Comparison of endoscope- versus microscope-assisted resection of deep-seated intracranial lesions using a minimally invasive port retractor system

Full access

OBJECT

Tubular brain retractors may improve access to deep-seated brain lesions while potentially reducing the risks of collateral neurological injury associated with standard microsurgical approaches. Here, microscope-assisted resection of lesions using tubular retractors is assessed to determine if it is superior to endoscope-assisted surgery due to the technological advancements associated with modern tubular ports and surgical microscopes.

METHODS

Following institutional approval of the tubular port, data obtained from the initial 20 patients to undergo transportal resection of deep-seated brain lesions were analyzed in this study. The pathological entities of the resected tissues included metastatic tumors (8 patients), glioma (7), meningioma (1), neurocytoma (1), radiation necrosis (1), primitive neuroectodermal tumor (1), and hemangioblastoma (1). Surgery incorporated endoscopic (5 patients) or microscopic (15) assistance. The locations included the basal ganglia (11 patients), cerebellum (4), frontal lobe (2), temporal lobe (2), and parietal lobe (1). Cases were reviewed for neurological outcomes, extent of resection (EOR), and complications. Technical data for the port, surgical microscope, and endoscope were analyzed.

RESULTS

EOR was considered total in 14 (70%), near total (> 95%) in 4 (20%), and subtotal (< 90%) in 2 (10%) of 20 patients. Incomplete resection was associated with the basal ganglia location (p < 0.05) and use of the endoscope (p < 0.002). Four of 5 (80%) endoscope-assisted cases were near-total (2) or subtotal (2) resection. Histopathological diagnosis, presenting neurological symptoms, and demographics were not associated with EOR. Complication rates were low and similar between groups.

CONCLUSIONS

Initial experience with tubular retractors favors use of the microscope rather than the endoscope due to a wider and 3D field of view. Improved microscope optics and tubular retractor design allows for binocular vision with improved lighting for the resection of deep-seated brain lesions.

ABBREVIATIONSEOR = extent of resection; GTR = gross-total resection; NTR = near-total resection; STR = subtotal resection.

Abstract

OBJECT

Tubular brain retractors may improve access to deep-seated brain lesions while potentially reducing the risks of collateral neurological injury associated with standard microsurgical approaches. Here, microscope-assisted resection of lesions using tubular retractors is assessed to determine if it is superior to endoscope-assisted surgery due to the technological advancements associated with modern tubular ports and surgical microscopes.

METHODS

Following institutional approval of the tubular port, data obtained from the initial 20 patients to undergo transportal resection of deep-seated brain lesions were analyzed in this study. The pathological entities of the resected tissues included metastatic tumors (8 patients), glioma (7), meningioma (1), neurocytoma (1), radiation necrosis (1), primitive neuroectodermal tumor (1), and hemangioblastoma (1). Surgery incorporated endoscopic (5 patients) or microscopic (15) assistance. The locations included the basal ganglia (11 patients), cerebellum (4), frontal lobe (2), temporal lobe (2), and parietal lobe (1). Cases were reviewed for neurological outcomes, extent of resection (EOR), and complications. Technical data for the port, surgical microscope, and endoscope were analyzed.

RESULTS

EOR was considered total in 14 (70%), near total (> 95%) in 4 (20%), and subtotal (< 90%) in 2 (10%) of 20 patients. Incomplete resection was associated with the basal ganglia location (p < 0.05) and use of the endoscope (p < 0.002). Four of 5 (80%) endoscope-assisted cases were near-total (2) or subtotal (2) resection. Histopathological diagnosis, presenting neurological symptoms, and demographics were not associated with EOR. Complication rates were low and similar between groups.

CONCLUSIONS

Initial experience with tubular retractors favors use of the microscope rather than the endoscope due to a wider and 3D field of view. Improved microscope optics and tubular retractor design allows for binocular vision with improved lighting for the resection of deep-seated brain lesions.

Since the first use of the operative microscope over 50 years ago, microsurgery has evolved into an indispensable technique in neurosurgery. In any surgical procedure, adequate visualization of the operative field is paramount for the surgeon. Traditionally, surgeons have employed “retractor” devices to create and maintain a visual corridor in order to access deep-seated lesions. Within neurosurgery, those designed for intracranial use include the well-known Greenberg, Leyla, and Budde Halo retractor systems. Like other highly sensitive tissues, the brain is prone to injury from the prolonged and excessive pressures that are potentially imposed by the retractor devices. Particularly, during approaches to deep-seated intracranial lesions, the surrounding white matter that comprises the surgical corridor is vulnerable to retractor-induced insult. The mechanism of injury is thought to be excessively prolonged compression of the cerebral vasculature, thereby inducing ischemia in the normally perfused brain tissue.1,4 To avoid this, pharmaceutical agents like mannitol, nimodipine, and corticosteroids are widely used to protect against ischemic injury, both from retraction and other etiologies like cerebral edema and hemorrhage.2,9,13,21,24 The technical aspects of the retractor systems—such as stereotactic frame systems, the Leyla flexible retractor arm, and cylindrical-shaped retractors, the latter of which is the basis of this study—have also advanced considerably and thereby reduced retractor-induced injury.12,20,36

One of the first cylindrical-shaped brain retractor devices was modeled after the curves of the gynecological speculum.17 These first tubular retractors introduced the concept of safely dilating the brain with progressively larger cylinders, creating a surgical corridor to access deep lesions. This design has since been commonly referred to as a tubular retractor. A novel feature of this original retractor design is its compatibility with stereotactic frame systems as both a fixed stereotactic reference point and as a retractor.16,17 Modified versions of this original design have gained wide use in spinal surgeries performed using a minimally invasive approach to repair herniated discs, vertebral interbody fusions, and decompression of spinal stenosis, among other conditions.7,10,19,29 Although the tubular brain retractor was introduced more than 3 decades ago, these devices have only recently gained ground as a tool to access deep-seated brain lesions. To date, most of the literature regarding the tubular retractors used in brain surgery is comprised of individual case reports that describe the successful resection of deep-seated lesions such as thalamic pilocytic astrocytomas, colloid cysts in the third ventricle, hematomas, and cavernous angiomas.5,18,25,27,28,35 Recently, Vycor Medical Inc. developed a new tubular retractor designed specifically for intracranial use, which is called the Viewsite Brain Access System and referred to in this study as the port. Unlike the original tubular retractor, the port is fully transparent, allows visualization of the entire surgical corridor, and is compatible with the majority of current frameless neuronavigation systems.

While a few recent case series have documented surgical experiences with the port, there have been no reports thus far comparing endoscope-assisted to microscope-assisted port procedures in regards to operative outcomes. Comparisons between the 2 modalities have been a topic of debate in other areas of interest, including approaches to the sella turcica, cerebellopontine angle, and posterior fossa.14,22,33,34 Previous reports on the port technique have documented visualization with multiple modalities, suggesting that intraoperative visualization is largely dependent on surgeon preference. The initial use of the port at our institution was evenly split between microscope-assisted surgery and endoscope-assisted surgery. However, we now exclusively use the microscope during surgery with the port because our initial experience led us to the belief that microscope-assisted surgery held definitive advantages over the endoscope when utilizing the port as the surgical corridor. With this study, we aimed to validate our impressions by retrospectively comparing surgical outcomes after port surgery using the endoscope or microscope. We also evaluated the literature and present our findings with the intent to optimize successful application of the port.

