Subthalamic Nucleus Deep Brain Stimulation Restores Motor and Sensorimotor Cortical Neuronal Oscillatory Activity in the Free-Moving 6-Hydroxydopamine Lesion Rat Parkinson Model.

OBJECTIVES: Enhanced beta oscillations in cortical-basal ganglia (BG) thalamic circuitries have been linked to clinical symptoms of Parkinson's disease. Deep brain stimulation (DBS) of the subthalamic nucleus (STN) reduces beta band activity in BG regions, whereas little is known about activity in cortical regions. In this study, we investigated the effect of STN DBS on the spectral power of oscillatory activity in the motor cortex (MCtx) and sensorimotor cortex (SMCtx) by recording via an electrocorticogram (ECoG) array in free-moving 6-hydroxydopamine (6-OHDA) lesioned rats and sham-lesioned controls. MATERIALS AND METHODS: Male Sprague-Dawley rats (250-350 g) were injected either with 6-OHDA or with saline in the right medial forebrain bundle, under general anesthesia. A stimulation electrode was then implanted in the ipsilateral STN, and an ECoG array was placed subdurally above the MCtx and SMCtx areas. Six days after the second surgery, the free-moving rats were individually recorded in three conditions: 1) basal activity, 2) during STN DBS, and 3) directly after STN DBS. RESULTS: In 6-OHDA-lesioned rats (N = 8), the relative power of theta band activity was reduced, whereas activity of broad-range beta band (12-30 Hz) along with two different subbeta bands, that is, low (12-30 Hz) and high (20-30 Hz) beta band and gamma band, was higher in MCtx and SMCtx than in sham-lesioned controls (N = 7). This was, to some extent, reverted toward control level by STN DBS during and after stimulation. No major differences were found between contacts of the electrode grid or between MCtx and SMCtx. CONCLUSION: Loss of nigrostriatal dopamine leads to abnormal oscillatory activity in both MCtx and SMCtx, which is compensated by STN stimulation, suggesting that parkinsonism-related oscillations in the cortex and BG are linked through their anatomic connections.

Does Temporary Externalization of Electrodes After Deep Brain Stimulation Surgery Result in a Higher Risk of Infection?

OBJECTIVES: Deep brain stimulation (DBS) is a well-established surgical therapy for movement disorders that comprises implantation of stimulation electrodes and a pacemaker. These procedures can be performed separately, leaving the possibility of externalizing the electrodes for local field potential recording or testing multiple targets for therapeutic efficacy. It is still debated whether the temporary externalization of DBS electrodes leads to an increased risk of infection. We therefore aimed to assess the risk of infection during and after lead externalization in DBS surgery. MATERIALS AND METHODS: In this retrospective study, we analyzed a consecutive series of 624 DBS surgeries, including 266 instances with temporary externalization of DBS electrodes for a mean of 6.1 days. Patients were available for follow-up of at least one year, except in 15 instances. In 14 patients with negative test stimulation, electrodes were removed. All kinds of infections related to implantation of the neurostimulation system were accounted for. RESULTS: Overall, infections occurred in 22 of 624 surgeries (3.5%). Without externalization of electrodes, infections were noted after 7 of 358 surgeries (2.0%), whereas with externalization, 15 of 252 infections were found (6.0%). This difference was significant (p = 0.01), but it did not reach statistical significance when comparing groups within different diagnoses. The rate of infection with externalized electrodes was highest in psychiatric disorders (9.1%), followed by Parkinson's disease (7.3%), pain (5.7%), and dystonia (5.5%). The duration of the externalization of the DBS electrodes was comparable in patients who developed an infection (6.1 ± 3.1 days) with duration in those who did not (6.0 ± 3.5 days). CONCLUSIONS: Although infection rates were relatively low in our study, there was a slightly higher infection rate when DBS electrodes were externalized. On the basis of our results, the indication for electrode externalization should be carefully considered, and patients should be informed about the possibility of a higher infection risk when externalization of DBS electrodes is planned.

Resection of posterior fossa tumors in the semi-sitting position in children younger than 4 years of age.

