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ORIGINAL ARTICLE
Year : 2020  |  Volume : 68  |  Issue : 6  |  Page : 1378--1384

Magnetic Resonance Evaluation of Lumbar Disc Degenerative Disease as an Implication of Low Back Pain: A Prospective Analysis

Reddy Ravikanth 
 Department of Radiology, Holy Family Hospital, Thodupuzha, Kerala, India

Correspondence Address:
Dr. Reddy Ravikanth
Department of Radiology, Holy Family Hospital, Thodupuzha - 685605, Kerala
India

Abstract

Background: The main objectives of this study are MR characterization of disc degeneration and sequelae, analysis of lumbar disc degeneration patterns in patients with low back pain, and evaluation of the extent of involvement. This unique study evaluates the number of discs involved and the Modic changes at prolapsed, degenerated nonprolapsed, and at nondegenerated, nonprolapsed levels. Study Design: A prospective, magnetic resonance imaging–based radiological study. Materials and Methods: A total of 1000 whole spine and lumbosacral spines were subjected to MRI examination, including spin echo with T1, T2, and STIR sequences. The Modic classification, Pfirrmann disc classification method, Borenstein criteria for central spinal canal stenosis, and Weishaupt Classification for Facet Degeneration were used for evaluation. Results: The commonest level of disc degeneration was L4-L5 (41.2%) and the commonest type was disc protrusion (69.4%). Disc height reduction was common at L5-S1 level (32.2%). Multidisc involvement is the commonest presentation (38.2%) followed by contiguous double level (34.7%) with disc bulges frequently reported at L3-L4 (27.2%) and L4-L5 (26.9%) levels. Majority of discs (56.1%) demonstrated Modic changes at prolapsed levels. Spondylolisthesis was commonly reported at L5-S1 level (87.5%) and was mostly associated with lumbar canal stenosis (38.4%). Posterior osteophytes were frequent at L3-L4 (31.1%) and L5-S1 (31.1%) levels. D12-L1 was least affected (4.1%) in lumbar disc degenerative disease. Conclusion: The clinicians evaluated multiple variables associated with intervertebral disc degeneration and its sequelae such as lumbar canal stenosis and found the evaluation methods to be simple and practical in evaluating lumbar spine degeneration and simple communication.



How to cite this article:
Ravikanth R. Magnetic Resonance Evaluation of Lumbar Disc Degenerative Disease as an Implication of Low Back Pain: A Prospective Analysis.Neurol India 2020;68:1378-1384


How to cite this URL:
Ravikanth R. Magnetic Resonance Evaluation of Lumbar Disc Degenerative Disease as an Implication of Low Back Pain: A Prospective Analysis. Neurol India [serial online] 2020 [cited 2021 Feb 25 ];68:1378-1384
Available from: https://www.neurologyindia.com/text.asp?2020/68/6/1378/304091


Full Text



Low back pain resulting from lumbar disc degenerative disease is one of the most common causes of disability in working age adults.[1] On imaging, the earliest visible changes of intervertebral disc degeneration occur at the endplate which are best visualized on magnetic resonance imaging (MRI).[2] The initial stages of disc degeneration are characterized by loss of disc signal intensity on T2W MRI images with/without disc height reduction. Hypointensity of the disc on T2W images results due to loss of hydration.[3] In later stages of the disc degeneration, morphological changes such as loss of disc height, annular tears, disc protrusion and extrusion, posterior osteophyte formation, facetal joint arthropathy, ligamentum flavum hypertrophy, juxtafacetal synovial cysts, and lumbar canal stenosis materialize. The current study evaluates the common variables associated with intervertebral disc degeneration and correlates with the lumbar disc levels. The unique feature of the study is the evaluation of the number of levels of disc involvement and Modic changes at prolapsed, degenerated nonprolapsed, and at nondegenerated, nonprolapsed levels.

Study design

A prospective, MRI–based radiological study.

