Neurosurgical Devices Research Articles

Coagulase-Negative Staphylococcal Meningitis in Adults: Clinical Characteristics and Therapeutic Outcomes

We wanted to analyze the clinical characteristics and therapeutic outcomes of adult meningitis caused by coagulase-negative staphylococci (CoNS). Over a period of 5 years (January 1999 to December 2003), 127 cases were identified as having adult culture-proven bacterial meningitis caused by a single pathogen. Of them, 14 cases with CoNS meningitis were enrolled, and their clinical characteristics and therapeutic outcomes were analyzed. The 14 cases (median age 37.5; range 24-77 years old) included nine men and five women. With polynerase chain reaction sequencing of bacterial 16S r-RNA, 10 of the 14 CoNS strains were identified as Staphylococcus epidermidis infection, and the other four belonged to Staphylococcus haemolyticus. All 14 cases were in a postneurosurgical state with insertion of a ventriculoperitoneal shunt, external ventricular device or intrathecal port A as their underlying conditions, and 12 of the 14 patients contracted the infection nosocomially. Fever (86%), leukocytosis (79%), hydrocephalus (50%), consciousness disturbance (36%), and seizure (7%) were the major clinical manifestations. All the involved CoNS strains showed resistance to oxacillin but retained their susceptibility to vancomycin and linezolid. All 14 CoNS strains had positive mecA gene detection. With the removal of neurosurgical devices and intravenous vancomycin therapy, 86% (12/14) of the patients survived. CoNS meningitis accounted for 11% (14/127) of our adult bacterial meningitis. All adult CoNS meningitis patients had a disrupted barrier of the central nervous system as the underlying condition. S. epidermidis was the most common CoNS subtype involved. All involved CoNS strains were oxacillin resistant. The therapeutic result showed that adult CoNS meningitis had a mortality rate of 14% (2/14).

Device-Related Infections: A Review

The use of surgically implanted devices has increased as a result of their beneficial effect on quality of life, and in some circumstances, on patient survival rates. They can, however, be associated with a variety of complications, the most dreaded being infection. Device-related infections are important to understand because of the morbidity and mortality associated with them. Frequently, patients are managed with hospitalization, prolonged courses of antibiotics, and surgical interventions, all of which can negatively impact on patients' quality of life. Such care is also associated with increased costs to health care systems. Furthermore, these infections often represent a diagnostic challenge because of the lack of consensus definition of what constitutes an infection and its severity, as well as the paucity of well-designed, large studies addressing optimal methods of investigation and management. An implant-associated infection is defined as a host immune response to one or more microbial pathogens on an indwelling implant. An understanding of the pathogenesis of these infections provides a rationale for management. Development of device-related infections begins with colonization of the foreign material, followed by a complex metamorphosis by the microorganisms with resultant biofilm formation. In this surface-associated form, bacteria have altered phenotypic properties. This change, in conjunction with the physical protective layer provided by the biofilm, renders antimicrobial therapy ineffective when used alone. Because the microorganisms are able to reside on the hardware, they proliferate and cause local damage, such as loosening of implanted devices, wound dehiscence, or disruption of prosthetic valves, as well as systemic manifestations, such as fever or embolic phenomenon. The onset and clinical manifestations of device-related infections vary with the pathogen involved, as well as which component of the device is affected. The time period after device implantation that signs and symptoms develop can assist in the selection of empiric antimicrobial therapy. Optimal diagnostic microbiologic specimens are paramount in tailoring the antimicrobial therapy, which almost always has to be given for a prolonged period of time. Surgical removal of the device is usually necessary. Some studies of limited types of device-related infections, however, have defined indications for which salvage therapy may be warranted. In addition, some patients are not candidates for, or may not want, further surgical interventions, in which case indefinite suppressive antimicrobial therapy may be considered. This review provides an overview of infections related to various neurosurgical, cardiac, and orthopedic devices, as well as those related to cochlear, breast, and penile prostheses, with discussion of definitions of such infections, along with microbiology, pathogenesis, and management guidelines, including the limited indications for salvage techniques.

