The Surgical Resection of Brainstem Glioma: Outcomes and Prognostic Factors

BACKGROUND

The management of brainstem glioma remains controversial, with increasing evidence supporting surgical resection as the primary treatment for a select subgroup of tumors. However, there remains no consensus on the specific benefits and risks, the selection of surgical candidates, and prognostic factors that may further refine surgical indications.

METHODS

A retrospective single-surgeon chart review was performed for all patients who underwent surgical treatment for radiographically suspected brainstem glioma between 2000 and 2017. Preoperative and postoperative radiographic evaluations on magnetic resonance imaging were conducted. Survival outcomes were collected, and machine-learning techniques were used for multivariate analysis.

RESULTS

Seventy-seven patients with surgical treatment of brainstem glioma were identified, with a median age of 9 years (range, 0-58 years). The cohort included 64% low-grade (I and II) and 36% high-grade (III and IV) tumors. For all patients, the 1-year and 5-year overall survival were 76.4% and 62.3%, respectively. Transient neurologic deficit was present in 34% of cases, and permanent deficit in a further 29%.

CONCLUSIONS

The radical surgical resection of brainstem gliomas can be performed with acceptable risk in well-selected cases and likely confers survival advantage for what is otherwise a rapidly and universally fatal disease. Various radiographic features are useful during patient selection and may guide treatment selection.

Rate-controlled intraventricular endoscopic irrigation via bipolar foot pedal activation: technical note

Irrigation during intraventricular endoscopic surgery is critical for visualization, with normal intracranial pressure maintained by balancing fluid ingress and egress. Although irrigation is typically achieved through manual manipulation of inexact stopcocks, the authors have developed a rate-controlled, foot pedal-activated system for precise intraventricular irrigation by using a standard irrigating bipolar electrocautery machine.This study is a retrospective review of patients who underwent endoscopic intraventricular surgery between January 1, 2018, and September 25, 2019, in which this irrigation system was used. Important components of this system include a bipolar module irrigation regulator that is set to a desired rate, a secure connection of the bipolar irrigation tubing to the endoscope, and one or more open egress ports on the endoscope for passive fluid drainage. Nineteen consecutive patients were identified on review (average age ± SD, 4.3 ± 4.1 years). Procedures performed included third ventriculostomies (n = 10); arachnoid/choroid cyst fenestrations/resections (n = 3); biopsy/tumor resection (n = 1); and combined procedures (n = 5). Foot pedal-controlled irrigation provided visualization of all intraventricular structures. A single operator was able to control the endoscope, endoscopic instruments, and irrigation, with assistance as indicated for more complex maneuvers. There were no perioperative complications. Because this setup is easily constructed from a standard irrigating bipolar machine, delivers precise irrigation flow rates, and facilitates a single-surgeon bimanual technique, these data support the utility of foot-controlled irrigation for endoscopic intraventricular surgery.

Keyhole retrosigmoid approach for large vestibular schwannomas: strategies to improve outcomes

