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Andreas Raabe, Jürgen Beck, Philippe Schucht and Kathleen Seidel

Object

The authors developed a new mapping technique to overcome the temporal and spatial limitations of classic subcortical mapping of the corticospinal tract (CST). The feasibility and safety of continuous (0.4–2 Hz) and dynamic (at the site of and synchronized with tissue resection) subcortical motor mapping was evaluated.

Methods

The authors prospectively studied 69 patients who underwent tumor surgery adjacent to the CST (< 1 cm using diffusion tensor imaging and fiber tracking) with simultaneous subcortical monopolar motor mapping (short train, interstimulus interval 4 msec, pulse duration 500 μsec) and a new acoustic motor evoked potential alarm. Continuous (temporal coverage) and dynamic (spatial coverage) mapping was technically realized by integrating the mapping probe at the tip of a new suction device, with the concept that this device will be in contact with the tissue where the resection is performed. Motor function was assessed 1 day after surgery, at discharge, and at 3 months.

Results

All procedures were technically successful. There was a 1:1 correlation of motor thresholds for stimulation sites simultaneously mapped with the new suction mapping device and the classic fingerstick probe (24 patients, 74 stimulation points; r2 = 0.98, p < 0.001). The lowest individual motor thresholds were as follows: > 20 mA, 7 patients; 11–20 mA, 13 patients; 6–10 mA, 8 patients; 4–5 mA, 17 patients; and 1–3 mA, 24 patients. At 3 months, 2 patients (3%) had a persistent postoperative motor deficit, both of which were caused by a vascular injury. No patient had a permanent motor deficit caused by a mechanical injury of the CST.

Conclusions

Continuous dynamic mapping was found to be a feasible and ergonomic technique for localizing the exact site of the CST and distance to the motor fibers. The acoustic feedback and the ability to stimulate the tissue continuously and exactly at the site of tissue removal improves the accuracy of mapping, especially at low (< 5 mA) stimulation intensities. This new technique may increase the safety of motor eloquent tumor surgery.

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Clemens Raabe, Jens Fichtner, Jürgen Beck, Jan Gralla and Andreas Raabe

OBJECTIVE

Frontal ventriculostomy is one of the most frequent and standardized procedures in neurosurgery. However, many first and subsequent punctures miss the target, and suboptimal placement or misplacement of the catheter is common. The authors therefore reexamined the landmarks and rules to determine the entry point and trajectory with the best hit rate (HtR).

METHODS

The authors randomly selected CT scans from their institution’s DICOM pool that had been obtained in 50 patients with normal ventricular and skull anatomy and without ventricular puncture. Using a 5 × 5–cm frontal grid with 25 entry points referenced to the bregma, the authors examined trajectories 1) perpendicular to the skull, 2) toward classic facial landmarks in the coronal and sagittal planes, and 3) toward an idealized target in the middle of the ipsilateral anterior horn (ILAH). Three-dimensional virtual reality ventriculostomies were simulated for these entry points; trajectories and the HtRs were recorded, resulting in an investigation of 8000 different virtual procedures.

RESULTS

The best HtR for the ILAH was 86% for an ideal trajectory, 84% for a landmark trajectory, and 83% for a 90° trajectory, but only at specific entry points. The highest HtRs were found for entry points 3 or 4 cm lateral to the midline, but only in combination with a trajectory toward the contralateral canthus; and 1 or 2 cm lateral to the midline, but only paired with a trajectory toward the nasion. The same “pairing” exists for entry points and trajectories in the sagittal plane. For perpendicular (90°) trajectories, the best entry points were at 3–5 cm lateral to the midline and 3 cm anterior to the bregma, or 4 cm lateral to the midline and 2 cm anterior to the bregma.

CONCLUSIONS

Only a few entry points offer a chance of a greater than 80% rate of hitting the ILAH, and then only in combination with a specific trajectory. This “pairing” between entry point and trajectory was found both for landmark targeting and for perpendicular trajectories, with very limited variability. Surprisingly, the ipsilateral medial canthus, a commonly reported landmark, had low HtRs, and should not be recommended as a trajectory target.

