A Novel Approach of Navigation-Assisted Flexible Neuroendoscopy

A Novel Approach of Navigation-Assisted Flexible Neuroendoscopy Abstract BACKGROUND AND IMPORTANCE Neuronavigation-assisted endoscopy is commonly used for skull base and intraventricular surgery. Flexible neuroendoscopy offers certain advantages over rigid endoscopy; however, a major disadvantage of the flexible endoscope has been easy disorientation in the flexed position. Neuronavigation-assisted flexible neuroendoscopy was not available until now. This is the first report of the use of navigation-assisted flexible neuroendoscopy in a patient with hydrocephalus. CLINICAL PRESENTATION A 10-mo-old girl presented with irritability and vomiting to the emergency department and was found to have severe hydrocephalus. The patient underwent successful endoscopic third ventriculostomy and exploration of the ventricles (lateral, third, cerebral aqueduct, fourth) and basal cisterns with the flexible neuroendoscopy assisted with electromagnetic neuronavigation. CONCLUSION As demonstrated by this initial experience, neuronavigation-assisted flexible neuroendoscopy is a feasible and safe tool, endoscopic procedures with the flexible endoscope may be possible in a safer manner. We report the first use of neuronavigation-assisted flexible neuroendoscopy to perform an ETV and exploration of the entire ventricular system. Further evaluation will be necessary to define and expand its applications in neurosurgery. Flexible neuroendoscopy, Hydrocephalus, Neuroendoscopy, Electromagnetic neuronavigation ABBREVIATIONS ABBREVIATIONS CSF cerebrospinal fluid ETV endoscopic third ventriculostomy Neuroendoscopic procedures are constantly increasing in variety and scope to become an essential part of the neurosurgery armamentarium.1 Flexible neuroendoscopy is not new and has been used by many neurosurgeons, although it has not gained as much popularity as rigid endoscopy due to lesser image quality, fragility, and the potential for disorientation in the flexed position. Neuronavigation-assisted endoscopy is commonly used but it had been only available for rigid endoscopy.2,3 An emerging solution that addresses this limitation is the coupling of electromagnetic navigation with the flexible neuroendoscope allowing tracking of the steerable tip. Here we present a case of a patient with hydrocephalus who underwent successfully navigation-assisted flexible endoscopic third ventriculostomy (ETV) and exploration of the ventricles (lateral, third, and fourth ventricle and cerebral aqueduct) and basal cisterns. This is the first case that describes the use of neuronavigation with flexible neuroendoscopy. This report was approved by the Ethics Committee. The patient's parents gave informed consent. CLINICAL PRESENTATION A 10-mo-old female presented with vomiting and lethargy to the emergency department. Neurological examination showed increased head circumference for her age, papilledema, and bulging fontanelle. Patient was a premature newborn with low-weight at birth, retinopathy, and ventriculomegaly, unfortunately the patient was lost to follow-up after initial discharge. Current neuroimaging demonstrated severe ventriculomegaly possible secondary to obstructive hydrocephalus. In order to facilitate cerebrospinal fluid (CSF) diversion, an ETV was planned. We opted to use a flexible neuroendoscope to perform an ETV and exploration of the cerebral aqueduct and fourth ventricle using the same burr hole and surgical trajectory.4 The endoscopic procedure was assisted with the use of electromagnetic neuronavigation. MRI-based frameless neuronavigation (Fiagon Navigation System, Hennigsdorf, Germany) was used to map an entry point at the coronal suture and 2.5 cm right of midline (Video and Legend, Supplemental Digital Content). The lateral ventricle was access with a flexible neuroendoscope (Karl Storz GmbH, Tuttlingen, Germany). A 0.85-mm diameter and 60-cm-long malleable flexible navigated glidewire (Fiagon GmbH, Hennigsdorf, Germany) was inserted into the endoscope working channel (1-mm diameter) for navigation purposes. The endoscope was passed through the foramen of Monro and the floor of the third ventricle was identified (Figures 1 and 2). Third ventriculostomy and Liliequist membrane perforation were performed in a standard fashion. The navigation probe was used again and a complete exploration of the ventricular system was carried. We identified the ipsilateral frontal, occipital (Figure 3), and temporal horns (Figure 4). Then, the contralateral ventricle was reached through the already fenestrated septum pellucidum, where the contralateral frontal and occipital horns were also visualized. The scope was maneuvered back into the third ventricle