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Minimally Invasive Endoscopic Resection of Intraparenchymal Brain Tumors Puneet Plaha1, Laurent J. Livermore1, Natalie Voets2, Erlick Pereira1, Simon Cudlip1

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Key words Brain tumor - Endoscopy - Intraparenchymal - Minimally invasive -

Abbreviations and Acronyms 3D: Three-dimensional ACA: Anterior cerebral artery CT: Computed tomography FLAIR: Fluid attenuated inversion recovery MRI: Magnetic resonance imaging WHO: World Health Organization From the 1Department of Neurosurgery, John Radcliffe Hospital, Oxford University Hospitals NHS Trust, Oxford; and 2Oxford Centre for MRI of the Brain, Nuffield Department of Clinical Neuroscience, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom To whom correspondence should be addressed: Puneet Plaha, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2014) 82, 6:1198-1208. http://dx.doi.org/10.1016/j.wneu.2014.07.034 Supplementary digital content available online. Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter Crown Copyright ª 2014 Published by Elsevier Inc. All rights reserved.

INTRODUCTION Resection of intraparenchymal brain tumors has evolved significantly over the last few decades. High-resolution microscopes, intraoperative image guidance, intraoperative magnetic resonance imaging (MRI), diffusion tensor imaging to identify white fiber tracts, and functional MRI have been introduced in the operating room to help the surgeon maximize tumor resection and reduce morbidity and mortality. The endoscope is another tool that has developed in parallel with high-definition cameras and viewing screens and, more recently, threedimensional (3D) cameras. The endoscope has traditionally been used in neurosurgery to access a lesion within a natural body cavity (i.e., the cerebral ventricular system). The challenge has been to access and resect deep-seated intraparenchymal lesions using a minimally invasive endoscopic technique. Kelly pioneered the development of a stereotactic frameeguided cylinder retractor

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- OBJECTIVE:

To report a minimally invasive, nontubular endoscopic technique to resect intraparenchymal brain tumors and assess the feasibility, safety, and surgical resection margins achievable by this novel technique.

- METHODS:

Over a 21-month period, 48 patients underwent 50 consecutive endoscopic intraparenchymal tumor resections. Data on surgical morbidity and mortality and length of stay were collected prospectively. The percentage of surgical resection and residual tumor volumes were calculated using preoperative and postoperative volume computed tomography or magnetic resonance imaging. All tumors were resected through a 2-cm minicraniotomy using a highdefinition rigid endoscope with a 30-degree viewing angle. Bimanual resection was performed using standard microsurgical technique.

- RESULTS:

Mean patient age was 53 years. There were 42 supratentorial (19 frontal, 17 temporal, 3 occipital, 1 parietal, and 2 parafalcine) tumors and 8 infratentorial tumors. Mean tumor volume was 41 cm3. There were 12 metastases, 24 glioblastomas, 4 World Health Organization grade III gliomas, 5 World Health Organization grade IeII gliomas, 3 meningiomas, and 2 hemangioblastomas. On volumetric analysis, the overall mean percent resection was 96%. In 70% of cases, >95% resection was achieved; total resection was achieved in 48% of cases. At 30 days postoperatively, there was 1 new postoperative neurologic deficit; there were no deaths during this period.

- CONCLUSIONS:

Our experience demonstrates that resection of intraparenchymal tumors using a minimally invasive endoscopic technique is technically feasible and safe, achieves good tumor resection margins, and has some potential advantages over a traditional microscopic technique.

system in an attempt to create a safe access corridor to perform laser excision of small brain lesions using the operating microscope (9, 10). Other investigators developed variations of this fixed tubular retractor system but were able to achieve total resection in only relatively small-sized lesions because of the fixed conduit and its small diameter (3, 5, 6, 18, 22). More recently, Kassam et al. (7) achieved good resection of tumors using an endoscopic bimanual technique through an 11.5-mm conduit (Neuroendoport, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA). Access to the tumor was obtained by adjusting the conduit trajectory multiple times throughout tumor surgery to facilitate resection of large lesions. Over the past 2 years, we have been exploring techniques to perform intraparenchymal tumor resection using the

rigid endoscope. We present our prospective single-center study of minimally invasive, transcranial, fully endoscopic, bimanual resection of both superficial and deep intraparenchymal brain tumors. The aim of this study was to assess the feasibility, safety, and surgical outcomes of this endoscopic approach.

