Interactive image-guided neuroendoscopy: development and early clinical experience

The Role of Diffusion Tensor Imaging in Establishing the Proximity of Tumor Borders to Functional Brain Systems: Implications for Preoperative Risk Assessments and Postoperative Outcomes

Diffusion Tensor Imaging (DTI) is a new MRI imaging technique sensitive to directional movements of water molecules, induced by tissue barriers. This provides a new form of contrast that allows the identification of functional white matter tracts within the brain, and has been proposed as a technique suitable for presurgical planning in brain tumor patients. Resection of primary brain tumors improves survival, functional performance, and the effectiveness of adjuvant therapies, provided that surgically-induced neurological deficits can be avoided. Diffusion Tensor Imaging (DTI) has the potential to establish spatial relationships between eloquent white matter and tumor borders, provide information essential to preoperative planning, and improve the accuracy of surgical risk assessments preoperatively. We present our experience in a series of 28 brain tumor patients where the integration of functional magnetic resonance imaging (fMRI) and DTI data was used to determine key anatomic spatial relationships preoperatively. Twice as many functional systems were localized to within 5 mm of tumor borders when DTI and fMRI were utilized for preoperative planning, compared to that afforded by fMRI alone. Our results show that the combined use of fMRI and DTI can provide a better estimation of the proximity of tumor borders to eloquent brain systems sub-serving language, speech, vision, motor and premotor functions. Additionally, a low regional complication rate (4%) observed in our series suggests that preoperative planning with these combined techniques may improve surgical outcomes compared to that previously reported in the literature. Larger studies specifically designed to establish the accuracy and predictive value of DTI in brain tumor patients are warranted to substantiate our preliminary observations.

Neuronavigational neuroendoscopy--to be or not to be? An international pilot questionnaire-based study

OBJECTIVE

The almost age-old neuroendoscopy (NE) and neuronavigation (NN) in its twenties independently and indisputably have proved their high value as neurosurgical armamentarium and became even indispensable in some pathologies. However, nowadays the effectiveness of their simultaneous and combined application still is a matter of debate. The purpose of our pilot international, questionnaire-based survey was to assess the position of the opinion leaders in the field of neuroendoscopy worldwide toward the neuronavigational neuroendoscopy (NNNE).

METHODS

Within 3 months, a questionnaire with 17 questions was emailed repeatedly to 55 leading academic neuroendoscopic neurosurgeons from 50 institutions in 24 countries. The questionnaire covered aspects of personal and institutional experience in NE, NN, and NNNE, the most frequently treated pathologies by NNNE as well as inquiring the neurosurgeons' opinion for the importance and future of NNNE.

RESULTS

Forty-one questionnaires were returned (response rate = 74.6%). Six questionnaires were excluded because of incomplete or incorrect answers, leaving in the survey 35 respondents from 35 institutions in 18 countries. The less experienced neurosurgeons rely in higher degree on NNNE. Most frequently, NNNE is performed for hydrocephalus (procedures other than third ventriculostomy), transsphenoidal surgery, tumor biopsy, and cyst fenestration. Regardless their neurosurgical and NE experience, more than 75% of the respondents state that NNNE extends the range of neuroendoscopic procedures in their neurosurgical departments.

CONCLUSION

NNNE represents a valuable operative technique with excellent future prospects. NNNE extends the range of neuroendoscopic procedures, transforming some number of patients from "nonoperable" neuroendoscopically to suitable for neuroendoscopy.

The role of neuroendoscopy in the management of solid or solid-cystic intra- and periventricular tumours

OBJECTS

The purpose of this study was to describe the surgical strategies of neuroendoscopic treatment in patients with solid or solid-cystic peri- and intraventricular tumours. Analysis of the postoperative histopathology and complication of neuroendoscopic interventions was also performed.

BACKGROUND

A number of intracranial tumours do not ultimately require aggressive surgical intervention. Either definite or palliative treatment for the intra- and periventricular lesions could be accomplished using various neuroendoscopic techniques, depending on the histopathological diagnosis and aim of therapeutic intervention.

MATERIALS AND METHODS

Between 1994 and 2004, 46 patients with newly diagnosed solid or solid-cystic peri- and intraventricular tumours underwent neuroendoscopic procedures Twenty patients had associated hydrocephalus requiring the cerebrospinal fluid diversion procedures. Since 1997, neuronavigation has been applied to selected cases.