Development of coordinate system of stereotactic neurosurgical device for intraoperative MRI

Intraoperative magnetic resonance (MR) imaging was used to evaluate the extent of a resection, mainly in pituitary, brain tumor and epilepsy surgery. This paper summarizes some of our experience gained in 300 patients, which were investigated by intraoperative MR imaging. In addition to MR imaging, functional data from magnetoencephalography and functional magnetic resonance imaging, resulting in so-called functional neuronavigation, were visualized intraoperatively, when lesions near eloquent brain areas were operated on. Both methods could be integrated in our intraoperative setup with a new navigation microscope that could be used at the 5 Gauss line. The combination of both methods offers the possibility to perform more radical resections without additional morbidity. Intraoperative MR imaging serves as quality control to evaluate the extent of a resection, while functional neuronavigation prevents too extensive resections that could result in neurological deficits.

Pulsed liquid jet dissector using holmium:YAG laser--a novel neurosurgical device for brain incision without impairing vessels.

Neurosurgery has long required a method for dissecting brain tissue without damaging principal vessels and adjacent tissue, so as to prevent neurological complications after operation. In this study we constructed a prototype of such a device and used it in an attempt to resect beagle brain cortex. The prototype device consisted of an optical fibre, a Y adaptor, and a nozzle whose internal exit diameter was 100 microm. Cold physiological saline (4 degrees C) was supplied to it at a rate of 40 ml/h. Pulsed liquid jets were ejected from the nozzle by a pulsed Holmium:YAG) (Ho:YAG) laser at an irradiation energy of 300 mJ/pulse. The profile of the liquid jet was observed with a high-speed camera while changing the distance between the optical fibre end and nozzle exit (equivalent to the standoff distance). With this device (3 Hz operation), brain dissection of anaesthetized beagles was attempted while measuring the local temperature of the target. A histological study of the incised parts was also performed. When the standoff distance was 24 mm, the liquid jet was emitted straight from the nozzle at a maximum initial velocity of 50 m/s. The brain parenchyma was cut with this device while preserving vessels larger than 200 microm in diameter and keeping the operative field clear. The local temperature rose to no more than 41 degrees C, below the functional heat damage threshold of brain tissue. Histological findings showed no signs of thermal tissue damage around the dissected margin. The Ho:YAG laser-induced liquid jet dissector can be applied to neurosurgery after incorporating some minor improvements.

Comparison of brain tissue and local cerebral venous gas tensions and pH

Neurosurgical monitoring devices have recently become available which are capable of measuring cerebral tissue gas tensions and pH. Brain tissue sensors have not been conclusively demonstrated to correlate with other measurements of regional cerebral gas tensions or pH. The present study was undertaken to correlate sensor values for p 02/ p C02 and pH with blood samples taken concurrently from local cerebral veins. Adult mongrel dogs were anesthetized and a craniotomy was performed. A small gyral vein was isolated and cannulated. Adjacent to the venous catheter tip, a Neurotrend® brain tissue probe was inserted in an intracortical location. Each subject received a sequence of manipulations in inspired oxygen and end tidal carbon dioxide conditions. Under each experimental condition, samples of arterial and gyral venous blood were obtained and blood gas analysis performed. Concurrent brain probe measurements of tissue p02, pC02 and pH were recorded. Statistical analysis determined that local tissue and cerebral venous blood values for p02, pC02 and pH were highly correlated (Rs= 0.62-0.82; p 0.001). This indicates that there exists a confirmable monotonic relationship between tissue values and conditions in the post-capillary venous bed. Tissue sensors such as the Neurotrend® probe can offer reliable trend indications in brain tissue gas tensions and pH. [Neurol Res 2000; 22: 642-644

