio viruses are the most common agents, although HIV-related myelitis is increasing in frequency.18 Epidural abscess and chronic meningeal infections such as tuberculosis and fungal meningitis mail also cause a secondary myelitis (see Fig 20-2, B).5,17 Post-infectious and post-vaccinal myelopathies also occur (see subsequent discussion) Imaging findings are typically nonspecific and resemble other noninfectious inflammatory and demy- Fig 20-6 Sagittal postcontrast T1-weighted MR scan on this 26-year-old woman with low-grade fever following lumbar surgery shows diffusely thickened, enhancing meninges (arrows) CSF showed mildly elevated protein, mild pleocytosis, and no organisms Probable aseptic meningitis elinating disorders (see subsequent discussion) Focal or diffuse increased intramedullary signal on T2weighted MR scans, with or without mass effect, is typical Enhancement following contrast administration can be seen in some cases.17 Intramedullary abscess In contrast to brain abscess, frank pyogenic spinal cord abscesses are extremely rare The few reported cases may represent focal venous infarcts that are complicated by bacterial colonization.3 DEMYELINATING DISEASES Multiple Sclerosis Etiology and pathology The general etiology a pathology of multiple sclerosis (MS) are detailed in Chapter 17 Spinal cord plaques are an almost universal autopsy finding in patients with MS; in some cases the spinal cord is the earliest affected site.19 Plaques occur preferentially in the dorsolateral cord and not respect boundaries between specific tracts or between gray and white matter (Fig 20-7).19 Chapter 20 Nonneoplastic Disorders of the Spine and Spinal Cord Fig 20-7 Axial T2-weighted MR scans in a 46-year-old woman with long-standing multiple sclerosis and cervical myelopathy show multifocal white and gray matter high signal intensity foci (arrows) Fig 20-8 This 43-year-old woman with a 3-month history of optic neuritis and right arm weakness developed sudden onset of rapidly progressive sensory deficit and upper extremity weakness Pre(A) and postcontrast (B) sagittal T1-weighted MR scans show diffuse cervical cord enlargement that extends from C2 to C7 and enhances moderately (arrows) The patient developed severe bilateral optic atrophy and quadriparesis Follow-up scans years later (not shown) demonstrated diffuse cord atrophy Neuromyelitis optica (Devic syndrome) 827 828 PART FIVE Spine and Spinal Cord Incidence, age, and gender MS is a worldwide disease, although the greatest prevalence is in temperate zones such as the United States and Canada, Great Britain, and northern Europe Disease onset is typically between 15 and 50 years, with a peak in the third and fourth decades There is a distinct female predominance, particularly in children and adolescents with MS.20 Location Spinal cord plaques can be found at any segment In later stages, plaques are evenly distributed; in early disease there is a distinct predilection for the cervical spinal cord.19 An MS variant, Devic disease (also called neuromyelitis optica), is a rapidly progressive fulminant demyelination that is restricted to the optic nerves and spinal cord (Fig 20-8).20a Imaging findings Spinal MR is not required for confirmation when a definite diagnosis of MS has been made on clinical grounds However, in patients with isolated myelopathy and a clinical suspicion of demyelinating disease, brain MR is recommended as the first screening imaging study.21 If such patients have a normal brain scan, MR examination of the spinal cord is appropriate (Fig 20-8) The most common finding on T2-weighted MR scans is one or more elongated, poorly marginated, hyperintense intramedullary lesions, particularly if focal or generalized cord atrophy is identified on T1WI.21 Acute demyelinating lesions may have mass effect and enhance following contrast administration (Figs 20-8 and 20-9).20 Acute Transverse Myelopathy Acute transverse myelopathy (ATM) is sometimes termed acute transverse myelitis In its most dramatic form, ATM is characterized by an acutely developing, rapidly progressing lesion that affects both halves o the cord ATM is not actually a true disease but a clinical syndrome with diverse causes (see box).22 Etiology