RESULTS

Obstructive hydrocephalus was treated sufficiently by endoscopic third ventriculostomy or endoscopic stent placement. Partial or total extirpation of solid tumour was achieved in four cases. The majority of pathological examinations revealed astrocytoma (23), craniopharygioma (7) and metastasis (2). Subsequent mode of treatment such as chemotherapy, radiation therapy or microscopic surgery was determined according to the pathological findings. There were three transient morbidities and one permanent deficit, but no operative mortality.

CONCLUSION

Transventricular endoscopic approach is an effective and reliable alternative treatment of newly diagnosed peri- and intraventricular lesions. Neuroendocopic procedures offer the opportunity to combine tumour biopsy and treatment of hydrocephalus. In selected patients, partial or total tumour removal could be performed.

Frameless, pinless stereotactic neurosurgery in children

OBJECT

Frameless neuronavigation has been established as a useful adjunct to intracranial surgery; however, the procedure is limited in young children by the need for rigid skull fixation with pins. Pin fixation is difficult and hazardous for patients younger than 2 years of age. Minor risks have been associated with pin fixation in older patients also, including scalp laceration, skull fracture, and epidural hematoma.

METHODS

The authors adapted a pinless head fixation system, consisting of a beanbag device, for use with frameless neuronavigation. This system was used to perform intracranial neurosurgical procedures in nine patients.

CONCLUSIONS

This pinless, frameless method provides a new option for children who are unable to sustain rigid head fixation. It is also an alternative to rigid pin fixation for patients of any age.

Intra-operative 3D ultrasound in neurosurgery

In recent years there has been a considerable improvement in the quality of ultrasound (US) imaging. The integration of 3D US with neuronavigation technology has created an efficient and inexpensive tool for intra-operative imaging in neurosurgery. In this review we present the technological background and an overview of the wide range of different applications. The technology has so far mostly been applied to improve surgery of tumours in brain tissue, but it has also been found to be useful in other procedures such as operations for cavernous haemangiomas, skull base tumours, syringomyelia, medulla tumours, aneurysms, AVMs and endoscopy guidance.

Intracranial navigation using a novel device for endoscope fixation and targeting: technical innovation

Intracranial endoscopy involves point-to-point navigation: first, in the introduction of the endoscope into a cerebrospinal fluid-containing space and, second, in the identification of a target structure. We report testing and preliminary clinical use of a device for the direct cranial fixation and point-to-point neuronavigation of a rigid ventricular endoscope. An 18-month-old female child presented with rapidly progressive macrocephaly, developmental delay and left hemiparesis. Neuroimaging revealed a large suprasellar cyst and obstructive hydrocephalus. We adapted a ball-stem device with an endoscopic working channel for direct cranial fixation over a burr hole. This device was successfully used in conjunction with MR-based neuronavigation to fenestrate the cyst. Seven months after the operation her developmental delay, macrocephaly and hemiparesis resolved. This device may be particularly effective in cases of small ventricles, ambiguous intra-ventricular landmarks, and in children too young for head-holder immobilization.

The evolution of stereotactic guidance in neuroendoscopy

OBJECTIVES

To evaluate the advantages and limitations of the utilized system in accordance with the operative indications of stereotactic neuroendoscopy.

PATIENTS AND METHODS

We reviewed our collective experience of computer-assisted stereotaxy (frame-based and frameless) and virtual endoscopy in neuroendoscopic surgery from 1982 to 2003. Sterotactic guiding systems (frame-based and frameless) have been used to perform more than 450 neuroendoscopic operations at our institute.

RESULTS

Even though image guidance is not essential in all cases, technological developments have definitely been one of the major factors in improving outcomes. Planning endoscopic trajectory and intraoperative orientation within the ventricular system or other cavities are the main indications for its application.

CONCLUSIONS

No surgical tool, no matter how accurate, can be a substitute for thoughtful and methodical pre-operative planning. Image-guided technologies are applied in order to make endoscopic surgery safer, faster and more easily reproducible. Despite the high initial cost of the equipment, overall expenses are expected to be reduced because of greater operative efficiency and shorter hospital stay.

Virtual Reality Neurosurgery: A Simulator Blueprint

OBJECTIVE

This article details preliminary studies undertaken to integrate the most relevant advancements across multiple disciplines in an effort to construct a highly realistic neurosurgical simulator based on a distributed computer architecture. Techniques based on modified computational modeling paradigms incorporating finite element analysis are presented, as are current and projected efforts directed toward the implementation of a novel bidirectional haptic device.