Methods

Twenty consecutive patients were identified who underwent the resection of a deep-seated brain lesion located within the basal ganglia, thalamus, cerebellum, or deep cortical lobes using the port between September 2010 and April 2011 at The Ohio State University Wexner Medical Center. The collected data included patient demographics, anatomic location of the lesion, and postoperative neurological outcomes. Extent of resection (EOR) was determined based on routine postoperative MRI performed within 24 hours after surgery. Postoperative T1-weighted images with diffusion restriction and T2-weighted FLAIR images were used to evaluate ischemic injury in the normal brain and the regression of surgical edema at 2 or more months after surgery. Gross-total resection (GTR) was defined as the resection of 100% of the target lesion, near-total resection (NTR) as greater than 95% but not 100% volumetric reduction of the lesion, and subtotal resection (STR) as less than 95% resection on postoperative MRI.

Statistics were calculated using GraphPad Prism 6 (GraphPad Software, Inc.). The p values were calculated using the Fisher exact test for retrospective data analyses.

Technical Data

The Viewsite Brain Access System (Vycor Medical Inc.) was used for surgical access in all patients. The retractor is available in 4 widths at the distal opening (12 mm, 17 mm, 21 mm, and 28 mm) and 3 lengths (3 cm, 5 cm, and 7 cm). Construction with transparent plastic allows for intraoperative visualization of the surrounding brain traversing the entire depth of the port. The system consists of an introducer and working channel port that can be inserted while distributing the brain tissue evenly in a 360° dispersion pattern. The attachment flange is compatible with most surgical arms in order to facilitate secure fixation of the port during surgery. All cases presented in this manuscript were operated on using the 12-mm retractor. In some cases, the 17-mm retractor was substituted later in the surgery to increase visualization. The retractors with 21-mm or 28-mm widths were never used in this series.

The OPMI Pentero 900 (Carl Zeiss Meditec AG) microscope was used for microscopic visualization of the surgical bed during port surgery, and the technical specifications of the microscope were evaluated for their potential impact on intraoperative visualization. For example, an integrated, electronically controlled, double-iris diaphragm offered a choice between maximum light and resolution or depth of field, which could be tailored to the specific size of the port being used. A 2-channel illumination design reduced shadowing in the deep cavities, primarily provided illumination of the field of interest, and automatically limited brightness to prevent inadvertent light exposure.

Endoscopic dissections were performed using 0°, 30°, and 45° Hopkins II rod-lens endoscopes (Karl Storz Endoscopy) measuring 4 mm × 18 cm. The endoscope was connected to a light source through a fiber optic cable and a camera fitted with 3 charge-couple device sensors. The endoscope system consisted of an endoscope, a working sheath, and an obturator, all of which were easily accommodated by the port and still permitted the bimanual technique. There was excellent illumination of the surgical field by virtue of the endoscope’s proximity to the anatomical structures. Wide-angle optics from the Hopkins II rod-lens provided high-resolution images. The availability of multiple-angle endoscopes facilitated the examination of areas that would be otherwise obscured from the operative microscope or the naked eye.

Port Technique

There are a number of ways a tubular retractor can be used, and surgeons familiar with the port likely have unique nuances to their surgical techniques. For deep-seated intraaxial brain tumors, we employ the following general techniques at our institution. Preoperative imaging is used to select the optimal trajectory toward the tumor that minimizes transgression of the eloquent areas of the brain, avoids ventricles, and optimizes visualization of the tumor. A curvilinear incision that provides sufficient access for a 3 × 3-cm craniotomy is performed. After bone flap removal and dural opening, the best entry point is determined either on a gyrus or through a sulcus. For the sulcal approach, the initial superficial portion of the pathway is dissected under the microscope to approximately 1.5 cm wide and all the way down to its fundus, where a linear opening is performed and any vessel that could be present is avoided. For approach through a gyrus, a 1.5-cm linear pial incision is performed and then dissected bluntly for up to 2 cm in depth to provide an initial dissection for the port. The navigation wand is secured within the port using bone wax with the tip of the wand at the end of the port. The port is then inserted via the cortical opening to the tumor using navigation guidance. The navigation wand and cannula of the port are removed, and the port is secured to a snake retractor arm which is locked to a Mayfield head clamp. At this point, either the microscope or endoscope is used to visualize and remove the tumor through the port. The length of the port is selected by measuring the distance from the surface of the brain to the far edge of the tumor. The smallest diameter port (12 mm) is always used initially. After debulking the tumor, if a larger diameter port is felt to be useful then the small-diameter port is exchanged for a port that is 1 size larger (17 mm). Further increases in port size during surgery have not been necessary. The angulation of the port can be altered as often as necessary during the procedure. Typically, small changes are made in angulation with the surface of the brain serving as the “fulcrum” for these changes. After removing the tumor, hemostasis within the resection cavity is achieved using standard techniques. The port is removed, and hemostasis along the wall of the trajectory is confirmed. Closure then proceeds per standard techniques.

Technique

Case Illustration 1

A 61-year-old male patient presented at our institution due to new-onset seizures. He was found to have moderate expressive aphasia and right-sided hemiparesis (Table 1; Case 14). Preoperative MRI demonstrated multiple small lesions and 1 dominant, symptomatic, heterogeneously enhancing lesion measuring 2.8 × 2.4 cm with significant vasogenic edema involving the left parietooccipital region (Fig. 1A). The patient had been recently diagnosed with cutaneous melanoma, and, therefore, these brain lesions were highly suspicious of melanoma metastases. Given the size of the dominant lesion and the patient’s clinical symptoms, resection was recommended as the initial management, to be followed by adjuvant radiation. The patient underwent left parietal craniotomy and minimally invasive microscope-assisted transportal surgery for GTR of the dominant lesion. A 3 × 3-cm craniotomy was performed and a 1-cm linear opening was made in the pia of 1 gyrus. The port was inserted via this pial opening to the surface of the tumor using navigation guidance (Fig. 2) and attached to a retractor arm to maintain positioning. The microscope was then used to visualize and remove the tumor at the depth of the port. Immediate postoperative imaging demonstrated GTR with minimal evidence of the surgical corridor (Fig. 1B and C). There were no complications associated with the surgery, and the patient subsequently received adjuvant radiation and chemotherapy. The final pathology was metastatic melanoma. At the 3-month follow-up visit, the patient’s presenting neurological symptoms had resolved. Diffusion-weighted MRI at that time demonstrated no evidence of recurrent tumor or postsurgical ischemic injury and only minimal residual edema (Fig. 1D and E).

FIG. 1.
FIG. 1.

Case 14. Microscopic transportal GTR of melanoma metastasis. Preoperative axial T1-weighted MR image (A) after Gd contrast administration demonstrates a left parietal metastasis from melanoma with significant vasogenic edema. Axial T1- (B) and T2-weighted (C) images after Gd contrast administration obtained 1 day after surgery demonstrate complete resection with a minimal surgical corridor and expected postoperative FLAIR changes. Axial T2- (D) and diffusion-weighted (E) images demonstrate the significant reduction of surgical edema and no evidence of ischemia along the surgical corridor 2 months after surgery.

FIG. 2.
FIG. 2.

Vycor port with Stryker navigation wand embedded in bone wax (inset, top left), which allows for navigation guidance of the port into the tumor, as depicted on the navigation screen to the right of the surgeon. Once the port has achieved the desired position, either the endoscope or microscope can be used for tumor resection via the port. Figure is available in color online only.

TABLE 1.

