MRI of the lumbar intervertebral disc

Clinical Rudiolog.v ( 1999) 54, 703-723

Pictorial Review

MRI of the Lumbar Intervertebral Disc STEVEN MORGAN, ASIF SAIFUDDIN

The Department of Radiology, The Royal National Orthopaedic Hospital Trust, Brockley Hill, Stanmore. Middlesex HA7 4LP, U.K.

Received: 27 April 1999 Revised: 21 June 1999 Accepted: 27 June 1999

The lumbar spine is one of the commonest regions of the body imaged with MRI. Various pathological processes can involve the lumbar intervertebral disc, including degeneration, infection and trauma and these may present with a variety of signal intensity and morphological changes as depicted by MRI. The aim of this pictorial review is to illustrate these abnormalities and discuss their clinical relevance where appropriate. Morgan, S. and Saifuddin, A. (1999) Clinical Radiology 54, 703- 723. 0 1999 The Royal College of Radiologists

Key words: lumbar spine, intervertebral disc, MRI.

Low back pain and sciatica are frequent clinical complaints and the lumbar spine is one of the commonest regions examined by magnetic resonance imaging (MRI). This pictorial review is aimed at illustrating the various focal and generalized abnormalities of the lumbar intervertebral disc as demonstrated by MRI and discusses the clinical relevance of the imaging findings based on a review of the literature.

NORMAL ANATOMY OF THE LUMBAR INTERVERTEBRAL DISC

The disco-vertebral complex is an avascular, secondary cartilaginous joint composed of three components: the cartilaginous end-plate, annulus fibrosus and nucleus pulposus. The vertebral end-plate is composed of a flat bony disc with a slightly elevated rim due to the attached ring apophysis. This produces a central depression in the end-plate that is occupied by hyaline cartilage.

The annulus fibrosus has an outer and inner layer. The tough outer layer is composed of bundles of tightly packed type-1 collagen fibres laid down in a concentric fashion forming thin lamellae that are thickest anteriorly. They are attached both to the adjacent hyaline cartilage, and more firmly to the ring apophysis periosteum as Sharpey fibres. Annular fibres also merge with both anterior and posterior longitudinal ligaments. The outer annulus appears hypointense on all pulse sequences and is optimally demonstrated on T2 weighted fast spin echo

Correspondence IO: Dr Asif Saifuddin, Consultant Radiologist, The Royal National Orthopaedic Hospital Trust, Brockley Hill, Stanmore, Middlesex. HA7 4LP. U.K.

0009-9260/99/I IO703+2 I $12.0010

(T2W FSE) images. The inner annulus is composed of fibro- cartilage and contains a high proportion of type-II collagen. It is indistinguishable from the hyperintense nucleus pulposus on T2W FSE images [I]. The nucleus pulposus is a remnant of the embryonic notochord and is composed of a proteoglyan matrix and type-II collagen. The negatively charged proteoglycan matrix absorbs water adding to its resilience. The normal nucleus is hyperintense on T2W FSE images and relatively hypointense compared to normal vertebral marrow on Tl weighted spin echo (TIW SE) images. The intranuclear cleft is seen in normal adults and is caused by fibrous transformation of the gel-like matrix of the central portion of the nucleus polposus [I]. It is almost invariably seen over the age of 30 years [2] and appears as a hypointense band centrally within the nucleus on T2W FSE images (Fig. 1).

The notochord remnant is commonly seen as an indentation of the superior and inferior end-plates and contains disc material of normal signal characteristics.

MR SEQUENCES USED IN LUMBAR SPINE IMAGING

The lumbar spine is typically imaged using TlW SE and T2W FSE sagittal sequences, supplemented with TlW SE and/ or T2W FSE axial images at selected levels [3]. Alternatively, a dual-echo T2W FSE axial sequence has been proposed to reduce the need for an axial TlW SE sequence [4]. Gradient echo imaging of the spine has also been performed [5] but the anatomy of the annulus is poorly demonstrated. T2W FSE sequences have been associated with some reduction of signal intensity (SI) from the normal nucleus pulposus compared to conventional T2W SE sequences, but this does not appear to

0 1999 The Royal College of Radiologists

704 CLINICAL RADIOLOGY

Fig. 1 - Normal lumbar intervertebral discs (LU2 to L4/5) on a sagittal T2W FSE image. The intervertebral cleft is best seen in the L112 disc as a hypointense band running horizontally. Loss of signal at the LYSI level indicates disc degeneration.

affect the diagnosis of disc degeneration [6]. The use of fat saturation can result in increased contrast between the disc and marrow [7] but is not routinely employed in the assessment of degenerative disc disease. However, it is of value in the assessment of traumatic, infective and neoplastic involvement of the spine.

