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The Keyhole Concept in Neurosurgery
Peer-Review Reports
The Keyhole Concept in Neurosurgery Robert Reisch1, Axel Stadie 2, Ralf A. Kockro3, Nikolai Hopf 4
Key words 䡲 Keyhole neurosurgery 䡲 Minimally invasive neurosurgery 䡲 Neuroendoscopy 䡲 Surgical planning
䡲 OBJECTIVE: Improvements in preoperative diagnostic imaging as well as in microsurgical techniques significantly advanced the development of transcranial neurosurgery, allowing the treatment of complicated diseases through smaller and more specific approaches.
Abbreviations and Acronyms 3D: Three-dimensional MCA: Middle cerebral artery MRI: Magnetic resonance imaging TEAM: Transcranial endoscope-assisted microsurgery
䡲 METHODS: In this article, authors overviewed their experience in transcranial endoscope-assisted microsurgery, using limited-sized keyhole craniotomies. Over a 10-year period, authors treated more than 3000 patients according to the transcranial endoscope-assisted microsurgery concept, advanced by the pioneer of minimally invasive neurosurgery, Axel Perneczky.
From the 1Centre for Endoscopic and Minimally Invasive Neurosurgery, Clinic Hirslanden Zurich, Zurich, Switzerland; 2 Department of Neurosurgery, University Hospital Mannheim, Mannheim, Germany; 3Department of Neurosurgery, University Hospital Zurich, Zurich, Switzerland; and 4Department of Neurosurgery, Katharinenhospital Stuttgart, Stuttgart, Germany To whom correspondence should be addressed: Robert Reisch, M.D., Ph.D. [E-mail: [email protected]]. Citation: World Neurosurg. (2013) 79, 2S:S17.e9-S17.e13. DOI: 10.1016/j.wneu.2012.02.024 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter © 2013 Published by Elsevier Inc.
INTRODUCTION Axel Perneczky, pioneer of keyhole neurosurgery conceptualized the goal of minimally invasiveneurosurgery—operatingwithaminimum of trauma while achieving maximal surgical efficiency (1, 5). However, Perneczky’s basic message was not only the limited cranial opening but the limited approach-associated surgical traumatization achieved with less exploration of the surgical site and less brain retraction. The craniotomy should be as small as possible for minimally invasive exposure but as large as necessary for achieving maximal surgical effect. In this way, limited exposure is not the primary goal but the result of the keyhole concept, with the main and most important goal being to avoid surgery-related complications (6, 9). The greatest mistake one could make when following this philosophy would be creating a far too small craniotomy with loss of essential surgical control.
䡲 RESULTS AND CONCLUSION: In all cases, meticulous preoperative planning was done for determining the site, size, and optimal placement of the craniotomy as well as the trajectory toward the surgical target. Most importantly, the surgical approach was performed either completely or at least under permanent presence of the responsible senior surgeon from the moment of patient positioning until wound closure. The minimally invasive keyhole approaches allowed safe intraoperative control and adequate dealing with intracranial lesions. Essential preconditions for keyhole surgery were 1) careful selection of cases, 2) accurate preoperative planning, 3) placement of the craniotomy tailored to the individual case, and 4) intraoperative use of transcranial endoscope-assisted microsurgery techniques. Advantages of intraoperative endoscopic visualization were increased light intensity, extended viewing angle, and clear depiction of details even in hidden parts of the surgical field.
METHODS AND RESULTS The clear benefit of keyhole neurosurgery is the minimal approach-related traumatization. By choosing the best approach to a specific lesion, the size of the craniotomy can be dramatically reduced with the need for only a small dura opening, with less brain exposure and retraction (2, 5). During a 10-year period, the authors have used keyhole approaches in more than 3000 cases. Surgical experiences showed clear advantages of minimally invasive keyhole microsurgery with improved postoperative results, including shorter hospitalization time because of reduction of the risk of complications such as bleeding or rebleeding with neurologic deterioration, epileptic seizures, leakage of cerebrospinal fluid, infection, scarification, and cosmetic impairment (5, 11, 13).