Patient characteristics and outcomes

Case No.Age (yrs), SexPathologyLocationPresenting SymptomsEORMicroscope or EndoscopeSize of Ports Used
175, MMetastasis (lung)Rt cerebellumAtaxiaGTREndoscope12 mm × 7 cm
237, FMetastasis (breast)Rt cerebellumAtaxiaNTREndoscope12 mm × 7 cm
324, MNeurocytomaRt basal gangliaAltered mental statusSTREndoscope12 mm × 7 cm
450, MPNETLt frontalHeadaches, nausea, vomitingSTREndoscope12 mm × 7 cm
559, FGBMRt basal gangliaAsymptomaticNTREndoscope12 mm × 7 cm; 17 mm × 7 cm
657, MGBMLt basal gangliaSeizuresNTRMicroscope12 mm × 7 cm
764, FHemangioblastomaLt cerebellumHeadaches, nausea, vomitingGTRMicroscope12 mm × 5 cm; 12 mm × 7 cm
863, MMetastasis (lung)Lt basal gangliaAltered mental status, visual changesGTRMicroscope12 mm × 7 cm
941, MAstrocytoma (fibrillary)Rt temporalSeizuresGTRMicroscope12 mm × 7 cm
1062, MMetastasis (lung)Lt frontalRt arm weaknessGTRMicroscope12 mm × 5 cm
1186, FMetastasis (lung)Lt cerebellumAtaxiaGTRMicroscope12 mm × 7 cm
1262, MGBMRt temporo-occipitalHeadache, nausea, vomitingGTRMicroscope12 mm × 7 cm
1374, FMetastasis (ovarian)Rt basal gangliaLt side weakness, dysarthriaGTRMicroscope12 mm × 7 cm
1461, MMetastasis (melanoma)Lt parietalSeizures, aphasiaGTRMicroscope12 mm × 7 cm
1553, FMeningiomaLt basal gangliaHeadache, nausea, vomitingGTRMicroscope12 mm × 7 cm; 17 mm × 7 cm
1624, MGBMRt basal ganglia, thalamusAltered mental statusNTRMicroscope12 mm × 7 cm
1731, MMetastasis (melanoma)Lt basal gangliaHeadache, nausea, vomitingGTRMicroscope12 mm × 7 cm; 17 mm × 7 cm
1865, MGBMLt basal gangliaRt side weaknessGTRMicroscope12 mm × 5 cm; 12 mm × 7 cm; 17 mm × 7 cm
1973, FGBMRt basal gangliaSeizureGTRMicroscope12 mm × 7 cm
2024, MRadiation necrosisRt basal gangliaAltered mental statusGTRMicroscope12 mm × 7 cm

GBM = glioblastoma multiforme; PNET = primitive neuroectodermal tumor.

Case Illustration 2

A 74-year-old female patient with a known history of Stage III ovarian cancer developed new-onset slurred speech (Case 13). Subsequently, brain MRI was performed, which demonstrated a heterogeneously enhancing mass centered in the right basal ganglia, measuring 2.7 cm × 2.5 cm, and extending into the lateral portion of the right thalamus (Fig. 3A). After discussion with the patient and neuro-oncology tumor board, the patient was taken to the operating room for GTR of her single lesion via microscope-assisted port surgery. Navigation to the tumor bed and placement of the port were performed similarly to that described for Case Illustration 1, with the exception that intraoperative brain mapping was performed to identify the central sulcus and avoid injury to the surrounding eloquent structures. After proper positioning, the port was locked into place using the Greenberg retractor system. Under microscopic visualization, central debulking of the tumor proceeded with tumor forceps in a piecemeal fashion. Given the spongy nature of the tumor, minute retractions of the port encouraged the tumor tissue to come into view within the port lumen. This technique yielded efficient resection of the tumor without compromising the normal brain tissue and is depicted in detail in Fig. 4, as well as Video 1.

VIDEO 1. We demonstrate a minimally invasive neurosurgical approach utilizing a transparent, tubular, port retractor (Vycor Medical Inc.) with microscopic visualization. The index patient is a 74-year-old female with suspected brain metastasis to the right basal ganglia from Stage III ovarian cancer. Accurate guidance of the port to the target of interest is shown utilizing a neuronavigation probe placed within the confines of the 12-mm × 7-cm port. There is adequate room within the port for manipulation of at least 2 instruments, such as the illustrated suction tip and tumor forceps. The ease of repositioning the port is also demonstrated, which encourages additional tumor tissue to appear within the operative field. Postoperative MRI showed GTR with evidence of a minimal surgical corridor on T2-weighted MRI and no diffusion restriction, indicative of ischemic injury. Copyright J. Bradley Elder. Published with permission. Click here to view with Media Player. Click here to view with Quicktime.

FIG. 3.
FIG. 3.

Case 13. Microscopic transportal GTR of ovarian cancer metastasis. Preoperative axial T1-weighted image (A) after Gd contrast administration demonstrates a heterogeneously enhancing metastatic lesion deep within the right basal ganglia. Axial T1-weighted image after Gd contrast administration (B) and axial T2-weighted FLAIR image (C) obtained 1 day after surgery showing total resection of the lesion and decompression of the ventricles. Postoperative coronal T1-weighted image (D) after Gd contrast administration demonstrates a minimal surgical corridor (white arrow).

FIG. 4.
FIG. 4.

An intraoperative photograph of a 12-mm (width) × 7-cm (length) Vycor port maintaining the surgical corridor. Cotton is seen within the port. The port is attached to a flexible snake-arm retractor allowing for self-retaining but easily adjustable retraction during surgery. The normal brain is readily seen through the transparent walls of the port (arrowhead) and is evenly distributed along the rounded edges of the port (left-pointing arrow). Minute retractions of the port encourage spongy tumor tissue to emerge into view (right-pointing arrow). Figure is available in color online only.

Final pathology confirmed metastatic ovarian cancer. Immediate postoperative MRI demonstrated GTR of the lesion without new ischemic changes or complications and only minimal evidence of a surgical corridor (Fig. 3B–D).

Additional Case Illustrations

An additional 8 cases are illustrated (Figs. 512). In lieu of providing imaging of all 20 cases, which we felt would be redundant, these additional 8 cases are representative of the spectrum of STR, NTR, and GTR obtained using both endoscopic and microscopic visualization.

FIG. 5.
FIG. 5.

Case 1. Endoscopic transportal GTR of lung cancer metastasis. Preoperative axial (A) and sagittal (B) T1-weighted images after Gd contrast administration demonstrate a right cerebellar lesion. Axial T1-weighted images pre- (C) and post- (D) Gd contrast administration obtained 1 day after surgery demonstrate complete resection and residual hyperintensity consistent with blood products. Axial T1-weighted images, pre- (E) and post-Gd contrast administration (F), obtained 3 months after surgery demonstrate GTR of the lesion.

FIG. 6.
FIG. 6.

Case 2. Endoscopic transportal NTR of breast cancer metastasis. Preoperative axial (A) and sagittal (B) T1-weighted images after Gd contrast administration demonstrate a right cerebellar lesion. Axial T1-weighted images pre- (C) and (D) post-Gd contrast administration obtained 1 day after surgery demonstrate minor residual enhancement within the surgical bed (white arrow).

FIG. 7.
FIG. 7.

Case 4. Endoscopic transportal STR of a primitive neuroectodermal tumor. Preoperative sagittal (A) and axial (B) T1-weighted images after Gd contrast administration demonstrate a large lesion within the left frontal lobe. Postoperative axial T1-weighted images pre- (C) and (D) post-Gd contrast administration demonstrate residual enhancement (white arrows). Residual enhancement is further visualized on the postoperative sagittal T1-weighted MR image (E) and demonstrative of STR.