NORMAL PHYSIOLOGICAL ALTERATIONS OF THE LUMBAR DISC

A normal diurnal variation occurs in hydration of the

intervertebral disc with influx of water overnight and gradual reduction during the day. This produces a measurable change in disc water content, disc height and disc volume. all of which reduce throughout the day together with a mild increase in disc bulge [&lo]. However, none of these changes are visible to the reporting radiologist [lo].

Extension of the spine is associated with anterior migration of the nucleus pulposus in the normal disc [ 1 1, 121.

ABNORMALITIES OF THE LUMBAR INTERVERTEBRAL DISC

Abnormalities of the discovertebral complex can be divided into changes in SI and/or changes in disc morphology, which can be either focal or generalized. They may affect the nucleus or annulus separately or in combination.

CHANGES IN DISC SIGNAL INTENSITY

Nucleus Pulposus

increased SI on Tl W SE Imaging

Increased SI of the nucleus pulposus on TIW images is an uncommon manifestation of mild disc calcification in association with degenerative disc disease 113,141 (Fig. 2). As the disc calcification increases, the Tl W SI becomes hypointense [ 141. Hyperintense disc calcification tends to be seen in old age and is not considered to be of clinical relevance.

Disc calcification or ossification may occur as a late consequence of spinal trauma or discitis, or secondary to conditions such as ankylosing spondylitis (Fig. 3) [15], which can lead to the development of marrow spaces within the disc.

Subacute intradiscal haemorrhage associated with spinal trauma may cause increased SI on TlW images (Fig. 4). Bone within the disc space is seen after anterior discectomy and fusion and appears isointense to marrow (Fig. 5).

Finally, it is important to remember that diffuse infiltrative disorders of the vertebral marrow may result in generalised SI loss in the vertebral body, giving the appearance of relative hyperintensity of the intervertebral disc.

Decreased SI on TI W SE Imaging

The intervertebral disc vacuum phenomenon is due to a collection of intradiscal nitrogen and most commonly occurs in degenerative disc disease. It appears as a linear area of signal void on both TlW and T2W sequences (Fig. 6), although in a small proportion of cases, the T2W SI may be increased [16]. Gradient echo sequences have a greater sensitivity to this abnormality [17]. Intradiscal gas may also be seen adjacent to vertebral collapse from both benign and malignant causes [ 181.

Generalized mild hypointensity in the disc is seen with infective discitis [I91 and with disc degeneration. The use of interbody titanium cages for anterior fusion will result in signal void within the disc space.

h4Rl OF THE LUMBAR INTERVERTEBRAL DISC 705

Fig. 2 Calcification (confirmed radiographically) in the L5/Sl disc, manifest as hyperintensity on both sagittal TlW SE (left) and T2W FSE (tight) images.

i .=

Fig. 3 - Disc calcification (confirmed radiographically) in ankylosing spondylitis. involving both nucleus and annulus at various levels, and appearing hyperintense on both sagittal TIW SE (left) and T2W FSE (right) images.

Fig. 4 - E vlild diffise hyperintensity from subacute disc haemorrhage in the TI 1112 and T12/Ll discs on Tl W SE (left) and fat saturated T2W FSE im (right), following Ll burst fracture. Note also haematoma in the conus medullaris.

Increased SI on T2 W SE Imaging

Any condition associated with increased intradiscal water will cause hyperintensity on T2W images. Disc oedema secondary to infection is the commonest, with hyperintensity seen in 95% of cases (Fig. 7) [19,20]. This is associated with loss of definition of the vertebra1 end-plates, inflammatory change in the adjacent vertebral marrow and paravertebral or epidural abscess. The disc may also appear hyperintense following acute spinal trauma (Fig. 4).

Decreased SI on T2W SE Imaging

Generalized reduction of disc SI (Fig. 1) occurs as a consequence of ageing [21] and with disc degeneration [1,22], two conditions that cannot be differentiated by MRI [23]. The high sensitivity and specificity of MRI in the diagnosis of disc degeneration has been confirmed in vivo compared to discography [24]. Progressive degeneration is associated with further loss of signal, loss of disc height and bulging of the annulus fibrosus. Signs of advanced degeneration include calcification and the vacuum phenomenon, as mentioned previously.

