
==== Front
J Neurosurg Case Lessons
J Neurosurg Case Lessons
J Neurosurg Case Lessons
Journal of Neurosurgery: Case Lessons
2694-1902
American Association of Neurological Surgeons

39186824
10.3171/CASE24301
CASE24301
SpineSpineLumbarLumbarTechniqueTechniqueCase Lesson
Contralateral discectomy as a novel approach for disc herniation compressing a conjoined nerve root: illustrative case
Trakolis Leonidas MD 1
Petridis Athanasios K MD 12
1 Department of Neurosurgery, St. Luke Hospital, Thessaloniki, Greece
2 Heinrich Heine University Medical School Düsseldorf, Düsseldorf, Germany
Correspondence Leonidas Trakolis: St. Luke Hospital, Thessaloniki, Greece. leonidastra86@hotmail.com.
INCLUDE WHEN CITING Published August 26, 2024; DOI: 10.3171/CASE24301.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

26 8 2024
26 8 2024
8 9 CASE2430109 5 2024
12 6 2024
© 2024 the authors
2024
the authors
https://creativecommons.org/licenses/by-nc-nd/4.0/ CC BY-NC-ND 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

BACKGROUND

A conjoined nerve root is a rare condition with numerous variants. The diagnosis can be challenging, especially when the condition coexists with other pathologies. In cases where a disc herniation affects these nerve roots, any miscalculation or inexperience of the surgeon can irreversibly injure them. Numerous reports have described the dismay of surgeons during discectomy in patients with a conjoined nerve root. Many surgical techniques have been suggested but without the good results following typical discectomies.

OBSERVATIONS

In this case report, the authors describe a 53-year-old female patient who presented with radicular pain due to a large disc herniation at the level of L5–S1 on the left side. Intraoperatively, the authors identified a conjoined nerve root, forcing them to employ a novel approach with very good results.

LESSONS

In some cases, the only possible way to remove a disc herniation is the contralateral approach, as described in this report.

https://thejns.org/doi/10.3171/CASE24301

conjoined nerve
contralateral discectomy
disc herniation
ABBREVIATIONS

MRI = magnetic resonance imaging.
==== Body
pmcLumbar disc herniation is a very common condition, and in many cases, the only effective therapy is surgical discectomy. A conjoined nerve root is a rare finding that can complicate the surgical procedure, often leading surgeons to make compromises. Its reported incidence varies greatly, from 2% to 17.3%,1 and in most cases, it affects the nerve roots of the lumbar spine. Patients usually present with the typical symptoms of disc herniation—radicular pain, numbness, and/or motor weakness—although symptoms from different roots are possible as well.2 On magnetic resonance imaging (MRI) examination, the conjoined nerve root is not always identifiable, either because it is under a massive disc herniation or because the image quality is insufficient. Ideally, high-quality, thin-slice MRI with coronal views2–5 or computed tomography myelography5, 6 should be performed preoperatively. Kang et al. proposed an alternative method of identification, that is, observation of the sagittal shoulder sign, which promises an accuracy of up to 91%.7 Nevertheless, it is rather common to diagnose a conjoined nerve root during surgery,2, 8, 10 surprising the surgeons and sometimes leading to irreversible damage to the nerve root.1, 10 Removal of the disc herniation is impossible in most cases, as the root(s) is under tension and unmovable.11 Intraoperative management is restricted to extensive decompression of the nerve structures and consists of hemilaminectomy, foraminotomy, lateral recess decompression, and/or partial pediculectomy,1 and if possible, partial removal of the herniated disc,11 which has remained unchanged over time. Nonetheless, the success rate in treating a conjoined nerve root is rather disappointing compared to ordinary nerve roots,12, 13 mostly because of the technical difficulty in removing the bulging disc. We report the case of a 53-year-old female patient with a disc herniation at level L5–S1 on the left side, which compressed the left L5 (conjoined) nerve root. As far as we are aware, the surgical method used in this case, a discectomy from the contralateral side, has not been described.

