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Neurophysiological monitoring of spinal cord function during instrumented anterior cervical fusion.

BACKGROUND CONTEXT: Somatosensory evoked potentials (SSEPs) monitor global spinal cord function, and the interpretation of motor loss is based on inferred rather than direct measurements. Therefore, SSEPs may not be useful for identifying motor function deficits caused by anterior spinal column injury or nerve root injury during decompression or placement of instrumentation. For these reasons, adjunctive methods for monitoring may be especially useful during cervical spine surgery. PURPOSE: To evaluate the effectiveness of SSEP and transcranial electrical motor evoked potential (tceMEP) monitoring of spinal cord function during anterior fusion of the cervical spine. STUDY DESIGN/SETTING: Retrospective review. PATIENT SAMPLE: Consecutive instrumented, anterior cervical spine surgeries performed by the same surgeon at a single institution for 119 patients. OUTCOME MEASURES: Record of neurophysiological alerts during surgery and record of postoperative neurological deficits not present before surgery. METHODS: Spinal cord function was monitored intraoperatively with recordings of ulnar and posterior tibial nerve SSEPs and tceMEPs. RESULTS: Six neurophysiologic alerts occurred that prompted surgeon and/or anesthesiologist intervention. Three patients developed new motor weakness after surgery. One patient had temporary right-leg weakness that was predicted accurately by the disappearance of the right lower extremity tceMEPs. One patient had additional temporary postoperative compromise of the right C5-C6 spinal nerve roots that could not be detected intraoperatively because of absent baseline tceMEPs from the affected muscles. For one patient who developed quadriparesis postoperatively, tceMEP monitoring was precluded by the excessive use of neuromuscular blockade during the procedure. CONCLUSIONS: The results illustrate the potential utility of intraoperative SSEPs and the tceMEPs for detection of changes in spinal cord function related to patient positioning and hemodynamic effects during anterior cervical fusion.

Adult↗
PubMed2003

Application of time-frequency analysis to somatosensory evoked potential for intraoperative spinal cord monitoring.

OBJECTIVE: To investigate the improvement in the reliability of intraoperative spinal cord monitoring by applying time-frequency analysis to somatosensory evoked potentials (SEP). METHODS: 34 patients undergoing scoliosis surgery were studied. SEP were recorded during different stages of scoliosis surgery. Averaged SEP signals were analysed intraoperatively by short time Fourier transform (STFT). The time-frequency characteristics of SEP were observed during surgery. The main peak in the time-frequency interpretation of SEP was measured in peak time, peak frequency, and peak power. The changes in these variables were compared with the changes in latency and amplitude during different surgical stages. RESULTS: During different surgical stages, changes in peak times and peak powers were found to correlate with the changes in latency and amplitude, respectively. Peak time showed more variability than latency (p < 0.01), while peak power showed less variability than amplitude (p < 0.01). The peak frequency of SEP appeared to be unchanged during surgery. SEP signals were found to have specific time-frequency characteristics, with the time-frequency distribution of the signals being located in a particular time-frequency space. CONCLUSIONS: Time-frequency analysis of SEP waveforms reveals stable and easily identifiable characteristics. Peak power is recommended as a more reliable monitoring parameter than amplitude, while peak time monitoring was not superior to latency measurement. Applying time-frequency analysis to SEP can improve the reliability of intraoperative spinal cord monitoring.

Adolescent↗
PubMed1999

Intraoperative enzyme-amperometric monitoring of extracellular glutamate concentration with a dialysis electrode in ischemic human brain.