and through the ETV the basal cisterns (interpeduncular, prepontine, premedullary, and cerebellopontine) were explored (Figure 5). The endoscope was directed towards the posterior portion of the third ventricle (Figure 6), and through the cerebral aqueduct the fourth ventricle was reached (Figure 7). The cerebral aqueduct had a normal appearance with no evidence of aqueductal stenosis. Within the fourth ventricle we observed: the floor of the fourth ventricle, cerebellar vermix, choroid plexus, obex, cerebellar tonsils, both Luschka foramina, and Magendie foramen. The flexible endoscope was then carefully drawn back into the third and lateral ventricles. The cerebral aqueduct and right fornix were intact with no evidence of injury from the endoscopic procedure. The patient awoke in stable neurological condition and remained neurologically intact postoperatively. The patient's mother reported the patient was doing well in follow-up several weeks later. Follow-up CT scan demonstrated improvement of hydrocephalus. FIGURE 1. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the right foramen of Monro looking into the third ventricle. FIGURE 1. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the right foramen of Monro looking into the third ventricle. FIGURE 2. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated in the third ventricle looking at the floor of the third ventricle. FIGURE 2. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated in the third ventricle looking at the floor of the third ventricle. FIGURE 3. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the right atrium and looking into the right occipital horn. FIGURE 3. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the right atrium and looking into the right occipital horn. FIGURE 4. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the right temporal horn looking at the right hippocampus. FIGURE 4. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the right temporal horn looking at the right hippocampus. FIGURE 5. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the interpeduncular cistern looking at the left internal carotid artery. FIGURE 5. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the interpeduncular cistern looking at the left internal carotid artery. FIGURE 6. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the posterior portion of the third ventricle looking at the entrance of the cerebral aqueduct. FIGURE 6. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the posterior portion of the third ventricle looking at the entrance of the cerebral aqueduct. FIGURE 7. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated in the fourth ventricle looking at the foramen of Magendie. FIGURE 7. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated in the fourth ventricle looking at the foramen of Magendie. DISCUSSION Neuroendoscopy has a history of steady growth. Innovations have produced endoscopes with wide variability in view angle, resolution, illumination, and flexibility. Endoscopic procedures and clinical indications of flexible neuroendoscopy have expanded, including: ETV and choroid plexus cauterization,5 lamina terminalis fenestration,6 intraventricular tumor resection,7,8 aqueductoplasty,9 transaqueductal Magendie and Luschka foraminoplasty,10 basal cistern exploration and biopsy,11 and neurocysticercosis cyst extraction.12 Flexible neuroendoscopy has not gained as much popularity as the rigid endoscope.13 This is in part because of the lesser image quality, lower brightness, and the potential for disorientation in the flexed position. However, the quality and characteristics of flexible neuroendoscopes have improved considerably over the past years. The recently developed videoscope is unique due to the high-quality image, the 180° rotation of the flexible insertion tube, the ability to observe capillary blood vessels, and the capability to produce enhanced images of the subependymal capillary blood vessels under the ependymal layers if used together with narrow-band imaging technology.14 Another newly developed high-definition flexible endoscope enabled by camera-on-a-chip technology has also overcome the problem of lesser image quality and poor resolution.8 These 2 new flexible endoscopes have addressed the problems of lesser image quality, lower brightness, and fragility of equipment by averting the trade-off between the range of motion provided by the flexible endoscope and the high-resolution imaging provided by rigid endoscope. Neuronavigation-Assisted Flexible Neuroendoscopy Another disadvantage of the flexible neuroendoscope is the potential disorientation in the flexed position, particularly in patients with no normal anatomical landmarks for