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Daniel M Schwartz

Publications and source records attributed to Daniel M Schwartz.

At least 19 recordsLinked to original sources
PubMed2006

Neurophysiological identification of position-induced neurologic injury during anterior cervical spine surgery.

This study was a retrospective review of 3,806 patients who underwent anterior cervical spine surgery with multi-modality neurophysiological monitoring consisting of transcranial electric motor evoked potentials, somatosensory evoked potentials and spontaneous electromyography between 1999-2003. The objectives of this study were twofold: (1) to evaluate the role of transcranial electric motor evoked potential tceMEP and ulnar nerve somatosensory evoked potential (SSEP) monitoring for identifying impending position-related stretch brachial plexopathy, peripheral nerve entrapment/compression or spinal cord compression and (2) to estimate the point-prevalence of impending neurologic injury secondary to surgical positioning effects. Sixty-nine of 3,806 patients (1.8% showed intraoperative evidence of impending neurologic injury secondary to positioning, prompting interventional repositioning of the patient. The brachial plexus was the site of evolving injury in 65% of these 69 cases. Impending brachial plexopathy was most commonly noted immediately following shoulder taping and the application of counter-traction. Brachial plexus stretch upon neck extension for optimal surgical access and visualization was second in frequency-of-occurrence. Evolving traction injury to the ulnar nerve attributed to tightly-wrapped or malpositioned arms was observed in 16% of alerted cases, whereas evolving spinal cord injury following neck extension accounted for an additional 19%. This study highlights the role of tceMEP and ulnar nerve SSEP monitoring for detecting emerging peripheral nerve injury secondary to positioning in preparation for and during anterior cervical spine surgery.

Adult↗
PubMed2006

Characterization of neurophysiologic alerts during anterior cervical spine surgery.

STUDY DESIGN: A retrospective review of neurophysiologic alerts during anterior cervical surgery. OBJECTIVES: To examine incidence and types of neurophysiologic alerts and their correlation with new postoperative neurologic deficits after anterior cervical discectomy or corpectomy procedures. SUMMARY OF BACKGROUND DATA: Although multimodality neurophysiologic monitoring has been shown to predict iatrogenic neurologic injuries in scoliosis surgeries, their role in degenerative or trauma-related anterior cervical spine surgery is still unclear. MATERIALS AND METHODS: We retrospectively reviewed 1,445 patients who underwent anterior cervical discectomy or corpectomy and arthrodesis with neurophysiologic monitoring that included transcranial electrical motor-evoked potentials (tceMEP), somatosensory-evoked potentials (SSEP), and spontaneous electromyography (EMG). Intraoperative alerts were analyzed for type, perceived cause, actions taken to reverse or minimize the possible spinal cord injury, and any new postoperative neurologic deficits. RESULTS: There were 267 (18.4%) procedures that had either minor (spontaneous, sustained EMG) or major (tceMEP/SSEP amplitude reduction) alerts. Patients who underwent corpectomies had 28% increased risk of having a major neurophysiologic alert compared with those who had discectomies. Diagnosis of cervical spondylotic myelopathy or trauma increased the risk of having a major neurophysiologic alert 30% and 76%, respectively, compared with cervical radiculopathy. Eight surgeries were aborted due to persistent tceMEP/SSEP amplitude loss, but none resulted in new postoperative neurologic deficits. Two patients had halo-vest applied due to early termination of surgery. One of these patients ultimately could not receive definitive surgical stabilization. DISCUSSION AND CONCLUSION: Diagnosis of cervical spondylotic myelopathy or trauma and cervical corpectomy procedures increase the risk for having major intraoperative alerts. In case of persistent tceMEP/SSEP amplitude loss, consider delaying potentially harmful interventions, such as premature termination of the procedure or methylprednisolone infusion, until a new neurologic deficit is verified with an awake-clinical examination.

Adult↗
PubMed2006

Neurophysiological monitoring under anesthesia to position a child with extreme lumbar spine flexion for MRI and CT scan.

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.

Adolescent↗
PubMed2005

Axillary nerve monitoring during arthroscopic shoulder stabilization.

PURPOSE: 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. TYPE OF STUDY: Prospective cohort study. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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 OF EVIDENCE: Level II, prospective cohort study.

Adolescent↗
PubMed2005

Anesthetic management for pediatric spinal fusion: implications of advances in spinal cord monitoring.