Early MIU signs of disc degeneration include infolding of the anterior annulus and a hypointense central dot (Fig. 8) [25]. These can be seen before any loss of disc SI and may be associated with pain reproduction at discography [26]. Failure to recognise these early signs of disc degeneration may be one reason for the reported finding of apparently normal MRI in the presence of abnormal discography [27,28].

Changes consistent with rapid disc degeneration are seen following chemonucleolysis and include loss of both disc SI and height [29-311.

ages

Fig. 5 - Anterior discectomy and fusion with bone graft resulting in a hyperintense mass within the L4/5 and LX I disc spaces on a TI W SE MR image. Artifact is due to arthrodesis of the LS/Sl facets.

MRI OF THE LUMBAR INTERVERTEBRAL DISC 707

Fig. 6 - The intndiscal I mcuum phenomenon appearing as linear signal void on a TIW SE image (top) with corrqmding CT re~~n~tnr~tbn (bottom).

Foci of increased SI may occur in degenerate discs from a variety of causes. Disc calcification has been discussed earlier (Figs 2 and 3). Linear hyperintensity parallel to the end-plate has been demonstrated and is thought to represent separation of the nucleus pulposus from the hyaline cartilage end-plate [25] as a manifestation of advanced degeneration (Fig. 9). Fluid- filled cystic spaces have also been demonstrated in degenerate discs in the absence of infection [23,32].

Increased SI within a degenerate disc with associated Type 1 end-plate changes (see later) has been termed ‘inflammatory disc degeneration’ [33] and must be differentiated from infective discitis, which can have a similar appearance. The presence of an associated paravertebral or epidural inflammatory mass or abscess is an important differentiating feature. Signal loss on T2W images with associated end-plate erosions can be seen with discovertebral destruction in ankylosing spondylitis [34].

Disc Enhancement Following Intravenous Gadolinium-DTPA

Enhancement may occur within the non-operated degenerate disc, the infected disc and the post-operative disc. Disc

degeneration may be accompanied by ingrowth of blood vessels from the periphery of the annulus into the nucleus. Such disc vascularization produces either linear (Fig. 10) or nodular intradiscal or peridiscal enhancement [33,35] and has been described in patients with low back pain. However, comparison studies with discography have not been performed so the sensitivity or specificity of this sign as a marker of a painful degenerate disc is unknown.

Intradiscal enhancement is common following discectomy. Although it can be seen following successful surgery [36], it has been suggested that it indicates post-operative discitis, especially if associated with oedema in the adjacent end- plates [37,38]. Intradiscal enhancement is almost invariable with infective discitis (Fig. 7c) [ 191.

Anmilus Fibrosus Increased SI on TI W SE Imaging

High SI may be seen in the annulus from calcification/ ossification in degenerative disc disease (Fig. 11) or with ankylosing spondylitis (Fig. 3) [15].

Enhancement may be seen within the annulus on enhanced


(b) CC)

Fig. 7 - ((I) Sagittal TIW SE (left) and coronal RW FSE (right) MR images in a patient with infective discitis showing fluid in the degenerate L415 disc and oedema within the adjacent bone marrow. (h) axial pre-gadolinium (c) post-gadolinium Tl W SE MRI showing enhancement both within the disc space and in the circumferential paravettebral inflammatory mass.


Fig. 8 - Early signs of disc degeneration on T2W FSE images. (a) Hypointense central dot within the L4/5 disc. (b) Infolding of the anterior annulus of the L3/4 disc with normal nuclear signal intensity. A thin hyperintense linear signal extends from the nucleus into the posterior annulus consistent with a radial annular tear (c) Corresponding L3/4 discogram showing a thin posterior radial annular tear with extradural leak of contrast medium. (Reproduced with pennissim from: Saifuddin A, Broithwite I. White J. Taylor BA. Runton P. The value of lumbar Apine magnetic resonnnce imaging in the denmstrotion of onulor tears. Spine 1998: 23453-457).

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Fig. 9 - Sagittal T2W FSE image showing loss of signal in the lower lumbar discs and hyperintense lines parallel to the end-plates at the I.415 and L5/Sl disc levels, indicating separation of the degenerate nucleus pulposus from the cartilaginous end-plate.