PURPOSE: The semi-sitting position for resection of posterior fossa tumors is a matter of ongoing debate. Here we report about our experience with this approach in children younger than 4 years of age. METHODS: We retrospectively analyzed data of children younger than 4 years of age operated on in our institution in the semi-sitting position over a 15-year period. Patients were intraoperatively monitored for venous air embolism (VAE) by transthoracic Doppler (TTD) or transesophageal echocardiography (TEE). The severity of VAE was classified according to the Tübingen grading scale. Intraoperative incidents of VAE were recorded and the patients' course was followed postoperatively with a special focus on possible complications. RESULTS: Twenty-four children (18 boys, 6 girls) were operated on in the semi-sitting position (26 operations). Mean age was 2.2 years (± 1.0), range between 0.4 and 3.9 years. External ventricular drains were inserted in 18 children with hydrocephalus preoperatively. VAE was detected in 6 instances during surgery (6/26 (23.1%)). In 3 patients with grade 1 VAE, no additional treatment was necessary. In one patient with grade 2 VAE, intracardiac air suction via the central venous catheter was performed, and in two patients with grade 4 VAE, additional cathecholamine-infusion was administered. No major intraoperative complications occurred. Postoperative CT images showed pneumocephalus in all children. In two children, small asymptomatic impression skull fractures at the site of the Mayfield pin occurred. Revision surgery was necessary in one child with a suboccipital CSF fistula. CONCLUSION: The semi-sitting position for resection of tumors in the posterior fossa in children younger than 4 years of age can be safely performed in experienced centers taking special caution to detect and treat potential complications in an interdisciplinary setting.

Microsurgical posterior fossa re-exploration for recurrent trigeminal neuralgia after previous microvascular decompression: common grounds-scarring, deformation, and the "piston effect".

OBJECTIVE: Microvascular decompression (MVD) is a well-accepted treatment modality for trigeminal neuralgia (TN) with high initial success rates. The causes for recurrence of TN after previously successful MVD have not been fully clarified, and its treatment is still a matter of debate. Here, we present the surgical findings and the clinical outcome of patients with recurrent TN after MVD who underwent posterior fossa re-exploration. METHODS: Microsurgical posterior fossa re-exploration was performed in 26 patients with recurrent TN (mean age 59.1 years) who underwent MVD over a period of 10 years. The trigeminal nerve was exposed, and possible factors for recurrent TN were identified. Arachnoid scars and Teflon granulomas were dissected meticulously without manipulating the trigeminal nerve. Outcome of posterior fossa re-exploration was graded according to the Barrow Neurological Institute (BNI) pain intensity score. Follow-up was analyzed postoperatively at 3, 12, and 24 months and at the latest available time point for long-term outcome. RESULTS: The mean duration of recurrent TN after the first MVD was 20 months. Pain relief was achieved in all patients with recurrent TN on the first postoperative day. Intraoperative findings were as follows: arachnoid scar tissue in 22/26 (84.6%) patients, arterial compression in 1/26 (3.8%), venous contact in 8/26 (30.8%), Teflon granuloma in 14/26 (53.8%), compression by an electrode in Meckel's cave used for treatment of neuropathic pain in 1/26 (3.8%), evidence of pulsations transmitted to the trigeminal nerve through the Teflon inserted previously/scar tissue ("piston effect") in 15/26 (57.7%), and combination of findings in 18/26 (69.2%). At long-term follow-up (mean 79.5 months; range, 29-184 months), 21/26 (80.8%) patients had favorable outcome (BNI I-IIIa). New hypaesthesia secondary to microsurgical posterior fossa re-exploration occurred in 5/26 (19.2%) patients. CONCLUSIONS: Posterior fossa re-exploration avoiding manipulation to the trigeminal nerve, such as pinching or combing, may be a useful treatment option for recurrent TN after previously successful MVD providing pain relief in the majority of patients with a low rate of new hypaesthesia.

The semi-sitting position in patients with indwelling CSF shunts: perioperative management and avoidance of complications.