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Andreas Raabe, Jürgen Beck, Stefan Rohde, Joachim Berkefeld and Volker Seifert

Object

The aim of this study was to investigate the feasibility of integrating three-dimensional rotational angiography (3D-RA) data into a surgical navigation system and to assess its accuracy and potential clinical benefit.

Methods

The study cohort consisted of 16 patients with 16 intracranial aneurysms who had been scheduled for routine or emergency surgery. Rotational angiography data were exported using a virtual reality modeling language file format and imported into the BrainLAB VectorVision2 image-guided surgery equipment. During 3D-RA the position of the head was measured using a special headframe. The authors also determined the accuracy of 3D-RA image guidance and the clinical benefit as judged by the surgeon, including, for example, early identification of branching vessels and the aneurysm.

There was good correspondence between the 3D-RA–based navigation data and the intraoperative vascular anatomy in all cases, with a maximum error of 9° of angulation and 9° of rotation. In eight cases, the surgeon determined that the 3D-RA image guidance facilitated the surgical procedure by predicting the location of the aneurysm or the origin of a branching artery that had been covered by brain tissue and blood clots.

Conclusions

The integration of 3D-RA into surgical navigation systems is feasible, but it currently requires a new perspective-registration technique. The intraoperative 3D view provides useful information about the vascular anatomy and may improve the quality of aneurysm surgery in selected cases.

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Kathleen Seidel, Jürgen Beck, Lennart Stieglitz, Philippe Schucht and Andreas Raabe

Object

Mapping and monitoring are believed to provide an early warning sign to determine when to stop tumor removal to avoid mechanical damage to the corticospinal tract (CST). The objective of this study was to systematically compare subcortical monopolar stimulation thresholds (1–20 mA) with direct cortical stimulation (DCS)–motor evoked potential (MEP) monitoring signal abnormalities and to correlate both with new postoperative motor deficits. The authors sought to define a mapping threshold and DCS-MEP monitoring signal changes indicating a minimal safe distance from the CST.

Methods

A consecutive cohort of 100 patients underwent tumor surgery adjacent to the CST while simultaneous subcortical motor mapping and DCS-MEP monitoring was used. Evaluation was done regarding the lowest subcortical mapping threshold (monopolar stimulation, train of 5 stimuli, interstimulus interval 4.0 msec, pulse duration 500 μsec) and signal changes in DCS-MEPs (same parameters, 4 contact strip electrode). Motor function was assessed 1 day after surgery, at discharge, and at 3 months postoperatively.

Results

The lowest individual motor thresholds (MTs) were as follows (MT in mA, number of patients): > 20 mA, n = 12; 11–20 mA, n = 13; 6–10 mA, n = 20; 4–5 mA, n = 30; and 1–3 mA, n = 25. Direct cortical stimulation showed stable signals in 70 patients, unspecific changes in 18, irreversible alterations in 8, and irreversible loss in 4 patients. At 3 months, 5 patients had a postoperative new or worsened motor deficit (lowest mapping MT 20 mA, 13 mA, 6 mA, 3 mA, and 1 mA). In all 5 patients DCS-MEP monitoring alterations were documented (2 sudden irreversible threshold increases and 3 sudden irreversible MEP losses). Of these 5 patients, 2 had vascular ischemic lesions (MT 20 mA, 13 mA) and 3 had mechanical CST damage (MT 1 mA, 3 mA, and 6 mA; in the latter 2 cases the resection continued after mapping and severe DCS-MEP alterations occurred thereafter). In 80% of patients with a mapping MT of 1–3 mA and in 75% of patients with a mapping MT of 1 mA, DCS-MEPs were stable or showed unspecific reversible changes, and none had a permanent motor worsening at 3 months. In contrast, 25% of patients with irreversible DCS-MEP changes and 75% of patients with irreversible DCS-MEP loss had permanent motor deficits.

