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. Author manuscript; available in PMC: 2018 Jun 1.
Published in final edited form as: Interdiscip Neurosurg. 2017 Jun;8:17–22. doi: 10.1016/j.inat.2017.01.003

Three-Dimensional, computer simulated navigation in endoscopic neurosurgery

Roberta K Sefcik 1, Jonathan Rasouli 1, Joshua B Bederson 1, Raj K Shrivastava 1
PMCID: PMC5402761  NIHMSID: NIHMS847370  PMID: 28451520

Abstract

BACKGROUND

In order to address the pre- and perioperative need for visualization and prediction of patient-specific anatomy for surgical planning, endoscopic neurosurgeons have increasingly relied on computerized navigation devices to guide their surgical approaches.

OBJECTIVE

This manuscript aims to review: 1) the use of neuronavigation in endoscopic neurosurgery for pre-operative planning, 2) the intraoperative advantages of neuronavigation in endoscopic neurosurgery, and 3) the effects of navigation guidance on operative time, registration accuracy, brain shift, and avoidance of complications. Limitations of the current neuroendoscopic navigation literature will be discussed.

METHODS

We conducted a search using PubMed-MEDLINE; the keywords “stereotactic navigation AND endoscopic surgery” and “simulation AND endoscopic neurosurgery”. 36 studies were identified that addressed the use of neuronavigation in endoscopic neurosurgery. These studies were then further analyzed for topics relevant to computerized neuroendoscopy and reviewed for the purposes of this article.

CONCLUSION

Three-dimensional, frameless neuronavigation systems are useful in endoscopic neurosurgery to assist in the pre-operative planning of potential trajectories and to help localize the pathology of interest. Neuronavigation appears to be accurate to < 1–2 mm without issues related to brain shift. Further work is necessary in the investigation of the effect of neuronavigation on operative time, cost, and patient-centered outcomes.

Keywords: Endoscopic, stereotactic navigation, neuronavigation, frameless, image-guided

Introduction

A recurrent problem faced by endoscopic neurosurgeons is the ability to visualize and predict the location of important anatomic structures in a relatively small working environment. In endoscopic trans-sphenoidal surgery of the pituitary gland, the ability to predict the location of the carotid artery behind the sphenoid bone is paramount to prevent accidental vascular injury. In re-operative cases, normal anatomy can be distorted and the risk of iatrogenic complications can significantly increase.1 To address these potential pitfalls, endoscopic neurosurgeons have increasingly relied on computerized navigation devices to guide their surgical approaches. There are several navigation systems currently available on the market such as the Brainlab Curve (AG, Feldkirchen, Germany) and Medtronic StealthStation S7 (Medtronic, Minneapolis, MN).2 This manuscript aims to review the use of three-dimensional (3D) computerized neuronavigation systems in endoscopic neurosurgery for pre-operative planning and several of its key intraoperative advantages through discussion of an illustrative case of odontoidectomy with intraoperative neuronavigation. In addition, the effects of navigation guidance in regards to operative time, registration accuracy, brain shift, and complications will be discussed. Finally, the limitations of the current neuronavigation in neuroendoscopy literature will be discussed.

Illustrative Case: Navigation Guidance in Endoscopic Odontoidectomy

Navigation guidance has been utilized in endoscopic odontoidectomy.3–5 We report the case of a 49-year-old woman who initially presented complaining of severe frontal tussive headaches accompanied by imbalance, dizziness, nausea, and perioral and lingual numbness for the previous seven months. At the time, the patient’s exam was normal with the exception of bilateral fine beating nystagmus noted upon sustained horizontal gaze. MRI of the brain and cervical spine revealed a type I Chiari malformation with downward tonsilar displacement of 12 mm, no associated syrinx, and right-sided foraminal stenosis secondary to bulging discs at the cervical level (C) 3/4, and C 4/5 (Figure 1). Given the unremitting symptomatology with medical therapy, the patient underwent a decompressive suboccipital craniectomy and laminectomy of C1 with an uneventful post-operative course.

Figure 1. Pre-operative MRI of the brain and cervical spine.

Figure 1

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(A) Pre-operative sagittal and axial T2-weighted magnetic resonance imaging scans demonstrating a Type I Chiari Malformation with associated basilar invagination. (B) There is ventral and dorsal medullary compression by the odontoid process and cerebellar tonsils, respectively.