OBJECTIVE: Posterior fossa or midline tumors are often associated with hydrocephalus and primary tumor removal with or without perioperative placement of an external ventricular drain (EVD) is commonly accepted as first-line treatment. Shunting prior to posterior fossa surgery (PFS) is mostly reserved for symptomatic cases or special circumstances. There are limited data regarding the anticipated risk for symptomatic pneumocephalus and the perioperative management using the semi-sitting position (SSP) in such a scenario. Here, we therefore assessed the safety of performing PFS in a consecutive series of patients over a period of 15 years to allow the elaboration of recommendations for perioperative management. METHODS: According to specific inclusion and exclusion criteria a total of 13 patients who underwent 17 operations was identified. Supratentorial pneumocephalus was evaluated with semiautomatic-volumetric segmentation. The volume of pneumocephalus was evaluated according to age and ventricular size. RESULTS: Ten of the 13 patients had a programmable valve (preoperative valve setting range 6-14 cmH20; mean 7.5 cmH20) while 3 patients had non programmable valves. A variable amount of supratentorial air collection was evident in all patients postoperatively (range 3.2-331 ml; mean 122.32 ml). Positive predictors for the volume of postoperative pneumocephalus were higher age and a preoperative Evans ratio > 0.3. In our series, we encountered no cases of tension pneumocephalus necessitating an air replacement procedure as well as no obstruction, disconnection, infection or hardware malfunction of the shunt system. CONCLUSIONS: Our findings indicate that a CSF shunt in situ is not a contraindication for performing PFS in the semi-sitting position and it does not increase the pre-existing risk for postoperative tension pneumocephalus. In cases of primary shunting for hydrocephalus associated with posterior fossa tumors a programmable valve set at a medium opening pressure with a gravitational device is a valid option when PFS in the semi-sitting position is opted. In patients with an indwelling shunt diversion system special caution is indicated in order to prevent and detect overdrainage especially in not adjustable valves or shunts without antisiphon devices.

Routine postoperative admission to the neurocritical intensive care unit after microvascular decompression: necessary or can it be abandoned?

Postoperative neurocritical intensive care unit (NICU) admission of patients who underwent craniotomy for close observation is common practice. In this study, we performed a comparative analysis to determine if there is a real need for NICU admission after microvascular decompression (MVD) for cranial nerve disorders or whether it may be abandoned. The present study evaluates a consecutive series of 236 MVD surgeries performed for treatment of trigeminal neuralgia (213), hemifacial spasm (17), vagoglossopharyngeal neuralgia (2), paroxysmal vertigo (2), and pulsatile tinnitus (2). All patients were operated by the senior surgeon according to a standard protocol over a period of 12 years. Patients were admitted routinely to NICU during the first phase of the study (phase I), while in the second phase (phase II), only patients with specific indications would go to NICU. While 105 patients (44%) were admitted to NICU postoperatively (phase I), 131 patients (56%) returned to the ward after a short stay in a postanaesthesia care unit (PACU) (phase II). Specific indications for NICU admission in phase I were pneumothorax secondary to central venous catheter insertion (4 patients), AV block during surgery, low blood oxygen levels after extubation, and postoperative dysphagia and dysphonia (1 patient, respectively). There were no significant differences in the distribution of ASA scores or the presence of cardiac and pulmonary comorbidities like congestive heart failure, arterial hypertension, or chronic obstructive pulmonary disease between groups. There were no secondary referrals from PACU to NICU. Our study shows that routine admission of patients after eventless MVD to NICU does not provide additional value. NICU admission can be restricted to patients with specific indications. When MVD surgery is performed in experienced hands according to a standard anaesthesia protocol, clinical observation on a neurosurgical ward is sufficient to monitor the postoperative course. Such a policy results in substantial savings of costs and human resources.

Oscillatory activity in the BNST/ALIC and the frontal cortex in OCD: acute effects of DBS.

Deep brain stimulation (DBS) of the bed nucleus of the stria terminalis/anterior limb of the internal capsule (BNST/ALIC) is successfully used for treatment of patients with obsessive-compulsive disorder (OCD). Clinical and experimental studies have suggested that enhanced network synchronization in the theta band is correlated with severity of symptoms. The mechanisms of action of DBS remain unclear in OCD. We here investigate the effect of acute stimulation of the BNCT/ALIC on oscillatory neuronal activity in patients with OCD implanted with DBS electrodes. We recorded the oscillatory activity of local field potentials (LFPs) from DBS electrodes (contact + 0/- 3; bipolar configuration; both hemispheres) from the BNST/ALIC parallel with frontal cortical electroencephalogram (EEG) one day after DBS surgery in four patients with OCD. BNST/ALIC and frontal EEG oscillatory activities were analysed before stimulation as baseline, and after three periods of stimulation with different voltage amplitudes (1 V, 2 V and 3.5 V) at 130 Hz. Overall, acute high frequency DBS reduced oscillatory theta band (4-8 Hz; p < 0.01) but increased other frequency bands in BNST/ALIC and the frontal cortex (p < 0.01). We show that stimulation of the BNST/ALIC in OCD modulates oscillatory activity in brain regions that are involved in the pathomechanisms of OCD. Our findings confirm and extend the findings that enhanced theta oscillatory activity in neuronal networks may be a biomarker for OCD.

