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PubMed2004

[Intraoperative auditory monitoring in acoustic neurinoma surgery].

Intraoperative auditory monitoring in acoustic neuroma surgery is used to improve residual hearing. Three techniques are available: monitoring of brainstem auditory evoked potentials, of electrocochleography or of direct eighth nerve compound action potential. The three techniques with their advantages and disadvantages are discussed. The current trend is to monitor brainstem auditory evoked potentials using digital filtering or to monitor the eighth nerve compound action potential.

Audiometry, Evoked Response↗
PubMed1996

Intraoperative auditory monitoring in acoustic neuroma surgery.

Intraoperative auditory monitoring is a useful adjunct that is currently evolving. Near-field monitoring techniques such as electrocochleography and direct eighth nerve compound action potential are being used more frequently. The use of these two techniques is compared in 26 patients undergoing hearing preservation acoustic neuroma resection. Overall, 9 (35%) of the 26 patients had their hearing preserved. Three (23%) of the 13 with electrocochleography monitoring and 6 (46%) of the 13 with direct compound action potential monitoring had hearing preserved after surgery. Although there was a suggestion of improved results with direct compound action potential monitoring, the results were not statistically different. It was noted that lack of electrical response at the completion of the procedure (regardless of monitoring technique) was correlated with poor postoperative hearing, whereas the presence of a waveform at termination in no way predicted satisfactory postoperative hearing. The two techniques and their advantages and disadvantages are discussed.

Action Potentials↗
PubMed2002

Anesthesia for intraoperative neurophysiologic monitoring of the spinal cord.

Intraoperative neurophysiologic monitoring (INM) using somatosensory and motor evoked potentials (MEPs) has become popular to reduce neural risk and to improve intraoperative surgical decision making. Intraoperative neurophysiologic monitoring is affected by the choice and management of the anesthetic agents chosen. Because inhalational and intravenous anesthetic agents have effects on neural synaptic and axonal functional activities, the anesthetic effect on any given response will depend on the pathway affected and the mechanism of action of the anesthetic agent (i.e., direct inhibition or indirect effects based on changes in the balance of inhibitory or excitatory inputs). In general, responses that are more highly dependent on synaptic function will have more marked reductions in amplitude and increases in latency as a result of the synaptic effects of inhalational anesthetic agents and similar effects at higher doses of intravenous agents. Hence, recording cortical somatosensory evoked potentials and myogenic MEPs requires critical anesthetic choices for INM. The management of the physiologic milieu is also important as central nervous system blood flow, intracranial pressure, blood rheology, temperature, and arterial carbon dioxide partial pressure produce alterations in the responses consistent with the support of neural functioning. Finally, the management of pharmacologic neuromuscular blockade is critical to myogenic MEP recording in which some blockade may be desirable for surgery but excessive blockade may eliminate responses. A close working relationship of the monitoring team, the anesthesiologist, and the surgeon is key to the successful conduct and interpretation of INM.

Anesthesia↗
PubMed1990

Thermally controlled laser irradiation of the myocardium with intraoperative ultrasound monitoring.

We used intraoperative ultrasonography (IOUS) to study the feasibility and safety of Nd:YAG laser irradiation of the myocardium in 26 canine left ventricular segments. During the laser irradiation process, the myocardial temperature was monitored and surface cooling was used. Afterward, intraoperative ultrasonographic scans, which enabled the evaluation of the irradiated lesions, were compared with cross sections made through the tissues. The total dose of laser energy ranged from 200 to 3,600 joules, and the estimated volume of irradiated lesions ranged from 76.8 to 2590 mm3. There were significant correlations between the laser discharge output (in joules [J]) and the irradiated lesion volume (P less than 0.001), and between the laser energy density (in J/mm2) and the depth of the lesions (P less than 0.01). Macroscopic examination of the cross sections of irradiated myocardium revealed that the lesions were well-demarcated, but not charred or perforated. Thus, we could obtain a satisfactorily large zone of laser photocoagulation without inducing tissue damage, if surface cooling was used and the myocardial temperature was monitored. IOUS was successful in visualizing and locating the irradiated lesions that were seen as hypoechoic, clearly outlined nodules. We submit that this study has established the technical feasibility and dose-response relationship of thermally controlled laser irradiation, and has demonstrated the usefulness of IOUS for the precise localization and monitoring of such laser treatment.

