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At least 631 records · Page 35Linked to original sources
PubMed1999

Minimally invasive stereotactically-guided extirpation of brain stem cavernoma with the aid of electrophysiological methods.

The surgical extirpation of brain stem cavernomas always includes a risk of neurological deficits. To minimize the risk of deficits and control the motor and sensory function intraoperative monitoring of SEP and MEP seems to be helpful. The high density of motor and sensory fibers within the brain stem makes bilateral intraoperative monitoring necessary. The following case demonstrates a stereotactically-guided supratentorial, transventricular approach for extirpation of a brain stem cavernoma. Sensory and motoric functions were observed by transcranial recording of SEP's and by transcranial stimulation of motor cortex.

Adult↗
PubMed1996

Intraoperative use of transcranial Doppler ultrasonography.

Transcranial Doppler (TCD) ultrasonography is a diagnostic tool that is well established in the fields of neurology and neurosurgery. There are many potential applications of TCD ultrasonographic monitoring in the perioperative care of the patient at risk of cerebral ischemia, the most important of which are detailed in this article. The introduction of TCD ultrasonography has made it possible to monitor intraoperative CBF changes in a continuous, noninvasive manner. Further refinement in the technology will delineate its appropriate use as an intraoperative monitor.

Brain Ischemia↗
PubMed1986

The value of intraoperative EEG monitoring during carotid endarterectomy.

Since controversy continues concerning the value of routine electroencephalographic (EEG) monitoring and selective carotid bypass shunting, we reviewed the neurological morbidity and mortality following elective carotid endarterectomy in 172 patients with symptomatic carotid occlusive disease. The use of EEG monitoring and selective shunting was associated with a reduction in the frequency of carotid shunts (49 to 12%) and a decline in combined major neurological morbidity and mortality (2.3 to 1.1%). We conclude that the routine use of intraoperative EEG monitoring is a valuable procedure, particularly in patients at high risk for perioperative neurological complications.

Aged↗
PubMed1996

Validity of SEP monitoring in carotid surgery. Review and own results.

OBJECTIVE: The sensitivity of intraoperative monitoring by means of somatosensory evoked potentials (SEP) in carotid surgery is to be examined. EXPERIMENTAL DESIGN: Prospective clinical investigation. In addition, the influence of circulatory parameters on SEP curves will also be tested. SETTING: Department of Surgery of a university clinic. MATERIALS AND METHODS: A total of 200 patients underwent intraoperative monitoring by means of somatosensory evoked potentials (SEP) during carotid endarterectomy between March 1, 1991 and August 1, 1994. MEASURES: In order to exclude blood pressure variations as a cause for amplitude changes the blood pressure and pulse were documented during the entire phase of preparation and clamping. RESULTS: A significant correlation could not be established between parameters of circulation and amplitude changes (r = 0.0026; p = 0.62). In seven cases of intraoperative amplitude reduction of more than 50% a stroke has been avoided by inserting a shunt. Despite the lack of an amplitude reduction, a watershed stroke of A.cerebri media and A.cerebri posterior occurred in two instances. Taking this into consideration the sensitivity of monitoring is 99.0% at a specificity of 100%. CONCLUSIONS: SEP-monitoring in carotid endarterectomy is simple to execute and is superior in sensitivity to EEG analysis. To avoid artefaction by anesthesia, a standard injection anesthesia is recommended. Farfield potentials should also be derived to avoid watershed infarctions.

Blood Pressure↗
PubMed2001

Reliability of intraoperative electrophysiological monitoring in selective posterior rhizotomy.

