[Show abstract][Hide abstract] ABSTRACT: A novel application of neurophysiological monitoring enabled us safely to anesthetize and position a child with severe lumbosacral spine flexion for diagnostic MRI and CT scan. We conducted a propofol-based anesthetic to optimize somatosensory (SSEP) and transcranial electric motor (tceMEP) evoked potential amplitudes, thereby facilitating dynamic neurological monitoring while fully extending the patient supine. In cases outside the operating room involving extraordinary changes in patient position, anesthesia providers may consider utilizing neurophysiological monitoring.
[Show abstract][Hide abstract] ABSTRACT: This study evaluated the ability of a novel intraoperative neurophysiologic monitoring method used to locate the axillary nerve, predict relative capsule thickness, and identify impending injury to the axillary nerve during arthroscopic thermal capsulorrhaphy of the shoulder.
Prospective cohort study.
Twenty consecutive patients with glenohumeral instability were monitored prospectively during arthroscopic shoulder surgery. Axillary nerve mapping and relative capsule thickness estimates were recorded before the stabilization portion of the procedure. During labral repair and/or thermal capsulorrhaphy, continuous and spontaneous electromyography recorded nerve activity. In addition, trans-spinal motor-evoked potentials of the fourth and fifth cervical roots and brachial plexus electrical stimulation, provided real-time information about nerve integrity.
Axillary nerve mapping and relative capsule thickness were recorded in all patients. Continuous axillary nerve monitoring was successfully performed in all patients. Eleven of the 20 patients underwent thermal capsulorrhaphy alone or in combination with arthroscopic labral repair. Nine patients underwent arthroscopic labral repair alone. In 4 of the 11 patients who underwent thermal capsulorrhaphy, excessive spontaneous neurotonic electromyographic activity was noted, thereby altering the pattern of heat application by the surgeon. In 1 of these 4 patients, a small increase in the motor latency was noted after the procedure but no clinical deficit was observed. There were no neuromonitoring or clinical neurologic changes observed in the labral repair group without thermal application. At last follow-up, no patient in either group had any clinical evidence of nerve injury or complications from neurophysiologic monitoring.
We successfully evaluated the use of intraoperative nerve monitoring to identify axillary nerve position, capsule thickness, and provide real-time identification of impending nerve injury and function during shoulder thermal capsulorrhaphy. The use of intraoperative nerve monitoring altered the heat application technique in 4 of 11 patients and may have prevented nerve injury.
Level II, prospective cohort study.
Arthroscopy The Journal of Arthroscopic and Related Surgery 07/2005; 21(6):665-71. · 3.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Clinically relevant aspects of pedicle screws were subjected to electrical resistance testing.
To catalog commonly used pedicle screws in terms of electrical resistance, and to determine whether polyaxial-type pedicle screws have the potential to create a high-resistance circuit during stimulus-evoked electromyographic testing.
Although stimulus-evoked electromyography is commonly used to confirm the accuracy of pedicle screw placement, no studies have documented the electrical resistance of commonly used pedicle screws.
Resistance measurements were obtained from eight pedicle screw varieties (5 screws of each type) across the screw shank and between the shank and regions of the screw that would be clinically accessible to stimulus-evoked electromyographic testing with a screw implanted in a pedicle. To determine measurement variability, resistance was measured three times at each site and with the crown of the polyaxial-type screw in three random positions.
Resistance across the screw shank ranged from 0 to 36.4 ohms, whereas resistance across the length of the monoaxial-type screws ranged from 0.1 to 31.8 ohms. Resistance between the hexagonal port and shank of polyaxial-type screws ranged from 0 to 25 ohms. In contrast, resistance between the mobile crown and shank of polyaxial-type screws varied widely, ranging from 0.1 ohms to an open circuit (no electrical conduction). Polyaxial-type screws demonstrated an open circuit in 28 of 75 measurements (37%) and a high-resistance circuit (exceeding 1000 ohms) in 5 of 75 measurements (7%).
Polyaxial-type pedicle screws have the potential for high electrical resistance between the mobile crown and shank, and therefore may fail to demonstrate an electromyographic response during stimulus-evoked electromyographic testing in the setting of a pedicle breech. To avoid false-negative stimulus-evoked electromyographic testing, the cathode stimulator probe should be applied to the hexagonal port or directly to the screw shank, and not to the mobile crown.
[Show abstract][Hide abstract] ABSTRACT: Retrospective review of 61 consecutive patients.
