Sequential Full-Endoscopic Decompression under Local Anesthesia for Concurrent L4/5 Lateral Recess and L5/S1 Foraminal Stenosis Due to Stable Isthmic Spondylolisthesis: A Case Report

Abstract

Isthmic spondylolisthesis at the L5-S1 level frequently leads to foraminal stenosis, while degenerative changes often cause lumbar spinal canal stenosis at L4-5. When both conditions coexist, accurate identification of the symptomatic lesion is challenging. Conventional surgical strategies typically involve combined decompression and interbody fusion under general anesthesia, which may not be suitable for elderly or high-risk patients. Recent advances in full-endoscopic spine surgery performed under local anesthesia provide a minimally invasive alternative. In this report, we present the case of a 75-year-old man with L5 radiculopathy in whom magnetic resonance imaging demonstrated right-sided lateral recess stenosis at L4-5 and right-sided foraminal stenosis at L5-S1 due to stable isthmic spondylolisthesis. Two-stage full-endoscopic spine surgery was performed under local anesthesia. The first procedure involved transforaminal pars crisscross decompression at L5-S1. Although foraminal decompression was achieved, symptoms persisted. A second-stage full-endoscopic ventral facetectomy at L4-5 resulted in immediate resolution of his symptoms. The patient remained asymptomatic at the 3-month follow-up. This case highlights the feasibility and efficacy of sequential full-endoscopic decompression under local anesthesia for multilevel lumbar stenosis associated with L5 radiculopathy. This approach may serve as a safe, less invasive alternative to fusion surgery in elderly patients and those with significant comorbidities.

Introduction

Lumbar spinal stenosis is a prevalent degenerative condition in the elderly population and often results in neurogenic claudication or radiculopathy. Among its subtypes, lumbar spinal canal stenosis at L4-5 and foraminal stenosis at L5-S1, particularly in the context of isthmic spondylolisthesis, represent a common but diagnostically challenging combination. The overlapping clinical symptoms due to compression of the L5 nerve root at both sites complicate the identification of the primary symptomatic lesion. Traditionally, surgical treatment for such dual-level pathology involves posterior decompression at L4-5 and interbody fusion at L5-S1, typically performed under general anesthesia. While effective, this approach may be unsuitable for patients who are elderly or those with significant comorbidities due to increased perioperative risks.

Recent advances in minimally invasive spine surgery, particularly full-endoscopic spinal surgery (FESS), have expanded therapeutic options for these patients. FESS performed under local anesthesia via a transforaminal approach offers targeted decompression with minimal disruption to surrounding tissue. Several techniques have shown promise in this setting, including full-endoscopic ventral facetectomy (FEVF) for lateral recess stenosis¹⁾ and, more recently, pars crisscross decompression for foraminal stenosis associated with stable isthmic spondylolisthesis at L5.²⁾

This report describes a case of L5 radiculopathy caused by coexisting spinal canal stenosis at L4-5 and foraminal stenosis at L5-S1. The patient was successfully treated using a 2-stage FESS procedure under local anesthesia. This case highlights the feasibility and effectiveness of endoscopic decompression in the management of multilevel lumbar pathology without the need for fusion or general anesthesia.

Case Report

Clinical history

A 75-year-old man presented with a 10-year history of progressive lower back pain and right leg pain. His past medical history included Buerger's disease, hypertension, and bronchial asthma. Despite long-term conservative management, including pharmacological therapy and physiotherapy, his symptoms persisted and progressively worsened.

Neurological examination revealed mild weakness in the right extensor hallucis longus muscle (manual muscle test grade 4/5). The straight leg raise test was positive at 80° on the right side and negative on the left. No bladder or bowel dysfunction was noted. Hypoesthesia was observed in the L5 dermatome on the right. A diagnostic right L5 nerve root block resulted in reproducible and temporary pain relief, indicating L5 radiculopathy.

Radiographic findings

A computed tomography (CT) scan of the patient's lumbar spine confirmed bilateral pars interarticularis defects at L5 vertebra (Fig. 1). Magnetic resonance imaging (MRI) demonstrated spinal canal stenosis, including right lateral recess stenosis at L4-5 and right-sided foraminal stenosis at L5-S1 associated with isthmic spondylolisthesis at L5 (Fig. 2). Dynamic lateral radiographs in flexion and extension revealed no significant intervertebral motion at L5-S1, consistent with a diagnosis of stable isthmic spondylolisthesis.

Fig. 1.

Preoperative CT scans demonstrating isthmic spondylolisthesis at L5 and foraminal stenosis at L5-S1. (A) Right para-sagittal CT scan showing anterior slippage of L5 and pars defects. (B) Axial CT scan at the L4-5 level. (C) Axial CT scan at the L5-S1 level. (D) Three-dimensional posterolateral view showing pars defects (red arrow).

CT: computed tomography

Fig. 2.