FIG. 8.
FIG. 8.

Case 8. Microscopic transportal GTR of lung cancer metastasis. Axial (A) and sagittal (B) T1-weighted images obtained after the administration of the Gd contrast agent demonstrate a lesion within the left basal ganglia. T1-weighted images after Gd contrast administration obtained 1 day after surgery demonstrate GTR. The punctate area of enhancement (white arrows) seen on the axial image (C) represents normal choroid plexus, which is better visualized on the coronal image (D).

FIG. 9.
FIG. 9.

Case 9. Microscopic transportal GTR of low-grade glioma. Preoperative (left) and postoperative (right) axial T2-weighted FLAIR images demonstrate a right temporal lesion that was successfully grossly resected with expected postoperative FLAIR changes.

FIG. 10.
FIG. 10.

Case 12. Microscopic transportal GTRof glioblastoma multiforme. Preoperative axial (A) and sagittal (B) T1-weighted images after Gd contrast administration demonstrate a right temporo-occipital lesion. Postoperative axial T1-weighted images before (C) and after (D) contrast administration demonstrate GTR. The area of enhancement (white arrow) represents normal choroid plexus.

FIG. 11.
FIG. 11.

Case 16. Microscopic transportal NTR of glioblastoma multiforme. Preoperative axial (A), coronal (B), and sagittal (C) T1-weighted images after Gd contrast administration demonstrate a lesion within the right basal ganglia and thalamus. Postoperative sagittal (D) and axial (E) T1-weighted images before contrast administration are shown. After contrast administration, axial (F) and coronal (G) images demonstrate residual enhancement (white arrows) suggestive of NTR.

FIG. 12.
FIG. 12.

Case 6. Microscopic transportal NTR of glioblastoma multiforme. Preoperative axial (A) and coronal (B) T1-weighted images after Gd contrast administration demonstrate a lesion within the left basal ganglia. Postoperative axial (C), sagittal (D), and coronal (E) T1-weighted images after contrast administration demonstrate NTR of the lesion and minimal evidence of a surgical corridor. However, residual enhancement (white arrow) is seen on the axial T1-weighted image (F) within the tumor bed.

Results

GTR was the goal in all 20 patients. EOR was considered GTR in 14 of 20 (70%), NTR (> 95%) in 4 of 20 (20%), and STR (< 90%) in 2 of 20 patients (10%). Incomplete resection was associated with basal ganglia location (p < 0.05) and the use of the endoscope (p < 0.002). Four of 5 (80%) endoscopic cases were NTR (2) or STR (2). Histology, presenting neurological symptoms, and demographics were not associated with EOR. The rates of postoperative complications, including new neurological deficits and MRI evidence of brain injury, were low and similar between groups. These data are outlined in Table 1.

The most common location operated on using the port was the basal ganglia (11 patients), followed by the cerebellum (4), frontal lobe (2), temporal lobe (2), and parietal lobe (1). The final pathology of the resected lesion included metastatic tumors (8 patients), glioma (7), meningioma (1), neurocytoma (1), radiation necrosis (1), primitive neuroectodermal tumor (1), and hemangioblastoma (1). Neurological symptoms at the time of presentation included headache (5 patients), altered mental status (4), seizures (4), ataxia (3), motor weakness (3), visual changes (1), dysarthria (1), and asymptomatic presentation (1).

There were no significant differences in the histology of the resected lesion in the endoscope- versus microscope-assisted cases. The most common histology represented was metastasis, which comprised 2 of 5 (40%) endoscope-assisted cases and 6 of 15 (40%) microscope-assisted cases. Likewise, lesion location was represented similarly between endoscope- and microscope-assisted cases. The basal ganglia was the most common site of operation and comprised 2 of 5 (40%) and 9 of 15 (60%) of the endoscope- and microscope-assisted resections, respectively. The location of the lesion within the basal ganglia was significantly associated with incomplete resection, irrespective of using an endoscope or microscope. Of the 6 cases of incomplete resection (Cases 2, 3, 4, 5, 6, and 16), a significant majority (4 of 6; 66%) involved lesions within the basal ganglia (p < 0.05).

All cases began with use of the 12 mm × 5 cm or 7 cm-sized port. Four cases, all of which involved lesions within the basal ganglia, required the additional use of a larger diameter 17-mm port (Cases 5, 15, 17, and 18). GTR was achieved in 3 of these 4 cases. The lone case with NTR involved endoscopic visualization through the port (Case 5).

Discussion

At our institution, we initially performed port surgery utilizing both the microscope and endoscope. In addition to extensive use of the microscope in nonport procedures, we have extensive experience using the endoscope for minimally invasive, transnasal approaches to the anterior skull base, which we have described in the past.6,15,30 We also detailed the endoscopic port technique in a 2-case series: 1 resection of a third ventricular colloid cyst, and 1 resection of parenchymal brain metastasis.23 Briefly, we use the microscope to assist traversing the depth of the sulcus, after which we proceeded with cannulation and endoscopic visualization through the port. We found that a 4-mm rigid endoscope and 2 instruments could adequately fit through the port cannula, allowing for bimanual surgical techniques. However, the presence of the endoscope inside the port was noted to decrease the freedom of movement of the other instruments, limit fine dissection, and prolong surgery. Our initial impression was that to perform surgery with the microscope using tubular retractors would require larger tubes greater than 20 mm in diameter as originally described by Patrick Kelly.16,17 At that time, the rationale for a large tube was based on the optical and lighting physics of the microscope, such that only with a certain minimal port diameter would the surgeon be able to triangulate the vision of both eyes on the depth of the cylinder in order to provide 3D visualization. Based on this assumption, endoscopic assistance was thought to be the optimal choice for minimally invasive port-assisted surgery using smaller diameter ports.8,26 However, with recent improvements in microscope technology, the possibility of stereoscopic visualization through narrow spaces became possible, conferring the potential advantage for microscope-assisted port surgery. Without an endoscope occupying the space inside the port, the freedom of movement increases and adequate visualization is possible with modern microscopes. It is important to mention that, for specific cases, it is certainly possible to use the endoscope at the end of the resection through the port to inspect the final cavity and confirm total resection. This technique may be particularly helpful when resecting intraventricular tumors.

Noting the advantages of microscopic visualization, we started to exclusively use the microscope during port surgery and performed the current retrospective analysis to evaluate our hypothesis. All of the data in this report stem from our initial 8 months of performing port surgery in order to limit the learning curve as a confounding factor. Our results suggest that incomplete resection of target lesions was significantly associated with endoscope-assisted visualization during port surgery and that microscope-assisted visualization afforded higher rates of total resection. Similarly, other groups have described successful results using the microscope with the port to resect lesions. Herrera et al. described 10 patients undergoing microscope-assisted resection of brain tumors with the port.11 They reported GTR in all but 1 patient. Similarly, Raza et al. achieved total resection with microscope-assisted port surgery in 6 of 7 patients, as well as 2 additional patients undergoing biopsy.31 Similar to our first case illustration (Case 14), these authors presented postoperative diffusion-weighted MRI to demonstrate minimal ischemic injury to the normal brain parenchyma after microscope-assisted port surgery. Lastly, in a case series of 4 patients, Recinos et al. documented the successful use of port surgery with the microscope in a pediatric population.32 Total resection was achieved in 2 of 4 patients, both of whom had deep-seated gliomas. Our data builds on these prior reports by providing results for a different range of pathological entities and comparing the results to an alternative technique for visualization using the port.

