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Katharina Faust and Peter Vajkoczy

OBJECT

Visual field defects (VFDs) due to optic radiation (OR) injury are a common complication of temporal lobe surgery. The authors analyzed whether preoperative visualization of the optic tract would reduce this complication by influencing the surgeon’s decisions about surgical approaches. The authors also determined whether white matter shifts caused by temporal lobe tumors would follow predetermined patterns based on the tumor’s topography.

METHODS

One hundred thirteen patients with intraaxial tumors of the temporal lobe underwent preoperative diffusion tensor imaging (DTI) fiber tracking. In 54 of those patients, both pre- and postoperative VFDs were documented using computerized perimetry. Brainlab’s iPlan 2.5 navigation software was used for tumor reconstruction and fiber visualization after the fusion of DTI studies with their respective magnetization-prepared rapid gradient-echo (MP-RAGE) images. The tracking algorithm was as follows: minimum fiber length 100 mm, fractional anisotropy threshold 0.1. The lateral geniculate body and the calcarine cortex were employed as tract seeding points. Shifts of the OR caused by tumor were visualized in comparison with the fiber tracking of the patient’s healthy hemisphere.

RESULTS

Temporal tumors produced a dislocation of the OR but no apparent fiber destruction. The shift of white matter tracts followed fixed patterns dependent on tumor location: Temporolateral tumors resulted in a medial fiber shift, and thus a lateral transcortical approach is recommended. Temporopolar tumors led to a posterior shift, always including Meyer’s loop; therefore, a pterional transcortical approach is recommended. Temporomesial tumors produced a lateral and superior shift; thus, a transsylvian-transcisternal approach will result in maximum sparing of the fibers. Temporocentric tumors also induced a lateral fiber shift. For those tumors, a transsylvian-transopercular approach is recommended. Tumors of the fusiform gyrus generated a superior (and lateral) shift; consequently, a subtemporal approach is recommended to avoid white matter injury. In applying the approaches recommended above, new or worsened VFDs occurred in 4% of the patient cohort. Total neurological and surgical morbidity were less than 10%. In 90% of patients, gross-total resection was accomplished.

CONCLUSIONS

Preoperative visualization of the OR may help in avoiding postoperative VFDs.

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Johannes Woitzik, Peter Horn, Peter Vajkoczy and Peter Schmiedek

Object. Recently, intraoperative fluorescence angiography in which indocyanine green (ICG) is used as a tracer has been introduced as a novel technique to confirm successful aneurysm clipping. The aim of the present study was to assess whether ICG videoangiography is also suitable for intraoperative confirmation of extracranial—intracranial bypass patency.

Methods. Forty patients undergoing cerebral revascularization for hemodynamic cerebral ischemia (11 patients), moyamoya disease (18 patients), or complex intracranial aneurysms (11 patients) were included. Superficial temporal artery (STA)—middle cerebral artery (MCA) bypass surgery was performed 35 times in 30 patients (five patients with moyamoya underwent bilateral procedures), STA—posterior cerebral artery bypass surgery in two patients, and saphenous vein (SV) high-flow bypass surgery in eight patients. In each patient, following the completion of the anastomosis, ICG (0.3 mg/kg body weight) was given systemically via an intravenous bolus injection. A near-infrared light emitted by laser diodes was used to illuminate the operating field and the intravascular fluorescence was recorded using an optical filter—equipped video camera. The findings of ICG videoangiography were compared with those of postoperative digital subtraction (DS) or computerized tomography (CT) angiography.

In all cases excellent visualization of cerebral arteries, the bypass graft, and brain perfusion was noted. Indocyanine green videoangiography was used to identify four nonfunctioning STA—MCA bypasses, which could be revised successfully in all cases. In two cases of SV high-flow bypasses, ICG videoangiography revealed stenosis at the proximal anastomotic site, which was also revised successfully. In all cases the final findings of ICG videoangiography could be positively validated during the postoperative course by performing DS or CT angiography.

