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Papers by Daniel Schwartz

Research paper thumbnail of 25. Neurophysiological detection of iatrogenic C5 nerve root injury during anterior cervical laminectomy and laminoplasty

The Spine Journal, 2004

poor treatment outcomes. High pain intensity is indicative of more than just self-reported pain. ... more poor treatment outcomes. High pain intensity is indicative of more than just self-reported pain. When individuals report extreme levels of pain intensity after extensive PRE-rehab treatment and disability averaging 16 months, they are likely also to display major barriers to recovery and higher levels of depression, physical inhibition, and perceived dysfunction. The 13% of patients still complaining of extreme pain intensity after rehabilitation have particularly poor outcomes, and are at risk for substantially higher health utilization costs and lower work productivity over the one year posttreatment. Early recognition may lead to strategies to decrease this risk. DISCLOSURES: No disclosures. CONFLICT OF INTEREST: No Conflicts.

Research paper thumbnail of 58. The Role of TceMEPs in Detection of Iatrogenic Spinal Nerve Root Deficit during Instrumented Lumbosacral Fusion

Research paper thumbnail of Intraoperative Monitoring of the Processed Electroencephalogram

Seminars in Hearing, 1988

Research paper thumbnail of P51. Are dermatomal somatosensory evoked potentials useful for assessing adequacy of cervical nerve root decompression?

The Spine Journal, 2003

reports on a high percentage of their original patients. This paper reviews the results in those ... more reports on a high percentage of their original patients. This paper reviews the results in those patients. RESULTS: Thirty-three of 43 eligible patients (77%) were evaluated including 30 patients who reported for examination and X-ray and 3 additional patients located by telephone survey. Before fusion surgery the average patient had two prior decompression surgeries and a history of back pain for 14.9 years and leg pain for 8.4 years. Average age at surgery was 50.4 years. Smokers included 15 patients with an average of 23.9 pack years of smoking. Average post-surgical follow-up was 115.5 months. Clinical success, defined by a modified Prolo score, included patients whose status was excellent, good, or fair with a minimum of three-points of improvement. Clinical success was achieved in 32/37 (86.5%) at 24 months and in 29/ 33 (87.8%) at ten years. This included 61% excellent, 27% good, and 12% fair results. Fusion success was reported in 37/37 (100%) of patients at 24 months and in 29/30 (96.7%) at ten years. One fusion failure was identified in a patient who was judged fused at 24 months. Patient satisfaction was reported in 31/33 (93.9%). Further lumbar surgery was done in 23 patients: in 18 patients for elective removal of pedicle screws and in 5 patients to extend the fusion to adjacent levels. Sagittal plane alignment was not measured in the original study. At ten-years, the L4-S1 lordosis averaged 23.3 degrees. Adjacent segment degeneration occurred in 60% of patients but was clinically significant in only 20%. Smokers had equal clinical and fusion success with non-smokers at 24 months and 10 years and had adjacent segment degeneration in 26.7%, a rate significantly lower than non-smokers at 66.7%. DISCUSSION: Since the original study, improved surgical techniques have allowed improvement in sagittal plane alignment with these implants. Additionally, tapered or wedged-shaped implants have facilitated achievement of normal lordosis. It is likely but unproven that the incidence of adjacent segment degeneration was related to the loss of 10 to 15 degrees of lordosis. The lower rate of adjacent degeneration in smokers is counterintuitive. The study protocol recommended removal of pedicle screws after bony fusion. Routine removal of pedicle screws is not currently recommended. CONCLUSIONS: The high rate of clinical success, fusion success, and patient satisfaction at 24 months was maintained at ten-year follow-up.

Research paper thumbnail of Efficacy of Spinal Cord Monitoring in Scoliosis Surgery in Patients with Cerebral Palsy

Journal of Spinal Disorders, 1996

Although spinal cord monitoring is recommended during scoliosis surgery, a review from Rancho Los... more Although spinal cord monitoring is recommended during scoliosis surgery, a review from Rancho Los Amigos Medical Center stated that they were only able to obtain reproducible tracings in 53% of cerebral palsy patients. To ascertain that monitoring is both feasible and reliable in these patients, we reviewed the records of 34 consecutive patients with cerebral palsy who had scoliosis surgery at our institution. Spinal cord function was monitored by recording peripheral nerve, cervical/brainstem, and cortical somatosensory evoked potentials to posterior tibial nerve stimulation. Reproducible tracings were achieved in 31 of the 34 patients. Significant intraoperative changes were recorded in 12 of the 31 monitored patients, usually related to and requiring some modifications of the instrumentation. We conclude that with careful technique, spinal cord monitoring using cervical/brainstem somatosensory evoked potentials can be reliably achieved in most patients with cerebral palsy undergoing scoliosis surgery.