TlW sequences as a manifestation of a radial annular tear [39]. Extradural enhancement associated with annular tears, and occasionally involving the adjacent nerve root, has also been described in patients with discogenic low back and leg pain [40] but is a rare finding (Fig 12).

Increased SI on l-2 W SE Imaging

Post-mortems have revealed three types of annular tear: concentric, radial and transverse, the latter two being identifiable

with MRI [41]. Transverse tears occur at the disc periphery as a result of disruption of Sharpey’s tibres (Fig. 13) and are not thought to be of clinical significance. Radial tears extend from the nucleus for a variable distance through the annulus, and when extending into the outer annulus, are manifest on MRl as the high intensity zone (HIZ) [42]. The HIZ is defined as a focal area of high SI within the posterior annulus of a degenerate disc, separate from the nucleus (Figs 12 and 14). On axial T2W FSE images, the HIZ is linear or globular and although most commonly present centrally within the annulus, it may be paracentral or laterally placed. Such findings are associated with an outer radial annular tear at discography. Several studies comparing MRI with discography in symptomatic patients have indicated that the HIZ is a highly specific marker of a painful disc [26,42-441 or segmental instability [45]. However, the sensitivity of the sign is low [26&l] and it has also been described in asymptomatic populations [46], limiting its value. As mentioned previously, the HIZ enhances following intravenous Gd-DTPA. Although the exact spatial relationship between the HIZ and the radial annular tear has not been proven, comparison of axial T2W FSE MRI with CT discography indicates that the two lesions do occur in the same place within the annulus (Fig. 14). Anterior HIZs are a rare finding but it should be noted that isolated anterior radial annular tears can be associated with back pain [26,47].

Radial annular tears may also be identified as linear areas of hyperintensity extending into the annulus from the nucleus (Figs 8b.c and 15).

CHANGES IN DISC MORPHOLOGY

Increased Disc Height

Increases in disc height are seen with pathological vertebral compression fractures due to displacement of the end-plate (Fig. 16). more commonly with malignant involvement of the vertebral body than osteoporotic collapse [48]. Increased disc height can also occur in association with burst fractures.

Fig. 10 - Degenerate L561 disc vascularisation. Sagittal TIW SE image (left) shows minor loss of SI. Sagittal T2W FSE image (centre) shows loss of SI but also a linear area of increased SI in the posterior inferior aspect of the nucleus. Enhanced sagittal Tl W SE image (right) showing linear enhancement within the nucleus.

MRI OF THE LUMBAR LNTERVER’IEBRAL DISC 711

Fig. I I - Posterior annular ossification manifest as focal hyperintensity on both Tl W SE (left) and T2W FSE (right) images in a patient with a degenerate 1 disc and lytic spondylolisthesis.

. .

Decreased Disc Height

The commonest cause of decreased intervertebral disc height is degenerative disc disease which is associated with a decrease in disc SI (see above). Other causes include acute disc hernia, infection, trauma, rheumatoid arthritis, amyloidosis and ochronosis.

A small disc showing normal signal characteristics may be seen in association with developmental anomalies of lumbosacral transition (Fig. 17) [49,50].

ABNORMALITIES OF DISC CONTOUR

Abnormal Peripheral Disc Margin

Abnormal configuration of the disc margin may be focal or diffuse. A disc hernia is focal displacement of nuclear, annual or end-plate material beyond the normal peripheral margin of the disc, as delineated by the margins of the adjacent vertebral body end-plate. This is distinct from a circumferential extension of the disc, which is termed a disc bulge (Fig. 18) [23,5 11. Disc hernias (Fig. 19) can be further sub-divided into protrusions and extrusions depending on the integrity of the outer annular fibres. A disc protrusion is hemiation with an intact annulus, and is also referred to as ‘contained disc hemiation’. However, the term ‘contained disc herniation’ is also used by