WORLD NEUROSURGERY 79 [2S]: S17.e9-S17.e13, FEBRUARY 2013
However, small craniotomies have offered some important restrictions that should be considered critically (7, 13). The major limitations of keyhole approaches are as follows. 1. limited and predefined surgical corridor 2. difficult intraoperative orientation 3. insufficiency of available microinstruments 4. decreased illumination in the deepseated field
Limited and Predefined Surgical Corridor Performing the keyhole craniotomy clearly defines the dimensions of the surgical corridor toward the target. Therefore, the craniotomy must be placed accurately and
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exactly at the right position to avoid intraoperative difficulties or disorientation. Two preconditions of a precisely placed craniotomy are important: (a) Distinguished preoperative approach planning. The smaller the craniotomy, the greater the need for precise planning and exact implementation of the plan, because it is extremely difficult to change the surgical corridor during the procedure (5). Preoperative planning includes creating a precise three-dimensional (3D) concept of the surgical target area and the trajectory leading to it. This is achieved by the acquisition and study of detailed multimodality imaging series, including high-resolution structural magnetic resonance imaging (MRI), f-MRI, diffusion tensor imaging–tractography as well as detailed arterial and venous vascular imaging. These imaging studies may then even be reconstructed on a 3D surgical planning console in order to plan the approach in stereoscopic environment, which displays surgically relevant structures in a virtual 3D space. This enables the simulation of intraoperative viewpoints and hence the exploration of the surgical site even before the actual surgery has started (3, 12, 13). (b) The personal performance of the surgery by the senior surgeon himself (3, 6, 9, 11, 12). Planning and personal performance should include positioning of the patient, skin incision, craniotomy, and surgical exposure of the target region. This permanent presence of the senior surgeon himself stands in contrast to the common practice of at least the initial approach being performed by a resident, who is then joined only later on by his senior colleague. Our experience showed that performing a precise patientspecifically tailored and minimally invasive approach requires the experience of a senior surgeon from the beginning on— especially when training a more junior neurosurgeon in these techniques. In this way, the principle of the individually tailored and “self-made” minimally invasive keyhole neurosurgery is in direct disparity to a standard surgical intervention via extended approaches. Difficult Intraoperative Orientation The second drawback of keyhole procedures is the difficult intraoperative orientation (13). The intraoperative use of navigation systems and real-time imaging, for example, ultrasound and intraoperative
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THE KEYHOLE CONCEPT
Figure 1. Transcranial endoscope-assisted microneurosurgery (TEAM), performed at the Centre for Endoscopic and Minimally Invasive Neurosurgery, Clinic Hirslanden, Zurich. Note that endoscopes with angled shafts are preferred for the TEAM technique, as the camera attached to the eyepiece does not interfere with the visual field of the microscope and does not hinder surgical manipulation. In the background intraoperative computed tomography appears, used for real-time image-guided surgery.
computed tomography and MRI may be helpful if the limited cranial opening leads to a structurally complex and hard-to-understand situation (Figure 1). Nevertheless, these technical tools can hardly replace the comprehensive 3D information gained by a detailed planning process nor can they substitute profound anatomic knowledge of the target region.
Insufficiency of Available Microinstruments The narrow viewing angle and almost coaxial control of dissection as a result of the small and individually tailored approach may cause an additional problem. In our experience, if the craniotomy is smaller than 1.5 cm, conventional microinstruments are difficult to use because they may strike against the craniotomy (4, 5, 8). For this reason, the development and intraoperative use of novel microinstruments, for example, scissors, grasping, and coagulating forceps, clip appliers, etc. has been an important step in advancing keyhole surgery. In particular, slim, tube-shaft designed tools allow unhindered manipulation even through limited keyhole craniotomies (Figure 2).
Decreased Illumination in the Deep-Seated Field The fourth and probably central difficulty of keyhole approaches is the loss of intraoper-
Figure 2. Conventional clip applier (left) and special tube-shaft instrument (right) designed for minimally invasive keyhole vascular surgery (Aesculap AG, Tuttlingen, Germany). When operating through keyhole craniotomies, the use of tube-shaft instruments is often obligatory for safe manipulation in the narrow field.
ative light and sight because the limited craniotomy causes significant reduction in intraoperative optical control. However, the neurosurgeon must be able to recognize both normal anatomic structures to avoid damaging them and abnormal structures to remove them. For the purpose of bringing light into the surgical field and controlling manipulation in the depth of the operating field, surgical microscopes can be effectively supported by the optical properties of modern endoscopes (2, 5, 7, 11). Advantages of endoscopes are 1) increased light intensity, 2) extended viewing angle, and 3) clear depiction of details in close-up. The endoscope is especially suited for obtaining a detailed view of structures in the shadow of the microscope’s light beam. Thus, in situations during microsurgical dissection where additional visual information of the target area is desired or when avoidance of retraction of superficial structures is recommended, an endoscope may be introduced into the surgical site. Both devices complement each other because of their different optical properties; hence, in this publication, we have termed the TEAMwork of the microscope and the endoscope as Transcranial Endoscope-Assisted Microneurosurgery (Figure 1). For the TEAM technique, rigid lens scopes are recommended because only instruments with rigid shafts can be controlled precisely and because, at least at present, only lens scopes offer acceptable image quality. Endoscopes with angled shafts are preferred as the camera attached to the eyepiece does not interfere with the
WORLD NEUROSURGERY, DOI:10.1016/j.wneu.2012.02.024
PEER-REVIEW REPORTS ROBERT REISCH ET AL.
visual field of the microscope and does not hinder surgical manipulation. Different degrees of angulation of the front lens offer viewing angles of 0, 30, 45, and 70 degrees. Recently, the intraoperative use of fullhigh-definition (HD) image quality has offered a new area in endoscopic neurosurgery with an increased range of indications in minimally invasive TEAM neurosurgery. The image quality of the full-high-definition system is markedly superior to that of a standard oneor three-chip camera unit, providing a five times higher optical resolution. The brilliant image quality offers exact and clear depiction of the smallest details within the surgical field, resulting in improved surgical orientation and safety (6, 11).