Changes in the extracellular concentration of glutamate in the brain ([Glu]e) were monitored continuously by an enzyme-amperometric technique employing a dialysis electrode during ischemia caused by isolation of the brain tissue in rats and human patients. In the rat (n = 10), the dialysis electrode was placed in the frontal cortex and the frontal lobe was transected. A transient sharp increase in [Glu]e was frequently observed during the transection. A biphasic elevation (a rapid increase followed by a slowly continuing increase) subsequently occurred with a latent period of 1-3 min after the transection of the rat frontal lobe. In patients (n = 7), the dialysis electrode was placed in tumor-free cortical areas which were planned to be resected together with gliomas. Progressive increases in [Glu]e were observed in all of the patients as the isolation of the brain tissue progressed. A biphasic increase, similar to that seen in the rat, was identified in 2 patients in whom the cortical area surrounding the dialysis electrode was rapidly isolated. The present enzyme-amperometric technique employing a dialysis electrode appears to be useful for detecting the occurrence of potentially harmful ischemia and for securing minimal metabolic stress caused during various surgical manipulations.

Animals↗
PubMed2004

Critical pathways can improve results with carotid endarterectomy.

Approximately 10 years ago, the Section of Vascular Surgery at Pennsylvania Hospital reported results of critical pathways that we developed for all major vascular operations, including carotid endarterectomy (CEA). After implementing these pathways, we then developed a specific five-step protocol to further improve results and decrease costs for elective CEA. With the advent of carotid artery balloon angioplasty and stenting (CABAS), CEA has come under increasing attack by endovascular interventionalists. We believe our regimen remains the gold-standard against which CABAS should be compared. Our five-step CEA protocol includes: (1) duplex ultrasonography performed in an accredited vascular laboratory as the sole diagnostic carotid preoperative study, (2) admission the day of surgery, (3) cervical block anesthesia to eliminate intraoperative electroencephalographic monitoring and other costly intraoperative monitoring tests, (4) transfer from the recovery room after a short observation period to the vascular ward, and (5) discharge the first postoperative morning. Since this 5-step protocol was implemented several years ago, we have found it to be safe and cost-effective, and now represents the standard against which CABAS should be compared.

Aged↗
PubMed2000

[Accuracy of intraoperative urinary bladder temperature monitoring during intra-abdominal operations].

OBJECTIVE: This study investigates whether the site of abdominal surgery or the urine flow rate affects the accuracy of urinary bladder temperature monitoring. METHODS: After approval by the local ethics committee we studied 7 patients during upper abdominal and 10 patients during lower abdominal surgery. Temperatures were recorded with a Hi-Lo Temp Esophageal-Stethoscope (Mallinckrodt Medical) and a Foley Catheter Temperature Sensor FC400-18 (Respiratory Support Products, Mallinckrodt Medical). Each probe and its recording unit were calibrated over a range of 30-40 degrees C against a reference quartz thermometer (Hewlett Packard Model 2801 A) in a water bath before the investigation. Urine flow rate was measured using a urometer. Temperatures and urine flow rate were recorded every 30 min. Agreement between the methods of measurement was assessed as described by Bland and Altman. RESULTS: 124 measuring points could be analyzed. Bladder temperature had a bias (B) of -0.06 degree C compared to oesophageal temperature. Limits of agreement (LOA; +/- 2 s) were +/- 0.68 degree C. In upper abdominal surgery (B: 0.02 degree C; LOA: +/- 0.42 degree C) a higher precision of oesophageal temperature estimation could be demonstrated compared to lower abdominal surgery (B: -0.14 degree C; LOA: +/- 0.82 degree C). Lower urine flow rates generally increased the limits of agreement. Regarding lower abdominal surgery the bias additionally increased to -0.22 degree C. CONCLUSION: Urinary bladder temperature recording is a clinically acceptable method to measure core temperature during abdominal surgery. The accuracy during lower abdominal surgery is decreased compared to upper abdominal surgery, especially in case of a urine flow rate below 250 ml/h.

Abdomen↗
PubMed2005

Industry perspective: maximizing the benefit of improved detection with guided and monitored thermal ablation of small tumors.

