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Axel Perneczky and Georg Fries

✓ When operating on deep-seated cerebral aneurysms, the surgeon's visual control of clip application may be impaired by the clip holder unless adjacent structures are retracted. To improve visual control and reduce the necessity for retraction, the senior author (A.P.) developed a new concept: an aneurysm clip with an inverted-spring mechanism. The clip has two jaws that point away from the clip blades. The jaws of the clip holder articulate with the inner side of the clip jaws. By distending the jaws of the clip holder the blades of the clip are opened and vice versa. Thus the visual field increases while the clip application is proceeding. This instrumentation is useful, especially in cases of deep-seated aneurysms arising from the posterior circulation and in multiple aneurysms. In these latter cases even lesions located contralaterally could be reached with good visual control.

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Georg Fries, Axel Perneczky and Oliver Kempski

✓ Monocytes/macrophages frequently infiltrate malignant gliomas and play a central role in the tumor-associated immune response as they process tumor antigen and present it to T-lymphocytes. Findings have accumulated that peripheral blood monocytes leaving the cerebral circulation become microglial cells and vice versa and that monocytes/macrophages may stimulate malignant tumor growth by some unknown mechanism. Most malignant gliomas express growth factor receptors, for example epidermal growth factor receptor (EGFR). The aim of this study was to determine whether peripheral blood monocytes of glioma patients release EGF, the appropriate ligand of gliomacell membrane-bound EGFR.

Long-term cultured peripheral blood monocytes from 14 patients with malignant gliomas were compared to those from 12 controls (seven with nontumorous disease and five healthy individuals). Using an enzyme-linked immunosorbent assay for EGF, the EGF content of cell culture supernatants was determined at Days 7, 21, and 100 of culture. The EGF content (mean ± standard error) of supernatants was 5.9 ± 0.2 pg/ml/103 glioma monocytes versus 1.3 ± 0.1 pg/ml/103 control monocytes at Day 7 of culture, 22.9 ± 0.8 pg/ml/103 glioma monocytes versus 1.8 ± 0.9 pg/ml/103 control monocytes at Day 21 of culture, and 23.4 ± 0.7 pg/ml/103 glioma monocytes, and below detection levels for control monocytes at Day 100 of culture. Steroid treatment of glioma patients did not influence the EGF release of cultured monocytes. These data indicate that glioblastoma-associated peripheral blood monocytes may be distinct from those of healthy individuals. Moreover, this study indicates that subtypes of glioma-associated peripheral blood monocytes may support immunosuppression and promote growth of malignant glioma by releasing unusually high amounts of EGF.

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Islam Gawish, Robert Reisch and Axel Perneczky

Object. Neuroendoscopy has an essential role in the management of occlusive hydrocephalus due to a membranous obstruction of the sylvian aqueduct. Well-known endoscopic methods include endoscopic third ventriculostomy (ETV) and endoscopic aqueductoplasty through a frontal burr hole. Building on their experience in the endoscopic management of hydrocephalus, the authors realized that not all of their patients with aqueductal obstruction were eligible for the aforementioned lines of treatment. Certain anatomical situations made it impossible to perform ETV or endoscopic aqueductoplasty through a frontal burr hole. Long-term complications of the shunt system led the authors to seek an alternative form of treatment for these patients. In this study, they present a new endoscopic approach to performing aqueductoplasty through the fourth ventricle.

Methods. Endoscopic aqueductoplasty was performed in five patients by using a tailored craniocervical approach. In all patients a caudally located membranous obstruction of the sylvian aqueduct was present, and the authors were able to relieve the membranous obstruction in all patients without complications. All patients experienced improvement, which was demonstrated clinically and on imaging studies.

Conclusions. Caudal endoscopic aqueductoplasty is a safe and effective method of treatment in the management of a caudally located membranous obstruction of the sylvian aqueduct. This should be considered as an alternative endoscopic method when other endoscopic solutions are not suitable.

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Johannes Mäurer, Elisabeth Mäurer and Axel Perneczky

✓ Two patients with rare variations of the A1 segment of the anterior cerebral artery are presented. One patient had a perforation of the optic tract by an abnormal course of the A1 segment, and the other harbored an aneurysm of the A1 segment running below the optic nerve. The authors present a summary of A1 segment variations described in the literature.

