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ORIGINAL ARTICLE
Year : 2022  |  Volume : 70  |  Issue : 8  |  Page : 218-223

Correlation Between Obliquity of Exiting Nerve Root on Lateral Sagittal MRI Images and Degenerative Spondylolisthesis


Department of Neurosurgery, Balwant Institute of Neurosurgery and Intensive Trauma Care (BINIT); Department of General Surgery, Dr. V. M. Government Medical College, Solapur, Maharashtra, India

Date of Submission08-Jun-2020
Date of Decision14-Jun-2020
Date of Acceptance11-Oct-2020
Date of Web Publication11-Nov-2022

Correspondence Address:
Dattaprasanna B Katikar
BINIT, 111, Modikhana, Sat Rasta, Solapur, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.360925

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 » Abstract 


Background: MRI has become the investigation of choice for patients of low back pain with radiculopathy. However, MRI does not consistently detect spondylolisthesis. In far lateral sagittalT2 MRI images, exiting nerve roots are seen descending vertically. We observed that the obliquity of these descending nerve roots may be related to spondylolisthesis.
Objective: Aim of this study is to evaluate the correlation between obliquity of exiting nerve root on MRI and lumbar instability on dynamic radiographs.
Methods and Material: We retrospectively studied 248 patients who underwent discectomy or laminectomy and stabilization for degenerative lumbar disease at our institute from January 2017 to February 2020. For objectively measuring the obliquity of the exiting nerve root, we described an angle between the vertebra and exiting nerve root on far lateral T2 MRI images. We measured the exiting root angle and studied its correlation with degenerative spondylolisthesis on dynamic X-rays.
Results: Out of 108 patients having spondylolisthesis, 106 (98.15%) had an angle of obliquity of the exiting nerve root as >105° and only two (1.85%) had an angleof <105°. Among 140 patients without spondylolisthesis, 137 (97. 86%) had an angle of obliquity of <105°and only three (2.14%) had an angle of >105°. Statistical parameters for our test of “angle of obliquity for the exiting nerve root in spondylolisthesis”are as follows: sensitivity of the test- 98.14%, specificity of the test- 97.85%.
Conclusion: Obliquity of the exiting nerve root is a very easy to detect. It has avery high sensitivity and very high specificity for detecting spondylolisthesis on supine MRI.


Keywords: Degenerative spondylolisthesis, exiting nerve root, low backache, lumbosacral radiculopathy, obliquity of the angle
Key Message: This test, obliquity of the exiting nerve root on MRI, has a very high sensitivity (98.14%) and very high specificity (97.85%) for diagnosing spondylolisthesis on MRI.


How to cite this article:
Katikar DB. Correlation Between Obliquity of Exiting Nerve Root on Lateral Sagittal MRI Images and Degenerative Spondylolisthesis. Neurol India 2022;70, Suppl S2:218-23

How to cite this URL:
Katikar DB. Correlation Between Obliquity of Exiting Nerve Root on Lateral Sagittal MRI Images and Degenerative Spondylolisthesis. Neurol India [serial online] 2022 [cited 2022 Dec 3];70, Suppl S2:218-23. Available from: https://www.neurologyindia.com/text.asp?2022/70/8/218/360925




Low backache, with or without pain in the lower limbs, is a common complaint nowadays. Magnetic resonance imaging (MRI) of the lumbosacral spine has become the investigation of choice for these patients.It has been observed that listhesis may get reduced in the supine position and hence may be missed on MRI and CT scans as both these studies are done with patients in the supine position.[1],[2] Weight-bearing, standing lateral flexion-extension X-rays are the gold standard to confirm or rule out spinal instability.[3],[4],[5]

Several investigators have tried to find the correlation between various degenerative changes seen on MRI and spinal instability.However, the sensitivity and specificity of these signs are not very high.[6],[7],[8],[9],[20]

Far lateral T2 sagittal MRI images show the exiting nerve roots coming out of the intervertebral foramen in an inverted teardrop shape. Usually, they come out and descend straight downwards, but in some cases, they descend obliquely. We carried out a pilot study and described the angle between the exiting nerve root and the lower end plate of the vertebra.