Currently, the detection of emerging injury through intraoperative neurologic monitoring is the best way to prevent neurologic injury. This requires a team approach that includes the anesthesiologist, neurophysiologist, and surgeon. The monitoring modalities available for the patient must be considered in planning the anesthetic management. In addition, intraoperative care for the patient requires an ongoing attention to how the anesthetic drugs affect spinal cord monitoring.

Anesthesia↗
PubMed2004

Statin and aspirin therapy are associated with decreased rates of choroidal neovascularization among patients with age-related macular degeneration.

PURPOSE: To investigate the relationship between statin and aspirin use and the risk of choroidal neovascularization (CNV) in patients with age-related macular degeneration (AMD). DESIGN: Retrospective consecutive case series. METHODS: All patients 60 years and older with AMD who were seen between January 1, 1990, and March 1, 2003, at the San Francisco Veterans Affairs Hospital Eye Clinic with fundus photographs were included. Patients with other diagnoses predisposing to CNV or incomplete medical records were excluded. The main outcome measure was angiographically evident CNV. Diagnosis was based on review of fundus photographs and fluorescein angiograms in masked fashion; medical records were reviewed for variables possibly predisposing to CNV or statin use. For patients with CNV, age of onset was recorded; those without CNV were treated as censored. Age-related macular degeneration disease status and time of onset of CNV was compared between patients treated or not treated with statins for at least 6 months. RESULTS: Of 326 patients with AMD, 104 had CNV, 204 had dry AMD, and 18 had geographic atrophy (GA). Of CNV subjects, 21 (20%) used statins, compared with 77 (38%) of dry AMD subjects without GA and 6 (33%) of controls with GA (hazard ratio = 0.51, 95% confidence interval (CI) = 0.31-0.86, P =.01). Aspirin use was also significantly associated with decreased rates of CNV; 62 CNV subjects (60%) used aspirin, compared with 154 (75%) dry AMD subjects without GA or 12 (67%) with GA (hazard ratio = 0.63, 95% CI = 0.40-0.98, P =.04). CONCLUSIONS: Therapy with statins or aspirin is associated with decreased rates of CNV among AMD patients. Additional study with a prospective and/or randomized trial of statin and aspirin use in AMD patients is warranted.

Age of Onset↗
PubMed2004

Complications of hydrogel explants used in scleral buckling surgery.

PURPOSE: To report a group of patients with symptoms of pain, strabismus, sensation of orbital fullness, and presence of a subconjunctival mass many years after successful scleral buckling surgery using hydrogel explants. DESIGN: We present an interventional consecutive case series of patients who underwent scleral buckling surgery using hydrogel explants from 4 to 14 years before onset of clinical symptoms. SETTING: This is a retrospective, multicenter clinical study. PATIENT POPULATION: 17 eyes of 15 patients presented with this disorder. All patients were examined; Snellen acuity, ocular motility, tonometry, slit lamp, and fundus examination were recorded. Two patients underwent either computed tomography or magnetic resonance imaging. Removal of the hydrogel explant was attempted in all patients. Removal of the buckle was technically difficult; the hydrogel material was fragile and fragmented when handled. RESULTS: All patients had prompt relief of pain and discomfort. Ocular motility and diplopia were greatly improved. Extraocular muscle surgery was not required in any case. Three eyes had intraoperative eye wall perforation. One eye developed postoperative bacterial endophthalmitis. Five eyes had recurrence of retinal detachment. One eye had additional complications of corneal edema and glaucoma. CONCLUSIONS: Patients who develop this clinical condition should be considered for removal of the hydrogel scleral buckle. Early recognition of this condition may prevent serious complications associated with delayed removal.

Adolescent↗
PubMed2004

Facilitated assessment of unconsciousness from morphologic changes in the bilateral posterior tibial nerve cortical somatosensory evoked potential under total intravenous propofol anesthesia during spine surgery.

