- Email: [email protected]
Minimally Invasive, but Not at the Cost of Maximally Effective, in the Surgical Removal of Brainstem Cavernous Malformations
Perspectives Commentary on: Surgical Resection of Cavernous Malformations of the Brainstem: Evolution of a Minimally Invasive Technique by Mai et al. pp. 691-703.
Robert F. Spetzler, M.D. Director, Barrow Neurological Institute (BNI) J.N. Harber Chair of Neurological Surgery at BNI Chairman and President, Barrow Neurosurgical Associates, Professor of Surgery Section of Neurosurgery, University of Arizona College of Medicine
Minimally Invasive, but Not at the Cost of Maximally Effective, in the Surgical Removal of Brainstem Cavernous Malformations Adib A. Abla and Robert F. Spetzler
I
n the current issue of WORLD NEUROSURGERY, Mai et al. review a series of 22 patients with 26 brainstem cavernous malformations. At an average of 26.6 months of follow-up, 14 patients had a modified Rankin score (mRS) of 0 or 1, and an additional 3 patients had a mRS of 2. A final mRS of 3 or 4 was achieved in 6 patients. Two patients had residual lesions but elected not to undergo additional surgery. The surgical approaches involved suboccipital craniotomy (n ⫽ 6), orbitozygomatic craniotomy (n ⫽ 5), transpetrosal approach (n ⫽ 4), combined transtemporal/transpetrosal (n ⫽ 2), lateral supracerebellar approach (n ⫽ 2), occipital transtentorial (n ⫽ 1), transmaxillary/transclival (n ⫽ 1), retrosigmoid (n ⫽ 1), presigmoid/ transsigmoid (n ⫽ 1), subtemporal/infratentorial (n ⫽ 1), and supracerebellar/transtentorial (n ⫽ 1). The article is concise and well-written with many salient points. The article presents various case examples in the text with excellent figures that demonstrate the trajectory from the craniotomy to the brainstem lesion. The authors obtained excellent clinical and radiographic outcomes and make valid arguments based on these 22 patients. Their surgical indications, surgical technique, and preservation of developmental venous anomalies are consistent with our institutional approach. It is very much on par with our institutional experience (1) that patients after these surgeries often experience new deficits, such as numbness, ataxia, diplopia, or dysmetria, which are frequently mild and transient. However, such small setbacks are acceptable when considering the damage caused by repeated hemorrhage and mass effect in many untreated patients who are often devastated by the bleeds. Overall, the authors should be congratulated on this experience. In the resection of brainstem cavernous malformations, there is a tipping point that involves the balance between obtaining a
Key words 䡲 Brainstem 䡲 Cavernoma 䡲 Cavernous malformation 䡲 Skull base
638
Abbreviations and Acronyms CSF: Cerebrospinal fluid MRI: Magnetic resonance imaging mRS: Modified Rankin score SCIT: Supracerebellar infratentorial
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gross total resection and keeping a patient’s neurologic function as close to baseline as possible. The authors’ conclusion is that they would favor a less than total resection, while advocating for a minimally invasive approach to the lesion to maintain function. We are very much in agreement, but there are important caveats and discussion points which we would like to elaborate on here. When defining what is minimally invasive, it can apply to many aspects of the case. It can refer to the size of the skin incision; to the size of the craniotomy; to the amount of dura mater that is opened; or to the pial opening into the brain, or entry site into the brainstem. There is no well-accepted definition of what makes a surgical procedure minimally invasive. In some cases, the procedure may involve an endoscope or a laser, and many neurosurgeons are probably familiar with advertising that touts the benefits of “laser” or “endoscopic” surgery. Also, as it relates to brainstem cavernous malformations, the term “minimally invasive” does not necessarily refer to keyhole endoscopic microneurosurgery at the present time. “Minimally invasive” is a relative term as it relates to skull base surgery and the often extensive dissection involved. A transpetrosal/transtemporal approach may not be considered minimally invasive to some neurosurgeons. The authors’ definition of “minimally invasive” in brainstem cavernous malformation surgery involves making a small opening in the brainstem, which, as we have described previously, is often best suited parallel to the traversing nerve fibers (1), and centrally debulking the lesion first (Figure 10 in Mai et al.). We agree with Mai et al. that a less aggressive stance for residuals that have not regrown or rebled is appropriate. The nuances of the first operation that made it difficult to obtain a complete resection are unlikely to change the second time,
Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona, USA To whom correspondence should be addressed: Robert F. Spetzler, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2013) 79, 5/6:638-640. http://dx.doi.org/10.1016/j.wneu.2013.01.053
