Frameless Stereotaxy Research Articles

Cystoperitoneal shunts for cystic vestibular schwannomas

We welcome the comments made by Dagain et al. in their letter of response to our article. In particular, we note the similarity of their approach to our own with regards to cystic vestibular schwannomas in elderly patients with significant comorbidities. We agree that cyst aspiration alone is unlikely to be sufficient and that a shunt will be required in most cases. In case 1 in our paper, intermittent reservoir aspirations did however allow us to gauge the clinical response to cyst drainage before proceeding to insertion of a distal catheter. Furthermore, we very much endorse the assertion that a valve-less system is required due to tumour fluid viscosity (in both the cases we described, a valve-less system was used with a reservoir for access). We note with interest the description of the patient in whom the solid tumour increased significantly after drainage of the cystic component. This reaffirms our opinion that patients treated with this method require interval clinical and radiological assessment. The emphasis placed on neuronavigation by Dagain et al. is very much in line with our clinical practice in this area: frameless stereotaxy was used in both of the cases described. Cystoperitoneal shunting for cystic vestibular schwannomas is an extremely useful technique in specific circumstances. We thank the authors for their remarks and we await the publication of their own series with interest.

Precision of navigated stereotactic probe implantation into the brainstem

The indications for stereotactic biopsies or implantation of probes for local chemotherapy in diffuse brainstem tumors have recently come under debate. The quality of performing these procedures significantly depends on the precision of the probes' placement in the brainstem. The authors evaluated the precision of brainstem probe positioning using a navigated frameless stereotactic system in an experimental setting. Using the VarioGuide stereotactic system, 33 probes were placed into a specially designed model filled with agarose. In a second experimental series, 8 anatomical specimens were implanted with a total of 32 catheters into the pontine brainstem using either a suboccipital or a precoronal entry point. Before intervention in both experimental settings, a thin-sliced CT scan for planning was obtained and fused to volumetric T1-weighted MR imaging data. After the probe positioning procedures, another CT scan and an MR image were obtained to compare the course of the catheters versus the planned trajectory. The deviation between the planned and the actual locations was measured to evaluate the precision of the navigated intervention. Using the VarioGuide system, mean total target deviations of 2.8 +/- 1.2 mm on CT scanning and 3.1 +/- 1.2 mm on MR imaging were detected with a mean catheter length of 151 +/- 6.1 mm in the agarose model. The catheter placement in the anatomical specimens revealed mean total deviations of 1.95 +/- 0.6 mm on CT scanning and 1.8 +/- 0.7 mm on MR imaging for the suboccipital approach and a mean catheter length of 59.5 +/- 4.1 mm. For the precoronal approach, deviations of 2.2 +/- 1.2 mm on CT scanning and 2.1 +/- 1.1 mm on MR imaging were measured (mean catheter length 85.9 +/- 4.7 mm). The system-based deviation of frameless stereotaxy using the VarioGuide system reveals good probe placement in deep-seated locations such as the brainstem. Therefore, the authors believe that the system can be accurately used to conduct biopsies and place probes in patients with brainstem lesions.

Tomotherapy for neurofibromatosis Type 2: case report and review of the literature

Neurofibromatosis 2 (NF2) results in multiple central nervous system tumours. In this case report, the patient has one vestibular schwannoma, one trigeminal schwannoma and two meningiomas developed before the age of 30. Aiming to treat three targets at one fraction with minimal interaction and overlapping doses to normal tissue, the sophisticated equipment of tomotherapy was utilised for frameless stereotaxy; tomotherapy delivered intensity-modulated, rotational radiation therapy using a fan-beam delivery. Daily CT scans with the inbuilt CT scanner were also performed as part of the image-guided radiotherapy. The course of fractionated stereotactic radiotherapy consisted of eight fractions given three times per week with an overall treatment time of 17 days. For the meningioma over left parietal vertex, 4.5 Gy per fraction was given at 36 Gy/8 Fr/17 days. For the meningioma over anterior cerebral falx, 4 Gy per fraction was given at 32 Gy/8 Fr/17 days. For the two schwannomas as one target, 5 Gy per fraction was given at 40 Gy/8 Fr/17 days. The acute effect of the treatment was alopecia and mild headache. Subsequent follow-up confirmed clinical improvement. This is the first reported case of clinical experience with tomotherapy in the management of NF2.