We observed that in patients without spondylolisthesis, this angle was almost a right angle. However, in patients with spondylolisthesis obvious on MRI, this was always an obtuse angle. In some patients, we found this angle was obtuse, but there was no obvious spondylolisthesis on MRI. When we did standing lateral flexion-extension radiographs of these patients, they revealed spondylolisthesis.[21]

The aim of this study was to determine the incidence of the obliquity of the exiting nerve root visible on far lateral Sagittal T2WI MRI and to assess its correlation with lumbar instability present on standing lateral flexion-extension X-rays.


 » Methods Top


This is a retrospective, observational study.

We retrospectively studied patients who underwent discectomy or laminectomy and stabilization for degenerative lumbar disease at our institute between January 2017 and February 2020.

The criteria of inclusion were patients who were operated for lumbar discectomy or lumbar laminectomy and stabilization for degenerative lumbar disease and whose MRI studies and standing lumbosacral spine lateral flexion-extension radiographs were available for review.

The exclusion criteria were patients whose MRI and standing lateral flexion-extension X-rays were not available for review.

We considered degenerative spondylolisthesis to be present when a vertebral slip greater than 3 mm was seen on lateral standing flexion-extension radiographs.[10]

For objectively measuring the obliquity of the exiting nerve root, we described an angle which the exiting nerve root made with the body of vertebra.We selected far lateral sagittal T2-weighted image just lateral to the facet joints or the image that clearly showed exiting nerve roots coming out of intervertebral foramen in an inverted teardrop manner.We drew a line parallel to the lower endplate of the vertebra and another line along the exiting nerve root and measured the angle between these two lines. We considered this the “angle of obliquity of the exiting nerve root”[Figure 1].
Figure 1: The transverse line is the line parallel to the lower endplate of the vertebra, and thevertical line is parallel to the exiting nerve root.The angle calculated here is 91.30°.We can also see roots coming out of the foramen at all the levels at almost right angle to the vertebral body

Click here to view


We studied the correlation of this obliquity of exiting nerve root on lateral sagittal MRI images with spondylolisthesis on standing lumbosacral spine lateral flexion-extension X-rays.

Statistically, we determined the (1) sensitivity of our test, (2) specificity of our test, (3) predictive value of a positive test, and (4) predictive value of a negative test. We calculated Yule's coefficient of association, Q. This showed that the angle of obliquity of exiting nerve root of more than 105° is “very highly associated”with spondylolisthesis.


 » Results Top


The demographic data of our study are shown in [Table 1].
Table 1: Age and gender distribution

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There were 129 (52%) males and 119 (48%) females, with an average age of 47.21 years (range: 26–76 years).

In our study, 108 (43.54%) patients had spondylolisthesis, and it was more common in females [Table 2].
Table 2: Patients with and without spondylolisthesis

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Out of 108 patients with spondylolisthesis, in 67 (62.03%) patients, it was also reported on MRI.However, in 41 (37.96%) patients out of 108 patients, spondylolisthesis was not reported on MRI. This shows that in 37.96% of patients, the spondylolisthesis was missed on MRI [Table 3].
Table 3: Spondylolisthesis reported on MRI and X-rays

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[Table 4] shows a very high correlation between spondylolisthesis and the angle of obliquity of the exiting nerve root of >105°. Moreover, there is very high correlation between the angle of obliquity of the exiting nerve root of <105° and theabsence of spondylolisthesis.
Table 4: Angle of Obliquity of the Exiting Nerve Root in patients with and without Spondylolisthesis.

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Statistically, we calculated the parameters for our test of “angle of obliquity of exiting nerve root in spondylolisthesis” as compared with standing lateral flexion extension X rays, the current gold standard. The sensitivity of the test was found to be 98.14%. The specificity of the test was found to be 97.85%.The predictive value of a positive test was 97.25%.The predictive value of a negative test was found to be 98.56%. Yule's coefficient of association Q for our study was 0.99.

All the above parameters show that the angle of obliquity of the exiting nerve root >105° is very highly associated with spondylolisthesis.


 » Discussion Top


Lumbar spondylolisthesis is a comparatively common condition causing low back pain with or without radiculopathy.In patients with lumbosacral radiculopathy, the presence of spinal instability will dictate the need for stabilization in addition to decompression, whereas in the absence of spinal instability, only decompressive surgery is needed.

