Operative Corridor Research Articles

Single-Surgeon in Vivo Experience with the Zeiss QEVO Microinspection Tool: An Analysis of Its Use for Extending the Reach of Operative Visualization

The operating microscope is a foundational tool in modern neurosurgery. Operating microscopes serve increasingly as the lynchpin for highly sophisticated visualization platforms incorporating many complementary technologies. The Zeiss QEVO microinspection tool is a 45-degree viewing endoscopic instrument integrated into the Zeiss KINEVO 900 operating microscope (Carl Zeiss AG, Oberkochen, Germany). The QEVO tool enables surgeons to "look around the corners" of the surgical field to optimize visualization within tight operative corridors. In this article, we document our experience using the QEVO microinspection tool in a series of complex cranial neurosurgery procedures. This report focuses on the handling, visualization, and overall utility of the QEVO tool for achieving optimal visualization in deep cranial corridors.

A Review of Minimally Invasive Techniques in Thoracolumbar Trauma

AbstractThe development of endoscopy, microscopy, and image guidance system provided the impetus for the adoption of minimally invasive surgery (MIS) techniques in the management of spinal trauma patients. The underlying drive has been an attempt to achieve the functional and biomechanical goals inherent to trauma care but through MIS techniques. Broadly the MIS techniques for spinal trauma can be divided into two categories—fusion and nonfusion methods. Fusion methods include mini-open or keyhole approaches that allow for discectomy and/or corpectomy and cage reconstruction via an anterior/lateral/posterior operative corridor. The nonfusion methods primarily include percutaneous pedicle screw fixation, kyphoplasty, and vertebroplasty, all without placement of bone graft or other attempts at inducing arthrodesis. In this review article, we have stratified the MIS techniques based on the operative corridor used and briefly described the decision-making process, technical nuances, pros, and cons of each technique.

Intradural Clinoidectomy: A Tailored Osteotomy for Approaching the Paraclinoid Carotid Artery and Interpeduncular Cisterns

Anterior clinoidectomy is an important tool for neurovascular and skull base surgeons. This technique is cardinal for expanding access to the sella, proximal carotid artery, and central skull base. The goal of anterior clinoidectomy is to reveal the more proximal ophthalmic and clinoidal segments of the internal carotid artery while unroofing the optic canal and skeletonizing the proximal optic nerve. This maneuver expands the opticocarotid and carotid-oculomotor access windows and therefore the operative corridor to the interpeduncular cisterns.

Extradural Clinoidectomy: An Efficient Technique for Expanding the Operative Corridor Toward the Central Skull Base

Extradural anterior clinoidectomy is an important tool for neurovascular and skull base surgery. This technique is cardinal for expanding access to the proximal carotid artery, optic nerve, sella, and the central skull base. The goal of anterior clinoidectomy is to reveal the more proximal ophthalmic and clinoidal segments of the internal carotid artery (ICA) while skeletonizing the proximal optic nerve. This maneuver expands the opticocarotid and carotid-oculomotor windows and therefore the operative corridor to the interpeduncular cisterns; both the carotid artery and optic nerve are partially untethered or liberated and can be more safely mobilized.