OBJECTIVE There are numerous treatment strategies in the management for large vestibular schwannomas, including resection only, staged resections, resections followed by radiosurgery, and radiosurgery only. Recent evidence has pointed toward maximal resection as being the optimum strategy to prevent tumor recurrence; however, durable tumor control through aggressive resection has been shown to occur at the expense of facial nerve function and to risk other approach-related complications. Through a retrospective analysis of their single-institution series of keyhole neurosurgical approaches for large vestibular schwannomas, the authors aim to report and justify key techniques to maximize tumor resection and reduce surgical morbidity. METHODS A retrospective chart review was performed at the Centre for Minimally Invasive Neurosurgery. All patients who had undergone a keyhole retrosigmoid approach for the resection of large vestibular schwannomas, defined as having a tumor diameter of ≥ 3.0 cm, were included in this review. Patient demographics, preoperative cranial nerve status, perioperative data, and postoperative follow-up were obtained. A review of the literature for resections of large vestibular schwannomas was also performed. The authors' institutional data were compared with the historical data from the literature. RESULTS Between 2004 and 2017, 45 patients met the inclusion criteria for this retrospective chart review. When compared with findings in a historical cohort in the literature, the authors' minimally invasive, keyhole retrosigmoid technique for the resection of large vestibular schwannomas achieved higher rates of gross-total or near-total resection (100% vs 83%). Moreover, these results compare favorably with the literature in facial nerve preservation (House-Brackmann I-II) at follow-up after gross-total resections (81% vs 47%, p < 0.001) and near-total resections (88% vs 75%, p = 0.028). There were no approach-related complications in this series. CONCLUSIONS It is the experience of the senior author that complete or near-complete resection of large vestibular schwannomas can be successfully achieved via a keyhole approach. In this series of 45 large vestibular schwannomas, a greater extent of resection was achieved while demonstrating high rates of facial nerve preservation and low approach-related and postoperative complications compared with the literature.

Intraparenchymal extravasation of gadolinium mimicking an enhancing brain tumor

Gadolinium (Gd)-enhanced magnetic resonance imaging plays an essential role in the detection, characterization, and staging of intracranial neoplasms and vascular abnormalities. Although Gd is helpful in a majority of situations, it can lead to diagnostic misinterpretation in the setting of active vascular extravasation. Scarce reports of intracranial extravasation of Gd are present in the literature. Here, we report the first case of surgically proven spontaneous intraparenchymal extravasation of Gd mimicking an enhancing intra-axial neoplasm in a pediatric patient. Early and accurate recognition of Gd extravasation is critical in obtaining the accurate diagnosis and triaging patients expeditiously into proper avenues of care.

Surgical relevance of pediatric skull base maturation for the far-lateral and extreme-lateral infrajugular transcondylar-transtubercular exposure approaches

OBJECTIVE

Lesions of the foramen magnum, inferolateral-to-midclival areas, and ventral pons and medulla are often treated using a far-lateral or extreme-lateral infrajugular transcondylar-transtubercular exposure (ELITE) approach. The development and surgical relevance of critical posterior skull base bony structures encountered during these approaches, including the occipital condyle (OC), hypoglossal canal (HGC), and jugular tubercle (JT), are nonetheless poorly defined in the pediatric population.

METHODS

Measurements from high-resolution CT scans were made of the relevant posterior skull base anatomy (HGC depth from posterior edge of the OC, OC and JT dimensions) from 60 patients (evenly distributed among ages 0-3, 4-7, 8-11, 12-15, 16-18, and > 18 years), and compared between laterality, sex, and age groups by using t-tests and linear regression.

RESULTS

There were no significant differences in posterior skull base parameters by laterality, and HGC depth and JT size did not differ by sex. The OC area was significantly larger in males versus females (174.3 vs 152.2 mm2; p = 0.01). From ages 0-3 years to adult, the mean HGC depth increased 27% (from 9.0 to 11.4 mm) and the OC area increased 52% (from 121.4 to 184.0 mm2). The majority of growth for these parameters occurred between the 0-3 year and 4-7 year age groups. Conversely, JT volume increased nearly 3-fold (281%) from 97.4 to 370.9 mm3 from ages 0-3 years to adult, with two periods of substantial growth seen between the 0-3 to 4-7 year and the 12-15 to 16-18 year age groups. Overall, JT growth during pediatric development was significantly greater than increases in HGC depth and OC area (p < 0.05). JT volume remained < 65% of adult size up to age 16.

CONCLUSIONS

When considering a far-lateral or ELITE approach in pediatric patients, standard OC drilling is likely to be needed due to the relative stability of OC and HGC anatomy during development. The JT significantly increases in size with development, yet is only likely to need to be drilled in older children (> 16 years) and adults.