OBJECT: Selective posterior rhizotomy is a well-established treatment for spasticity associated with cerebral palsy. At most medical centers, responses of dorsal rootlets to electrical stimulation are used to determine ablation sites; however, there has been some controversy regarding the reliability of intraoperative stimulation. The authors analyzed data obtained from the McGill Rhizotomy Database to determine whether motor responses to dorsal root stimulation were reproducible. METHODS: A series of 77 patients underwent selective dorsal rhizotomy at a single medical center. The dorsal roots from L-2 to S-2 were stimulated to determine the threshold amplitude. The roots were then stimulated at 2 to 4 times the highest threshold with a 1-second 50-Hz train. A second stimulation run of the entire dorsal root was performed before it was divided into rootlets. Rootlets were individually stimulated and sectioned according to the extent of abnormal electrophysiological propagation. Motor responses were recorded by electromyography and were also assessed by a physiotherapist, and grades of 0 to 4+ were assigned. The difference in grades between the first and second stimulation trains was determined for 752 roots. Statistical analysis demonstrated a clear consistency in motor responses between the two stimulation runs, both in the electromyographic readings and the physiotherapist's assessment. More than 93% of dorsal roots had either no change or a difference of only one grade between the two trials. Furthermore, the vast majority of dorsal roots assigned a grade of 4+ at the first trial maintained the same maximally abnormal electrophysiological response during the second stimulation run. CONCLUSIONS: This study indicates that currently used techniques are reproducible and reliable for selection of abnormal rootlets. Intraoperative electrophysiological stimulation can be valuable in achieving a balance between elimination of spasticity and preservation of underlying strength.

Cerebral Palsy↗
PubMed2003

Transient paraplegia revealed by intraoperative neurophysiological monitoring: was it caused by the epidural anesthetic or an epidural hematoma?

IMPLICATIONS: Our case report describes the electrophysiological features associated with the development of a spinal epidural hematoma during surgery of the lumbar spine. It stresses the importance of the evaluation of nonsurgical factors, which can potentially affect intraoperative evoked potentials; in this case, epidural local anesthetic or epidural hematoma.

Adult↗
PubMed2004

Continuous monitoring of corneal thickness changes during LASIK with online optical coherence pachymetry.

PURPOSE: To assess the continuous intraoperative monitoring of central corneal thickness (CCT) changes during laser in situ keratomileusis (LASIK) using online optical coherence pachymetry (OCP). SETTING: Department of Ophthalmology, Vivantes Klinikum Neukolln, Berlin, Germany. METHODS: In this prospective nonrandomized comparative clinical case series of consecutive patients, 32 eyes having LASIK for myopia, myopic astigmatism, or hyperopia were continuously monitored intraoperatively in real time with online OCP integrated into a clinical excimer laser. The intraoperative values were compared to the postoperative flap and residual stromal thicknesses measured with corneal optical coherence tomography (OCT) as well as the calculated myopic ablation depth. RESULTS: Continuous monitoring with online OCP enabled intraoperative visualization of the CCT changes during LASIK. The CCT, flap thickness after the microkeratome pass, time-resolved ablation, and residual stromal thickness were assessed. Intraoperatively, the mean flap thickness was 135 microm +/- 38 (SD) and the mean residual stromal thickness, 286 +/- 59 microm. The mean intraoperative flap and residual stromal thickness values were 43.7 microm and 15.4 microm lower, respectively, than the postoperative values assessed with corneal OCT (P<.001 and P=.005, respectively). The optically determined myopic ablation depth was 118 +/- 37 microm, which was 28 microm higher than the nominal ablation depth. There was a significant correlation (P<.001) between the postoperative flap (r=0.79) and residual (r=0.88) thickness measured with corneal OCT as well as the calculated myopic ablation depth (r=0.95). CONCLUSIONS: Intraoperative online OCP could be an important safety feature to monitor the flap and residual stromal thicknesses during LASIK. The individual ablation depth and possible dehydration effects were also monitored continuously.

Adult↗
PubMed1992

Intraoperative and postoperative monitoring of microsurgical free tissue transfers.

Numerous techniques have been described for monitoring the postoperative viability of microsurgical free tissue transfers, and their sensitivity and reliability continue to be evaluated in animal experiments and clinical trials. Relative advantages and disadvantages of these various postoperative monitoring techniques are discussed. The concept of intraoperative monitoring of the microsurgical anastomoses during closure and inset of a free flap is introduced because many free flaps may fail on the operating table, but this only becomes clinically apparent several hours later in the early postoperative period.

Animals↗
PubMed2004

Brainstem auditory evoked potential monitoring during microvascular decompression for hemifacial spasm: intraoperative brainstem auditory evoked potential changes and warning values to prevent hearing loss--prospective study in a consecutive series of 84 patients.