and pathology Several neuropathological processes may give rise to ATM Some cases develop with active infection; others occur as a post infectious demyelinating disorder (acute disseminated encephalomyelitis, or ADEM) (Fig 20-10) Acute Transverse Myelopathy Etiology Acute infection Post-infection Post-vaccination Autoimmune (SLE, MS) Systemic malignancy ATM sometimes may follow vaccination or be seen with immune disorders such as systemic lupus erythematosus (SLE) and multiple sclerosis (MS) Acute or subacute myelopathy sometimes occurs as a complication of systemic malignancy similar to limbic encephalitis.18,22 Some cases of ATM with sudden onset may be caused by vascular occlusion and are more accurately characterized as spinal cord infarcts (see subsequent discussion) The precise etiology in most cases remains unknown.23 Incidence, age, and gender The estimated annual incidence of ATM is approximately one case per million.22 ATM occurs in all age groups There is no gender predilection Location Any segment can be affected, although there is a slight predilection for the thoracic cord.23 Multilevel involvement is typical.22,23 Clinical presentation and natural history In typical case, there is no prior history of neurologic all normality.22 Time from symptom onset to maximum deficit ranges from less than hour to 17 days.23 Sensory levels are typically in the thoracic region.23 Prognosis in most cases is poor, and severe residual neurologic deficits are common.22 Imaging findings The major role of neuroimaging is to identify treatable conditions that can mimic ATM These include acute disk herniation, hematoma, epidural abscess, or compression myelopathies.22 During the acute phase, MR scans are normal in approximately half of all ATM cases and nonspecific in the remainder.23 Focal cord enlargement on T1 and poorly delineated hyperintensities on T2weighted scans are the most commonly identified abnormalities (Fig 20-10).22 Enhancement following contrast administration occurs in some cases Miscellaneous Myelopathies Radiation myelopathy Radiation myelopathy is a rare but serious complication of therapeutic irradiation (see box, p 830) The following three criteria for establishing the diagnosis of radiation myelopathy have been established24: The spinal cord must have been included in the radiation field The neurologic deficit must correspond to the cord segment that was irradiated Metastasis or other primary spinal cord lesions must be ruled out Four distinct clinical syndromes of radiation myelopathy have been described, of which chronic progressive radiation myelopathy (CPRM) is the most common form identified on imaging studies.24-26 Chapter 20 Nonneoplastic Disorders of the Spine and Spinal Cord Fig 20-9 This 42-year-old man with a 3-month history of lower extremity weakness had sudden onset of a rapidly ascending sensory level and paralysis A, Sagittal T1-weighted MR scan shows enlargement of the midthoracic spinal cord (arrows) B, Sagittal T2weighted scan shows intramedullary high signal (arrows) C, T1WI following contrast administration shows patchy enhancement (arrows) Biopsy for possible spinal cord neoplasm disclosed multiple sclerosis Fig 20-10 This 16-year-old girl had a two-week history of right arm and leg numbness and tingling following a flulike illness Sagittal T1- (A) and proton density-weighted (B) MR scans show enlargement of the upper cervical cord (A, arrows) with high signal intensity on PDWI (B, arrows) Acute transverse myelopathy 829 858 PART FIVE Spine and Spinal Cord Fig 20-49 This 32-year-old man had a right L5 radiculopathy that remained unchanged following L4-L5 and L5-S1 diskectomies MR scan was obtained days after surgery Sagittal T1- (A) and T2-weighted (B) scans show a possible L5-S1 recurrent HNP (arrows) Sagittal Tl-weighted scan (C) obtained following contrast administration shows most of the mass enhances (large straight arrow) Note enhancement at the posterior anulus of L4-L5 (curved arrow), a normal postoperative finding Nerve root enhancement (small arrows) is striking but is also normal up to months following surgery Reexploration disclosed only hemorrhage and surgical changes cal imaging issue is recurrent HNP versus