A Novel Type of IDH-wildtype Glioma Characterized by Gliomatosis Cerebri-like Growth Pattern, TERT Promoter Mutation, and Distinct Epigenetic Profile.

Diffuse gliomas in adults encompass a heterogenous group of central nervous system neoplasms. In recent years, extensive (epi-)genomic profiling has identified several glioma subgroups characterized by distinct molecular characteristics, most importantly IDH1/2 and histone H3 mutations. A group of 16 diffuse gliomas classified as "adult-type diffuse high-grade glioma, IDH-wildtype, subtype F (HGG-F)" was identified by the DKFZ v12.5 Brain Tumor Classifier . Histopathologic characterization, exome sequencing, and review of clinical data was performed in all cases. Based on unsupervised t -distributed stochastic neighbor embedding and clustering analysis of genome-wide DNA methylation data, HGG-F shows distinct epigenetic profiles separate from established central nervous system tumors. Exome sequencing demonstrated frequent TERT promoter (12/15 cases), PIK3R1 (11/16), and TP53 mutations (5/16). Radiologic characteristics were reminiscent of gliomatosis cerebri in 9/14 cases (64%). Histopathologically, most cases were classified as diffuse gliomas (7/16, 44%) or were suspicious for the infiltration zone of a diffuse glioma (5/16, 31%). None of the cases demonstrated microvascular proliferation or necrosis. Outcome of 14 patients with follow-up data was better compared to IDH-wildtype glioblastomas with a median progression-free survival of 58 months and overall survival of 74 months (both P <0.0001). Our series represents a novel type of adult-type diffuse glioma with distinct molecular and clinical features. Importantly, we provide evidence that TERT promoter mutations in diffuse gliomas without further morphologic or molecular signs of high-grade glioma should be interpreted in the context of the clinicoradiologic presentation as well as epigenetic profile and may not be suitable as a standalone marker for glioblastoma, IDH-wildtype.

Neurophysiological basis of direct cortical stimulation and applied neuroanatomy of the motor cortex: a review.

Intraoperative electrical stimulation of the motor cortex is a sensitive method for intraoperative mapping and monitoring of this region. Two different stimulation techniques have been established, the bipolar and monopolar techniques. Controversy exists regarding the most suitable method. Both methods have advantages and disadvantages and different electrophysiological backgrounds. The present study is a review of the electrophysiological basis of direct cortical electrical stimulation of the motor cortex. Both methods are discussed and their field of application is presented.

Subcortical mapping and monitoring during insular tumor surgery.

OBJECT: The treatment of insular tumors is controversial. Surgical treatment is associated with a higher morbidity rate than other therapies. The present work presents a new method in which the descending motor pathways are monitored during surgery for insular tumors. METHODS: Intraoperative monitoring was performed in a combination of 2 techniques. The motor cortex was stimulated with a transcranial electrical stimulus. In addition, direct subcortical stimulation was performed with an electrical anodal monopolar stimulus. Compound motor action potentials (CMAPs) were recorded from target muscles. RESULTS: Fifteen patients were included in this preliminary study. Following transcranial stimulation, CMAPs were recorded in all cases. Subcortical stimulation was successful in 12 cases. Significant CMAP alterations were recorded in 5 patients. There were no false-negative results in the series. CONCLUSIONS: The technique presented here is a safe method. It allows a quantitative monitoring of motor function and functional mapping of the pyramidal tract during insular surgery.

Neurophysiological intraoperative monitoring in neurosurgery: aid or handicap? An international survey.