orientation. Neuronavigation has been commonly used with rigid endoscopy but not with flexible neuroendsocopy, until now. Here, we present an initial experience using neuronavigation incorporated to a flexible neuroendoscope. Using electromagnetic tracking and a malleable navigated glidewire inside of the endoscope working channel, we were able to track the tip of the flexible neuroendoscope while maneuvering it through the ventricular system during the entire procedure. This allowed us to know in real time where the tip of the endoscope was located even with the tip of the endoscope in the flexed position. We encountered 2 problems that still need to be solved. First, the moment the glidewire was replaced for an instrument (eg, grasping forceps) navigation was no longer available. Second, we were able to track only the tip of the endoscope, it would have been interesting and useful to track multiple sites of the endoscope and know the exact location of the endoscope shaft while in the flexed position. Perhaps multiple miniaturized electromagnetic field sensors can be mounted along the endoscope allowing us knowing the accurate location of the entire length of the endoscope. A prototype of this ideal flexible neuroendoscope is currently being developed but has not been used in humans.15 With advances in neuronavigation and image-guided surgery, neuroendoscopy has the potential to overcome the limitations of lack of stereoscopic view and the ability to track the tip of the endoscope. Loss of orientation or view, with consequent inability to achieve surgical goals, is a source of anxiety and consumes valuable operating time, as well as a source of potential morbidity. In the near future, for flexible neuroendoscopy, there would be an advantage to a technology that would allow the surgeon to know where the entire shaft is so that it does not negatively impact critical structures behind the field of view. This kind of virtual representation, or even definition of “no-fly zones” for the back of the endoscope could help promote this technology among surgeons who are not currently comfortable with it. Key Points To avoid difficulty with instrument insertion/exchange the endoscope should be positioned neutral (0°). However, the flexibility of the navigable glidewire allows its insertion/removal with the flexible endoscope in the flexed position. Avoid instrument insertion/exchange in small spaces (eg cerebral aqueduct). During a navigation-assisted flexible neuroendoscopic procedure, the site or region of interest within the ventricle is identified first with the navigable glidewire, then the glidewire has to be removed and the appropriate instrument inserted. This is because current flexible neuroendoscopes have only 1 working channel. The surgeon has to keep in mind the essential steps and maneuvers (degree of endoscope rotation, flexion, etc.) necessary to approach the fourth ventricle or basal cisterns and do the opposite maneuvers carefully and slowly when withdrawing the endoscope. Always try to withdraw the endoscope in a neutral position and never in a flexed position. CONCLUSION Neuronavigation-assisted flexible neuroendoscopy is a feasible and safe tool for intraventricular neurosurgical procedures; endoscopic procedures with the flexible endoscope may be possible in a safer manner. We report the first use of neuronavigation-assisted flexible neuroendoscopy to perform an ETV and exploration of the entire ventricular system. Further evaluation will be necessary to define and expand its applications in neurosurgery. Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article. REFERENCES 1. Cappabianca P, Cinalli G, Gangemi M et al.   Application of neuroendoscopy to intraventricular lesions. Neurosurgery . 2008; 62( suppl 2): SHC-575-SHC-598. 2. Alberti O, Riegel T, Hellwig D, Bertalanffy H. Frameless navigation and endoscopy. J Neurosurg . 2001; 95( 3): 541- 543. Google Scholar PubMed  3. Sangra M, Clark S, Hayhurst C, Mallucci C. Electromagnetic-guided neuroendoscopy in the pediatric population. J Neurosurg Pediatr . 2009; 3( 4): 325- 330. Google Scholar CrossRef Search ADS PubMed  4. Torres-Corzo JG, Rangel-Castilla L, Nakaji P. Neuroendoscopic Surgery . 1st ed. New York, NY: Thieme; 2016. Google Scholar CrossRef Search ADS   5. Warf BC, Tracy S, Mugamba J. Long-term outcome for endoscopic third ventriculostomy alone or in combination with choroid plexus cauterization for congenital aqueductal stenosis in African infants. J Neurosurg Pediatr . 2012; 10( 2): 108- 111. Google Scholar CrossRef Search ADS PubMed  6. Rangel-Castilla L, Hwang SW, Jea A, Torres-Corzo J. Efficacy and safety of endoscopic transventricular lamina terminalis fenestration for hydrocephalus. Neurosurgery . 