MATERIALS AND METHODS Patients In a 21-month period between December 2011 and August 2013, 50 consecutive endoscopic resections of intraparenchymal brain tumors were performed on 48 patients. All patients were discussed at a neuro-oncology multidisciplinary team meeting before surgery as per United

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Kingdom national guidelines (1) with a management plan of surgical resection agreed on and patient consent given for the operations. All surgical procedures were performed by the senior author (P.P.). The mean age of patients was 53 years (range, 23e75 years). There 24 women and 24 men in the study. Of tumors, 42 (84%) were supratentorial. Based on the closest cortical surface used for access, tumors were classified as predominantly frontal (n ¼ 19), temporal (n ¼ 17), occipital (n ¼ 3), parietal (n ¼ 1), and parafalcine (n ¼ 2). There were 8 (16%) infratentorial tumors (all cerebellum). World Health Organization (WHO) performance grade was 0 in 66% of patients, grade I in 26%, grade II in 6%, and grade III in 2%. The most common preoperative neurologic symptom was headache (22% of cases). At the time of presentation, preoperative mild limb or facial weakness was seen in 20% of cases, cerebellar symptoms were seen in 12%, seizures were seen in 10%, short-term memory problems or confusion was seen in 10%, and speech deficits were seen in 8%. Volumetric assessment of preoperative imaging demonstrated a mean tumor volume of 41 cm3 (range, 2.4e131 cm3). The mean distance to the cortical surface for subcortical tumors was 8 mm (range, 1e32 mm). In 9 cases, the tumor came to the pial surface. First-time operations accounted for 40 cases, and 10 cases were repeat resections for recurrent tumors. Surgical Planning Planning neuronavigation imaging was acquired in patients using a 1.5-T MRI scanner. T1-weighted contrast-enhanced contiguous 1.25-mm axial slices were used to acquire a volume data set that was compatible with both neuronavigation software packages used (Brainlab; Brainlab AG, Munich, Germany, and StealthStation; Medtronic, Inc., Minneapolis, Minnesota, USA). Patients with tumor in an eloquent location underwent preoperative functional MRI and diffusion tensor imaging to plan a safe trajectory and determine extent of surgical resection. Patients underwent routine neuroanesthesia and endotracheal intubation. Patients with supratentorial tumors were placed in a supine (frontal and temporal tumors), lateral (parietal tumors), or prone (occipital tumors) position. Patients with cerebellar

ENDOSCOPIC RESECTION OF INTRAPARENCHYMAL TUMORS

tumors were placed in the park bench or semiprone position. In all cases, the patient’s head was immobilized with a Mayfield pinfixation device (Mayfield Clinic, Cincinnati, Ohio, USA). Frameless image guidance was used in all cases, and registration was performed using facial recognition or scalp fiducial markers for supratentorial or cerebellar tumors, respectively. Brainlab was used in 44 cases, and StealthStation was used in 6 cases. The endoscope stack, comprising a camera unit with light source and screen (Karl Storz GmbH & Co., Tuttlingen, Germany), was positioned behind the surgeon to allow maximum length on the camera and light source leads. A highdefinition screen was positioned directly opposite the surgeon and the assistant so as to be in the direct line of sight of the operating surgeon (Figure 1A). In all cases, a 30-degree, 4-mm-diameter, rigid endoscope was used (Karl Storz GmbH & Co.). Cortical entry site and trajectory were planned using the navigation guidance

system. We generally chose the shortest distance to the tumor avoiding eloquent areas of cortex where possible and limiting the extent of white matter tract resection as visualized on diffusion tensor imaging and functional MRI scans. A 3-cm “lazy S” or linear incision was made in the scalp over the planned area, and a 2- to 2.5-cm craniotomy (Figure 1B) was performed followed by a cruciate durotomy. For temporal tumors, the incision typically was in front of the tragus of the ear, and for frontal tumors, it was typically behind the hairline (Figure 1C and D). Endoscopic Resection Using the image guidance probe, a 1- to 1.5-cm corticotomy was performed over a noneloquent gyrus for a transcortical approach and in some cases an intrasulcal approach. The 30-degree rigid endoscope was introduced by the assistant surgeon. Using the image guidance trajectory, a 1- to 1.5-cm access corridor was created by