Our data also indicate that STR was more commonly achieved with lesions located deep within the basal ganglia. Among the aforementioned studies, incomplete resection associated with the basal ganglia location was described in a 10-year-old male patient who had NTR of a dysembryoplastic neuroepithelial tumor.32 Likewise, STR was documented in 3 adult patients with gliomas, although the locations of their lesions were not reported. These cases all involved visualization with loupe magnification, suggesting that port surgery with loupes may lead to suboptimal surgical outcomes. Interestingly, among the 2 reported cases of microscopic port surgery for papillary tumors within the pineal region, neither achieved GTR.31,32 Furthermore, 1 patient, a 15-month-old male, developed an aqueductal hematoma that caused hydrocephalus, although this clot was successfully removed via the port with minimal gross injury to the brain parenchyma.32 Although no further details were given, one possibility is that the port may be too bulky of a structure to access the pineal region via a typical midline infratentorial-supracerebellar approach. This is supported by the fact that both patients had evidence of adverse FLAIR changes and diffusion restriction on postoperative MRI.

The results presented in this study indicate 3 major advantages that the microscope confers over the endoscope during port surgery. First, the microscope allows a binocular 3D impression of the surgical field, which facilitates accurate and efficient manipulation of the surgical instruments. In support of this notion, compared with traditional 2D endoscopic views, newer 3D endoscopes reduce operating times and shorten learning curves.3 Second, the absence of an endoscope frees up additional space within the port for more instruments. As such, we often perform microsurgery with a third assisting hand to provide additional suction or microretraction. Third, the independent positioning of the microscope permits faster and more precise readjustments of the port during surgery. Use of the endoscope requires the removal of the scope prior to port manipulation, which prohibits continued close-up views of the surgical bed during the repositioning of the port. As such, in most circumstances, the microscope is preferable to the endoscope during port surgery. However, certain older microscopes may preclude microscope-assisted port surgery due to a wider aperture distance between each eye, which prevents adequate binocular depth perception through the limited diameter of the port. Current microscopes decrease this width and provide more optimally focused lighting, thereby allowing for clear views of the surgical bed.

When evaluating patients for possible port-assisted surgery, a number of factors are considered. The anatomic location of the tumor and presumed histology are 2 key factors that guide this decision. In general, we found tumors located in the cerebellar hemispheres, deep white matter of the cerebral hemispheres, and basal ganglia to be ideal candidates for port-assisted surgery. Superficial hemispheric lesions (< 3 cm from the surface at the deepest point) can be removed using standard open microsurgical techniques, and the addition of the port is unlikely to confer an advantage. Deep white matter and basal ganglia lesions allow the advantages of the port to be realized, including minimizing collateral tissue damage by evenly distributing the radial retraction of surrounding tissue along the white matter tracts in combination with a minimally sized craniotomy. Imaging such as functional MRI and diffusion tensor imaging are commonly used in coordination with standard neuro-navigation MRI to preoperatively plan the entry point and trajectory of the port. This planning is used to determine the appropriate incision and craniotomy. The advantages of the port are somewhat different for cerebellar lesions. The primary advantage of the port for approaching cerebellar tumors is the minimization of the incision and craniotomy, which we have anecdotally found to decrease postoperative pain, although pain was not an outcome evaluated in this study. Preoperative planning for posterior fossa lesions involved developing a trajectory that minimized the length of the aperture while avoiding vascular structures such as the transverse sinus, rather than critical neural structures as with supratento-rial approaches. Another difference involved techniques to minimize the risk of cerebrospinal fluid leak, which was less of a concern with supratentorial approaches.

An advantage of microscope-assisted transportal surgery, as described here, in comparison with endoscope-assisted port surgery is the freedom to make small adjustments in the trajectory of the port during surgery in order to visualize various parts of the target lesion. With a fixed endoscope, the endoscope-port apparatus must first be disconnected, readjusted without direct visualization, and then reconnected. With the microscope, small adjustments in the port can be made under direct visualization. This is often either the depth of the port or the trajectory. If the trajectory is adjusted, such as for large tumors or to visualize the walls of the resection cavity, the surface of the brain is typically considered the “fulcrum” during movement with the distal tip of the port moving radially outward from its baseline position. Thus, the distal end of the port moves the greatest distance during any adjustment, which is safest since the tip is typically within the lesion. In reality, the actual movements are small, likely no more than 15° in any direction. Avoiding morbidity when adjusting the port requires preventing translational movement of the proximal aspect of the port across/into the surface of the brain (i.e., keeping the entry point into the brain as the “fulcrum” of any port movements), carefully selecting the entry point through the sulcus near the target or the midpoint of a gyrus, and selecting a trajectory parallel to the white matter tracts while avoiding the eloquent structures as much as possible. We also periodically check the entry point of the port under direct visualization to ensure that brain relaxation during surgery has not negatively impacted positioning.

The presumed histological diagnosis is the other main factor that impacts the decision to use the port to access deep-seated lesions. Histological entities felt to favor the use of the port include tumors with a “soft” or “suckable” consistency, such as many metastatic tumors (e.g., breast cancer and melanoma; Cases 2, 14, and 17) and high-grade gliomas (Cases 5, 6, 12, 16, 18, and 19). Nonneoplastic entities such as hematomas are also amenable to the use of the port, as the soft consistency facilitates the use of the suction instrument to assist with resection and promotes collapse of the surrounding brain around the resection cavity during surgery, thereby minimizing the need for manipulation of the port. Firm tumors, such as meningiomas, recurrent glial tumors with significant scar tissue, or metastatic sarcoma, are more likely to be less amenable to the use of the port due to the difficulty of manipulating these lesions within the aperture of the port. Nevertheless, the utilization of an ultrasonic aspirator and suction cutter device, such as the Nico Myriad, can facilitate the resection of these dense tumors through port access (Cases 15 and 16). Lesions associated with a significant potential for hemorrhage, such as renal cell carcinoma metastases, may present difficulties when using the port, as intralesional piecemeal resection would likely be complicated by significant bleeding, thereby increasing the difficulty and time of the surgery through the port. Tumor size was felt to be less important than histology and anatomical location in achieving the successful surgical resection of deep-seated lesions. Generally, a safe trajectory toward a tumor with an appropriately soft consistency renders size less important because the tumor is easily dissected and removed through the port. Typically, pressure from the surrounding brain assists with coaxing the peripheral portions of the tumor toward the central aspects of the visualized cavity, thereby facilitating removal. Firmer tumors—such as meningiomas, certain gliomas, firmer metastases, and recurrent tumors with associated scar tissue and greater size-may increase the difficulty of achieving total resection or increase the risks of morbidity due to a greater degree of manipulation of the port needed to visualize the entire tumor. Soft consistency definitely mitigates size as a factor in achieving GTR. Future work will be necessary to accurately determine the impact of tumor size on the EOR in port-assisted surgery.

These considerations were factored into decisions regarding how to approach the lesions using the port in this case series, and we did not have to abort the use of the port and convert to open surgery or expand craniotomy during any of the 20 cases reported here. However, for each case, the surgical field was prepared such that we could easily expand craniotomy for open surgery. One complication that we did not encounter was herniation of the brain through limited craniotomy, which was a concern given that many of the lesions were associated with significant cerebral edema. This was likely avoided due to the minimal dural opening and careful attention to measures taken prior to surgery, including positioning and osmotic diuresis.