2012; 71( 2): 464- 473; discussion 473. Google Scholar CrossRef Search ADS PubMed  7. Ogiwara H, Morota N. Flexible endoscopy for management of intraventricular brain tumors in patients with small ventricles. J Neurosurg Pediatr . 2014; 14( 5): 490- 494. Google Scholar CrossRef Search ADS PubMed  8. Friedman GN, Grannan BL, Nahed BV, Codd PJ. Initial experience with high-definition camera-on-a-chip flexible endoscopy for intraventricular neurosurgery. World Neurosurg . 2015; 84( 6): 2053- 2058. Google Scholar CrossRef Search ADS PubMed  9. Antes S, Salah M, Linsler S, Tschan CA, Breuskin D, Oertel J. Aqueductal stenting with an intra-catheter endoscope—a technical note. Childs Nerv Syst . 2016; 32( 2): 359- 363. Google Scholar CrossRef Search ADS PubMed  10. Torres-Corzo J, Sanchez-Rodriguez J, Cervantes D et al.   Endoscopic transventricular transaqueductal Magendie and Luschka foraminoplasty for hydrocephalus. Neurosurgery . 2014; 74( 4): 426- 435. Google Scholar CrossRef Search ADS PubMed  11. Torres-Corzo J, Vinas-Rios JM, Sanchez-Aguilar M, Vecchia RR, Chalita-Williams JC, Rangel-Castilla L. Transventricular neuroendoscopic exploration and biopsy of the basal cisterns in patients with Basal meningitis and hydrocephalus. World Neurosurg . 2012; 77( 5-6): 762- 771. Google Scholar CrossRef Search ADS PubMed  12. Proano JV, Torres-Corzo J, Rodriguez-Della Vecchia R, Guizar-Sahagun G, Rangel-Castilla L. Intraventricular and subarachnoid basal cisterns neurocysticercosis: a comparative study between traditional treatment versus neuroendoscopic surgery. Childs Nerv Syst . 2009; 25( 11): 1467- 1475. Google Scholar CrossRef Search ADS PubMed  13. Zada G, Liu C, Apuzzo ML. "Through the looking glass": optical physics, issues, and the evolution of neuroendoscopy. World Neurosurg . 2013; 79( 2 suppl): S3- 13. Google Scholar CrossRef Search ADS PubMed  14. Oka K. Introduction of the videoscope in neurosurgery. Neurosurgery . 2008; 62( 5 suppl 2): ONS337- ONS340. Google Scholar PubMed  15. Atsumi H, Matsumae M, Hirayama A et al.   Newly developed electromagnetic tracked flexible neuroendoscope. Neurol Med Chir (Tokyo) . 2011; 51( 8): 611- 616. Google Scholar CrossRef Search ADS PubMed  Supplemental digital content is available for this article at operativeneurosurgery-online.com. COMMENTS The authors provide a very interesting case report demonstrating the use of a flexible neuroendoscope with the assistance of stereotactic neuro-navigation. A navigation-compatible electromagnetic glidewire was inserted into the working channel of the endoscope. The major limitation of this technique is that the glidewire has to be removed in order to use other instruments through the endoscope, thus losing the stereotactic navigation until the wire is reinserted. The authors acknowledge this limitation and offer suggestions on the creation of an ideal future endoscope that would permit localization of the entire length of the endoscope throughout a procedure. The accompanying video and photographs provide a nice display of the views possible with the navigation-assisted flexible neuroendoscope via this glidewire method. Future developments in this field could permit expanded use of the neuroendoscope for more complex minimally invasive procedures. Carrie R. Muh Durham, North Carolina The authors present an exceptional video and description of a technique that will be useful to many surgeons practicing neuroendoscopy. Advances in technology facilitate expanded uses for the flexible endoscope. From the video, I can tell that the authors are extremely experienced and facile with the equipment. Beginning neuroendoscopists should not try to emulate this technique until they have achieved mastery of the basics. This is a very interesting demonstration and I look forward to the authors publishing more of their experience in the future. Daniel H. Fulkerson Indianapolis, Indiana The authors provide a well-written and well-illustrated technical report on the use of frameless stereotactic neuronavigation with the use of a flexible endoscope. The major source of complications in intraventricular endoscopic approaches is disorientation. Frameless stereotaxis may help to reduce disorientation, as suggested by the authors. However, neuronavigation systems, like the one used by the authors, that rely on a preoperative imaging dataset have decreasing accuracy during the surgical procedure. The reasons for this loss of accuracy are multifactorial. As an example, brain shift may occur from the loss of cerebrospinal fluid after cannulation of the ventricular system, decreasing the reliability of neuronavigation. I look forward to future studies from the authors that expand on their n of 1, and report on their experience with frameless stereotactic neuronavigation and flexible endoscopy, including their quantification and compensation for brain shift and inaccuracy of neuronavigation as the surgical procedure progresses. Andrew Jea Indianapolis, Indiana Copyright © 2017 by the Congress of Neurological Surgeons http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Operative Neurosurgery Oxford University Press