Pseudotumor cerebri syndrome in a child with Alagille syndrome: intracranial pressure dynamics and treatment outcome after ventriculoperitoneal shunting.

Alagille syndrome (AS) is a rare multisystem disease of the liver, heart, eyes, face, skeleton, kidneys, and vascular system. The occurrence of pseudotumor cerebri syndrome (PTCS) in patients with AS has been reported only exceptionally. Owning to its rarity and a mostly atypical presentation, the diagnosis and natural history of affected patients remain uncertain. We report an atypical case of PTCS in a 4-year-old boy with a known history of AS who presented with bilateral papilledema (PE) on a routine ophthalmological examination. Visual findings deteriorated after treatment with acetazolamide. Continuous intracranial pressure (ICP) monitoring was then utilized to investigate ICP dynamics. Successful treatment with resolution of PE was achieved after ventriculoperitoneal shunting but relapsed due to growth-related dislocation of the ventricular catheter. This report brings new insights into the ICP dynamics and the resulting treatment in this possibly underdiagnosed subgroup of PTCS patients. It also demonstrates that ventriculoperitoneal shunting can provide long-term improvement of symptoms for more than 10 years.

Effect of a bundle approach on external ventricular drain-related infection.

BACKGROUND: Emergency placement of an external ventricular drain (EVD) is one of the most frequently performed neurosurgical procedures. EVD-related infection continues to be a major challenge causing significant morbidity and costs. Bundle approaches have been shown to reduce infection rates; however, they are still not widely used, and observation periods often were rather short. METHODS: The present study evaluated the effect of a multi-item bundle approach for EVD placement and care on the occurrence of EVD-related infection. A before/after approach was used to compare groups of consecutive patients over 5-year epochs to control for bias and secondary confounding variables. RESULTS: The number of patients in the group before implementation of the bundle approach was 141 and 208 thereafter. There were no statistical differences in demographic and other variables. While 41/141 patients (29.1%) had an EVD-related infection before, this was the case in only 10/208 patients (4.8%) thereafter (p < 0.0001). The EVD-related infection rate was reduced from 13.7/1000 catheter days to 3.2/1000, and the 50% probability of an EVD-related infection in correlation to the mean duration of EVD placement was significantly lower (p < 0.0001). Routine EVD replacement was not helpful to reduce EVD-related infection. EVD-related infection rates remained low also over the next 8 years after the study was finished. CONCLUSIONS: The introduction of a multi-item bundle approach for EVD insertion and care resulted in a marked reduction of EVD-related infection. Long observation periods over 5 years and beyond confirm that short-term changes are sustained with continued use of such protocols.

Primary and secondary gliosarcoma: differences in treatment and outcome.

INTRODUCTION: There are only few studies comparing differences in the outcome of primary versus secondary gliosarcoma. This study aimed to review the outcome and survival of patients with primary or secondary gliosarcoma following surgical resection and adjuvant treatment. The data were also matched with data of patients with primary and secondary glioblastoma (GBM). PATIENTS AND METHODS: Treatment histories of 10 patients with primary gliosarcoma and 10 patients with secondary gliosarcoma were analysed and compared. Additionally, data of 20 patients with primary and 20 patients with secondary GBM were analysed and compared. All patients underwent surgical resection of the tumour in our department. Follow-up data, progression-free survival (PFS), and median overall survival (mOS) were evaluated. RESULTS: The median PFS in patients with primary gliosarcoma was significantly higher than in patients with secondary gliosarcoma (p = 0.037). The 6-month PFS rates were 80.0% in patients with primary and 30.0% in patients with secondary gliosarcoma. Upon recurrence, five patients with primary gliosarcoma and four patients with secondary gliosarcoma underwent repeat surgical resection. The mOS of patients with primary gliosarcoma was significantly higher than that of patients with secondary gliosarcoma (p = 0.031). The percentage of patients surviving at 1-year/2-year follow-up in primary gliosarcoma was 70%/20%, while it was only 10%/10% in secondary gliosarcoma. When PFS and mOS of primary gliosarcoma was compared to primary GBM, there were no statistically differences (p = 0.509; p = 0.435). The PFS and mOS of secondary gliosarcoma and secondary GBM were also comparable (p = 0.290 and p = 0.390). CONCLUSION: Patients with primary gliosarcoma have a higher PFS and mOS compared to those with secondary gliosarcoma. In the case of tumour recurrence, patients with secondary gliosarcoma harbour an unfavourable prognosis with limited further options. The outcome of patients with primary or secondary gliosarcoma is comparable to that of patients with primary or secondary GBM.