Future work, which has already begun, will involve prospective assessments of microscope-assisted port surgery to include variables such as length of hospital stay, postoperative pain, and preoperative variables that influence the decision to perform a surgical approach, including whether to use the port and the chosen trajectory. This prospective analysis may yield additional factors important for transportal surgery planning and lead to the development of a classification scheme for deep-seated lesions, which may be candidates for surgical resection.

Conclusions

A minimally invasive neurosurgical approach using a transparent tubular port can provide a safe and effective option for patients with deep-seated brain tumors. Options for visualization through the port include loupes, endoscopic assistance, and microscopic assistance. Using current technology, our results show that EOR was improved with the use of the microscope in comparison with the endoscope for visualization. The factors underlying the advantages of the microscope include the 3D field of view, improved lighting, increased freedom of movements, and greater efficiency of manipulation during angle readjustments and repositioning. At this point, we have largely abandoned the endoscope as the main visualization tool for transportal brain surgery. As such, our findings further define the technical considerations for minimally invasive, transportal resection of intracranial lesions, and may impact operative decisions in neurosurgical patients. In the future, further work will be necessary to determine if additional advancements in surgical field visualization, such as the use of 2D exoscopes and 3D endoscopes, can improve on the results of the 2D endoscope and compare favorably to the microscope.

Acknowledgment

We wish to acknowledge Ryan Hallinan, medical instrumentation specialist, for assistance in the filming of the video accompanying this study.

Author Contributions

Conception and design: Elder, Prevedello. Acquisition of data: all authors. Analysis and interpretation of data: all authors. Drafting the article: all authors. Critically revising the article: all authors. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Elder. Statistical analysis: all authors. Administrative/technical/material support: all authors. Study supervision: all authors.

References

  • 1

    Albin MSBunegin LDujovny MBennett MHJannetta PJWisotzkey HM: Brain retraction pressure during intracranial procedures. Surg Forum 26:4995001975

  • 2

    Andrews RJBringas JR: A review of brain retraction and recommendations for minimizing intraoperative brain injury. Neurosurgery 33:105210641993

  • 3

    Barkhoudarian GDel Carmen BecerraRomero ALaws ER: Evaluation of the 3-dimensional endoscope in transsphenoidal surgery. Neurosurgery 73:1 Suppl Operativeons74ons792013

  • 4

    Bennett MHAlbin MSBunegin LDujovny MHellstrom HJannetta PJ: Evoked potential changes during brain retraction in dogs. Stroke 8:4874921977

  • 5

    Cabbell KLRoss DA: Stereotactic microsurgical craniotomy for the treatment of third ventricular colloid cysts. Neurosurgery 38:3013071996

  • 6

    Carrau RLPrevedello DMde Lara DDurmus KOzer E: Combined transoral robotic surgery and endoscopic endonasal approach for the resection of extensive malignancies of the skull base. Head Neck 35:E351E3582013

  • 7

    Chotigavanichaya CKorwutthikulrangsri ESuratkarndawadee SRuangchainikom MWatthanaapisith TTanapipatsiri S: Minimally invasive lumbar disectomy with the tubular retractor system: 4–7 years follow-up. J Med Assoc Thai 95:Suppl 9S82S862012

  • 8

    Engh JALunsford LDAmin DVOchalski PGFernandez-Miranda JPrevedello DM: Stereotactically guided endoscopic port surgery for intraventricular tumor and colloid cyst resection. Neurosurgery 67:3 Suppl Operativeons198ons2052010

  • 9

    Feldman ZReichenthal EZachari ZShapira YArtru AA: Mannitol, intracranial pressure and vasogenic edema. Neurosurgery 36:123612371995

  • 10

    Franke JGreiner-Perth RBoehm HMahlfeld KGrasshoff HAllam Y: Comparison of a minimally invasive procedure versus standard microscopic discotomy: a prospective randomised controlled clinical trial. Eur Spine J 18:99210002009

  • 11

    Herrera SRShin JHChan MKouloumberis PGoellner ESlavin KV: Use of transparent plastic tubular retractor in surgery for deep brain lesions: a case series. Surg Technol Int 19:47502010

  • 12

    Horwitz MJ: The Leyla retractor: use in acoustic neuroma and neurotologic surgery. Otolaryngology 86:ORL-934ORL-9351978

  • 13

    Jacewicz MBrint STanabe JPulsinelli WA: Continuous nimodipine treatment attenuates cortical infarction in rats subjected to 24 hours of focal cerebral ischemia. J Cereb Blood Flow Metab 10:89961990

  • 14

    Kahilogullari GBeton SAl-Beyati ESKantarcioglu OBozkurt MKantarcioglu E: Olfactory functions after transsphenoidal pituitary surgery: endoscopic versus microscopic approach. Laryngoscope 123:211221192013

  • 15

    Kassam ABPrevedello DMCarrau RLSnyderman CHThomas AGardner P: Endoscopic endonasal skull base surgery: analysis of complications in the authors’ initial 800 patients. J Neurosurg 114:154415682011

  • 16

    Kelly PJ: Future perspectives in stereotactic neurosurgery: stereotactic microsurgical removal of deep brain tumors. J Neurosurg Sci 33:1491541989

  • 17

    Kelly PJGoerss SJKall BA: The stereotaxic retractor in computer-assisted stereotaxic microsurgery. Technical note. J Neurosurg 69:3013061988

  • 18

    Kelly PJKall BAGoerss SJ: Computer-interactive stereotactic resection of deep-seated and centrally located intra-axial brain lesions. Appl Neurophysiol 50:1071131987

  • 19

    Kotwal SKawaguchi SLebl DHughes AHuang RSama A: Minimally invasive lateral lumbar interbody fusion: clinical and radiographic outcome at a minimum 2-year follow-up. J Spinal Disord Tech 28:1191252015

  • 20

    Leksell LLindquist CAdler JRLeksell DJernberg BSteiner L: A new fixation device for the Leksell stereotaxic system. Technical note. J Neurosurg 66:6266291987

  • 21

    Lo EHSteinberg GK: Effects of dextromethorphan on regional cerebral blood flow in focal cerebral ischemia. J Cereb Blood Flow Metab 11:8038091991

  • 22

    McLaughlin NEisenberg AACohan PChaloner CBKelly DF: Value of endoscopy for maximizing tumor removal in endonasal transsphenoidal pituitary adenoma surgery. J Neurosurg 118:6136202013

  • 23

    McLaughlin NPrevedello DMEngh JKelly DFKassam AB: Endoneurosurgical resection of intraventricular and intraparenchymal lesions using the port technique. World Neurosurg 79:2 SupplS18.e1S18.e82013

  • 24

    Meyer FBAnderson RESundt TM JrYaksh TL: Treatment of experimental focal cerebral ischemia with mannitol. Assessment by intracellular brain pH, cortical blood flow, and electroencephalography. J Neurosurg 66:1091151987

  • 25

    Moshel YALink MJKelly PJ: Stereotactic volumetric resection of thalamic pilocytic astrocytomas. Neurosurgery 61:66752007

  • 26

    Ochalski PGFernandez-Miranda JCPrevedello DMPollack IFEngh JA: Endoscopic port surgery for resection of lesions of the cerebellar peduncles: technical note. Neurosurgery 68:144414512011

  • 27

    Otsuki TJokura HYoshimoto T: Stereotactic guiding tube for open-system endoscopy: a new approach for the stereotactic endoscopic resection of intra-axial brain tumors. Neurosurgery 27:3263301990

  • 28

    Patil AA: Free-standing, stereotactic, microsurgical retraction technique in “key hole” intracranial procedures. Acta Neurochir (Wien) 108:1481531991

