Category: Neuronavigation

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O-Arm–Guided Balloon Kyphoplasty: Prospective Single-Center Case Series of 54 Consecutive Patients

Neurosurgery 68[ONS Suppl 2]:ons250–ons256, 2011 DOI: 10.1227/NEU.0b013e31821421b9

Balloon kyphoplasty is widely used to treat vertebral compression fractures. Procedure outcome and safety are directly linked to precise radiological imaging requiring 1 or 2 C arms to allow correct visualization throughout the procedure. This minimally invasive spinal surgery is associated with radiation exposure for both patient and surgeon. In our center, we switched from using a C-arm to an O-arm image guidance system to perform balloon kyphoplasty. Our preliminary experience is reported in Acta Neurochirurgica, and the encouraging results led us to study this subject more extensively. This article presents our complete results. To the best of our knowledge, there is no comparable clinical series describing O-arm use in kyphoplasty procedures published in the literature. OBJECTIVE: To report our complete results of using the O-arm guidance system to perform balloon kyphoplasty.

METHODS: We prospectively evaluated O-arm–guided kyphoplasty procedure in 54 consecutive patients and measured x-ray exposure and fluoroscopy time.

RESULTS: The mean surgical time for the procedure was 38 minutes with a mean fluoroscopy procedure time of 3.1 minutes. The mean fluoroscopy time by level was 2.5 minutes. Mean irradiation dose by procedure was 220 mGy and by level was 166 mGy. There was a significant reduction in fluoroscopy time and x-ray exposure from 5.1 minutes with classic C-arm use to 3.1 minutes when with O-arm use without additional time required for positioning the system.

CONCLUSION: With this new intraoperative system, the overall surgical and fluoroscopy times can be further reduced in the near future.

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Optic Radiation Fiber Tracking Using Anteriorly Angulated Diffusion Tensor Imaging: A Tested Algorithm for Quick Application

Neurosurgery 68:1239–1251, 2011 DOI: 10.1227/NEU.0b013e31820b52e1

Fiber tracking (FT) of the optic pathways (OPs) is difficult because there is no standard for the parameters of diffusion tensor imaging (DTI), placement of seed volumes, or interpreting the results.

OBJECTIVE: To determine optimal conditions and parameters for DTI and FT of the optic radiation under intraoperative conditions, we performed a multivariate prospective study.

METHODS: A healthy man underwent magnetic resonance imaging and DTI scans using various scan parameters. The slice thicknesses were 2.7 mm, 5 mm, and 7 mm, and the gantry of the slices was 0 degrees and 44 degrees. The OPs were tracked using different settings for focal anisotropy and minimal length of the visualized fibers. The time needed for DTI, image processing, and uploading as well as the difficulty of depicting the OPs, the time needed for FT, quality, and volume of the tracked fiber object were registered and analyzed.

RESULTS: The DTI took between 2 minutes 14 seconds for the axial scan with 7-mm slice thickness and 6 minutes 14 seconds for the 44-degree angulated scan with 2.7-mm slice thickness. Splitting the data into a 3-dimensional mosaic data set took between 1 minute 42 seconds (44 degrees, 7 mm; 0 degrees, 7 mm) and 4 minutes 21 seconds (44 degrees, 2.7 mm). The best results were achieved using 44-degree, 2.7-mm DTI. The optimal setting for focal anisotropy was 0.1 and 11 mm for minimal length. Using these parameters, tracking of the OPs was possible in 1 minute 22 seconds and with high quality and correlating with anatomic studies.

CONCLUSION: The use of anteriorly angulated DTI improves the FT work flow and the results of tractography of the OP. The quality of the resulting objects can be judged by anatomic landmarks.