epidural scar because the former may warrant reoperation, whereas the latter does not NECT is less specific than either CECT or MR.96 Findings suggestive of disk on NECT scans include mass effect, contiguity with the disk space, density greater than 90 Hounsfield units (HU), gas or calcium collection, and nodularity, whereas scar more often lacks mass effect, is located above or below the disk space, and has a linear configuration.100 Disk can be distinguished from epidural fibrosis on 80% of CECT studies.96 Disks are typically seen as areas of decreased attenuation with a peripheral rim of enhancement, whereas scar demonstrates homogeneous enhancement.100 Conventional pre- and postcontrast MR scans are 96% accurate in differentiating disk from scar102; special sequences such as fat-suppressed scans are typically not required (Fig 20-50).103 Mature, organized epidural scar enhances consistently and intensely on early postinjection T1WI, whereas disk material usually-although not invariably-does not enhance immediately following contrast administration (Fig 20-51).102,103a Signal intensity is less helpful in distinguishing these two entities.96 A spectrum of imaging changes are seen in postoperative arachnoiditis Myelographic findings of mild arachnoiditis are blunting of the caudal nerve root sleeves, segmental nerve root fusion, and small irregularities of the thecal sac margin.104 Multisegmental nerve root fusion with root sleeve obliteration, intradural scarring, and loculation is seen with moderate arachnoiditis (Fig 20-52) Severe adhesive arachnoiditis may cause a myelographic block.104 On axial postmyelogram CT scans, nodular or cordlike intradural masses are seen with moderately severe disease (Fig 20-53, A) Sometimes the nerve roots are annealed against the dura and the thecal sac appears empty or featureless (naked sac sign) (Fig 20-53, B) MR findings of arachnoiditis include intradural fibrosis, nerve root clumping, loculation and sacculation, root retraction, and adhesions (Fig 20-54) Fig 20-50 FBSS secondary to recurrent HNP Sagittal T1- (A) and T2-weighted (B) MR scans show recurrent L4-L5 HNP The disk fragment (arrows) is isointense with the parent disk on both sequences Postcontrast sagittal T1WI (C) shows peripheral enhancement (small arrows), but the central mass (large arrows) remains low signal intensity Recurrent HNP surrounded by epidural fibrosis was found at surgery Fig 20-51 Sagittal pre-contrast T1- (A) and T2-weighted (B) MR scans in this patient with FBSS show a large soft tissue mass at the L4-L5 interspace (large arrows) Note high signal in the nucleus pulposus (B, curved arrow) and adjacent marrow (B, small arrows) Postcontrast T1WI (C) shows all of the mass enhances (large arrows) except for a small central portion (open arrow) The disk space does not enhance, but the adjacent marrow (small arrows) shows some increased signal intensity Surgery disclosed a large amount of epidural scar surrounding a small retained disk fragment There was no evidence for diskitis or osteomyelitis 860 PART FIVE Spine and Spinal Cord Fig 20-52 Myelographic findings of moderately severe arachnoiditis on an AP view Note sacculation, effacement of root sleeves, intradural adhesions, and focal scarring Fig 20-53 Two cases illustrate CT-myelographic findings of arachnoiditis A, Intradural fibrosis with clumped nerve roots (arrows) B, Featureless, "naked" thecal sac caused by retraction and adhesion of nerve roots (arrows) to the lateral dural wall Fig 20-54 MR findings of arachnoiditis Sagittal T2weighted MR scan (A) shows thickened, clumped nerve roots (arrowheads), sacculation (small arrows), and intradural fibrotic masses (large arrows) Chapter 20 Nonneoplastic Disorders of the Spine and Spinal Cord 861 Fig 20-54, cont'd Axial T1- (B) and T2-weighted (C) MR scans in another case show a relatively featureless sac (B, arrows) with loculated intradural cyst (C, solid arrows) and retracted, scarred roots (C, open arrows) (compare with Fig 20-53, B) Postoperative osteomyelitis can be identified or both CT and MR studies (Figs 20-55 and 20-56) Contrast-enhanced MR is particularly helpful for delineating diskitis and epidural abscess (Fig 20-56) Postcontrast