Animals↗
PubMedDate not supplied

[Intraoperative electroneurophysiological monitoring of basal cranial nerve surgery].

INTRODUCTION: Since 1980 when intraoperative monitoring was introduced or acoustic nerve surgery, the technique rapidly was outspreaded to the other basal cranial nerves, and today is the most important and indispensable piece of work first of all because of its effectiveness in the prevention of the neurologic deficits. OBJECTIVE: The aim of this work is to describe the basic requisites needed (personnel, equipment, stimulation and recording electrodes, patient handling), as well as to review the different techniques used (electromyography and electroneurography) in the motor cranial nerve monitorization (facial, motor trigeminal, extraocular muscles, glossopharyngeal, vagus, spinal accessory and hypoglossal) and the sensitive cranial nerves (optic, sensitive trigeminal, and acoustic) especially with evoked potentials. Finally, we pointed out the non-neurologic structures monitoring during the surgery of the posterior fossa.

Cranial Nerves↗
PubMedDate not supplied

Intraoperative neurophysiological monitoring. Part 2: Neurophysiological background.

Continuous intraoperative monitoring of neurophysiological signals provides a reliable way to determine the functional integrity of the nervous system during the course of neurological, orthopedic, or vascular surgery. To understand the use of electrophysiological recording in the operating room, the basic mechanisms that give rise to the recorded signals are briefly reviewed. Additionally, the equipment necessary for proper signal recording and presentation of the results is described. Finally, a short introduction to anesthesia management and some commonly induced neuroprotective conditions, such as hypothermia and hypotension, are provided, since these are the main factors affecting the signals, thus contributing to the difficulty of correct interpretation of the recordings during the course of an operation.

Anesthesia↗
PubMed1999

Intraoperative electrooculographic monitoring of oculomotor nerve function during skull base surgery. Technical note.

Intraoperative monitoring techniques for protecting the integrity of the oculomotor nerves during skull base surgery have been reported by several investigators, all of which involved the use of electromyographic responses to extraocular muscles. However, these techniques have not yet become popular because of the complexity of the procedures. The authors report an extremely simple and far more reliable technique in which electrooculographic (EOG) monitoring is used. The oculomotor nerves were stimulated with a monopolar electrode during skull base exposure. The polarity of the EOG responses recorded with surface electrodes placed on the skin around the eyeball yielded precise information concerning the location and function of the oculomotor and abducent nerves. In addition, with the aid of continuous EOG monitoring that detected transient changes in the background waves, surgical procedures that might impinge on oculomotor nerve function could be avoided. The present technique has been used in eight patients with skull base tumors and with it, the authors have achieved excellent results.

Electrooculography↗
PubMedDate not supplied

Intraoperative neurophysiologic monitoring: focus on cervical myelopathy and related issues.

BACKGROUND CONTEXT: The use of neurophysiologic monitoring during surgical procedures for cervical spondylotic myelopathy (CSM) is controversial. PURPOSE: The aim of this article is to review the literature regarding various monitoring techniques as applied to the patient with CSM. STUDY DESIGN/METHODS: A systematic literature review. CONCLUSIONS: Neurophysiologic monitoring is a diagnostic tool for assessment of neurologic function during cervical spine surgery. Recording of somatosensory evoked potentials (SSEPs), transcranial electrical motor evoked potentials (tceMEPs), and electromyograms (EMGs) may be useful as these monitoring modalities provide complementary information.

Anesthetics↗
PubMed1992

The case against intraoperative ECG monitoring.

It can be seen that ECG monitoring has its limitations; however, if it is employed correctly, it can be an invaluable adjunct to physical monitoring. The ECG does not provide information about the cardiac contractile state or hemodynamic status and may not always permit the facile resolution of dysrhythmias; however, in conjunction with other forms of cardiovascular monitoring, the ECG permits the anesthetist to have greater confidence in cardiovascular events occurring during anesthesia and permits the early detection and treatment of cardiac rhythm disturbances.

Anesthesia, General↗
PubMed2004

The use of evoked potentials in intraoperative neurophysiologic monitoring.