Illustrative Case

A 53-year-old female patient presented to us with severe radicular pain in the left leg. She worked as a cleaning lady and had experienced back pain for years. In the last 3 weeks, the pain had exacerbated and radiated to the left leg (L5 dermatome). In the neurological examination, mild numbnessi in the same dermatome with dysesthesia was noticed but without any motor weakness. The Lasègue (straight leg raise) sign was positive on the left side at 45°. Additionally, she had pain in the left iliosacral joint. She had broken her right leg a few months earlier and since then had put more strain on her left leg. Otherwise, she was healthy and took no medication. MRI examination of the lumbar spine showed a disc bulging at the L4–5 level on the left side with contact with the exiting L5 root, as well as a larger caudal sequestered disc herniation at the L5–S1 level on the left side (Figs. 1–4) with compression of the descending L5 root. Painkillers proved to be inadequate, so we decided to proceed with surgical discectomy. We started with a hemilaminectomy from the left side at L5–S1, continuing with a flavectomy until we reached the L5 nerve root and a further similar structure exactly below it, which entered the same foramen (Fig. 5). This structure was very firm and unmovable. We suspected that it might be the bulging disc instead of an additional nerve root, so we decided to carefully make a 2-mm straight incision on it, parallel to the nerve fibers. As soon as we saw some cerebrospinal fluid exit, we stopped and covered the structure with a cotton ball. We concluded that there was a double L5 nerve root exiting in the same foramen. The subligamentous disc herniation was intensively compressing both nerve roots and the thecal sac. After performing a foraminotomy and unroofing the conjoined root, we tried to mobilize the disc herniation over the exit of the upper root and afterward between the 2 L5 roots, but without success, as they were both firm and fixed in place. The nerve structures were under high pressure, so we decided to change our strategy and go from the contralateral (right) side to avoid further manipulation of the nerve roots. We performed an incomplete hemilaminectomy and flavectomy on the same level, this time from the right side. We identified the (single) L5 nerve root on this side as well as the L5–S1 disc. The paramedian disc herniation could be felt with the nerve hook. We incised the disc and performed a nucleotomy. The herniation was hard and difficult to mobilize with the hook. However, we had enough space to move the thecal sac gently to the left side and remove the disc herniation with the Kerrison rongeurs and the grasping forceps. After the removal of part of the disc and most of the disc herniation, we washed the disc with saline solution and checked both sides to ensure that the nerve roots and the thecal sac were relaxed. We closed the small incision on the left lower L5 nerve root with a 1 × 1–cm Tachosil and confirmed (twice) with the Valsalva maneuver that the closure was watertight. We closed the wound with fascial, subcutaneous, and intradermal sutures. No Redon drainage was needed. FIG. 1. Sagittal T2-weighted MRI sequence showing the 2 L5 nerve roots (red arrow).

FIG. 2. Sagittal T2-weighted MRI sequence showing unifying of the L5 nerve root in the foramen (red arrow).

FIG. 3. Axial T2-weighted MRI sequence showing 1 of the 2 L5 nerve roots (red arrow), whereas the other is hidden under the disc herniation.

FIG. 4. Axial T2-weighted MRI sequence showing disc herniation between the 2 L5 roots (red arrows).

FIG. 5. Illustration of the anatomy seen during surgery in our case. The arrows highlight the L5 nerve roots on the left side.

The next day, the patient was mobilized. She had severe weakness of the left gastrocnemius muscle and numbness of the complete left L5 dermatome, probably from the perioperative manipulation of the L5 roots on the left side. Nonetheless, she had no pain, could walk independently, and was discharged home. She received some paracetamol and methylprednisolone for a week. The neurological deficits resolved within 1 week, and she experienced only pseudoradicular pain on the left side and very slight dysesthesia of the left calf and upper left foot. The pain radiated from the left gluteal region to the back of the knee, most probably from an irritation of the iliosacral joint. Less than 2 weeks after surgery, the pain decreased, motor function remained intact, and the dysesthesia was unchanged. She stopped taking painkillers and began physiotherapy. At the 1-month examination, she had slight dysesthesia starting from the lower middle of the left calf and reaching to the second and third toes. The pain in the iliosacral joint and the motor weakness disappeared, and she sometimes had very slight radicular pain from the gluteal region to the upper half of the left calf. She moved freely, did not need any painkillers or other medication, and was able to work again.