Figure 1. (A) Endoscopic operating room setup with high-definition screen positioned in line of sight of both surgeon and assistant. Assistant is to the right of the surgeon holding endoscope. (B) Standard 2-cm minicraniotomy. (C) Standard temporal incision. (D) Standard frontal incision.

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the surgeon down to the tumor. When the tumor was located, the access corridor was lined with Surgicel (Ethicon, Inc., Somerville, New Jersey, USA) and surgical patties (1.27 cm  3.81 cm) to protect the underlying brain. During the surgical resection, the corridor was irrigated with warm saline. With the endoscope held by the assistant, the surgeon was at liberty to use standard bimanual microsurgical techniques to perform tumor resection. Tumor resection was generally carried out using a malleable suction catheter (6F or 8F; Frazier suction handles; DTR Medical Ltd, Swansea, United Kingdom) in 1 hand and a slightly curved ultrasonic surgical aspirator with a microsuction tip (CUSA EXcel; Integra LifeSciences Corporation, Plainsboro, New Jersey, USA) in the other. A double suction technique using a combination of a 6F and 8F malleable suction catheter providing retraction and aspiration simultaneously was occasionally used. The malleable suction catheters can be “bent” to work around the “corners” of the resection cavity, which are very well visualized with the 30-degree angled optics of the endoscope. The most superficial and accessible part of the tumor was resected first, and the plane between the tumor and the surrounding brain was identified where possible. In some cases, the tumor was initially decompressed internally giving more space to visualize the capsule or tumor plane. The 30-degree angulation of the endoscopic view and the slight curve on the instruments allowed visualization and resection of a large tumor cavity through a very small cortical tract in all cases. The assistant’s role as camera operator was vital to provide appropriate visualization of the operative field. The key principle is to use the 30-degree view of the endoscope to position the scope at the opposite side of the corridor to the operating surgeon. For example, if the surgeon is working at the 6 o’clock position, the endoscope should be placed at the 12 o’clock position with the cone of light angled directly downward; if the surgeon moves to the 9 o’clock position, the endoscope should be moved to the 3 o’clock position and the angle of light rotated from looking up to looking horizontally across to the left, and so on (Figure 2). Care was taken to exert minimal retraction of the brain surrounding the surgical corridor by the endoscope and surgical instruments, but often a

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Figure 2. Hand orientation and position of 30-degree endoscope. (A and B) Operator using ultrasonic aspirator and suction, working inferiorly at the 6 o’clock position with assistant holding camera at 12 o’clock position, light angled vertically down. (C and D) Operator working laterally at 9 o’clock position with assistant holding camera at 3 o’clock position, light angled horizontally to left. (E and F) Operator at 12 o’clock position and camera at 6 o’clock position with light angled vertically up. T, tumor; B, normal brain; P, pattie; S, Surgicel.

temporary amount of very gentle retraction was applied to access the whole tumor. Hemostasis was achieved using standard microsurgical techniques with enhanced

visualization of bleeding points provided by the endoscopic image. Initially, if the endoscopic view was disrupted by blood or condensation, it was removed along with