  • 29

    Popov VAnderson DG: Minimal invasive decompression for lumbar spinal stenosis. Adv Orthop 2012:6453212012

  • 30

    Prevedello DMEbner FHde Lara DDitzel Filho LOtto BACarrau RL: Extracapsular dissection technique with the cotton swab for pituitary adenomas through an endoscopic endonasal approach — how I do it. Acta Neurochir (Wien) 155:162916322013

  • 31

    Raza SMRecinos PFAvendano JAdams HJallo GIQuinones-Hinojosa A: Minimally invasive trans-portal resection of deep intracranial lesions. Minim Invasive Neurosurg 54:5112011

  • 32

    Recinos PFRaza SMJallo GIRecinos VR: Use of a minimally invasive tubular retraction system for deep-seated tumors in pediatric patients. J Neurosurg Pediatr 7:5165212011

  • 33

    Takemura YInoue TMorishita TRhoton AL Jr: Comparison of microscopic and endoscopic approaches to the cerebellopontine angle. World Neurosurg 82:4274412014

  • 34

    Van Rompaey JBush CMcKinnon BSolares AC: Minimally invasive access to the posterior cranial fossa: an anatomical study comparing a retrosigmoidal endoscopic approach to a microscopic approach. J Neurol Surg A Cent Eur Neurosurg 74:162013

  • 35

    Yadav YRYadav SSherekar SParihar V: A new minimally invasive tubular brain retractor system for surgery of deep intracerebral hematoma. Neurol India 59:74772011

  • 36

    Zamorano LMartinez-Coll ADujovny M: Transposition of image-defined trajectories into arc-quadrant centered stereotactic systems. Acta Neurochir Suppl (Wien) 46:1091111989

If the inline PDF is not rendering correctly, you can download the PDF file here.

Article Information

Correspondence J. Bradley Elder, 410 W. 10th Ave., Doan Hall, N1052, Columbus, OH 43210. email: brad.elder@osumc.edu.

INCLUDE WHEN CITING Published online August 28, 2015; DOI: 10.3171/2015.1.JNS141113.

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

© AANS, except where prohibited by US copyright law.

Headings

Figures

  • View in gallery

    Case 14. Microscopic transportal GTR of melanoma metastasis. Preoperative axial T1-weighted MR image (A) after Gd contrast administration demonstrates a left parietal metastasis from melanoma with significant vasogenic edema. Axial T1- (B) and T2-weighted (C) images after Gd contrast administration obtained 1 day after surgery demonstrate complete resection with a minimal surgical corridor and expected postoperative FLAIR changes. Axial T2- (D) and diffusion-weighted (E) images demonstrate the significant reduction of surgical edema and no evidence of ischemia along the surgical corridor 2 months after surgery.

  • View in gallery

    Vycor port with Stryker navigation wand embedded in bone wax (inset, top left), which allows for navigation guidance of the port into the tumor, as depicted on the navigation screen to the right of the surgeon. Once the port has achieved the desired position, either the endoscope or microscope can be used for tumor resection via the port. Figure is available in color online only.

  • View in gallery

    Case 13. Microscopic transportal GTR of ovarian cancer metastasis. Preoperative axial T1-weighted image (A) after Gd contrast administration demonstrates a heterogeneously enhancing metastatic lesion deep within the right basal ganglia. Axial T1-weighted image after Gd contrast administration (B) and axial T2-weighted FLAIR image (C) obtained 1 day after surgery showing total resection of the lesion and decompression of the ventricles. Postoperative coronal T1-weighted image (D) after Gd contrast administration demonstrates a minimal surgical corridor (white arrow).

  • View in gallery

    An intraoperative photograph of a 12-mm (width) × 7-cm (length) Vycor port maintaining the surgical corridor. Cotton is seen within the port. The port is attached to a flexible snake-arm retractor allowing for self-retaining but easily adjustable retraction during surgery. The normal brain is readily seen through the transparent walls of the port (arrowhead) and is evenly distributed along the rounded edges of the port (left-pointing arrow). Minute retractions of the port encourage spongy tumor tissue to emerge into view (right-pointing arrow). Figure is available in color online only.

  • View in gallery

    Case 1. Endoscopic transportal GTR of lung cancer metastasis. Preoperative axial (A) and sagittal (B) T1-weighted images after Gd contrast administration demonstrate a right cerebellar lesion. Axial T1-weighted images pre- (C) and post- (D) Gd contrast administration obtained 1 day after surgery demonstrate complete resection and residual hyperintensity consistent with blood products. Axial T1-weighted images, pre- (E) and post-Gd contrast administration (F), obtained 3 months after surgery demonstrate GTR of the lesion.

  • View in gallery

    Case 2. Endoscopic transportal NTR of breast cancer metastasis. Preoperative axial (A) and sagittal (B) T1-weighted images after Gd contrast administration demonstrate a right cerebellar lesion. Axial T1-weighted images pre- (C) and (D) post-Gd contrast administration obtained 1 day after surgery demonstrate minor residual enhancement within the surgical bed (white arrow).

  • View in gallery

    Case 4. Endoscopic transportal STR of a primitive neuroectodermal tumor. Preoperative sagittal (A) and axial (B) T1-weighted images after Gd contrast administration demonstrate a large lesion within the left frontal lobe. Postoperative axial T1-weighted images pre- (C) and (D) post-Gd contrast administration demonstrate residual enhancement (white arrows). Residual enhancement is further visualized on the postoperative sagittal T1-weighted MR image (E) and demonstrative of STR.

  • View in gallery

    Case 8. Microscopic transportal GTR of lung cancer metastasis. Axial (A) and sagittal (B) T1-weighted images obtained after the administration of the Gd contrast agent demonstrate a lesion within the left basal ganglia. T1-weighted images after Gd contrast administration obtained 1 day after surgery demonstrate GTR. The punctate area of enhancement (white arrows) seen on the axial image (C) represents normal choroid plexus, which is better visualized on the coronal image (D).

  • View in gallery

    Case 9. Microscopic transportal GTR of low-grade glioma. Preoperative (left) and postoperative (right) axial T2-weighted FLAIR images demonstrate a right temporal lesion that was successfully grossly resected with expected postoperative FLAIR changes.

  • View in gallery

    Case 12. Microscopic transportal GTRof glioblastoma multiforme. Preoperative axial (A) and sagittal (B) T1-weighted images after Gd contrast administration demonstrate a right temporo-occipital lesion. Postoperative axial T1-weighted images before (C) and after (D) contrast administration demonstrate GTR. The area of enhancement (white arrow) represents normal choroid plexus.

  • View in gallery

    Case 16. Microscopic transportal NTR of glioblastoma multiforme. Preoperative axial (A), coronal (B), and sagittal (C) T1-weighted images after Gd contrast administration demonstrate a lesion within the right basal ganglia and thalamus. Postoperative sagittal (D) and axial (E) T1-weighted images before contrast administration are shown. After contrast administration, axial (F) and coronal (G) images demonstrate residual enhancement (white arrows) suggestive of NTR.

  • View in gallery

    Case 6. Microscopic transportal NTR of glioblastoma multiforme. Preoperative axial (A) and coronal (B) T1-weighted images after Gd contrast administration demonstrate a lesion within the left basal ganglia. Postoperative axial (C), sagittal (D), and coronal (E) T1-weighted images after contrast administration demonstrate NTR of the lesion and minimal evidence of a surgical corridor. However, residual enhancement (white arrow) is seen on the axial T1-weighted image (F) within the tumor bed.