To diagnose spondylolisthesis, standing lumbosacral lateral flexion-extension X-rays are the gold standard. As standing X-rays are loading ones, they tend to pronounce the slip of the vertebra. As MRI and CT scans are done in the supine position, they may allow the realignment of slipped vertebra in some patients and the listhesis may be missed in them. Because MRI does not show the degree of slip uniformly, fluid effusion distending facets seen as T2 hyperintensity is used to predict listhesis. Ben-Galim et al.[2] reported that facet fluid effusion bigger than 1.5 mm highly correlates with degenerative spondylolisthesis.[11],[12],[22],[23]

Many authors have studied the association between lumbar facet degeneration and other findings of degeneration on MRI with spondylolisthesis, but the outcomes of these studies are equivocal.[1],[6],[7],[8],[9],[13]

As many investigators have detected linear correlation in facet joint effusion and lumbar instability,[14],[15],[16],[17] the facet fluid sign, despite being imperfect, has become more acceptable among all the tests to the extent of being called thegold standard.[18],[24]

Thus, the quest for a test with high sensitivity and specificity that can reliably predict spondylolisthesis on MRI continues.[25]

We feel that the far lateral sagittal images of the T2-weighted MRI sequence are not usually looked at very carefully. This is the slice that is just lateral to the facet joint. This slice shows exiting nerve roots coming out from the intervertebral foramen.They look like a vertical row of inverted teardrops. If we look carefully, they travel parallel to the posterior border of the vertebra or at right angles to the lower end plate.

Arslan et al., who studied the anatomy of the nerve root, observed that immediately after coming out of intervertebral foramen, the exiting nerve root descends vertically for a few millimeters, crosses the intervertebral disc, and then turns anterio-inferiorly.[19],[26]

Thus, we concentrated on this descending part of the exiting nerve root coming out of the intervertebral foramen.We observed that these roots usually come out of the foramen and descend straight [Figure 2]; however, in some patients, they come out of the foramen and descend obliquely, directing posteriorly. When we studied this further, we realized that at the level of spondylolisthesis, this root descended obliquely [Figure 3]. In some patients, surprisingly, we saw the oblique root without obvious spondylolisthesis at that level on MRI. When we did standing lateral flexion-extension radiographs of these patients, they showed spondylolisthesis [Figure 4]a, [Figure 4]b, [Figure 4]c. This obliquity of the exiting nerve root was quite obvious to a discerning eye, but to have an objective measurement, we described the angle of obliquity exiting nerve root[Figure 1].
Figure 2: Angle of obliquity of the exiting nerve root

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Figure 3: Angle of obliquity of the exiting nerve root >105°in a patient with spondylolisthesis

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Figure 4: (a) In this patient, we did not find spondylolisthesis on MRI. (b) The root was oblique. (c) We did standing lateral flexion-extension X-rays, which showed spondylolisthesis

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During our study, we found that whenever the exiting nerve root looks straight descending down, the angle is less than 105°, and if the exiting nerve root looks oblique, the angle is usually more than 105°[Figure 2] and [Figure 3].

We did a pilot study of 30 patients for studying the obliquity of the exiting nerve root. Encouraged by the outcome, we decided to do a retrospective study of patients who had undergone discectomy or lumbar laminectomy and stabilization at our institute to evaluate the correlation between the obliquity of the exiting nerve root on MRI and spondylolisthesis.

Whenever there is instability, body and the nature try to create stability by adding more tissue. In lumbar spondylolisthesis, it happens by osteophyte formation, additional bone formation, and fibrosis, which try to hold the slipping vertebrae together.

During this process, whenever the added tissue occupies a lot of space and starts compressing the nerve roots, patients get the signs and symptoms of nerve root compression and canal stenosis. We feel that whenever this type of additional tissue formation is there between the two vertebrae, it engulfs the exiting root and makes it oblique because of the slip [Figure 5]a.
Figure 5: (a) Artist's impression of our hypothesis in spondylolisthesis while standing the upper exiting nerve root is seen to be descending vertically almost at a right angle to the vertebral body. The lower exiting nerve root is engulfed by fibrosis and comes out at an obtuse angle to the vertebral body due to listhesis at that level. (b) Artist's impression of our hypothesis in the supine position when the vertebral slip gets obliterated; because of fibrosis, the root continues to be in oblique position even when the vertebrae have aligned

Click here to view


In the supine position, the slip may get neutralized in some patients and vertebrae may get aligned. However, as the exiting nerve root is engulfed in fibrosis, it does not come back to its natural position when the patient becomes supine and it continues to be in the oblique direction [Figure 5]b.