OBJECT: Neurophysiological intraoperative monitoring (IOM) is regarded as a useful tool to provide information about physiological changes during surgery in eloquent areas of the nervous system, to increase safety and reduce morbidity. Nevertheless, numerous older studies report that very few patients benefit from IOM, and that there are high rates of false-positive and false-negative changes of neurophysiological parameters during surgery. There is an ongoing discussion about the effectiveness of neurophysiological IOM. This questionnaire study was performed to evaluate the attitude of neurosurgeons toward neurophysiological IOM and the availability of this tool. METHODS: One hundred fifty neurosurgeons from 60 institutions in 16 countries were asked to answer anonymously a questionnaire with 11 questions. The questionnaire covered aspects of personal experience, the neurosurgical institution, and availability of neurophysiological IOM as well as asking the surgeon's opinion of the procedure. RESULTS: One hundred nine questionnaires were returned (73%). Seven questionnaires were excluded because of failure to complete the form correctly or completely, leaving 102 respondents from 44 institutions in 16 countries in the study; 79.5% of the included institutions provided neurophysiological IOM. Young neurosurgeons did not put more trust in IOM than experienced neurosurgeons. With growing IOM experience, surgeons seem to allow less influence of the findings on the course of their operation. At large institutions in which > 1500 operations per year are done, IOM is performed by the neurosurgeons themselves in most cases. In institutions with fewer operations, the IOM team consists mostly of nonneurosurgeons. Regardless of the availability of neurophysiological IOM, all surgeons stated that IOM is gaining increasing importance. CONCLUSIONS: Neurophysiological IOM represents an established tool in neurosurgery. Although the importance of IOM is emphasized by the majority of neurosurgeons, the relevance of this tool to the course of the operation changes with increasing neurophysiological IOM experience.

Sensor-based neuronavigation: evaluation of a large continuous patient population.

OBJECTIVE: Navigation systems enable neurosurgeons to guide operations with imaging data. Sensor-based neuronavigation uses an electromagnetic field and sensors to measure the positions of the patient's brain anatomy and the surgical instruments. The aim of this investigation was to determine the accuracy level of sensor-based tracking in a large patient collection. METHODS: This study covers 250 patients operated upon during a continuous 5.5-year period. The patients had a wide range of indications and surgical procedures. The operations were performed with a direct current (DC) pulsed sensor-based electromagnetic navigation system. Four kinds of errors were measured: the fiducial registration error (FRE), the target registration error (TRE), brain shift, and the position error (PE). These errors were calculated for five subgroups of indications: target determination and trajectory guidance, functional navigation, skull base and neurocranium, determination of resection volume, and transnasal and transsphenoidal access. RESULTS: The overall mean FRE was 1.66mm (+/-0.61mm). The overall mean TREs were 1.33mm (+/-0.51mm) centroid and 1.59mm (+/-0.57mm) lesional. The overall mean brain shift for applicable cases was 1.61mm (+/-1.14mm). The overall mean PE was 0.92mm (+/-0.54mm). CONCLUSIONS: By and large, modern sensor-based neuronavigation operates within an acceptable and commonplace degree of error. However, the neurosurgeon must remain critical in cases of small lesions, and must exert caution not to introduce further interference from metal objects or electromagnetic devices.

Isolated B-cell lymphoproliferative disorder at the dura mater with B-cell chronic lymphocytic leukemia immunophenotype.

Lymphoma manifestations of the dura mater are extremely rare and have mostly been attributed to extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) type. We report a patient with an isolated meningeal tumor, identified as a B-cell lymphoproliferative disorder with typical B-cell chronic lymphocytic leukemia immunophenotype. Because of the subclinical detection of trisomy 3 in the bone marrow by cytogenetic analysis and interphase fluorescence in situ hybridization, CD5(+) MALT is an important differential diagnosis; however, to our knowledge, this entity has never been reported in the context of dural lymphoma.

[Evaluation of a DC pulsed magnetic tracking system in neurosurgical navigation: technique, accuracies, and influencing factors]. / Evaluierung eines DC-gepulsten magnetischen Trackingsystems im Rahmen der neurochirurgischen Navigation: Technik, Genauigkeiten und Einflussparameter.