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surrounding parenchyma. The diameter of the surgical instruments and wiped with a the operative corridor was measured in wet gauze and an endoscopic antifog agent cases where this could be identified. (ULTRASTOP; Sigmapharm Arzneimittel Patients had a follow-up examination in GmbH, Vienna, Austria), which decreased the neuro-oncology clinic 1 week after the need for endoscope cleaning. More discharge and then regularly under the care recently, we started using an endoscope of the clinical oncologist while undergoing with a foot pedaleoperated warm saline further adjuvant treatment. Patients who irrigation sheath, which provides excellent did not require adjuvant treatment were scope cleaning (Karl Storz GmbH & Co.). followed by at 3, 6, and 12 months and then When the tumor resection was complete, a annually as per our standard protocol. “360-degree spherical” gross inspection of Mean follow-up period was 10 months the cavity was performed with the endo(range, 30 daye21 months). scope to confirm that the planned surgical resection was achieved. The resection cavity was copiously irrigated with warm saline to RESULTS identify bleeding points, which were coagOf the 50 cases, histologic analysis ulated with bipolar diathermy. After demonstrated 12 were metastases (10 ensuring complete hemostasis, the resecadenocarcinomas [breast, lung, gastrointion bed and the surgical corridor were lined testinal tract primaries], 2 melanomas), 24 with a hemostatic agent, Surgicel. The dura were glioblastomas, 4 were WHO grade III mater was closed using interrupted nonabgliomas (2 anaplastic astrocytomas, 2 sorbable sutures and a dural sealant such as anaplastic oligodendrogliomas), 5 were DuraSeal (Covidien, Inc., Dublin, Ireland). WHO grade IeII gliomas (3 We did not use an extradural or astrocytomas, 1 oligodensubgaleal suction drain. The droglioma, 1 pilocytic astrocybone flap and skin were closed toma), 3 were meningiomas, in standard fashion. Videos and 2 were hemangioIeIV show examples of endoVideo available at blastomas. On volumetric scopic resection of a temporal WORLDNEUROSURGERY.org analysis, the mean percent metastasis (Video I), a frontal resection for all cases was 96% metastasis (Video II), a paraf(range, 73%e100%). Mean alcine metastasis (Video III), and a temporal glioblastoma multiforme postoperative residual volume was 2.4 cm3. (Video IV). Total resection achieved in 48% of all cases. In 70% of cases, >95% resection was Postoperative Imaging and Follow-Up achieved; >95% resection was achieved in All patients underwent postoperative im11 (92%) metastases, 14 (58%) glioblasaging within 24 hours (either volume actomas, 3 (75%) WHO grade III gliomas, 2 quired contrast-enhanced CT or MRI scan). (40%) WHO grade IeII gliomas, 3 (100%) 3D volumetric measurement of preoperameningiomas, and 2 (100%) hemangiotive and postoperative imaging studies was blastomas. Table 1 summarizes the extent performed using Brainlab iPlan volume of resection and complications in each acquisition software. Residual tumor was pathologic group. Examples of preoperadefined as any enhancement on T1 posttive and postoperative radiologic studies contrast MRI scan or on contrast-enhanced are shown in Figures 3e6. CT scan for high-grade lesions (glioma and No cases of hemorrhage were seen along metastasis) and meningioma. For lowthe operative corridor or contusion in the grade glioma, absence of fluid attenuated surrounding parenchyma on postoperative inversion recovery (FLAIR) signal on the CT imaging. On analysis of postoperative postoperative scan was used to define reFLAIR MRI, the average signal beyond the sidual tumor. Percentage of resection was edge of the tract was 1.2 mm (SD, 0.8). No calculated as follows: (preoperative tumor patient had any postoperative neurologic volume/postoperative tumor volume)  deficit attributable to this. The mean 100/preoperative tumor volume. Postdiameter of the operative tract was 10 mm operative imaging (CT and MRI, especially (range, 7e15 mm; SD, 1.7). FLAIR MRI) was analyzed for evidence of The mean operative time for all cases was hemorrhage, contusion, or edema along 3 hours 35 minutes ( SD, 1 hour 9 mithe operative corridor and in the nutes). In 49 of 50 cases, the estimated