ILLUSTRATIVE CASE History Mother and sister of this 55-year-old female patient suffered from severe aneurysmal subarachnoid hemorrhage, and a brother died suddenly after fatal bleeding. For neurologic and radiologic clarification, MRI with MR angiography was performed. Three-dimensional time-of-flight angiography showed two unruptured aneurysms of the right middle cerebral artery (MCA): a proximal one at the early temporal branch and a distal one at the MCA bifurcation (Figure 3A). Because of the disastrous familiar history and the patient’s understandable anxiety, indication for treatment was given.
THE KEYHOLE CONCEPT
Planning Procedures After interdisciplinary discussion concerning the treatment modality, the surgical solution was chosen; arguments favoring surgery were the small size of the proximal, and unfavorable, dome neck aspect ratio of the distal aneurysm. This decision was maintained by the patient’s severe contrast medium allergy; therefore, surgical planning was done without performing conventional cerebral angiography (digital subtraction angiography) by thorough evaluation of the MRI studies. Two possible approaches were compared. The pterional approach allowed early access of the Sylvian fissure; however, the view to the early temporal branch was significantly obstructed by the larger distal aneurysm (Figure 3B). In contrast, the subfrontal approach through supraorbital skin incision promised sufficient visualization of both aneurysms with safe proximal control of the MCA main trunk (Figure 3C). In addition, the supraorbital subfrontal direction avoided manipulation of the temporal lobe with protection of the Sylvian veins. Transcranial Endoscope-Assisted Microsurgery With the patient in a supine position, a 3-cm skin incision was made within the eyebrow and a right supraorbital craniotomy was performed with an outer diameter of 1.5 ⫻ 2 cm. After removal of the bone flap, the frontal inner edge of the craniotomy and osseous extensions of the orbital roof were removed us-
Figure 3. Three-dimensional time-of-flight magnetic resonance angiography, showing unruptured aneurysms at the early temporal branch and at the bifurcation of the right middle cerebral artery (MCA) (A). After interdisciplinary discussion concerning the treatment modality, the surgical solution was chosen due to the small size of the proximal, and unfavorable dome neck aspect ratio of the distal aneurysm. Note that from the
ing high-speed drill. The dura was opened in a semilunar shaped fashion, the frontal lobe was gently mobilized with cotton pads, and the suprasellar cisterns were exposed (9, 10). After removal of cerebrospinal fluid, the carotid bifurcation was approached, allowing early proximal control. Now, the Sylvian fissure was partially opened and both aneurysms approached. According to the preoperative diagnostics, we found the smaller proximal aneurysm at the early temporal branch; the distal aneurysm at the MCA bifurcation showed a wide neck. The subfrontal supraorbital approach offered optimal access to both aneurysms (Figure 4A). The endoscopic image allowed precise investigation of the aneurysm topography, including the neck region and eloquent perforators in the vicinity of the aneurysms (Figures 4B and C). At first, the deep-seated proximal aneurysm was clipped; however, endoscopic investigation showed residual neck (Figure 4D). Therefore, the clip position was revised. After endoscopically verified complete closure (Figure 4E), the distal aneurysm was clipped under endoscopic control (Figures 4E and F). Both aneurysms were now opened without observing arterial bleeding; micro-Doppler showed normal flow within the MCA vessels. According to severe contrast medium allergy, no indocyanine green angiography was used. An important remark: during surgery, no cerebral retractor was in site, only sterile cotton pads were used for gentle dissection.
pterional view (B), the early temporal branch is significantly obstructed by the larger distal aneurysm. In contrast, the subfrontal supraorbital access (C) offers sufficient visualization of both aneurysms with safe proximal control of the MCA main trunk. (Courtesy Zsolt Kulcsár, Daniel Rüfenacht, Isabel Wanke, and Stephan Wetzel, Neuroradiology Hirslanden, Zurich, Germany.)
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THE KEYHOLE CONCEPT
Figure 4. Intraoperative endoscopic photographs demonstrating clipping procedure. Both aneurysms could be optimal visualized through the subfrontal supraorbital keyhole, even without using brain retraction; note effective dissection with sterile cottonoid pads (A). The proximal aneurysm of the early temporal branch was first approached (B); thereafter, the distal one. Note small perforators near to the neck of the distal aneurysm and the temporal main trunk of the middle cerebral artery (MCA), observing
Postoperative Course The patient made an uneventful recovery, postoperative examination revealed no
without injury of the temporal lobe (C). At first, the deep proximal aneurysm was closed; however, residual neck appeared in close-up position of the endoscope (D), making clip replacement necessary (E). Using the TEAM technique, the distal wide distal aneurysm could also be successfully closed through the limited keyhole craniotomy (E). Note the main temporal trunk of the MCA in close-up, without clip-related narrowing (F).
neurologic symptoms; computed tomographic scan showed no intracranial complication and confirmed optimal place-
ment of the small bone flap (Figure 5). According to the endoscopically verified closure and contrast medium allergy, no postoperative digital subtraction angiography was performed. The patient could return to her previous employment as medical doctor 2 weeks after surgery, the cosmetic result was excellent.