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2013.01.053
PERSPECTIVES
unless there is expansion and new mass effect attributable to further bleeding. The one option when it is unclear if there is any residual cavernous malformation is to obtain an intraoperative or immediate postoperative magnetic resonance imaging (MRI) scan and bring the patient back either the same day or the next day if it is deemed safe to resect additional lesion or if there is residual lesion obscured from the surgeon’s view. In our experience, avoiding hemostatic agents in the operative cavity allows for a better delineation of the brain/cavernoma interface on the MRI T2 thin-cut sequence, and we have avoided hemostatic agents in the more recent part of our experience. Additionally, it is possible to find cavernous malformations that have more than one distinct component or are two separate lesions that do not fully communicate in the operative cavity; this is where an immediate postoperative MRI scan can help aid further removal to achieve a gross total resection. An institutional philosophy has been to err on the cautious side; it is always possible to take more lesion out but not vice versa. The decision to limit or cease further resection of the lesions should be dictated by anatomic features in the resection cavity, such as proximity to motor fibers as suggested by neuronavigation or neuromonitoring or a venous anomaly that hinders the view. The term “minimally invasive” applies here and is appropriate but does not and should not reflect the exposure afforded by the craniotomy. Limiting one’s approach to the lesion with a small access corridor may be less invasive but can injure brain when retracted excessively. The one cautionary note with regard to recommending intentionally a less than total resection is the danger involved with rehemorrhage from residual lesions after surgery, as reported by Gross et al. (3) in a review of 1390 cases in the literature. There are additional points to make, all of which can make this surgery a more “minimally invasive” but maximally effective procedure:
y In our recently published experience (1), we realized that in the latter part of the experience we were approaching all of the lesions with 1 of 5 approaches (orbitozygomatic, suboccipital with or with telovelar, lateral supracerebellar infratentorial [SCIT], retrosigmoid, or far-lateral). The suboccipital approaches can and often are combined to tailor the craniotomy to the lesions (i.e., retrosigmoid/far-lateral, supracerebellar/retrosigmoid, or suboccipital/far-lateral). The petrosal approaches were largely abandoned because they involved an additional but unwarranted excess morbidity. The SCIT and retrosigmoid skin incisions are comparable in size and smaller than the incisions used for the other three approaches.
y A balance between minimizing bone removal and minimizing brain manipulation is important. As craniotomies become smaller, manipulation increases, and vice versa (i.e., an orbitozygomatic approach involves more bone removal and less frontal lobe retraction).
y Gravity retraction of the cerebellum so that the tentorium is parallel to the floor and positioned above the cerebellum relative to the ground allows for minimally invasive lateral SCIT approaches. It avoids the need for a lumbar drain or use of the prone position that may require increased traction on the superior cerebellum.
WORLD NEUROSURGERY 79 [5/6]: 638-640, MAY/JUNE 2013
y In regard to instrumentation, we rarely, if ever, require a fixed retractor for these cases. This need can be overcome with instrumentation and additional maneuvers listed subsequently. The use of lighted instruments and fine micrograspers in our institutional experience enhances both visibility and maneuverability in a small deep opening in the brainstem. The opening into the brainstem is made with microforceps without teeth rather than bipolar forceps to avoid coagulation injury and to make a fine entry site.
y Continuous repositioning of the patient by rotating the body or elevating or dropping the head and rotating the microscope are crucial to maximize the effectiveness of a smaller opening in these operations.
y The use of cisternal/sulcal dissection can greatly enhance visibility in the posterior fossa, making the most of the opening (craniotomy). This dissection can increase access, while taking advantage of natural cleavage planes to mobilize brain and allow more gentle removal of cavernous malformations.
y The telovelar approach makes use of the cerebellomedullary fissure to separate the tonsil from the brainstem and allow increased visualization of the lateral and superior aspects of the fourth ventricle.
y The arachnoid between the vermis and tonsil is continuous with this cerebellomedullary fissure (it follows the route of the distal posterior inferior cerebellar artery) and can provide further access to the middle cerebellar peduncle when approaching deep-seated lesions from above. It avoids the need for cerebellar hemisphere brain transgression.