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blood loss was 95% resection 95% resection 95% resection 95% resection 95% resection 95% resection 95% resection 95% resection was achieved. There is growing evidence to suggest that near-total resection affords significant improved survival. Lacroix et al. (14) demonstrated a survival advantage with 98% resection, and Sanai et al. (20) more recently reported a survival

advantage with 78% resection and that the biggest predictor of survival was seen with >95% resection. A more recent multicenter study confirmed that a gross total resection is a favorable prognostic factor compared with subtotal resection (13). Total resection rates in glioma surgery have also been shown to be significantly better with the use of 5-aminolevulinic acid (24). We now have the capability to perform endoscopic 5-aminolevulinic acid tumor resection, and preliminary results are encouraging. The extent of resection has also been shown to be important in low-grade gliomas. Smith et al. (23) demonstrated an increase in overall survival with >90% resection in a retrospective study of 216 low-grade gliomas and achieved this in 47% of cases. Although our numbers in this group are small, we achieved >90% resection in all but 1 (80%) of our lowgrade gliomas, demonstrating that satisfactory resections can be achieved with this endoscopic technique. There is good evidence that resection of solitary metastases prolongs life in patients with a high performance status (19), and we achieved complete resection in 11 of 12 cases (92%) in our endoscopic series. The case in which complete resection was not achieved involved a 57-yearold woman with a parafalcine frontal lung metastasis. Part of the tumor incorporating the pericallosal vessels was left in situ, and an 88% resection was achieved. There were three meningiomas in our series. The first patient was a young woman with multiple meningiomas that developed after she received radiotherapy as a child for leukemia. This patient had a temporal fossa meningioma arising from the floor and the lateral wall of the cavernous sinus. A Simpson grade II resection was achieved. The second patient had a left cerebellar hemisphere 23-mm intraparenchymal tumor. This patient had a history of carcinoma of the breast, and this new tumor was suspected to be a metastasis, but histology confirmed fibroblastic meningioma (WHO grade I). A small cuff of the tumor capsule was left adherent to a draining vein. The third patient had a mixed cystic/solid tumor in the left temporal lobe with the solid component arising from the lateral wall of the cavernous sinus and the tentorial edge. This tumor was an incidental finding on a brain scan the patient received after a fall.

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Table 2. Summary of Previously Reported Techniques for Accessing and Resecting Deep-Seated Lesions Author

Technique

Access Corridor

Endoscope/Microscope

Resection

Outcome

Limitations

Tubular conduit on stereotactic frame “Tulip retractor”

6 mm

Binocular optical system

Adapted microsurgical instruments via side window in conduit

6 lesions (2 metastases, astrocytoma, AVM, glioma, ICH)—total resection reported in all cases

Small lesions limited by size of conduit

Kelly et al., 1986 (10), 1988 (9)

Computer-assisted stereotactic laser excision via cylinder retractor system

2e3 cm

Microscopic

Bimanual laser assisted

1986: 83 lesions in 78 patients (9 vascular lesions, 14 metastases, 21 astrocytomas, 26 GBM, 8 miscellaneous)—total resection in 61 cases. 1988: 123 lesions reported, no resection outcomes given

Special stereotactic system for laser excision only

Otsuki et al., 1990 (18)

Tubular conduit on stereotactic frame

8 mm

0-degree endoscope

Adapted microsurgical instruments via side window in conduit

15 lesions (2 cavernous angiomas, 5 metastases, 1 lymphoma, 4 astrocytomas, 2 gliosis, 1 hematoma)—total resection in 8 small lesions; biopsy or aspiration in 7

Small lesions limited by size of conduit

Greenfield et al., 2008 (3)

METRx tubular retractors

14e22 mm

Microscopic

Bimanual

10 lesions (cavernous malformation, 6 metastases, 2 GBM, meningioma)—gross total resection in all cases

METRx tubular system designed for spinal procedures

Kassam et al., 2009 (7)

Neuroendoport conduit

11.5 mm

0-degree endoscope

Bimanual

21 lesions (3 cavernous, 1 hemangioblastoma, 12 metastases, 5 GBM)—total resection 38%, neartotal 28.6%, subtotal 33.3%

Multiple manipulations of conduit required to achieve maximal resection. Conduit cannot be used for tumors reaching pial surface

Jo et al., 2011 (6)

Transparent tubular conduit

11 mm

0-degree endoscope

Bimanual, microsurgical instruments

5 intraparenchymal cases (cavernous angioma, metastasis, 2 ganglioglioma, oligodendroglioma)—gross total resection in all cases

Small lesions (3 cm) limited by size of port; calcified lesions

Current study

Nontubular access corridor

10 mm

30-degree endoscope

Bimanual

50 lesions (12 metastases, 24 glioblastomas, 4 WHO grade III, 5 WHO grade IeII, 3 meningiomas, 2 hemangioblastomas)—total resection 48%, >95% resection 70%

Need further development of microsurgical instruments and access corridor

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AVM, arteriovenous malformation; ICH, intracranial hemorrhage; GBM, glioblastoma multiforme; WHO, World Health Organization.