METHODS

Patient-specific data derived from noninvasive magnetic resonance imaging sequences are used to construct a computational model of the surgical region of interest. Magnetic resonance images of the brain may be coregistered with those obtained from magnetic resonance angiography, magnetic resonance venography, and diffusion tensor imaging to formulate models of varying anatomic complexity.

RESULTS

The majority of the computational burden is encountered in the presimulation reduction of the computational model and allows realization of the required threshold rates for the accurate and realistic representation of real-time visual animations.

CONCLUSION

Intracranial neurosurgical procedures offer an ideal testing site for the development of a totally immersive virtual reality surgical simulator when compared with the simulations required in other surgical subspecialties. The material properties of the brain as well as the typically small volumes of tissue exposed in the surgical field, coupled with techniques and strategies to minimize computational demands, provide unique opportunities for the development of such a simulator. Incorporation of real-time haptic and visual feedback is approached here and likely will be accomplished soon.

Computer-aided navigation in neurosurgery

The article comprises three main parts: a historical review on navigation, the mathematical basics for calculation and the clinical applications of navigation devices. Main historical steps are described from the first idea till the realisation of the frame-based and frameless navigation devices including robots. In particular the idea of robots can be traced back to the Iliad of Homer, the first testimony of European literature over 2500 years ago. In the second part the mathematical calculation of the mapping between the navigation and the image space is demonstrated, including different registration modalities and error estimations. The error of the navigation has to be divided into the technical error of the device calculating its own position in space, the registration error due to inaccuracies in the calculation of the transformation matrix between the navigation and the image space, and the application error caused additionally by anatomical shift of the brain structures during operation. In the third part the main clinical fields of application in modern neurosurgery are demonstrated, such as localisation of small intracranial lesions, skull-base surgery, intracerebral biopsies, intracranial endoscopy, functional neurosurgery and spinal navigation. At the end of the article some possible objections to navigation-aided surgery are discussed.

Endoscopic assisted microneurosurgery for cerebral aneurysms

While there have been many advances in the field of microneurosurgery, the clipping of aneurysms remains an intricate procedure. Technical complications include residual aneurysm, perforator injuries, parent artery occlusion and cranial nerve injuries. The neuroendoscope is a useful tool and adjunct to the microsurgical clipping of these aneurysms. We study the usefulness of the neuroendoscope in enhancing visualisation during surgery. Twenty-four cases of ruptured cerebral aneurysms were operated on over a duration of 6 months in which a 1mm diameter rigid endoscope was used. We discuss our preliminary results and examine the advantages of the neuroendoscope. These include the ability to look around corners and behind obstructions. While this provides an additional view to the surgeon, the high magnification gives good definition of the surrounding structures. With less brain retraction, smaller operative exposures and yet better visualisation offered, neuroendoscopy may reduce operative morbidity.

Complications of endoscopic third ventriculostomy

OBJECT

The purpose of this prospective investigation was to determine the rate of complications associated with endoscopic third ventriculostomy (ETV).

METHODS

Between March 1993 and October 2001, 193 ETVs were performed in 188 patients at a single institution. The age of the patients ranged from 1 month to 85 years (mean age 39 years). One procedure had to be abandoned because a severe venous hemorrhage blurred the surgeon's view; however, third ventriculostomy was successfully accomplished in that patient 14 days later. In addition, there were two cases in which significant venous hemorrhages could be controlled endoscopically by using irrigation. Postoperative imaging revealed three subdural collections, one tiny thalamic contusion, one cortical hemorrhage at the puncture site, and one severe subarachnoid hemorrhage (SAH). There were two deaths (1% mortality rate) related to the endoscopic procedure; causes of death were one SAH from a torn basilar perforating artery and one wound infection leading to meningitis and septic multiorgan failure. Three permanent deficits occurred (confusion, oculomotor palsy, and diabetes insipidus [1.6% permanent morbidity rate]). Transient deficits included four cases of meningitis, three cases of cerebrospinal fluid leak, two cases of herniation syndrome, two cases of confusion, one case in which there was a decrease of consciousness, two cases of oculomotor palsy, and one case in which there was loss of thirst (7.8% transient morbidity rate). Misplacement of the fenestration was the main reason for severe complications. During the course of the study, the complication rate dropped significantly (no incidences of mortality or permanent morbidity occurred during the last 100 procedures).