OBJECTIVE: To describe a unique morphologic feature of the bilateral posterior tibial nerve cortical somatosensory evoked potential, the S-wave, which varies systematically with propofol infusion rate and which appears to be useful in guiding adequate propofol concentration levels during spine surgery. METHODS: Two illustrative cases were selected from a pool of 15,000 pediatric and adult patients (ages 8-85 years) who were undergoing corrective spine surgery in operating rooms of university and community hospitals. Anesthesia was maintained with a continuous intravenous infusion of propofol (125-225 microg/kg/min) along with intermittent boluses of narcotic and midazolam (1.0-2.0 mg) as needed. Characteristic metamorphosis of the bilateral posterior tibial nerve cortical somatosensory evoked potential, highlighted by the emergence of an additional middle-latency component labeled the S-wave, served as a neurophysiological marker of "light" propofol anesthesia prompting elevation of propofol infusion rate or bolus injection. RESULTS: The S-wave was routinely abolished with increased propofol infusion rate or bolus injection. In all instances increased propofol concentration levels produced a characteristic morphologic change in the posterior tibial nerve cortical somatosensory evoked potential consistent with a return to adequate anesthetic depth. Selected cases presented herein compare the S-wave technique to BIS and illustrate the usefulness of the S-wave in identifying inadequate depth of propofol anesthesia. CONCLUSIONS: The bilateral posterior tibial nerve cortical somatosensory evoked potential changes its morphology in predictable fashion with decreased depth of propofol anesthesia, allowing for anticipation of imminent anesthetic "lightening." It serves as a useful cross-check to Bispectral Index (BIS) or other "level of consciousness" EEG-based algorithms for monitoring depth of propofol anesthesia during prolonged corrective spine surgery.

Adult↗
PubMed2004

Comparison of transcranial electric motor and somatosensory evoked potential monitoring during cervical spine surgery.

BACKGROUND: There has been little enthusiasm for somatosensory evoked potential monitoring in cervical spine surgery as a result, in part, of the increased risk of motor tract injury at this level, to which somatosensory monitoring may be insensitive. Transcranial electric motor evoked potential monitoring allows assessment of the motor tracts; therefore, we compared transcranial electric motor evoked potential and somatosensory evoked potential monitoring during cervical spine surgery to determine the temporal relationship between the changes in the potentials demonstrated by each type of monitoring and neurological sequelae and to identify patient-related and surgical factors associated with intraoperative neurophysiological changes. METHODS: Somatosensory evoked potential and transcranial electric motor evoked potential data recorded for 427 patients undergoing anterior or posterior cervical spine surgery between January 1999 and March 2001 were analyzed. All patients who showed substantial (at least 60%) or complete unilateral or bilateral amplitude loss, for at least ten minutes, during the transcranial electric motor evoked potential and/or somatosensory evoked potential monitoring were identified. RESULTS: Twelve of the 427 patients demonstrated substantial or complete loss of amplitude of the transcranial electric motor evoked potentials. Ten of those patients had complete reversal of the loss following prompt intraoperative intervention, whereas two awoke with a new motor deficit. Somatosensory evoked potential monitoring failed to identify any change in one of the two patients, and the change in the somatosensory evoked potentials lagged behind the change in the transcranial electric motor evoked potentials by thirty-three minutes in the other. No patient showed loss of amplitude of the somatosensory evoked potentials in the absence of changes in the transcranial electric motor evoked potentials. Transcranial electric motor evoked potential monitoring was 100% sensitive and 100% specific, whereas somatosensory evoked potential monitoring was only 25% sensitive; it was, however, 100% specific. CONCLUSIONS: Transcranial electric motor evoked potential monitoring appears to be superior to conventional somatosensory evoked potential monitoring for identifying evolving motor tract injury during cervical spine surgery. Surgeons should strongly consider using this modality when operating on patients with cervical spondylotic myelopathy in general and on those with ossification of the posterior longitudinal ligament in particular.

Cervical Vertebrae↗
PubMed2004

Light-adjustable lens: development of in vitro nomograms.

PURPOSE: To determine whether digital spatial intensity patterns can be developed to effect precise in vitro correction of myopic, hyperopic, and astigmatic refractive errors in a silicone light-adjustable lens (LAL). Also, to determine whether a new spatial intensity pattern for "lock-in" is effective in vitro. METHODS: A digital interferometer/irradiation system was developed to irradiate LALs and measure the power change following irradiation. Light-adjustable lenses were mounted into a wet cell maintained at 35.0 +/- 0.5 degrees C (simulated ocular temperature) and allowed to equilibrate for a minimum of 2 hours. Ultraviolet light was then applied with spatial light intensity patterns to correct hyperopia, myopia, and astigmatism. Light-adjustable lenses were also treated to effect lock-in with a separate spatial light intensity pattern. Treated lenses were characterized for power change and optical quality. In the case of lock-in, exhaustive chemical extraction was also performed to determine the percentage of remaining macromer. RESULTS: Appropriate digital irradiation spatial intensity patterns were created to develop nomograms for in vitro correction of myopia, hyperopia, and astigmatism in approximate 0.25 D steps. Power changes were reproducible and did not alter optical quality of the LALs. Further, lock-in dosing of the LALs did not alter optical quality or significantly change LAL power. CONCLUSIONS: In vitro nomograms have been developed for a silicone LAL that permit precise correction of myopia, hyperopia, and astigmatism. Furthermore, a spatial light intensity pattern has been devised that effects lock-in without significantly altering LAL power or optical quality.