Tl-weighted scans also show abnormal nerve root enhancement, a relatively common cause of FBSS (Fig 20-57) Conus medullaris or filum terminale tumors may be overlooked unless the thoracolumbar junction is routinely imaged on myelograms or MR studies (Fig 20-58) Other masses that can be overlooked or complicate lumbar surgery and cause postoperative symptoms include synovial cysts and pseudomeningoceles (Figs 20-59 and 20-60) Back Pain in Children In contrast to adults, low back pain in children is uncommonly caused by facet arthroses, spinal stenosis, disk herniation or desire for secondary gain, and often indicates serious disease (see box, p 866) 862 PART FIVE Spine and Spinal Cord Fig 20-55 FBSS secondary to postoperative diskitis and osteomyelitis A, Axial NECT scan shows irregular erosion and end plate destruction (large arrows) with psoas abscesses (small arrows) B, Sagittal midline reformatted scan shows the irregular end plates (large arrows) and paravertebral soft tissue mass (small arrows) Fig 20-56 FBSS with diskitis and epidural abscess A, Sagittal precontrast T1-weighted MR scan shows low signal marrow (small arrows) and a soft tissue mass (large arrows) at the L5-S1 interspace B, Sagittal T2WI shows high signal in the disk space (curved arrow), marrow (small arrows), and soft tissue mass (large arrows) Chapter 20 Nonneoplastic Disorders of the Spine and Spinal Cord Fig 20-56, cont'd C, Sagittal T1WI following contrast administration shows enhancement in the disk space (curved arrows) and marrow (small arrows), and around a loculated low signal fluid collection (lager arrows) Fig 20-57 FBSS secondary to neuritis Postcontrast sagittal (A) and axial (B) T1-weighted MR scans show enhancing L4 nerve root (arrows) (From Jinkins JR, Osborn AG et al, AJNR 14:383-394, 1993.) 863 864 PART FIVE Spine and Spinal Cord Fig 20-58 This 46-year-old man had persisting low back pain year after L4-L5 and L5-S1 diskectomies for bulging disks A, First sagittal T1-weighted MR scan was interpreted as normal Note suboptimal view of conus B, Repeat study with contrast enhancement obtained months later shows a conus medullaris mass (arrows) A schwannoma was found at surgery The patient's symptoms completely resolved after tumor removal Fig 20-59 FBSS following L4-L5 diskectomy and fusion Sagittal postcontrast T1weighted MR scan (A) shows an enhancing cystic mass (arrows) Sagittal (B) and axial (C) T2WIs show the well-delineated cystic mass (arrows) has high signal intensity Juxtaarticular (synovial) cyst was found Chapter 20 Nonneoplastic Disorders of the Spine and Spinal Cord 865 Fig 20-60 This 54-year-old patient had persistent back pain following lumbar diskectomy A, Oblique view of lumbosacral myelogram shows multiple bulbous outpouchings (large arrows) along the distal root sleeves These are arachnoid diverticulae Also present is a larger contrast collection (small arrows) caused by a postoperative pseudomeningocele B, Axial postmyelogram CT scan shows the diverticulae (large arrows) The pseudomeningocele (small arrows) is seen extending through the laminectomy defect (open arrows) C, Coronal T2-weighted MR scan shows the typical CSF-filled bulbous dilatations (arrows) characteristic of arachnoid diverticulae Congenital anomalies Occult spinal dysraphic disorders can cause painful scoliosis Low back pain is also often seen with thick filum terminale and tethered conus medullaris (see Chapter 19) Trauma Spondylolysis, and spondylolisthesis are common Overuse injuries secondary to repetitive, unrepaired microtrauma are frequent, particularly in athletes engaging in high-impact sports (Fig 20-61).105 Pars interartericularis stress fractures and "lim-bus" fractures of the vertebral body ring apophysis are common injuries.106 An avulsed, displaced arc- uate end-plate fragment with attached disk material is present (Fig 20-62).107 Infection Diskitis and osteomyelitis are most commonly found in children younger than 10 years old.105 Disk herniation Disk herniation in prepubescent children is rare, but its prevalence in adolescents is increasing It nearly always occurs acutely with sudden exertion and is therefore a traumatic injury rather than a degenerative one (see previous