The continuous growth of mammography is driven by global acceptance of the demonstrated ability of screening mammography to reduce mortality from breast cancer. An increasing number of benign and malignant tumors are being diagnosed as a result of the growth in mammography, improvements in technology, especially digital mammography, as well as by an increase in patient surveillance. Breast imaging technology for cancer screening continues to improve, with the integration of ultrasound with digital mammography showing promise that an even larger number of small abnormalities will be detected in screening programs. The results of minimally invasive ablative techniques as tested in pilot clinical studies for breast tumor ablation are reviewed. A new x-ray based thermal monitoring method is described. An improved ability to intraoperatively monitor thermal ablative methods may enable more accurate minimally invasive treatment of an ever increasing number of both benign and malignant breast tumors.

Breast Neoplasms↗
PubMed1994

Intraoperative motor and sensory monitoring of the cauda equina.

A set of standard techniques to monitor the motor and sensory function of the cauda equina is proposed for surgery in the lumbosacral spinal canal for the release of a tethered cord or the removal of a neoplasm. Continuous loudspeaker-controlled recording of electromyographic activity in four leg muscles of both sides supplied the surgeon with immediate feedback on injury to any of the motor roots from the second lumbar to the fourth sacral segment. Continuous recording of tibial nerve somatosensory evoked potentials yielded information about the functional state of parts of the lumbosacral sensory pathways. Motor roots could be identified by electrical stimulation in the operating field with bipolar stimulation forceps and recording of compound muscle action potentials from the leg muscles. Sensory nerve roots could be identified by nerve root somatosensory evoked potentials recorded from the scalp after the electrical stimulation of the exposed nerve. This set-up is a combination of previously developed monitoring techniques and provides the surgeon with functional information: 1) continuous feedback on the state of the endangered motor and sensory function of the cauda equina; and 2) rapid anatomical identification of nerve roots and their distinction from fibrous or neoplastic structures.

Adolescent↗
PubMed1999

[Complications of PPP: prevention and management strategies].

OBJECTIVE: In order to minimize the complications of palatopharyngoplasty (PPP). METHOD: Perioperative complications of PPP of 110 cases were analysed. RESULT: In our series, the complications included velopharyngeal insufficiency (28 cases), hypertensive crisis (12 cases), respiratory embarrassment (12 cases), wound dehiscence (2 cases), local hemorrhage (1 cases), hypovolemic shock (1 cases) and nasopharyngeal stricture (1 cases). CONCLUSION: It is concluded that prevention is important. Prevention strategies included: 1. Preoperative careful examination; 2. Using local anesthesia; 3. Intraoperative monitor ECG, blood pressure and oxygen saturation; 4. Intraoperative inbreathing oxygen; 5. Staunch blood thoroughly; 6. Postoperative proper treatment with steroid; 7. CPAP treatment should be applied before PPP in the severe OSAS.

Adult↗
PubMed2003

Do intraoperative microrecordings improve subthalamic nucleus targeting in stereotactic neurosurgery for Parkinson's disease?

AIM: The clinical importance of intraoperative microrecordings for subthalamic nucleus (STN) localization in neurosurgical practice remains a matter of debate in the various groups. METHODS: To investigate their usefulness in localizing the STN, we retrospectively evaluated how intraoperative microelectrode recordings changed the targeting of the STN estimated only on intraoperative stimulation and neuroanatomic targeting procedures. For neuroradiologic targeting of the nucleus we used a TC-MRI fusion algorithm and direct visualization of the STN. Besides standard microrecordings we also analyzed the power spectral density (PSD) pattern of physiological signals along the track and its neuroanatomic and clinical correlations. RESULTS: In our series of 12 patients with Parkinson's disease undergoing surgery for implantation of deep-brain stimulation (DBS) electrodes in the STN we found that in 25% (1/4) of patients, microrecordings determined the choice of the optimal track. In all the tracks analyzed the PSD peak coincided with the point selected for the final electrode implantation on the basis of the standard procedure for intraoperative monitoring based on both microstimulation and recordings. CONCLUSION: Intraoperative microrecordings are of determinant importance for accurate STN localization and are essential for optimal results in neurosurgical practice. PSD analysis is a simple and quick quantitative signal descriptor that will probably provide even more precise, simple and rapid tool for intraoperative neurophysiological localization of the STN.