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Navigated Transcranial Magnetic Stimulation and Functional Magnetic Resonance Imaging: Advanced Adjuncts in Preoperative Planning for Central Region Tumors

Neurosurgery 68:1317–1325, 2011 DOI: 10.1227/NEU.0b013e31820b528c

Tumor resection in the vicinity of the motor cortex poses a challenge to all neurosurgeons. For preoperative assessment of eloquent cortical areas, functional magnetic resonance imaging (fMRI) is used, whereas intraoperatively, direct cortical stimulation (DCS) is performed. Navigated transcranial magnetic stimulation (nTMS) is comparable to DCS in activating cortical pyramidal neurons.

OBJECTIVE: To evaluate the reliability of nTMS compared with fMRI and DCS for preoperative resection planning of centrally located tumors.

METHODS: In a prospective series, 11 patients (ages, 20-63 years; mean, 41.9 ± 14.9 years, 2 women) with tumors located in or adjacent to the motor cortex were evaluated for surgery. fMRI and nTMS were applied for preoperative assessment of the extent of tumor resection. A 3-dimensional anatomic data set with superimposed fMRI data was integrated in the eXimia Navigated Brain Stimulation station for ensuing motor cortex mapping by nTMS. Responses from nTMS were evaluated by electromyographic response. During surgery, the coordinates of each DCS site were unambiguously defined and integrated into neuronavigation. A post hoc comparison of the coordinates of nTMS, fMRI, and DCS was performed.

RESULTS: Distances from nTMS to DCS (10.5 ± 5.67 mm) were significantly smaller than those from fMRI to DCS (15.0 ± 7.6 mm).

CONCLUSION: nTMS anticipates information usually only enabled by DCS and therefore allows surgical planning in eloquent cortex surgery.

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Classification and Analysis of the Errors in Neuronavigation

Neurosurgery 68:1131–1143, 2011 DOI: 10.1227/NEU.0b013e318209cc45

There are many different types of errors in neuronavigation, and the reasons and results of these errors are complex. For a neurosurgeon using the neuronavigation system, it is important to have a clear understanding of when an error may occur, what the magnitude of it is, and how to avoid it or reduce its influence on the final application accuracy.

In this article, we classify all the errors into 2 groups according to the working principle of neuronavigation systems. The first group contains the errors caused by the differences between the anatomic structures in the images and that of the real patient, and the second group contains the errors occurring in transforming the position of surgical tools from the patient space to the image space. Each group is further divided into 2 subgroups.

We discuss 16 types of errors and classify each of them into one of the subgroups. The classification and analysis of these errors should help neurosurgeons understand the power and limits of neuronavigation systems and use them more properly.

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Stereotactic Brain Biopsy With a Low-Field Intraoperative Magnetic Resonance Imager

Neurosurgery 68[ONS Suppl 1]:ons217–ons224, 2011 DOI: 10.1227/NEU.0b013e31820826c2

Techniques for stereotactic brain biopsy have evolved in parallel with the imaging modalities used to visualize the brain.

OBJECTIVE: To describe our technique for performing stereotactic brain biopsy using a compact, low-field, intraoperative magnetic resonance imager (iMRI).

METHODS: Thirty-three patients underwent stereotactic brain biopsies with the PoleStar N-20 iMRI system (Medtronic Navigation, Louisville, Colorado). Preoperative iMRI scans were obtained for biopsy target identification and trajectory planning. A skull-mounted device (Navigus, Medtronic Navigation) was used to guide an MRI-compatible cannula to the target. An intraoperative image was acquired to confirm accurate cannula placement within the lesion. Serial images were obtained to track cannula movement and to rule out hemorrhage. Frozen sections were obtained in all but 1 patient with a brain abscess.

RESULTS: Diagnostic tissue was obtained in 32 of 33 patients. In all cases, imaging demonstrated cannula placement within the lesion. Histological diagnoses included 22 primary brain tumors and 10 nonneoplastic lesions. In 61% of the cases, initial trajectory was corrected on the basis of the intraoperative scans. In 1 patient, biopsy was nondiagnostic despite accurate cannula placement. No patient suffered a clinically or radiographically significant hemorrhage during or after surgery. There were no intraoperative complications.