discussion) 866 PART FIVE Spine and Spinal Cord Fig 20-61 Two cases, both of 13-year-old female gymnasts with low back pain, illustrate imaging findings with stress fractures A, Radionuclide bone scan shows abnormal uptake at the L3 pedicles (arrows) B, Tomographic SPECT scan in the second case shows abnormal uptake in the articular pillars (arrows) C, NECT scan shows bilateral stress fractures (arrows) Back Pain in Children* Congenital malformation (occult dysraphism, tethered cord, diastematomyelia, hydromyelia) Systemic disease (e.g., sickle cell anemia) Overuse injury with stress fracture Avulsion fracture of ring apophysis with detached disk fragment (HNP otherwise uncommon in children) Spondylolysis, spondylolisthesis Scheuerman disease Diskitis, osteomyelitis Tumor (spinal column, spinal cord) Referred pain (check kidneys, hips, etc.) *Not factitious; disease usually real; to be taken seriously Scheuerman disease is a common disorder that consists of vertebral body wedging, end-plate irregularities, and narrowed disk spaces with or without disk herniation Intravertebral disk herniation (Schmorl's nodes) are commonly associated with Scheuerman disease.105 Neoplasms Benign neoplasms and tumorlike lesions in children that may cause back pain include osteoid osteoma, osteoblastoma, and aneurysmal bone cyst; primary osseous malignant tumors include Ewing sarcoma and lymphoma Pain is also a frequent early presenting symptom in children with intramedullary spinal cord tumors such as astrocytoma or ependymoma (see Fig 21-45).108 Chapter 20 Nonneoplastic Disorders of the Spine and Spinal Cord 867 Fig 20-62 This 12-year-old basketball player had a twisting fall A, Axial NECT scan shows an avulsed ring apophysis with accompanying disk fragment (arrows) B, Sagittal T1-weighted MR scan shows the disk (large arrow) with central, very hypointense area representing avulsed cortex (open arrow) Miscellaneous Hip disorders, systemic abnormalities such as sickle cell disease, and gastrointestinal or genitourinary problems can cause back pain TRAUMA In this section, we briefly consider the role of CT and MR imaging in evaluating the patient with spine trauma, particularly soft tissue injury Axial loading These are compressive and vertical force injuries Typical examples include cervical axial loading from diving injury and thoracolumbar loading from jumping injury Axial loading commonly results in vertebral body compression (burst) fractures Lateral element fractures and compression injury (e.g., articular pillar fractures of the cervical spine) are also common Mechanisms of Spine Injury There are four basic types of spine injury: flexion and extension injuries, axial loading (compression) injury, and rotational injury Each type of injury has manifestations that are relatively site-specific for different regions of the spine.109 Rotation injury Rotation injury is rarely isolated and usually occurs in combination with flexionextension injury.109 Lateral mass fractures and facet subluxations are common Uncovertebral fracture dislocations are frequent manifestations of cervical spine rotation injury Flexion injury Flexion injury is common in the cervical and thoracic spine and at the thoracolumbar junction Flexion injury typically results in anterior wedging and vertebral body fractures.109 With sufficient force, disruption of the posterior longitudinal ligament and interspinous ligaments occurs Facet distraction and anteroposterior subluxation is also common with severe injury Osseous Spine Injury Patterns Cervical spine C1 (atlas) Atlantooccipital dislocation is often, but riot invariably, fatal A dens to basion distance greater than 12.5 mm on lateral plain film radiographs should suggest this rare injury.109a The most common injury to C1 is a bilateral vertical fracture through the neural arch This so-called Jefferson fracture is a burst fracture that involves both the anterior and posterior arches (Fig 20-63) The patient is neurologically intact unless the transverse ligament is also disrupted.110 Instability may be present with flexion-extension.111 Rotatory atlantoaxial dislocation is rare Here, the atlas Extension injury Extension injury is particularly common in the