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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 11  |  Issue : 3  |  Page : 131-135

Morphometric Analysis of Lumbar Dorsal Root Ganglia: A Cadaveric Study


1 Assistant Professor, Department of Anatomy, BGS Global Institute of Medical Sciences, Bengaluru, Karnataka, India
2 Associate Professor, Department of Anatomy, BGS Global Institute of Medical Sciences, Bengaluru, Karnataka, India
3 Professor, Department of Anatomy, BGS Global Institute of Medical Sciences, Bengaluru, Karnataka, India

Date of Submission26-Mar-2022
Date of Decision24-May-2022
Date of Acceptance06-Jun-2022
Date of Web Publication14-Jul-2022

Correspondence Address:
K R Rohini
Department of Anatomy, BGS Global Institute of medical sciences, Kengeri, Bengaluru - 560 060, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/NJCA.NJCA_69_22

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  Abstract 


Background: As there is an increase need for less invasive techniques, especially in the spinal interventional procedures, detailed anatomical structures need to be defined for the better surgical outcome. After an intensive search of the literature, it was found that the available information regarding human lumbar dorsal root ganglia is limited. Therefore, the current study was aimed to analyze the morphometry and location of the dorsal root ganglia in lumbar region. Materials and Methods: One hundred intervertebral foramina from 10 formalin-fixed human cadavers examined from L1 to L5 level. The morphometry of dorsal root ganglia was noted and evaluated. The position of dorsal root ganglia was classified based on its relation to pedicle. Results: The mean length of the dorsal root ganglia was L1, 6.49 mm; L2, 9.63 mm; L3, 12.18 mm; L4, 13.43 mm; L5, 14.95 mm. The mean width was L1, 5.01 mm; L2, 5.96 mm; L3, 6.71 mm; L4, 6.8 mm; L5, 6.83 mm. The mean distance between the dorsal root ganglia and the nerve root was L1, 3.51 mm; L2, 4.03 mm; L3, 5.2 mm; L4, 7.24 mm; L5, 8.46 mm. Most of dorsal root ganglia were intraspinal in L1-L2 intervertebral foramen, intraforaminal in L2-L3 to L4-L5 level and extraforaminal at L5-S1. Conclusion: In-depth knowledge of position of dorsal root ganglia will be helpful in safely performing surgery in the lumbar spinal region.

Keywords: Dorsal root ganglia, intervertebral foramen, lumbar spine


How to cite this article:
Rohini K R, Ashok K R, Komala B. Morphometric Analysis of Lumbar Dorsal Root Ganglia: A Cadaveric Study. Natl J Clin Anat 2022;11:131-5

How to cite this URL:
Rohini K R, Ashok K R, Komala B. Morphometric Analysis of Lumbar Dorsal Root Ganglia: A Cadaveric Study. Natl J Clin Anat [serial online] 2022 [cited 2022 Oct 6];11:131-5. Available from: http://www.njca.info/text.asp?2022/11/3/131/350922




  Introduction Top


Lower back pain is a major health issue that affects people all over the world.[1] The lumbar region's dorsal root ganglion (DRG) has been suggested to causative factor in the mechanism of lower back pain and also in sciatica.[2],[3],[4] DRG are sensitive to mechanical compression which occurs in condition like disc herniation.[5]

The possible reason for the symptoms experienced in patients with disc herniation in lumbar region is the compression of DRG.[6]

The percutaneous radio frequency used to treat DRG in chronic lower back pain radiating to lower limb shows to be useful and safe with a success rate of approximately 60%.[7]

Thus, the location of DRG and its relations are important to understand pathological anatomy and for therapeutic interventions. Many anatomical studies describe the morphometry of DRG, but still, there are no normal baseline morphometric values of the DRG.[2],[3],[6] This study was done to know the morphometry of DRG and its location with respect to the intervertebral foramina in the cadaver to add to the present knowledge.


  Materials and Methods Top


One hundred dorsal root ganglia were studied from 10 formalin-fixed human cadavers aged between 50 and 70 years of both gender (males – 7 and females – 3), from the department of Anatomy BGS Global institute of medical sciences, Kengeri, Bengaluru, with the approval from institutional ethics committee (letter no. BGS GIMS/GEN/08/2018-19 dated 09/01/2019) were included in the study. Specimens indicating gross evidence of congenital or acquired diseases and also the foraminal levels where distortion of normal anatomical relationship has occurred were excluded.

Dissection was done by placing the cadaver in prone position and posterior aspect of the spinal elements from L1 to S1 were exposed by the paraspinal approach. All the soft tissues between the spinous process and transverse process were removed. Inter transverse muscles were dissected to visualize the extraforaminal region. A bone cutter was used to remove the laminae and facets of the vertebrae to appreciate the pedicles, thecal sac, and the neural tissue. The nerve root and its ganglion were visualized at each level. Relationship of dorsal root ganglia to the intervertebral foramen was noted.