Navigation systems are useful instruments in cranial neurosurgery. For specification of position, so-called sensor-based navigation techniques use: (a) a signal emitter that generates a defined electromagnetic field in the area of the operation site; and (b) small sensors that detect the position of various operating instruments in the electromagnetic field. For a long time, owing to a lack of clinical data and long-term studies, electromagnetic systems have been regarded as error-prone and imprecise. With the development of a pulsed direct current (DC) technique, precision levels can now be reached that are comparable with those of established optical and mechanical measuring procedures. However, it must be noted that the influence on the measuring accuracy within the operating field increases with increasing susceptibility of the various metals used in the operating theatre (titanium

Empty polyetheretherketone (PEEK) cages in anterior cervical diskectomy and fusion (ACDF) show slow radiographic fusion that reduces clinical improvement: results from the prospective multicenter "PIERCE-PEEK" study.

BACKGROUND: Anterior cervical diskectomy and fusion (ACDF) is a well-established surgical treatment for radiculopathy and myelopathy. Previous studies showed that empty PEEK cages have lower radiographic fusion rates, but the clinical relevance remains unclear. This paper's aim is to provide high-quality evidence on the outcomes of ACDF with empty PEEK cages and on the relevance of radiographic fusion for clinical outcomes. METHODS: This large prospective multicenter clinical trial performed single-level ACDF with empty PEEK cages on patients with cervical radiculopathy or myelopathy. The main clinical outcomes were VAS (0-10) for pain and NDI (0-100) for functioning. Radiographic fusion was evaluated by two investigators for three different aspects. RESULTS: The median (range) improvement of the VAS pain score was: 3 (1-6) at 6 months, 3 (2-8) at 12 months, and 4 (2-8) at 18 months. The median (range) improvement of the NDI score was: 12 (2-34) at 6 months, 18 (4-46) at 12 months, and 22 (2-44) at 18 months. Complete radiographic fusion was reached by 126 patients (43%) at 6 months, 214 patients (73%) at 12 months, and 241 patients (83%) at 18 months. Radiographic fusion was a highly significant (p < 0.001) predictor of the improvement of VAS and NDI scores. CONCLUSION: This study provides strong evidence that ACDF is effective treatment, but the overall rate of radiographic fusion with empty PEEK cages is slow and insufficient. Lack of complete radiographic fusion leads to less improvement of pain and disability. We recommend against using empty uncoated pure PEEK cages in ACDF. TRIAL REGISTRATION: ISRCTN42774128. Retrospectively registered 14 April 2009.

Real-time tracking of vertebral body movement with implantable reference microsensors.

OBJECTIVE: In the spine, navigation techniques serve mainly to control and accurately target insertion of implants. The main source of error is that the spine is not a rigid organ, but rather a chain of semiflexible movement segments. Any intraoperative manipulation of the patient alters the geometry and volumetry as compared to the 3D volume model created from the image data. Thus, the objective of the study was to implement the theoretical principle of microsensor referencing in a model experiment and to clarify which anatomical structures are suitable for intermittent implantation of positional sensors, as illustrated with cervical vertebral bodies. MATERIALS AND METHODS: Laboratory tests were conducted using 70 models of human cervical vertebral bodies. The first experiment investigated whether arbitrary movements of vertebral bodies can be tracked with the positional information from the implanted microsensors. The accuracy of this movement monitoring was determined quantitatively on the basis of positional error measurement. In the second experiment, different ventral and dorsal surgical operations were simulated on five models of the cervical spine. Quantifiable measurement values such as the spatial extension of the intervertebral space and the relative positions of the planes of the upper plates were determined. RESULTS: With respect to the differing anatomy of the individual vertebral bodies of the cervical spine, the sensors could be placed securely with a 5x2 mm drill. The registration error (RE) was determined as a root mean square error. The mean value was 0.9425 mm (range: 0.57-1.2 mm; median: 0.9400 mm; SD: 0.1903 mm). The precision of the movement monitoring of the vertebral body was investigated along its three main axes. The error tolerance between post-interventional 3D reconstruction and direct measurement on the model did not exceed 1.3 mm in the distance measurements or 2.5 degrees in the angular measurements. The tomograms on the system monitor could be updated in close to real time on the basis of the positional information from the reference sensor. CONCLUSIONS: Motion sensors implanted into the vertebral bodies communicated any change in position to the navigation system in close to real time, thus enabling the preoperative image data set to be updated. The experiments described could ultimately show that continuous real-time visualization of individual vertebral body movements along the movement axes (flexion-extension, tilting and rotation) is possible with high accuracy using implantable microsensors. A future application of such microsensors might be the integration of robot systems into spinal microsurgery.