OBJECTIVE: The nerve function of Cranial Nerve VIII is at risk during microvascular decompression for hemifacial spasm. Intraoperative monitoring of brainstem auditory evoked potentials (BAEPs) can be a useful tool to decrease the danger of hearing loss. The aim of this study was 1) to assess the side effects of surgery on hearing and describe the main intraoperative BAEP changes observed in the authors' series, and 2) to define warning values beyond which the probability of hearing impairment rises significantly. These values were calculated by correlating the (possible) postoperative hearing disturbances evaluated in terms of pure tone average with intraoperative BAEP changes (especially delay in Wave V latency). METHODS: This series included 84 consecutive patients affected with hemifacial spasm who underwent microvascular decompression during which BAEPs were monitored. During surgery, Wave I, I to V interpeak interval, latency, and amplitude of Wave V were recorded and measured. Auditory function was studied before and after surgery and expressed as a pure tone average in all patients. Then, correlations were made between hearing impairment after surgery and intraoperative BAEP changes in an attempt to define warning values. RESULTS: Seventy-four patients (88%) had no hearing loss after surgery (Group 1). Eight patients (9.5%) had hearing impairment with a decrease in pure tone average of more than 20 dB (Group 2). Two patients (2.3%) experienced a definitive and complete hearing loss on the side operated on (Group 3). Among intraoperative BAEP changes, latency of Peak V was the most frequently observed and the most significant phenomenon, especially during cerebellar retraction and the decompression step of the microvascular decompression procedure. In the group of patients without hearing loss (Group 1), the mean delay in latency of Peak V was 0.61 millisecond (standard deviation, +/-0.36 ms); in the group with hearing decrease (Group 2), the mean delay was 1.05 milliseconds (standard deviation, +/-0.64 ms); and in the group with deafness (Group 3), Wave V was abolished. CONCLUSION: From a practical standpoint, three warning values, based on delay in latency of Peak V, were established for use during surgery: an initial one at 0.4 millisecond ("watching" signal) at the safety limit; a second one at 0.6 millisecond (risk "warning" signal), which is the mean value corresponding to the group of patients without postoperative hearing loss; and an ultimate one at 1 millisecond ("critical" warning), before irreversibility. These warnings should help the surgeon to avoid or correct maneuvers that are dangerous for hearing function, which is mandatory in functional surgery.

Adult↗
PubMed1999

[Intraoperative electrophysiological monitoring for functional preservation of the cauda equina during lumbosacral surgery].

Adequate electrophysiological techniques to monitor function of the cauda equina have been proposed for surgery in patients with lumbosacral lipoma or myeloschisis. Motor fibers were identified by electrical stimulation in the operating field with bipolar rectangular impulses of 200 mu sec duration at 2 Hz under 5 mA and compound muscle action potentials (CMAPs) recorded from the leg and anal muscles. By recording CMAPs from the tibialis anterior, the biceps femoris, the gastrocnemius, and the external anal sphincter muscles, all of the roots from the fourth lumbar to the fourth sacral segment were continuously monitored. To spare recording channels, recordings were obtained from the right versus the left side. In our institute, 5 patients have undergone lumbosacral surgery while using this monitoring system, and the results indicated that there was no postoperative neurological exacerbation in any of the cases. According to a combination of the CMAPs produced by stimulation, the segment of the stimulated motor root could be identified electrophysiologically. Monitoring of somatosensory evoked potentials was not performed because this would have required too much time and would have prolonged surgery. However, some sensory fibers, which appeared to be posterior roots of the cauda equina on intraoperative inspection, could be identified indirectly with CMAPs recording because of current spreading from the stimulation to motor fibers.

Action Potentials↗
PubMed2005

Changes in transcranial motor evoked potentials during intramedullary spinal cord tumor resection correlate with postoperative motor function.