DISCUSSION AND CONCLUSION
Figure 5. Postoperative computed tomographic (CT) scan in axial (A) and sagittal (B) plane, demonstrating site and size of the supraorbital keyhole craniotomy. Note placement of the distal aneurysm clip on the sagittal imaging.
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Using modern diagnostic tools, the specific anatomy and pathology of the individual patient can be precisely visualized. This allows us to establish a detailed surgical plan and to determine an exact anatomic pathway for optimal surgical access. Based on the well-defined access, the surgical dissection can be performed while creating a minimally traumatizing cranial opening and while avoiding exploratory dissection (5). In fact, the position and course of the surgical approach plays the most important role
WORLD NEUROSURGERY, DOI:10.1016/j.wneu.2012.02.024
PEER-REVIEW REPORTS ROBERT REISCH ET AL.
in minimally invasive keyhole neurosurgery, and it is complemented by the use of carefully chosen instruments and the recognition of small technical details—to avoid intraoperative confusion or space constrains during dissection (3, 12). Therefore, the planning as well as the performance of the approach is the task of the modern keyhole neurosurgeon (5, 11). Of course, operating “skin to skin” is time consuming for the senior surgeon and prevents quick switching from one operating theater into the other. However, we strongly believe that this personal performance of the TEAM technique by the senior surgeon, bearing the responsibility to avoid approach-related trauma and achieve maximally efficient surgery, is key to successful keyhole surgery, thus optimizing the surgical outcome.
THE KEYHOLE CONCEPT
REFERENCES 1. Hopf NJ, Reisch R: Axel Perneczky, 1.11.194524.1.2009. Minim Invasive Neurosurg 52:1-4, 2009. 2. Hopf NJ, Stadie A, Reisch R: Surgical management of bilateral middle cerebral artery aneurysms via a unilateral supraorbital key-hole craniotomy. Minim Invasive Neurosurg 52:126-131, 2009. 3. Kockro RA, Stadie A, Schwandt E, Reisch R, Charalampaki C, Ng I, Yeo TT, Hwang P, Serra L, Perneczky A: A collaborative virtual reality environment for neurosurgical planning and training. Neurosurgery 61:379-391, 2007. 4. Perneczky A, Fries G: Use of a new aneurysm clip with an inverted-spring mechanism to facilitate visual control during clip application. J Neurosurg 82:898-899, 1995. 5. Perneczky A, Reisch R: Multiple aneurysms treated via frontal interhemispheric approach. In: Kobayashi S, ed. Neurosurgery of Complex Vascular Lesions and Tumors. Stuttgart: Thieme Verlag; 2005:7-11. 6. Perneczky A, Reisch R: Key hole approaches in neurosurgery. Volume I. Concept and surgical technique. Wien: Springer Verlag; 2008.
ACKNOWLEDGMENT Endoscope-assisted keyhole neurosurgery was advanced by our teacher and mentor Axel Perneczky. He passed away suddenly on January 24, 2009, at the age of 63 years. This paper is addressed to him in deep respect.
7. Reisch R: Endoscopic transsphenoidal surgery of the central skull base. Center Valley, PA: Aesculap; 2008.
9. Reisch R, Perneczky A: Ten-year experience with the supraorbital subfrontal approach through an eyebrow skin incision. Neurosurgery 57:242-255, 2005. 10. Reisch R, Perneczky A, Filippi R: Surgical technique of the supraorbital key-hole craniotomy. Surg Neurol 59:223-227, 2003. 11. Reisch R, Stadie A, Kockro R, Gawish I, Schwandt E, Hopf N: The minimally invasive supraorbital subfrontal key-hole approach for surgical treatment of temporomesial lesions of the dominant hemisphere. Minim Invasive Neurosurg 52:163-169, 2009. 12. Stadie AT, Kockro RA, Reisch R, Tropine A, Boor S, Stoeter P, Perneczky A: Virtual reality system for planning minimally invasive neurosurgery. Technical note. J Neurosurg 108:382-394, 2008. 13. Stadie AT, Reisch R, Kockro RA, Fischer G, Schwandt E, Boor S, Stoeter P: Minimally invasive cerebral cavernoma surgery using keyhole approaches—solutions for technique-related limitations. Minim Invasive Neurosurg 52:9-16, 2009.
Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. received 16 August 2011; accepted 03 February 2012 Citation: World Neurosurg. (2013) 79, 2S:S17.e9-S17.e13. DOI: 10.1016/j.wneu.2012.02.024 Journal homepage: www.WORLDNEUROSURGERY.org
8. Reisch R, Perneczky A: The supraorbital craniotomy for frontobasal meningiomas. In: Kobayashi, S, ed. Neurosurgery of Complex Vascular Lesions and Tumors. Stuttgart: Thieme Verlag; 2005:201-206.
WORLD NEUROSURGERY 79 [2S]: S17.e9-S17.e13, FEBRUARY 2013
Available online: www.sciencedirect.com 1878-8750/$ - see front matter © 2013 Published by Elsevier Inc.