Long-Term Deep Brain Stimulation in Treatment-Resistant Obsessive-Compulsive Disorder: Outcome and Quality of Life at Four to Eight Years Follow-Up.

BACKGROUND: Obsessive compulsive disorder (OCD) is a severe disabling disease, and around 10% of patients are considered to be treatment-resistant (tr) in spite of guideline-based therapy. Deep brain stimulation (DBS) has been proposed as a promising treatment for patients with trOCD. However, the optimal site for stimulation is still a matter of debate, and clinical long-term follow-up observations including data on quality of life are sparse. We here present six trOCD patients who underwent DBS with electrodes placed in the bed nucleus of the stria terminalis/anterior limb of the internal capsule (BNST/ALIC), followed for four to eight years after lead implantation. MATERIALS AND METHODS: In this prospective observational study, six patients (four men, two women) aged 32-51 years and suffering from severe to extreme trOCD underwent DBS of the BNST/ALIC. Symptom severity was assessed using the Yale-Brown Obsessive Compulsive Scale (Y-BOCS), and quality of life using the World Health Organization Quality of Life assessment scale (WHO-QoL BREF). Follow-up was obtained at least for four years in all patients. RESULTS: With chronic DBS for four to eight years, four of the six patients had sustained improvement. Two patients remitted and two patients responded (defined as >35% symptom reduction), while the other two patients were considered nonresponders on long-term. Quality of life markedly improved in remitters and responders. We did not observe peri-interventional side effects or adverse effects of chronic stimulation. CONCLUSIONS: Chronic DBS of ALIC provides long-term benefit up to four to eight years in trOCD, although not all patients take profit. Targeting the BNST was not particularly relevant since no patient appeared to benefit from direct stimulation of the BNST. Quality of life improved in DBS responders, documented by improved QoL scores and, even more important, by regaining of autonomy and improving psychosocial functioning.

Microvascular decompression: is routine postoperative CT imaging necessary?

BACKGROUND: Postoperative head CT imaging is routinely performed for detection of postoperative complications following intracranial procedures. However, it remains unclear whether with regard to radiation exposure, costs, and possibly lack of consequences this practice is truly justified in various operative procedures. The objective of this study was to analyze whether routine postoperative CT imaging after microvascular decompression (MVD) is necessary or whether it may be abandoned. METHODS: A series of 202 MVD surgeries for trigeminal neuralgia (179), hemifacial spasm (17), vagoglossopharyngeal neuralgia (2), paroxysmal vertigo (2), and pulsatile tinnitus (2) operated by the senior surgeon (JKK) and who had postoperative routine CT imaging was analyzed. RESULTS: Routine postoperative CT imaging detected small circumscribed postoperative hemorrhage in 9/202 (4.4%) instances. Hemorrhage was localized at the site of the Teflon felt (1/9), the cerebellum (4/9), in the frontal subdural space (3/9), and in the frontal subarachnoid space (1/9). In two patients, asymptomatic hemorrhage was accompanied by mild cerebellar edema (1%), and another patient had mild transient hydrocephalus (0.5%). Furthermore, there were small accumulations of intracranial air in 86/202 instances. No other complications such as infarction or skull fracture secondary to fixation with the Mayfield clamp were detected. MVD had been performed for trigeminal neuralgia in 6/9 patients, for hemifacial spasm in 2/9, and in one patient with both. No patient underwent a second surgery. Hemorrhage was symptomatic at the time of imaging in only one instance who had mild postoperative gait ataxia. Two patients with hemorrhage developed delayed facial palsy most likely unrelated to hemorrhage which remitted with corticosteroid treatment. At 3-month follow-up and at long-term follow-up, they had no neurological deficits. CONCLUSION: Routine postoperative CT imaging is not necessary after MVD in a standard setting in patients who do not have postoperative neurological deficits.