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Jacques et al., 1980 (4, 5)

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TUMOR Figure 7. Endoscope versus microscope. (A) Drawing shows use of the divergent 30-degree angled endoscopic light source to visualize “around corners” resecting large lesions through a small access corridor. (B) Convergent linear light source of the microscope requires a large corticotomy to resect a large deep lesion.

She was asymptomatic on imaging surveillance for 2 years with a lesion slowly increasing in size. The lesion was resected, but diathermy was performed on part of the solid component along the lateral wall of the cavernous sinus and the tentorial edge (Simpson grade IV). We achieved 100% resection in both hemangioblastomas in the study.

Infections Database reported an 8% overall infection rate in 245 nonendoscopic craniotomies performed in our unit (17). We anticipate that our infection rates will continue to decrease because all our infections occurred early in our case series, and we have not had an infection in the last 25 cases since we made adaptations to our skin retraction technique.

Complications A patient with a medial frontal low-grade glioma (grade II oligodendroglioma) involving the gyrus rectus developed a left ACA infarct on the third postoperative day. During tumor resection, there was significant bleeding from an anomalous frontopolar branch of the ACA, which was controlled by coagulating the vessel. In this case, we extended the craniotomy because of brain swelling, and we used the microscope as an adjunct to ensure complete hemostasis. A combination of local pressure over the vessel, chemical hemostatic agents, and diathermy resulted in spasm of the ACA and subsequently an evolving infarct. At the present time, this patient has shown significant improvement since surgery with a Glasgow Coma Scale score of 15 and is mobile despite a right leg monoparesis. There were 3 superficial wound infections in our series and no brain abscess. There were no long-term sequelae in any of the 3 cases. An infection rate of 6%, as found in our study, compares favorably with published infection rates in craniotomies—a large multicenter study of 4758 craniotomies reported an overall infection rate of 6.6% (11). The Oxford Craniotomy

Advantages of the Endoscope Table 3 summarizes the advantages and disadvantages of our endoscopic technique and of standard microscopic technique. We discuss a few key advantages here. First is the excellent illumination afforded by the light source and the ability to insert the scope into the depth of the tumor cavity or deep into the brain allowing one to have one’s “eye” close to the operative site. The 30-degree divergent light source helps one to see beyond the direct line of vision and allows one to perform large tumor resections through a small scalp incision and a minimally invasive approach without the use of a retractor. This minimally invasive technique aims to reduce morbidity and length of hospital stay. Our median length of stay was 2 days (mean, 4.8 days), which is substantially less than a mean of 9.4 days reported for craniotomies in our department (17) or the median of 5 days reported in a large study of 400 craniotomies performed for excision of intraaxial brain tumors (21). With more experience and staff training, our length of hospital stay has been shortened to a 1-night hospital stay after surgery, and we are now moving toward performing these operations as day cases.