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Georg Fries, Thomas Wallenfang, Johannes Hennen, Markus Velthaus, Axel Heimann, Hans Schild, Axel Perneczky and Oliver Kempski

✓ Cerebral sinus-vein thrombosis may lead to severe hemodynamic changes, elevated intracranial pressure (ICP), and brain edema. It is supposed that progression of the thrombus from the sinus into bridging and cortical veins plays a key role in the development of these pathophysiological changes, but this hypothesis lacks experimental proof. The aim of this study, using a novel animal model of sinus-vein thrombosis, was to evaluate the effects of a standardized occlusion of the superior sagittal sinus and its bridging and cortical veins on hemodynamic alterations, on brain water content, and on ICP in domestic pigs.

In 10 animals, the middle third of the superior sagittal sinus was occluded with a catheter-guided balloon. Five of these pigs received an additional injection of 1 ml fibrin glue into the superior sagittal sinus anterior to the inflated balloon, leading to an obstruction of bridging and cortical veins. In five control animals the balloon was inserted but not inflated. Five pigs underwent cerebral angiography. Four hours after occlusion, the brains were frozen in liquid nitrogen, and coronal slices were examined for Evans blue dye extravasation, regional water content, and histological changes.

Occlusion of the superior sagittal sinus alone did not affect ICP or cerebral perfusion pressure (CPP). The additional injection of fibrin glue caused an obstruction of cortical and bridging veins as well as severe increases in mean (± standard deviation) ICP to 49.4 ± 14.3 mm Hg, compared with 8.3 ± 4.5 mm Hg in sham-treated controls and 7.1 ± 3.9 mm Hg in animals with occlusion of the superior sagittal sinus alone. There was also a steep fall in the mean CPP to 34.2 ± 19.6 mm Hg compared with 96.4 ± 13.8 mm Hg in the control group.

White-matter water content anterior to the occlusion site was elevated to 81.9 ± 3.7 gm/100 gm frozen weight in the fibrin group as compared to 70.7 ± 2.2 gm/100 gm in controls. Posterior to the occlusion site, water content did not differ among the three groups. Angiography demonstrated collateral flow via cortical and bridging veins in animals with occlusion of the superior sagittal sinus alone. Additional fibrin glue obstructed these collateral vessels.

The data suggest a multistep process of pathophysiological alterations in patients with sinus-vein thrombosis and may explain why these patients present with a wide variety of symptoms: minor neurological deficits or headache might indicate thrombosis of the superior sagittal sinus and/or its bridging veins. In subjects with severe symptoms, coma, and increased ICP there may be an additional involvement of tributary cortical veins. The proposed multistep process offers the rationale for heparin treatment of sinus-vein thrombosis even in patients with minor symptoms.

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Dorothee Koch-Wiewrodt, Wolfgang Wagner and Axel Perneczky

✓Laminectomy is the most conventional dorsal approach to intraspinal space-occupying lesions and may result in gradually increasing instability or deformity of the vertebral column. Less invasive procedures such as hemilaminectomy and osteoplastic laminotomy have been described by other authors, but an approach that interferes with spinal stability to an even lesser extent seems desirable.

In an attempt to further reduce the need for bone removal, the authors used interlaminar fenestration (mostly unilateral) at one or more spinal levels to remove intramedullary, extramedullary, or extradural lesions, and even some lesions that extended over several spine segments. The authors present their experiences with this surgical approach in 78 patients harboring different intraspinal lesions. Up to 16 segments were fenestrated in one patient. Complete removal of the lesion was possible in most patients, and no postoperative spinal instabilities were observed in up to 8 years of follow up. Multilevel interlaminar fenestration, also called “multiple spinal keyhole surgery,” is a feasible, safe, and effective approach to intraspinal lesions.