Research paper thumbnail of Prevention of Positional Brachial Plexopathy During Surgical Correction of Scoliosis

Journal of Spinal Disorders, 2000

Continuous intraoperative monitoring of spinal cord function using somatosensory evoked potential... more Continuous intraoperative monitoring of spinal cord function using somatosensory evoked potentials (SSEP) has gained nearly universal acceptance as a reliable and sensitive method for detecting and possibly preventing neurologic injury during surgical correction of spinal deformities. In several reports, spinal cord injury was identified successfully based on changes in SSEP response characteristics, specifically amplitude and latency. Less well documented and used, however, is monitoring of peripheral nerve function with SSEPs to identify and prevent the neurologic sequelae of prolonged prone positioning on a spinal frame. The authors describe a patient who underwent surgical removal of spinal instrumentation but was not monitored. A brachial plexopathy developed in this patient from pressure on the axilla exerted by a Relton-Hall positioning frame during spinal surgery. In addition, data are presented from 15 of 500 consecutive pediatric patients who underwent surgical correction of scoliosis between 1993 and 1997 with whom intermittent monitoring of ulnar nerve SSEPs was used successfully to identify impending brachial plexopathy, a complication of prone positioning. A statistically significant reduction in ulnar nerve SSEP amplitude was observed in 18 limbs of the 500 patients (3.6%) reviewed. Repositioning the arm(s) or shoulders resulted in nearly immediate improvement of SSEP amplitude, and all awoke without signs of brachial plexopathy. This complication can be avoided by monitoring SSEPs to ulnar nerve stimulation for patients placed in the prone position during spinal surgery.

Research paper thumbnail of Influence of Rigid Spinal Instrumentation on the Neurogenic Motor Evoked Potential

Journal of Spinal Disorders, 1996

Three case reports are presented to illustrate how placement of spinal instrumentation obliterate... more Three case reports are presented to illustrate how placement of spinal instrumentation obliterates previously normal neurogenic motor evoked potentials (NMEPs) elicited by transosseous electrical stimulation. This results in an unacceptably high false-positive rate for NMEP recordings during scoliosis surgery. The loss of the NMEPs was attributed to shunting of electrical current from JO5 spinous process stimulating needles through the metal rod to ground, thus preventing adequate stimulation to the spinal cord. A modification of the transosseous technique with epidural stimulation to improve test reliability is described.

Research paper thumbnail of Influence of Nitrous Oxide on Posterior Tibial Nerve Cortical Somatosensory Evoked Potentials

Journal of Spinal Disorders, 1997

The suppressive effect of the halogenated inhalation anesthesia on cortical somatosensory evoked ... more The suppressive effect of the halogenated inhalation anesthesia on cortical somatosensory evoked potentials (cSSEPs) has been well documented. Less studied and appreciated is the effect of nitrous oxide often with a narcotic as an alternative to a potent agent for spinal cord monitoring. This study sought to define more clearly the influence of nitrous oxide on cSSEPs elicited to posterior tibial nerve stimulation. A secondary purpose was to demonstrate the advantage of a total intravenous propofol anesthesia in facilitating uncompromised large-amplitude cSSEPs. Fifty adult patients undergoing anterior cervical discectomy served as the study sample. Brainstem and cortical posterior tibial nerve SSEPs were recorded under two independent anesthesia conditions, namely, nitrous oxide and propofol. Results demonstrated a significant amplitude reduction and latency prolongation with the nitrous oxide versus propofol protocol. cSSEP amplitude with propofol was, on the average, approximately two times larger than that with nitrous oxide. Based on these findings, the use of nitrous-oxide anesthesia is not recommended when limited to monitoring cSSEPs that are already amplitude compromised secondary to existing spinal cord disease.

Research paper thumbnail of Comparison of transcranial electric motor and somatosensory evoked potential monitoring during cervical spine surgery

The Journal of bone and joint surgery. American volume, 2004

There has been little enthusiasm for somatosensory evoked potential monitoring in cervical spine ... more 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. 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...

Research paper thumbnail of The Retrolabyrinthine Transsigmoid Approach to Midbasilar Artery Aneurysms

The Laryngoscope, 1992

One of the more challenging problems in surgery of the petroclival area are aneurysms of the midb... more One of the more challenging problems in surgery of the petroclival area are aneurysms of the midbasilar trunk and vertebrobasilar artery junction. Aneurysms in this area are difficult to access. Most approaches result in a deep and narrow surgical field which includes ...