The Negligible Influence of Chronic Obesity on Hospitalization, Clinical Status, and Complications in Elective Posterior Lumbar Interbody Fusion.

Background. Posterior lumbar interbody fusion (PLIF) is a common surgical treatment for degenerative spinal instability, but many surgeons consider obesity a contraindication for elective spinal fusion. The aim of this study was to analyze whether obesity has any influence on hospitalization parameters, change in clinical status, or complications. Methods. In this prospective study, regression analysis was used to analyze the influence of the body mass index (BMI) on operating time, postoperative care, hospitalization time, type of postdischarge care, change in paresis or sensory deficits, pain level, wound complications, cerebrospinal fluid leakage, and implant complications. Results. Operating time increased only 2.5 minutes for each increase of BMI by 1. The probability of having a wound complication increased statistically with rising BMI. Nonetheless, BMI accounted for very little of the variation in the data, meaning that other factors or random chances play a much larger role. Conclusions. Obesity has to be considered a risk factor for wound complications in patients undergoing elective PLIF for degenerative instability. However, BMI showed no significant influence on other kinds of peri- or postoperative complications, nor clinical outcomes. So obesity cannot be considered a contraindication for elective PLIF.

Does preoperative paresis influence intraoperative monitoring of the motor cortex?

Intraoperative monitoring of motor function by means of motor evoked potentials (MEPs) is a new method. The current study examines the influence of preoperative paresis on the feasibility and reliability of this method. Intraoperative monitoring of MEPs was performed in 58 patients during surgery in the central region. The patients were divided into three groups according to their preoperative strength (group I, muscle strength less than or equal to grade 4 according to the British Medical Research Council grading system [n = 17]; group II, normal strength (n = 36); and group III, muscle strength less than grade 5 but not worse than grade 4 [n = 5]). The motor cortex was stimulated directly with a high-frequency monopolar anodal train. In groups II and III, MEPs were elicited in all patients on cortical stimulation, whereas in group I a response was obtained in only 88% of patients. The MEP parameters in all groups had a broad interindividual range of variation. A correlation between individual intraoperative potential changes and surgical maneuvers was observed in seven patients in group II and in four patients in group I. No MEP changes were recorded in group III. Irreversible MEP changes (groups I and II) resulted in postoperative clinical deterioration. No postoperative deterioration of motor function was observed in patients with reversible MEP changes. Preoperative paresis reduces the feasibility of the method; however, it has no influence on the intraoperative pattern and reaction of the MEPs.

Impact of somatosensory evoked potential monitoring on cervical surgery.

Controversy still exists about the necessity of somatosensory evoked potential (SSEP) monitoring during cervical surgery. The purpose of this prospective study is to determine the impact of SSEP monitoring on anterior cervical surgery. Intraoperative SSEP monitoring was performed in 100 patients treated by an anterior cervical approach. The patients were divided into three groups according to their preoperative clinical condition. Somatosensory evoked potential monitoring was performed during five stages of the procedure: M1, after the induction of anesthesia; M2, during positioning; M3, during distraction of the intervertebral space; M4, throughout decompression; and M5, during graft placement. Normal SSEPs were obtained during M1 from all the patients in group 2. Pathologic SSEPs were recorded at M1 in 45 patients from group 1. No SSEPs were recorded at M1 in six patients in group 3. A deterioration of the SSEPs was observed in 35 patients during M2. Deteriorated SSEPs were observed during M3 in 14 patients. No deterioration of the SSEPs was recorded during M4. Intraoperative SSEP monitoring is easy to perform and helps to increase safety during anterior cervical surgery. Critical phases of the surgical procedure were identified and the surgical strategy was modified as a result of this study.

