ISSN:1077-2855    

出版商:OVID    

年代:2001

数据来源: OVID

ISSN:1077-2855    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Neurophysiological tests have improved the planning of a resection in patients with abnormalities near or involving eloquent cortex. With the use of these neurophysiological techniques, mapping of eloquent cortex in or near a planned resection is possible, allowing the neurosurgeon to optimize the resection, thus improving outcome and lessening morbidity. One type of neurophysiological test, evoked potentials (somatosensory, visual, and brainstem) allows one to identify somatosensory, primary visual or auditory cortex. The most common modalities are the somatosensory evoked potentials (SSEPs), in use for many years. The most frequently used are the median nerve SSEPs, but posterior tibial, ulnar and radial are a few of the other types that can be used. Over the years the techniques have been refined and the usefulness of the test has been demonstrated in both children and adults. With the widespread use of these techniques and with their use in combination with other techniques, what follows will serve as a review of the use of evoked potentials in cortical localization. This review will address the performance, pitfalls and special considerations of using evoked potentials in the operating room for cortical localization.

ISSN:1077-2855    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Cortical stimulation (CS) is important in planning epilepsy surgery in both adults and children. The goal of epilepsy surgery is seizure control without a significant neurologic deficit. The term eloquent cortex refers to cortical areas subserving the critical neurologic functions of motor, somatosensory, language, and memory. The identification of these areas is called cortical or functional mapping. CS may either activate or inhibit neurologic function from the stimulated area, thus identifying its function. CS also produces epileptiform activity, either spikes or sharp waves, called afterdischarges (ADs). The stimulation intensity that results in an AD is called the AD threshold. The techniques and precautions of CS are reviewed, including background electronic principles, stimulation parameters, and recording and testing methods, emphasizing its application to children. The immature cortex is more resistant to CS, which depends on the degree of myelination. Because more energy is needed to elicit a functional response in children, different stimulation parameters are used, especially a longer pulse duration. In addition, functional mapping in adults is generally performed at stimulation intensities below the AD threshold, whereas in younger children, functional responses may occur only above the AD threshold.

ISSN:1077-2855    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

This article describes two functional techniques for localizing eloquent cortical areas during surgery. The motivation for their use is derived from the inherent variability in cortical surface blood vessel and sulci pattern between patients; the distortion of the cortical surface from cortical masses; limited craniectomy size, which alters the perspective gained from surrounding cortical anatomy; and cortical plasticity of function, in which some functions relocate within the cortex when invaded by pathologic processes. The advantage of this approach is that maximum surgical removal of diseased tissue can occur while minimizing the risk of incurring new neurologic deficits. The first technique involves discrete electrical stimulation of the cortical surface. This approach has been used for localizing sensory, motor, and cortical areas important for speech function. The technique in most cases requires that the neurosurgical procedure be carried out on sedated patients. The second technique can be used to localize the central sulcus in both anesthetized and awake patients. It involves a morphologic analysis of the cortical surface somatosensory evoked potentials acquired when electrically stimulating contralateral peripheral nerves. The neurophysiologic basis for locating the central sulcus by finding the cortical surface where a phase reversal occurs in the distributed somatosensory evoked potentials is presented. Finally, practical aspects important for the successful use of both techniques are reviewed.

ISSN:1077-2855    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

A practical means of noninvasively stimulating the cortex was developed in the mid-1980s. Both electrical and magnetic stimulating pulses applied transcranially were shown to be capable of exciting motor cortex. Transcranial magnetic stimulation (TCMS), compared with transcranial electrical stimulation, produced relatively pain-free cortical excitation. This generated interest in developing clinical applications making use of TCMS. This article reviews the basic principles of perioperative TCMS. Two clinical applications that require TCMS are then discussed. The first involves the use of TCMS for monitoring the functional integrity of the spinal cord descending motor paths during surgery. Spinal cord motor path monitoring may have utility because several case reports have suggested that somatosensory evoked potentials may not always predict new postoperative motor deficits. The second application involves the use of discrete TCMS for localizing eloquent cortex in the preoperative period. The ability to define cortical areas functionally as they relate to surgical pathology is an invaluable aid for planning a surgical approach to their cure. A method under development at the authors' institution for correlating TCMS-derived functional data with anatomical data acquired from magnetic resonance imaging is described, and the use of this method for locating motor and visual association cortices is reviewed.