References

1

Albin MSBunegin LDujovny MBennett MHJannetta PJWisotzkey HM: Brain retraction pressure during intracranial procedures. Surg Forum 26:4995001975

2

Andrews RJBringas JR: A review of brain retraction and recommendations for minimizing intraoperative brain injury. Neurosurgery 33:105210641993

3

Barkhoudarian GDel Carmen BecerraRomero ALaws ER: Evaluation of the 3-dimensional endoscope in transsphenoidal surgery. Neurosurgery 73:1 Suppl Operativeons74ons792013

4

Bennett MHAlbin MSBunegin LDujovny MHellstrom HJannetta PJ: Evoked potential changes during brain retraction in dogs. Stroke 8:4874921977

5

Cabbell KLRoss DA: Stereotactic microsurgical craniotomy for the treatment of third ventricular colloid cysts. Neurosurgery 38:3013071996

6

Carrau RLPrevedello DMde Lara DDurmus KOzer E: Combined transoral robotic surgery and endoscopic endonasal approach for the resection of extensive malignancies of the skull base. Head Neck 35:E351E3582013

7

Chotigavanichaya CKorwutthikulrangsri ESuratkarndawadee SRuangchainikom MWatthanaapisith TTanapipatsiri S: Minimally invasive lumbar disectomy with the tubular retractor system: 4–7 years follow-up. J Med Assoc Thai 95:Suppl 9S82S862012

8

Engh JALunsford LDAmin DVOchalski PGFernandez-Miranda JPrevedello DM: Stereotactically guided endoscopic port surgery for intraventricular tumor and colloid cyst resection. Neurosurgery 67:3 Suppl Operativeons198ons2052010

9

Feldman ZReichenthal EZachari ZShapira YArtru AA: Mannitol, intracranial pressure and vasogenic edema. Neurosurgery 36:123612371995

10

Franke JGreiner-Perth RBoehm HMahlfeld KGrasshoff HAllam Y: Comparison of a minimally invasive procedure versus standard microscopic discotomy: a prospective randomised controlled clinical trial. Eur Spine J 18:99210002009

11

Herrera SRShin JHChan MKouloumberis PGoellner ESlavin KV: Use of transparent plastic tubular retractor in surgery for deep brain lesions: a case series. Surg Technol Int 19:47502010

12

Horwitz MJ: The Leyla retractor: use in acoustic neuroma and neurotologic surgery. Otolaryngology 86:ORL-934ORL-9351978

13

Jacewicz MBrint STanabe JPulsinelli WA: Continuous nimodipine treatment attenuates cortical infarction in rats subjected to 24 hours of focal cerebral ischemia. J Cereb Blood Flow Metab 10:89961990

14

Kahilogullari GBeton SAl-Beyati ESKantarcioglu OBozkurt MKantarcioglu E: Olfactory functions after transsphenoidal pituitary surgery: endoscopic versus microscopic approach. Laryngoscope 123:211221192013

15

Kassam ABPrevedello DMCarrau RLSnyderman CHThomas AGardner P: Endoscopic endonasal skull base surgery: analysis of complications in the authors’ initial 800 patients. J Neurosurg 114:154415682011

16

Kelly PJ: Future perspectives in stereotactic neurosurgery: stereotactic microsurgical removal of deep brain tumors. J Neurosurg Sci 33:1491541989

17

Kelly PJGoerss SJKall BA: The stereotaxic retractor in computer-assisted stereotaxic microsurgery. Technical note. J Neurosurg 69:3013061988

18

Kelly PJKall BAGoerss SJ: Computer-interactive stereotactic resection of deep-seated and centrally located intra-axial brain lesions. Appl Neurophysiol 50:1071131987

19

Kotwal SKawaguchi SLebl DHughes AHuang RSama A: Minimally invasive lateral lumbar interbody fusion: clinical and radiographic outcome at a minimum 2-year follow-up. J Spinal Disord Tech 28:1191252015

20

Leksell LLindquist CAdler JRLeksell DJernberg BSteiner L: A new fixation device for the Leksell stereotaxic system. Technical note. J Neurosurg 66:6266291987

21

Lo EHSteinberg GK: Effects of dextromethorphan on regional cerebral blood flow in focal cerebral ischemia. J Cereb Blood Flow Metab 11:8038091991

22

McLaughlin NEisenberg AACohan PChaloner CBKelly DF: Value of endoscopy for maximizing tumor removal in endonasal transsphenoidal pituitary adenoma surgery. J Neurosurg 118:6136202013

23

McLaughlin NPrevedello DMEngh JKelly DFKassam AB: Endoneurosurgical resection of intraventricular and intraparenchymal lesions using the port technique. World Neurosurg 79:2 SupplS18.e1S18.e82013

24

Meyer FBAnderson RESundt TM JrYaksh TL: Treatment of experimental focal cerebral ischemia with mannitol. Assessment by intracellular brain pH, cortical blood flow, and electroencephalography. J Neurosurg 66:1091151987

25

Moshel YALink MJKelly PJ: Stereotactic volumetric resection of thalamic pilocytic astrocytomas. Neurosurgery 61:66752007

26

Ochalski PGFernandez-Miranda JCPrevedello DMPollack IFEngh JA: Endoscopic port surgery for resection of lesions of the cerebellar peduncles: technical note. Neurosurgery 68:144414512011

27

Otsuki TJokura HYoshimoto T: Stereotactic guiding tube for open-system endoscopy: a new approach for the stereotactic endoscopic resection of intra-axial brain tumors. Neurosurgery 27:3263301990

28

Patil AA: Free-standing, stereotactic, microsurgical retraction technique in “key hole” intracranial procedures. Acta Neurochir (Wien) 108:1481531991

29

Popov VAnderson DG: Minimal invasive decompression for lumbar spinal stenosis. Adv Orthop 2012:6453212012

30

Prevedello DMEbner FHde Lara DDitzel Filho LOtto BACarrau RL: Extracapsular dissection technique with the cotton swab for pituitary adenomas through an endoscopic endonasal approach — how I do it. Acta Neurochir (Wien) 155:162916322013

31

Raza SMRecinos PFAvendano JAdams HJallo GIQuinones-Hinojosa A: Minimally invasive trans-portal resection of deep intracranial lesions. Minim Invasive Neurosurg 54:5112011

32

Recinos PFRaza SMJallo GIRecinos VR: Use of a minimally invasive tubular retraction system for deep-seated tumors in pediatric patients. J Neurosurg Pediatr 7:5165212011

33

Takemura YInoue TMorishita TRhoton AL Jr: Comparison of microscopic and endoscopic approaches to the cerebellopontine angle. World Neurosurg 82:4274412014

34

Van Rompaey JBush CMcKinnon BSolares AC: Minimally invasive access to the posterior cranial fossa: an anatomical study comparing a retrosigmoidal endoscopic approach to a microscopic approach. J Neurol Surg A Cent Eur Neurosurg 74:162013

35

Yadav YRYadav SSherekar SParihar V: A new minimally invasive tubular brain retractor system for surgery of deep intracerebral hematoma. Neurol India 59:74772011

36

Zamorano LMartinez-Coll ADujovny M: Transposition of image-defined trajectories into arc-quadrant centered stereotactic systems. Acta Neurochir Suppl (Wien) 46:1091111989

TrendMD

Metrics

Metrics

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 201 201 93
PDF Downloads 159 159 61
EPUB Downloads 0 0 0

PubMed

Google Scholar