 Materials and Methods



The institutional ethical committee approved the study and, only then, we analyzed the results of 1000 whole spine and lumbosacral spine MRI examinations performed in 422 females and 578 males in the Department of Radiology and Diagnostic Imaging at a tertiary care center between April 2014 and December 2018 in patients diagnosed with low back pain due to lumbar disc degeneration. The examinations were performed using GE Brivo 1.5T device, including spin echo with T1, T2, and STIR sequences in axial, coronal, and sagittal planes, respectively. The age group varied from 18 to 90 years (Mean 45). Patients who undertook prior surgeries, spinal infections, and active malignancies were excluded from the study. The study population was subjected to the evaluation of variables such as reduced disc height, disc desiccation, disc herniation, disc bulge, disc extrusion, narrowing of the neural foraminal, lateral recess, lumbar canal stenosis, compression of the nerve roots, posterior osteophytes, juxtafacetal spinal cysts, facetal joint arthropathy, and ligamentum flavum thickening [Table 1], [Table 2] and [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]. Continuous and intermittent low back pain and spondylolisthesis were correlated with the intervertebral disc level [Table 3]. In addition, the number of levels of disc involvement was evaluated [Table 4] and the end plate signal intensity changes were evaluated as per the Modic system [Table 5]. The distribution of Modic changes among discs in the study population was correlated at prolapsed, degenerated and prolapsed, and nondegenerated and nonprolapsed levels [Table 6]. The Pfirrmann classification system, Central Spinal canal stenosis grading criterion, Weishaupt Classification for sagittal disc degeneration on T2W MRI, for spinal canal stenosis, and Facet Degeneration classification [Table 7], [Table 8], [Table 9] were used, respectively. Classification systems for neural foraminal narrowing are based on the degree of effacement of perineural fat within the foramen on T1-weighted sagittal images. Two such systems were proposed by Wildermuth et al. and Lee et al. Both systems use four grades [Table 10].{Figure 1}{Figure 2}{Figure 3}{Figure 4}{Figure 5}{Figure 6}{Table 1}{Table 2}{Table 3}{Table 4}{Table 5}{Table 6}{Table 7}{Table 8}{Table 9}{Table 10}

 Results



A total 1000 patients with low back pain were evaluated for lumbar degenerative disc disease with MRI examinations. 422 females (42.2%) and 578 males (57.8%) aged 18-90 years were included in the study. The disease was frequent in the 4th–5th decades of life. A total of 623 patients reported loss of lumbar lordosis whereas it was preserved in 377 patients with low back pain at presentation.

