S26 Abstracts of the Hydrocephalus 2008 Congress / Clinical Neurology and Neurosurgery 110S (2008), S1–S41 The measurement principle of the sensor exploits conductance differences between the cerebrospinal fluid and the brain tissue. Experiments with prototype sensors accurately predicted the volume content of elastically deformable membranes and gel phantoms mimicking the conductance prop- erties of the human brain. The volume-conductance correlation detected by the sensor in brain phantoms was validated in dog brain tissue. The sensor was incorporated into a fully automatic feedback control system designed to maintain the volume contained inside of pathological parameters. The experimental conductance properties were also used to assess the sensor performance in a simulated case of hydrocephalus. The computer analysis predicted voltage drops over the range of size increases in human ven- triculomegaly and showed only mild positional dependence of the sensor electrodes inside the ventricular space. These promising experimental and computational results of the novel impedance sensor with the new feedback control system could serve as the foundation for improved therapy for hydrocephalic patients which monitors volume and then actively provides feedback control. O.097 The usage of new ultrasonic microprobe in neuroendoscopy H. Jednacak 1 , J. Paladino 1 , P. Miklic 1 , M. Vukic 1 , M. Klarica 2 1 Department of Neurosurgery, School of Medicine, University of Zagreb, Zagreb, Croatia; 2 Croatian Institute for Brain Research, Zagreb, Croatia The role of endoscopic procedures in adult and pediatric neurosurgery is rapidly growing, not only for the treatment of different obstructive hydrocephalus forms, but also for the other indications: various intracranial cysts and intraventricular space occupying lesions. The usage of different neuroendosopic techniques and instruments (blunt perforation, endoscopic scissors and forceps, mono and bipolar electrocoagulation and laser) clearly demonstrates unsufficiency of the existing neuroendoscopic armamentar- ium. We report our experience with originally constructed Neurosurgical Endoscope Contact Ultrasound Probe “NECUP-2” in neuroendoscopy. The newly developed “NECUP-2” consists of the ultrasound generator (ampli- tude 300 μm, intensity 900 W/cm 2 , acceleration 400000 m/s2, frequency 25000 Hz), and titanium microprobe with 1.6 mm diameter which easily passes through the 2.2 mm ventriculoscope working channel. The ultra- sound intensity can be changed from low to high, enabling tissue perforation and removal with preserving of the vascular structures. Between June 1997 and June 2007, 132 neuroendoscopic procedures have been performed: 102 ETV, 10 septotomies, 15 arachnoid cysts and 5 intraventricular tumors. The “NECUP-2” was applied effectively in all cases in which blunt perofration was not possible: 38/102 ETV, 10/10 septostomies, 15/15 arachnoid cysts. In the five cases of intraventricular tumors neuroendosopic procedure was combined with open microsurgery for tumor removal with preservation of vascular structures. There wasn’t any “NECUP-2” related complications. Our preliminary results demonstrate that the application of the “NECUP-2” in neuroednosopic procedures is effective and safe, and can be a useful addition to standard neuroendoscopic instruments and techniques. O.098 Navigation- and laser assisted neuroendoscopy for stent placement in complex hydrocephalus H.C. Ludwig, V. Rohde Neurosurgery, Universitätsmedizin Goettingen, Germany Objective: In complex multiloculated hydrocephalus and intracranial cysts endoscopic procedures have replaced shunt operations with the implanta- tion of multiple catheters and microsurgery. Multiple catheter placements correspond with higher complication rates. The therapeutic goals are fen- estration of membranes for unhindered communication between different liquor compartments, the use of one single shunt catheter and stent place- ment for patency of the created fenestrations. Due to missing landmarks in cases of paediatric post infectious or haemorrhagic hydrocephalus stent placement and planning of the trajectory is dependent on neuronavigation. Methods: We have operated during the last 6 years 58 patients, mostly preterm infants with post haemorrhagic or infectious hydrocephalus and children with congenital cysts. The mean age was 15 years. In 40 of the 58 patients a shunt placement (Medos ® or proGAV ® Shunts, Bactiseal ® - catheter) was included. In some patients a shunt could be avoided. Neuronavigation was used in 90% of the procedures. In some cases the stent placement was combined with ETV, pellucidotomy and the rescue of lost or fixed catheters. Fenstrations were performed using a 2.0 μ fibre conducted laser (Revolix ® ). Results: Overall a shunt-free treatment was achieved in 17 children, 14 patients were treated by a new shunt with a single stent-catheter. Simpli- fication of a previous multiple-catheter shunt was possible in 25 children. In 7 children the development of a new cyst was observed and treated by reendoscopy (5) or microsurgery (2). Beside a transient hemiparesis we did not observe any morbidity or mortality. Conclusion: Essential for the result of cyst communication and stent place- ment is the planning of the right trajectory by neuronavigation. The use of a fibre conducted 2.0 μ laser (Revolix ® ) allows fast, safe and bloodless hollow cyst fenestrations. O.099 Introduction of a new intrument for easy frameless stereotactic placement of shunt catheters L.H. Stieglitz, L. Droll, W. Luedemann, P.M. Klinge, A. Samii, M. Samii International Neuroscience Institute, Hannover, Germany Objective: While the intraventricular placement of shunt catheters is usu- ally easy and secure using anatomical landmarks, stereotactic placement can be useful in cases with complex anatomy. Material and Methods: We built a shunt catheter placement tool for the VectorVision neuronavigation system by BrainLab, which can be used in combination with the BrainLab sterotaxy arm and needs no upgrades of the navigation system’s software. For testing of the tool a patient with hydrocephalus but otherwise normal anatomy was selected to allow easy control of the tool’s acuracy. As preoperative neuroimaging the patient received a cranial CT scan with a slice thickness of 1 mm. To keep the head moveable we used the “Laterus”-reference star by BrainLab which is fixed not to a Mayfield frame but to the forehead with a bone screw. Registration was performed using the Z-touch surface registration tool by BrainLab. Results: After planning of the intended trajectory of the shunt catheter using the BrainLab pointer, trepanation of the skull, opening of the dura and the cortex the pointer was substituted by the catheter placement tool which was brought into position and fixed using the BrainLab stereotaxy arm. The navigation unit of the tool was removed and the shunt catheter inserted as intended. After successful installation of the shunt catheter the placement tool was removed by opening of the guidance tube. The further shunt implantation procedure was continued as usual. The postoperative CT scan showed the correct placement of the shunt catheter. Conclusions: We introduce a new shunt catheter placement tool for easy frameless stereotactic shunt catheter placement using the VectorVision neuronavigation system by BrainLab. O.100 An “intelligent” shunt device and method for treating hydrocephalus secondary to intraventricular hemorrhage F. Pizzi University Medical Center at Princeton, Princeton, NJ, USA The proposed method and device, Dual Channel IVD (Internal Ventricular Drain)/Shunt, effectively eliminates deficiencies and patient jeopardies as- sociated with the usage of the External Ventricular Drainage (EVD) method in the presence of obstructive hydrocephalus secondary to blood in the cerebrospinal fluid pathways. A tube inserted in the ventricle is run under the scalp to an implanted device that receives the bloody ventricular fluid. The device splits into two channels, one with an on-off switch and reservoir and the other with a ball-in-cone spring valve. The “on” position allows the bloody fluid to run in a subcutaneously implanted valveless catheter