RARE-12. VASCULOPATHY IN PEDIATRIC CRANIOPHARYNGIOMA PATIENTS TREATED WITH SURGERY AND RADIOTHERAPY

PURPOSEAs much as 40% of pediatric brain tumor patients will experience varied levels of Vasculopathy (VS), however few predictive factors have been described. Here we describe the type and timing of VS and explore the relationship between treatment modality and the timing, location, and distribution of VS.METHODS94 pediatric Craniopharyngioma patients underwent surgery and proton radiotherapy. Pre- and post-treatment imaging, cumulative physical and biological proton dose maps, clinical characteristics, and measures of dyslipidemia were evaluated. MR and MRAs were evaluated for pre- and post-radiotherapy VS (type, workup, location, and severity). VS events were segmented and described according to their normal brain region, and vascular territory.RESULTS47 patients were found to have 154 confirmed VS of varying severity with a median time to event of 3.41 years 95% CI 3.08–3.88. 22% (N=21) of patients had ≥1 pre-existing instances of VS and 26.6% (N=25) had a dyslipidemia at diagnosis. Forty-six (48.9%) patients had evidence of VS post-RT with 9.5% (N=9) being clinically significant. Aspirin was recommended in 10.6% (N=10) patients. Only 4 (4.2%) patients required revascularization. Clinical characteristics were not predictive of VS. An increased frequency of VS were observed along the operative corridor and high-dose radiotherapy field.CONCLUSIONSVS often precedes radiotherapy necessitating appropriate baseline imaging. Surgery type and extent are interrelated to the risk for radiotherapy-induced VS. While the spatial radiotherapy dose distribution approximated most vascular injury events, it was not all-inclusive. Spatial modeling of biological and physical dose may offer insights into therapy related vascular injury.

Primary Repair of Posteriorly Located Anterior Skull Base Dural Defects Using Nonpenetrating Titanium Clips in Cranial Trauma.

Objective Primary repair of posteriorly located anterior skull base (ASB) dural defects following cranial trauma is made difficult by narrow operative corridors and adherent dura mater. Inadequate closure may result in continued cerebrospinal fluid (CSF) leak and infectious sequelae. Here, we report surgical outcomes following the use of nonpenetrating titanium microclips as an adjunctive repair technique in traumatic anterior skull base dural defects extending from the olfactory groove to the tuberculum sellae. Methods All trauma patients who underwent a bifrontal craniotomy from January 2013 to October 2019 were retrospectively reviewed. Patients with ASB defects located at posterior to the olfactory groove were analyzed. Patients with isolated frontal sinus fractures were excluded. All patients presented with CSF leak or radiographic signs of dural compromise. Patients were divided according to posterior extent of injury. Patient characteristics, imaging, surgical technique, and outcomes are reported. Results A total of 19 patients who underwent a bifrontal craniotomy for repair of posteriorly located ASB dural defects using nonpenetrating titanium microclips were included. Defects were divided by location: olfactory groove (10/19), planum sphenoidale (6/19), and tuberculum sellae (3/19). No patients demonstrated a postoperative CSF leak. No complications related to the microclip technique was observed. Clip artifact did not compromise postoperative imaging interpretation. Conclusion Primary repair of posteriorly located ASB dural defects is challenging due to narrow working angles and thin dura mater. Use of nonpenetrating titanium microclips for primary repair of posteriorly located dural defects is a reasonable adjunctive repair technique and was associated with no postoperative CSF leaks in this cohort.

The Paramedian Supracerebellar Approach: A Less Disruptive and More Flexible Operative Corridor to the Pineal and Posterior Upper Brainstem Regions

The paramedian supracerebellar craniotomy is an underrecognized route to the midline and paramedian regions of the upper posterior brainstem. As compared with its midline supracerebellar counterpart, this less disruptive approach preserves the majority of the midline bridging veins, requires less cerebellar retraction, and is significantly more efficient. In this offering, I will emphasize the realities of this flexible route and its remarkable advantages in reaching deep-seated lesions.

Scrub Typhus in India: A Critical Commentary

Scrub typhus in India, although, dates back to World War II, was nearly forgotten barring occasional reporting of outbreaks from the Indian Armed Forces, which kept the interest alive in the disease. Scrub typhus at that time was considered a formidable foe. It was credited with inflicting heavy casualties amongst troops in the China-Burma-India operational corridor, which forced the commanders to withdraw troops from these areas. This tended to alter the course of the war itself. An old foe indeed; scrub typhus continues to take a heavy toll on the vulnerable Armed Forces personnel who are posted in areas that enhance their vulnerability to the disease and has predictably also impacted the unsuspecting civil population too who are residing in such areas. Scrub typhus has undoubtedly emerged as a major public health challenge in India. Slow, yet steady, appreciation of the impact of scrub typhus though is being felt, however, professional efforts are still dismal and have failed to bring the disease to limelight and contain its insistent march. Scrub typhus, although an old foe, has reemerged albeit with new challenges.