A total of 1820 disc involvements were identified in the current study with an average of 1.82 disc involvement per patient. The commonest level of disc degeneration was L4-L5 (41.2%) and the commonest type is disc protrusion (69.4%). Disc height reduction was common at L5-S1 level (32.2%). Six patients (0.6%) showed changes of discitis on MRI. A total of 451 patients (45.1% of total patients) demonstrated a medial annular disc tear with the commonest involvement at L4 –L5 level (42.4%) and 408 patients (40.8% of total patients) demonstrated paramedian annular tear with the commonest involvement at L4 –L5 disc level (51.2%). The right and left paramedian tears were noted in 206 patients (20.6% of total patients) and 202 patients (20.2% of total patients), respectively. The right paramedian tear was slightly more common as compared to the right side in patients and the commonest level of disc involvement is at L4-L5 level (50.7% on the right and 51.3% on the left). A total of 398 patients (39.8% of total patients) demonstrated foraminal annular tear with the commonest level of involvement at L4–L5 (59.7%). The right and left foraminal tears were demonstrated in 211 (21.1% of total patients) and 187 patients (18.7% of total patients), respectively. The right foraminal tear was more common as compared to the left and the commonest level of disc involvement is at L4-L5 (57.2% on the right and 64.1% on the left). Protrusion was demonstrated in 1264 discs (69.4% of disc involvement), extrusion was demonstrated in 42 discs (18.8% of disc involvement), and disc bulges demonstrated in 597 disc (32.8% of disc involvement). The commonest levels of disc protrusion and extrusion are L4–L5 disc level as noted in 583 and 161 discs (46.1% of protrusions and 47.2% of extrusions). Commonest level of disc bulge is at L3 – L4 noted in 162 (27.2% disc bulge) and at L4 – L5 disc level as noted in 161 discs (26.9% disc bulge). Posterior osteophytes were commonly found at L3 – L4 (31.1%) and L5 – S1 (31.1%) levels. Spinal canal narrowing was demonstrated at 451 disc levels (24.8% of disc involvement), commonest at L4-L5 disc as noted in 182 (40.3% of spinal canal narrowing). Narrowing of lateral recess and compression of neural foramen were demonstrated in 998 discs (54.8% of disc involvement) and both were common at L4–L5 levels (49.1% with narrowing of lateral recess and 48.8% with compression of neural foramen). Facetal arthropathy and ligamentum flavum thickening was seen at 1642 disc levels (90.2% of the disc involvement) and both were common at L4 – L5 disc level (44.1%). Ninety patients (0.9% of total patients) showed spondylolisthesis in the form of anterolisthesis or retrolisthesis. However, anterolisthesis (70.2% of spondylolisthesis) was common as compared to retrolisthesis (29.2% of spondylolisthesis). Listhesis of the L5 vertebral body was the commonest as compared to S1 vertebral body in 79 patients (87.5% of spondylolisthesis). Multidisc involvement is the commonest presentation (38.2%) followed by contiguous double level (34.7%) with disc bulges frequently reported at L3–L4 (27.2%) and L4–L5 (26.9%) levels. Majority of discs (56.1%) demonstrated Modic changes at prolapsed levels. Spondylolisthesis was commonly reported at L5-S1 level (87.5%) and was mostly associated with lumbar canal stenosis (38.4%). Posterior osteophytes were frequent at L3-L4 (31.1%) and L5-S1 (31.1%) levels. D12-L1 was least affected (4.1%) in lumbar disc degenerative disease.

 Discussion



Lumbar disc degeneration disease is an irreversible and the most common cause of low back pain in the world. The disc structures were directly evaluated for disc degenerative disease with MRI that correlates the dehydration of the discs with the signal from the T2-weighted images. An area of increased signal may be identified within the disc or along the annulus of the disc and is associated with an annular disc tear. Changes at the endplate adjacent to the disc have been described as reactive endplate changes and graded as Modic 1, Modic 2, and Modic 3 changes.[4] Modic 1 reactive endplate changes demonstrate decreased signal intensity on T1 images and increased signal intensity on T2 images representing marrow edema and inflammation. Modic 2 reactive endplate changes are represented by increased T1 signal intensity and isointense T2 images which represent conversion of hemopoietic bone marrow into yellow fatty marrow as a result of marrow ischemia. Modic 3 reactive endplate changes demonstrate decreased disc signal intensity on both T1 and T2 images representing bony sclerosis at each endplate.

This study found that disc degeneration was more common in males (982 of 1820 involved discs representing 53.9%) than females (838 of 1820 involved discs representing 46.1%) which was consistent with prior studies.[5] The disc degeneration presenting age was observed at the 4th-5th decades of life in our study, which was comparable with other studies.[6] Disc desiccation occurred in 342 discs (18.8% of disc involvement). In our study, D12-L1 (4.1%) was the least affected level in lumbar disc degenerative disease and variables like thecal indentation, annular tears, disc protrusion, disc extrusion, posterior osteophytes, spinal canal narrowing, lateral recess narrowing, compression of neural foramina, facetal joint arthropathy, ligamentum flavum hypertrophy, and lumbar canal stenosis were more commonly found at L4–L5 and L5–S1 levels. The results were comparable with previous studies which is craniocaudal direction pattern of incidence and severity of disc degeneration.[7]