Six weeks post-operatively, the patient presented with a recurrence of the tussive frontal headache exacerbated with flexion of the head, neck pain with radiation to the shoulders bilaterally, dizziness, imbalance, dysmetria, ataxia, paresthesias of the upper and lower extremities, and difficulty with ambulation and dexterity. Physical examination revealed a wide-based gait with the inability to toe or heel walk or maintain a tandem gait, diffuse weakness and hyperactive reflexes throughout, and diminished sensation following a stocking glove distribution. As shown in Figure 1, MRI of the brain and cervical spine revealed a ventral cervicomedullary junction deformity, an acute angle between the dens and the clivus, and stable cerebellar ectopia. Due to the interval development of symptoms suggestive of cervical myelopathy and findings on MRI, the patient underwent a staged endoscopic transnasal odontoidectomy followed by occipitocervical fusion. The interval development of symptomatic atlanto-axial instability was likely exacerbated by the initial decompression. However, it is unclear if the patient had pre-existing instability before surgery. Unfortunately, pre-operative flexion/extension imaging of the cervical spine was not available.

As demonstrated in Figures 2–4, stereotactic neuronavigation (Brainlab AG, Feldkirchen, Germany and Surgical Theatre, LLC, Mayfield Village, OH) was essential in the determination of the operative approach (transnasal versus transoral), and navigation was used throughout the case with excellent accuracy. Based on the results of imaging, a trans-nasal entry point was selected instead of a trans-oral approach. The reason was due to a tortuous left carotid artery that was directly anterior to the C2 vertebral body. A trans-oral approach may have increased the risk of accidental carotid injury given the angle of approach; therefore a slight more superior trajectory angle was selected (trans-nasal). An extradural odontoid, C1 process, and basilar invagination resection was performed using a transclival C1 approach. Following drilling of the inferior clivus, the underlying tectorial membrane and dura were identified. The anterior tubercle of C1 was drilled until the identification of C2, and the angulation of C2 was shaped to an anterior angulation. The odontoid process was drilled using an eggshell technique. A 30-degree endoscope in combination with intraoperative navigation was used to identify decompression of the spinal cord, as pictured in Figure 5. Occipitocervical fusion occurred 4 days post-operatively, as demonstrated in Figure 6, and the patient was discharged after an uneventful post-operative course 8 days following the first operation. The patient’s post-operative course remained unremarkable and her myelopathic symptoms were steadily improving.

Figure 2. 3D-reconstructed pre-operative images displayed by the Surgical Theatre™ planning station (Surgical Theatre, LLC, Mayfield Village, OH).

Figure 2

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(A) (blue asterix) A tortuous left internal carotid artery is seen directly anterior to the C2 vertebral body and odontoid process. (B) A stereotactic registration wand was used to plan the surgical approach (maroon asterix). Based on this imaging, a trans-nasal approach was selected given the location of the left internal carotid artery.

Figure 4. 3D-reconstructed coronal view demonstrating a “probe’s eye” view through the nasal septum.

Figure 4

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The anterior face of C1-2 is seen in the center of the circle (blue asterix).

Figure 5. Comparison of pre-operative trajectory planning and resultant post-operative decompression.

Figure 5

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(A) Sagittal T1-weighted MRI demonstrating the surgical approach (endoscopic trans-nasal, red arrow). (B) Post-operative T1-weighted MRI demonstrating resection of anterior arch of C1 and odontoid process (blue asterix). There is less ventral compression of the medulla and craniocervical junction. (C) Post-operative midline sagittal CT scan demonstrating resection of the anterior and posterior arch of C1 and the odontoid process (blue asterix). (D) Coronal CT view demonstrating satisfactory resection of the odontoid tip (blue asterix).

Figure 6. Post-operative lateral flexion-extension cervical x-rays.

Figure 6

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Post-operative lateral flexion-extension cervical x-rays after occiput-C4 instrumentation and fusion demonstrating dynamic stability and preservation of cervical lordosis.