Patient Informed Consent

The necessary patient informed consent was obtained in this study.

Discussion

Observations

Conjoined nerve roots, although rare, are the most common nerve anomalies described, affecting mostly the L4–S1 lumbar roots.1, 5 Various diagnostic methods have been utilized to identify the pathology,3–7, 14 with MRI being the most effective.15 Nevertheless, most cases will be diagnosed intraoperatively,8, 12 drastically increasing the risk of iatrogenic nerve injury. In cases of a shared dural envelope or additional nerve roots, retraction is almost impossible, leading to postsurgical symptoms such as neurapraxia and pain.16 In our case, retraction led to temporary weakness of the gastrocnemius muscle and persistent numbness of the L5 dermatome. Thankfully, under corticosteroid therapy, the symptoms subsided only a few days later. Some patients present with an inhomogeneous and atypical clinical picture, with a negative Lasègue sign (or a negative crossed straight leg raise sign) and differences between sensory deficits and pain radiation.2, 5, 17 In our case, however, the patient presented with typical L5 radicular pain and numbness. The preoperative MRI examination revealed a disc herniation at the L5–S1 level on the left side, matching the symptoms of the patient. The quality of the imaging was poor, and coronal images were not available. Additionally, the voluminous disc herniation partially concealed the nerve root, making identification of the conjoined nerve difficult. There are numerous classification methods, the first presented 60 years ago by Cannon et al.12 The most cited classification is from Neidre and MacNab,18 which divides these anomalies into conjoined, abundant, and anastomotic roots. Recently, Burke et al.19 described 2 previously unclassified confluent root variants (Table 1), while Yu et al.20 added another confluent nerve variant, a root comprising 2 adjacent contributions that arise from the thecal sac. In our case, there was an additional L5 nerve root on the left side exiting to the same foramen, making it a type 2b case according to the Neidre and MacNab classification (Fig. 5). This anomaly intraoperatively reduced the available space over the disc, preventing us from removing the herniation. The surgical methods used until now include extended decompression of the (conjoined) nerve root (hemilaminectomy with unroofing of the lateral recess), foraminotomy, and in some cases partial facetectomy.1, 5, 8, 11, 21 Some of these methods can lead to instability of the spine and later to spinal fusion.22 Furthermore, in most cases, the disc herniation cannot be removed due to the special anatomy and the firmness and immobility of the nerve root(s),1, 11 especially in cases with an additional nerve root, resulting in a poor outcome.13 TABLE 1. The revised lumbar nerve root anomaly classification of Neidre and MacNab, according to Burke et al.

Main Type	Subtype	Description	
Type 1–conjoined	Type 1a	2 nerve roots that arise from a common dural sheath	
	Type 1b	2 nerve roots that arise close in the thecal sac, w/o a common dural sheath	
Type 2–redundant	Type 2a	No extra nerve root, 1 neural exit foramen w/o nerve root	
	Type 2b	Extra nerve root, all foramina contain nerve root(s)	
Type 3–anastomotic		Normal adjacent nerve roots but connected by vertical segment	
Type 4–confluent		2 contributions from 2 adjacent nerve roots arising from the thecal sac, coalescing to form a single nerve root that exits foramen	
Neidre and MacNab, 198318 and Burke et al., 2013.19

Lessons

We performed a standard, minimally invasive, microscope-assisted discectomy with a 3-cm-long incision and a tubular retractor.24 This method provides a good overview of the nerve structures and enough space to move with the instruments. The contralateral discectomy is not a new method; however, it is mostly used for minimally invasive intra- and extraforaminal disc herniations.24–26 In cases with typical anatomy, there is usually no need to approach the herniation from the contralateral side, mainly due to the limited view, which increases the risk of complications. However, in cases similar to ours, it can be very advantageous. Without the need to remove the facet joints or go far laterally with the decompression, the stability of the spine can be preserved while the disc herniation can be completely removed. If the hemilaminectomy of the contralateral side reaches slightly over the midline, the thecal sac can be mobilized medially, providing excellent space and visual contact of the disc herniation and minimizing the perioperative risk. Especially in cases with hardened subligamentous disc herniation, the extra space can be very convenient for the surgeon, as some fragments cannot simply be pulled out but have to be removed with a Kerrison rongeur or diamond burr drill. On the other hand, in cases with a soft disc herniation, a hemilaminectomy up to the midline is usually adequate.