We measured the angle of obliquity for the exiting nerve root in patients with and without spondylolisthesis. When we correlated this data, we came to a conclusion that obliquity of the exiting nerve root on MRI has a very high correlation with spondylolisthesis.

All our statistical parameters show that the obliquity of exiting the root on MRI is an excellent indicator of spondylolisthesis with very high sensitivity and specificity.

Schellinger et al.[16] found out that only 50% of the patients with facet fluid had spondylolisthesis.

Ben-Galim et al.[2] provided the explanations why the face fluid sign may be an imperfect indicator of instability.Hipp et al.[18] mentioned that a perfect relationship between spondylolisthesis and the facet fluid sign is not to be expected.

Rihn et al.[14] described the method for estimating the facet fluid wherein multiple axial T2 MRI images must be selected through the L4–L5 facets and the ratio of the sum of width of facet fluid to the sum of width of thefacets must be calculated.

As compared to this, to see the oblique root, we simply have to study the far lateral sagittal image of T2-weighted MRI where the roots are coming out of the foramina and see the obliquity of the exiting nerve root. In the majority of the cases, we can judge the obliquity by looking at the image. To further endorse the observation, we have specified the angle between the body of the vertebra and the exiting nerve root.

Apart from being highly predictive, we found our method of predicting the listhesis on MRI with obliquity of the exiting nerve root to be more user-friendly, less cumbersome, and easy to apply for all lumbosacral levels. This test, obliquity of the exiting nerve root on MRI, has a very high sensitivity (98.14%) and very high specificity (97.85%) for diagnosing spondylolisthesis on supine MRI.

Limitations of our study: As our study is retrospective and observational, the sensitivity and specificity observed by us need to be further validated by prospective studies.


 » Conclusion Top


In conclusion, this test of obliquity of the exiting nerve root on MRI has very high sensitivity (98.14%) and very high specificity (97.85%) for predicting spondylolisthesis on MRI.

The angle of obliquity of the exiting nerve root >105° is highly associated with spondylolisthesis.

Acknowledgements

The author thanks Dr. Tanmay Mahale for sketching [Figure 5]a and [Figure 5]b.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
 » References Top

1.
Caterini R, Mancini F, Bisicchia S, Maglione P, Farsetti P. The correlation between exaggerated fluid in lumbar facet joints and degenerative spondylolisthesis: Prospective study of 52 patients. J OrthopTraumatol 2011;12:87-91.  Back to cited text no. 1
    
2.
Ben-Galim P, Reitman CA. The distended facet sign: An indicator of position-dependent spinal stenosis and degenerative spondylolisthesis. Spine J2007;7:245-8.  Back to cited text no. 2
    
3.
Quinnell RC, Stockdale HR. Flexion and extension radiography of the lumbar spine: A comparison with lumbar discography. ClinRadiol1983;34:405-11.  Back to cited text no. 3
    
4.
Bendo JA, Ong B. Importance of correlating static and dynamic imaging studies in diagnosing degenerative lumbar spondylolisthesis. Am J Orthop (Belle Mead NJ) 2001;30:247-50.  Back to cited text no. 4
    
5.
Stokes IA, Frymoyer JW. Segmental motion and instability. Spine1987;12:688-91.  Back to cited text no. 5
    
6.
Fujiwara A, Lim TH, An HS, Tanaka N, Jeon CH, Andersson GB, et al. The effect of disc degeneration and facet joint osteoarthritis on the segmental flexibility of the lumbar spine. Spine 2000;25:3036-44.  Back to cited text no. 6
    
7.
Murata M, Morio Y, Kuranobu K. Lumbar disc degeneration and segmental instability: A comparison of magnetic resonance images and plain radiographs of patients with low back pain. Arch Orthop Trauma Surg 1994;113:297-301.  Back to cited text no. 7
    
8.
Bräm J, Zanetti M, Min K, Hodler J. MR abnormalities of the intervertebral disks and adjacent bone marrow as predictors of segmental instability of the lumbar spine. ActaRadiol 1998;39:18-23.  Back to cited text no. 8
    
9.
Grobler LJ, Robertson PA, Novotny JE, Pope MH. Etiology of spondylolisthesis. Assessment of the role played by lumbar facet joint morphology. Spine1993;18:80-91.  Back to cited text no. 9
    