CONCLUSION: Stereotactic biopsy with a low-field iMRI is an accurate way to obtain specimens with a high diagnostic yield. This accuracy, combined with the acceptable additional procedural time, may obviate the need for frozen section. The ability to correct biopsy cannula placement during surgery eliminates the chance of misdiagnosis because of faulty targeting, as well as the risks associated with inconclusive frozen sections and ‘‘blind’’ replacement of the cannula.

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A Moveable 3-Tesla Intraoperative Magnetic Resonance Imaging System

Neurosurgery 68[ONS Suppl 1]:ons168–ons179, 2011 DOI: 10.1227/NEU.0b013e3182045803

Based on success with a prototype 1.5T intraoperative magnetic resonance imaging (iMRI) system and the desire for increased signal-to-noise ratio, along with its relationship to image quality and advanced applications, a 3.0T system that uses the same novel moveable magnet configuration was developed.

OBJECTIVE: To assess clinical applicability by prospectively applying the higher-field system to a neurosurgical cohort.

METHODS: Upgrading to 3.0T required substantial modification of an existing iMRIequipped operating room. The 1.5T magnet was replaced with a ceiling-mounted, moveable 3.0T magnet with a 70-cm working aperture. Local radiofrequency shielding was replaced with whole-room shielding. A new hydraulic operating table, highperformance gradients, and advanced image processing software were also installed. The new system was used as an adjunct to standard neurosurgical practice.

RESULTS: The iMRI system upgrade required 6 months. Since completion, the 3.0T iMRI system has successfully guided neurosurgery in 120 patients without system failure in a patient-focused environment. Intraoperative image quality was superior to that obtained at 1.5T and enabled intraoperative acquisition of advanced imaging sequences, including tractography. Intraoperative imaging was found to modify surgery in a substantial number of patients.

CONCLUSION: Implementation of an iMRI system based on a moveable 3.0T magnet is feasible. From clinical experience with 120 patients, iMRI at 3.0T is safe, reliable, and capable of directing image-guided surgery with exceptional image quality.

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Intraoperative Computed Tomography for Deep Brain Stimulation Surgery: Technique and Accuracy Assessment

Neurosurgery 68[ONS Suppl 1]:ons114–ons124, 2011. DOI: 10.1227/NEU.0b013e31820781bc

The efficacy of deep brain stimulation (DBS) is highly dependent on the accuracy of lead placement.

OBJECTIVE: To describe the use of intraoperative computed tomography (iCT) to confirm lead location before surgical closure and to study the accuracy of this technique.

METHODS: Fifteen patients underwent awake microelectrode-guided DBS surgery in a stereotactic frame. A portable iCT scanner (Medtronic O-arm) was positioned around the patient’s head throughout the procedure and was used to confirm lead location before fixation of the lead to the skull. Images were computationally fused with preoperative magnetic resonance imaging (MRI), and lead tip coordinates with respect to the midpoint of the anterior commissure-posterior commissure line were measured. Tip coordinates were compared with those obtained from postoperative MRI.

RESULTS: iCT was integrated into standard frame-based microelectrode-guided DBS surgery with a minimal increase in surgical time or complexity. Technically adequate 2-dimensional and 3-dimensional images were obtained in all cases. Head positioning and fixation techniques that allow unobstructed imaging are described. Lead tip measurements on iCT fused with preoperative MRI were statistically indistinguishable from those obtained with postoperative MRI.

CONCLUSION: iCT can be easily incorporated into standard DBS surgery, replaces the need for C-arm fluoroscopy, and provides accurate intraoperative 3-dimensional confirmation of electrode tip locations relative to preoperative images and surgical plans. iCT fused to preoperative MRI may obviate the need for routine postoperative MRI in DBS surgery. Technical nuances that must be mastered for the efficient use of iCT during DBS implantation are described.