Surgical Challenges Associated With Anterior Choroidal Artery Aneurysm Clipping: 2-Dimensional Operative Video.

Surgical treatment of anterior choroidal artery (AChA) aneurysms is challenging because of the constrained operative corridor and limitations imparted by the surrounding rigid structures during the exposure. The AChA most commonly arises as a single branch from the communicating (C7) segment of the internal carotid artery but has 2 to 4 branches in approximately one-third of cases, and aneurysms generally arise from the parent vessel interface with these branches. This patient experienced a sentinel headache 4 d before presenting with subarachnoid hemorrhage. The patient had a large right AChA aneurysm with a unique configuration in which the parent vessel was located anterior to the aneurysm. Endovascular therapy was aborted because there was an AChA branch at the base of the aneurysm. An orbitozygomatic craniotomy was performed that provided transsylvian access to the region of interest. Clip application was challenging because of the close proximity of the branch vessels. Intraoperative indocyanine green evaluation and postoperative angiogram showed patency of the AChA and posterior communicating artery. This video demonstrates the surgical challenge associated with AChA aneurysms because of the proximity of adjacent structures and highlights the importance of meticulous technique during clip application. The patient gave informed consent for surgery and video recording. Institutional review board approval was deemed unnecessary. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Minimally Invasive Navigated Foraminal Discectomy via Contralateral Approach Using a 3-Dimensional 4K High-Definition Exoscope: 2-Dimensional Operative Video.

This surgical video is the first to demonstrate a novel minimally invasive technique of utilization of surgically navigated foraminal discectomy using a 3-dimensional 4k high-definition exoscope (Sony Olympus). Typical approaches for foraminal disc herniations may involve violation of the facet resulting in subsequent destabilization requiring fusion.1 Although minimally invasive facet-sparing contralateral techniques have previously been described,2 there is continued limitations stemming from rudimentary localization with standard fluoroscopy and impaired visualization with the bulky traditional operative microscope.3 We demonstrate that high-quality real-time navigation is possible using standard Iso-C intraoperative fluoroscopy for 3-dimensional reconstructions, allowing for intraoperative routing. Navigation is particularly advantageous for adjustments in the trajectory of the tubular retractor and for confirmation of complete foraminal decompression. Visualization from the 4k high-definition exoscope also allows for an unparalleled view of the narrow operative corridor and allows for participation from the operative team. Informed consent was obtained from the patient for the surgery in its entirety.

Changes in the Operative Corridor in Oblique Lumbar Interbody Fusion Between Preoperative Magnetic Resonance Imaging and Intraoperative Cone-Beam Computed Tomography Using Morphometric Analysis.

BackgroundThe oblique lumbar interbody fusion or anterior-to-psoas (OLIF/ATP) technique relies on a corridor anterior to the psoas and posterior to the vasculature for lumbar interbody fusion. This is evaluated preoperatively with CT and/or MRI. To date, there have been no studies examining how intraoperative, lateral decubitus positioning may change the dimensions of this corridor when compared to preoperative imaging.ObjectiveOur objective was to evaluate changes in the intraoperative corridor in the supine and lateral positions utilizing preoperative and intraoperative imaging.MethodsWe performed a retrospective analysis among patients who have undergone an OLIF/ATP approach at two tertiary care centers from 2016 to 2018 by measuring the distance between the left lateral border of the aorta or iliac vessels and anteromedial border of the psoas muscle from L1-L2 through L4-5 disc spaces. We compared this corridor between supine, preoperative MRI axial and intraoperative CT acquired in the right lateral decubitus position.ResultsThirty-three patients, 15 of whom were female, were included in our study. The average age of the patients was 65.4 years and the average BMI was 31 kg/m2. The results revealed a statistically significant increase (p<.05) in the intraoperative corridor from supine to lateral decubitus positioning at all levels. However, age, BMI, and gender had no statistically significant impact on the preoperative versus intraoperative corridor.ConclusionThis is the first study to provide objective evidence that lateral decubitus positioning increases the intraoperative corridor for OLIF/ATP. Our study demonstrates that lateral decubitus positioning provides a more favorable corridor for the OLIF/ATP technique from L1-L5 disc levels.