Image-guided multilevel vertebral osteotomies for en bloc resection of giant cell tumor of the thoracic spine: case report and description of operative technique

The use of frameless stereotactic navigation is gaining popularity in spinal surgery. Although initially used in the spine for placement of lumbar pedicle screws, this technology has expanded to facilitate placement of spinal instrumentation at virtually all spinal levels. While previous reports have described the utility of image guidance for placement of spinal instrumentation, its use in assisting with resection of complex spine tumors has not been extensively reported. Here we describe the use of frameless stereotaxy to guide a complex, four-level sagittal vertebral osteotomy for en bloc resection of a giant cell tumor involving the chest wall and thoracic spine.

CT-Based, Fiducial-Free Frameless Stereotaxy for Difficult Ventriculoperitoneal Shunt Insertion: Experience in 26 Consecutive Patients

Background:Patients with small or dysmorphic ventricles requiring ventriculoperitoneal shunt (VPS) insertion for hydrocephalus can be challenging. The ‘freehand’ technique does not always provide for accurate catheter insertion, particularly in patients with slit ventricles, complex hydrocephalus or displaced ventricles. Consequently, many surgeons use stereotaxy for assistance. We have employed a frameless stereotactic technique, obviating the need for fiducials or preoperative MRI, for difficult ventricular catheter placement over the past 1.5 years with excellent results. We describe our experience with frameless stereotactic VPS insertion. Methods:We retrospectively reviewed the charts of 26 patients who underwent frameless stereotactic VPS insertion. All patients had preoperative CT scans using a navigation protocol and were registered into the Stealth Station via the face tracer program. Catheters were inserted using the Medtronic frameless trajectory guide kit. We recorded demographic data, operative time, complications and follow-up. Results:The mean patient age was 31 years. The average operative time was 46 min. There were 3 complications. The average follow-up was 5 months. Twenty-one patients had postoperative imaging, with 20 having excellent catheter positioning. Conclusions:Our results confirm that frameless stereotactic VPS without fiducial marker placement is a feasible technique for catheter insertion in patients who have small/dysmorphic ventricles. In experienced hands, there is negligible added operative time and a low complication rate.

A modified stereotactic frame as an instrument holder for frameless stereotaxis: Technical note

Background:In order to improve the targeting capability and trajectory planning and provide a more secure probe-holding system, a simple method to use a stereotactic frame as an instrument holder for the frameless stereotactic system was devised.Methods:A modified stereotactic frame and BrainLab vector vision neuronavigation sys¬tem were used together. The patient was placed in the stereotactic head-holder to which a reference array of the neuronavigation system was attached. The pointer of the frameless system was placed in the probe-holder of the frame. An offset in distances was kept between the radius of the arch of the frame and the tip of the pointer so that the pointer was always outside the head during navigation. The offset correction was made on the BrainLab monitor so that the center of the arc of the frame was at the tip of the probe line on the monitor. Then, using the frame’s coordinate adjuster system, the center of the arc was positioned on the target. This method was used to insert depth electrodes (seven procedures) and gain access to the temporal horn (three procedures).Results:Post-operative scans showed that the accuracy was within 2.5 mm in all three planes for depth electrode placement, and easy access to the temporal horn was obtained in two other patients.Conclusion:This is a simple method to use a stereotactic frame to improve coordinate and trajectory adjustments and provides a better method to stabilize the pointer and the probe-holder during frameless stereotactic procedures.