some authors to describe disc hemiation confined by the posterior longitudinal ligament (PLL). Extruded discs occur where nuclear material breaches the outer annular fibres. Extruded discs can be further categorized as sub- or transligamentous depending on the integrity of the PLL. If the herniated disc becomes detached from the parent disc it is termed sequestrated. A sequestrated fragment can migrate superiorly, inferiorly, or rarely posteriorly to the dural sac [.52]. Rarer posterior disc hernias include intradural [53,54], which may show diffuse enhancement with intravenous Gadolinium- DTPA [5.5], and transdural [56]. The PLL forms a thin black line on T2W sagittal image. In transligamentous extrusion this line is interrupted. MRI has been shown to be highly accurate in the diagnosis of different types of disc hernia [57]. Evaluating the difference between protruded and extruded discs can be difficult and is only of clinical importance if techniques such as automated percutaneous lumbar discectomy (APLD) are being considered. Two additional MR signs have been described. Firstly, if the AP diameter of the herniated disc is greater than 50% of the spinal canal diameter, then an extrusion is present in over 90% of cases [58]. Secondly, a protrusion usually has a broad base against the parent disc, broader than any other part of the hernia. By comparison, an extrusion often has a base narrower than the extruded material [51]. Protrusions and extrusions may also be differentiated by their outline. Since a protrusion is limited by the outer annular fibres, it tends to have

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Fig Pas der

(6)

12 - High intensity zone (HIZ). (a) Sagittal TlW SE (left). sagittal T2W FSE (centre) and enhanced sagittal TIW SE (right) images showing HIZs in ;erior annulus at the L&5 and L5/Sl levels. Both show enhancement. (b) Axial TIW SE (left) and enhanced TIW SE (right) images at the LS/Sl II nonstrating enhancing extradwal inflammatory tissue adjacent to the posterior disc margin and involving the right Sl nerve root.


Fig. 13 - Sagittal T2W FSE image demonstrating transverse anterior annular tears in the L1/2 to L4/5 discs disrupting Shapey’s fibres.

a smooth outline whereas an extrusion has a poorly defined outer margin [23]. Disc hernias may be central. paracentral, subfacetal (foraminal) or true lateral in position. Foraminal hernias may be mistaken for neurogenic tumours when associated with foraminal enlargement and marked contrast medium enhancement [59].

Sequestrated disc fragments are reliably diagnosed on MRI, typically exhibiting a slightly higher SI on T2W sequences than the parent disc [60] and showing peripheral enhancement following intravenous gadolinium [61]. The latter feature may be a predictor of spontaneous resolution of the hernia [62].

Intraosseous Disc Herniation

Schmorl’s nodes are hemiation of nuclear material into trabecular bone of vertebral end-plates (Fig. 20). They are

caused by any process that weakens the vertebral end-plate or by trauma in otherwise normal bone. Most are incidental findings on lateral radiographs although some are symptomatic 1631.

On MRI, chronic Schmorl’s nodes appear as extensions of disc material into the vertebral body, typically surrounded by a rim of low SI due to reactive sclerosis [23]. Some Schmorl’s nodes are associated with enhancing marrow oedema. Such vascular Schmorl’s nodes are larger and more frequently associated with bone marrow oedema in patients with back pain than in asymptomatic patients [64]. Occasionally, the oedema may extend throughout the vertebral body into the pedicles, raising the suspicion of infection or malignant infiltration [65].

Chronic Schmorl’s nodes may also be associated with fatty end-plate changes (Fig. 20b). Hemiation of disc material into the anterior ring apophysis is termed the anterior limbus lesion or limbus vertebra and is seen in children [66]. It can be associated with significant back pain and imaging features that may be mistaken for infection (Fig. 21). Posterior limbus lesions are also described [67] and, in adults, indicate acute disc hernia.

Traumatic intraosseous disc hernia may also give rise to the acquired coronal cleft vertebra [68] where hemiation of disc material from the disc both above and below the affected vertebra can separate the vertebral body.

ABNORMALITIES OF THE VERTEBRAL END-PLATE

Signal changes within the vertebral end-plate (Medic changes) are a manifestation of degenerative disc disease and are divided into three types (Fig. 22) [69,70]. Type-l changes consist of reduced SI on TlW SE sequences and increased SI on T2W FSE sequences and are due to fibrovascular replacement of the subchondral bone. Type-2 changes have increased SI on both Tl W SE and T2W FSE sequences and are associated with fatty replacement of the subchondral bone. Type-3 changes consist of reduced SI on both TlW SE and T2W FSE sequences are associated with subchondral sclerosis on radiographs. A mixture of Types can be seen [71] and there is evidence that Type-l changes convert to Type-2 changes with time. Several studies suggest that degenerative end-plate changes are associated with back pain, particularly Type-l changes [45,7 1,721. The low prevalence of end-plate changes in an asymptomatic population supports this [46].