To determine the effectiveness of combining intraoperative monitoring of both spontaneous electromyographic activity and compound muscle action potential response to stimulation for detecting a perforation of the pedicle cortex irritation of nerve root during lumbar spine fusion surgery.
The complication rate from instrumentation used with lumbar spine fusion varies from 1 to 33%. To prevent neurologic complications, several monitoring techniques have been used to alert surgeons to possible neurologic damage being introduced during nerve decompression or placement of instrumentation with spine procedures. Because of different sensitivities, one monitoring technique may not be as effective for preventing complications as a combination of techniques.
Sixty-one consecutive patients who underwent instrumented posterior lumbar fusions received continuous electromyographic monitoring and stimulus-evoked electromyographic monitoring. A significant neurophysiologic event was signaled by sustained neurotonic electromyographic activity, prompting an alert and a pause in the surgical manipulations that precipitated the activity. After insertion of the transpedicular screws, the integrity of the pedicle cortex was tested by stimulating each screw head and recording compound muscle action potentials. In the presence of a pedicle breach, stimulus intensities below 7 mA were sufficient to evoke compound muscle action potentials from the muscle group innervated by the adjacent spinal nerve root, prompting a surgical alert and subsequent repositioning of the screw.
Fourteen significant neurophysiologic events occurred in 13 of 61 patients (21%). Sustained neurotonic electromyographic discharges occurred in 5 of 40 patients during placement of interbody fusion cages, in 2 patients during placement of transpedicular screws, and in 1 patient during tightening of rods. On pedicle screw stimulation, breaches of the pedicle cortex were detected in 6 patients. After surgery, no new neurologic deficits were found in 60 of the 61 patients. One patient who experienced temporary paraparesis had sustained neurotonic electromyographic discharges during retraction of the thecal sac and distraction of the disc space before placement of the cage.
These results suggest that intraoperative electromyographic monitoring provides a real-time measure of impending spinal nerve root injury during instrumented posterior lumbar fusion, allowing for timely intervention and minimization of negative postoperative sequela.
[Show abstract][Hide abstract] ABSTRACT: Purpose of study: There is ongoing controversy as to the risk of paraplegia from segmental artery ligation during anterior spinal fusion. While somatosensory evoked potentials have been used to test indirectly for spinal cord ischemia after temporary segmental artery occlusion, the potential for a false-negative finding is high, because the SSEP is dorsal column mediated. The purpose of this study was to determine if transcranial electrical motor-evoked potentials (TCEMEPs) could provide a more sensitive, direct test for identifying nutrient-feeding segmental arteries that are critical to anterior spinal motor tract function before vessel ligation.Methods used: TCEMEPs (Digitimer, Ltd., Garden City, UK) were recorded from bilateral quadriceps, tibialis anterior and/or abductor hallucis muscles as well as from an upper extremity control muscle group, both before and 2 to 3 minutes after test occlusion of each candidate segmental artery. If postocclusion TCEMEP amplitudes did not change, the vessel was permanently ligated. If, however, response amplitude over one or more lower extremity muscles was diminished by more than 50%, the clamp was released until complete amplitude recovery. If on subsequent reclamping, TCEMEP amplitudes again diminished (more than 50%), no permanent ligation was performed.of findings: Significant TCEMEP changes after temporary vessel occlusion were noted in 8 (6.0%) of 150 pediatric patients in this series. In two patients, the TCEMEP changes were correlated with hypotension (MAP< 55 mm Hg), which resolved upon elevating the MAP to 90 mm Hg, thereby allowing for permanent vessel ligation. For the remaining six patients (4.0%), however, TCEMEPs could be restored only by removal of the test clamp. Consequently, no permanent ligation was performed to avoid postoperative motor deficit. No patient emerged with new motor deficit after surgery, as predicted by unchanged TCEMEPs at closing.Relationship between findings and existing knowledge: TCEMEPs provide a rapid, valid and reliably sensitive technique for identifying segmental arteries that may be nutrient feeders to the anterior spinal cord. If ligated, such segmental vessels may predispose the patient to anterior spinal cord ischemic injury, particularly during a single-stage anterior-posterior spinal fusion for scoliosis correction.Overall significance of findings: These data suggest that, in select patients, there are segmental arteries that represent critical feeding vessels to the anterior spinal artery for maintenance of adequate spinal cord perfusion during the application of strong corrective spinal forces.Disclosures: Device or drug: Digitimer D-185 Multi-Pulse Motor Evoked Potential Stimulator. Status: investigational.Conflict of interest: No conflicts.