Conclusions. Indocyanine green videoangiography provides a reliable and rapid intraoperative assessment of bypass patency. Thus, ICG videoangiography may help reduce the incidence of early bypass graft failure.

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Marcus Czabanka, Peter Vajkoczy, Peter Schmiedek, and Peter Horn

Object

Different revascularization procedures are used in the treatment of patients with moyamoya disease (MMD). The aim of this study was to investigate the relative contribution of direct and indirect revascularization procedures to the restoration of collateral blood supply in adult and pediatric patients with MMD.

Methods

The authors performed 39 combined cerebral revascularization procedures (standard extraintracranial bypass [STA-MCA bypass] plus encephalomyosynangiosis [EMS]) in 10 pediatric and 10 adult patients. All patients underwent physical examination and digital subtraction angiography before and 6 months after surgery. The STA-MCA bypass and EMS function were graded as Grade I (poor), II (moderate), or III (good) on the basis of the angiograms.

Results

In pediatric patients, bypass function was Grade I in 12, Grade II in 8, and Grade III in 0 hemispheres; EMS function was Grade I in 0, Grade II in 12, and Grade III in 8 hemispheres. In the adult patients, bypass function was Grade I in 8, Grade II in 8, and Grade III in 3 hemispheres; EMS function was Grade I in 10 hemispheres, Grade II in 5, and Grade III in 1 hemisphere. In the pediatric patients disease was classified as improved in 14 hemispheres on the basis of clinical results and stable in 6. In the adults it was classified as improved in 12 hemispheres stable in 7 hemispheres.

Conclusions

Combined revascularization led to good angiographic and clinical results in both patient populations. Especially in pediatric patients, EMS represents a suitable alternative to bypass surgery.

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Peter Vajkoczy, Peter Horn, Claudius Thome, Elke Munch and Peter Schmiedek

Object. The goal of this study was to evaluate regional cerebral blood flow (rCBF) monitoring, performed using thermal-diffusion (TD) flowmetry, as a novel means for the bedside diagnosis of symptomatic vasospasm.

Methods. Fourteen patients with high-grade subarachnoid hemorrhage (SAH) who underwent early clip placement for anterior circulation aneurysms were prospectively entered into the study. Thermal-diffusion microprobes were implanted into the white matter of vascular territories that were deemed at risk for developing symptomatic vasospasm. Data on arterial blood pressure, intracranial pressure, cerebral perfusion pressure, rCBF measurement obtained using a TD probe (TD-rCBF), cerebrovascular resistance (CVR), and blood flow velocities were collected at the patient's bedside. The diagnosis of symptomatic vasospasm was based on the manifestation of a delayed ischemic neurological deficit and/or a reduced territorial level of CBF as assessed using stable Xe-enhanced computerized tomography (CT) scanning in combination with vasospasm demonstrated by angiography.

Bedside monitoring of TD-rCBF and CVR allowed the detection of symptomatic vasospasm. In the 10 patients with vasospasm the TD-rCBF decreased from 21 ± 4 to 9 ± 1 ml/100 g/min (mean ± standard error of the mean), whereas in the four other patients the TD-rCBF value remained unchanged (mean TD-rCBF = 25 ± 4 compared with 21 ± 4 ml/100 g/min). A comparison of the results of TD-rCBF and Xe-enhanced CT studies, as well as the calculation of sensitivities, specificities, predictive values, and likelihood ratios, identified a TD-rCBF value of 15 ml/100 g/min as a reliable cutoff for the diagnosis of symptomatic vasospasm. In addition, TD flowmetry was characterized by a more favorable diagnostic reliability than transcranial Doppler ultrasonography.

Conclusions. Thermal-diffusion flowmetry represents a promising method for the bedside monitoring of patients with SAH to detect symptomatic vasospasm. This is of major clinical interest for patients with high-grade SAH, who often cannot be assessed neurologically.