The value of intraoperative neurophysiological monitoring for microsurgical removal of conus medullaris lipomas: a 12-year retrospective cohort study.

BACKGROUND: Lipomas in the lower spinal canal can lead to progressive neurological deficits, so they may have to be surgically removed. Intraoperative neurophysiological monitoring serves to minimize the morbidity of the surgical procedure. However, so far there are no evidence-based recommendations which type of monitoring procedure or combination of procedures to choose. METHODS: The aim of this study was to evaluate the feasibility and value of various intraoperative monitoring techniques: motor and sensory evoked potentials (MEP, SEP), free-running and triggered electromyography (EMG). Thirty cases of spinal lipomas of the Conus medullaris (dorsal Type A: 20.0%; caudal Type B: 33.3%; transitional Type C: 46.7%) were retrospectively evaluated over a 12-year period. RESULTS: The patients were mostly pediatric and suffered from persistent pain (73.3%), pareses (56.7%), sensory deficits (43.4%), and/or urogenital dysfunctions (60.0%). SEPs were successfully evoked in 66.7% of cases, MEPs in 86.7% of cases, and EMGs in 100%. MEP alterations correlated with direct mechanical maneuvers in the operating site. SEP changes correlated mostly with physiological events, such as rinsing/cooling of the operating site. Spike-, burst- or tonic train-activity was found in the free-running EMG that occurred only with certain manipulation patterns. Irreversible MEP changes and signal loss in the triggered EMG correlated with post-operative deficits. CONCLUSIONS: The results of this study showed, that intraoperative monitoring could be considered a helpful tool during lipoma tumor surgery near the Conus medullaris. Most reliable results were obtained from transcranial MEPs, free-running EMGs, and triggered EMGs. That's why the authors favor a routine set-up consisting of at least these three techniques, as this enables mapping at the beginning of the operation, continuous functional testing during surgery, and prognosis of the post-operative symptomology.

Intraoperative neurophysiological monitoring of extracranial-intracranial bypass procedures.

OBJECT: Intraoperative neurophysiological monitoring (IONM) represents an established tool in neurosurgery to increase patient safety. Its application, however, is controversial. Its use has been described as helpful in avoiding neurological deterioration during intracranial aneurysm surgery. Its impact on extracranial-intracranial (EC-IC) bypass surgery involving parent artery occlusion for the treatment of complex aneurysms has not yet been studied. The authors therefore sought to evaluate the effects of IONM on patient safety, the surgeon's intraoperative strategies, and functional outcome of patients after cerebral bypass surgery. Intraoperative neurophysiological monitoring results were compared with those of intraoperative blood flow monitoring to assess bypass graft perfusion. METHODS: Compound motor action potentials (CMAPs) were generated using transcranial electrical stimulation in patients undergoing EC-IC bypass surgery. Preoperative and postoperative motor function was analyzed. To assess graft function, intraoperative flowmetry and indocyanine green fluorescence angiography were performed. Special care was taken to compare the relevance of electrophysiological and blood flow monitoring in the detection of critical intraoperative ischemic episodes. RESULTS: The study included 31 patients with 31 aneurysms and 1 bilateral occlusion of the internal carotid arteries, undergoing 32 EC-IC bypass surgeries in which radial artery or saphenous vein grafts were used. In 11 cases, 15 CMAP events were observed, helping the surgeon to determine the source of deterioration and to react to it: 14 were reversible and only 1 showed no recovery. In all cases, blood flow monitoring showed good perfusion of the bypass grafts. There were no false-negative results in this series. New postoperative motor deficits were transient in 1 case, permanent in 1 case, and not present in all other cases. CONCLUSIONS: Intraoperative neurophysiological monitoring is a helpful tool for continuous functional monitoring of patients undergoing large-caliber vessel EC-IC bypass surgery. The authors' results suggest that continuous neurophysiological monitoring during EC-IC bypass surgery has relevant advantages over flow-oriented monitoring techniques such as intraoperative flowmetry or indocyanine green-based angiography.