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Wolfgang Wagner, Lydia Peghini-Halbig, Johannes C. Mäurer and Axel Perneczky

✓ The results of intraoperative monitoring of median nerve somatosensory evoked potentials (SEP's) were evaluated in 75 neurosurgical patients in order to assess the role of differential derivation of brain stem (P14) and spinal cord (N13) wave activity. These components were compared with the conventionally recorded neck potential (“N13”) that reflects overlap of P14 and N13. The spinal cord N13 wave was recorded from the posterior to anterior lower aspect of the neck and the brain stem P14 wave from the midfrontal scalp to the nasopharynx; both derivations enabled isolated low-artifact recording of these components. In 18.7% of patients, moderate to major latency and/or amplitude shifts of N13 or P14 were found that were masked in conventional neck-scalp recordings of “N13”. There was a 6.7% false-negative rate in this series. Using a neck-scalp derivation alone, a 14.7% false-negative rate would have resulted and an isolated worsening of the P14 component (with stable neck potential) in six cases would have been overlooked. It is concluded that the proposed SEP recording technique allows independent assessment of spinal cord and brain stem activity. It is, therefore, superior to the conventional neck-scalp derivation technique, in which important information may be concealed or even lost due to the overlap of the brain stem P14 and spinal cord N13 potentials.

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Jens Conrad, Stefan Welschehold, Patra Charalampaki, Erik van Lindert, Peter Grunert and Axel Perneczky

Object

Primary intracranial ependymal cysts are extremely rare. Similar to congenital intraparenchymal cysts in the mesencephalon they usually occur with symptoms of an occlusive hydrocephalus or symptoms like Parinaud syndrome, dizziness, or gait disturbance. The objective of this study was to evaluate the surgical methods for the treatment of these cysts and the clinical outcome of the patients.

Methods

The authors present the clinical records of 8 patients who were treated in their department for symptomatic mesencephalic ependymal cysts in the past 10 years. The patient age ranged from 22 to 60 years with a mean age of 44 years. In 4 cases the authors performed a suboccipital infratentorial supracerebellar approach by using endoscope-assisted microsurgery. The other 4 patients underwent a pure endoscopic procedure over a frontal bur hole trepanation.

Results

Four patients became symptom free, and the remaining 4 improved significantly after a mean follow-up duration of 38.5 months (range 5–119 months). One patient underwent 2 operations: first a ventriculocystostomy and 4 months later endoscopic third ventriculostomy because of recurrent hydrocephalus. In 1 case a second surgery was necessary because of a wound infection. In all of the patients an adequate fenestration of the cyst was achieved.

Conclusions

A symptomatic mesencephalic ependymal cyst is an indication for neurosurgical intervention. These cysts can be treated successfully and most likely definitively by a pure endoscopic or endoscope-assisted keyhole neurosurgical technique. There were no morbid conditions or death due to the procedures in this group of 8 patients. Therefore, the authors regard these surgical procedures to be good alternatives to treatments such as shunt placement or stereotactic aspiration of the cysts.

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Axel Thomas Stadie, Ralf Alfons Kockro, Robert Reisch, Andrei Tropine, Stephan Boor, Peter Stoeter and Axel Perneczky

Object

The authors report on their experience with a 3D virtual reality system for planning minimally invasive neurosurgical procedures.

Methods

Between October 2002 and April 2006, the authors used the Dextroscope (Volume Interactions, Ltd.) to plan neurosurgical procedures in 106 patients, including 100 with intracranial and 6 with spinal lesions. The planning was performed 1 to 3 days preoperatively, and in 12 cases, 3D prints of the planning procedure were taken into the operating room. A questionnaire was completed by the neurosurgeon after the planning procedure.

Results

After a short period of acclimatization, the system proved easy to operate and is currently used routinely for preoperative planning of difficult cases at the authors' institution. It was felt that working with a virtual reality multimodal model of the patient significantly improved surgical planning. The pathoanatomy in individual patients could easily be understood in great detail, enabling the authors to determine the surgical trajectory precisely and in the most minimally invasive way.

Conclusions

The authors found the preoperative 3D model to be in high concordance with intraoperative conditions; the resulting intraoperative “déjà-vu” feeling enhanced surgical confidence. In all procedures planned with the Dextroscope, the chosen surgical strategy proved to be the correct choice.

Three-dimensional virtual reality models of a patient allow quick and easy understanding of complex intracranial lesions.