Conclusions

Mapping should primarily guide tumor resection adjacent to the CST. DCS-MEP is a useful predictor of deficits, but its value as a warning sign is limited because signal alterations were reversible in only approximately 60% of the present cases and irreversibility is a post hoc definition. The true safe mapping MT is lower than previously thought. The authors postulate a mapping MT of 1 mA or less where irreversible DCS-MEP changes and motor deficits regularly occur. Therefore, they recommend stopping tumor resection at an MT of 2 mA at the latest. The limited spatial and temporal coverage of contemporary mapping may increase error and may contribute to false, higher MTs.

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Alessa Schütz, Michael Murek, Lennart Henning Stieglitz, Corrado Bernasconi, Sonja Vulcu, Jürgen Beck, Andreas Raabe and Philippe Schucht

OBJECTIVE

Decompressive craniectomy (DC) is an established treatment for refractory intracranial hypertension. It is usually followed by autologous cranioplasty (AC), the reinsertion of a patient’s explanted bone flap. A frequent long-term complication of AC is bone flap resorption (BFR), which results in disfigurement as well as loss of the protective covering of the brain. This study investigates risk factors for BFR after AC, including medical conditions and antihypertensive drug therapies, with a focus on angiotensin-converting enzyme inhibitors (ACEIs), which have been associated with a beneficial effect on bone healing and bone preservation in orthopedic, osteoporosis, and endocrinology research.

METHODS

In this single-center, retrospective study 183 consecutive cases were evaluated for bone flap resorption after AC. Information on patient demographics, medical conditions, antihypertensive therapy, and BFR—defined as an indication for revision surgery established by a neurosurgeon based on clinical or radiographic assessments—was collected. A Kaplan-Meier analysis of time from AC to diagnosis of BFR was performed, and factors associated with BFR were investigated using the log-rank test and Cox regression.

RESULTS

A total of 158 patients were considered eligible for inclusion in the data analysis. The median follow-up time for this group was 2.2 years (95% CI 1.9–2.5 years). BFR occurred in 47 patients (29.7%), with a median time to event of 3.7 years (95% CI 3.3–4.1 years). An ACEI prescription was recorded in 57 cases (36.1%). Univariate Kaplan-Meier analysis and the log-rank test revealed that ACEI therapy (2-year event free probability [EFP] 83.8% ± 6.1% standard error vs 63.9% ± 5.6%, p = 0.02) and ventriculoperitoneal (VP) shunt treatment (2-year EFP 86.9% ± 7.1% vs 66% ± 5.0%, p = 0.024) were associated with a lower probability of BFR. Multiple Cox regression analysis showed ACEI therapy (HR 0.29, p = 0.012), VP shunt treatment (HR 0.278, p = 0.009), and male sex (HR 0.500, p = 0.040) to be associated with a lower risk for BFR, whereas bone fragmentation (HR 1.92, p = 0.031) was associated with a higher risk for BFR.

CONCLUSIONS

Hypertensive patients treated with ACEIs demonstrate a lower rate of BFR than patients treated with other hypertensive medications and nonhypertensive patients. Our results are in line with previous reports on the positive influence of ACEIs on bone healing and preservation. Further analysis of the association between ACEI treatment and BFR development is needed and will be evaluated in a multicenter prospective trial.

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Erdem Güresir, Hartmut Vatter, Patrick Schuss, Ági Oszvald, Andreas Raabe, Volker Seifert and Jürgen Beck

Object

The object of this study was to describe the rapid closure technique in decompressive craniectomy without duraplasty and its use in a large cohort of consecutive patients.