The proximal and distal margins of oval-shaped DRG were noted. The following parameters were studied [Figure 1] and [Figure 2]: (a) DRG length – The distance between the proximal and distal ends of DRG, (b) The widest area of DRG was taken as the width, (c) The DRG distance from the nerve root, (d) Comparing them on either side, and (e) DRG position – this was identified by taking midpoint of the ganglia as a reference point. It was studied using 2 lines. The first line connected medial borders of the pedicles and the second one connecting the lateral edges of the pedicles. DRG situated medial to the first line was considered intraspinal. The medial and lateral edges of the pedicles were used as intraforaminal zone. The extraforaminal region is lateral to the lateral border of the pedicle.[8]{Figure 1}{Figure 2}

Morphometric measurement was done using Vernier calipers (precision = 0.1 mm). Statistical Package for social sciences (SPSS for windows, version 16.0, SPSS INC®, Chicago, USA) was used for the statistics with significance set at P < 0.05.


  Results Top


One hundred lumbar intervertebral foramen from 10 cadavers were included in the study. One foramen at the L5-S1 level on the right side of the male cadaver was excluded because of distortion of the tissue.

Most of the DRG from L2-L3 to L4-L5 level were intraforaminal. Sixty-five percent of dorsal root ganglia in L1-L2 intervertebral foramen level was intraspinal and 68% of DRG were extraforaminal at L5-S1 level [Graph 1].[INLINE:1]

The mean length of DRG was L1, 6.49 mm; L2, 9.63 mm; L3, 12.18 mm; L4, 13.43 mm; and L5, 14.95 mm. The mean width of DRGs was L1, 5.01 mm; L2, 5.96 mm; L3, 6.71 mm; L4, 6.8 mm; and L5, 6.83 mm. The mean distance between DRG and the nerve root was L1, 3.51 mm; L2, 4.03 mm; L3, 5.2 mm; L4, 7.24 mm; and L5, 8.46 mm. All these parameters gradually increased from L1 to L5 as shown in [Table 1] and were statistically significant. The difference in the DRG length, width, and distance from nerve root on either side was not statistically significant.{Table 1}

It was observed that all these parameters of the DRG were larger in males when compared to females [Table 2]. However, these values between them were not statistically significant.{Table 2}


  Discussion Top


The DRG is collection of cell bodies of neurons and it acts as a conduit of sensory impulses from various receptors to the central nervous system.[9] Recent studies suggest that DRG are not just passively transmitting the signals, but are actively involved in modulating the signal processing, especially during inflammation or injury by releasing cytokines and ion channel changes which initiate the hyperexcitability of neurons in the spinal ganglia.[10] Ahimsadasan et al. stated that high permeability between blood and nervous tissue makes DRG more susceptible to neurotoxic substances and toxic metabolites from drug-induced neuropathies.[11] DRG is also concerned with the transition of pain from acute to chronic.[10]

DRG is used as an ideal target to treat long-standing lower extremity pain. As the spinal ganglia are easily accessed, either through the neuroforaminal approach or from the epidural space to the outside; the site is used as target for surgery, radiofrequency ablation, and therapeutic steroid injections.[11]

DRG develops in neural crest cells, as development progresses it migrates toward the periphery.[12] DRG is normally situated in the intervertebral foramen, below the vertebral pedicle. However, the ganglia in the sacral region are present inside the vertebral canal.[13]

Many authors classified anatomical positions of DRGs into intraspinal, intraforaminal, and extraforaminal.[6],[14],[15] In the present study, it was observed that 65% of dorsal root ganglia in L1-L2 intervertebral foramen were intraspinal, large percentage of the L2, L3, and L4 DRG was located within the foramen and 68% of DRG were extraforaminal at L5-S1 level. As shown in [Table 3], most of the studies described the DRG at the lumbar levels as an oval structure and were intraforaminal.[3],[6],[14],[16],[17],[18] The difference can be attributed to ethnicity and also a slight variation in classifying the position, in our study, we took the midpoint of ganglia as landmark.{Table 3}

Several researches said that proximally situated DRG has been associated with radiculopathy.[12],[19] Hasue et al. observed the nerve root canal of intraspinal type of dorsal root ganglia, mainly in subarticular region, is slender and also stable, so the intensity of the motional compression is more. Thus, the intraspinal position of the DRG is vulnerable to chemical and mechanical stimulation.[15] The minimal space in intervertebral foraminal area makes the intraforaminal DRG more susceptible to compression by disc herniation.[18] Ohmori et al. studied the relationship between DRG location and clinical symptoms; they observed that the severity of low back pain was more in extraforaminal position of DRG.[20]