Research paper thumbnail of Results of closed management of acute dislocation after reverse shoulder arthroplasty

Journal of Shoulder and Elbow Surgery, 2014

Postoperative instability continues to be one of the most common complications limiting outcomes ... more Postoperative instability continues to be one of the most common complications limiting outcomes of reverse shoulder arthroplasty (RSA). The optimal management of this complication remains unknown. The purpose of this study was to evaluate the outcomes of patients with postoperative dislocation after RSA managed with closed reduction. All patients who were treated with a closed reduction for dislocation after RSA in the period between May 2002 and September 2011 were identified and retrospectively reviewed. Final outcomes including recurrent instability, need for revision surgery, American Shoulder and Elbow Surgeons outcome score, and range of motion were evaluated. A total of 21 patients were identified. Nearly 50% of cases (10 of 21) had previous surgery, with 80% (8 of 10) of these being previous arthroplasty. The average time to first dislocation was 200 days, with 62% (13 of 21) occurring in the first 90 days. At average follow-up of 28 months, 62% of these shoulders remained stable (13 of 21), 29% required revision surgery (6 of 21), and 9% remained unstable (2 of 21). The average American Shoulder and Elbow Surgeons score was 68.0 for patients treated with closed reduction for instability and 62.7 for those treated with revision surgery (P = .64). This study shows that an initial dislocation episode after RSA with use of this implant can be successfully managed with closed reduction and temporary immobilization in more than half of cases. Given that outcomes after revision surgery are not different from those after closed treatment, we would continue to recommend an initial attempt at closed reduction in the office setting in all cases of postoperative RSA dislocation.

Research paper thumbnail of Anesthetic Effects on Neuroelectric Events

Seminars in Hearing, 1988

Research paper thumbnail of Neurophysiological monitoring of spinal cord function during instrumented anterior cervical fusion

The Spine Journal, 2004

BACKGROUND CONTEXT: Somatosensory evoked potentials (SSEPs) monitor global spinal cord function, ... more 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.

Research paper thumbnail of P27. Complementary use of EMG and transcranial electrical MEPs for detection of iatrogenic nerve root injury during instrumented lumbosacral fusion

The Spine Journal, 2004

BACKGROUND CONTEXT: Compression fracture of the vertebral body is common, especially in elderly. ... more BACKGROUND CONTEXT: Compression fracture of the vertebral body is common, especially in elderly. Vertebral compression fractures usually are caused by osteoporosis, and range from mild to severe. Osteoporotic vertebral collapse with intravertebral cleft causes localized low back pain associated with instability and/or kyphosis, leading to inability to perform activities of daily living, and life-threatening decline in the elderly patient who already has decreased reserves. Recently, percutaneous vertebroplasty became a widely accepted therapeutic option in osteoporotic fractures of the vertebral bodies which is employed in more and more patients. Under image guidance, the method can be safely performed and provides a high success rate regarding stabilization of vertebral fractures and pain relief. PURPOSE: The purpose of this study is to investigate a minimum of 1year follow-up clinical results of vertebroplasty by percutaneous transpedicular injection of bioactive calcium phosphate cement (CPC) under local anesthesia for osteoporotic vertebral collapse. STUDY DESIGN/SETTING: A retrospective study. PATIENT SAMPLE: Ten consecutive patients with severe low back pain but no neural compromise associated with vertebral collapse underwent percutaneous transpedicular vertebroplasty using CPC under local anesthesia. There were 3 males and 7 females with a mean age of 76 years (66-84 years). The level of vertebroplasty was T11 in 3 cases and T12 in 7 cases. Follow-up period averaged 18 months (13-21 months). OUTCOME MEASURES: Clinical outcomes were evaluated low back pain response using a visual analog scale (VAS). Radiographic evaluation was a wedging angle of collapsed vertebra and union rates. Intravertebral instability was investigated by flexion-extension film and CT. METHODS: Clinical and radiographic assessments were performed assessed preoperatively, immediate postoperatively, and at the final follow-up. RESULTS: In clinical outcomes, at the preoperative, immediate postoperative and the final follow-up, VAS of low back pain was 7.1, 3.9, 3.9. Low back pain was decreased in eight cases (80%) at one day after surgery. However, pain relief was not maintained in two cases at the last follow up. In radiographic evaluation, the average of wedging angle of collapsed vertebra was 22 degrees preoperatively, 13 degrees immediately after surgery, and 24 degrees at final follow-up. Union rate was 80%, but 20% remained instability of intravertebral cleft. Three cases achieved anterior bony bridging in spite of intervertebral necrosis. CONCLUSIONS: Percutaneous transpedicular vertebroplasty using CPC is less invasive procedure that provides early relief of pain. The current results suggested that this procedure alleviated low back pain associated with osteoporotic vertebral collapse, but maintenance of pain relief and kyphosis correction was not encouraging. Also, almost all cases could achieve pain relief immediately after the procedure, suggesting that the cause of low back pain associated with vertebral collapse might not be only a mechanical instability of intravertebral cleft. The limitation of this procedure was that correction of kyphosis could not be maintained, and CPC alone could not be played a part in the anterior column support.