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The Keyhole Concept in Neurosurgery Robert Reisch1, Axel Stadie 2, Ralf A. Kockro3, Nikolai Hopf 4
Key words 䡲 Keyhole neurosurgery 䡲 Minimally invasive neurosurgery 䡲 Neuroendoscopy 䡲 Surgical planning
䡲 OBJECTIVE: Improvements in preoperative diagnostic imaging as well as in microsurgical techniques significantly advanced the development of transcranial neurosurgery, allowing the treatment of complicated diseases through smaller and more specific approaches.
Abbreviations and Acronyms 3D: Three-dimensional MCA: Middle cerebral artery MRI: Magnetic resonance imaging TEAM: Transcranial endoscope-assisted microsurgery
䡲 METHODS: In this article, authors overviewed their experience in transcranial endoscope-assisted microsurgery, using limited-sized keyhole craniotomies. Over a 10-year period, authors treated more than 3000 patients according to the transcranial endoscope-assisted microsurgery concept, advanced by the pioneer of minimally invasive neurosurgery, Axel Perneczky.
From the 1Centre for Endoscopic and Minimally Invasive Neurosurgery, Clinic Hirslanden Zurich, Zurich, Switzerland; 2 Department of Neurosurgery, University Hospital Mannheim, Mannheim, Germany; 3Department of Neurosurgery, University Hospital Zurich, Zurich, Switzerland; and 4Department of Neurosurgery, Katharinenhospital Stuttgart, Stuttgart, Germany To whom correspondence should be addressed: Robert Reisch, M.D., Ph.D. [E-mail: [email protected]]. Citation: World Neurosurg. (2013) 79, 2S:S17.e9-S17.e13. DOI: 10.1016/j.wneu.2012.02.024 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter © 2013 Published by Elsevier Inc.
INTRODUCTION Axel Perneczky, pioneer of keyhole neurosurgery conceptualized the goal of minimally invasiveneurosurgery—operatingwithaminimum of trauma while achieving maximal surgical efficiency (1, 5). However, Perneczky’s basic message was not only the limited cranial opening but the limited approach-associated surgical traumatization achieved with less exploration of the surgical site and less brain retraction. The craniotomy should be as small as possible for minimally invasive exposure but as large as necessary for achieving maximal surgical effect. In this way, limited exposure is not the primary goal but the result of the keyhole concept, with the main and most important goal being to avoid surgery-related complications (6, 9). The greatest mistake one could make when following this philosophy would be creating a far too small craniotomy with loss of essential surgical control.
䡲 RESULTS AND CONCLUSION: In all cases, meticulous preoperative planning was done for determining the site, size, and optimal placement of the craniotomy as well as the trajectory toward the surgical target. Most importantly, the surgical approach was performed either completely or at least under permanent presence of the responsible senior surgeon from the moment of patient positioning until wound closure. The minimally invasive keyhole approaches allowed safe intraoperative control and adequate dealing with intracranial lesions. Essential preconditions for keyhole surgery were 1) careful selection of cases, 2) accurate preoperative planning, 3) placement of the craniotomy tailored to the individual case, and 4) intraoperative use of transcranial endoscope-assisted microsurgery techniques. Advantages of intraoperative endoscopic visualization were increased light intensity, extended viewing angle, and clear depiction of details even in hidden parts of the surgical field.
METHODS AND RESULTS The clear benefit of keyhole neurosurgery is the minimal approach-related traumatization. By choosing the best approach to a specific lesion, the size of the craniotomy can be dramatically reduced with the need for only a small dura opening, with less brain exposure and retraction (2, 5). During a 10-year period, the authors have used keyhole approaches in more than 3000 cases. Surgical experiences showed clear advantages of minimally invasive keyhole microsurgery with improved postoperative results, including shorter hospitalization time because of reduction of the risk of complications such as bleeding or rebleeding with neurologic deterioration, epileptic seizures, leakage of cerebrospinal fluid, infection, scarification, and cosmetic impairment (5, 11, 13).
WORLD NEUROSURGERY 79 [2S]: S17.e9-S17.e13, FEBRUARY 2013
However, small craniotomies have offered some important restrictions that should be considered critically (7, 13). The major limitations of keyhole approaches are as follows. 1. limited and predefined surgical corridor 2. difficult intraoperative orientation 3. insufficiency of available microinstruments 4. decreased illumination in the deepseated field
Limited and Predefined Surgical Corridor Performing the keyhole craniotomy clearly defines the dimensions of the surgical corridor toward the target. Therefore, the craniotomy must be placed accurately and
www.WORLDNEUROSURGERY.org
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PEER-REVIEW REPORTS ROBERT REISCH ET AL.