A study done by Moon et al. found no difference in the location of the spinal ganglia in terms of age, height, weight, and gender and also proved that contrast images act as a good anatomical reference for positional categorization of DRG.[3]

In the current study, there was a gradual increase in the length and width of DRGs from upper to lower lumbar levels. These findings are consistent with the result of previously done studies as shown in [Table 4]. But in comparison with their result, the parameters in our study were greater than their measurement, especially at the lower lumbar levels. This difference may be because of the selection of subjects, or different population groups and even because of the use of different techniques.{Table 4}

The dimension of spinal ganglia was larger in males than females, which was similar to the study done by Shen et al.[6] but unlike our study, they were statistically significant at L1, L2, and L5 levels.

Mirkovic et al.[23] described a triangular safety access zone to approach intervertebral disc in the lumbar region; exiting lumbar nerve root forms its lateral margin. Vialle et al.[24] noted that the spinal ganglion is positioned in lateral margin of safe triangle and the distance of DRG from nerve root is 7.95 mm and because of the oval shape of DRG, it may obstruct the safe limit. They instead proposed a rectangular safety zone to reduce the nerve injury and neuropathic pain. In the current study, the distance of DRG from the nerve root was ranging from 3.51 mm at L1-L2 level to 8.46 mm at L5-S1 foramen level.

The result from the present study compared to previous studies indicates that there is variation in the parameters of DRG in the lumbar region among different population. Hence, it is necessary to evaluate population-specific anatomical parameters and to be considered during surgical procedures. However, morphological values of DRG from the study to be recognized as normal anatomic value are limited due to short number of sample size and range.


  Conclusion Top


A deep understanding of anatomy and variation of dorsal root ganglia is essential for proper diagnosis, and also for improving the interventional treatment of neuropathic pain syndromes. In the present study, we observed the varying positions of DRG in upper and lower lumbar levels which were not noted in other studies done in different populations. We also observed the increase in dimensions of DRG from upper to lower lumbar levels. Further continuation of the study in large subjects by cadaveric and radiographic studies will add to the existing morphological knowledge of DRG.

Acknowledgment

The authors sincerely thank those who donated their bodies to science so that anatomical research could be performed. Results from such research can potentially increase Humankind's overall knowledge can then improve patient care. Therefore, these donors and their families deserve our highest gratitude.[25]

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Moon HS, Kim YD, Song BH, Cha YD, Song JH, Lee MH. Position of dorsal root ganglia in the lumbosacral region in patients with radiculopathy. Korean J Anesthesiol 2010;59:398-402.  Back to cited text no. 3
    
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Kobayashi S, Yoshizawa H, Yamada S. Pathology of lumbar nerve root compression. Part 2: Morphological and immunohistochemical changes of dorsal root ganglion. J Orthop Res 2004;22:180-8.  Back to cited text no. 4
    
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Weinstein J. Report of the 1985 ISSLS traveling fellowship. Mechanisms of spinal pain. The dorsal root ganglion and its role as a mediator of low-back pain. Spine (Phila Pa 1976) 1986;11:999-1001.  Back to cited text no. 5
    
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Shen J, Wang HY, Chen JY, Liang BL. Morphologic analysis of normal human lumbar dorsal root ganglion by 3D MR imaging. AJNR Am J Neuroradiol 2006;27:2098-103.  Back to cited text no. 6
    
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van Wijk RM, Geurts JW, Wynne HJ. Long-lasting analgesic effect of radiofrequency treatment of the lumbosacral dorsal root ganglion. J Neurosurg 2001;94:227-31.  Back to cited text no. 7
    
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Vanderlinden RG. Subarticular entrapment of the dorsal root ganglion as a cause of sciatic pain. Spine (Phila Pa 1976) 1984;9:19-22.  Back to cited text no. 12
    
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Baron EM. Spinal cord and spinal nerves: Gross anatomy. In: Standring S, editor. Gray's Anatomy: The Anatomical Basis of Clinical Practice. 41th ed., Philadelphia: Elsevier; 2016.p. 767.  Back to cited text no. 13
    
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Kikuchi S, Sato K, Konno S, Hasue M. Anatomic and radiographic study of dorsal root ganglia. Spine (Phila Pa 1976) 1994;19:6-11.  Back to cited text no. 14
    
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Hasue M, Kunogi J, Konno S, Kikuchi S. Classification by position of dorsal root ganglia in the lumbosacral region. Spine (Phila Pa 1976) 1989;14:1261-4.  Back to cited text no. 15
    
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Arslan M, Cömert A, Açar Hİ, Ozdemir M, Elhan A, Tekdemir I, 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. 18
    
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