Methods

Between 1999 and 2008, supratentorial rapid closure decompressive craniectomy (RCDC) was performed 341 times in 318 patients at the authors' institution. Cases were stratified as 1) traumatic brain injury, 2) subarachnoid hemorrhage, 3) intracerebral hemorrhage, 4) cerebral infarction, and 5) other. A large bone flap was removed and the dura mater was opened in a stellate fashion. Duraplasty was not performed—that is, the dura was not sutured, and a dural substitute was neither sutured in nor layed on. The dura and exposed brain tissue were covered with hemostyptic material (Surgicel). Surgical time and complications of this procedure including follow-up (> 6 months) were recorded. After 3–6 months cranioplasty was performed, and, again, surgical time and any complications were recorded.

Results

Rapid closure decompressive craniectomy was feasible in all cases. Complications included superficial wound healing disturbance (3.5% of procedures), abscess (2.6%) and CSF fistula (0.6%); the mean surgical time (± SD) was 69 ± 20 minutes. Cranioplasty was performed in 196 cases; the mean interval (± SD) from craniectomy to cranioplasty was 118 ± 40 days. Complications of cranioplasty included epidural hematoma (4.1%), abscess (2.6%), wound healing disturbance (6.1%), and CSF fistula (1%).

Compared with the results reported in the literature for decompressive craniectomy with duraplasty followed by cranioplasty, there were no significant differences in the frequency of complications. However, surgical time for RCDC was significantly shorter (69 ± 20 vs 129 ± 43 minutes, p < 0.0001).

Conclusions

The present analysis of the largest series reported to date reveals that the rapid closure technique is feasible and safe in decompressive craniectomy. The surgical time is significantly shorter without increased complication rates or additional complications. Cranioplasty after a RCDC procedure was also feasible, fast, safe and not impaired by the RCDC technique.

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Raphael Meier, Nicole Porz, Urspeter Knecht, Tina Loosli, Philippe Schucht, Jürgen Beck, Johannes Slotboom, Roland Wiest and Mauricio Reyes

OBJECTIVE

In the treatment of glioblastoma, residual tumor burden is the only prognostic factor that can be actively influenced by therapy. Therefore, an accurate, reproducible, and objective measurement of residual tumor burden is necessary. This study aimed to evaluate the use of a fully automatic segmentation method—brain tumor image analysis (BraTumIA)—for estimating the extent of resection (EOR) and residual tumor volume (RTV) of contrast-enhancing tumor after surgery.

METHODS

The imaging data of 19 patients who underwent primary resection of histologically confirmed supratentorial glioblastoma were retrospectively reviewed. Contrast-enhancing tumors apparent on structural preoperative and immediate postoperative MR imaging in this patient cohort were segmented by 4 different raters and the automatic segmentation BraTumIA software. The manual and automatic results were quantitatively compared.

RESULTS

First, the interrater variabilities in the estimates of EOR and RTV were assessed for all human raters. Interrater agreement in terms of the coefficient of concordance (W) was higher for RTV (W = 0.812; p < 0.001) than for EOR (W = 0.775; p < 0.001). Second, the volumetric estimates of BraTumIA for all 19 patients were compared with the estimates of the human raters, which showed that for both EOR (W = 0.713; p < 0.001) and RTV (W = 0.693; p < 0.001) the estimates of BraTumIA were generally located close to or between the estimates of the human raters. No statistically significant differences were detected between the manual and automatic estimates. BraTumIA showed a tendency to overestimate contrast-enhancing tumors, leading to moderate agreement with expert raters with respect to the literature-based, survival-relevant threshold values for EOR.

CONCLUSIONS

BraTumIA can generate volumetric estimates of EOR and RTV, in a fully automatic fashion, which are comparable to the estimates of human experts. However, automated analysis showed a tendency to overestimate the volume of a contrast-enhancing tumor, whereas manual analysis is prone to subjectivity, thereby causing considerable interrater variability.