Multisegmental Lumbar Corporectomy and Transcorporal Fixation for Correction of Extreme Thoracolumbar Kyphosis in Myelomeningocele with Chronic Decubitus.

We introduce a novel technique for the treatment of severe kyphosis in myelomeningocele. A 5-year-old paraplegic boy with myelomeningocele presented with severe thoracolumbar kyphosis and a chronic ulcus at the site of the gibbus. The myelomeningocele had been treated during his first week of life, and an accompanying Chiari type II malformation had been treated by ventriculoperitoneal shunting. He subsequently developed a rapidly progressive thoracolumbar kyphosis with an angle of 180° between T10 and L5. He also suffered from a chronic superinfected skin ulcus at the site of the gibbus. Since the skin ulcus required plastic surgery reconstruction, we deemed classical posterior fixation after kyphectomy unfeasible. The subsequent operative steps of our novel surgical approach were performed in a single-stage surgery. First, a three-level lumbar corporectomy from L1 to L3 was performed. Subsequently, the body of the removed L2 vertebra was isolated and configured as an autologous graft to bridge the gap between the thoracic and the caudal lumbar spine. The graft was fixed via a transcorporal interbody fusion technique with titanium screws, and chopped autologous bone was added for fusion. The skin was closed using rotation flaps. At the 3-year follow-up, the patient and his family reported marked improvement of quality of life, imaging showed solid fusion and the wound was unremarkable. Our novel technique with transcorporal fixation provides new perspectives in the treatment of severe kyphosis and skin ulceration in myelomeningocele.

Optimizing in†Vitro Impedance and Physico-Chemical Properties of Neural Electrodes by Electrophoretic Deposition of Pt Nanoparticles.

Neural electrodes suffer from an undesired incline in impedance when in permanent contact with human tissue. Nanostructures, induced by electrophoretic deposition (EPD) of ligand-free laser-generated nanoparticles (NPs) on the electrodes are known to stabilize impedance in vivo. Hence, Pt surfaces were systematically EPD-coated with Pt NPs and evaluated for impedance as well as surface coverage, contact angle, electrochemically active surface area (ECSA) and surface oxidation. The aim was to establish a systematic correlation between EPD process parameters and physical surface properties. The findings clearly reveal a linear decrease in impedance with increasing surface coverage, which goes along with a proportional reduction of the contact angle and an increase in ECSA and surface oxidation. EPD process parameters, prone to yield surface coatings with low impedance, are long deposition times (40-60 min), while high colloid concentrations (>250 µg mL-1 ) and electric field strengths (>25 V cm-1 ) should be avoided due to detrimental NP assemblage effects.

Shunt Surgery in Idiopathic Intracranial Hypertension Aided by Electromagnetic Navigation.

BACKGROUND: Idiopathic intracranial hypertension (IIH) is characterized by increased cerebrospinal fluid (CSF) pressure and normal or slit ventricles. Lumboperitoneal shunting had been favored by many investigators for CSF diversion in IIH for decades; however, it has been associated with various side effects. Because of the small ventricular size adequate positioning of a ventricular catheter is challenging. OBJECTIVES: Here, we investigated the usefulness of electromagnetic (EM)-guided ventricular catheter placement for ventriculoperitoneal shunting in IIH. METHODS: Eighteen patients with IIH were included in this study. The age of patients ranged from 5 to 58 years at the time of surgery (mean age: 31.8 years; median: 29 years). There were 2 children (5 and 11 years old) and 16 adults. Inclusion criteria for the study were an established clinical diagnosis of IIH, lack of improvement with medication, and the presence of small ventricles. In all patients EM-navigated placement of the ventricular catheter was performed using real-time tracking of the catheter tip for exact positioning close to the foramen of Monro. Postoperative CT scans were correlated with intraoperative screen shots to validate the position of the catheter. RESULTS: In all patients EM-navigated ventricular catheter placement was achieved with a single pass. There were no intraoperative or postoperative complications. Postoperative imaging confirmed satisfactory positioning of the ventricular catheter. No proximal shunt failure was observed during the follow-up at a mean of 41.5 months (range: 7-90 months, median: 40.5 months). CONCLUSIONS: EM-navigated ventricular catheter placement in shunting for IIH is a safe and straightforward technique. It obviates the need for sharp head fixation, the head of the patient can be moved during surgery, and it may reduce the revision rate during follow-up.