Minimally invasive resection of intracranial lesions using tubular retractors: a large, multi-surgeon, multi-institutional series.

Lesions located in subcortical areas are difficult to safely access. Tubular retractors have been increasingly used successfully with low complication profile to access lesions by minimizing brain retraction trauma and distributing pressure radially. Both binocular operative microscope and monocular exoscope are utilized for lesion visualization through tubular retractors. We present the largest multi-surgeon, multi-institutional series to determine the efficacy and safety profile of a transcortical-transtubular approach for intracranial lesion resections with both microscopic and exoscopic visualization. We reviewed a multi-surgeon, multi-institutional case series including transcortical-transtubular resection of intracranial lesions using either BrainPath (NICO, Indianapolis, Indiana) or ViewSite Brain Access System (VBAS, Vycor Medical, Boca Raton, Florida) tubular retractors (n=113). One hundred thirteen transtubular resections for intracranial lesions were performed. Patients presented with a diverse number of pathologies including 25 cavernous hemangiomas (21.2%), 15 colloid cysts (13.3%), 26 GBM (23.0%), two meningiomas (1.8%), 27 metastases (23.9%), 9 gliomas (7.9%) and 9 other lesions (7.9%). Mean lesion depth below the cortical surface was 4.4cm, and mean lesion size was 2.7cm. A gross total resection was achieved in 81 (71.7%) cases. Permanent complication rate was 4.4%. One patient (0.8%) experienced one early postoperative seizure (<1week postop). No patients experienced late seizures (>1week follow-up). Mean post-operative hospitalization length was 4.1days. Tubular retractors provide a minimally invasive operative corridor for resection of intracranial lesions. They provide an effective tool in the neurosurgical armamentarium to resect subcortical lesions with a low complication profile.

Use of Tubular Retractors for Minimally Invasive Resection of Deep-Seated Cavernomas.

Cavernomas located in subcortical or eloquent locations are difficult lesions to access safely. Tubular retractors, which distribute retraction pressure radially, have been increasingly employed successfully. These retractors may be beneficial in subcortical cavernoma resection. To review a single institution's case series to determine the safety profile and efficacy of transcortical-transtubular cavernoma resections and to describe our transtubular operative technique. We reviewed a single institution's transcortical-transtubular cavernoma resections using either BrainPath (NICO, Indianapolis, Indiana) or ViewSite Brain Access System (Vycor Medical, Boca Raton, Florida) tubular retractors performed from 2013 to 2018 (n=20). Gross total resection was achieved in all patients. When a developmental venous anomaly (DVA) was present, avoidance of DVA resection was achieved in all cases (n=4). All patients had a supratentorial cavernoma with mean depth below cortical surface of 44.1 mm. Average postoperative clinical follow-up was 20.4 wk. Early neurologic deficit rate was 10% (n=2); permanent neurologic deficit rate was 0%. One patient (5%) experienced early postoperative seizures (<1 wk postop). No patients experienced late seizures (>1 wk follow-up). Engel class 1 seizure control at final clinical follow-up was achieved in 87.5% of patients presenting with preoperative epilepsy. Tubular retractors provide a low-profile, minimally invasive operative corridor for resection of subcortical cavernomas. There were no permanent neurologic complications in our series of 20 cases, and long-term seizure control was achieved in all patients. Thus, tubular retractors appear to be a safe and efficacious tool for resection of subcortical cavernomas.

The Orbitozygomatic Craniotomy and Its Judicious Use.

The concept of maximizing bone removal along the skull base has been advocated to expand the operative space for large, firm, and encasing ventral and ventrolateral skull base tumors. However, indications for the use of such osteotomies have not been well defined. The improved maneuverability and enhanced extent of expansion of the operative corridor via the skull base approaches compared to those of standard craniotomies have been based on cadaveric studies that might not simulate the operative environment realistically. Bony removal alone is not adequate to protect neurovascular structures, and strategic use of dynamic retraction and innovative operative routes are some of the other factors that contribute to successful microsurgery. In this analysis, the more discriminate indications and modified techniques for orbitozygomatic osteotomy are discussed.