Research paper thumbnail of 3:47 Provocative transcranial motor-evoked potential testing of anterior segmental arteries before ligation

The Spine Journal, 2002

later by complete SSEP loss, never regained neurophysiological function and awoke with dense para... more later by complete SSEP loss, never regained neurophysiological function and awoke with dense paraplegia as predicted. Relationship between findings and existing knowledge: These data suggest that TCEMEPs are a more sensitive and earlier indicator of impending spinal cord ischemic injury then somatosensory evoked potentials. Overall significance of findings: This study highlights the feared limitation of SSEPs for spinal cord monitoring; namely, the potential for false-negative results in the presence of impending spinal cord ischemic injury. As a result, TCEMEPs are recommended as the primary monitoring modality with SSEPs serving adjunctively. Disclosures: Device or drug: Digitimer D-185 Multi-pulse Motor Evoked Potential Stimulator. Status: investigational. Conflict of interest: No conflicts.

Research paper thumbnail of 3:41 Transcranial electric motor-evoked potential monitoring as an early indicator of emerging thoracic spinal cord ischemic injury

Research paper thumbnail of Detection of Brachial Plexopathy during Transaxillary Robotic Thyroidectomy

Research paper thumbnail of Characterization of Neurophysiologic Alerts During Anterior Cervical Spine Surgery

Spine, 2006

A retrospective review of neurophysiologic alerts during anterior cervical surgery. To examine in... more A retrospective review of neurophysiologic alerts during anterior cervical surgery. To examine incidence and types of neurophysiologic alerts and their correlation with new postoperative neurologic deficits after anterior cervical discectomy or corpectomy procedures. 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. 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. 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. 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.

Research paper thumbnail of Multimodality Monitoring of Transcranial Electric Motor and Somatosensory-Evoked Potentials During Surgical Correction of Spinal Deformity in Patients With Cerebral Palsy and Other Neuromuscular Disorders

Spine, 2003

This prospective, descriptive study determined the reliability of transcranial electric motor and... more This prospective, descriptive study determined the reliability of transcranial electric motor and posterior tibial nerve somatosensory-evoked potentials in children with neuromuscular scoliosis. To assess the applicability of transcranial electric motor and posterior tibial nerve somatosensory-evoked potentials during surgical correction of neuromuscular scoliosis, particularly with cerebral palsy-related deformity. During corrective spinal surgery for neuromuscular scoliosis, intraoperative multimodality spinal cord monitoring is recommended. There exist conflicting, retrospective studies regarding the reliability of spinal cord monitoring in patients with neuromuscular scoliosis. Transcranial electric motor potentials and posterior tibial nerve somatosensory-evoked potentials were monitored in all patients presenting for spinal fusion between 2000 and 2001. Anesthesia was standardized for all patients. There were 68 patients subdivided into two subject groups. Group I consisted of 39 patients with neuromuscular scoliosis associated with cerebral palsy, and Group II consisted of 29 children with neuromuscular scoliosis due to a disease process other than cerebral palsy. Five of the 68 patients had significant amplitude changes in 1 or both monitoring methods during surgery relative to baseline. Of these, one had permanent neurologic deficit despite standard intervention. Somatosensory-evoked potentials were monitored successfully in 82% of the cerebral palsy and 86% of the noncerebral palsy patients. Transcranial electric motor-evoked potentials, on the other hand, were monitorable in 63% of patients with mild or moderate degrees of cerebral palsy and 39% of those with severe involvement. Eighty-six percent of those with noncerebral palsy-related neuromuscular scoliosis had recordable motor-evoked potentials at baseline. Both transcranial electric motor and posterior tibial nerve somatosensory-evoked potentials can be monitored reliably in most patients with neuromuscular scoliosis. Those with severe cerebral palsy present the greatest challenge to successful neurophysiologic monitoring.

Research paper thumbnail of Neurophysiological monitoring under anesthesia to position a child with extreme lumbar spine flexion for MRI and CT scan

Pediatric Anesthesia, 2006

A novel application of neurophysiological monitoring enabled us safely to anesthetize and positio... more 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.

