Clinical and radiological outcome 1-year after cervical total disc replacement using the Signus ROTAIO - Prosthesis.

INTRODUCTION: The instantaneous center of rotation (iCOR) of a motion segment has been shown to correlate with its total range of motion (ROM). Importantly, a correlation of the correct placement of cervical total disc replacement (cTDR) to preserve a physiological iCOR has been previously identified. However, changes of these parameters and the corresponding clinical relevance have hardly been analyzed. This study assesses the radiological and clinical correlation of iCOR and ROM following cTDR. MATERIALS/METHODS: A retrospective multi-center observational study was conducted and radiological as well as clinical parameters were evaluated preoperatively and 1 year after cTDR with an unconstrained device. Radiographic parameters including flexion/extension X-rays (flex/ex), ROM, iCOR and the implant position in anterior-posterior direction (IP ap), as well as corresponding clinical parameters [(Neck Disability Index (NDI) and the visual analogue scale (VAS)] were assessed. RESULTS: 57 index segments of 53 patients treated with cTDR were analyzed. Pre- and post-operative ROM showed no significant changes (8.0° vs. 10.9°; p > 0.05). Significant correlations between iCOR and IP (Pearson's R: 0.6; p < 0.01) as well as between ROM and IP ap (Pearson's R: - 0.3; p = 0.04) were identified. NDI and VAS improved significantly (p < 0.01). A significant correlation between NDI and IP ap after 12 months (Pearson's R: - 0.39; p < 0.01) was found. CONCLUSION: Implantation of the tested prosthesis maintains the ROM and results in a physiological iCOR. The exact position of the device correlates with the clinical outcome and emphasize the importance of implant design and precise implant positioning.

Suction Spatula for Surgery of Vestibular Schwannomas in Supine Position: Technical Note.

BACKGROUND: Resection of vestibular schwannomas with good functional outcome remains a neurosurgical challenge. In this study, we report on our initial experience with a suction spatula, which allows free bimanual dissection of small tumors in a clear, bloodless surgical field in supine position. METHODS: Forty-one patients underwent vestibular schwannoma surgery in supine position, using a suction spatula. To analyze its feasibility, 11 aspects of the device were compared with the regular retractor. RESULTS: The suction spatula was successfully applied in all surgeries. Compared with a common spatula, the suction spatula showed superior performance during meatotomy, microsurgical and endoscopic tumor dissection, and management of bleedings. We noted no difference in ergonomics, compatibility, instrumental conflict, costs, reusability, and sterilization issues. Minor performance was related to its thickness/size. There were no significant disadvantages according to our data. There were no surgical complications related to this device. CONCLUSIONS: The main advantage of the suction spatula is in the treatment of small, mainly intrameatal vestibular schwannomas in supine patient position. It gives the surgeon a "third hand" while enabling a continuous bimanual dissection with 2 microinstruments without the use of a regular suction tip.

Two-pore-domain potassium channels contribute to neuronal potassium release and glial potassium buffering in the rat hippocampus.

Two-pore-domain potassium (K2P) channels have been suggested to be involved in neuronal K+ release and glial K+ uptake. We studied effects of the K2P channel blockers quinine (200 or 500 microM), quinidine (500 microM), and bupivacaine (200 microM) on stimulus-induced and iontophoretically induced transient increases of the extracellular potassium concentration ([K+]o) in area CA1 of rat hippocampal slices, always in presence of AMPA/kainate and NMDA receptor antagonists. Increases in [K+]o evoked by repetitive alvear stimulation (20 Hz) were blocked by quinine and quinidine but amplitudes of population spikes were only modestly reduced. Bupivacaine suppressed both rises in [K+]o and population spikes. In contrast, iontophoretically induced rises in [K+]o were moderately augmented by quinine and quinidine while bupivacaine had no effect. Barium at concentrations of 2 mM which should block both potassium inward rectifier (Kir) and some K2P channels doubled iontophoretically induced rises in [K+]o also in presence of quinine, quinidine, and bupivacaine. The data suggest that quinine/quinidine-sensitive K2P channels mediate K+ release from neurons and possibly contribute to glial K+ buffering.

Carbamazepine-resistance in the epileptic dentate gyrus of human hippocampal slices.