exactly at the right position to avoid intraoperative difficulties or disorientation. Two preconditions of a precisely placed craniotomy are important: (a) Distinguished preoperative approach planning. The smaller the craniotomy, the greater the need for precise planning and exact implementation of the plan, because it is extremely difficult to change the surgical corridor during the procedure (5). Preoperative planning includes creating a precise three-dimensional (3D) concept of the surgical target area and the trajectory leading to it. This is achieved by the acquisition and study of detailed multimodality imaging series, including high-resolution structural magnetic resonance imaging (MRI), f-MRI, diffusion tensor imaging–tractography as well as detailed arterial and venous vascular imaging. These imaging studies may then even be reconstructed on a 3D surgical planning console in order to plan the approach in stereoscopic environment, which displays surgically relevant structures in a virtual 3D space. This enables the simulation of intraoperative viewpoints and hence the exploration of the surgical site even before the actual surgery has started (3, 12, 13). (b) The personal performance of the surgery by the senior surgeon himself (3, 6, 9, 11, 12). Planning and personal performance should include positioning of the patient, skin incision, craniotomy, and surgical exposure of the target region. This permanent presence of the senior surgeon himself stands in contrast to the common practice of at least the initial approach being performed by a resident, who is then joined only later on by his senior colleague. Our experience showed that performing a precise patientspecifically tailored and minimally invasive approach requires the experience of a senior surgeon from the beginning on— especially when training a more junior neurosurgeon in these techniques. In this way, the principle of the individually tailored and “self-made” minimally invasive keyhole neurosurgery is in direct disparity to a standard surgical intervention via extended approaches. Difficult Intraoperative Orientation The second drawback of keyhole procedures is the difficult intraoperative orientation (13). The intraoperative use of navigation systems and real-time imaging, for example, ultrasound and intraoperative
S17.e10
www.SCIENCEDIRECT.com
THE KEYHOLE CONCEPT
Figure 1. Transcranial endoscope-assisted microneurosurgery (TEAM), performed at the Centre for Endoscopic and Minimally Invasive Neurosurgery, Clinic Hirslanden, Zurich. Note that endoscopes with angled shafts are preferred for the TEAM technique, as the camera attached to the eyepiece does not interfere with the visual field of the microscope and does not hinder surgical manipulation. In the background intraoperative computed tomography appears, used for real-time image-guided surgery.
computed tomography and MRI may be helpful if the limited cranial opening leads to a structurally complex and hard-to-understand situation (Figure 1). Nevertheless, these technical tools can hardly replace the comprehensive 3D information gained by a detailed planning process nor can they substitute profound anatomic knowledge of the target region.
Insufficiency of Available Microinstruments The narrow viewing angle and almost coaxial control of dissection as a result of the small and individually tailored approach may cause an additional problem. In our experience, if the craniotomy is smaller than 1.5 cm, conventional microinstruments are difficult to use because they may strike against the craniotomy (4, 5, 8). For this reason, the development and intraoperative use of novel microinstruments, for example, scissors, grasping, and coagulating forceps, clip appliers, etc. has been an important step in advancing keyhole surgery. In particular, slim, tube-shaft designed tools allow unhindered manipulation even through limited keyhole craniotomies (Figure 2).
Decreased Illumination in the Deep-Seated Field The fourth and probably central difficulty of keyhole approaches is the loss of intraoper-
Figure 2. Conventional clip applier (left) and special tube-shaft instrument (right) designed for minimally invasive keyhole vascular surgery (Aesculap AG, Tuttlingen, Germany). When operating through keyhole craniotomies, the use of tube-shaft instruments is often obligatory for safe manipulation in the narrow field.
ative light and sight because the limited craniotomy causes significant reduction in intraoperative optical control. However, the neurosurgeon must be able to recognize both normal anatomic structures to avoid damaging them and abnormal structures to remove them. For the purpose of bringing light into the surgical field and controlling manipulation in the depth of the operating field, surgical microscopes can be effectively supported by the optical properties of modern endoscopes (2, 5, 7, 11). Advantages of endoscopes are 1) increased light intensity, 2) extended viewing angle, and 3) clear depiction of details in close-up. The endoscope is especially suited for obtaining a detailed view of structures in the shadow of the microscope’s light beam. Thus, in situations during microsurgical dissection where additional visual information of the target area is desired or when avoidance of retraction of superficial structures is recommended, an endoscope may be introduced into the surgical site. Both devices complement each other because of their different optical properties; hence, in this publication, we have termed the TEAMwork of the microscope and the endoscope as Transcranial Endoscope-Assisted Microneurosurgery (Figure 1). For the TEAM technique, rigid lens scopes are recommended because only instruments with rigid shafts can be controlled precisely and because, at least at present, only lens scopes offer acceptable image quality. Endoscopes with angled shafts are preferred as the camera attached to the eyepiece does not interfere with the
WORLD NEUROSURGERY, DOI:10.1016/j.wneu.2012.02.024
PEER-REVIEW REPORTS ROBERT REISCH ET AL.
visual field of the microscope and does not hinder surgical manipulation. Different degrees of angulation of the front lens offer viewing angles of 0, 30, 45, and 70 degrees. Recently, the intraoperative use of fullhigh-definition (HD) image quality has offered a new area in endoscopic neurosurgery with an increased range of indications in minimally invasive TEAM neurosurgery. The image quality of the full-high-definition system is markedly superior to that of a standard oneor three-chip camera unit, providing a five times higher optical resolution. The brilliant image quality offers exact and clear depiction of the smallest details within the surgical field, resulting in improved surgical orientation and safety (6, 11).