In this case study, stereotactic neuronavigation was crucial for pre-operative trajectory planning (transnasal versus transoral) and intraoperative navigation. This patient experienced no adverse events and improved post-operatively. This informative case adds to the growing literature in navigation-assisted endoscopic odontoidectomy, demonstrating the safe and effective use of neuronavigation for pre-operative planning and intraoperative navigation in endoscopic odontoidectomy.

Methods

A review of the available literature utilizing PubMed/MEDLINE and the following search terms: “stereotactic navigation AND endoscopic surgery” and “simulation AND endoscopic neurosurgery” was performed. The former resulted in 63 total results, 49 of which were related to the research question by title, and the latter resulted in 82 total results, 60 of which were related to the research question by title. The abstract and the methods section of each related manuscript were reviewed. Manuscripts that were not related to navigation in endoscopic neurosurgery or were performed solely in cadavers were excluded. All of the remaining 36 studies were reviewed in their entirety.

Results

The Current State of Navigation Guidance in Endoscopic Neurosurgery

Navigation and Pre-Operative Planning

There is substantial evidence to support the utility of neuronavigation in preoperative planning of burr hole placement6–9 and trajectory selection2,6–12 in a variety of neurosurgical cases, including third ventriculostomy,2,6,12,13 brain biopsy,9 colloid cyst aspiration,8,13 and arachnoid cyst fenestration2 (Table 1). Based on these studies, it appears that stereotactic navigation may be most useful for entrance site selection and pre-selection of trajectories in cases using multiple entry sites,7 and in endoscopic colloid cyst surgery due to the variability of the optimal entry point.8 In surgeries demonstrating an advantage for stereotactic navigation in pre-operative planning, neuronavigation was of less utility intra-operatively.11 For example, when optic navigation was performed in combination with continuous navigation of the endoscope, this resulted in a difficulty in establishing a line-of-sight.2 Overall, the review of more than 244 cases employing stereotactic navigation demonstrated pre-operative advantages for using neuronavigation in target localization,14 surgical access,6–940 and trajectory planning compared to conventional localization methods.2,6–12

Table 1.

Pre-operative planning: Advantages of computer-assisted navigation in endoscopic neurosurgery

Author & Year Number ofPatients Procedure Advantages
Rhoten et al., 19976 11 Ventricular fenestration, shunting, third ventriculostomy Entry site and trajectory planning
Target localization
Grunert et al., 199820 11 . Trajectory planning
Matula et al., 199814 5 . Target localization
Rohde et al., 199812 12 Third ventriculostomy, cystoventriculostomy, ventriculoatrial shunt, cystoperitoneal shunt, intracranial cysts Trajectory planning
Burtscher et al., 200311 5 Third ventriculostomy and fenestration Trajectory planning
Fixed suction mouthpiece for pre-operative planning without patient present
Souweidane et al., 200813 4 Colloid cyst aspiration, third ventriculostomy Access optimization
Leonardo et al., 20097 44* Ventricular access via catheter tracking Entry site and trajectory planning in cases with multiple entry points
Tanei et al., 20129 6 Parenchymal biopsy Entry point and trajectory planning
Target localization
Mert et al., 20132 52 Transphenoidal procedures, third ventriculostomy, cyst puncture Trajectory planning
Rangel-Castilla et al., 20148 39 Colloid cyst resection Trajectory and entry site planning
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*

Navigation was variably employed

Intraoperative Advantages of Navigation Guidance

In addition to the pre-operative advantages of navigation guidance in surgical planning, neuronavigation has been shown to have many advantages during surgery, including anatomical identification of key structures2,5,15 and real-time intraoperative guidance6,12,16 (Table 2). Neuronavigation allows for the real-time, accurate intraoperative sampling of multiple lesions using a single burr hole16 and intraparenchymal tumor resection due to the difficulty of externally visualizing anatomic landmarks.12,16,17 Neuronavigation is limited in its ability to display the sella’s relationship to surrounding anatomy and the sphenoid sinus’ contours when compared to 3D reconstructions.18 The use of neuronavigation may also impact the extent of tumor resection,19 with a meta-analysis demonstrating an association between navigation and either near-complete or complete tumor resection (p<0.0003),20 and an additional report of higher resection volumes in endoscopic biopsy when compared to open or stereotactic biopsies (p<0.05).21 Further investigation is still needed into the effect of intraoperative navigation on the avoidance of injury, with very limited reporting on safety outcomes at present.22,23

Table 2.