What Do Medical Students Know about Deep Brain Stimulation?

BACKGROUND: Deep brain stimulation (DBS) is an established therapy for movement disorders. It is currently under investigation in neuropsychiatric disorders. Neurophobia is a common phenomenon that might have a negative impact in medical education. Little is known about medical students' knowledge about DBS when they enter university and what they learn about it during their medical formation. METHODS: A 10-item questionnaire was designed. Questions addressed indications for DBS, costs of DBS, complications, the percentage of Parkinson disease (PD) patients who might profit from DBS, etc. Students at Hannover Medical School were asked to complete the questionnaire in the preclinical study period and in the last year of the study. RESULTS: Comparing the "early group" (204 students) and the "advanced group" (162 students), there was a significant gain of knowledge. More common disorders such as PD and tremor were known to be indications for DBS. Knowledge about the impact of DBS on specific symptoms in PD and about DBS targets was limited in both groups. CONCLUSIONS: DBS is partly known among medical students in the preclinical phase with a gain of knowledge during further study. Future studies on this topic addressing general practitioners as neurologists are needed to better understand why knowledge on DBS is still limited.

Electrophoretic deposition of ligand-free platinum nanoparticles on neural electrodes affects their impedance in vitro and in vivo with no negative effect on reactive gliosis.

BACKGROUND: Electrodes for neural stimulation and recording are used for the treatment of neurological disorders. Their features critically depend on impedance and interaction with brain tissue. The effect of surface modification on electrode impedance was examined in vitro and in vivo after intracranial implantation in rats. Electrodes coated by electrophoretic deposition with platinum nanoparticles (NP; <10 and 50 nm) as well as uncoated references were implanted into the rat's subthalamic nucleus. After postoperative recovery, rats were electrostimulated for 3 weeks. Impedance was measured before implantation, after recovery and then weekly during stimulation. Finally, local field potential was recorded and tissue-to-implant reaction was immunohistochemically studied. RESULTS: Coating with NP significantly increased electrode's impedance in vitro. Postoperatively, the impedance of all electrodes was temporarily further increased. This effect was lowest for the electrodes coated with particles <10 nm, which also showed the most stable impedance dynamics during stimulation for 3 weeks and the lowest total power of local field potential during neuronal activity recording. Histological analysis revealed that NP-coating did not affect glial reactions or neural cell-count. CONCLUSIONS: Coating with NP <10 nm may improve electrode's impedance stability without affecting biocompatibility. Increased impedance after NP-coating may improve neural recording due to better signal-to-noise ratio.

Comparative characterization of single cell activity in the globus pallidus internus of patients with dystonia or Tourette syndrome.

Altered processing in the basal ganglia has been described both in dystonia and Tourette's syndrome (TS). Deep brain stimulation (DBS) of the globus pallidus internus (GPi) has become a recognized treatment for dystonia and has been used successfully to alleviate tics in TS. This study evaluates possible differences of GPi linear and nonlinear neuronal discharge characteristics between patients with dystonia and TS. Nine patients with primary dystonia and six patients with TS were studied during functional stereotactic neurosurgical operations for implantation of DBS electrodes under general anesthesia. Six patients with primary dystonia under local anesthesia served as non-anesthetized controls. Single-unit activity recordings in the GPi were obtained during routine microelectrode recording and mapping to delineate nuclear borders and to identify the sensorimotor subregions. Anesthesia profoundly decreased neuronal activity in patients with dystonia. Dystonia patients showed marginally higher mean firing rates in the GPi compared to TS patients (P = 0.06). Although the average total number of bursts and the mean peak frequency in bursts did not differ between groups, the mean spikes in bursts were higher in dystonia patients (P < 0.05). Nonlinear time series analysis metrics, measured as complexity of Lempel-Ziv and maximum approximate entropy, revealed higher randomness in TS compared to dystonia patients (P < 0.05). The percentage of oscillating neurons in spike trains was higher in dystonia compared to TS (P < 0.05). Our data provide evidence for differences of the neuronal dynamic complexity, randomness and oscillatory modulation of spike trains in the GPi between dystonia and TS. Such differences, although subtle, might contribute to the specific clinical phenomenology secondary to disordered neuronal basal ganglia processing.