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Fabienne Perren, Peter Horn, Peter Vajkoczy, Peter Schmiedek and Stephen Meairs

Object. Moyamoya is a rare, chronic disease that leads to the progressive narrowing and/or occlusion of the distal internal carotid and proximal cerebral arteries. Chronic cerebral ischemia ensues due to insufficient collateral blood supply. One potential treatment consists of the restoration of regional cerebral blood flow by direct or indirect revascularization surgery. The extent of neovascularization, especially in indirect procedures such as encephalomyosynangiosis (EMS), is currently evaluated with conventional angiography. Because this method is invasive and carries some risks, the authors investigated power Doppler imaging as an alternative noninvasive bedside procedure that can be used to assess surgically induced indirect revascularization in adult patients with moyamoya disease.

Methods. Twelve symptomatic patients with adult moyamoya disease (seven women and five men, mean age 38 ± 17 years) underwent combined (direct and indirect) revascularization. They were then examined using conventional angiography and power Doppler imaging to assess the extent of revascularization within 120 days postsurgery. According to the number of intracranial vessels demonstrating opacification on conventional angiography and power Doppler imaging studies, EMS was graded as follows: 1, absent (0 vessels); 2, moderate (one—four vessels); and 3, extensive (> four vessels) for both methods. Examiners were blinded to the classification results for the procedure that they did not grade.

All 24 hemispheres were examined. The visual grading of EMS revealed a highly significant agreement between conventional angiography and power Doppler imaging (Spearman rank coefficient, r = 0.92; p < 0.001) and there was 100% agreement of patency of the bypass between the direct and indirect methods.

Conclusions. The authors found excellent agreement between the two methods. Therefore, power Doppler imaging is a valid noninvasive alternative to carotid artery angiography in evaluating direct and indirect revascularization.

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Satoshi Takahashi, Peter Vajkoczy and Thomas Picht

Object

Navigated transcranial magnetic stimulation (nTMS) is a novel technology in the field of neurosurgery for noninvasive delineation of cortical functional topography. This study addresses the spatial accuracy and clinical usefulness of nTMS in brain tumor surgery in or near the motor cortex based on a systematic review of observational studies.

Methods

A systematic search retrieved 11 reports published up to October 2012 in which adult patients were examined with nTMS prior to surgery. Quality criteria consisted of documentation of the influence of nTMS brain mapping on clinical decision making in a standardized prospective manner and/or performance of intraoperative direct electrical stimulation (DES) and comparison with nTMS results. Cross-observational assessment of nTMS accuracy was established by calculating a weighted mean distance between nTMS and DES.

Results

All studies reviewed in this article concluded that nTMS correlated well with the “gold standard” of DES. The mean distance between motor cortex identified on nTMS and DES by using the mean distance in 81 patients described in 6 quantitatively evaluated studies was 6.18 mm. The nTMS results changed the surgical strategy based on anatomical imaging alone in 25.3% of all patients, based on the data obtained in 87 patients in 2 studies.

Conclusions

The nTMS technique spatially correlates well with the gold standard of DES. Its functional information benefits surgical decision making and changes the treatment strategy in one-fourth of cases.

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Theodoros Kombos, Olaf Süss and Peter Vajkoczy

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.

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Julius Dengler, Naoki Kato and Peter Vajkoczy