Although not universally adopted, the growing body of literature provides strong evidence of the clinical utility of IOM in a variety of cerebrovascular surgical and endovascular procedures. The Therapeutics and Technology Subcommittee of the American Academy of Neurology and Fisher et al concluded that the following are useful and noninvestigational: 1. EEG, compressed spectral array, and SSEP in CEA and brain surgeries that potentially compromise cerebral blood flow, 2. BAEP and cranial nerve monitoring in surgeries performed in the region of the brainstem or inner ear, 3. SSEP monitoring performed for surgical procedures potentially involving ischemia or mechanical trauma of the spinal cord. They also came to the conclusion that although promising, motor EPs and visual EPs are still investigational. Further investigation, especially in the area of outcomes research and cost-effectiveness, is required before IOM can become standard practice.

Arteriovenous Malformations↗
PubMed2001

Perioperative management of total parenteral nutrition, glucose containing solutions, and intraoperative glucose monitoring in paediatric patients: a survey of clinical practice.

Infants and children, particularly those who are chronically ill and maintained on total parenteral nutrition (TPN), are at risk for perioperative hypoglycaemia [blood glucose < 2.2 mmol x l(-1) (40 mg x dl(-1))] and hyperglycaemia [blood glucose > 11 mmol x l(-1) (200 mg x dl(-1))]. We surveyed paediatric anaesthesiologists regarding their perioperative management of blood glucose and TPN in paediatric patients to determine the current practice and its perceived success. Questionnaires were mailed to all members of the Study Group on Pediatric Anesthesia and the response rate was 70%. Results indicate that the current perioperative management of blood glucose and TPN is somewhat varied. Furthermore, greater than 10% of those surveyed report that their management results in a variable response in the maintenance of normoglycaemia. While the detrimental effects of perioperative hypoglycaemia and hyperglycaemia are rare, they are serious. A Medline search shows that no studies have been published regarding perioperative management of paediatric patients receiving TPN, although it appears that clinical study is warranted.

Blood Glucose↗
PubMed2001

A new technique for intraoperative visual monitoring during spinal surgery: angiofiber and endoscopic ultrasonography.

PURPOSE: This paper is focused on our clinical use of endoscopic ultrasonography (EUS) and angiofiber (AF) for spinal microsurgery. METHODS: EUS and AF were used in seven operations for syringomyelia and spinal tumor. We used EUS for extradural observation, and AF for extra and intra-dural, subarachnoid and intraluminal visual evaluation of the lesions. RESULTS: EUS images of the spinal cord, roots and lesions were clear, providing precise evaluation of the lesion and the course of the shunt tube in real time during surgery. AF could provide clear vision of the syrinx lumen or subarachnoid space. Because these fine instruments could be advanced under the unresected laminae, sonographic and endoscopic images were obtained from beyond the extent of laminotomy, where the microscope could not reach. CONCLUSION: Combined together, EUS and AF contributed to accurate and safe spinal surgery while minimising the laminotomy.

Adolescent↗
PubMed2001

Stereotactic guided laser-induced interstitial thermotherapy (SLITT) in gliomas with intraoperative morphologic monitoring in an open MR-unit.

Stereotactic guided laser-induced interstitial thermotherapy (SLITT) represents a minimal invasive method to produce necrosis in cerebral tumor tissue by local heating. The dose/response relationship relies on experimental studies and few clinical data performed in high field MR systems. A better understanding of the energy-dose/tissue response in human brain tumors is important to optimize this treatment modality. Twenty-four patients with gliomas were treated with SLITT, with a total of 30 laser procedures performed. Under local anesthesia 600 microns laser-fibers were inserted by stereotactic-guided technique into the center of the tumor. In a low field open MR system (0.2 T) the denaturation of the tumor using a neodymium YAG laser (1064 nm) was monitored by 3D-turbo FLASH T1-weighted sequences. Laser energy was applied in steps of 400 to 1200 Joules. Development of necrosis at a mean total energy dose of 2979 Joules could be monitored in all procedures. Two different thermal lesion architectures were observed. First signal changes were monitored after a mean of 1108 Joules and 1393 Joules, respectively. Mean max. total lesion size was 21.2 mm. The higher the total energy the larger was the thermolesion, but no linear relationship could be seen. Tumor tissue response showed no dependency on tumor grading. Monitoring of stereotactic guided laser-induced thermolesions in the low-power MR OPEN is feasible and safe. Although lesion size basically is energy dependent, it should be applied individually, since the thermal response in brain tumors varies due to different optical properties, even in the same tumor gradings.

Brain Neoplasms↗