The method does have some limitations. The contralateral approach is indicated for medial or mediolateral disc herniations. A far lateral or intraforaminal disc herniation will not be accessible from the contralateral side. Furthermore, it is not always possible to identify the root anomaly before surgery in order to choose the contralateral approach from the beginning. This can lead to bilateral hemilaminectomy, which means more scar tissue on both sides and, when a complete bilateral hemilaminectomy is performed, eventual instability of the spine. Still, this method is a good alternative to the classic approach and maximizes the success rate in difficult cases by offering a generous decompression.

In sum, a disc herniation affecting a conjoined nerve is a complex condition, and the proper diagnosis of this anatomical particularity is of the utmost importance. Thin coronal T2-weighted MRI sequences demonstrate, in our opinion, the highest diagnostic precision. If they are not available, a careful study of the axial and sagittal images can be adequate as well. Nonetheless, identification of the anomaly is not always possible before surgery. Discectomy in patients with a conjoined nerve root can be technically challenging, often with unsatisfactory results. An additional nerve root can hinder the removal of the disc herniation, leading to more precarious attempts to solve the problem. In our case, we used a novel surgical approach, performing a discectomy from the contralateral side of the herniation, and achieved good results. More experience with this approach in cases with conjoined nerves should be gathered.

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: both authors. Acquisition of data: Trakolis. Analysis and interpretation of data: Trakolis. Drafting the article: Trakolis. Critically revising the article: both authors. Reviewed submitted version of manuscript: both authors. Approved the final version of the manuscript on behalf of both authors: Trakolis.

Correspondence

Leonidas Trakolis: St. Luke Hospital, Thessaloniki, Greece. leonidastra86@hotmail.com.
==== Refs
References