Pediatric Intracavernous Sinus Lesions: A Single Institutional Surgical Case Series and Review of the Literature

BACKGROUND

Pediatric intracavernous sinus tumors are exceedingly rare and thus poorly characterized. Their neurosurgical management is challenging and diagnostic, and management guidelines are limited.

OBJECTIVE

To report our institutional experience with the surgical resection of pediatric intracavernous sinus tumors. We also compare and contrast our results with the 14 cases of pediatric intracavernous sinus lesions in the current literature.

METHODS

A retrospective descriptive analysis of consecutive pediatric patients (ages 0-18 yr) presenting to our institution with a diagnosis of an intracavernous sinus lesion was performed. From January 2012 to January 2017, 5 cases were identified. Eleven patients with secondary invasion of the cavernous sinus (2 meningiomas, 7 pituitary adenomas) or dermoid tumors involving the cavernous sinus (2) were not included in our review.

RESULTS

Surgical resection via a frontotemporal orbitozygomatic approach was performed in all cases by a single senior neurosurgeon (M.L.). There were no perioperative or postoperative complications attributable to the surgery or approach. Four of 5 patients remained neurologically stable throughout the perioperative and postoperative period. The fifth patient had a complete resolution of their cranial neuropathies postoperatively. A pathological diagnosis that guided long-term management was obtained in all cases.

CONCLUSION

Neurosurgical management of pediatric cavernous sinus lesions can be safely performed and critically guide future therapies. Surgeon familiarity with cavernous sinus and skull-base anatomy is critical to the successful management of these patients. The benefits of surgery should be balanced against the potential complications and need for a tissue diagnosis in children. The senior author had a significant experience with cavernous sinus approaches in adults prior to initiating use of the approach in the pediatric population.

Endoscopic surgery for nonsyndromic craniosynostosis: a 16-year single-center experience

OBJECTIVE

In this paper the authors review their 16-year single-institution consecutive patient experience in the endoscopic treatment of nonsyndromic craniosynostosis with an emphasis on careful review of any associated treatment-related complications and methods of complication avoidance, including preoperative planning, intraoperative management, and postoperative care and follow-up.

METHODS

A retrospective chart review was conducted on all patients undergoing endoscopic, minimally invasive surgery for nonsyndromic craniosynostosis at Rady Children's Hospital from 2000 to 2015. All patients were operated on by a single neurosurgeon in collaboration with two plastic and reconstructive surgeons as part of the institution's craniofacial team.

RESULTS

Two hundred thirty-five patients underwent minimally invasive endoscopic surgery for nonsyndromic craniosynostosis from 2000 to 2015. The median age at surgery was 3.8 months. The median operative and anesthesia times were 55 and 105 minutes, respectively. The median estimated blood loss (EBL) was 25 ml (median percentage EBL 4.2%). There were no identified episodes of air embolism or operative deaths. One patient suffered an intraoperative sagittal sinus injury, 2 patients underwent intraoperative conversion of planned endoscopic to open procedures, 1 patient experienced a dural tear, and 1 patient had an immediate reexploration for a developing subgaleal hematoma. Two hundred twenty-five patients (96%) were admitted directly to the standard surgical ward where the median length of stay was 1 day. Eight patients were admitted to the intensive care unit (ICU) postoperatively, 7 of whom had preexisting medical conditions that the team had identified preoperatively as necessitating a planned ICU admission. The 30-day readmission rate was 1.7% (4 patients), only 1 of whom had a diagnosis (surgical site infection) related to their initial admission. Average length of follow-up was 2.8 years (range < 1 year to 13.4 years). Six children (< 3%) had subsequent open procedures for perceived suboptimal aesthetic results, 4 of whom (> 66%) had either coronal or metopic craniosynostosis. No patient in this series either presented with or subsequently developed signs or symptoms of intracranial hypertension.