Electrodes, Implanted↗
PubMed1994

A new method for intraoperative recurrent laryngeal nerve monitoring.

The recurrent laryngeal nerve is at risk of iatrogenic injury during surgical procedures in which its anatomical location is exposed. Borrowing from biotechnology currently available for facial nerve monitoring, we have developed a method of electrophysiologically assessing the function of the recurrent laryngeal nerve during technically difficult neck surgeries. Electromyographic as well as nerve action potential recordings are monitored using the Xomed-Treace Nerve Integrity Monitor-2 (NIM-2). This method differs from those previously published in that it is much less cumbersome and time-consuming. The technique as well as an illustrative case are reported.

Adult↗
PubMed2003

[Intraoperative detection of ischemic brain hypoxia using oxygen tissue pressure microprobes].

OBJECTIVE AND IMPORTANCE: Detection of intraoperative ischemic events could lead to the resolution of their cause and to the prevention of the definitive establishment of a postoperative infarct. We want to illustrate the possibilities that intraoperative monitoring of oxygen tissue pressure (PtiO2) in critical areas during a neurosurgical vascular procedure offers, enhancing its reliability and immediacy in obtaining information about tissue oxygenation status as a marker of ischemia in the vascular territory at risk. CLINICAL PRESENTATION: We report the case of a 32 year-old male with a deep arteriovenous malformation (AVM) localised in the insular region. The patient had been previously treated with radiosurgery without achieving a satisfactory result. INTERVENTION: AVM removal was performed through a transylvian transinsular approach. PtiO2 was monitorised at the temporal pole (reference area) and at the posterior temporal region (risk area). Both probes maintained close tissue oxygenation levels until the last stage of the AVM resection when, during the coagulation of a supposed afferent vessel, a brisk fall of the oxygen tissue pressure in the posterior temporal region was detected. An ischemic infarct in this area was observed postoperatively. CONCLUSIONS: PtiO2 monitoring has a high reliability in the detection of intraoperative tissue hypoxia. Data obtained could lead to early identification of these events and, whatever possible, to resolve this situation preventing the definitive establishment of an ischemic infarct.

Adult↗
PubMed2004

Impact of intraoperative parathyroid hormone monitoring on the prediction of multiglandular parathyroid disease.

Optimal interpretation of the results of intraoperative parathyroid hormone (IOPTH) monitoring during neck exploration for primary hyperparathyroidism (pHPT) is still controversial. The reliability of the "50% rule" in multiglandular disease (MGD) is often disputed, mostly because of competing pathophysiologic paradigms. The aim of this study was to ascertain and corroborate the ability of IOPTH monitoring to detect MGD in a practice, combining conventional and alternative parathyroidectomy techniques. This is a retrospective single institution analysis of 69 consecutive patients undergoing cervical exploration for pHPT by various approaches. The IOPTH measurements were performed after induction of anesthesia but prior to skin incision and 10 minutes after excision of the first visualized enlarged parathyroid gland. In this series, 55 patients (80%) had single adenomas, and 14 patients (20%) had MGD. In 8 of the 14 patients with MGD, IOPTH levels were obtained sequentially after removal of every enlarged gland. Of these 8 patients, 6 (75%) had a false-positive decrease (decrease below 50% of baseline value in presence of another enlarged gland) failing to predict the presence of a second enlarged gland. In 2 cases IOPTH monitoring provided a true-negative result, correctly predicting MGD. If MGD is defined by gross morphologic criteria, IOPTH monitoring fails to predict the presence of MGD reliably. However, if MGD is defined by functional criteria, the course of these patients does not seem significantly affected. The importance of these findings must be further investigated, especially with regard to the outcome of minimally invasive parathyroid procedures.

Adenoma↗
PubMed1984

Intraoperative evoked potential monitoring of the spinal cord: enhanced stability of cortical recordings.