Impact of intraoperative neurophysiological monitoring on surgery of high-grade gliomas.

INTRODUCTION: Controversy exists on the application of intraoperative monitoring (IOM) procedures during malignant glioma surgery. Because resection rate correlates with the survival rate, it is of paramount importance to determine these values. This study evaluates the impact of IOM on the resection rates, the survival rate, the quality of life, and the functional outcome of malignant gliomas. METHODS: Forty patients with a glioma were included in the study. They were divided into two groups: group 1, patients with a glioma not adjacent to motor cortical areas operated without the use of IOM, and group 2, patients with a glioma adjacent to the central region operated under IOM. The further treatment was the same in both groups. The following parameters were analyzed: tumor resection rate, survival rate, preoperative and postoperative Karnowsky Performance Score, and preoperative and postoperative motor function. RESULTS: There were no statistically significant differences in the type of surgery performed or in the resection grade in both groups. No statistically significant difference was found in the median survival of the two groups in the Kaplan-Meier analysis with mean survival time 48.8 and 48.2 weeks. The mean Karnowsky Performance Score preoperative was 82.5 and 81.5, and 81.1 and 82.7 after 6 months, for groups 1 and 2, respectively. CONCLUSION: The data presented here demonstrate that tumor resection is not negatively influenced by IOM. Accordingly, gliomas that are found to be otherwise resectable should not be excluded from aggressive management simply because of their vicinity to the motor cortex. Surgery should be performed under IOM.

Navigated transcranial magnetic stimulation for preoperative functional diagnostics in brain tumor surgery.

OBJECTIVE: Transcranial magnetic stimulation (TMS) is a noninvasive method for analyzing cortical function. To utilize TMS for presurgical functional diagnostics, the magnetic impulse must be precisely targeted by stereotactically positioning the coil. The aim of this study was to evaluate the usefulness of TMS for operation planning when combined with a sensor-based electromagnetic navigation system (nTMS). METHODS: Preoperative functional mapping with nTMS was performed in 10 patients with rolandic tumors. Intraoperative mapping was performed with the "gold standard" of direct cortical stimulation. Stimulation was performed in the same predefined 5-mm raster for both modalities, and the results were compared. RESULTS: In regard to the 5-mm mapping raster, the centers of gravity of nTMS and direct cortical stimulation were located at the same spot in 4 cases and at neighboring spots in the remaining 6 cases. The mean distance between the tumor and the nearest motor response ("safety margin") was 7.9 mm (range, 5-15 mm; standard deviation, 3.2 mm) for nTMS and 6.6 mm (range, 0-12 mm; standard deviation, 3.4 mm) for direct cortical stimulation. CONCLUSION: nTMS allowed for reliable, precise application of the magnetic impulse, and the peritumoral somatotopy corresponded well between the 2 modalities in all 10 cases. nTMS is a promising method for preoperative functional mapping in motor cortex tumor surgery.

Electrical excitability of the angular gyrus.