CONCLUSIONS

In this large single-center consecutive patient series in the endoscopic treatment of nonsyndromic craniosynostosis, significant complications were avoided, allowing for postoperative care for the vast majority of infants on a standard surgical ward. No deaths, catastrophic postoperative morbidity, or evidence of the development of symptomatic intracranial hypertension was observed.

Extended middle fossa approach to lateralized pontine cavernomas in children

OBJECTIVE Treatment of hemorrhagic cavernous malformations within the lateral pontine region demands meticulous surgical planning and execution to maximize resection while minimizing morbidity. The authors report a single institution's experience using the extended middle fossa rhomboid approach for the safe resection of hemorrhagic cavernomas involving the lateral pons. METHODS A retrospective chart review was performed to identify and review the surgical outcomes of patients who underwent an extended middle fossa rhomboid approach for the resection of hemorrhagic cavernomas involving the lateral pons during a 10-year period at Rady Children's Hospital of San Diego. Surgical landmarks for this extradural approach were based on the Fukushima dual-fan model, which defines the rhomboid based on the following anatomical structures: 1) the junction of the greater superficial petrosal nerve (GSPN) and mandibular branch of the trigeminal nerve; 2) the lateral edge of the porus trigeminus; 3) the intersection of the petrous ridge and arcuate eminence; and 4) the intersection of the GSPN, geniculate ganglion, and arcuate eminence. The boundaries of maximal bony removal for this approach are the clivus inferiorly below the inferior petrosal sinus; unroofing of the internal auditory canal posteriorly; skeletonizing the geniculate ganglion, GSPN, and internal carotid artery laterally; and drilling under the Gasserian ganglion anteriorly. This extradural petrosectomy allowed for an approach to all lesions from an area posterolateral to the basilar artery near its junction with cranial nerve (CN) VI, superior to the anterior inferior cerebellar artery and lateral to the origin of CN V. Retraction of the mandibular branch of the trigeminal nerve during this approach allowed avoidance of the region involving CN IV and the superior cerebellar artery. RESULTS Eight pediatric patients (4 girls and 4 boys, mean age of 13.2 ± 4.6 years) with hemorrhagic cavernomas involving the lateral pons and extension to the pial surface were treated using the surgical approach described above. Seven cavernomas were completely resected. In the eighth patient, a second peripheral lesion was not resected with the primary lesion. One patient had a transient CN VI palsy, and 2 patients had transient trigeminal hypesthesia/dysesthesia. One patient experienced a CSF leak that was successfully treated by oversewing the wound. CONCLUSIONS The extended middle fossa approach can be used for resection of lateral pontine hemorrhagic cavernomas with minimal morbidity in the pediatric population.

Space-brain: The negative effects of space exposure on the central nervous system

Journey to Mars will be a large milestone for all humankind. Throughout history, we have learned lessons about the health dangers associated with exploratory voyages to expand our frontiers. Travelling through deep space, the final frontier, is planned for the 2030s by NASA. The lessons learned from the adverse health effects of space exposure have been encountered from previous, less-lengthy missions. Prolonged multiyear deep space travel to Mars could be encumbered by significant adverse health effects, which could critically affect the safety of the mission and its voyagers. In this review, we discuss the health effects of the central nervous system by space exposure. The negative effects from space radiation and microgravity have been detailed. Future aims and recommendations for the safety of the voyagers have been discussed. With proper planning and anticipation, the mission to Mars can be done safely and securely.

Phrenic nerve decompression for the management of unilateral diaphragmatic paralysis - preoperative evaluation and operative technique

Background:

Unilateral diaphragmatic paralysis (UDP) can be a very disabling, typically causing shortness of breath and reduced exercise tolerance. We present a case of a surgical decompression of the phrenic nerve of a patient who presented with UDP, which occurred following cervical spine surgery.

Methods:

The workup for the etiology of UDP demonstrated paradoxical movement on “sniff test” and notably impaired pulmonary function tests. Seven months following the onset of the UDP, he underwent a surgical decompression of the phrenic nerve at the level of the anterior scalene.