Research paper thumbnail of 25. Neurophysiological detection of iatrogenic C5 nerve root injury during anterior cervical laminectomy and laminoplasty

The Spine Journal, 2004

poor treatment outcomes. High pain intensity is indicative of more than just self-reported pain. ... more poor treatment outcomes. High pain intensity is indicative of more than just self-reported pain. When individuals report extreme levels of pain intensity after extensive PRE-rehab treatment and disability averaging 16 months, they are likely also to display major barriers to recovery and higher levels of depression, physical inhibition, and perceived dysfunction. The 13% of patients still complaining of extreme pain intensity after rehabilitation have particularly poor outcomes, and are at risk for substantially higher health utilization costs and lower work productivity over the one year posttreatment. Early recognition may lead to strategies to decrease this risk. DISCLOSURES: No disclosures. CONFLICT OF INTEREST: No Conflicts.

Research paper thumbnail of 58. The Role of TceMEPs in Detection of Iatrogenic Spinal Nerve Root Deficit during Instrumented Lumbosacral Fusion

Research paper thumbnail of Intraoperative Monitoring of the Processed Electroencephalogram

Seminars in Hearing, 1988

Research paper thumbnail of P51. Are dermatomal somatosensory evoked potentials useful for assessing adequacy of cervical nerve root decompression?

The Spine Journal, 2003

reports on a high percentage of their original patients. This paper reviews the results in those ... more reports on a high percentage of their original patients. This paper reviews the results in those patients. RESULTS: Thirty-three of 43 eligible patients (77%) were evaluated including 30 patients who reported for examination and X-ray and 3 additional patients located by telephone survey. Before fusion surgery the average patient had two prior decompression surgeries and a history of back pain for 14.9 years and leg pain for 8.4 years. Average age at surgery was 50.4 years. Smokers included 15 patients with an average of 23.9 pack years of smoking. Average post-surgical follow-up was 115.5 months. Clinical success, defined by a modified Prolo score, included patients whose status was excellent, good, or fair with a minimum of three-points of improvement. Clinical success was achieved in 32/37 (86.5%) at 24 months and in 29/ 33 (87.8%) at ten years. This included 61% excellent, 27% good, and 12% fair results. Fusion success was reported in 37/37 (100%) of patients at 24 months and in 29/30 (96.7%) at ten years. One fusion failure was identified in a patient who was judged fused at 24 months. Patient satisfaction was reported in 31/33 (93.9%). Further lumbar surgery was done in 23 patients: in 18 patients for elective removal of pedicle screws and in 5 patients to extend the fusion to adjacent levels. Sagittal plane alignment was not measured in the original study. At ten-years, the L4-S1 lordosis averaged 23.3 degrees. Adjacent segment degeneration occurred in 60% of patients but was clinically significant in only 20%. Smokers had equal clinical and fusion success with non-smokers at 24 months and 10 years and had adjacent segment degeneration in 26.7%, a rate significantly lower than non-smokers at 66.7%. DISCUSSION: Since the original study, improved surgical techniques have allowed improvement in sagittal plane alignment with these implants. Additionally, tapered or wedged-shaped implants have facilitated achievement of normal lordosis. It is likely but unproven that the incidence of adjacent segment degeneration was related to the loss of 10 to 15 degrees of lordosis. The lower rate of adjacent degeneration in smokers is counterintuitive. The study protocol recommended removal of pedicle screws after bony fusion. Routine removal of pedicle screws is not currently recommended. CONCLUSIONS: The high rate of clinical success, fusion success, and patient satisfaction at 24 months was maintained at ten-year follow-up.

Research paper thumbnail of Efficacy of Spinal Cord Monitoring in Scoliosis Surgery in Patients with Cerebral Palsy

Journal of Spinal Disorders, 1996

Although spinal cord monitoring is recommended during scoliosis surgery, a review from Rancho Los... more Although spinal cord monitoring is recommended during scoliosis surgery, a review from Rancho Los Amigos Medical Center stated that they were only able to obtain reproducible tracings in 53% of cerebral palsy patients. To ascertain that monitoring is both feasible and reliable in these patients, we reviewed the records of 34 consecutive patients with cerebral palsy who had scoliosis surgery at our institution. Spinal cord function was monitored by recording peripheral nerve, cervical/brainstem, and cortical somatosensory evoked potentials to posterior tibial nerve stimulation. Reproducible tracings were achieved in 31 of the 34 patients. Significant intraoperative changes were recorded in 12 of the 31 monitored patients, usually related to and requiring some modifications of the instrumentation. We conclude that with careful technique, spinal cord monitoring using cervical/brainstem somatosensory evoked potentials can be reliably achieved in most patients with cerebral palsy undergoing scoliosis surgery.