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Levin Häni, Sonja Vulcu, Mattia Branca, Christian Fung, Werner Josef Z’Graggen, Michael Murek, Andreas Raabe, Jürgen Beck and Philippe Schucht

OBJECTIVE

The use of subdural drains after surgical evacuation of chronic subdural hematoma (CSH) decreases the risk of recurrence and has become the standard of care. Halfway through the controlled, randomized TOSCAN (Randomized Trial of Follow-up CT after Evacuation of Chronic Subdural Hematoma) trial, the authors’ institutional guidelines changed to recommend subgaleal instead of subdural drainage. The authors report a post hoc analysis on the influence of drain location in patients participating in the TOSCAN trial.

METHODS

The study involved 361 patients enrolled in the TOSCAN trial. The patients were stratified according to whether they received surgery before (cohort A) or after (cohort B) the change in institutional protocol. An intention-to-treat analysis was performed with surgery for recurrence as the primary endpoint. Secondary endpoints were outcome-based on modified Rankin Scale scores, seizures, infections, parenchymal brain injuries, and hematoma diameter.

RESULTS

Of the 361 patients included in the analysis, 214 were stratified into cohort A (subdural drainage recommended), while 147 were stratified into cohort B (subgaleal drainage recommended). There was a 31.78% rate of crossover from the subdural to the subgaleal drainage insertion site due to technical or anatomical difficulties. No differences in the rates of reoperation (21.5% [cohort A] vs 25.17% [cohort B], OR 0.81, 95% CI 0.50–1.34, p = 0.415), infections (0.47% [cohort A] vs 2.04% [cohort B], OR 0.23, 95% CI 0.02–2.19, p = 0.199), seizures (3.27% [cohort A] vs 2.72% [cohort B], OR 1.21, 95% CI 0.35–4.21, p = 0.765), or favorable outcomes (modified Rankin Scale score 0–3) at 1 and 6 months (91.26% [cohort A] vs 96.43% [cohort B], OR 0.39, 95% CI 0.14–1.07, p = 0.067; 89.90% [cohort A] vs 91.55% [cohort B], OR 0.82, 95% CI 0.39–1.73, p = 0.605) were noted between the two cohorts. Postoperatively, patients in cohort A had more frequent parenchymal brain tissue injuries (2.8% vs 0%, p = 0.041). Postoperative absolute and relative hematoma reduction was similar irrespective of the location of the drain.

CONCLUSIONS

Subgaleal rather than subdural placement of the drain did not increase the risk for reoperation for recurrence of CSHs, nor did it have a negative impact on clinical or radiological outcome. The intention to place a subdural drain was associated with a higher rate of parenchymal injuries.

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Serge Marbacher, Janine-Ai Schläppi, Christian Fung, Jürg Hüsler, Jürgen Beck and Andreas Raabe

Object

Recent studies in rats have demonstrated that statins may have an inhibitory effect on intracranial aneurysm (IA) development. The purpose of this study was to assess whether long-term statin use is associated with a reduced risk of IA formation in humans.

Methods

This was a single-center case-control study that included consecutive patients admitted to the authors' institution between January 1, 2005, and December 31, 2008. A case was defined as a patient with a cerebral angiography–confirmed diagnosis of IA. Three controls were matched to each case based on age, sex, and index year of hospital admission. The primary exposure of interest was cumulative statin use. Conditional logistic regression was used to assess the relationship between statin intake and incidence of IA.

Results

In total, 1200 patients were included in the study. No overall association was found between statin use and incidence of IA formation (OR 1.08, 95% CI 0.69–1.69), nor when dichotomized into hydrophilic and lipophilic user, or between short (≤12-month) and long (≥36-month) duration of intake. Hypertension and smoking significantly increased the risk of IA development (OR 4.02, 95% CI 2.49–6.45, and OR 1.67, 95% CI 1.02–2.72, respectively).

Conclusions

In contrast to recent experimental reports of the association between statins and a reduction of IA formation, the authors' findings suggest that in humans statins may have no significant beneficial effect on IA suppression.

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Michael Fiechter, Jens Fichtner, Sergej Feiler, Radu Olariu, Jürgen Beck, Andreas Raabe and Christian T. Ulrich