An Eyebrow, Supracarotid Triangle Approach for Lesions at the Ventral Thalamopeduncular Junction: A Technical Report

Lesions arising at the ventral thalamopeduncular junction are difficult to resect. In addition to being relatively inaccessible, these lesions are located in one of the most sensitive areas of the brain. A critical question is whether new approaches could be developed to allow surgeons to adequately resect these lesions with reasonable outcomes. In the present report, we describe our approach to resect lesions in this region of the brain using an eyebrow craniotomy approach with a trajectory through the supracarotid triangle. Through retrospective data collection, we present a small series of patients who had undergone an eyebrow, supracarotid triangle approach to resect lesions located at the thalamopeduncular junction. We describe our surgical technique and report patient outcomes using this approach. Three patients had undergone an eyebrow, supracarotid approach for resection of a lesion arising at the ventral thalamopeduncular junction. Two patients had presented with a cavernoma and one with a pilocytic astrocytoma. Complete resection of all 3 lesions was achieved during surgery without any intraoperative complications. No patient developed permanent contralateral weakness despite entering the peduncle during surgery. One patient developed permanent paresthesia in his left hand. Lesions arising at the ventral thalamopeduncular junction can be adequately resected with reasonable outcomes using an eyebrow, supracarotid triangle approach. This operative technique establishes another potential operative corridor by which neurosurgeons can resect lesions arising within this relatively inaccessible part of the brain.

The Extended Pterional Craniotomy: A Contemporary and Balanced Approach.

Pterional craniotomy is the workhorse approach among cranial operative corridors. It is a highly flexible skull base approach that affords excellent exposure of the anterior cranial fossa, the circle of Willis, and the interpeduncular region. Its strategic use via dynamic retraction can obviate the need to use a more extensive skull base route, such as orbitozygomatic osteotomy, in select cases. The focus of the surgeon should be reaching the surgical target effectively while minimizing disruption of normal anatomy. In other words, the focus should be less on "how to get there" and more on "what to do when you are there." This multimedia presentation summarizes an efficient execution of this route and its expansion and demonstrates the surgical corridor via 3-dimensional virtual reality models.

Contralateral Ventriculostomy for Intraoperative Brain Relaxation in Supratentorial Brain Tumors.

CSF drainage from the ventricular system is a popular and effective technique for intraoperative brain relaxation as it reduces ICP, enlarges extra-axial operative corridors, and slackens the brain increasing its tolerance for surgical manipulation. However, sometimes when the ventricular chambers distant from the site of pathology are tapped, there is a risk of neurological worsening due to paradoxical herniation of the brain, exemplified by the phenomenon of upward transtentorial herniation observed in posterior fossa tumors, consequent to a supratentorial ventriculostomy. Expectation of an analogous phenomenon precludes contralateral ventricular drainage in supratentorial brain tumors producing midline shift, subfalcine herniation, and resultant distension of the opposite lateral ventricles. Demonstrating the safety and efficacy of intraoperative contralateral ventricular drainage in the presence of sub-falcine herniation. Clinical and imaging information were retrospectively collected for four cases in which this technique was adopted. The first case was a large clinoidal meningioma with a midline shift and contralateral ventriculomegaly. EVD from the dilated ventricle provided optimum brain conditions for safe resection of the tumor through an orbitopterional approach. The second case required a contralateral EVD to reduce ICP intraoperatively, for a recurrent anaplastic ependymoma with severe mass effect. It reduced the venous hypertension related to raised ICP minimizing the blood loss. Contralateral EVD was utilized to enlarge the working corridor for interhemispheric approach in two cases. Contralateral ventricular drainage is a safe, effective, and convenient operative step for reducing brain turgor in the presence of sub-falcine herniation produced by large supratentorial tumors.