10.
Dvorak J, Panjabi MM, Chang DG, Theiler R, Grob D. Functional radiographic diagnosis of the lumbar spine. Flexion-extension and lateral bending. Spine 1991;16:562-71.  Back to cited text no. 10
    
11.
Tarpada SP, Cho W, Chen F, Amorosa LF. Utility of supine lateral radiographs for assessment of lumbar segmental instability in degenerative lumbar spondylolisthesis. Spine2018;43:1275-80.  Back to cited text no. 11
    
12.
Joseph JR, Chen KS, Than KD, Park P. Evaluation and treatment of degenerative lumbar spondylolisthesis. In: Youmans and Winn, editors. Neurological Surgery. 7th ed, H.Winn Philadelphi, PA: Elsevier; 2017. p. 2384-9.  Back to cited text no. 12
    
13.
Grogan J, Nowicki BH, Schmidt TA, Haughton VM. Lumbar facet joint tropism does not accelerate degeneration of the facet joints. Am J Neuroradiol1997;18:1325-9.  Back to cited text no. 13
    
14.
Rihn JA, Lee JY, Khan M, Ulibarri JA, Tannoury C, Donaldson WF III, et al. Does lumbar facet fluid detected on magnetic resonance imaging correlate with radiographic instability in patients with degenerative lumbar disease? Spine 2007;32:1555-60.  Back to cited text no. 14
    
15.
Chaput C, Padon D, Rush J, Lenehan E, Rahm M. The significance of increased fluid signal on magnetic resonance imaging in lumbar facets in relationship to degenerative spondylolisthesis. Spine2007;32:1883-7.  Back to cited text no. 15
    
16.
Schellinger D, Wener L, Ragsdale BD, Patronas NJ. Facet joint disorders and their role in the production of back pain and sciatica. Radiographics 1987;7:923-44.  Back to cited text no. 16
    
17.
Cho BY, Murovic JA, Park J. Imaging correlation of the degree of degenerative L4–5 spondylolisthesis with the corresponding amount of facet fluid. J Neurosurg Spine 2009;11:614-9.  Back to cited text no. 17
    
18.
Hipp JA, Guyer RD, Zigler JE, Ohnmeiss DD, Wharton ND. Development of a novel radiographic measure of lumbar instability and validation using the facet fluid sign. Int J Spine Surg 2015;9:37.  Back to cited text no. 18
    
19.
Arslan M, Cömert A, Açar Hİ, Özdemir M, Elhan A, Tekdemir İ, et al. Nerve root to lumbar disc relationships at the intervertebral foramen from a surgical viewpoint: An anatomical study. Clin Anat 2012;25:218-23.  Back to cited text no. 19
    
20.
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.  Back to cited text no. 20
    
21.
Amitkumar M, Singh PK, Singh KJ, Khumukcham T, Sawarkar DP, Chandra SP, Kale SS. Surgical Outcome in Spinal Operation in Patients Aged 70 Years and Above. Neurol India 2020;68:45-51.  Back to cited text no. 21
[PUBMED]  [Full text]  
22.
Yerramneni VK, Kanala RR, Kolpakawar S, Yerragunta T. MITLIF Operative Nuances- Step by Step. Neurol India 2021;69:1196-1199.  Back to cited text no. 22
[PUBMED]  [Full text]  
23.
Davanzo J, Brandmeir NJ. Surgical Technique and Patient Selection for Spinal Cord Stimulation for Chronic Pain. Neurol India 2020;68(Supplement):S213-S217.  Back to cited text no. 23
    
24.
Vajramani GV. High Frequency (HF10) Spinal Cord Stimulation for Chronic Neuropathic Pain. Neurol India 2020;68(Supplement):S337-S339.  Back to cited text no. 24
    
25.
Singh V, Rustagi T, Mahajan R, Priyadarshini M, Das K. Ligamentum Flavum Cyst: Rare Presentation Report and Literature Review. Neurol India 2020;68:1207-1210.  Back to cited text no. 25
[PUBMED]  [Full text]  
26.
Baldia M, Mani S, Walter N, Kumar S, Srivastava A, Prabhu K. Bone Marrow-Derived Mesenchymal Stem Cells Augment Regeneration of Intervertebral Disc in a Reproducible and Validated Mouse Intervertebral Disc Degeneration Model. Neurol India 2021;69:1565-1570.  Back to cited text no. 26
[PUBMED]  [Full text]  


    Figures

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