y In the retrosigmoid approach to the pons, when deciding to enter in the middle cerebellar peduncle, dissection of the horizontal fissure of the cerebellum further increases the ability to look lateral to medial when accessing the brainstem just posterior to the fifth cranial nerve. Accessing the lesion through the middle cerebellar peduncle uses less craniotomy than one would need otherwise.
y In the low retrosigmoid approach, dissection of the foramen of Luschka by shrinking the choroid plexus, mobilizing the flocculus, and splitting the potential space between the cranial nerve VII–VIII complex and the cranial nerve IX–XI complex back into the fourth ventricle allows additional lateral to medial visibility of the pontomedullary brainstem and floor of the fourth ventricle.
y For supracerebellar approaches, dividing the tentorium increases visualization of the supratrochlear region and posterior cerebral artery and allows access to the thalamus and supratentorial midbrain.
y Improved positioning that can reduce the potential for venous hypertension to occur when turning the patient’s neck involves the park bench position or the avoidance of the prone position if and when this is possible.
y The use of intraoperative neuronavigation as we have alluded to here is critical. The 2-point method allows one to form a line between the limit of the resection, the entry into the brainstem, and the projection of that line on the surface, which predicts the most suitable craniotomy (2). Similarly, another principle is employed when microscopic dissection is under way. When performing these operations, the senior author
www.WORLDNEUROSURGERY.org
639
PERSPECTIVES
(R.F.S.) lines up the limit of the cavernous malformation resection on the neuronavigation and uses the trajectory view to create a path in line with the long axis of the lesion. At the same time, very fine manipulations of the microscope in two dimensions using the foot-pedal joystick are employed to line up the entry point to the lesion that is visible in the operative field of view and perfectly creates a trajectory to the limit of the lesion.
y To achieve cerebrospinal fluid (CSF) egress, patiently obtaining CSF relaxation from the cisterna magna on a retrosigmoid approach and the quadrigeminal cistern on a lateral SCIT approach as the first step allows for relaxation of the cerebellum (in conjunction with gravity retraction) that obviates the need for lumbar drainage, retractors, or extensive manipulation of or potential injury to the cerebellar cortex. Finally, at our institution, we do not currently use the endoscope for brainstem cavernous malformation surgery because we believe the size of the endoscopes does not allow them to give a
REFERENCES 1. Abla AA, Lekovic GP, Turner JD, de Oliveira JG, Porter R, Spetzler RF: Advances in the treatment and outcome of brainstem cavernous malformation surgery: a single-center case series of 300 surgically treated patients. Neurosurgery 68:403-414, 2011. 2. Brown A, Thompson B, Spetzler RF: The two point method: evaluating brain stem lesions. BNI Quarterly 12(1):20-24, 1996.
640
www.SCIENCEDIRECT.com
closer vantage point of the brainstem cavernoma cavity (i.e., fitting the endoscope between cranial nerves). However, with improved technology and increased resolution and light in progressively smaller, more flexible endoscopes, this situation will likely change. The progression will start with using the endoscope for inspection of the cavity before it is used as an adjunct to resection of the lesion. A midline endoscopic endonasal approach is an exception that has previously been reported (4, 5). However, in both cases, the perioperative course involved CSF leak. As the approach at our institution has become more minimally invasive, the added experience of the senior author (R.F.S.) has led not only to smaller openings but also, more importantly, to smarter and more refined exposure. Such experience and the above-listed tenets have afforded the ability to do more with less. Still, exposure is everything. Inadequate exposure leads to brain retraction, which can potentially cause ischemia and subpial injury to the brain.