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Prediction of neurological deficits and recovery after surgery in the supplementary motor area: a prospective study in 26 patients

J Neurosurg 113:1152–1163, 2010.(DOI: 10.3171/2010.6.JNS1090)

Resection of lesions involving the supplementary motor area (SMA) may result in immediate postoperative motor and speech deficits that are reversible in most cases. In the present study the authors aimed to determine the critical involvement of SMA in the lesioned and healthy hemispheres in this functional recovery. They hypothesized that compensatory mechanisms take place following surgery in the SMA, and that these mechanisms can involve either the lesioned or the non-lesioned hemisphere. In addition, they hypothesized that a correlation will be present between the functional MR imaging (fMR) imaging–related activation in the SMA and the occurrence of a functional deficit during intraoperative cortical stimulation.

Methods. Twenty-six patients scheduled for resection of space-occupying lesions involving, or in the vicinity of, the SMA were recruited. Patients underwent an fMR imaging examination that included finger-tapping and verbgeneration tests to assess for motor and language functions. Intraoperatively direct cortical stimulation (DCS) of the SMA region was performed while patients were monitored for language and motor functions using tests similar to those used for the fMR imaging. Task dysfunction during DCS assessed the critical involvement of the SMA in the tested functions. Neurological evaluations were performed prior to surgery and at 3 time points within a month following surgery. A region of interest–based approach was used to evaluate fMR imaging blood oxygen level–dependent activation level and asymmetry in the SMA. These measurements were later compared with the intraoperative DCS and neurological findings.

Results. Functional MR imaging showed greater activation and dominance of the SMA in the lesioned hemisphere in patients who exhibited no motor or language dysfunction during DCS. In addition, patients with the highest activation of the SMA in the lesioned hemisphere for language and motor tests showed stronger coupling of this region with ipsilateral motor and language networks. In contrast, activation in the nonlesioned hemisphere did not correspond with DCS results.

Conclusions. The authors’ findings demonstrate the necessity of activation in the vicinity of the lesioned SMA for functional compensation in motor and language tasks. It is possible that more effective functional coupling of the SMA with motor and language areas in the same hemisphere prevents dysfunctions following surgical intervention. Importantly, fMR imaging activation in the unaffected SMA was not sufficient for development of functional compensation and, if anything, indicated decompensation.

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A Review of Complications Associated With Craniocervical Fusion Surgery

Neurosurgery 67:1396–1403, 2010 DOI: 10.1227/NEU.0b013e3181f1ec73

Fusion at the craniovertebral junction is performed to treat instability of the upper cervical spine and occiput. The literature consists exclusively of case series in which complication rate and avoidance are variably addressed.

OBJECTIVE: To describe the rates of various complications encountered during craniocervical fusions and discuss preoperative and perioperative strategies useful for risk reduction. METHODS: A computerized search of PubMed for literature on craniocervical fusion and other upper cervical fusions was performed. Keywords used in the search included: occipitocervical fusion, odontoid screw, atlantoaxial fusion, with and without complications, anterior fixation, lateral mass screw, transarticular screw, halo, vertebral artery injury, and odontoid fracture. References were limited to studies on human subjects. Other sources were identified from the reference lists of relevant publications.

RESULTS: Twenty-two reports described data derived from 2274 procedures analyzed for complications. The most commonly encountered perioperative complications were related to instrumentation failure after nonunion with rates as high as 7% during occipitocervical fusion and 6.7% during atlantoaxial fusion. Other commonly encountered complications included injury to the vertebral artery (1.3%-4.1% during placement of C1-C2 transarticular screws, most commonly in the case of high-riding vertebral artery), dural tears, and wound infection.

CONCLUSION: Occipitocervical or atlantoaxial fusion procedures can be performed with low morbidity. Safety is enhanced with appropriate preoperative assessment of anatomic variants and preparation for perioperative management of complications.