1. Lotan R Al-Rashdi A Yee A Finkelstein J . Clinical features of conjoined lumbosacral nerve roots versus lumbar intervertebral disc herniations. Eur Spine J. 2010;19 (7 ):1094-1098.20602242
2. Trimba R Spivak JM Bendo JA . Conjoined nerve roots of the lumbar spine. Spine J. 2012;12 (6 ):515-524.22749652
3. Song SJ Lee JW Choi JY , et al. Imaging features suggestive of a conjoined nerve root on routine axial MRI. Skelet Radiol. 2008;37 (2 ):133-138.
4. Haijiao W Koti M Smith FW Wardlaw D . Diagnosis of lumbosacral nerve root anomalies by magnetic resonance imaging. J Spinal Disord. 2001;14 (2 ):143-149.11285427
5. Böttcher J Petrovitch A Sörös P Malich A Hussein S Kaiser WA . Conjoined lumbosacral nerve roots: current aspects of diagnosis. Eur Spine J. 2004;13 (2 ):147-151.14634853
6. Cail WS Butler AB . Conjoined lumbosacral nerve roots. Diagnosis with metrizamide myelography. Surg Neurol. 1983;20 (2 ):113-119.6879407
7. Kang CH Shin MJ Kim SM , et al. Conjoined lumbosacral nerve roots compromised by disk herniation: sagittal shoulder sign for the preoperative diagnosis. Skelet Radiol. 2008;37 (3 ):225-231.
8. Taghipour M Razmkon A Hosseini K . Conjoined lumbosacral nerve roots: analysis of cases diagnosed intraoperatively. J Spinal Disord Tech. 2009;22 (6 ):413-416.19652567
9. Scuderi GJ Vaccaro AR Brusovanik GV Kwon BK Berta SC. Conjoined lumbar nerve roots: a frequently underappreciated congenital abnormality. J Spinal Disord Tech. 2004;17 (2 ):86-93.15260089
10. Can H Kircelli A Kavadar G , et al. Lumbosacral conjoined root anomaly: anatomical considerations of exiting angles and root thickness. Turk Neurosurg. 2017;27 (4 ):617-622.27593795
11. Kuroki H Nagai T . Conjoined nerve root in a patient with lumbar disc herniation accompanied by a lumbosacral spine anomaly: a case report. J Med Case Rep. 2023;17 (1 ):1-8.36597169
12. Cannon BW Hunter SE Picaza JA . Nerve-root anomalies in lumbar disc surgery. J Neurosurg. 1962;19 (3 ):208-214.13876232
13. White JG Strait TA Binkley JR Hunter SE . Surgical treatment of 63 cases of conjoined nerve roots. J Neurosurg. 1982;56 (1 ):114-117.7054404
14. Hashimoto M Watanabe O Hirano H . Extraforaminal stenosis in the lumbosacral spine. Efficacy of MR imaging in the coronal plane. Acta Radiol. 1996;37 (5 ):610-613.8915261
15. Artico M Carloia S Piacentini M , et al. Conjoined lumbosacral nerve roots: observations on three cases and review of the literature. Neurocirugia (Astur). 2006;17 (1 ):54-59.16565781
16. Lightsey HM Xiong GX Schoenfeld AJ Simpson AK . Microendoscopic decompression of conjoined lumbosacral nerve roots. BMJ Case Rep. 2022;15 (3 ):248680.
17. Ogon M Goebel WE Trappe AE . Recurrent sciatica caused by “conjoined nerve roots”. Diagnosis, therapy, follow-up. Article in German. Nervenarzt. 1991;62 (6 ):378-382.1831545
18. Neidre A MacNab I . Anomalies of the lumbosacral nerve roots. Review of 16 cases and classification. Spine (Phila Pa 1976). 1983;8 (3 ):294-299.6623195
19. Burke SM Safain MG Kryzanski J Riesenburger RI . Nerve root anomalies: implications for transforaminal lumbar interbody fusion surgery and a review of the Neidre and Macnab classification system. Neurosurg Focus. 2013;35 (2 ):E9.
20. Yu C Zhengqi C Xiuchun Y . An amendment to the Neidre and MacNab classification system for lumbosacral nerve root anomaly and its implication in percutaneous endoscopic lumbar discectomy. World Neurosurg. 2018;111 :16-21.29233749
21. Epstein JA Carras R Ferrar J Hyman RA Khan A . Conjoined lumbosacral nerve roots: management of herniated discs and lateral recess stenosis in patients with this anomaly. J Neurosurg. 1981;55 (4 ):585-589.7277006
22. Ahuja S Moideen AN Dudhniwala AG Karatsis E Papadakis L Varitis E . Lumbar stability following graded unilateral and bilateral facetectomy: a finite element model study. Clin Biomech (Bristol Avon). 2020;75 :105011.32335473
23. Caspar W. A new surgical procedure for lumbar disc herniation causing less tissue damage through a microsurgical approach. In: Wüllenweber R , Brock M , Hamer J , Klinger M , Spoerri O , eds.Lumbar Disc Adult Hydrocephalus. Advances in Neurosurgery. Vol 4. Springer; 1977.
24. Yeom KS Choi YS . Full endoscopic contralateral transforaminal discectomy for distally migrated lumbar disc herniation. J Orthop Sci. 2011;16 (3 ):263-269.21442187
25. Jha RT Syed HR Catalino M Sandhu FA . Contralateral approach for minimally invasive treatment of upper lumbar intervertebral disc herniation: technical note and case series. World Neurosurg. 2017;100 :583-589.28137544
26. Yeom JS Kim KH Hong SW , et al. A minimally invasive technique for L5–S1 intraforaminal disc herniations: microdiscectomy with a tubular retractor via a contralateral approach. J Neurosurg Spine. 2008;8 (2 ):193-198.18248293