Astigmatism↗
PubMed2003

Regulated expression of apolipoprotein E by human retinal pigment epithelial cells.

In early age-related macular degeneration (AMD), lipid-containing deposits (drusen) accumulate in Bruch's membrane underlying the retinal pigment epithelium (RPE). Recent studies indicate that apolipoprotein E (apoE) may play a role in lipid trafficking in AMD. Compared with the apoE3 allele, the apoE4 and apoE2 alleles are associated with decreased and increased risk for AMD, respectively; drusen contain high levels of apoE, and apoE null mice develop lipid deposits in Bruch's membrane similar to those observed in AMD. Primary cultures of human RPE cells expressing the apoE3 allele were grown on Transwell culture plates. Western blotting, ELISA assay, and mass spectrometry confirmed that apoE3 was secreted into the apical and basal chambers and that secretion was upregulated by thyroid hormone, 9-cis-retinoic acid, and 22(R)-hydroxycholesterol. In addition, basally secreted apoE associated with exogenously added HDL. These results indicate that apoE secretion can be regulated by specific hormones and that apoE associates with HDL. The findings are consistent with a role for apoE in lipid trafficking through Bruch's membrane and may be relevant to AMD.

Adult↗
PubMed2003

Light-adjustable lens.

PURPOSE: First, to determine whether a silicone light-adjustable intraocular lens (IOL) can be fabricated and adjusted precisely with a light delivery device (LDD). Second, to determine the biocompatibility of an adjustable IOL and whether the lens can be adjusted precisely in vivo. METHODS: After fabrication of a light-adjustable silicone formulation, IOLs were made and tested in vitro for cytotoxicity, leaching, precision of adjustment, optical quality after adjustment, and mechanical properties. Light-adjustable IOLs were then tested in vivo for biocompatibility and precision of adjustment in a rabbit model. In collaboration with Zeiss-Meditec, a digital LDD was developed and tested to correct for higher-order aberrations in light-adjustable IOLs. RESULTS: The results establish that a biocompatible silicone IOL can be fabricated and adjusted using safe levels of light. There was no evidence of cytotoxicity or leaching. Testing of mechanical properties revealed no significant differences from commercial controls. Implantation of light-adjustable lenses in rabbits demonstrated- excellent biocompatibility after 6 months, comparable to a commercially available IOL. In vivo spherical (hyperopic and myopic) adjustment in rabbits was achieved using an analog light delivery system. The digital light delivery system was tested and achieved correction of higher-order aberrations. CONCLUSION: A silicone light-adjustable IOL and LDD have been developed to enable postoperative, noninvasive adjustment of lens power. The ability to correct higher-order aberrations in these materials has broad potential applicability for optimization of vision in patients undergoing cataract and refractive surgery.

Animals↗
PubMed2002

Intraoperative neurophysiologic detection of iatrogenic C5 nerve root injury during laminectomy for cervical compression myelopathy.