Results:

He noted rapid symptomatic improvement following surgery and reversal of the above noted objective findings was documented. At his 4-year follow-up, he had complete resolution of his clinical symptoms. Repeated physiologic testing of his respiratory function had shown a complete reversal of his UDP.

Conclusions:

Anatomical compression of the phrenic nerve by redundant neck vasculature should be considered in the differential diagnosis of UDP. Here we demonstrated the techniques in workup and surgical management, with both subjective and objective evidence of success.

Management of Through-and-Through Penetrating Skull Injury: A Railroad Spike That Transgressed the Anterior Skull Base

BACKGROUND

Penetrating injuries involving foreign objects that transgress the entirety of the human skull present challenges in the management of vascular injuries, infectious risk, cerebrospinal fluid leak, and cosmetic repair. Ultimately, effective management of these injuries requires a multidisciplinary team and judicious surgical planning.

CASE DESCRIPTION

Here we present the treatment of a patient who experienced a penetrating injury from a railroad spike, with entry and exit points involving the left and right anterior aspects of the temporal fossa, respectively.

CONCLUSIONS

The rationale for management decisions is reviewed in the context of the published literature.

Operative and Therapeutic Advancements in Breast Cancer Metastases to the Brain

Patients with breast cancer are surviving longer as the state of the art for care advances. Because patients are surviving longer with primary breast cancer, the incidence of secondary metastatic disease has risen. Metastatic breast cancer to the brain was once thought to be universally fatal. While it is still quite lethal, its treatment after diagnosis is increasingly safe and effective. Critical progress has been made in understanding the interaction between breast metastases and the neural niche, neuroimaging of functional anatomy, minimally invasive image-guided brain surgery, characterizing subtypes of breast cancer based on molecular and genetic profiles, and individualized pharmaceuticals and immunotherapies. In this review, we discuss recent advances that have brought us to state-of-the-art management of metastatic breast cancer to the brain.

Robot-assisted endoscopic third ventriculostomy: institutional experience in 9 patients

OBJECTIVE The endoscopic third ventriculostomy (ETV) is an established and effective treatment for obstructive hydrocephalus. In its most common application, surgeons plan their entry point and the endoscope trajectory for the procedure based on anatomical landmarks, then control the endoscope freehand. Recent studies report an incidence of neural injuries as high as 16.6% of all ETVs performed in North America. The authors have introduced the ROSA system to their ETV procedure to stereotactically optimize endoscope trajectories, to reduce risk of traction on neural structures by the endoscope, and to provide a stable mechanical holder of the endoscope. Here, they present their series in which the ROSA system was used for ETVs. METHODS At the authors' institution, they performed ETVs with the ROSA system in 9 consecutive patients within an 8-month period. Patients had to have a favorable expected response to ETV (ETV Success Score ≥ 70) with no additional endoscopic procedures (e.g., choroid plexus cauterization, septum pellucidum fenestration). The modality of image registration (CT, MRI, surface mapping, or bone fiducials) was dependent on the case. RESULTS Nine pediatric patients with an age range of 1.5 to 16 years, 4 girls and 5 boys, with ETV Success Scores ranging from 70 to 90, underwent successful ETV surgery with the ROSA system within an 8-month period. Their intracranial pathologies included tectal tumors (n = 3), communicating hydrocephalus from hemorrhage or meningeal disease (n = 2), congenital aqueductal stenosis (n = 1), compressive porencephalic cyst (n = 1), Chiari I malformation (n = 1), and pineal region mass (n = 1). Robotic assistance was limited to the ventricular access in the first 2 procedures, but was used for the entirety of the procedure for the following 7 cases. Four of these cases were combined with another procedural objective (3 stereotactic tectal mass biopsies, 1 Chiari decompression). A learning curve was observed with each subsequent surgery as registration and surgical times became shorter and more efficient. All patients had complete resolution of their preprocedural symptoms. There were no complications. CONCLUSIONS The ROSA system provides a stable, precise, and minimally invasive approach to ETVs.