Safe superconducting current discharge for the magnetic stereotaxis system

The Magnetic Stereotaxis System is a unique neurosurgical device designed to provide surgical treatment of regions of the brain normally inaccessible with contemporary techniques. By magnetically propagating a small (approximately 5 mm length, approximately 3 mm diameter) magnetic implant and attached catheter through the brain under near real-time fluoroscopic guidance while referencing preoperative magnetic resonance imaging scans, both precision surgery and drug therapy can be applied to specific sites in the brain while circumventing the blood-brain barrier. Given the high current requirements for the proper operation of the system, a hazard exists in which a coil may fail by either a coil quench or a magnet system shutdown. A silicon controlled rectifier switch and varistor combine to circumvent this threat by controlling the current discharge, thereby preventing damage to the cryogenic system while simultaneously protecting the patient. Analysis reveals that of the failures that may occur in the volume occupied by the brain, a field direction variation of up to 150 at a magnitude of 0.10-0.15 T results for 70% of the casts, 0.15-0.20 T for 50%, 0.20-0.25 T for 25%, and 0.25-0.30 T for 5%. In no circumstance does the force magnitude increase.

Software safety in medical applications.

The use of software in safety-critical medical applications permits sophisticated functionality that would otherwise not be achievable. However, it is very difficult to ensure that software in these systems is dependable. In particular all software development techniques have limitations, and none can provide any guarantee of overall software dependability. Given this shortcoming, the approach that we have taken is to develop techniques that emphasize the verification of properties that are important to overall software dependability. In this paper we describe two techniques that support the implementation and verification of dependable software for an experimental neurosurgical device and safety-critical applications in general. The first technique involves the assurance of critical safety properties by a relatively simple software component known as a safety kernel. Situated between the application software and the application devices, the safety kernel enforces rules that govern the safe operation of the devices. The simplicity of the safety kernel facilitates its implementation and verification. In most cases, it is not possible to rely on testing to provide the necessary verification of the software in a safety-critical application. However, testing can play an appropriate and vital role in the demonstration of safety properties. The second technique takes this approach, utilizing automated testing and selected test cases to demonstrate useful system properties.

Pharmacokinetics of intraventricular administration.

The widespread use of neurosurgical devices for intraventricular drug delivery has led to an escalation in the number of CSF pharmacokinetic studies. When experimental data for ventricular CSF concentration vs. time are normalized for dose and plotted for drugs with a wide range of physical properties, there is a remarkably narrow range. Simulations from a distributed model for the central nervous system suggest that the narrow range of observed CSF half-times following bolus administration is a consequence of physiologic limits upon rate of drug removal from CSF. Whereas bulk flow of CSF establishes minimum rate of drug washout, diffusion through brain tissue and subsequent removal by capillaries establishes a maximum rate of drug egress which is only seven times the minimum rate. Predictions of CSF concentration vs. time can be made based upon the capillary exchange rate for a particular drug, which could be estimated or calculated from CSF concentration measurements following systemic administration. Simulations are also presented of steady-state CSF concentrations during continuous ventricular infusions.

Neurosurgical devices and drugs

Neurosurgical devices and drugs

Neurosurgical devices and drugs

Neurosurgical devices and drugs

Neurosurgical devices and drugs

Neurosurgical devices and drugs

Neurosurgical devices and drugs

Neurosurgical devices and drugs

Neurosurgical devices and drugs: standardizing intracranial shunts; CT scanning; unnecessary X-ray films of the skull.

Neurosurgical devices and drugs: standardizing intracranial shunts; CT scanning; unnecessary X-ray films of the skull.

Neurosurgical devices and drugs

Neurosurgical devices and drugs

Neurosurgical devices and drugs

Neurosurgical devices and drugs

Neurosurgical devices and drugs.

Neurosurgical devices and drugs.

Neurosurgical devices and drugs

Neurosurgical devices and drugs

Neurosurgical devices and drugs

Neurosurgical devices and drugs

Neurosurgical materials and devices.

Computerized tomography (CT) images are created by computer and as such are inherently amenable to computer image processing techniques. Advances have been made in the areas of alternative visualization (coronal views, etc.), image enhancement, feature extraction, and computer analysis of the extracted information. Further advances await imaginative application of these techniques and time; others will depend upon necessary advances in image processing methods.

Neurosurgical materials and devices

Neurosurgical materials and devices