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Abstract

Abstract BACKGROUND AND IMPORTANCE Neuronavigation-assisted endoscopy is commonly used for skull base and intraventricular surgery. Flexible neuroendoscopy offers certain advantages over rigid endoscopy; however, a major disadvantage of the flexible endoscope has been easy disorientation in the flexed position. Neuronavigation-assisted flexible neuroendoscopy was not available until now. This is the first report of the use of navigation-assisted flexible neuroendoscopy in a patient with hydrocephalus. CLINICAL PRESENTATION A 10-mo-old girl presented with irritability and vomiting to the emergency department and was found to have severe hydrocephalus. The patient underwent successful endoscopic third ventriculostomy and exploration of the ventricles (lateral, third, cerebral aqueduct, fourth) and basal cisterns with the flexible neuroendoscopy assisted with electromagnetic neuronavigation. CONCLUSION As demonstrated by this initial experience, neuronavigation-assisted flexible neuroendoscopy is a feasible and safe tool, endoscopic procedures with the flexible endoscope may be possible in a safer manner. We report the first use of neuronavigation-assisted flexible neuroendoscopy to perform an ETV and exploration of the entire ventricular system. Further evaluation will be necessary to define and expand its applications in neurosurgery. Flexible neuroendoscopy, Hydrocephalus, Neuroendoscopy, Electromagnetic neuronavigation ABBREVIATIONS ABBREVIATIONS CSF cerebrospinal fluid ETV endoscopic third ventriculostomy Neuroendoscopic procedures are constantly increasing in variety and scope to become an essential part of the neurosurgery armamentarium.1 Flexible neuroendoscopy is not new and has been used by many neurosurgeons, although it has not gained as much popularity as rigid endoscopy due to lesser image quality, fragility, and the potential for disorientation in the flexed position. Neuronavigation-assisted endoscopy is commonly used but it had been only available for rigid endoscopy.2,3 An emerging solution that addresses this limitation is the coupling of electromagnetic navigation with the flexible neuroendoscope allowing tracking of the steerable tip. Here we present a case of a patient with hydrocephalus who underwent successfully navigation-assisted flexible endoscopic third ventriculostomy (ETV) and exploration of the ventricles (lateral, third, and fourth ventricle and cerebral aqueduct) and basal cisterns. This is the first case that describes the use of neuronavigation with flexible neuroendoscopy. This report was approved by the Ethics Committee. The patient's parents gave informed consent. CLINICAL PRESENTATION A 10-mo-old female presented with vomiting and lethargy to the emergency department. Neurological examination showed increased head circumference for her age, papilledema, and bulging fontanelle. Patient was a premature newborn with low-weight at birth, retinopathy, and ventriculomegaly, unfortunately the patient was lost to follow-up after initial discharge. Current neuroimaging demonstrated severe ventriculomegaly possible secondary to obstructive hydrocephalus. In order to facilitate cerebrospinal fluid (CSF) diversion, an ETV was planned. We opted to use a flexible neuroendoscope to perform an ETV and exploration of the cerebral aqueduct and fourth ventricle using the same burr hole and surgical trajectory.4 The endoscopic procedure was assisted with the use of electromagnetic neuronavigation. MRI-based frameless neuronavigation (Fiagon Navigation System, Hennigsdorf, Germany) was used to map an entry point at the coronal suture and 2.5 cm right of midline (Video and Legend, Supplemental Digital Content). The lateral ventricle was access with a flexible neuroendoscope (Karl Storz GmbH, Tuttlingen, Germany). A 0.85-mm diameter and 60-cm-long malleable flexible navigated glidewire (Fiagon GmbH, Hennigsdorf, Germany) was inserted into the endoscope working channel (1-mm diameter) for navigation purposes. The endoscope was passed through the foramen of Monro and the floor of the third ventricle was identified (Figures 1 and 2). Third ventriculostomy and Liliequist membrane perforation were performed in a standard fashion. The navigation probe was used again and a complete exploration of the ventricular system