ISSN:1077-2855    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Conscious sedation can be defined as adequate sedation while maintaining verbal rapport, amnesia with the relief of anxiety, and analgesic supplementation with local or regional blocks. Verbal communication with the patient is particularly important. One criterion affecting the use of conscious sedation is the surgeon's familiarity with the technique. The anesthesiologist should have a thorough knowledge of the sedatives and analgesics administered. The ability to establish a patent airway and maintain oxygenation and ventilation as needed is essential. Conscious sedation is not suitable for every patient. It is most appropriate for the cooperative patient who has a thorough understanding of the planned anesthetic and surgery. With this knowledge, the patient then accepts it willingly. Intraoperative monitoring should include noninvasive oxygen monitoring with a pulse oximeter, blood pressure, end-tidal carbon dioxide, temperature, electrocardiogram, and the use of a precordial stethoscope. Resuscitation equipment should be immediately available. An appropriate level of consciousness implies that patients will be able to control their own airway and take deep breaths, as necessary. Level of consciousness should be assessed every minute whenever medications are being titrated. With the administration of medication, the patient's responses to verbal commands are delayed and responses are frequently slowed or slurred. Light tactile stimulation may be required to get the patient's attention. Sedative medications depress both hypoxic and hypercapnic ventilatory drives. Monitoring of ventilation provides the earliest indication of adequate gas exchange. This may subsequently lead to alveolar hypoventilation, apnea, airway obstruction, and hypoxemia. With appropriate intervention when these signs are first observed, the risk of adverse outcomes may be significantly reduced. Medications administered may directly depress cardiac function, so patients may be at increased risk for developing cardiac dysrhythmias during conscious sedation. Supplemental oxygen should be continued into the postanesthetic care unit. Patients must be monitored during the recovery period to ensure that any adverse events are rapidly recognized and appropriately treated. It is important to establish appropriate guidelines for discharge from the recovery area or the intensive care unit. The underlying condition, the type of sedation administered, and the nature of the procedure must be considered. Patients who have received respiratory antagonists must be observed for an appropriate period of time to ensure that respiratory depression does not recur.

ISSN:1077-2855    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

This article describes the use of 3D reconstruction for preoperative surgical planning and intraoperative navigation for cortical surgery. Before each surgical procedure, a detailed structural and functional model is reconstructed from magnetic resonance imaging scans and functional mapping modalities. These models, when integrated with direct intraoperative cortical mapping, create an integral 3D map of the cortical surface surrounding the lesion and its relation to the whole brain anatomy. A navigation system is coupled to the surgical field using skin-to-skin registration involving infrared light-emitting diode instrument tracking. This allows accurate guidance in the mapped 3D space. These detailed, patient-specific 3D maps of the brain are used as a method of accurately assessing the surgical approach, determining the potential neurologic risks, and navigating within the brain. One hundred fifty-five patients have been treated with this system for either preoperative planning or surgical navigation.

ISSN:1077-2855    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Resection, or even biopsy, of an intraaxial mass lesion in close relation to eloquent cortex carries a major risk for neurologic deficit. In such lesions, craniotomy under local anesthesia and monitored sedation is a safe technique that allows maximal resection of the lesion, with a low risk of new neurologic deficit. We have assessed the safety and effectiveness of this technique, demonstrated its usefulness in gross total or substantial tumor resection, found that there was no additional operative morbidity or usage of hospital resources. The technique also involves a level of stress that remains within the tolerance level of the average adult. Operating under local anesthesia proved an important tool for localization of function and exploration of eloquent cortex, as well as for the safe removal of epileptogenic areas. A number of other noninvasive strategies have been described and are currently the subject of great interest. Although these are promising new techniques, cortical mapping under local anesthesia was one of the most important steps in our progress toward a more exact localization of function in the cerebral cortex, and apart from a research tool in neurophysiology remains an important adjunct for the management of brain tumors by defining the limits of safe resection.

ISSN:1077-2855    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

The authors analyzed the outcome of 21 patients who underwent 24 craniotomies with intravenous sedation and brain mapping for the resection of brain metastases by the senior author from July 1995 through July 2000. All patients had tumors in close proximity to eloquent cortex including speech and sensorimotor areas. There were no perioperative deaths. Of 21 patients with neurologic deficits, there was complete resolution in 67%, improvement in 14%, and no change in 14% after surgery. Only one patient with preoperative hemiparesis sustained permanent neurologic deficit. The median length of stay was 3 days. The authors found awake craniotomy to be a safe procedure in patients with metastases sited in eloquent brain, with a low complication rate. Local anesthesia obviates the complications of general anesthesia, minimizes the hospital stay, and allows brain mapping to be performed during tumor extirpation. Most patients tolerated the procedure well, and none required conversion to general anesthesia. This technique should be part of every neurosurgical oncologist's repertoire.

ISSN:1077-2855    

出版商:OVID    

年代:2001

数据来源: OVID