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Second, lesions with a cystic component are particularly suited for an endoscopic approach. The cyst effectively creates an access corridor, and initially accessing and draining the cyst allows one enough space and maneuverability to resect the solid component of the tumor or a mural nodule of a hemangioblastoma. Third, tumors on the cortical surface can be easily resected with a microscope, and perhaps most neurosurgeons would continue to use it for this indication. We have found the endoscope particularly useful in resecting deep subcortical tumors and tumors in the temporal fossa, posterior fossa, frontal lobe, and interhemispheric fissure. The endoscope is particularly useful for resecting tumors in the temporal and frontal lobes, which are conventionally resected through a frontotemporal craniotomy made larger than the size of the tumor, especially when one is performing a lobectomy. This large craniotomy is made to allow adequate illumination of anatomic structures at the depth of resection especially around the pericallosal artery complex/anterior skull base and medially along the tentorial edge with temporal lesions. The excellent illumination of the scope and 30-degree angulation of the light allows us to perform all frontal and temporal resections through a minimal access approach (Figures 1BeD and 7). An endoscopic approach also reduces the morbidity associated with the conventional frontotemporal craniotomy (temporalis muscle and subgaleal swelling and periorbital edema and hematoma). Similarly, with lesions in the posterior fossa, we have not considered it necessary to perform a conventional suboccipital craniotomy (Figure 5). With tumors in the interhemispheric fissure, we insert the endoscope along the falx with the 30-degree light angulation toward the medial cortical surface. Apart from the wide field of view, the endoscope can be used to retract the falx gently rather than applying a retractor on the cortical surface of the brain. At the present time, we do not use the endoscope in patients who require a large craniotomy for the operation to be performed awake with motor and speech mapping. A question concerns the wider application of this technique to the neurosurgery community. Using the endoscope over the microscope is unlikely to improve overall survival of patients with brain tumors, but it has advantages (Table 3).

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Table 3. Advantages and Disadvantages of Endoscopic Technique versus Standard Microscopic Technique

Instrumentation

Standard Microscopic Technique

1. HD image

1. HD image

2. Excellent illumination and visualization at depths. Introducing the light source to the depth allows surgeon to have his “eye” close to the operative site

2. Poor illumination at depth

3. 30-degree angulation allows surgeon to see beyond his direct sight of vision (Figure 7)

4. 3D image

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Minimally Invasive Endoscopic Technique

3. Direct vision along line of view (Figure 7)

4. 2D image although a moving scope gives surgeon 3D depth perception. Trials of 3D endoscopes in progress Technique

Craniotomy

1. Use conventional 2-hand microsurgical approach to resect tumors 2. 2 surgeons

1. Use conventional 2-hand microsurgical approach to resect tumors

3. Active role of assistant as scope operator enhances training experience

2. Single surgeon

4. Learning curve

3. Passive role of assistant

5. Scope needs cleaning with irrigation device and antifog solution

4. Conventional technique—learning curve less steep

6. Presently using standard microsurgical instruments, although working on modifications specific for endoscopic approach

5. No cleaning of microscope lens during surgery

1. Small 2e2.5-cm craniotomy

1. Craniotomy size depends on tumor size and anatomic location

2. For temporal tumors, temporalis muscle is not elevated but incised; minimal postoperative temporal swelling; no periorbital hematoma 3. In patients with infection where bone flap is removed, given the small size of the defect, no cranioplasty is required 4. No scalp or extradural suction drain required postoperatively

6. Standard microsurgical instruments available

2. Postoperative temporal and periorbital swelling for standard myocutaneous scalp flap 3. Large infected craniotomy requires bone removal and cranioplasty at a later stage 4. Scalp or extradural drain commonly used postoperatively

Access corridor

Tumor location

1. Small access corridor diameter (1e1.5 cm) regardless of tumor size

1. Access corridor diameter depends on diameter of the tumor

2. No retractor device

2. Retractor device commonly used for subcortical lesions

1. Excellent for all subcortical intraparenchymal tumors, especially temporal fossa, frontal, and posterior fossa tumors. Also for intraventricular tumors (data not yet published). Interhemispheric approach to parafalcine and cingulate lesions

1. Presently the microscope is used for all intraparenchymal lesions. With superficial cortical tumors, the endoscope may not have an added advantage

2. Cystic lesions are excellent because cyst has created the access corridor HD, high-definition; 3D, three-dimensional; 2D, two-dimensional.