The angular gyrus (AG) is a circumscribed area between the parietal and temporal lobes and its exact function is not clear. The purpose of the present study was to investigate the feasibility of intraoperative electrical stimulation of the AG in humans. The AG was electrically stimulated in five cases with the assistance of neuronavigation. Two different stimulation techniques were applied: bipolar cortical stimulation and monopolar cortical stimulation. After monopolar cortical stimulation, a compound muscle action potential was recorded from the contralateral arm muscles in three patients. In the remaining two patients no compound muscle action potential was elicited after monopolar cortical stimulation. The latency of the recorded compound muscle action potential from the thenar muscle ranged from 30.3 to 32.7 milliseconds and from the two forearm flexors was 28.7 and 29.7. Bipolar stimulation generated a motor response in the contralateral extremity in three research subjects but no motor response in two. Response was obtained in all three research subjects with the combination of 40 Hz and a duration of 4 or 6 seconds. Because this is to their knowledge the first report demonstrating a functional output of Exner's area to the motor cortex, it would be difficult to suggest all the pathways and functions of this complex connectivity. The aim of the pilot study presented here was to investigate the feasibility of electrical stimulation of the AG. The findings presented here show that intraoperative electrical stimulation of the AG is possible. Although the results are limited by the small number of patients investigated, they are encouraging and suggest that it is worthwhile to continue research in this area.

Transpedicular screw fixation in the thoracic and lumbar spine with a novel cannulated polyaxial screw system.

OBJECTIVE: Transpedicular screws are commonly and successfully used for posterior fixation in spinal instability, but their insertion remains challenging. Even using navigation techniques, there is a misplacement rate of up to 11%. The aim of this study was to assess the accuracy of a novel pedicle screw system. METHODS: Thoracic and lumbar fusions were performed on 67 consecutive patients for tumor, trauma, degenerative disease or infection. A total of 326 pedicular screws were placed using a novel wire-guided, cannulated, polyaxial screw system (XIA Precision(®), Stryker). The accuracy of placement was assessed postoperatively by CT scan, and the patients were followed-up clinically for a mean of 16 months. RESULTS: The total medio-caudal pedicle wall perforation rate was 9.2% (30/326). In 19 of these 30 cases a cortical breakthrough of less than 2 mm occurred. The misplacement rate (defined as a perforation of 2 mm or more) was 3.37% (11/326). Three of these 11 screws needed surgical revision due to neurological symptoms or CSF leakage. There have been no screw breakages or dislocations over the follow up-period. CONCLUSION: We conclude that the use of this cannulated screw system for the placement of pedicle screws in the thoracic and lumbar spine is accurate and safe. The advantages of this technique include easy handling without a time-consuming set up. Considering the incidence of long-term screw breakage, further investigation with a longer follow-up period is necessary.

Neuronavigation without rigid pin fixation of the head in left frontotemporal tumor surgery with intraoperative speech mapping.

OBJECTIVE: Intraoperative speech mapping has evolved into the "gold standard" for neurosurgical removal of lesions near the language cortex. The integration of neuronavigation into a multimodal protocol can improve the reliability of this type of operation, but most systems require rigid fixation of the patient's head throughout the operation. This article describes and evaluates a new noninvasively attached sensor-based reference tool, which can replace rigid pin fixation of the patient's head during awake craniotomies. METHODS: The attachment technique and the resulting application accuracy were investigated under clinical conditions in 13 patients undergoing awake craniotomy with intraoperative mapping of cortical language sites. RESULTS: Spatial information was used for updating the image guidance by continuously adjusting the image planes relative to the position of the patient's head. The mean registration error achieved with this technique was 1.53 +/- 0.51 mm (fiducial registration error +/- standard deviation). The system's median application accuracy between dura opening and closure ranged from 0.83 to 1.85 mm (position error). CONCLUSION: The use of a reference sensor can replace uncomfortable pin fixation of the patient's head during navigation-supported awake craniotomies. Application accuracy is not affected by repositioning of the patient or by unavoidable head movements. Thus, this technique enables full exploitation of the benefits of navigation in a multimodal operative protocol without the need to rigidly fix the patient's head.