Research paper thumbnail of Prevention of Positional Brachial Plexopathy During Surgical Correction of Scoliosis

Journal of Spinal Disorders, 2000

Continuous intraoperative monitoring of spinal cord function using somatosensory evoked potential... more Continuous intraoperative monitoring of spinal cord function using somatosensory evoked potentials (SSEP) has gained nearly universal acceptance as a reliable and sensitive method for detecting and possibly preventing neurologic injury during surgical correction of spinal deformities. In several reports, spinal cord injury was identified successfully based on changes in SSEP response characteristics, specifically amplitude and latency. Less well documented and used, however, is monitoring of peripheral nerve function with SSEPs to identify and prevent the neurologic sequelae of prolonged prone positioning on a spinal frame. The authors describe a patient who underwent surgical removal of spinal instrumentation but was not monitored. A brachial plexopathy developed in this patient from pressure on the axilla exerted by a Relton-Hall positioning frame during spinal surgery. In addition, data are presented from 15 of 500 consecutive pediatric patients who underwent surgical correction of scoliosis between 1993 and 1997 with whom intermittent monitoring of ulnar nerve SSEPs was used successfully to identify impending brachial plexopathy, a complication of prone positioning. A statistically significant reduction in ulnar nerve SSEP amplitude was observed in 18 limbs of the 500 patients (3.6%) reviewed. Repositioning the arm(s) or shoulders resulted in nearly immediate improvement of SSEP amplitude, and all awoke without signs of brachial plexopathy. This complication can be avoided by monitoring SSEPs to ulnar nerve stimulation for patients placed in the prone position during spinal surgery.

Research paper thumbnail of Influence of Rigid Spinal Instrumentation on the Neurogenic Motor Evoked Potential

Journal of Spinal Disorders, 1996

Three case reports are presented to illustrate how placement of spinal instrumentation obliterate... more Three case reports are presented to illustrate how placement of spinal instrumentation obliterates previously normal neurogenic motor evoked potentials (NMEPs) elicited by transosseous electrical stimulation. This results in an unacceptably high false-positive rate for NMEP recordings during scoliosis surgery. The loss of the NMEPs was attributed to shunting of electrical current from JO5 spinous process stimulating needles through the metal rod to ground, thus preventing adequate stimulation to the spinal cord. A modification of the transosseous technique with epidural stimulation to improve test reliability is described.

Research paper thumbnail of Influence of Nitrous Oxide on Posterior Tibial Nerve Cortical Somatosensory Evoked Potentials

Journal of Spinal Disorders, 1997

The suppressive effect of the halogenated inhalation anesthesia on cortical somatosensory evoked ... more The suppressive effect of the halogenated inhalation anesthesia on cortical somatosensory evoked potentials (cSSEPs) has been well documented. Less studied and appreciated is the effect of nitrous oxide often with a narcotic as an alternative to a potent agent for spinal cord monitoring. This study sought to define more clearly the influence of nitrous oxide on cSSEPs elicited to posterior tibial nerve stimulation. A secondary purpose was to demonstrate the advantage of a total intravenous propofol anesthesia in facilitating uncompromised large-amplitude cSSEPs. Fifty adult patients undergoing anterior cervical discectomy served as the study sample. Brainstem and cortical posterior tibial nerve SSEPs were recorded under two independent anesthesia conditions, namely, nitrous oxide and propofol. Results demonstrated a significant amplitude reduction and latency prolongation with the nitrous oxide versus propofol protocol. cSSEP amplitude with propofol was, on the average, approximately two times larger than that with nitrous oxide. Based on these findings, the use of nitrous-oxide anesthesia is not recommended when limited to monitoring cSSEPs that are already amplitude compromised secondary to existing spinal cord disease.

Research paper thumbnail of Comparison of transcranial electric motor and somatosensory evoked potential monitoring during cervical spine surgery

The Journal of bone and joint surgery. American volume, 2004

There has been little enthusiasm for somatosensory evoked potential monitoring in cervical spine ... more 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. 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...

Research paper thumbnail of The Retrolabyrinthine Transsigmoid Approach to Midbasilar Artery Aneurysms

The Laryngoscope, 1992

One of the more challenging problems in surgery of the petroclival area are aneurysms of the midb... more One of the more challenging problems in surgery of the petroclival area are aneurysms of the midbasilar trunk and vertebrobasilar artery junction. Aneurysms in this area are difficult to access. Most approaches result in a deep and narrow surgical field which includes ...