Overexpression of drug efflux pumps at the blood brain barrier (BBB) has been suggested to be one important factor contributing to drug resistance in epilepsy. This would imply that resected brain tissue of drug-resistant patients is drug-sensitive in absence of the BBB. Here we studied the effects of carbamazepine (CBZ) at therapeutically relevant concentration on epileptiform activity electrophysiologically recorded in acute hippocampal slices of patients with mesial temporal lobe epilepsy (MTLE; 28 patients, 49 slices) or extra-hippocampal tumours (tumour; 6 patients, 11 slices). Epileptiform activity was induced by hilar stimulation (0.067 Hz) during elevation of extracellular potassium concentration ([K(+)](o)) and remained self-sustained in presence of 10-12 mM [K(+)](o). Quantitative analysis of data revealed that epileptiform activity in tissue of tumour-patients was predominantly suppressed by CBZ, indicating that the 'epilepsy model' used is CBZ-sensitive. In contrast, epileptiform activity in tissue of drug-resistant MTLE patients was resistant to CBZ in 82% of patients, partially suppressed in 11% and completely suppressed in 7%. The effects of CBZ in tissue of MTLE patients did not depend on the type of activity, hippocampal pathology, excitability of the tissue, or equilibration time of the drug. Considering that CBZ has direct access to all compartments of the slice, our results suggest that CBZ-resistance mechanisms are located within the parenchyma of the dentate gyrus and contribute to drug resistance in the majority of MTLE patients. BBB-located drug-resistance mechanisms per se may play a minor role in this region, because CBZ-sensitivity was only observed in 7% of CBZ-resistant patients.

Drug resistance in cortical and hippocampal slices from resected tissue of epilepsy patients: no significant impact of p-glycoprotein and multidrug resistance-associated proteins.

Drug resistant patients undergoing epilepsy surgery have a good chance to become sensitive to anticonvulsant medication, suggesting that the resected brain tissue is responsible for drug resistance. Here, we address the question whether P-glycoprotein (Pgp) and multidrug resistance-associated proteins (MRPs) expressed in the resected tissue contribute to drug resistance in vitro. Effects of anti-epileptic drugs [carbamazepine (CBZ), sodium valproate, phenytoin] and two unspecific inhibitors of Pgp and MRPs [verapamil (VPM) and probenecid (PBN)] on seizure-like events (SLEs) induced in slices from 35 hippocampal and 35 temporal cortex specimens of altogether 51 patients (161 slices) were studied. Although in slice preparations the blood brain barrier is not functional, we found that SLEs predominantly persisted in the presence of anticonvulsant drugs (90%) and also in the presence of VPM and PBN (86%). Following subsequent co-administration of anti-epileptic drugs and drug transport inhibitors, SLEs continued in 63% of 143 slices. Drug sensitivity in slices was recognized either as transition to recurrent epileptiform transients (30%) or as suppression (7%), particularly by perfusion with CBZ in PBN containing solutions (43, 9%). Summarizing responses to co-administration from more than one slice per patient revealed that suppression of seizure-like activity in all slices was only observed in 7% of patients. Patients whose tissue was completely or partially sensitive (65%) presented with higher seizure frequencies than those with resistant tissue (35%). However, corresponding subgroups of patients do not differ with respect to expression rates of drug transporters. Our results imply that parenchymal MRPs and Pgp are not responsible for drug resistance in resected tissue.

Intrameatal thrombosed anterior inferior cerebellar artery aneurysm mimicking a vestibular schwannoma.

Aneurysms of the anterior inferior cerebellar artery (AICA) are a rare entity. Purely intrameatal aneurysms are even rarer. The authors report an intrameatal thrombosed AICA aneurysm mimicking a vestibular schwannoma that was treated by resection and end-to-end anastomosis. This 22-year-old man presented with acute hearing loss, vertigo, and moderate facial palsy. Magnetic resonance imaging showed an atypical intrameatal lesion with dilation of the internal auditory canal. Microsurgical inspection via a retrosigmoid approach and drilling of the posterior wall of the internal auditory canal revealed a thrombosed AICA aneurysm. The aneurysm was excised, and an end-to-end suture was performed to restore AICA continuity. Intraoperative indocyanine green videoangiography as well as postoperative digital substraction angiography showed a good revascularization. Intrameatal AICA aneurysms may present with symptoms similar to vestibular schwannomas. End-to-end reanastomosis after aneurysm resection is a treatment option when clipping is impossible.