cervical region The most common abnormality is posterior element fracture With sufficient hyperextension, the anterior longitudinal ligament ruptures and subluxation may occur 868 PART FIVE Spine and Spinal Cord Fig 20-63 Axial NECT scan shows the anterior and posterior arch fractures of the C1 ring (arrows), also known as a "Jefferson" fracture The transverse ligament is intact, and the relationship between the axis and dens remains normal is rotated more than 45 degrees and the facets are often locked Nontraurnatic C1-C2 rotational subluxation can occur with various lesions such as rheumatoid arthritis C1-C2 subluxation can result from tonsillitis and pharyngitis and is a cause of torticollis in children C2 (axis) Odontoid (dens) fractures usually occur at the base of the dens Horizontal dens fractures can be subtle on axial CT scans, and reformatted sagittal and coronal views are particularly useful (Fig 20-64) The so-called Hangman's fracture is caused by hyperextension resulting in bilateral neural arch fractures (traumatic spondylolysis) (Fig 20-65) The odontoid and its attachments are intact Typically there are bilateral C2 pedicle fractures with separation of the neural arch from the C2 body Anterior subluxation of the C1-C2 complex is common, but spinal cord damage is rare C3-C7 Typical flexion injuries include simple wedge fracture of one or more anterior vertebral bodies Unless the posterior longitudinal ligament (PLL) is disrupted or there is axial loading, retropulsed vertebral body is usually absent.110 If hyperflexion Fig 20-64 An elderly nursing home resident had a fall A, Axial NECT scan shows some C1-C2 rotation and a bone fragment behind the C2 body (arrows) B, Sagittal reformatted scans show the dens is fractured (arrows) and displaced posteriorly Chapter 20 Nonneoplastic Disorders of the Spine and Spinal Cord 869 Fig 20-65 A, Lateral plain film shows traumatic spondylolysis (Hangman's fracture) of C2 (large arrows) Note anterior displacement of the C1-C2 body complex (small arrows) B, Axial NECT scan shows the fracture extends through the pedicles and inferior C2 body (arrows) The patient was neurologically intact occur, the PLL and interspinous ligaments are disrupted The posterior aspect of the affected intervertebral disk space is often widened Facet fracturesubluxation can also occur with flexion injury (Fig 20-66) Other fractures that occur with flexion injury are the "clay-shoveler's" fracture (avulsed spinous process, usually C6 or C7) and the "teardrop" or "burst" ftacture Posterior vertebral body displacement with spinal cord injury is common with burst injuries.110 Vertical compression from diving injury can also cause burst fractures of the mid- and lower cervical spine.109 Extension injuries often disrupt the anterior longitudinal ligament (ALL), widening the anterior aspect of the affected intervertebral disk space Prevertebral soft tissue swelling is often present Avulsion fractures of the anterior vertebral bodies and articular pillar compression fractures are common Nerve root compression and spinal cord injury without obvious fracture-dislocation can occur with extension injury.110 Thoracic spine Thoracic fractures are less common than cervical and thoracolumbar junction injury Thoracic "burst" fractures can occur with severe axial loading Because the ribs and sternum act as Fig 20-66 Axial NECT scan shows bilateral pedicle fractures (small arrows) with some distraction of the superior and inferior articular facets on the right, seen as joint space widening (large arrow) 870 PART FIVE Spine and Spinal Cord Fig 20-67 This 3-year-old child with quadriparesis following cervical spine injury had normal plain film examination (not shown) Sagittal T1- (A) and proton density-weighted MR scans (B) show a large subacute epidural hematoma (arrows) The scan was obtained days after the injury Fig 20-68 A 54-year-old man fell off his horse 10 days before this MR scan Study was obtained because of bilateral lower extremity weakness and sphincter incontinence Sagittal (A) and axial (B) T1-weighted scans show a large extraaxial high signal mass (arrows) with severe cord compression Epidural hematoma was removed at surgery Fig 20-69 A 32-year-old