ILLUSTRATIVE CASE History Mother and sister of this 55-year-old female patient suffered from severe aneurysmal subarachnoid hemorrhage, and a brother died suddenly after fatal bleeding. For neurologic and radiologic clarification, MRI with MR angiography was performed. Three-dimensional time-of-flight angiography showed two unruptured aneurysms of the right middle cerebral artery (MCA): a proximal one at the early temporal branch and a distal one at the MCA bifurcation (Figure 3A). Because of the disastrous familiar history and the patient’s understandable anxiety, indication for treatment was given.
THE KEYHOLE CONCEPT
Planning Procedures After interdisciplinary discussion concerning the treatment modality, the surgical solution was chosen; arguments favoring surgery were the small size of the proximal, and unfavorable, dome neck aspect ratio of the distal aneurysm. This decision was maintained by the patient’s severe contrast medium allergy; therefore, surgical planning was done without performing conventional cerebral angiography (digital subtraction angiography) by thorough evaluation of the MRI studies. Two possible approaches were compared. The pterional approach allowed early access of the Sylvian fissure; however, the view to the early temporal branch was significantly obstructed by the larger distal aneurysm (Figure 3B). In contrast, the subfrontal approach through supraorbital skin incision promised sufficient visualization of both aneurysms with safe proximal control of the MCA main trunk (Figure 3C). In addition, the supraorbital subfrontal direction avoided manipulation of the temporal lobe with protection of the Sylvian veins. Transcranial Endoscope-Assisted Microsurgery With the patient in a supine position, a 3-cm skin incision was made within the eyebrow and a right supraorbital craniotomy was performed with an outer diameter of 1.5 ⫻ 2 cm. After removal of the bone flap, the frontal inner edge of the craniotomy and osseous extensions of the orbital roof were removed us-
Figure 3. Three-dimensional time-of-flight magnetic resonance angiography, showing unruptured aneurysms at the early temporal branch and at the bifurcation of the right middle cerebral artery (MCA) (A). After interdisciplinary discussion concerning the treatment modality, the surgical solution was chosen due to the small size of the proximal, and unfavorable dome neck aspect ratio of the distal aneurysm. Note that from the
ing high-speed drill. The dura was opened in a semilunar shaped fashion, the frontal lobe was gently mobilized with cotton pads, and the suprasellar cisterns were exposed (9, 10). After removal of cerebrospinal fluid, the carotid bifurcation was approached, allowing early proximal control. Now, the Sylvian fissure was partially opened and both aneurysms approached. According to the preoperative diagnostics, we found the smaller proximal aneurysm at the early temporal branch; the distal aneurysm at the MCA bifurcation showed a wide neck. The subfrontal supraorbital approach offered optimal access to both aneurysms (Figure 4A). The endoscopic image allowed precise investigation of the aneurysm topography, including the neck region and eloquent perforators in the vicinity of the aneurysms (Figures 4B and C). At first, the deep-seated proximal aneurysm was clipped; however, endoscopic investigation showed residual neck (Figure 4D). Therefore, the clip position was revised. After endoscopically verified complete closure (Figure 4E), the distal aneurysm was clipped under endoscopic control (Figures 4E and F). Both aneurysms were now opened without observing arterial bleeding; micro-Doppler showed normal flow within the MCA vessels. According to severe contrast medium allergy, no indocyanine green angiography was used. An important remark: during surgery, no cerebral retractor was in site, only sterile cotton pads were used for gentle dissection.
pterional view (B), the early temporal branch is significantly obstructed by the larger distal aneurysm. In contrast, the subfrontal supraorbital access (C) offers sufficient visualization of both aneurysms with safe proximal control of the MCA main trunk. (Courtesy Zsolt Kulcsár, Daniel Rüfenacht, Isabel Wanke, and Stephan Wetzel, Neuroradiology Hirslanden, Zurich, Germany.)
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THE KEYHOLE CONCEPT
Figure 4. Intraoperative endoscopic photographs demonstrating clipping procedure. Both aneurysms could be optimal visualized through the subfrontal supraorbital keyhole, even without using brain retraction; note effective dissection with sterile cottonoid pads (A). The proximal aneurysm of the early temporal branch was first approached (B); thereafter, the distal one. Note small perforators near to the neck of the distal aneurysm and the temporal main trunk of the middle cerebral artery (MCA), observing
Postoperative Course The patient made an uneventful recovery, postoperative examination revealed no
without injury of the temporal lobe (C). At first, the deep proximal aneurysm was closed; however, residual neck appeared in close-up position of the endoscope (D), making clip replacement necessary (E). Using the TEAM technique, the distal wide distal aneurysm could also be successfully closed through the limited keyhole craniotomy (E). Note the main temporal trunk of the MCA in close-up, without clip-related narrowing (F).
neurologic symptoms; computed tomographic scan showed no intracranial complication and confirmed optimal place-
ment of the small bone flap (Figure 5). According to the endoscopically verified closure and contrast medium allergy, no postoperative digital subtraction angiography was performed. The patient could return to her previous employment as medical doctor 2 weeks after surgery, the cosmetic result was excellent.