3. Gross BA, Batjer HH, Awad IA, Bendok BR, Du R: Brainstem cavernous malformations: 1390 surgical cases from the literature. World Neurosurg 2012 Apr 5 [Epub ahead of print]. 4. Kimball MM, Lewis SB, Werning JW, Mocco JD: Resection of a pontine cavernous malformation via an endoscopic endonasal approach: a case report. Neurosurgery 71:186-193, 2012. 5. Sanborn MR, Kramarz MJ, Storm PB, Adappa ND, Palmer JN, Lee JY: Endoscopic, endonasal, transclival
resection of a pontine cavernoma: case report. Neurosurgery 71:198-203, 2012. Citation: World Neurosurg. (2013) 79, 5/6:638-640. http://dx.doi.org/10.1016/j.wneu.2013.01.053 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter © 2013 Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2013.01.053
Robert F. Spetzler, M.D. Director, Barrow Neurological Institute (BNI) J.N. Harber Chair of Neurological Surgery at BNI Chairman and President, Barrow Neurosurgical Associates, Professor of Surgery Section of Neurosurgery, University of Arizona College of Medicine
Minimally Invasive, but Not at the Cost of Maximally Effective, in the Surgical Removal of Brainstem Cavernous Malformations Adib A. Abla and Robert F. Spetzler
I
n the current issue of WORLD NEUROSURGERY, Mai et al. review a series of 22 patients with 26 brainstem cavernous malformations. At an average of 26.6 months of follow-up, 14 patients had a modified Rankin score (mRS) of 0 or 1, and an additional 3 patients had a mRS of 2. A final mRS of 3 or 4 was achieved in 6 patients. Two patients had residual lesions but elected not to undergo additional surgery. The surgical approaches involved suboccipital craniotomy (n ⫽ 6), orbitozygomatic craniotomy (n ⫽ 5), transpetrosal approach (n ⫽ 4), combined transtemporal/transpetrosal (n ⫽ 2), lateral supracerebellar approach (n ⫽ 2), occipital transtentorial (n ⫽ 1), transmaxillary/transclival (n ⫽ 1), retrosigmoid (n ⫽ 1), presigmoid/ transsigmoid (n ⫽ 1), subtemporal/infratentorial (n ⫽ 1), and supracerebellar/transtentorial (n ⫽ 1). The article is concise and well-written with many salient points. The article presents various case examples in the text with excellent figures that demonstrate the trajectory from the craniotomy to the brainstem lesion. The authors obtained excellent clinical and radiographic outcomes and make valid arguments based on these 22 patients. Their surgical indications, surgical technique, and preservation of developmental venous anomalies are consistent with our institutional approach. It is very much on par with our institutional experience (1) that patients after these surgeries often experience new deficits, such as numbness, ataxia, diplopia, or dysmetria, which are frequently mild and transient. However, such small setbacks are acceptable when considering the damage caused by repeated hemorrhage and mass effect in many untreated patients who are often devastated by the bleeds. Overall, the authors should be congratulated on this experience. In the resection of brainstem cavernous malformations, there is a tipping point that involves the balance between obtaining a
Key words 䡲 Brainstem 䡲 Cavernoma 䡲 Cavernous malformation 䡲 Skull base
638
Abbreviations and Acronyms CSF: Cerebrospinal fluid MRI: Magnetic resonance imaging mRS: Modified Rankin score SCIT: Supracerebellar infratentorial
www.SCIENCEDIRECT.com
gross total resection and keeping a patient’s neurologic function as close to baseline as possible. The authors’ conclusion is that they would favor a less than total resection, while advocating for a minimally invasive approach to the lesion to maintain function. We are very much in agreement, but there are important caveats and discussion points which we would like to elaborate on here. When defining what is minimally invasive, it can apply to many aspects of the case. It can refer to the size of the skin incision; to the size of the craniotomy; to the amount of dura mater that is opened; or to the pial opening into the brain, or entry site into the brainstem. There is no well-accepted definition of what makes a surgical procedure minimally invasive. In some cases, the procedure may involve an endoscope or a laser, and many neurosurgeons are probably familiar with advertising that touts the benefits of “laser” or “endoscopic” surgery. Also, as it relates to brainstem cavernous malformations, the term “minimally invasive” does not necessarily refer to keyhole endoscopic microneurosurgery at the present time. “Minimally invasive” is a relative term as it relates to skull base surgery and the often extensive dissection involved. A transpetrosal/transtemporal approach may not be considered minimally invasive to some neurosurgeons. The authors’ definition of “minimally invasive” in brainstem cavernous malformation surgery involves making a small opening in the brainstem, which, as we have described previously, is often best suited parallel to the traversing nerve fibers (1), and centrally debulking the lesion first (Figure 10 in Mai et al.). We agree with Mai et al. that a less aggressive stance for residuals that have not regrown or rebled is appropriate. The nuances of the first operation that made it difficult to obtain a complete resection are unlikely to change the second time,
Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona, USA To whom correspondence should be addressed: Robert F. Spetzler, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2013) 79, 5/6:638-640. http://dx.doi.org/10.1016/j.wneu.2013.01.053
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2013.01.053
PERSPECTIVES
unless there is expansion and new mass effect attributable to further bleeding. The one option when it is unclear if there is any residual cavernous malformation is to obtain an intraoperative or immediate postoperative magnetic resonance imaging (MRI) scan and bring the patient back either the same day or the next day if it is deemed safe to resect additional lesion or if there is residual lesion obscured from the surgeon’s view. In our experience, avoiding hemostatic agents in the operative cavity allows for a better delineation of the brain/cavernoma interface on the MRI T2 thin-cut sequence, and we have avoided hemostatic agents in the more recent part of our experience. Additionally, it is possible to find cavernous malformations that have more than one distinct component or are two separate lesions that do not fully communicate in the operative cavity; this is where an immediate postoperative MRI scan can help aid further removal to achieve a gross total resection. An institutional philosophy has been to err on the cautious side; it is always possible to take more lesion out but not vice versa. The decision to limit or cease further resection of the lesions should be dictated by anatomic features in the resection cavity, such as proximity to motor fibers as suggested by neuronavigation or neuromonitoring or a venous anomaly that hinders the view. The term “minimally invasive” applies here and is appropriate but does not and should not reflect the exposure afforded by the craniotomy. Limiting one’s approach to the lesion with a small access corridor may be less invasive but can injure brain when retracted excessively. The one cautionary note with regard to recommending intentionally a less than total resection is the danger involved with rehemorrhage from residual lesions after surgery, as reported by Gross et al. (3) in a review of 1390 cases in the literature. There are additional points to make, all of which can make this surgery a more “minimally invasive” but maximally effective procedure:
y In our recently published experience (1), we realized that in the latter part of the experience we were approaching all of the lesions with 1 of 5 approaches (orbitozygomatic, suboccipital with or with telovelar, lateral supracerebellar infratentorial [SCIT], retrosigmoid, or far-lateral). The suboccipital approaches can and often are combined to tailor the craniotomy to the lesions (i.e., retrosigmoid/far-lateral, supracerebellar/retrosigmoid, or suboccipital/far-lateral). The petrosal approaches were largely abandoned because they involved an additional but unwarranted excess morbidity. The SCIT and retrosigmoid skin incisions are comparable in size and smaller than the incisions used for the other three approaches.
y A balance between minimizing bone removal and minimizing brain manipulation is important. As craniotomies become smaller, manipulation increases, and vice versa (i.e., an orbitozygomatic approach involves more bone removal and less frontal lobe retraction).
y Gravity retraction of the cerebellum so that the tentorium is parallel to the floor and positioned above the cerebellum relative to the ground allows for minimally invasive lateral SCIT approaches. It avoids the need for a lumbar drain or use of the prone position that may require increased traction on the superior cerebellum.
WORLD NEUROSURGERY 79 [5/6]: 638-640, MAY/JUNE 2013
y In regard to instrumentation, we rarely, if ever, require a fixed retractor for these cases. This need can be overcome with instrumentation and additional maneuvers listed subsequently. The use of lighted instruments and fine micrograspers in our institutional experience enhances both visibility and maneuverability in a small deep opening in the brainstem. The opening into the brainstem is made with microforceps without teeth rather than bipolar forceps to avoid coagulation injury and to make a fine entry site.
y Continuous repositioning of the patient by rotating the body or elevating or dropping the head and rotating the microscope are crucial to maximize the effectiveness of a smaller opening in these operations.
y The use of cisternal/sulcal dissection can greatly enhance visibility in the posterior fossa, making the most of the opening (craniotomy). This dissection can increase access, while taking advantage of natural cleavage planes to mobilize brain and allow more gentle removal of cavernous malformations.
y The telovelar approach makes use of the cerebellomedullary fissure to separate the tonsil from the brainstem and allow increased visualization of the lateral and superior aspects of the fourth ventricle.
y The arachnoid between the vermis and tonsil is continuous with this cerebellomedullary fissure (it follows the route of the distal posterior inferior cerebellar artery) and can provide further access to the middle cerebellar peduncle when approaching deep-seated lesions from above. It avoids the need for cerebellar hemisphere brain transgression.
