Abstract

BackgroundFar lateral disc herniation (FLDH) constitutes a minor portion of the total discectomy workload for spine surgeons. So far, there is still a debate about the term “extreme lateral,” and in general, it describes the intra - and extraforaminal position of the disc herniation. We present a surgical treated case series in which the disc herniation on the lumbar spine was still ventral of the exiting nerve root far outside of the foramen.

MethodsStudy Design and Patient Characteristics: retrospective analysis of 14 surgical treated patients. Surgical Technique: In all patients, the so-called foraminal retreat maneuver (percutaneous endoscopic lumbar discectomy) was performed. A foraminoscope with a 15° optic orientation and a nonbeveled working sleeve were used in all cases. The aforementioned technique represents a modification of the “inside-out” endoscopic surgery on the lumbar spine.

ResultsWe treated 11 male and 3 female patients with an average age of 67 years and 66 years, respectively. Except for one, 13 patients presented with clear monoradicular symptoms accompanied by mild-to-moderate neurological deficits. In 11 cases, the disc herniation exhibited cranial migration; two were at the disc level, and in another case, caudal migration was observed. Immediate pain relief and significant improvement of neurological symptoms occurred in all patients. Two patients developed neuropathic pain, which improved after conservative treatment within 6 weeks following the procedure. No recurrence was observed in this case series.

ConclusionPatients suffering from extreme lateral lumbar disc herniation were found to be significantly older. Furthermore, there is a higher tendency toward male patients and cranial migration of the herniation. The described and modified inside-out technique, along with a 15° optic, allows for clear identification of the exiting nerve root and safe removal of the displaced disc herniation far outside of the spinal canal and foramen. No complications occurred in this small series, and the development of neuropathic pain appears to be relatively common.

Keywords: Endoscope, Extreme lateral, Lumbar disc herniation, Transforaminal

INTRODUCTION

In 1974, Abdullah et al. were the first to describe an extreme lateral lumbar disc herniation.[ 1 ] The diagnosis was confirmed by discography, with the herniation located within the foramen. With the advent of computed tomography (CT) and magnetic resonance imaging (MRI), further case reports detailing more lateral extraforaminal localization were published.[ 8 , 27 ] Nowadays, the term “extreme lateral” is used for both intra- and extraforaminal disc herniation. We propose that the term “extreme lateral” should be reserved for lumbar sequestration lying extraforaminal and anterior to the exiting nerve root [ Figure 1 ].

Figure 1:

(a,b): White arrows show the extreme lateral position of the disc herniation at the disc level or with cranial migration.

At present, there are no case series or research articles in the common and recent literature addressing this specific type of lumbar disc herniation. Far lateral disc herniation (FLDH) constitutes a minor portion of the total discectomy workload for spine surgeons. The overall incidence ranged from 3% to 12% of all lateral disc herniation (LDH).[ 4 , 19 ] Due to their different anatomical positioning compared to the more common paramedian disc herniation, the surgical procedures involved in releasing the neural compression caused by FLDHs are often challenging and frustrating to most spine surgeons, resulting in suboptimal outcomes for the patient. This is related to the higher risk of spinal instability from facet joint disruption and may even be associated with nerve root injury.[ 2 ]

Far lateral LDH presents with some unique clinical features. First, it often occurs in older patients, with a peak age in the sixth decade.[ 19 , 23 ] It usually has a more acute onset and causes more severe radicular pain due to direct pressure on the dorsal root ganglion.[ 20 ] Furthermore, it occurs more frequently at the upper lumbar levels and is commonly associated with intracanalicular LDH or stenosis.[ 23 ] Finally, the surgical outcomes of foraminal or far lateral LDH are less favorable than those of central or subarticular LDH.[ 3 ]

MATERIALS AND METHODS

Study design and patient characteristics

Retrospective analysis of 14 surgical treated patients (from May 2016 to April 2024). All patients provided informed consent to be included in this case series, and all of them, the same surgical technique was applied. Imaging findings of all patients and the diagnosis of an extreme lateral disc herniation are documented in Figure 2 .

Figure 2:

(a-v): Imaging findings of the surgical treated patients. The locations of sequestered discs in radiological images are shown with white, blue, and red arrows.

Surgical technique

The surgical intervention employed percutaneous endoscopic lumbar discectomy. In all patients, the so-called foraminal retreat maneuver was performed.[ 12 ]

Surgical technique steps:

The procedures were performed with the patients under general anesthesia in the prone position with slightly flexed hips and knees on the Wilson frame. Nerve root monitoring through free-run electromyography (EMG) or stimulated EMG was done sometimes but not routinely.[ 24 ]

Figure 3:

(a-c) Intraoperative X-ray documentation of the foraminal retreat maneuver starting in the center of the disc.

Figure 4:

(a) Endoscopic view of the Kambin triangle after resection of soft tissue, (b) mobilizing the cranial migrated disc herniation with a hook and (c) released exiting nerve root covering the concavity of the lateral vertebral body.

RESULTS

The distribution along the lumbar spine was as follows: two patients at L5/S1, eight patients at L4/5, three patients at L3/4, and finally, one patient at L2/3. We treated 11 male and 3 female patients with an average age of 67 years and 66 years, respectively. Except for one,[ 14 ] 13 patients presented with clear monoradicular symptoms accompanied by mild-to-moderate neurological deficits. In eleven cases, the disc herniation exhibited cranial migration; two were at the disc level, and in one further case, caudal migration was observed [ Figure 5 ].