A review of perioperative complications during frameless stereotactic surgery: our institutional experience

Frameless stereotactic neurosurgery is increasingly being used for the biopsy of intracranial tumors and the resection of deep-seated lesions where reliance on surface anatomic landmarks can be misleading, as well as in movement disorders, psychiatric disorders, seizure disorders, and chronic refractory pain. Nascent biological approaches, including gene therapy and stem-cell and tissue transplants for movement disorders, also utilize neuronavigational techniques. These procedures are complex and involve understanding of the basic principles and factors affecting neuronavigation. The procedure may appear to be simple, but serious complications may occur. The purpose of this study was to review the intraoperative and postoperative complications occurring during frameless stereotaxy at our institution from January 2003 to July 2007. Seventy-eight patients underwent various neurosurgical procedures under general anesthesia. Intraoperative complications seen were intraoperative brain bulge (n = 3), seizures (n = 3), failure to extubate (n = 4), and fresh neurodeficits (n = 6). No hemodynamic disturbances such as hypertension or hypotension or bradycardia or tachycardia requiring active intervention were observed. Awareness and vigilance can help in the early identification and better management of the above intraoperative complications.

Neuronavigation in the Minimally Invasive Presacral Approach for Lumbosacral Fusion

Intraoperative 3D navigation (3D NAV) is gaining importance in spinal surgery, especially with the advancement of minimally invasive techniques in this field. We hypothesized that 3D NAV may be of benefit in the recently described minimally invasive presacral approach for L4-S1 fusion (AxiaLIF). Five patients with refractory low back pain and L5-S1 degenerative disease underwent 3D NAV-assisted placement of a presacral L5-S1 screw. Additionally, a patient recently underwent a two-level AxiaLIF procedure (L4-S1) which was also performed with 3D NAV. Navigation was performed by acquiring intraoperative images via isocentric fluoroscopy and utilizing frameless stereotaxy. Accuracy of 3D NAV was confirmed by overlapping intraoperative images, navigation screenshots, and postoperative CT scans. Outcome was determined by pre- and postoperative VAS (back and leg pain) and ODI. Operative results were reviewed for all six patients and clinical outcomes were retrospectively reviewed for the five L5-S1 procedure patients. Postoperative imaging demonstrated accurate screw placement in comparison to intraoperative C-arm imaging and navigation imaging in all patients. No perioperative complications were encountered. In the five one-level patients, mean VAS (for back and leg pain) and ODI improved significantly at most recent follow-up. The minimally invasive presacral approach to L4-L5-S1 fusion can be performed safely and accurately with intraoperative 3D NAV. This is especially the case in two-level AxiaLIF procedures, where computer guidance can provide better planning possibilities for optimal screw trajectory.

Effect of high frequency repetitive transcranial magnetic stimulation on reaction time, clinical features and cognitive functions in patients with Parkinson’s disease

The aim of the present study was to investigate the effects of one session of high-frequency repetitive transcranial magnetic stimulation (rTMS) applied over the left dorsal premotor cortex (PMd) and left dorsolateral prefrontal cortex (DLPFC) on choice reaction time in a noise-compatibility task, and cognitive functions in patients with Parkinson's disease (PD). Clinical motor symptoms of PD were assessed as well. Ten patients with PD entered a randomized, placebo-controlled study with a crossover design. Each patient received 10 Hz stimulation over the left PMd and DLPFC (active stimulation sites) and the occipital cortex (OCC; a control stimulation site) in the OFF motor state, i.e. at least after 12 h of dopaminergic drugs withdrawal. Frameless stereotaxy was used to target the optimal position of the coil. For the evaluation of reaction time, we used a noise-compatibility paradigm. A short battery of neuropsychological tests was performed to evaluate executive functions, working memory, and psychomotor speed. Clinical assessment included a clinical motor evaluation using part III of the Unified Parkinson's Disease Rating Scale. Statistical analysis revealed no significant effect of rTMS applied over the left PMd and/or DLPFC in patients with PD in any of the measured parameters. In this study, we did not observe any effect of one session of high frequency rTMS applied over the left PMd and/or DLPFC on choice reaction time in a noise-compatibility task, cognitive functions, or motor features in patients with PD. rTMS applied over all three stimulated areas was well tolerated and safe in terms of the cognitive and motor effects.