y In the retrosigmoid approach to the pons, when deciding to enter in the middle cerebellar peduncle, dissection of the horizontal fissure of the cerebellum further increases the ability to look lateral to medial when accessing the brainstem just posterior to the fifth cranial nerve. Accessing the lesion through the middle cerebellar peduncle uses less craniotomy than one would need otherwise.
y In the low retrosigmoid approach, dissection of the foramen of Luschka by shrinking the choroid plexus, mobilizing the flocculus, and splitting the potential space between the cranial nerve VII–VIII complex and the cranial nerve IX–XI complex back into the fourth ventricle allows additional lateral to medial visibility of the pontomedullary brainstem and floor of the fourth ventricle.
y For supracerebellar approaches, dividing the tentorium increases visualization of the supratrochlear region and posterior cerebral artery and allows access to the thalamus and supratentorial midbrain.
y Improved positioning that can reduce the potential for venous hypertension to occur when turning the patient’s neck involves the park bench position or the avoidance of the prone position if and when this is possible.
y The use of intraoperative neuronavigation as we have alluded to here is critical. The 2-point method allows one to form a line between the limit of the resection, the entry into the brainstem, and the projection of that line on the surface, which predicts the most suitable craniotomy (2). Similarly, another principle is employed when microscopic dissection is under way. When performing these operations, the senior author
www.WORLDNEUROSURGERY.org
639
PERSPECTIVES
(R.F.S.) lines up the limit of the cavernous malformation resection on the neuronavigation and uses the trajectory view to create a path in line with the long axis of the lesion. At the same time, very fine manipulations of the microscope in two dimensions using the foot-pedal joystick are employed to line up the entry point to the lesion that is visible in the operative field of view and perfectly creates a trajectory to the limit of the lesion.
y To achieve cerebrospinal fluid (CSF) egress, patiently obtaining CSF relaxation from the cisterna magna on a retrosigmoid approach and the quadrigeminal cistern on a lateral SCIT approach as the first step allows for relaxation of the cerebellum (in conjunction with gravity retraction) that obviates the need for lumbar drainage, retractors, or extensive manipulation of or potential injury to the cerebellar cortex. Finally, at our institution, we do not currently use the endoscope for brainstem cavernous malformation surgery because we believe the size of the endoscopes does not allow them to give a
REFERENCES 1. Abla AA, Lekovic GP, Turner JD, de Oliveira JG, Porter R, Spetzler RF: Advances in the treatment and outcome of brainstem cavernous malformation surgery: a single-center case series of 300 surgically treated patients. Neurosurgery 68:403-414, 2011. 2. Brown A, Thompson B, Spetzler RF: The two point method: evaluating brain stem lesions. BNI Quarterly 12(1):20-24, 1996.
640
www.SCIENCEDIRECT.com
closer vantage point of the brainstem cavernoma cavity (i.e., fitting the endoscope between cranial nerves). However, with improved technology and increased resolution and light in progressively smaller, more flexible endoscopes, this situation will likely change. The progression will start with using the endoscope for inspection of the cavity before it is used as an adjunct to resection of the lesion. A midline endoscopic endonasal approach is an exception that has previously been reported (4, 5). However, in both cases, the perioperative course involved CSF leak. As the approach at our institution has become more minimally invasive, the added experience of the senior author (R.F.S.) has led not only to smaller openings but also, more importantly, to smarter and more refined exposure. Such experience and the above-listed tenets have afforded the ability to do more with less. Still, exposure is everything. Inadequate exposure leads to brain retraction, which can potentially cause ischemia and subpial injury to the brain.
3. Gross BA, Batjer HH, Awad IA, Bendok BR, Du R: Brainstem cavernous malformations: 1390 surgical cases from the literature. World Neurosurg 2012 Apr 5 [Epub ahead of print]. 4. Kimball MM, Lewis SB, Werning JW, Mocco JD: Resection of a pontine cavernous malformation via an endoscopic endonasal approach: a case report. Neurosurgery 71:186-193, 2012. 5. Sanborn MR, Kramarz MJ, Storm PB, Adappa ND, Palmer JN, Lee JY: Endoscopic, endonasal, transclival
resection of a pontine cavernoma: case report. Neurosurgery 71:198-203, 2012. Citation: World Neurosurg. (2013) 79, 5/6:638-640. http://dx.doi.org/10.1016/j.wneu.2013.01.053 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter © 2013 Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2013.01.053