Figure 5:

(a-d) Extreme rare case of extraforaminal caudal migration L4/5. Caudal orientation of the working sleeve and the endoscope. White arrows in a-c show the sequestered disc.

Immediate pain relief and significant improvement of neurological symptoms occurred in all patients. Two patients developed neuropathic pain, which improved after conservative treatment within 6 weeks following the procedure. No recurrence was observed in this case series [ Table 1 ].

Table 1:

Patient characteristics, clinical and imaging findings.

Patient No. 12 was suffering from acute left leg pain and L5 radiculopathy, followed by mild neurological deficits. MRI in the disc level L4/5 was inconspicuous, and in axial T2 weight images, a presacral luxation was supposed. The diagnosis was confirmed by discography with connected CT of the lumbosacral level, followed by multiplanar reconstruction in the selected bone window [ Figure 6 ].

Figure 6:

(a-c) Diagnosis of presacral luxation of a sequester (white arrows) on figures a,b,c, was confirmed by CT-discography with positive radiography of the displaced and compressed L5 - nerve root (red arrow) on figure c.

DISCUSSION

FLDH is defined as a disc herniation located on the sagittal plane laterally to the medial wall of the pedicle.[ 1 , 6 ] This definition is also made as extra-canalicular, extreme lateral, and extraforaminal lumbar disc herniation (ELDH) and describes the same pathology.[ 15 ] The latter types of herniation ELDH are responsible for nerve root compression at the level of or beyond the dorsal ganglion, where the root emerges from the foraminal canal. Assessing the precise position of the disc herniation beyond the foramen is important for surgeons who must choose the appropriate surgical approach. However, there are difficulties in making a correct diagnosis before surgery because careful observations of the extraforaminal zone are often lacking, and the extent of scanning (MRI, CT) on the sagittal plane and slice thickness of the axial plane is limited. Moreover, a coexisting intraspinal pathology can obscure a diagnosis of far lateral entrapment of the lumbar spinal nerve. Furthermore, there are no reports on the characteristics and reliable MRI findings of extraforaminal disc herniation.[ 15 ] In a case series of 18 patients, Kaya et al. found that a total of 15 (84%) patients had upper migration, and three (16%) had FLDH in the disc distance. A distinction between intraforaminal and extraforaminal was not made, and a microsurgical midline approach treated all patients. In the case of cranial migration, the lateral surface of the pars interarticularis was drilled.[ 10 ] A clear anatomical division of the extraforaminal zone anterior to the exiting nerve root is also missing, and the migration of the fragments is observed to be toward the psoas muscle.[ 21 ] Very rarely, these dislocations can mimic an abscess within the psoas muscle.[ 9 ]

Nowadays, the transforaminal endoscopic, percutaneous discectomy method is becoming increasingly widespread. Successful results are reported with this minimally invasive technique.[ 16 , 18 , 19 ] Its popularity is increasing with its short operation time, low bleeding, shorter postoperative recovery period, low complications, and high success rates. In addition, it has been suggested as an effective and reliable method in patients with recurrent lumbar disc herniation who require surgical treatment and do not have segmental instability.[ 16 ]

In a summary of surgical treated far lateral lumbar disc herniation reported as suspicious for nerve sheath tumors, Uy BR et al. presented two own cases and five separate published case reports. In three of them, the dorsal approach was chosen, and a hemilaminectomy paired with a complete facetectomy was performed. In two cases, transposase access in a lateral decubitus position was elected, and finally, in two patients, an anterior transperitoneal or retroperitoneal approach was selected.[ 26 ] The anterior transperitoneal approach was done in a female patient with an extreme lateral presacral disc herniation L5/S1, very similar to our patient number 12.[ 11 ] In another publication on ELDH at L5/S1 with caudal migration, the presacral L-5 root was explored through a microsurgical lateral extraforaminal transmuscular approach.[ 25 ] Although some scientific and technical descriptions in the literature on full endoscopic treatment of extreme lateral lumbar disc herniation can be found, details of different dislocations in the extraforaminal compartments are not taken into account.[ 5 , 17 , 28 ]

Paramedian lumbar disc herniations are generally reported in the 30–50 age range.[ 7 , 10 , 20 , 22 ] Patients suffering from extreme lateral lumbar disc herniation were found to be significantly older in parallel with our study.[ 7 , 10 , 19 ]

Limitations of this study include its retrospective nature. In addition, later examinations and a clinical follow-up of the patients were not carried out.

However, the technology described here allows different alignments of the working sleeves outside the foramen to secure the safe identification of the nerve roots and the unusually far lateral migrated sequester. In contrast to the very heterogeneous open surgical approaches, this presented percutaneous endoscopic technique is, to our knowledge, the first minimal invasive access dealing with very demanding and complex disc pathologies on the lumbar spine.

CONCLUSION

Patients suffering from extreme lateral lumbar disc herniation were found to be significantly older compared to the general occurrence in the population of symptomatic lumbar disc herniation. Furthermore, there is a higher tendency toward male patients and cranial migration of the herniation. The modified inside-out technique, described as the foraminal retreat maneuver, along with a 15° optic, allows for clear identification of the exiting nerve root and safe removal of the displaced disc herniation far outside of the spinal canal and foramen. No complications occurred in this small series, and the development of neuropathic pain appears to be relatively common. The distribution along the lumbar spine shows no major deviations.

Authors’ contributions

Luebbers and Baalmann performed the surgeries and collected data. They also discussed the technique. Ali and Kale summarized and discussed the clinical data.

Ethical approval

The Institutional Review Board approval is not required as it is retrospective study.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

Disclaimer

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.

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