Abstracts of the Hydrocephalus 2008 Congress / Clinical Neurology and Neurosurgery 110S (2008), S1–S41 S25 CSF dynamics, preoperative medication, as well as operative records were examined to document initial shunt placement and following revisions. Subjects: There were 32 F and 3 M. Mean age: 35 years. Thirty five patients underwent 65 shunt placements in total. Twenty-six lumboperitoneal and 9 ventriculoperitoneal shunts were placed at first operation. Mean preopera- tive symptom duration: 30.5 months. Six patients had optic nerve sheath fen- estration previously. Mean CSF opening pressure during LP was 40 mm Hg. 46% of the patients experienced symptom improvement post-LP. In 71% of the patients headache was the initial symptom. Headache was present in all subjects whereas visual disturbances were present in 73% of the patients. 78% of patients had papilloedema on presentation. Only 2 patients (6%) were not obese. Only 2 patients (6%) did not receive additional pharma- cological treatment prior to operation. Outcome measures: Rate of shunt revision, headache and visual outcomes as documented in follow-up clinics. Results: The revision rate was 34%. In one third of the revision cases there was a site change. Two patients had both a VP and LP shunt in situ for control of symptoms. Mean time for first shunt revision was 14.2 months. Number of revisions ranged from 1-5 in mean follow-up period of 32.4 months. Headaches improved in 72% of cases. Visual function improved in 48% of cases. Conclusions: Headaches improve more often when compared with visual disturbances in patients suffering from BIH. There was no difference in outcomes between VP and LP shunts. Patients undergo frequent shunt revisions which often require change of site insertion or occasionally an additional shunt component. Patients should be followed-up for a minimum of 3 years. O.093 Prognostic clinical and radiological parameters for the evolution of hydrocephalus in patients with vestibular schwannomas V.M. Gerganov 1 , A. Pirayesh 1 , M. Nouri 2 , A. Samii 1 , M. Samii 1 1 International Neuroscience Institute, Hannover, Germany; 2 Tehran University of Medical Sciences, Tehran, Iran Objective: To define the preoperatively available parameters that might be related to the formation of hydrocephalus (H) or may predict its evolution after surgical removal of vestibular schwannomas (VS). Methods: radiological and clinical analysis of a series of 350 patients with VS. The following parameters were correlated to H: patients’ sex, age at onset of symptoms and at surgery; tumor diameters, shape, volume, and extension; type of H, dilation of the lateral ventricle – ipsilateral, contralateral, or bilateral, dilation of Sylvian fissure and of cortical sulci. Results: 49 patients had H (14%). The incidence of H was higher in elderly and in those with larger tumors (p<0.05). The mean age in both groups was similar, however in patients with H 13.5% were >65 years vs. 5.1% in patients without H. In case of round VS, an increased rate of H was found (83%, vs. 52%). In 48 patients the VS were removed primarily. In 13 of them the H disappeared early after surgery, in 30 cases it remained constant, and in 6 cases it increased. The tumor size tended to be larger among those 6 who didn’t respond to treatment (4.4cm vs. 3,7cm). The remaining clinical and radiological parameters showed no correlation to the outcome. Conclusion: Our data suggest that the incidence of H correlated with tumor size and age. The clinical and radiological examination cannot predict which patients will profit from primarily tumor removal and which will need specific therapy of the H. O.094 Simple valveless cystoventricular shunts in arachnoid cyst, a case series T. Keinert, N. Naveed, A. Aschoff, A. Unterberg Department of Neurosurgery, University Hospital Heidelberg, Germany Objective: The treatment of Arachnoid cysts ist still controversial. Micro- surgical, endoscopic approaches as well as valve shunts show a significant number of complications an revisions. The shortest, the most simple and costeffective procedure is a valveless shunt. We report of a case series of cystoventricular catheters shunting in patients of our collective with arachnoid cysts. Methods: Between January 2000 and December 2007, 6 patients with intracranial arachnoid cysts underwent surgery at University of Heidelberg and were treated with a valveless cystoventriccular shunt. Included in the study were 2 male and 4 female patients ranging in age from 30 to 78 years. Mean age was 51,6 years. All diagnoses were confirmed on neuroimaging, surgery and histological examination. Mean Follow up time was 29.8 month. Results: All cysts were temporal or parietal. The symptoms at presentation included headache (66%), weakness (33%), seizure (33%) and nausea (16%). Postoperative all patients besides one with an opioid abuse had a significant reduction of symptoms. There was a zero quota of side effects and revisions. The cyst size was reduced to 43% in mean related to fact that relatively big cysts were shunted. Postoperative quality of life was similar to normal collective. Conclusion: According to the principle of the creation of a single CSF space we present a simple and effective therapy for treating supratentoriell arachnoid cyst. Due to the technical approach severe risks as in open craniotomy or endoscopy are avoided. Otherwise typical shunt failures as valve malfunction, chronic headache or subdural hygroma are avoided. Session 7A 14:00–16:00, Room A (Technical) advances in surgical management of hydrocephalus O.095 A new assessment tool for evaluation of normal pressure hydrocephalus (NPH): Quantitative volumetric CSF drainage M.G. Wasner, G. Jost, D. Cordier, H. Bächli Neurosurgical Clinic, University Hospital, Basel, Switzerland Objective: Therapy of choice in patients with clinical and neuroradiolog- ical signs of NPH is ventriculo-peritoneal (VP-) shunting. The available shunt systems are partial pressure valves. The opening pressure of the valve is important to prevent over- or underdrainage. In a pilot study we determine preoperatively the individually adapted CSF volume reduction (ml/h) in optimal regression of NPH symptoms. The aim was to correlate the flow rate with the pressure stage of the valve. Methods: 10 patients with suspected NPH underwent preoperatively ex- ternal volumetric controlled CSF drainage (LiquoGuard ® , MöllerMedical) with staged drainage of 5ml/h to 20ml/h over 5 days. Before, during and after external CSF drainage, repetitive neuropsychological testing and a standardized gait analysis have been performed. In patients with confirmed NPH-diagnosis a proGAV (0-20/+25cm H 2 O) VP-shunt was implanted. In case of symptomatic improvement at 5ml/h CSF flow the pressure valve was set to 15cm H 2 O. In the follow up gait analysis, minimental test, urodynamic and CCT were repeated. Results: 2 of 10 patients showed no decrease of symptoms during open drainage. 8 patients received a VP shunt and exhibited a satisfactory reduc- tion of NPH symptoms. No overdrainage was noted. Ataxia was reduced in 8 of 8 patients, disturbance of memory was reduced in 6 of 8 patients. Conclusion: Preoperative volumetric drainage is a new assessment tool for NPH diagnostic workup and allows determining the optimal pressure stage of the shunt system. O.096 A novel impedance sensor to monitor and control ventricular size A. Linninger 1 , S. Basati 1 , R. Penn 2 1 University of Illinois at Chicago; 2 University of Chicago, IL, USA A novel impedance sensor for monitoring and controlling the volume of the cerebrospinal fluid-filled ventricles of the brain is will be presented.