Intraoperative EP monitoring of spinal cord function depends upon a quickly obtained, reproducible EP. The records must be obtained in a hostile environment where artifacts and other sources of electrical noise cannot easily be eliminated: records are obtained continuously without interrupting the surgery. We studied EP reproducibility by measuring cortical EP amplitude range and latency range within individual patients. Reproducibility was enhanced by several changes in the stimulus and recording parameters: (1) Bipolar recording near the vertex (Cz-Pz, E1-E2) eliminated a significant amount of the artifacts and random variations seen in referential recordings. Bipolar recordings sacrifice some amplitude but the improved reproducibility is worthwhile. (2) Restricted filters (especially 30-3000 Hz) improve reproducibility still further, compared to the traditional open filters (1-1000 Hz). (3) Fast stimulation rates improve monitoring up to rates of about 5 stimuli/sec. At even faster rates too much amplitude attenuation usually occurs. Using these techniques stable intraoperative EPs were recorded from all 115 patients except those in whom EPs were abnormal even before surgery. Advantages and disadvantages compared to epidural recording techniques were discussed. Several further observations were made, including (1) monitoring could be done equally as well with stimulation either at the peroneal or at the posterior tibial nerve; (2) balanced nitrous oxide and narcotic anesthesia did attenuate EPs by about 60%, although this is not so much as to interfere seriously with monitoring.

Adolescent↗
PubMed2004

Immediate and medium-term results of intraoperative parathyroid hormone monitoring during video-assisted parathyroidectomy.

HYPOTHESIS: Using an intraoperative parathyroid hormone (IOPTH) assay during video-assisted parathyroidectomy by lateral approach is useful in patients with sporadic primary hyperparathyroidism, and the medium-term results of surgery are excellent. DESIGN: Retrospective study of patients with sporadic primary hyperparathyroidism following video-assisted parathyroidectomy by lateral approach with IOPTH measurement. PATIENTS: Of 394 patients with sporadic primary hyperparathyroidism, 200 (67%) were eligible for video-assisted parathyroidectomy by lateral approach: patients in whom a single enlarged gland was clearly localized by ultrasonography, sestamibi scintigraphy, or both. MAIN OUTCOME MEASURES: An IOPTH assay was used in 198 patients. Intraoperative parathyroid hormone was measured at induction, skin incision, ablation, and 5 and 15 minutes after ablation. RESULTS: The immediate results of the IOPTH assay were true positive in 187 cases (94.4%), true negative in 8 cases (4%), false negative in 2 cases (1%), and false positive in 1 case (0.5%). The overall accuracy of the IOPTH assay was 98.5%. All patients were normocalcemic postoperatively. The median follow-up was 20.5 months in 150 reviewed: 149 patients (99.4%) were normocalcemic, 17 patients (11.3%) had an elevated PTH level with normocalcemia, and 1 patient (0.6%) had recurrent primary hyperparathyroidism. CONCLUSIONS: In our experience, IOPTH monitoring during video-assisted parathyroidectomy by lateral approach is useful in detecting multiple gland disease not suspected by preoperative localization studies. Overall, IOPTH monitoring predicts medium-term normocalcemia with a success rate of 98.5% in patients with sporadic primary hyperparathyroidism.

Adult↗
PubMed2003

Spinal dural arteriovenous fistulas: the use of intraoperative microvascular Doppler monitoring.

Spinal dural arteriovenous fistulas are characterized by an abnormal communication between the dural branch of the radiculomedullary artery and an intradural medullary vein. Although the optimal treatment strategy is still debated, a complete interruption of the flow in the fistulas should be obtained. The authors report four cases operated on with intraoperative microvascular Doppler monitoring assistance. In all cases, microDoppler confirmed the location of the fistula and revealed an arterial spectrum on the redundant dorsal medullary veins. After the clipping of the feeder of the arteriovenous shunt, the intraoperative monitoring documented a complete disappearance of the arterial spectrum and the reappearance of the venous pattern. The ultrasonographic changes suggested the complete interruption of the fistulas. Postoperative angiography showed no residual abnormality in all patients. Doppler monitoring during surgery confirms satisfactory interruption of the arterial feeder and may prove useful where initial identification of the feeding vessel is difficult.

Aged↗