Flexibility of Head Positioning and Head Fixation Provided by a Novel System for Non-invasive Maxillary Fixation and Frameless Stereotaxy: Technical Note

The aim of this study was to demonstrate the flexibility in patient positioning and head fixation provided by a newly developed, minimally invasive upper jaw fixation device in combination with standard navigation software. The Vogele-Bale-Hohner (VBH) headholder and the Stereotactic Intervention and Planning Laboratory (SIP-Lab) Innsbruck reference frame, were applied in epilepsy surgery requiring stereotactic guidance. The system can be adapted to various positioning and instrument guidance requirements. Instrument holders can be fixed either to a base plate or directly to the mouthpiece. When used together with a head clamp and a stabilizing arm, there are no restrictions on patient positioning. When used with the non-invasive headholder, only the supine position is well-suited for use with the described guidance instrumentation. The system can also be used with the head placed on the horseshoe headholder without altering navigation support. The VBH mouthpiece combined with an external registration frame is a flexible tool that permits patient positioning and neuronavigation with the head either fixed with a head clamp, or restrained non-invasively with a headholder, or not fixed at all. This might be advantageous within the context of epilepsy surgery.

VARIOGUIDE

VarioGuide (BrainLAB AG, Feldkirchen, Germany) is a new system for frameless image-guided stereotaxy. In the present study, we aimed to assess target point accuracy in a laboratory setting and the clinical feasibility of the system. Using the phantom of our frame-based stereotactic system (Riechert-Mundinger; Inomed Medizintechnik GmbH, Teningen, Germany), target points were approached from different angles with the frameless system. Target point deviation in the x, y, and z planes was assessed. Furthermore, patients harboring intracranial lesions were diagnostically biopsied using VarioGuide. Phantom-based accuracy measurements yielded a mean target point deviation of 0.7 mm. Between February 2007 and April 2008, 27 patients were diagnostically biopsied. Lesion volumes ranged from 0.2 to 117.6 cm3, trajectory length ranged from 25.3 to 64.1 mm, and the diagnostic yield was 93%. Concluding from the phantom measurements with ideal image-object registration, assumed spherical lesions with a volume of 0.524 cm can be biopsied with 100% target localization. Early clinical data revealed VarioGuide to be safe and accurate for lesions of 0.2 cm3 and larger. Thereby, the system seems feasible for the biopsy of most intracranial lesions.

Frame-based stereotaxy in a frameless era: current capabilities, relative role, and the positive- and negative predictive values of blood through the needle

In the modern era of frameless stereotaxis (FL), the role of frame-based (FB) stereotactic needle biopsy is evolving. Retrospective review of prospective database of 106 lesions in 91 consecutive patients undergoing FB stereotactic needle biopsy with a systematic "geologic core" technique by a single surgeon. Diagnostic accuracy was calculated comparing biopsy diagnosis with final pathology in 11 patients who underwent subsequent surgical resection. All instances of intra-operative bleeding through the needle were prospectively noted and compared with post-biopsy CT scan. Lesions were classified as risky for FL technique if they were (1) infratentorial or pineal, (2) within 10 mm of the circle of Willis or root of the Sylvian fissure, or (3) within 10 mm of deep cerebral veins. Diagnostic yield was 94%. Diagnostic accuracy was 91%. Of 18 lesions involving the corpus callosum, 13 (72.2%) were GBM 2 were anaplastic astrocytoma, and 1 each were found to be anaplastic oligodendroglioma, primary central nervous system lymphoma (PCNSL) and tumescent MS. Of 25 multifocal lesions, malignant primary brain tumor was diagnosed in 17 (68%) (11 GBM, 3 PCNSL, 2 anaplastic ologodendroglioma, and 1 anaplastic astrocytoma). Mortality was 0%. Three patients developed temporary neurologic deficits and one had permanent deficit. Absence of persistent blood through the biopsy needle had a negative predicative value of 98.8% for subsequent neuroimaging blood >5 mm diameter. According to our criteria, 80% of patients would have been candidates for FL biopsy. Stereotactic biopsy is an effective, safe and important technique for histologic diagnosis of brain lesions, particularly for multifocal and corpus callosum lesions. Post-biopsy CT can be safely reserved for patients who demonstrate persistent bleeding through the biopsy needle. FB stereotaxy remains an important technique for the 20% with small or deep seated lesions or when it is advantageous to avoid an incision, a burr hole or general anesthesia.