Expanding the horizons of minimally invasive spine surgery

The trend of using smaller operative corridors is observed in various surgical specialties. The development of smart technologies with the overall aim of reducing surgical trauma has resulted in the concept of minimally invasive surgical techniques. Enhancements in microsurgery, tubes, endoscopy, and various percutaneous techniques, as well as improvement of implant materials, have proven to be milestones. The ease of performing surgery through tubes has recently evolved into percutaneous placement of spinal instrumentation, including intervertebral spacers, rods, and pedicle screws. The advancement of training of spine surgeons and the integration of image guidance with precise intraoperative imaging, computer-, and navigation-assisted treatment modalities constitute the era of reducing treatment morbidity in spinal surgery. This progress has led to the present era of preserving spinal function. In this report, we present a chronological perspective of the use of tubular retractors, the learning curve of tubular retractor in dealing complex cases and its wide applications, and expanding the horizon using tubular retractors.

Intraoperative Management of an Enlarged Suprameatal Tubercle During Microvascular Decompression of the Trigeminal Nerve, Surgical and Anatomical Description: 2-Dimensional Operative Video.

The suprameatal tubercle is a variable prominence of the posterior aspect of the petrous part of the temporal bone located above the internal acoustic meatus. An enlarged suprameatal tubercle (EST) may present an obstacle during posterior fossa operations, including microvascular decompression (MVD). In this video we present the case of a 55-yr-old woman with 2 yr of medically refractory left V2-3 typical trigeminal neuralgia. Magnetic resonance imaging (MRI) was suspicious for a compressive superior cerebellar artery (SCA) loop, and negative for any other pathological findings. A left retrosigmoid craniotomy was performed, and upon initial exploration, only the most proximal, superior aspect of the trigeminal nerve was unobscured by an EST. The EST was subsequently removed using the ultrasonic aspirator with bone cutting attachment, allowing full visualization of the nerve from root entry zone (REZ) to Meckel's cave. Inferiorly, a small EST remnant was left to protect the VII-VIII complex. An MVD was performed using Teflon felt to elevate the SCA loop off the REZ and nerve, which was then fully explored, to ensure complete decompression. The patient recovered well with resolved trigeminal neuralgia and no new deficit. EST is a rare anatomic variant, with potentially significant implications for visualization of structures superior and deep to the internal acoustic canal, including the trigeminal REZ and nerve. Resection of the tubercle is safe, and recommended where it markedly obstructs the operative corridor. Care should be taken to wax the drilled surface of the petrous temporal bone and minimize incumbent risk of cerebrospinal fluid leak. Informed consent was appropriately documented and verified as outlined by our institutional guidelines.

Anatomical Predictors of Transcranial Surgical Access to the Suprasellar Space

Objective The suprasellar space is a common location for intracranial lesions. The position of the optic chiasm (prefixed vs. postfixed) results in variable sizes of operative corridors and is thus important to identify when choosing a surgical approach to this region. In this study, we aim to identify relationships between suprasellar anatomy and external cranial metrics to guide in preoperative planning. Methods T2-weighted magnetic resonance images (MRIs) from 50 patients (25 males and 25 females) were analyzed. Various intracranial and extracranial metrics were measured. Statistical analysis was performed to determine any associations between metrics. Results Interoptic space (IOS) size correlated with interpupillary distance (IPD; a = 7.3, 95% confidence interval [CI] = 4.5-10.0, R 2 = 0.3708, p = 0.0009). IOS size also correlated with fixation of the optic chiasm, for prefixed chiasms ( n = 7), the mean IOS is 205.14 mm 2 , for normal chiasm position ( n = 33) the mean IOS is 216.94 mm 2 and for postfixed chiasms ( n = 10) the mean IOS is 236.20 mm 2 ( p = 0.002). IPD correlates with optic nerve distance (OND; p = 0.1534). Cranial index does not predict OND, IPD, or IOS. Conclusion This study provides insight into relationships between intracranial structures and extracranial metrics. This is the first study to describe a statistically significant correlation between IPD and IOS. Surgical approach can be guided in part by the size of the IOS and its correlates. Particularly small intraoptic space may guide the surgeon away from a subfrontal approach.