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Utility of diffusion tensor-imaged (DTI) motor fiber tracking for the resection of intracranial tumors near the corticospinal tract

Acta Neurochir. DOI 10.1007/s00701-010-0817-0

Treatment of intracranial tumors near the corticospinal tract remains a surgical challenge. Several technical tools to map and monitor the motor tract have been implemented. The present study aimed to assess the utility of diffusion tensor imaging (DTI) fiber tracking in the surgical treatment of motor eloquent tumors at our institution.

Methods Patients operated for intracranial tumors close to the motor tract with the use of intraoperative image guidance including DTI fiber tracking of the corticospinal tract and intraoperative motor evoked potential (MEP) monitoring were analyzed. The intraoperative utility of fiber tracking data was analyzed. Furthermore, preoperative MRI scans with and without motor fiber tracking were reevaluated post hoc for tumor relation to the motor tract, estimated resectability, and best approach. Thereby, the utility of fiber tracking in surgical planning was assessed.

Results Nineteen patients were analyzed. The estimation of tumor localization in relation to the motor tract and of resectability was not influenced by fiber tracking in any of the cases. Only in one single case did evaluating surgeons change their surgical approach after the addition of the fiber tracking data. In all cases, fiber tracking included in image guidance did not change the intraoperative strategy, while MEP monitoring did.

Conclusions DTI fiber tracking did not influence the surgical planning or the intraoperative course. However, it is still used at our institution due to its ease in acquisition and its potential impact in a larger series. Furthermore, more experience with this technique is required to lead to a technical improvement.

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Clinical Motor Outcome of Bilateral Subthalamic Nucleus Deep-Brain Stimulation for Parkinson’s Disease Using Image-Guided Frameless Stereotaxy

Neurosurgery 67:1088–1093, 2010 DOI: 10.1227/NEU.0b013e3181ecc887

Image-guided neuronavigation has largely replaced stereotactic frames when precise, real-time anatomic localization is required during neurosurgical procedures. However, some procedures, including placement of deep-brain stimulation (DBS) leads for the treatment of movement disorders, are still performed using frame-based stereotaxy. Despite the demonstration of comparable accuracy between frame-based and ‘‘frameless’’ image-guided approaches, the clinical efficacy of frameless DBS placement has never been reported.

OBJECTIVE: To analyze the outcomes of subthalamic nucleus (STN) DBS using the frameless technique for the treatment of Parkinson’s disease (PD).

METHODS: Of 31 subjects (20 men) with PD for 10 6 4 years, 28 had bilateral STN DBS and 3 had unilateral STN DBS. The Unified Parkinson’s Disease Rating Scale (UPDRS) motor scale (III) and total medication doses were assessed before surgery on and off medication and off medication/ON DBS (off/ON) after 6 to 12 months of STN DBS.

RESULTS: There was a 58% improvement from bilateral STN DBS in the UPDRS III (40 6 16 preoperatively off, 17 6 11 off/ON) 9.6 6 1.9 months after surgery (P , .001). This compared favorably with the published outcomes using the frame-based technique. All motor subscores improved significantly (P , .01). The mean reduction in medication was 50%. No intraoperative complications occurred, but one subject with hypertension died of a delayed hemorrhage postoperatively. Two subjects developed postoperative infections that required lead removal and antibiotics.

CONCLUSIONS: Bilateral STN DBS for PD performed by an experienced team using a frameless approach results in outcomes comparable to those reported with the use of the frame-based technique.

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Image-guided frameless stereotactic biopsy without intraoperative neuropathological examination. Clinical article