Impact of ventricular-peritoneal shunt valve design on clinical outcome of pediatric patients with hydrocephalus: Lessons learned from randomized controlled trials

Hydrocephalus is one of the most common diseases managed by pediatric neurosurgeons. Cerebrospinal fluid (CSF) shunting has been the mainstay of durable treatment for hydrocephalus for many decades. There are two main categories of shunt designs for regulating the extent of CSF diversion: (1) Fixed-parameter valves and (2) adjustable valves. Furthermore, these valves can also function with and without an anti-siphon device. Here, we review randomized controlled trials (RCTs) that examined the impact of these valve designs on the clinical outcome of pediatric patients afflicted with hydrocephalus. All three RCTs suggested no significant differences in clinical outcome as a function of shunt design. Implications of these findings are discussed.

Do corticosteroids play a role in the management of traumatic brain injury?

Neuroprotective strategies for the medical management of traumatic brain injury (TBI) have been elusive. While laboratory studies provide a conceptual framework for the potential efficacy of corticosteroids in this context, clinical trials testing this hypothesis have yielded no convincing evidence of clinical benefit. Here, we review the five key randomized control trials (RCTs) that have examined this issue. Based on the proposed primary endpoints of these RCTs, the five RCTs consistently showed that corticosteroids do not confer significant benefit in the TBI population.

A Novel, Minimally-Invasive Approach to Repair Degenerative Disk Disease in an Ovine Model Using Injectable Polymethyl-Methacrylate and Bovine Collagen (PMMA/BC)

BACKGROUND

The natural, inflammatory repair processes of an injured intervertebral degenerative disc can propagate further injury and destruction. While there are many different treatment modalities of the pain related to degenerative disc disease, none are actually reparative in nature. Treatment strategies to repair a degenerative disc without inducing a destructive inflammatory milieu have been elusive. 

PURPOSE

The purpose of this experiment is to discover the feasibility of reconstructing an injured intervertebral disc using an injected, inert polymer as the foundation for endogenous collagen growth.

STUDY DESIGN

In this ovine model of six subjects in total, we introduce a modality where a large inert polymer, polymethyl methacrylate (PMMA), in conjunction bovine collagen (BC) is injected into the intervertebral disc. Following six months of observation, histologic specimens were evaluated macroscopically and microscopically for evidence of a benefit of the injectable PMMA/BC.

METHODS

We obtained six merino sheep for this study. Concentric injuries were made to four of their lumbar intervertebral discs. Two of those levels were treated with a percutaneous injection of 0.3 cc of PMMA/BC. The remaining lumbar levels were left untreated and were our controls. After six months, all subjects were sacrificed. Their four levels were extracted and were examined macroscopically and microscopically.

RESULTS

All subjects tolerated the lumbar injury and percutaneous injection of PMMA/BC well. After the six month interval, all subjects have demonstrated an intact architecture of their lumbar disc height at the macroscopic and microscopic level. Microscopically, there was no evidence of external migration of the PMMA/BC microspheres, nor was there any evidence of an inflammatory response by its presence. Notably, the PMMA/BC microspheres were well-incorporated into the concentric disc tears and had undergone endogenous collagen formation in its environment. Treatment levels were revealing for maintenance of disc height without evidence of an ongoing degeneration. The controlled levels were revealing for continued disc degeneration with loss of disc height and evolving injury at the level of the concentric tear.

CONCLUSIONS

This ovine model demonstrates a novel and promising technique for prevention and arrest of lumbar intervertebral disc degeneration.