Quantitative Analysis of Surgical Exposure and Angle of Surgical Freedom Obtained by Endoscope and Microscope in Various Approaches to the Anterior Communicating Artery Complex Using CT-Based Frameless Stereotaxy

Introduction: Surgical treatment of aneurysms of the anterior communicating artery complex is challenging due to the intricate vascular anatomy. Endoscopy is a leading technique of minimally invasive neurosurgical procedures, and it could lend itself well to overcome some of the vascular visualization challenges associated with this procedure.

Quantitative Analysis of Surgical Exposure and Surgical Freedom Obtained by Endoscope and Microscope in the Endonasal Transsphenoidal Approaches to Sella Using CT-Based Frameless Stereotaxy: An Anatomical Study

Introduction: Among the most significant technical advances in cranial base surgery has been the introduction of the endonasal endoscopic techniques in the management of skull base lesions. The evolution and the changing role of the endoscope in pituitary and midline cranial base surgery attract significant attention from the neurosurgical community.

A Preliminary Study of fMRI-Guided rTMS in the Treatment of Generalized Anxiety Disorder

Article AbstractLetter to the Editor Sir: In our recent article, we investigated the effects of functional magnetic resonance imaging (fMRI)-guided repetitive transcranial magnetic stimulation (rTMS) treatment for symptoms of generalized anxiety disorder (GAD). We found that low-frequency rTMS treatment, administered with frameless stereotaxy on the basis of individual functional imaging data, significantly decreased anxiety symptoms associated with GAD. However, when the article was published, the duration of the rTMS effects beyond the 3-week treatment period was not known. The possibility of long-lasting treatment effects, as has been observed with short-term electroconvulsive therapy, could have significant clinical and economic implications for further utilization of rTMS for anxiety.

Endoscopic Treatment for Deep-seated or Multiple Intraparenchymal Tumors: Technical Note

Although endoscopic biopsy is a well-established technique in the treatment of intraventricular or cystic tumors, solid intraparenchymal tumors have not been considered candidates for this procedure. The purpose of this study is to describe strategies of neuroendoscopic treatment in patients with solid intraparenchymal tumors. Six patients with deep-seated or multiple intraparenchymal tumors underwent neuroendoscopic biopsy combined with frame-based or frameless stereotaxy during the one year period between October 2006 and September 2007. After histological diagnosis, all patients were treated with radiotherapy and chemotherapy or chemotherapy alone. Three patients were diagnosed histopathologically as having malignant glioma, and three with malignant lymphoma. A tumor was removed completely in one patient using an endoscopic procedure. Tumors disappeared in three patients with radiotherapy and chemotherapy after an endoscopic procedure. The growth of the tumor was controlled with therapy in one patient. Only in one patient was there a malignant transformation and growth of tumor was recognized in spite of therapy. Neuroendoscopic treatment may be a useful option in the management of deep-seated or multiple intraparenchymal tumors.