Preoperative findings on MRI. (A) T2-weighted mid-sagittal MRI scan indicating spinal canal stenosis at L4-5. (B) Axial MRI scan at the L4-5 level showing right-sided lateral recess stenosis. (C) T2-weighted right para-sagittal MRI indicating foraminal stenosis at L5-S1 (white arrow). (D) Axial MRI scan at the L5-S1 level showing right-sided foraminal stenosis.

MRI: magnetic resonance imaging

Surgical intervention

Given the patient's systemic comorbidities, including asthma, and his desire to avoid general anesthesia and spinal fusion, we proposed a 2-stage minimally invasive decompression strategy using transforaminal FESS under local anesthesia. Both the L4-5 lateral recess stenosis and the L5-S1 foraminal stenosis were considered potential causes of the L5 symptoms. However, imaging findings suggested that the stenosis was more severe at the L5-S1 level; and thus, this level was prioritized for treatment.

In the first stage, we performed transforaminal full-endoscopic pars crisscross decompression at the L5-S1 level with the patient in the prone position. First, 1% lidocaine was injected for local anesthesia in the skin, subcutaneous tissue, fascia, and soft tissue near the pars defect and on the surface of the disc. Next, an 8-mm cannula was placed at the superior articular process (SAP) of S1. After removal of the soft tissue, the pars crisscross became visible. The pars crisscross includes the SAP of S1, the floating lamina, the inferior articular process (IAP) of L4, and the ragged edge of the pars. By resecting these in sequence, decompression of the exiting L5 nerve root was confirmed intraoperatively from the inlet to the outlet of the foramen. The operative time was 95 mins, blood loss was minimal, and ambulation was initiated 2 hrs postoperatively. However, the patient experienced persistent right leg pain despite technically successful decompression. Postoperative MRI and CT scans demonstrated adequate foraminal enlargement (Fig. 3).

Fig. 3.

Endoscopic view after pars crisscross decompression and postoperative scans. (A) Intraoperative endoscopic view after decompression. The exiting L5 nerve root was decompressed from the inlet to the outlet of the intervertebral foramen at L5-S1 on the right. (B) Postoperative T2-weighted right para-sagittal MRI demonstrating decompression of intervertebral foramen at L5-S1 compared with the preoperative image (white arrow). (C) Postoperative axial CT scan confirming enlargement of the foramen (red circle). (D) Postoperative sagittal CT scan showing bony resection around the L5-S1 foramen on the right. (E) Three-dimensional CT scan obtained postoperatively. The red line indicates the resected area.

CT: computed tomography; MRI: magnetic resonance imaging

Three months later, a second-stage decompression was performed using FEVF at L4-5. Because the patient strongly preferred surgery under local anesthesia, FEVF―which can be performed under local anesthesia―was selected instead of interlaminar decompression, which requires general anesthesia. After adequate local anesthesia, a small skin incision was made 80 mm lateral to the midline. An 8-mm cannula was placed at the SAP of L5. After partial resection of the SAP and ventral portion of the IAP, flavectomy was performed to decompress the traversing right L5 nerve root. Complete decompression was confirmed intraoperatively. The operative time was 103 mins, blood loss was minimal, and ambulation was initiated 2 hrs postoperatively. The patient's right leg pain resolved immediately following the second surgery. Postoperative MRI and CT scans confirmed adequate decompression of the right lateral recess (Fig. 4). There were no intraoperative or postoperative complications. At the 3-month follow-up, the patient remained symptom-free and had returned to his normal daily activities.

Fig. 4.

Endoscopic view after full-endoscopic ventral facetectomy and postoperative scans. (A) Intraoperative endoscopic image showing a decompressed right traversing L5 nerve root. (B) Postoperative axial T2-weighted MRI at the L4-5 level demonstrating decompression of the right lateral recess compared with the preoperative image. (C) Postoperative axial CT scan confirming resection of the superior articular process at L5 and the ventral portion of the inferior articular process at L4 (ventral facetectomy). (D) Postoperative sagittal CT scan showing bony resection around the L4-5 foramen and lateral recess on the right. (E) Postoperative three-dimensional CT scan. The red line indicates the resected area.

CT: computed tomography; MRI: magnetic resonance imaging

Discussion

Isthmic spondylolisthesis occurs most often at the L5-S1 level and is frequently associated with intervertebral foraminal narrowing, often resulting in L5 radiculopathy. Foraminal stenosis tends to worsen as slippage progresses or disc height decreases, creating complex patterns of nerve root compression that are difficult to localize. Jo et al.³⁾ evaluated 46 patients with L5 isthmic spondylolisthesis and found that approximately 61% had severe foraminal stenosis on MRI, highlighting the anatomical vulnerability of the L5-S1 foramen in this condition. Identification of the culprit lesion becomes particularly challenging when lateral recess stenosis at L4-5 coexists with foraminal stenosis at L5-S1 on the same side, since both are capable of compressing the L5 nerve root at different anatomical levels. This anatomical overlap complicates surgical decision-making, especially when both lesions are radiographically significant.