Research paper thumbnail of Results of closed management of acute dislocation after reverse shoulder arthroplasty

Journal of Shoulder and Elbow Surgery, 2014

Postoperative instability continues to be one of the most common complications limiting outcomes ... more Postoperative instability continues to be one of the most common complications limiting outcomes of reverse shoulder arthroplasty (RSA). The optimal management of this complication remains unknown. The purpose of this study was to evaluate the outcomes of patients with postoperative dislocation after RSA managed with closed reduction. All patients who were treated with a closed reduction for dislocation after RSA in the period between May 2002 and September 2011 were identified and retrospectively reviewed. Final outcomes including recurrent instability, need for revision surgery, American Shoulder and Elbow Surgeons outcome score, and range of motion were evaluated. A total of 21 patients were identified. Nearly 50% of cases (10 of 21) had previous surgery, with 80% (8 of 10) of these being previous arthroplasty. The average time to first dislocation was 200 days, with 62% (13 of 21) occurring in the first 90 days. At average follow-up of 28 months, 62% of these shoulders remained stable (13 of 21), 29% required revision surgery (6 of 21), and 9% remained unstable (2 of 21). The average American Shoulder and Elbow Surgeons score was 68.0 for patients treated with closed reduction for instability and 62.7 for those treated with revision surgery (P = .64). This study shows that an initial dislocation episode after RSA with use of this implant can be successfully managed with closed reduction and temporary immobilization in more than half of cases. Given that outcomes after revision surgery are not different from those after closed treatment, we would continue to recommend an initial attempt at closed reduction in the office setting in all cases of postoperative RSA dislocation.

Research paper thumbnail of Anesthetic Effects on Neuroelectric Events

Seminars in Hearing, 1988

Research paper thumbnail of Neurophysiological monitoring of spinal cord function during instrumented anterior cervical fusion

The Spine Journal, 2004

BACKGROUND CONTEXT: Somatosensory evoked potentials (SSEPs) monitor global spinal cord function, ... more 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.

Research paper thumbnail of P27. Complementary use of EMG and transcranial electrical MEPs for detection of iatrogenic nerve root injury during instrumented lumbosacral fusion

The Spine Journal, 2004

BACKGROUND CONTEXT: Compression fracture of the vertebral body is common, especially in elderly. ... more BACKGROUND CONTEXT: Compression fracture of the vertebral body is common, especially in elderly. Vertebral compression fractures usually are caused by osteoporosis, and range from mild to severe. Osteoporotic vertebral collapse with intravertebral cleft causes localized low back pain associated with instability and/or kyphosis, leading to inability to perform activities of daily living, and life-threatening decline in the elderly patient who already has decreased reserves. Recently, percutaneous vertebroplasty became a widely accepted therapeutic option in osteoporotic fractures of the vertebral bodies which is employed in more and more patients. Under image guidance, the method can be safely performed and provides a high success rate regarding stabilization of vertebral fractures and pain relief. PURPOSE: The purpose of this study is to investigate a minimum of 1year follow-up clinical results of vertebroplasty by percutaneous transpedicular injection of bioactive calcium phosphate cement (CPC) under local anesthesia for osteoporotic vertebral collapse. STUDY DESIGN/SETTING: A retrospective study. PATIENT SAMPLE: Ten consecutive patients with severe low back pain but no neural compromise associated with vertebral collapse underwent percutaneous transpedicular vertebroplasty using CPC under local anesthesia. There were 3 males and 7 females with a mean age of 76 years (66-84 years). The level of vertebroplasty was T11 in 3 cases and T12 in 7 cases. Follow-up period averaged 18 months (13-21 months). OUTCOME MEASURES: Clinical outcomes were evaluated low back pain response using a visual analog scale (VAS). Radiographic evaluation was a wedging angle of collapsed vertebra and union rates. Intravertebral instability was investigated by flexion-extension film and CT. METHODS: Clinical and radiographic assessments were performed assessed preoperatively, immediate postoperatively, and at the final follow-up. RESULTS: In clinical outcomes, at the preoperative, immediate postoperative and the final follow-up, VAS of low back pain was 7.1, 3.9, 3.9. Low back pain was decreased in eight cases (80%) at one day after surgery. However, pain relief was not maintained in two cases at the last follow up. In radiographic evaluation, the average of wedging angle of collapsed vertebra was 22 degrees preoperatively, 13 degrees immediately after surgery, and 24 degrees at final follow-up. Union rate was 80%, but 20% remained instability of intravertebral cleft. Three cases achieved anterior bony bridging in spite of intervertebral necrosis. CONCLUSIONS: Percutaneous transpedicular vertebroplasty using CPC is less invasive procedure that provides early relief of pain. The current results suggested that this procedure alleviated low back pain associated with osteoporotic vertebral collapse, but maintenance of pain relief and kyphosis correction was not encouraging. Also, almost all cases could achieve pain relief immediately after the procedure, suggesting that the cause of low back pain associated with vertebral collapse might not be only a mechanical instability of intravertebral cleft. The limitation of this procedure was that correction of kyphosis could not be maintained, and CPC alone could not be played a part in the anterior column support.