Localizing Broca's area for transcranial magnetic stimulation: Comparison of surface distance measurements and stereotaxic positioning

Precise placement of transcranial magnetic stimulation (TMS) coils over target regions is crucial for correct interpretation of TMS effects. Modern frameless stereotaxic systems yield high accuracy, but require extensive equipment and cannot be used in every setting, for example, during functional imaging sessions. The aim of this study was the development of a method for TMS-coil placement based on individual imaging data without the need for external tracking devices. We compared coil positioning over Broca's area using an advanced stereotaxic navigation system with placement according to the surface distance measurements (SDM) method. By using the SDM-method, 3-dimensional renderings adapted from individual T1-weighted magnetic resonance imaging (MRI) data were created to identify Broca's area and Broca's homologue, respectively, and to define anatomic landmarks on the skin's surface. Distances between these landmarks were used to localize the real target on the individual's head. The mean Euclidean distance between surface positions as determined with the two methods was 8.31 mm and the mean difference of estimated virtual electric field intensity at the target point was 7.37 V/m corresponding to 4.01% of maximum field strength. Our findings suggest that, compared with a state-of-the-art frameless stereotaxy system, the SDM-method yields a reasonable accuracy for positioning of a TMS-coil over Broca's area in terms of spatial coordinates.

Quantitative Analysis of Surgical Exposure and Angle of Surgical Freedom Obtained by Endoscope and Microscope in the Retrosigmoid and Various Posterior Petrosectomy Approaches to the Petroclival Region Using CT-Based Frameless Stereotaxy

Objective: Several approaches are used to expose the petroclival region and most of them require a certain degree of temporal bone resection with its associated approach morbidity, such as hearing and facial nerve compromise. To gain insight into the benefits of integration of endoscopy, we evaluated and compared the exposure obtained by endoscope and microscope in the retrosigmoid and the presigmoid approaches by quantitative analysis.

Quantitative Analysis of Surgical Exposure and Angle of Surgical Freedom Obtained by Endoscope and Microscope in Various Approaches to the Anterior Communicating Artery Complex Using CT-Based Frameless Stereotaxy

Quantitative Analysis of Surgical Exposure and Angle of Surgical Freedom Obtained by Endoscope and Microscope in Various Approaches to the Anterior Communicating Artery Complex Using CT-Based Frameless Stereotaxy

The Combined Use of CT-Based Frameless Stereotaxy and Endoscope for Exposure of IAC and Fundus with Preservation of Integrity of the Labyrinth

Hearing loss following removal of acoustic neuromas with preservation of the cochlear nerve may result from labyrinthine injury (posterior semicircular canal and/or common crus) during drilling of the posterior wall of the internal auditory meatus (IAC). Objectives: To investigate the usefulness of image guidance and endoscope for exposure of IAC and fundus in an effort to preserve the integrity of the labyrinth. Methods: A retrosigmoid approach to the IAC was performed on 10 whole fresh cadaveric heads after subjecting them to high-resolution CT scan (120 kV; slice thickness, 1mm; FOV, 40 cm; matrix, 512 × 512) with permanent bone fiducials. Drilling of the posterior wall of the internal acoustic canal was aided with image guidance .The most-lateral area of the IAC was exposed using the endoscope. Results: Target registration error for the procedure was 0.38 ± 0.18 mm.The measured length of the IAC along its posterior wall was 9.7 ± .1.6 mm. The angle of drilling (angle between the direction of drill and the posterior petrous surface) and the length of posterior wall of IAC drilled without violating the integrity of the labyrinth were 43.3 degrees ± 6 degrees and 7.2 ± 0.9 mm, respectively. The remaining part of the IAC and the fundus was exposed with the aid of the endoscope. Conclusion: Use of image guidance and endoscope can help in exposing the entire fundus without violating the labyrinth through a retrosigmoid approach, which can improve the hearing preservation in acoustic neuromas surgery.