OBJECTIVE: Intraoperative monitoring of transcranial motor evoked potentials (TcMEPs) has been investigated recently as a means of preventing motor deficits associated with resection of intramedullary spinal cord tumors (IMSCTs). In this study, we hypothesized that changes in the intraoperative MEPs during tumor resection correlate with postoperative motor function deficits. METHODS: A retrospective record review was conducted for 28 patients who underwent resection of an IMSCT using myogenic or muscle-recorded TcMEPs during a 44-month period. Intraoperative MEP recordings and results from preoperative, immediate postoperative, and subsequent follow-up neurological examinations were analyzed. RESULTS: Of the 28 patients who underwent resection of an IMSCT using TcMEPs, MEP changes occurred in 13 patients (46%). Impaired motor conduction was detected by changes in pattern and duration of the MEP waveform morphology (polyphasic to biphasic in 9 patients and polyphasic to biphasic to loss of MEP response in 5 patients, 1 patient demonstrated both changes) and by an increase in voltage threshold (median, 175 V; range, 100-225 V; n = 22 extremities). Alterations in morphology and reduction in duration of the MEP response persisted despite significant increases in stimulation voltage. In 12 patients, reductions in the complexity and/or loss of the TcMEP waveform correlated with motor grade loss in the immediate postoperative period (P < 0.0001), at discharge (P < 0.001), and at follow-up (P < 0.001). The decrease in the duration of the response correlated with motor grade loss immediately after surgery (P < 0.001), at discharge (P < 0.0001), and at follow-up (P < 0.005). CONCLUSION: These results support the application of distal muscle-recorded TcMEPs to predict the occurrence and severity of postoperative motor deficits during resection of IMSCTs. Attention to such quantitative intraoperative monitoring data may help to minimize postoperative motor deficits by avoiding or correcting excessive spinal cord manipulation and modifying surgical technique during tumor resection.

Adult↗
PubMed1995

Neurophysiologic assessment in the management of spinal dysraphism.

Neurophysiologic techniques provide a valuable addition to the armamentarium of tools for the evaluation of sensory and motor function in the pediatric spinal cord. These techniques include median, radial, and ulnar nerve evoked potentials from the upper extremity; common peroneal and tibial nerve evoked potentials from the lower extremity; dermatomal potentials; and compound muscle action potentials and compound nerve action potentials. The techniques that evaluate the sensory system have been used extensively and effectively as research tools, as adjuncts to diagnostic evaluation, and for intraoperative monitoring. There is a considerable literature that describes the properties of SEPs in the infant and young child. Techniques for assessing the descending pathways have been developed in the last 10 years. These techniques hold great promise as both diagnostic and intraoperative monitoring tools. Many questions, however, still exist concerning their value and use. The rapidly increasing capability available in computer systems is also providing enhanced capability in the acquisition, display, and analysis of neurophysiologic data. It is now common to acquire multiple responses simultaneously, e.g. tibial SEPs, pudendal SEPs, and motor potentials. It is also possible to apply computationally intensive numerical algorithms in real time to enhance signal quality and reduce the time required to produce an interpretable display. Finally, it is possible to monitor multiple cases simultaneously from remote locations. These enhanced computational capabilities are helping to optimize the contribution of neurophysiologic monitoring to patient care.

Child↗
PubMed1996

[Intraoperative EEG monitoring in hemihepatectomies].

End-stage liver diseases are correlated with specific EEG changes. In chronic liver diseases normal EEG excludes hepatic encephalopathy. To date, it is not known at what time EEG changes appear in liver dysfunction and whether they are to be seen during the unhepatic phase in hemihepatectomies. To clarify this, we analyzed EEGs in 10 patients during hemihepatectomies with the CATEEM system. During the hemihepatectomies an occlusion of the liver hilus for 20-38 minutes (on average 28 minutes) was necessary. During and after the occlusion we found no changes in EEG. We conclude that brief failure of liver function under general anaesthesia is tolerated without danger to the central nervous system.

Adult↗
PubMed1992

Cerebral consequences of hypothermic circulatory arrest in adults.