was carried. We identified the ipsilateral frontal, occipital (Figure 3), and temporal horns (Figure 4). Then, the contralateral ventricle was reached through the already fenestrated septum pellucidum, where the contralateral frontal and occipital horns were also visualized. The scope was maneuvered back into the third ventricle and through the ETV the basal cisterns (interpeduncular, prepontine, premedullary, and cerebellopontine) were explored (Figure 5). The endoscope was directed towards the posterior portion of the third ventricle (Figure 6), and through the cerebral aqueduct the fourth ventricle was reached (Figure 7). The cerebral aqueduct had a normal appearance with no evidence of aqueductal stenosis. Within the fourth ventricle we observed: the floor of the fourth ventricle, cerebellar vermix, choroid plexus, obex, cerebellar tonsils, both Luschka foramina, and Magendie foramen. The flexible endoscope was then carefully drawn back into the third and lateral ventricles. The cerebral aqueduct and right fornix were intact with no evidence of injury from the endoscopic procedure. The patient awoke in stable neurological condition and remained neurologically intact postoperatively. The patient's mother reported the patient was doing well in follow-up several weeks later. Follow-up CT scan demonstrated improvement of hydrocephalus. FIGURE 1. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the right foramen of Monro looking into the third ventricle. FIGURE 1. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the right foramen of Monro looking into the third ventricle. FIGURE 2. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated in the third ventricle looking at the floor of the third ventricle. FIGURE 2. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated in the third ventricle looking at the floor of the third ventricle. FIGURE 3. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the right atrium and looking into the right occipital horn. FIGURE 3. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the right atrium and looking into the right occipital horn. FIGURE 4. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the right temporal horn looking at the right hippocampus. FIGURE 4. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the right temporal horn looking at the right hippocampus. FIGURE 5. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the interpeduncular cistern looking at the left internal carotid artery. FIGURE 5. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the interpeduncular cistern looking at the left internal carotid artery. FIGURE 6. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the posterior portion of the third ventricle looking at the entrance of the cerebral aqueduct. FIGURE 6. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated at the posterior portion of the third ventricle looking at the entrance of the cerebral aqueduct. FIGURE 7. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated in the fourth ventricle looking at the foramen of Magendie. FIGURE 7. View largeDownload slide Neuronavigation-assisted intraoperative flexible endoscopic images. The endoscope is situated in the fourth ventricle looking at the foramen of Magendie. DISCUSSION Neuroendoscopy has a history of steady growth. Innovations have produced endoscopes with wide variability in view angle, resolution, illumination, and flexibility. Endoscopic procedures and clinical indications of flexible neuroendoscopy have expanded, including: ETV and choroid plexus cauterization,5 lamina terminalis fenestration,6 intraventricular tumor resection,7,8 aqueductoplasty,9 transaqueductal Magendie and Luschka foraminoplasty,10 basal cistern exploration and biopsy,11 and neurocysticercosis cyst extraction.12 Flexible neuroendoscopy has not gained as much popularity as the rigid endoscope.13 This is in part because of the lesser image quality, lower brightness, and the potential for disorientation in the flexed position. However, the quality and characteristics of flexible neuroendoscopes have improved considerably over the past years. The recently developed videoscope is unique due to the high-quality image, the 180° rotation of the flexible insertion tube, the ability to observe capillary blood vessels, and the capability to produce enhanced images of the subependymal capillary blood vessels under the ependymal layers if used together with narrow-band imaging technology.14 Another newly developed high-definition flexible endoscope enabled by camera-on-a-chip technology has also overcome the problem of lesser image quality and poor resolution.8 These 2 new flexible endoscopes have addressed the problems of lesser image quality, lower brightness, and