Similar end-plate changes can be seen following chemonucleolysis [73] and adjacent to Schmorl’s nodes (Fig. 20). as mentioned previously. Other causes of oedema in the end-plate include infection and trauma.

Defects of the end-plate can be seen with intraosseous disc hernia, discitis. trauma and rarely, tumour extending into the disc from the vertebral body [20].

CLINICAL RADIOLOGY

(b)

Fig. 14 - (a) Sagittal T2W FSE (left) and axial T2W FSE (right) im ages demonstrating a degenerate L4/5 disc with focal high SI in the nucleus ; and a right paracenual HZ Cbj CT discoeram at IA15 demonstratine a full thickness right paracentral radial annul& tear with leak of conuast met into the extradural space.


Fig. 15 - Axial T2W FSE image demonstrating a right pancentral radial annular tear in the TIZ/Ll disc.

Fig. 16 - T2W FSE image showing increase in L2/3 and L314 intervertebral disc height secondary to pathological collapse of the L3 vertebral body from Langerhans Cell Histiocytosis.


Fig. 17 -Characteristic appearances on TIW SE (left) and T2W FSE (right) MR images of a developmentally small L561 disc at the level of a lumbosar transition.

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Fig. 18 - Axial T2W FSE MR image showing a degenerate L4/5 disc with mild generalized disc bulge. Note the loss of central nuclear Sl.


Fig. 19 - Different types of disc hemiation. ((1) Sagittal T2W FSE (left) and axial TIW SE (right) MR images demonstrating a cenkal LA15 disc protrusion. The posteriorannulus is intact as is the PLL. This therefore represents a ‘confined hemiation’. (h) Sagittal T2W FSE (left) and axial TI W SE (right) MR images demonstrating a right paracentral U/5 disc extrusion. The posterior annulus is disrupted but the extruded disc material is contained by the PLL. (c) Axial TI W SE MR image showing a right sided foraminal and far lateral disc hemiation. (d, Sagittal TI W SE MR image showing LYS I disc extrusion. Both the posterior annulus and PLL are disrupted. (e) Axial unenhanced (left) and enhanced (right) TIW SE MR images showing a right paracentral disc hemiation with peripheral enhancement, consistent with a sequestrated fragment.

MR1 OF THE LUMBAR INTERVERTEBRAL DISC 719

(b)

Fig. 20 - (a) Sagittal TIW SE (left) and RW SE (right) MR i showing an acute Schmorl’s node in the inferior end-plate of LS assc with oedema in the adjacent vertebral body. (b) Sagittal TIW SE MR showing a chronic calcified Schmorl’s node in the superior end-plate associated with fatty change in the adjacent vertebral body marrow

mages riated image

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Fig. 21 - Limbos vertebra from hemiation of disc material into the ring apophysis. (a) Coned lateral plain radiography of the L1/2 disc showing loss of disc height which is most marked anteriorly, apparent destruction at the anteroinferior comer of LI and sclerosis in the adjacent vertebral bodies. (h) Sagittal TIW SE (left) and T2W FSE MR images (right) demonstrating loss of SI and hemiation of the L1/2 disc into the anterior ring apophysis, with adjacent marrow changes consistent with combined oedema and sclerosis.

(b)


(b)


Fig. 22 - End-plate changes associated with degenerative disc disease. (a) Sagittal TIW SE (left) and T2W FSE MR images (right) showing disc degeneration at the LA/5 and L5/Sl levels and Type I end-plate changes at LA/5 consisting of low SI on TI and high Sl on T2. (b) Sagittal TIW SE (left) and T2W FSE MR images (right) showing disc degeneration at the L3/4, LA/5 and L5/Sl levels and Type 2 end-plate changes at L4/5 consisting of increased SI on both T1 and T2W images. (c) Sagittal Tl W SE (left) and T2W FSE MR images (right) showing disc degeneration at the L2f3, L4/5 and L5/Sl levels and combined Type I and 3 end-plate changes at L2/3. consisting of decreased SI on both TI and T2W sequences anteriorly with hyperintensity on T2 posteriorly. Note the L5/S I disc hernia which appears hypenntense compared to the parent disc. a feature of a sequestrated fragment (same patient as in Fig. 19~).

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MRI of the lumbar intervertebral disc

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