man was quadriplegic following an automobile accident Plain films and NECT scan showed no fracture, but mild C4-C5 subluxation with slight widening of the posterior interspace was seen MR scan was obtained hours after injury A, Sagittal T1-weighted MR scan shows traumatic disk herniation (large arrow) with focally enlarged spinal cord (open arrows) B, Sagittal proton density-weighted study shows the disk herniation (large arrow) and cord contusion, seen here as edema (small arrows) surrounding a focal hypointense area (open arrow) The anterior and posterior longitudinal ligaments are disrupted Fig 20-70 This 24-year-old woman experienced paraparesis immediately after a fall while rock climbing A, Axial NECT scan shows "naked" facets (small arrows), characteristic for severe facet distraction The sagittal reformatted image shows the thoracolumbar "burst" fracture (large arrow) with acute 872 PART FIVE Spine and Spinal Cord Fig 20-71 Use of MR imaging to assess long-term sequelae of traumatic spinal cord injury A, Sagittal T2WI in this 33-year-old quadriplegic man shows cord transection (arrows) and atrophy B, Sagittal T2-weighted scan in this 28-year-old woman paraplegic with an old thoracolumbar burst fracture shows proximal cord atrophy with myelomalacia (open arrows) A small focal syrinx (small arrows) is present ing forces, thoracic fractures are usually stable, unless multiple rib or sternal fractures are present.110 Thoracolumbar junction The majority of thoracolumbar fractures occur between T12 and L2 Nearly 75% are compression fractures, with anterior wedging of one or more vertebral bodies and intact posterior elements Approximately 20% of thoracolumbar injuries are fracture-dislocations in which there is a wedge or burst fracture of the vertebral body combined with facet injury (see subsequent discussion) The facets can be fractured, subluxed, perched, dislocated, or locked.110 In many cases of spine trauma the optimal imaging sequence combines thin-section high-resolution axial CT scans using multiplanar reconstruction (Fig 20-70, A) with MR evaluation of the spinal cord and paraspinous soft tissues (Fig 20-70, B) The precise location of bone fragments can be identified on CT, whereas soft tissue injury to the intervertebral disk, ligaments, and spinal cord is exquisitely delineated with MR Long-term sequelae of spinal cord trauma such as cord transection, traumatic syrinx, myelomalacia, and meningocele are well delineated using high-resolution MR imaging (Fig 20-71) Soft Tissue Injury MR is particularly helpful when neurologic deficits are disproportionate to the observed injury In children, significant spinal cord injury can occur without obvious fracture-dislocation MR depicts cord contusion and edema, and detects extraaxial lesions such as epidural hematoma (Fig 20-67) In adults, soft tissue lesions such as epidural hematoma (Fig 20-68) and traumatic disk herniation with cord compression or contusion (Fig 20-69) are best delineated with emergent MR imaging REFERENCES Sklar EML, Post MJD, Lebwohl NH: Imaging of infection of the lumbosacral spine, Neuroimaging 3:577-590, 1993 Post MJD, Sze G, Quencer RM et al: Gadolinium-enhanced MR in spinal infection, J Comp Asst Tomogr 14:721-729, 1990 Sharif HS: Role of MR imaging in the management of spinal infections, AJR 158:1333-1345, 1992 Brant-Zawadzki M: Infections In Newton TH, Potts DG, editors: Modern Neuroradiology, vol 1: Computed Tomography of the Spine and Spinal Cord, pp 205-229, 1983 Mark AS: MRI of infections and inflammatory diseases of the spine, MRI Decisions pp 12-26, March/April 1991 .. . deficits are typical.38 Chapter 20 Nonneoplastic Disorders of the Spine and Spinal' Cord 833 Fig 20- 13 Gross pathology (A), myelography (B), and angiography (C) of spinal cord AVM (arrows) Note .. . Nonneoplastic Disorders of the Spine and Spinal Cord 821 are often mildly elevated.4 Neurologic deficit and signs of cord compression may occur, with infection spread into the epidural space.4 Imaging .. . central transverse band of reduced signal intensity in the nucleus pulposus (Fig 20- 19 ).5 8 838 PART FIVE Spine and Spinal Cord Fig 20- 20 Pathology of radial anular (type II) tear of the anulus fibrosis