CONCLUSIONS

All permanent and fatal complications occurred during the authors' very early experience, indicating that a steep learning curve was associated with the procedure. Endoscopic third ventriculostomy, if performed correctly, is a safe, simple, and effective treatment option for various forms of noncommunicating hydrocephalus.

Interventional MR-guided neuroendoscopy: A new therapeutic option for children

Neuroendoscopic treatment of hydrocephalic children is an established surgical modality. Open magnetic resonance imaging (MRI) technology introduces new imaging features that, in combination with endoscopy, seem particularly valuable for performing these operations. "Near" real-time production of MR images in 3 dimensions during the procedure allows real-time neuronavigation, thus, facilitating guidance of an endoscope. Additionally, intraoperative changes such as brain shift, effects of perforation, and drainage of cysts are shown during an ongoing procedure. The patency of cysts or fluid compartments inside the ventricular system can be controlled by intraoperative injection of diluted gadolinium into the cystic compartments. These new therapeutic options were applied in 2 hydrocephalic children with complex ventricular cysts: a 3-month-old girl with a large, septated arachnoidal cyst and internal hydrocephalus and a boy of 7 years, 2 months with congenital hydrocephalus and premature closure of the coronary sutures.

A new method of ultrasonic guidance of neuroendoscopic procedures. Technical note

The authors present a newly designed device for ultrasonic guidance of neuroendoscopic procedures. It consists of a puncture adapter that attaches to a rigid endoscope having an outer diameter of 6 mm and is mounted on a small, bayonet-shaped ultrasound probe. This adapter directs the movement of the endoscope precisely within the ultrasonic field of view. The targeted region is identified by transdural insonation via an enlarged single burr-hole approach, and the endoscope is tracked in real time throughout its approach to the target. The procedure has been performed in 10 patients: endoscopic ventriculocystostomy in four cases; removal of a colloid cyst of the third ventricle in two cases; and intraventricular tumor biopsy, intraventricular tumor resection, third ventriculostomy, and removal of an intraventricular hematoma in one case each. The endoscope was depicted on ultrasonograms as a hyperechoic line without disturbing echoes and, consequently, the target (cyst, ventricle, or tumor) was safely identified in all but one case, in which intraventricular air hid a colloid cyst in the foramen of Monro. The method presented by the authors proved to be very effective in the guidance and control of neuroendoscopic procedures. Combining this method with image guidance is recommended to define the entry point of the endoscope precisely.

Frameless neuronavigation in intracranial endoscopic neurosurgery

OBJECT

Frameless computerized neuronavigation has been increasingly used in intracranial endoscopic neurosurgery. However, clear indications for the application of neuronavigation in neuroendoscopy have not yet been defined. The purpose of this study was to determine in which intracranial neuroendoscopic procedures frameless neuronavigation is necessary and really beneficial compared with a free-hand endoscopic approach.

METHODS

A frameless infrared-based computerized neuronavigation system was used in 44 patients who underwent intracranial endoscopic procedures, including 13 third ventriculostomies, nine aqueductoplasties, eight intraventricular tumor biopsy procedures or resections, six cystocistemostomies in arachnoid cysts, five colloid cyst removals, four septostomies in multiloculated hydrocephalus, four cystoventriculostomies in intraparenchymal cysts, two aqueductal stent placements, and fenestration of one pineal cyst and one cavum veli interpositi. All interventions were successfully accomplished. In all procedures, the navigational system guided the surgeons precisely to the target. Navigational tracking was helpful in entering small ventricles, in approaching the posterior third ventricle when the foramen of Monro was narrow, and in selecting the best approach to colloid cysts. Neuronavigation was essential in some cystic lesions lacking clear landmarks, such as intraparenchymal cysts or multiloculated hydrocephalus. Neuronavigation was not necessary in standard third ventriculostomies, tumor biopsy procedures, and large sylvian arachnoid cysts, or for approaching the posterior third ventricle when the foramen of Monro was enlarged.

CONCLUSIONS

Frameless neuronavigation has proven to be accurate, reliable, and extremely useful in selected intracranial neuroendoscopic procedures. Image-guided neuroendoscopy improved the accuracy of the endoscopic approach and minimized brain trauma.