Intraoperative navigation: Advantages of computer-assisted navigation in endoscopic neurosurgery

Author & Year Number of Patients Procedure Major Findings
Rhoten et al., 19976 11 Ventricular fenestration, shunting, third ventriculostomy Navigation of the ventricles
Matula et al., 199814 5 . Possible time-saving effect
Rohde et al., 199812 12 Third ventriculostomy, cystoventriculostomy, ventriculoatrial shunt, cystoperitoneal shunt, intracranial cysts Intraoperative navigation
Kuroki et al., 200223 92 Pituitary surgery Possible effects on time-saving and increased safety
Burtscher et al., 200311 5 Third ventriculostomy and fenestration Possible time-saving effect
Dubin et al., 200515 Dacryocystorhinostomy and optic and orbital nerve decompression Anatomical identification
Akai et al., 200817 3 Astrocytoma and lymphoma resection/biopsy, radiation necrosis Navigating the brain parenchyma
Leng et al., 20095 1 Endonasal cervicomedullary junction decompression Vascular localization Possible time-saving effect
Conley et al., 201119 4 Maxillary sinusitis-dentigerous cyst, orbital osteoma, clival lesion, stenosis of the frontal recess Complete or good resection
Tsuda et al., 201121 9 Tumor biopsy Increased resection volume
Possible time-saving effect over open procedures
Barber et al., 201320 . Tumor resection Complete or near-complete resection
Constantini et al., 201329 45 Biopsy Diagnostic rate similar in cases with and without navigation in a review
Mert et al., 20132 52 Transphenoidal procedures, third ventriculostomy, cyst puncture Anatomic orientation
Nagahisa et al., 201316 21 Intraparenchymal biopsies Navigation of the brain parenchyma
Sampling of multiple lesions using one burr hole
Ali et al., 201522 3 Endonasal dacryolocalization for nasolacrimal drainage obstructions Avoiding injury
Inoue et al., 201518 99 Transphenoidal pituitary surgery Navigation inferior to 3D reconstructions in anatomic presentation
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Effect of Neuronavigation on Operative Time

There is clinical equipoise regarding the effect of neuronavigation on the operative duration of endoscopic procedures. The possibility of a timesaving effect has previously been reported,5,11,14,23 and Tsuda et al. included a statistical analysis showing a timesaving effect, with the procedure duration of open biopsy of 4.4 hours, endoscopic biopsy 2.2 hours, and stereotactic biopsy 1 hour (p<0.01).21 Further investigations into the effect of stereotactic navigation on procedure duration with statistical analysis powered to detect differences in operative time are necessary, as shorter operative times could translate to substantial cost savings.

Accuracy of Neuronavigation and Brain Shift

In order to optimize safety during endoscopic neurosurgery, navigation guidance requires highly accurate registration. Of the reviewed studies,4,12,14,21,24–26 the most accurate target registration had a minimum error of 0.8 mm and mean error of 1.2 mm.4 Registration accuracy was found to be study-dependent, with toleration of inaccuracies up to 3.5 mm reported.12 There was no difference between endoscopic biopsies that employed navigation versus open or stereotactic biopsies with navigation, but there was a trend toward higher accuracy in neuroendoscopy, warranting further investigation with an appropriately powered study.21 Brain shift did not present a problem for intraoperative accuracy in the studies included in this review11,27,28 (Table 3).

Table 3.

Accuracy achieved in studies employing computer-assisted navigation in endoscopic neurosurgery

Author & Year Number of Patients Procedure Major Findings
Gunkel et al., 199725 11 . 1–2 mm accuracy
Matula et al., 199814 5 . 2 mm error but not separated from microscopic cases
Rohde et al., 199812 12 Third ventriculostomy, cystoventriculostomy, ventriculoatrial shunt, cystoperitoneal shunt, intracranial cysts 3.5 mm accuracy
Gumprecht et al., 200028 5 Ventriculostomy, arachnoid cyst removal, partial astrocytoma resection, colloid cyst removal No problems with brain shift
Krombach et al., 200227 23 Hydrocephalus, intracranial cysts No problems with brain shift
Burtscher et al., 200311 5 Third ventriculostomy and fenestration No problems with brain shift
Bumm et al., 200526 10 Paranasal anterior sphenoid wall resection, frontal sinus ostium opening and enlargement, frontal and ethmoid sinus tissue biopsy Similar accuracy to paranasal sinus surgery
Monin et al., 200524 1 Optic nerve sheath venous hemangioma resection 1.7 mm accuracy
Tsuda et al., 201121 9 Tumor biopsy Trend toward higher accuracy of aim for the target
Choudhri et al., 20144 5 Odontoidectomy 1.2 mm mean error rate
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Complications of Neuronavigation in Neuroendoscopy