fragility of equipment by averting the trade-off between the range of motion provided by the flexible endoscope and the high-resolution imaging provided by rigid endoscope. Neuronavigation-Assisted Flexible Neuroendoscopy Another disadvantage of the flexible neuroendoscope is the potential disorientation in the flexed position, particularly in patients with no normal anatomical landmarks for orientation. Neuronavigation has been commonly used with rigid endoscopy but not with flexible neuroendsocopy, until now. Here, we present an initial experience using neuronavigation incorporated to a flexible neuroendoscope. Using electromagnetic tracking and a malleable navigated glidewire inside of the endoscope working channel, we were able to track the tip of the flexible neuroendoscope while maneuvering it through the ventricular system during the entire procedure. This allowed us to know in real time where the tip of the endoscope was located even with the tip of the endoscope in the flexed position. We encountered 2 problems that still need to be solved. First, the moment the glidewire was replaced for an instrument (eg, grasping forceps) navigation was no longer available. Second, we were able to track only the tip of the endoscope, it would have been interesting and useful to track multiple sites of the endoscope and know the exact location of the endoscope shaft while in the flexed position. Perhaps multiple miniaturized electromagnetic field sensors can be mounted along the endoscope allowing us knowing the accurate location of the entire length of the endoscope. A prototype of this ideal flexible neuroendoscope is currently being developed but has not been used in humans.15 With advances in neuronavigation and image-guided surgery, neuroendoscopy has the potential to overcome the limitations of lack of stereoscopic view and the ability to track the tip of the endoscope. Loss of orientation or view, with consequent inability to achieve surgical goals, is a source of anxiety and consumes valuable operating time, as well as a source of potential morbidity. In the near future, for flexible neuroendoscopy, there would be an advantage to a technology that would allow the surgeon to know where the entire shaft is so that it does not negatively impact critical structures behind the field of view. This kind of virtual representation, or even definition of “no-fly zones” for the back of the endoscope could help promote this technology among surgeons who are not currently comfortable with it. Key Points To avoid difficulty with instrument insertion/exchange the endoscope should be positioned neutral (0°). However, the flexibility of the navigable glidewire allows its insertion/removal with the flexible endoscope in the flexed position. Avoid instrument insertion/exchange in small spaces (eg cerebral aqueduct). During a navigation-assisted flexible neuroendoscopic procedure, the site or region of interest within the ventricle is identified first with the navigable glidewire, then the glidewire has to be removed and the appropriate instrument inserted. This is because current flexible neuroendoscopes have only 1 working channel. The surgeon has to keep in mind the essential steps and maneuvers (degree of endoscope rotation, flexion, etc.) necessary to approach the fourth ventricle or basal cisterns and do the opposite maneuvers carefully and slowly when withdrawing the endoscope. Always try to withdraw the endoscope in a neutral position and never in a flexed position. CONCLUSION Neuronavigation-assisted flexible neuroendoscopy is a feasible and safe tool for intraventricular neurosurgical procedures; endoscopic procedures with the flexible endoscope may be possible in a safer manner. We report the first use of neuronavigation-assisted flexible neuroendoscopy to perform an ETV and exploration of the entire ventricular system. Further evaluation will be necessary to define and expand its applications in neurosurgery. Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article. REFERENCES 1. Cappabianca P, Cinalli G, Gangemi M et al.   Application of neuroendoscopy to intraventricular lesions. Neurosurgery . 2008; 62( suppl 2): SHC-575-SHC-598. 2. Alberti O, Riegel T, Hellwig D, Bertalanffy H. Frameless navigation and endoscopy. J Neurosurg . 2001; 95( 3): 541- 543. Google Scholar PubMed  3. Sangra M, Clark S, Hayhurst C, Mallucci C. Electromagnetic-guided neuroendoscopy in the pediatric population. J Neurosurg Pediatr . 2009; 3( 4): 325- 330. Google Scholar CrossRef Search ADS PubMed  4. Torres-Corzo JG, Rangel-Castilla L, Nakaji P. Neuroendoscopic Surgery . 