DISCUSSION AND CONCLUSION
Figure 5. Postoperative computed tomographic (CT) scan in axial (A) and sagittal (B) plane, demonstrating site and size of the supraorbital keyhole craniotomy. Note placement of the distal aneurysm clip on the sagittal imaging.
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Using modern diagnostic tools, the specific anatomy and pathology of the individual patient can be precisely visualized. This allows us to establish a detailed surgical plan and to determine an exact anatomic pathway for optimal surgical access. Based on the well-defined access, the surgical dissection can be performed while creating a minimally traumatizing cranial opening and while avoiding exploratory dissection (5). In fact, the position and course of the surgical approach plays the most important role
WORLD NEUROSURGERY, DOI:10.1016/j.wneu.2012.02.024
PEER-REVIEW REPORTS ROBERT REISCH ET AL.
in minimally invasive keyhole neurosurgery, and it is complemented by the use of carefully chosen instruments and the recognition of small technical details—to avoid intraoperative confusion or space constrains during dissection (3, 12). Therefore, the planning as well as the performance of the approach is the task of the modern keyhole neurosurgeon (5, 11). Of course, operating “skin to skin” is time consuming for the senior surgeon and prevents quick switching from one operating theater into the other. However, we strongly believe that this personal performance of the TEAM technique by the senior surgeon, bearing the responsibility to avoid approach-related trauma and achieve maximally efficient surgery, is key to successful keyhole surgery, thus optimizing the surgical outcome.
THE KEYHOLE CONCEPT
REFERENCES 1. Hopf NJ, Reisch R: Axel Perneczky, 1.11.194524.1.2009. Minim Invasive Neurosurg 52:1-4, 2009. 2. Hopf NJ, Stadie A, Reisch R: Surgical management of bilateral middle cerebral artery aneurysms via a unilateral supraorbital key-hole craniotomy. Minim Invasive Neurosurg 52:126-131, 2009. 3. Kockro RA, Stadie A, Schwandt E, Reisch R, Charalampaki C, Ng I, Yeo TT, Hwang P, Serra L, Perneczky A: A collaborative virtual reality environment for neurosurgical planning and training. Neurosurgery 61:379-391, 2007. 4. Perneczky A, Fries G: Use of a new aneurysm clip with an inverted-spring mechanism to facilitate visual control during clip application. J Neurosurg 82:898-899, 1995. 5. Perneczky A, Reisch R: Multiple aneurysms treated via frontal interhemispheric approach. In: Kobayashi S, ed. Neurosurgery of Complex Vascular Lesions and Tumors. Stuttgart: Thieme Verlag; 2005:7-11. 6. Perneczky A, Reisch R: Key hole approaches in neurosurgery. Volume I. Concept and surgical technique. Wien: Springer Verlag; 2008.
ACKNOWLEDGMENT Endoscope-assisted keyhole neurosurgery was advanced by our teacher and mentor Axel Perneczky. He passed away suddenly on January 24, 2009, at the age of 63 years. This paper is addressed to him in deep respect.
7. Reisch R: Endoscopic transsphenoidal surgery of the central skull base. Center Valley, PA: Aesculap; 2008.
9. Reisch R, Perneczky A: Ten-year experience with the supraorbital subfrontal approach through an eyebrow skin incision. Neurosurgery 57:242-255, 2005. 10. Reisch R, Perneczky A, Filippi R: Surgical technique of the supraorbital key-hole craniotomy. Surg Neurol 59:223-227, 2003. 11. Reisch R, Stadie A, Kockro R, Gawish I, Schwandt E, Hopf N: The minimally invasive supraorbital subfrontal key-hole approach for surgical treatment of temporomesial lesions of the dominant hemisphere. Minim Invasive Neurosurg 52:163-169, 2009. 12. Stadie AT, Kockro RA, Reisch R, Tropine A, Boor S, Stoeter P, Perneczky A: Virtual reality system for planning minimally invasive neurosurgery. Technical note. J Neurosurg 108:382-394, 2008. 13. Stadie AT, Reisch R, Kockro RA, Fischer G, Schwandt E, Boor S, Stoeter P: Minimally invasive cerebral cavernoma surgery using keyhole approaches—solutions for technique-related limitations. Minim Invasive Neurosurg 52:9-16, 2009.
Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. received 16 August 2011; accepted 03 February 2012 Citation: World Neurosurg. (2013) 79, 2S:S17.e9-S17.e13. DOI: 10.1016/j.wneu.2012.02.024 Journal homepage: www.WORLDNEUROSURGERY.org
8. Reisch R, Perneczky A: The supraorbital craniotomy for frontobasal meningiomas. In: Kobayashi, S, ed. Neurosurgery of Complex Vascular Lesions and Tumors. Stuttgart: Thieme Verlag; 2005:201-206.
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