Reducing radiation exposure and costs: CT body scout views with an enhanced protocol versus conventional radiography after shunt surgery.

OBJECTIVE: Ventriculoperitoneal shunt implantation has become standard treatment for cerebrospinal fluid diversion, besides endoscopic third ventriculostomy for certain indications. Postoperative X-ray radiography series of skull, chest and abdomen combined with cranial CT are obtained routinely in many institutions to document the shunt position and valve settings in adult patients. Measures to reduce postoperative radiation exposure are needed, however, there is only limited experience with such efforts. Here, we aim to compare routine postoperative cranial CT plus conventional radiography series (retrospective arm) with cranial CT and body scout views only (prospective arm) concerning both diagnostic quality and radiation exposure. PATIENTS AND METHODS: After introduction of an enhanced CT imaging protocol, routine skull and abdomen radiography was no longer obtained after VP shunt surgery. The image studies of 25 patients with routine postoperative cranial CT and conventional radiography (retrospective arm of study) were then compared to 25 patients with postoperative cranial CT and CT body scout views (prospective arm of study). Patient demographics such as age, sex and primary diagnosis were collected. The image quality of conventional radiographic images and computed tomography scout views images were independently analyzed by one neurosurgeon and one neuroradiologist. RESULTS: There were no differences in quality assessments according to three different factors determined by two independent investigators for both groups. There was a statistically significant difference, however, between the conventional radiography series group and the CT body scout view imaging group with regard to radiation exposure. The effective dose estimation calculation yielded a difference of 0.05 mSv (two-tailed t-test, p = 0.044) in favor of CT body scout view imaging. Furthermore, the new enhanced protocol resulted in a reduction of cost and the use of human resources. CONCLUSION: CT body scout view imaging provides sufficient imaging quality to determine shunt positioning and valve settings. With regard to radiation exposure and costs, we suggest that conventional postoperative shunt series may be abandoned.

Microelectrode recording and hemorrhage in functional neurosurgery: a comparative analysis in a consecutive series of 645 procedures.

OBJECTIVE: Functional stereotactic neurosurgery including deep brain stimulation (DBS) and radiofrequency lesioning is well established and widely used for treatment of movement disorders and various other neurological and psychiatric diseases. Although functional stereotactic neurosurgery procedures are considered relatively safe, intracranial hemorrhage resulting in permanent neurological deficits may occur in 1%-3% of patients. Microelectrode recording (MER) has been recognized as a valuable tool for refining the final target in functional stereotactic neurosurgery. Moreover, MER provides insight into the underlying neurophysiological pathomechanisms of movement disorders and other diseases. Nevertheless, there is an ongoing controversy on whether MER increases the risk for hemorrhage. The authors aimed to compare the risk of hemorrhage in functional stereotactic neurosurgical procedures with regard to the use of MER. METHODS: The authors performed a comparative analysis on a consecutive series of 645 functional neurosurgery procedures, including 624 DBS surgeries and 21 radiofrequency lesionings, to evaluate whether the use of MER would increase the risk for hemorrhage. MER was performed in 396 procedures, while no MER was used in 249 cases. The MER technique involved the use of a guiding cannula and a single trajectory when feasible. Postoperative CT scans were obtained within 24 hours after surgery in all patients and screened for the presence of hemorrhage. RESULTS: Twenty-one intracranial hemorrhages were detected on the postoperative CT scans (3.2%). Of the 21 intracranial hemorrhages, 14 were asymptomatic and 7 were symptomatic. Symptoms were transient except in 1 case. There was no statistically significant correlation between hemorrhage and the use of MER at any site (subdural, ventricle, trajectory, target, whether asymptomatic or symptomatic). There were 4 cases of symptomatic hemorrhage in the MER group (1%) and 3 cases in those without MER (1.2%). CONCLUSIONS: Intraoperative MER did not increase the overall risk of hemorrhage in the authors' experience using primarily a single MER trajectory and a guiding cannula.