1st ed. New York, NY: Thieme; 2016. Google Scholar CrossRef Search ADS   5. Warf BC, Tracy S, Mugamba J. Long-term outcome for endoscopic third ventriculostomy alone or in combination with choroid plexus cauterization for congenital aqueductal stenosis in African infants. J Neurosurg Pediatr . 2012; 10( 2): 108- 111. Google Scholar CrossRef Search ADS PubMed  6. Rangel-Castilla L, Hwang SW, Jea A, Torres-Corzo J. Efficacy and safety of endoscopic transventricular lamina terminalis fenestration for hydrocephalus. Neurosurgery . 2012; 71( 2): 464- 473; discussion 473. Google Scholar CrossRef Search ADS PubMed  7. Ogiwara H, Morota N. Flexible endoscopy for management of intraventricular brain tumors in patients with small ventricles. J Neurosurg Pediatr . 2014; 14( 5): 490- 494. Google Scholar CrossRef Search ADS PubMed  8. Friedman GN, Grannan BL, Nahed BV, Codd PJ. Initial experience with high-definition camera-on-a-chip flexible endoscopy for intraventricular neurosurgery. World Neurosurg . 2015; 84( 6): 2053- 2058. Google Scholar CrossRef Search ADS PubMed  9. Antes S, Salah M, Linsler S, Tschan CA, Breuskin D, Oertel J. Aqueductal stenting with an intra-catheter endoscope—a technical note. Childs Nerv Syst . 2016; 32( 2): 359- 363. Google Scholar CrossRef Search ADS PubMed  10. Torres-Corzo J, Sanchez-Rodriguez J, Cervantes D et al.   Endoscopic transventricular transaqueductal Magendie and Luschka foraminoplasty for hydrocephalus. Neurosurgery . 2014; 74( 4): 426- 435. Google Scholar CrossRef Search ADS PubMed  11. Torres-Corzo J, Vinas-Rios JM, Sanchez-Aguilar M, Vecchia RR, Chalita-Williams JC, Rangel-Castilla L. Transventricular neuroendoscopic exploration and biopsy of the basal cisterns in patients with Basal meningitis and hydrocephalus. World Neurosurg . 2012; 77( 5-6): 762- 771. Google Scholar CrossRef Search ADS PubMed  12. Proano JV, Torres-Corzo J, Rodriguez-Della Vecchia R, Guizar-Sahagun G, Rangel-Castilla L. 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COMMENTS The authors provide a very interesting case report demonstrating the use of a flexible neuroendoscope with the assistance of stereotactic neuro-navigation. A navigation-compatible electromagnetic glidewire was inserted into the working channel of the endoscope. The major limitation of this technique is that the glidewire has to be removed in order to use other instruments through the endoscope, thus losing the stereotactic navigation until the wire is reinserted. The authors acknowledge this limitation and offer suggestions on the creation of an ideal future endoscope that would permit localization of the entire length of the endoscope throughout a procedure. The accompanying video and photographs provide a nice display of the views possible with the navigation-assisted flexible neuroendoscope via this glidewire method. Future developments in this field could permit expanded use of the neuroendoscope for more complex minimally invasive procedures. Carrie R. Muh Durham, North Carolina The authors present an exceptional video and description of a technique that will be useful to many surgeons practicing neuroendoscopy. Advances in technology facilitate expanded uses for the flexible endoscope. From the video, I can tell that the authors are extremely experienced and facile with the equipment. Beginning neuroendoscopists should not try to emulate this technique until they have achieved mastery of the basics. This is a very interesting demonstration and I look forward to the authors publishing more of their experience in the future. Daniel H. Fulkerson Indianapolis, Indiana The authors provide a well-written and well-illustrated technical report on the use of frameless stereotactic neuronavigation with the use of a flexible endoscope. The major source of complications in intraventricular endoscopic approaches is disorientation. Frameless stereotaxis may help to reduce disorientation, as suggested by the authors. However, neuronavigation systems, like the one used by the authors, that rely on a preoperative imaging dataset have decreasing accuracy during the surgical procedure. The reasons for this loss of accuracy are multifactorial. As an example, brain shift may occur from the loss of cerebrospinal fluid after cannulation of the ventricular system, decreasing the reliability of neuronavigation. I look forward to future studies from the authors that expand on their n of 1, and report on their experience with frameless stereotactic neuronavigation and flexible endoscopy, including their quantification and compensation for brain shift and inaccuracy of neuronavigation as the surgical procedure progresses. Andrew Jea Indianapolis, Indiana Copyright © 2017 by the Congress of Neurological Surgeons

Journal

Operative NeurosurgeryOxford University Press

Published: Mar 1, 2018

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