To assist in localizing the culprit lesion in L5 radiculopathy, several studies have explored the diagnostic value of superficial peroneal nerve-sensory nerve action potential (SPN-SNAP). In a study of patients with L5 radiculopathy by Ando et al.⁴⁾ found that the amplitude of SPN-SNAP was significantly smaller in the group with foraminal stenosis at L5-S1 than in the group with spinal canal stenosis at L4-5. This finding suggests that SPN-SNAP could serve as a supportive tool for detecting postganglionic L5 root compression, particularly in patients with foraminal stenosis. However, in a study of individuals over the age of 60 years, Ho et al.⁵⁾ found no significant difference in the proportion with reduced SPN-SNAP amplitude between a healthy control group (27.3%) and a group with L5 radiculopathy (31.8%). These findings highlight the fact that a reduction in SPN-SNAP amplitude alone may lack sufficient specificity for diagnosing L5 radiculopathy in elderly patients. Therefore, it should not be used as a sole diagnostic criterion but rather interpreted cautiously in conjunction with imaging and clinical findings. Furthermore, population-based data show a limited correlation between imaging severity and clinical symptoms. For example, the Wakayama Spine Study found that only 17.5% of individuals with severe central stenosis on MRI were clinically symptomatic, underscoring the need for comprehensive functional assessment rather than reliance solely on imaging.⁶⁾

There is still no definitive method to identify a single causative lesion when both lateral recess stenosis at L4-5 and foraminal stenosis at L5-S1 are present. In conventional non-endoscopic surgery, performing a 1-stage procedure typically requires a highly invasive 2-level operation under general anesthesia, combining decompression at L4-5 and lumbar interbody fusion at L5-S1. Alternatively, if each level is addressed separately, the patient must undergo 2 sessions of general anesthesia.

FESS under local anesthesia has recently emerged as a minimally invasive alternative for treating multilevel lumbar pathology. Several transforaminal techniques expand the available endoscopic procedures for such complex scenarios. These include full-endoscopic lumbar foraminoplasty for foraminal stenosis,⁷⁾ FEVF for lateral recess stenosis,¹⁾ total endoscopic lumbar undercutting laminectomy for central canal stenosis,⁸⁾ and pars crisscross decompression.²⁾ FEVF, as described by Sairyo et al.,¹⁾ enables decompression of lateral recess stenosis via a transforaminal approach under local anesthesia through resection of the SAP, the ventral portion of the IAP, and the ligamentum flavum over the traversing nerve root.

Pars crisscross decompression is specifically designed to treat foraminal stenosis associated with stable isthmic spondylolisthesis at L5. The procedure involves sequential resection of the SAP at S1, the floating lamina, the IAP at L4, and the ragged edge of the pars defect, allowing complete visualization and decompression of the exiting L5 nerve root.²⁾ Kanda et al.⁹⁾ reported that 6 patients treated with pars crisscross decompression for adult-onset stable isthmic spondylolisthesis had good outcomes during a 3-month follow-up period. In the present case, both lesions were treated sequentially using these 2 techniques. The patient first underwent pars crisscross decompression for L5-S1 foraminal stenosis, followed by FEVF for residual lateral recess stenosis at L4-5. This staged strategy allowed targeted, level-specific decompression under local anesthesia with complete resolution of symptoms.

Nakajima et al.¹⁰⁾ described a similar staged full-endoscopic approach for treatment of foraminal stenosis at L5-S1 and lateral recess stenosis at L4-5, although there were no isthmic defects in their case. To our knowledge, the present case report is the first to describe staged full-endoscopic decompression under local anesthesia performed specifically for L5 radiculopathy caused by foraminal stenosis at L5-S1 in the setting of isthmic spondylolisthesis.

Another advantage of the full-endoscopic staged approach is that it does not require general anesthesia. This is particularly relevant for patients who are elderly or frail. Chung et al.¹¹⁾ reported a 26.4% complication rate and 6.7% mortality rate in patients over 80 years of age who underwent surgery under general anesthesia, with respiratory problems being the most frequent complications.

Overall, our case demonstrates that full-endoscopic staged decompression under local anesthesia is a safe, effective, and minimally invasive alternative to traditional fusion surgery in selected patients with multilevel lumbar stenosis and L5 radiculopathy. However, prospective studies are needed to confirm its long-term efficacy and to establish clear indications.

This case further demonstrates that transforaminal FESS performed under local anesthesia can be a safe and effective treatment option for multilevel lumbar pathology, including concurrent spinal canal stenosis at L4-5 and foraminal stenosis at L5-S1 attributable to stable isthmic spondylolisthesis. The use of transforaminal endoscopic pars crisscross decompression and FEVF allowed for adequate neural decompression without the need for general anesthesia or instrumented fusion.

For patients with significant medical comorbidities and for those who wish to avoid fusion surgery, staged endoscopic decompression provides a minimally invasive and functionally favorable alternative. This approach may be especially valuable in older patients, in whom surgical invasiveness and anesthesia-related risks must be minimized. Further studies in larger cohorts with longer follow-up periods are warranted to determine the long-term outcomes and precise indications for these techniques.

Conflicts of Interest Disclosure

All authors have no conflict of interest.

Informed Consent

Informed consent for publication was obtained from the patient.