Endoscopic neurosurgery employing neuronavigation is not without complications, and navigation guidance has not been shown to reduce adverse event rates in neuroendoscopy.20,29 Investigators have faced many challenges in endoscopic neurosurgery, especially in the ability to address intraoperative hemorrhage,17 and the intraoperative advantages of neuronavigation do not address the problem of hemostasis. Inaccuracies in neuronavigation could lead to safety problems, as the toleration of registration errors of up to 3 mm12 could potentially result in accidental vascular injury. The operation of neuronavigation is also prone to human error, with the inadvertent resection of normal brain tissue during tumor resection due to accidental powering off of equipment a possibility.

Applications in Pediatric Neurosurgery

Navigation guidance in endoscopic neurosurgery has not been limited to utilization in the adult population; however, the application of neuronavigation in pediatric neurosurgery is limited by the use of invasive head holders. A technique in which a suction mouthpiece replaces the invasive head holder used in adult operations has been successfully employed in a 20-month-old patient.11 Frameless neuronavigation has been reported in operations for hydrocephalus in patients as young as 6-weeks-old.30

Discussion

Limitations of the Current Literature

The literature on navigation in neuroendoscopy and endoscopic sinus surgery is restricted by the lack of statistical analyses, small patient cohorts, and limited description of the effects of navigation in endoscopic procedures.15,31–33 For example, investigators have explored the effect of navigation guidance on skin incision location, soft tissue dissection, surgical orientation, and operative duration during craniotomy, but the same level of detailed description does not exist in neuroendoscopy.34 At times, the reporting of neuroendoscopic procedures using navigation guidance were not separate from microscopic and open procedures, limiting the ability to draw neuroendoscopic-specific conclusions.35 In order to draw strong conclusions about the clinical utility of navigation guidance in neuroendoscopy, further investigation with pre-planned hypotheses and analyses specific to neuroendoscopic cases are needed. In addition, studies ought to explore the effects of navigation-assisted neuroendoscopy on cost and patient-centered outcomes, including post-operative recovery and patient satisfaction.

Conclusion

This manuscript reviewed the use of neuronavigation in endoscopic neurosurgery for pre-operative planning of trajectories2,6–12 and entrance site6–9 and localization of the pathology of interest.6,9 Furthermore, the intraoperative advantages of neuronavigation in anatomic localization or orientation were discussed.2,5,12,15–17 Neuronavigation in endoscopic surgery was highly accurate,4 and brain shift did not present a problem for the studies included in this review.11,27,28 Further work is necessary in the investigation of the effect of neuronavigation on operative time, cost, and patient-centered outcomes.

Figure 3. Pre-operative surgical planning using 3D reconstructions rendered by Surgical Theatre™ (Surgical Theatre, LLC, Mayfield Village, OH).

Figure 3

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(A) In this coronal view, the vertebrobasilar junction is seen in relation to the clivus (blue asterix). (B) In this sagittal view, multiple trans-nasal trajectories are projected. The final intraoperative trajectory is displayed (red arrow).

Highlights.

  • Pre-operative trajectory planning is optimized with neuronavigation

  • Neuronavigation aids in localizing intraoperative pathology

  • Neuronavigation may be accurate to < 1–2 mm with no brain shift-related problems

Acknowledgments

RKS was supported in part by the National Center for Advancing Translational Sciences of the National Institutes of Health under Award Number TL1TR001434.

Financial Support: None

Abbreviations

3D

Three-dimensional

C

cervical level

Footnotes

Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Disclosures: JBB is a consultant for and owns shares in Surgical Theater, LLC.

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