Novel Transabdominal Motor Action Potential (TaMAP) Neuromonitoring System for Spinal Surgery

INTRODUCTION

Minimally invasive lateral lumbar interbody fusion (LLIF) approaches to the lumbar spine reduce patient morbidity compared to anterior or posterior alternatives. This approach, however, decreases direct anatomical visualization, creating the need for highly sensitive and specific neurophysiological monitoring. We seek to determine feasibility in 'transabdominal motor action potential (TaMAP)' monitoring as an assessment for the integrity of the neural elements during lateral-approach surgeries to the lumbar spine.

METHODS

Cathode and anode leads were placed on the posterior and anterior surfaces of two porcine subjects. Currents of varying degrees were transmitted across, from front to back. Motor responses were monitored and recorded by needle electrodes in specific distal muscle groups of the lower extremity. Lastly, the cathode and anode were placed anterior and posterior to the chest wall and stimulated to the maximum of 1500 mA to determine any effect on cardiac rhythm.

RESULTS

Responses were seen by measuring vertical height differences between peaks of corresponding evoked potentials. Recruitment began at 200 mA in the lower extremities. Stimulation at 450 mA recruited a reliable and distinguishable electrographic response from most muscle groups. Responses were recorded and reliably measured and increased in proportion to the graduation of transabdominal stimulation current; no responses were seen in the arms or face. 1500 mA across the chest wall failed to stimulate or induce cardiac arrhythmia on repeated stimulation, indicating safety of stimulation.

CONCLUSION

TaMAPs seen in the animal model provide a potential alternative to standard transcranial motor evoked potentials done in the lateral approach of LLIFs. TaMAP recordings in most muscle groups were recordable and reliable, though some muscle groups failed to stimulate. Safety of transabdominal motor evoked potentials was confirmed in this porcine study. Future studies should examine TaMAPs reliability in detecting compressive lesions of nerve roots and peripheral nerves.

Cadaveric Analysis of the Kambin's Triangle

Introduction

Kambin’s Triangle is a right triangle over the dorsolateral disc. The area of this right triangle currently serves as a strategic site of posterolateral, minimally invasive access to the nerve root for delivery of epidural steroid injections. This posterolateral approach has also been considered a safe area of access to the intervertebral disc space and, thus, an effective approach in reducing complications, such as violation of the thecal sac, the nerve root, or the bony elements of the spine during minimally invasive spinal surgery. No published studies have been performed to characterize the dimensions of the Kambin's Triangle. Our aim is to characterize its dimensions at the lumbar levels and determine its efficacy and safety as a site of access for minimally invasive spinal surgery.

Methods

Two randomly chosen adult male cadavers were used for this study. The measurements were made bilaterally at their lumbar levels (L1–L5), which equates to 16 total measurements (eight bilateral disc spaces on two cadavers). The disc space was first accessed using a Kirschner wire in a standard oblique approach. With the assistance of fluoroscopy, a Kirschner wire was passed into the disc through the Kambin’s Triangle. The procedure was performed on the cadavers bilaterally at four levels, followed by open dissection. The calculations of the area were made by measuring the exiting nerve root, the superior border of the caudal vertebra, and the superior articulating facet—the borders of the Kambin's Triangle.

Results

The Kambin’s Triangle height and width respectively averaged at 12 mm and 10 mm (L1–L2), 13 mm and 11 mm (L2–L3), 17 mm and 11 mm (L3–L4), and 18 mm and 12 mm (L4–L5). Thus, the area at each level was 60 mm² (L1–L2), 71.5 mm² (L2–L3), 93.5 mm² (L3–L4), and 108 mm² (L4–L5). All dissected levels demonstrated adequate anchoring of the Kirschner wire into the disc space with no evidence of nerve injury. Following this, a retractor was placed and complete discectomies were performed. All exiting nerves were protected in this safe zone and the thecal sac remained inviolate.

Conclusion

Understanding the Kambin’s Triangle will assist surgeons in the minimally invasive approach to spinal surgeries, with potentially safe placement of interbody cages through this strategic space.