Journal of Neurosurgery, August 2010 Volume 113, Number 2
DOI: 10.3171/2009.12.JNS09573
Stereotactic biopsy is a safe and effective technique for the diagnosis of brain tumors. The use of intraoperative neuropathological examination has been routinely advocated to increase diagnostic yield, but the procedure lengthens surgical time, may produce false-negative and -positive results, and current biopsy techniques have a very low nondiagnostic rate. Therefore, the authors questioned the need for intraoperative histological evaluation.
Methods
The authors prospectively studied all patients undergoing image-guided biopsy under the care of a single surgeon (P.L.G.) between July 2005 and October 2007. A Stryker neuronavigation system with a trajectory guide was used to plan a single trajectory, and, using a side-cutting biopsy cannula, multiple biopsy samples were taken from between 1 and 4 sites within the tumor. Tissue was inspected macroscopically by the surgeon and was only submitted for neuropathological assessment postoperatively.
Results
One hundred thirty-four biopsies were performed during the study. A positive diagnosis was established in 133 cases (99.3%). One biopsy was negative (0.7%) and postoperative imaging (performed because the tissue was macroscopically normal) demonstrated inaccurate targeting of the lesion. Significant complications were seen in 3 patients (2.2%) who all had preoperative WHO performance scores of III or IV. Two patients suffered delayed deterioration and died due to probable surgical complications—one with thalamic glioblastoma multiforme (GBM) and one with gliomatosis cerebri. One patient with GBM suffered an intracerebral hematoma that was managed conservatively. Postoperative seizures were seen in 4 patients (3%), and 2 patients (1.5%) experienced a transient neurological deficit. Histological diagnosis showed a GBM in 64 cases, Grade III glioma in 19, Grade I or II in 23, metastasis in 10, lymphoma in 13, and other disease in 4. There were 32 patients discharged to home on the same day as surgery. Compared with the authors’ previous retrospective audit into 127 biopsies, this technique showed improved diagnostic yield (99.3 vs 94.5%, p = 0.032) with fewer complications (2.2 vs 4.7% [not statistically significant]).
Conclusions
This technique of image-guided biopsy has high diagnostic yield with acceptably low morbidity and may be performed as a day case. Intraoperative neuropathological examination would not have increased the diagnostic yield further in this study, and its routine use may not be necessary. In the authors’ department £70,350 (UK)/$114,522 (US) would have been saved by not using intraoperative neuropathology in this series. Therefore, intraoperative neuropathology should no longer be routinely recommended.

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Functional Magnetic Resonance Imaging and Diffusion Tensor Tractography Incorporated Into an Intraoperative 3-Dimensional Ultrasound-Based Neuronavigation System: Impact on Therapeutic Strategies, Extent of Resection, and Clinical Outcome

Neurosurgery 67:251-264, 2010 DOI: 10.1227/01.NEU.0000371731.20246.AC

Functional neuronavigation with intraoperative 3-dimensional (3D) ultrasound may facilitate safer brain lesion resections than conventional neuronavigation.

OBJECTIVE: In this study, functional magnetic resonance imaging (fMRI) and diffusion tensor tractography (DTT) were used to map eloquent areas. We assessed the use of fMRI and DTT for preoperative assessments and determined whether using these data together with 3D ultrasound during surgery enabled safer lesion resection.

METHODS:We reviewed 51 consecutive patients with intracranial lesions in whom fMRI with or without DTT was used to map eloquent areas. To assess a possible impact of fMRI/DTT, we reviewed and analyzed the quality of the fMRI/DTT data, any change in therapeutic strategies, lesion to eloquent area distance (LEAD), extent of resection, and clinical outcome.

RESULTS: As a result of the fMRI/DTT mapping, the therapeutic strategies were changed in 4 patients. The median tumor residue for glioma patients was 11% (n = 33) and 0% for nonglioma lesions (n = 12). For gliomas, there was a significant correlation between decreasing LEAD and increasing tumor residue. Of the glioma patients, 42% underwent gross total resection (≥ 95%) and 12% suffered neurological worsening after surgery as a result of complications. Of glioma patients with an LEAD of ≤ 5 mm, 24% underwent gross total resection and 10% experienced neurological deterioration.

CONCLUSION: This study demonstrates that preoperative fMRI and DTT had direct consequences for therapeutic strategies and indicates their impact on intraoperative strategies to spare eloquent cortex and tracts. Functional neuronavigation combined with intraoperative 3D ultrasound can, in most patients, enable resection of brain lesions with general anesthesia without jeopardizing neurological function.

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