The main presentation of disc herniation is sciatica. In this study, 82% of patients with low back pain and radiculopathy had disc herniation as compared to 9% in those with low back pain only (P = 0.004). Degenerative spinal stenosis is more common in patients with sciatica than in patients with low back pain. In this study, the prevalence of lumbar canal stenosis among patients with radiculopathy was 38.4%, and none was found among patients with low back pain only (P = 0.003). These findings are similar to findings by Shobeiri et al.[8] The small canal in patients with stenosis causes thecal sac or nerve roots to impinge against the spine bone elements, thus causing radiculopathy and activity-dependent pain. Similar to the study, the proportion of degenerated discs (reduction in disc signal intensity) progressively increases with the lower spine level and the most common spine levels were L4/L5 and L5/S. In line with the reports by Ong et al., 85% of the discs had normal signal intensity upto L1/L2 level, which then progressively decreased to 47% at L4/L5 level.[9] The prevalence of Modic changes (28%) was higher as compared to 23% found by Kuisma et al.[10] and is lower than the prevalence of 43% found by Jensen et al.[11] Similar to the studies by Takarad et al., disc herniation was most commonly found in posterolateral (75%), followed by 24% posterocentral and 2% foraminal.[12]

The Pfirrmann Classification of spinal disc degeneration is based on disc structure homogeneity, Nucleus Pulposus - Annulus Fibrosus distinction, MR signal intensity of Nucleus Pulposus, and preservation of disc height.[13] Grade 4 distribution was common at L4-L5 and L5-S1 levels (144 disc levels, 36.7% of disc involvement) while Grade 1 distribution was common at L1-L2 level (203 disc levels, 51.8% of disc involvement). The Borenstein lumbar central canal stenosis grading system, based on the separation degree of cauda equina on T2-weighted axial images (grade 0 = no lumbar stenosis without obliteration of anterior CSF space; grade 1 = mild stenosis with separation of all cauda equina; grade 2 = moderate stenosis with some cauda equina aggregated; and grade 3 = severe stenosis with none of the cauda equina separated), is correlated with the anterioposterior diameter measurements of spinal canal.[14] Facetal degeneration was seen at 272 disc levels (13.2% of the disc involvement) and was common at L5-S1 disc level (38.4%). The Weishaupt Classification of facet degeneration is based on joint space narrowing, osteophytosis of articular processes, hypertrophy of articular processes, and subchondral erosions and cysts.[15] Facetal degeneration was seen at 1642 disc levels (90.2% of the disc involvement) and was common at L4 – L5 disc level (44.1%).

Multidisc involvement is the commonest presentation (38.2%) followed by contiguous double level (34.7%) with disc bulges frequently reported at L3-L4 (27.2%) and L4-L5 (26.9%) levels which is in concordance with prior studies.[16] Spondylolisthesis was commonly reported at L5-S1 level (87.5%) and mostly associated with lumbar canal stenosis (38.4%) which is also consistent with results of prior studies.[17] In the current study, juxtafacetal synovial cysts (4.5% of disc involvement) constitute cystic dilatations of synovial sheaths that directly extrude from facet joints into the spinal canal and were most commonly demonstrated at L4-L5 (69.3% of synovial cysts) and L5-S1 (22.2% of synovial cysts) disc levels which is in agreement with findings of prior studies.[18]

 Conclusion



Lumbar disc degenerative disease is the most common condition that results in low back pain that neurosurgeons and radiologists frequently encounter. MRI is the preferred method for assessment of disc degeneration and its sequelae due to its multiplanar capability. In conclusion, we evaluated the common variables associated with intervertebral disc degeneration such as thecal indentation, annular tears, disc protrusion, disc extrusion, posterior osteophytes, spinal canal narrowing, lateral recess narrowing, compression of neural foramina, facetal joint arthropathy, ligamentum flavum hypertrophy and as well as the combined effects of these changes on the spinal canal such as lumbar canal stenosis which were more commonly found at L4-L5 and L5–S1 levels with D12-L1 level having the least involvement in lumbar disc degeneration. Multidisc involvement followed by contiguous double levels and presence of Modic changes at prolapsed levels were the unique findings in the current study. In addition, Pfirrmann grading system of disc degeneration, lumbar canal stenosis grading system of Borenstein, and Weishaupt classification of facetal degeneration are helpful to clinicians for simple and practical evaluation of degeneration of lumbar spine and for simple communication.

Acknowledgments

I wish to thank Mr. Vipin Jose, Senior Technician, Department of Radiology for his assistance in retrieving images.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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