Despite widespread use of hypothermic circulatory arrest (HCA) in aneurysm surgery and for repair of congenital heart defects, there is continued concern about possible adverse cerebral sequelae. The search for ways to improve implementation of HCA has inspired retrospective clinical studies to try to identify risk factors for cerebral injury, and clinical and laboratory investigations to explore the physiology of HCA. At present, risk factors associated with less favorable cerebral outcome after HCA include: prolonged duration of HCA (usually greater than 60 min); advanced patient age; rapid cooling (less than 20 min); hyperglycemia either before HCA or during reperfusion; preoperative cyanosis or lack of adequate hemodilution; evidence of increased oxygen extraction before HCA or during reperfusion; and delayed reappearance of electroencephalogram (EEG) or marked EEG abnormality. Strategies advocated to increase safety of HCA include: pretreatment with barbiturates and steroids; use of alpha-stat pH regulation during cooling and rewarming; intraoperative monitoring of EEG; slow and adequate cooling, including packing of the head in ice; monitoring of jugular venous oxygen content; hemodilution; and avoidance of hyperglycemia. Current investigation focuses on delineating the relationship of cerebral blood flow (CBF) to cerebral oxygen consumption and glucose metabolism during cooling, HCA, rewarming, and later recovery, and identifying changes in acute intraoperative parameters, including the presence of intracerebral enzymes in cerebral spinal fluid, with cerebral outcome as assessed by neurological evaluation, quantitative EEG, and postmortem histology. Clinically, intraoperative monitoring of EEG and measurement of CBF by tracer washout or Doppler flows are contributing to better understanding of the physiology of HCA, and in the laboratory, nuclear magnetic resonance (NMR) spectroscopy has provided valuable insights into the kinetics of intracerebral energy metabolism. Promising strategies for the future include investigation of other pharmacological agents to increase cerebral protection, and use of "cerebroplegia" or intermittent perfusion between intervals of HCA to improve cerebral tolerance for longer durations of HCA.

Animals↗
PubMed1988

Rapid monitoring of intraoperative cerebral blood flow using 133Xe.

This study examined the feasibility of rapid rCBF monitoring using 133Xe as a tracer during operative procedures. We compared the initial slope index derived from two bicompartmental and one monocompartmental physiological models. The single-compartment model requires only 3 min of monitoring, whereas the bicompartmental models, thought to be more reliable, require 11 min of clearance. Data were collected from 26 patients undergoing carotid endarterectomy. Approximately 20 mCi of 133Xe in saline was injected i.v. for up to five measurements per patient, for a total of 117 measurements. The robustness of the regression for the three parameters (r = 0.781-0.99, p less than 0.0001) suggests that the three parameters are closely related. This is supported by similarity of the slopes of the regression lines (between 0.944 and 1.25) and the mean +/- SD of the three rCBF models (24.9-27.5 +/- 12.0-14.3 ml 100 g-1 min-1). Similar results were obtained for individual detectors, despite the expected higher variability. For intraoperative use in surgical procedures in which physiological conditions may change rapidly and i.v. injections of tracer must be used, a rCBF index that quickly and accurately reflects flow conditions is useful. Our data suggest that the single-compartmental Wyper index may be used to provide information about cerebral perfusion that is as accurate and robust as bicompartmental models, but requires only one-quarter of the data collection time.

Cerebrovascular Circulation↗
PubMed1995

Intraoperative reflectance oximetry in burn patients.

OBJECTIVE: Transmission oximetry sites for intraoperative monitoring are frequently difficult to find in burn patients, as standard transmission oximetry sites are often burned or contained within the operative field. The objective of this study was to determine if reflectance oximetry is of potential value in monitoring this group of patients. METHODS: A total of 16 operative procedures in a group of acutely burned adult and pediatric patients with an average age of 9.7 years (range, 10 months to 37 years), average burn size of 42% of the body surface (range, 15% to 94%), and average weight of 34.2 kg (range, 9 to 100 kg) were done with simultaneous transmission and reflectance oximetry monitoring. RESULTS: During these 16 procedures in a diverse group of acutely burned adult and pediatric patients, there was no significant difference in saturations derived from transmission and reflectance oximetry probes. In smaller children, adequate signal for reflectance probe monitoring was often detected in hyperemic sites, such as healed partial thickness burn. CONCLUSIONS: This is the first published report documenting both the clinical use of the reflectance oximetry in burn patients and the clinical use of the Nellcor Oxisensor II RS-10 reflectance oximetry probe (Nellcor Corporation, Hayward, CA). This technique can facilitate the intraoperative monitoring of acutely burned adult and pediatric patients in whom standard transmission oximetry sites are difficult to find.

Adult↗