Limitations of the Technique and Study The limitations of our technique are summarized in Table 3. First, there is the risk of inadvertent widening of the corticotomy and access corridor during the surgical procedure. We have not found this to be the case because Surgicel and surgical patties line the tract well, and the corticotomy is limited by the small 2-cm craniotomy bone flap. On analysis of postoperative imaging, the mean diameter of our operative tract was 10.0 mm with a maximum of 15 mm; this is comparable to the diameter of tubular retractor systems such as the Neuroendoport reported by Kassam et al. (7), which has a diameter of 11.5 mm. During the surgical procedure,

we constantly wet the lining Surgicel and surgical patties with warm saline or change the patties for fresh ones. We have not found this practice to hamper tumor resection or contribute significantly to the overall length of the procedure. Second, the lack of a tubular retractor lining the access corridor raises the concern of increased risk of injury along the tract and the cortical surface. We have not found this to be the case, and no patient had a hematoma or contusion along the access corridor on postoperative CT scan. The peritract edema seen on postoperative FLAIR MRI scan was minimal and did not cause a new neurologic deficit in the patients.

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Third, our technique requires 2 surgeons, 1 to hold the scope and 1 to operate. The important and interactive role of the assistant has proved to be an excellent training opportunity for our residents to act initially as scope operator and to progress to undertaking most of the resection with the trainer holding the scope. In traditional microscopic techniques, the assistant’s role is more passive. However, we agree that the 2-surgeon procedure is more labor intensive, and new endoscopic holders are being developed by the industry and by our own department that may allow this procedure to be done by a single surgeon. Fourth, our surgical instrumentation and access corridor could be improved on.

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We are presently working with colleagues in medical engineering at the University of Oxford to develop instruments to facilitate minimal access surgery.

8. Keles GE, Anderson B, Berger MS: The effect of extent of resection on time to tumor progression and survival in patients with glioblastoma multiforme of the cerebral hemisphere. Surg Neurol 52: 371-379, 1999.

CONCLUSIONS

9. Kelly PJ, Goerss SJ, Kall BA: The stereotaxic retractor in computer-assisted stereotaxic microsurgery. Technical note. J Neurosurg 69:301-306, 1988.

We present our initial experience with an endoscopic, bimanual technique for resection of both superficial and deep intraparenchymal tumors. This method of resection achieves good resection rates and is safe with low complication rates. The advantages of using an endoscopic technique over a microscopic technique include the small scalp incision, minimally invasive approach without the use of a retractor, excellent illumination at the depths of the lesion, and access to subcortical lesions. The technique is versatile and suitable for intraparenchymal lesions in all lobes (supratentorial and infratentorial). Studies with further development of the instrumentation need to be undertaken to ensure universal application of this minimally invasive approach. REFERENCES 1. National Institute for Health and Clinical Excellence: Service guidance for improving outcomes for people with brain and other central nervous system tumours, www.nice.org.uk/guidance/csgbraincns. 2006. 2. Chaichana KL, Garzon-Muvdi T, Parker S, Weingart JD, Olivi A, Bennett R, Brem H, Quinones-Hinojosa A: Supratentorial glioblastoma multiforme: the role of surgical resection versus biopsy among older patients. Ann Surg Oncol 18: 239-245, 2011. 3. Greenfield JP, Cobb WS, Tsouris AJ, Schwartz TH: Stereotactic minimally invasive tubular retractor system for deep brain lesions. Neurosurgery 63 (4 Suppl 2):334-339 [discussion 339-340], 2008. 4. Jacques S, Shelden CH, McCann G, Linn S: A microstereotactic approach to small CNS lesions. Part I. Development of CT localization and 3-D reconstruction techniques. No Shinkei Geka 8: 527-537, 1980. 5. Jacques S, Shelden CH, McCann GD, Freshwater DB, Rand R: Computerized threedimensional stereotaxic removal of small central nervous system lesions in patients. J Neurosurg 53:816-820, 1980. 6. Jo KW, Shin HJ, Nam DH, Lee JI, Park K, Kim JH, Kong DS: Efficacy of endoport-guided endoscopic resection for deep-seated brain lesions. Neurosurg Rev 34:457-463, 2011. 7. Kassam AB, Engh JA, Mintz AH, Prevedello DM: Completely endoscopic resection of intraparenchymal brain tumors. J Neurosurg 110: 116-123, 2009.

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WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2014.07.034

Minimally invasive endoscopic resection of intraparenchymal brain tumors.

To report a minimally invasive, nontubular endoscopic technique to resect intraparenchymal brain tumors and assess the feasibility, safety, and surgic...
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