STUDY DESIGN: A retrospective and prospective study was conducted to investigate intraoperative neurophysiologic monitoring during cervical laminectomy to detect iatrogenic C5 nerve root palsy. OBJECTIVE: To evaluate the usefulness of various intraoperative neuromonitoring methods for identifying C5 nerve root palsy. SUMMARY OF BACKGROUND DATA: One unsolved complication after laminectomy or laminoplasty for cervical compression myelopathy is C5 nerve root palsy. It can go undetected even in the presence of intraoperative neuromonitoring with conventional upper extremity mixed nerve or dermatomal somatosensory-evoked potentials or transcranial motor-evoked potentials, recording typically from hand muscles. METHODS: The intraoperative neuromonitoring data of 200 patients who underwent cervical laminectomy for myelopathy between 1998 and 2000 were reviewed for C5 nerve root palsy. Retrospective studies were conducted for the first 132 patients, who were monitored with conventional techniques including ulnar and posterior tibial nerve somatosensory-evoked potentials, C5-C7 dermatomally evoked potentials, and transcranial electrical motor-evoked potentials recorded from hand and leg muscles. Prospective studies then were applied to the remaining 68 patients, for whom transcranial electrical motor-evoked potentials and spontaneous electromyography were monitored from deltoid and biceps muscles in the wake of undetected C5 nerve root palsy from conventional neurophysiologic monitoring methods. RESULTS: In the retrospective cohort, six patients presented after surgery with C5 nerve root palsy showing unilateral deltoid muscle paralysis despite entirely unremarkable conventional somatosensory-evoked potentials, dermatomally evoked potentials, and transcranial electrical motor-evoked potentials from hand and leg muscles. For the prospective cohort, two patients experienced postoperative iatrogenic C5 motor nerve root palsy. Impending C5 nerve root injuries after laminectomy were successfully identified in both patients showing significant changes in deltoid and biceps transcranial electrical motor-evoked potentials and spontaneous electromyography, thereby averting more serious consequence. There were no false-negative and false-positive results. CONCLUSIONS: In an effort to reduce postoperative C5 nerve root palsy, the clinician should consider intraoperative deltoid and biceps transcranial electrical motor-evoked potential and spontaneous electromyography monitoring whenever there is potential for iatrogenic C5 nerve root injury.

Adult↗
PubMed2002

Pedicle screws with high electrical resistance: a potential source of error with stimulus-evoked EMG.

STUDY DESIGN: Clinically relevant aspects of pedicle screws were subjected to electrical resistance testing. OBJECTIVES: 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. SUMMARY OF BACKGROUND DATA: 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. METHODS: 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. RESULTS: 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%). CONCLUSIONS: 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.

Alloys↗
PubMed2002

Human retinal pigment epithelial cells express scavenger receptors BI and BII.

The retinal pigment epithelial (RPE) cells that underlie the retina ingest and metabolize thousands of lipid-rich photoreceptor outer segments (POS) every day. The scavenger receptor (SR) CD36 and integrin alphavbeta5 have been shown to participate in POS binding and internalization by RPE cells. The objective of the current study was to determine whether RPE cells express SRs other than CD36. Primary cultures of human RPE cells express both mRNA and protein for SR-BI and SR- BII. SR-BI and SR-BII mRNAs were detected by reverse transcription-polymerase chain reaction. SR-BI protein was detected by immune precipitation of [(35)S]methionine-labeled crude cellular extracts. SR-BII was detected by Western blotting of immune precipitated crude cellular extracts. SR-BI and SR-BII proteins were also detected by immunofluorescence staining of RPE cells in culture. The results suggest that these SRs may play a role in POS lipid binding and uptake by RPE cells in the eye.

Blotting, Western↗
PubMed2002

Corneal toxicity of intraocular hyaluronidase.

The purpose of this study was to examine the corneal toxicity of different preparations of intraocular hyaluronidase. SDS-PAGE analysis of bovine testicular hyaluronidase (Wydase) and chromatographically purified hyaluronidase (Sigma) was performed. These two preparations were injected into the anterior chamber of rabbits in amounts ranging from 1.5-150 IU (Wydase) and 1.5-300 IU (Sigma). A third set of rabbit eyes received Wydase vehicle alone or in combination with Sigma hyaluronidase. Treated control eyes were injected with saline. Slit lamp examination and indirect ophthalmoscopy were performed preoperatively and on postoperative days 1 and 7. Light microscopy of the corneas was performed. SDS-PAGE of Wydase revealed numerous protein impurities, while Sigma demonstrated one protein band consistent with mammalian hyaluronidase. Persistent corneal edema, severe anterior chamber fibrin, and endothelial necrosis, were seen in the majority of eyes injected with Wydase in amounts of 50 IU and greater (n = 11). Thirty percent (30%) of the eyes injected with the Sigma preparation (n = 11) had localized corneal opacity similar to 50% of eyes injected with saline (n = 2). Of the rabbit eyes injected with the Wydase vehicle (n = 19), 68% had toxic changes. Intracameral injection of Wydase is toxic to the rabbit cornea in amounts of 50 IU and greater. A chromatographically purified preparation showed only transient local toxicity. Toxicity of Wydase may be due to protein impurities and the thimerosal-containing vehicle.

Animals↗
PubMedDate not supplied

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↗