Research paper thumbnail of 3:47 Provocative transcranial motor-evoked potential testing of anterior segmental arteries before ligation

The Spine Journal, 2002

later by complete SSEP loss, never regained neurophysiological function and awoke with dense para... more later by complete SSEP loss, never regained neurophysiological function and awoke with dense paraplegia as predicted. Relationship between findings and existing knowledge: These data suggest that TCEMEPs are a more sensitive and earlier indicator of impending spinal cord ischemic injury then somatosensory evoked potentials. Overall significance of findings: This study highlights the feared limitation of SSEPs for spinal cord monitoring; namely, the potential for false-negative results in the presence of impending spinal cord ischemic injury. As a result, TCEMEPs are recommended as the primary monitoring modality with SSEPs serving adjunctively. Disclosures: Device or drug: Digitimer D-185 Multi-pulse Motor Evoked Potential Stimulator. Status: investigational. Conflict of interest: No conflicts.

Research paper thumbnail of 3:41 Transcranial electric motor-evoked potential monitoring as an early indicator of emerging thoracic spinal cord ischemic injury

Research paper thumbnail of Detection of Brachial Plexopathy during Transaxillary Robotic Thyroidectomy

Research paper thumbnail of Characterization of Neurophysiologic Alerts During Anterior Cervical Spine Surgery

Spine, 2006

A retrospective review of neurophysiologic alerts during anterior cervical surgery. To examine in... more A retrospective review of neurophysiologic alerts during anterior cervical surgery. To examine incidence and types of neurophysiologic alerts and their correlation with new postoperative neurologic deficits after anterior cervical discectomy or corpectomy procedures. 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. 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. 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. 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.

Research paper thumbnail of Multimodality Monitoring of Transcranial Electric Motor and Somatosensory-Evoked Potentials During Surgical Correction of Spinal Deformity in Patients With Cerebral Palsy and Other Neuromuscular Disorders

Spine, 2003

This prospective, descriptive study determined the reliability of transcranial electric motor and... more This prospective, descriptive study determined the reliability of transcranial electric motor and posterior tibial nerve somatosensory-evoked potentials in children with neuromuscular scoliosis. To assess the applicability of transcranial electric motor and posterior tibial nerve somatosensory-evoked potentials during surgical correction of neuromuscular scoliosis, particularly with cerebral palsy-related deformity. During corrective spinal surgery for neuromuscular scoliosis, intraoperative multimodality spinal cord monitoring is recommended. There exist conflicting, retrospective studies regarding the reliability of spinal cord monitoring in patients with neuromuscular scoliosis. Transcranial electric motor potentials and posterior tibial nerve somatosensory-evoked potentials were monitored in all patients presenting for spinal fusion between 2000 and 2001. Anesthesia was standardized for all patients. There were 68 patients subdivided into two subject groups. Group I consisted of 39 patients with neuromuscular scoliosis associated with cerebral palsy, and Group II consisted of 29 children with neuromuscular scoliosis due to a disease process other than cerebral palsy. Five of the 68 patients had significant amplitude changes in 1 or both monitoring methods during surgery relative to baseline. Of these, one had permanent neurologic deficit despite standard intervention. Somatosensory-evoked potentials were monitored successfully in 82% of the cerebral palsy and 86% of the noncerebral palsy patients. Transcranial electric motor-evoked potentials, on the other hand, were monitorable in 63% of patients with mild or moderate degrees of cerebral palsy and 39% of those with severe involvement. Eighty-six percent of those with noncerebral palsy-related neuromuscular scoliosis had recordable motor-evoked potentials at baseline. Both transcranial electric motor and posterior tibial nerve somatosensory-evoked potentials can be monitored reliably in most patients with neuromuscular scoliosis. Those with severe cerebral palsy present the greatest challenge to successful neurophysiologic monitoring.

Research paper thumbnail of Neurophysiological monitoring under anesthesia to position a child with extreme lumbar spine flexion for MRI and CT scan

Pediatric Anesthesia, 2006

A novel application of neurophysiological monitoring enabled us safely to anesthetize and positio... more 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.