Large and giant anterior communicating artery (ACoA) aneurysms usually show partial thrombosis and incorporate both the A1 and A2 segments and crucial perforating vessels. Therefore, direct clip placement or endovascular strategies often fail, leaving cerebral bypass surgery as a relevant therapeutic option. The authors present 3 cases in which a giant or large ACoA aneurysm was successfully occluded using a new technique that applies a double-barrel radial artery bypass. A radial artery graft is modified into a Y-shaped double-barrel conduit. After both pterional and parasagittal craniotomies are carried out, the graft is tunneled between both sites and anastomosed in an end-to-side fashion proximally to either a superficial temporal artery (STA) or M2 branch and distally to bilateral A3 branches. Aneurysm occlusion is then conducted through the pterional or parasagittal craniotomy. In one case, a 42-year-old patient in whom an endovascular approach had failed, the authors performed an STA-A3-A3 bypass and proximal aneurysm occlusion. In two others, a 49-year-old man in whom coiling had failed and a 56-year-old man in whom a giant ACoA aneurysm was partially thrombosed, the authors performed an M2-A3-A3 double-barrel bypass followed by either proximal or distal aneurysm occlusion. Complete aneurysm occlusion with excellent bypass perfusion was documented in the first two cases. In the third case, the authors observed good bypass perfusion with persistent antegrade aneurysm filling, and thus endovascular coil embolization was added to completely occlude the aneurysm.

The Y-shaped double-barrel bypass using a radial artery graft allows for safe and effective occlusion of large and giant ACoA aneurysms that cannot be treated by direct clip application.

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Julia Onken, Bernhard Meyer and Peter Vajkoczy

OBJECTIVE

Cervical artificial disc replacement (C-ADR) is a widely used procedure with low risk at implantation. Few cases have been reported about the surgical techniques of C-ADR revision. The authors describe their surgical experience with the explantation of a Galileo C-ADR.

METHODS

Revision surgery was performed in a 58-year-old patient. Patient positioning and surgical opening techniques were performed as appropriate for anterior cervical decompression.

RESULTS

Revision surgery via the initial anterior approach was successful following an atraumatic removal of the implant. Fusion of the C5–6 segment was performed without complications.

CONCLUSIONS

In general, the authors observed recurrent nerve palsy and malpositioning of the revised implant in C-ADR revision surgery. Problems with implant removal did not occur because the fusion rate was low due to the short time between initial surgery and C-ADR revision surgery.

The video can be found here: https://youtu.be/32CUEDquinc.

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Claudius Thomé, Peter Vajkoczy, Peter Horn, Christian Bauhuf, Ulrich Hübner and Peter Schmiedek

Object. Temporary arterial occlusion (TAO) during aneurysm surgery carries the risk of ischemic sequelae. Because monitoring of regional cerebral blood flow (rCBF) may limit neurological damage, the authors evaluated a novel thermal diffusion (TD) microprobe for use in the continuous and quantitative assessment of rCBF during TAO.

Methods. Following subcortical implantation of the device at a depth of 20 mm in the middle cerebral artery or anterior cerebral artery territory, rCBF was continuously monitored by TD microprobe (TD-rCBF) throughout surgery in 20 patients harboring anterior circulation aneurysms; 46 occlusive episodes were recorded. Postoperative radiographic evidence of new infarction was used as the threshold for failure of occlusion tolerance.

The mean subcortical TD-rCBF decreased from 27.8 ± 8.4 ml/100 g/min at baseline to 13.7 ± 11.1 ml/100 g/min (p < 0.0001) during TAO. The TD microprobe showed an immediate exponential decline of TD-rCBF on clip placement. On average, 50% of the total decrease was reached after 12 seconds, thus rapidly indicating the severity of hypoperfusion. Following clip removal, TD-rCBF returned to baseline levels after an average interval of 32 seconds, and subsequently demonstrated a transient hyperperfusion to 41.4 ± 18.3 ml/100 g/min (p < 0.001). The occurrence of postoperative infarction (15%) and the extent of postischemic hyperperfusion correlated with the depth of occlusion-induced ischemia.

Conclusions. The new TD microprobe provides a sensitive, continuous, and real-time assessment of intraoperative rCBF during TAO. Occlusion-induced ischemia is reliably detected within the 1st minute after clip application. In the future, this may enable the surgeon to alter the surgical strategy early after TAO to prevent ischemic brain injury.