Joshua D. Auerbach

Background: Despite the many reports attesting to the efficacy of intraoperative somatosensory evoked potential monitoring in reducing the prevalence of iatrogenic spinal cord injury during corrective scoliosis surgery, these afferent neurophysiological signals can provide only indirect evidence of injury to the motor tracts since they monitor posterior column function. Early reports on the use of transcranial electric motor evoked potentials to monitor the corticospinal motor tracts directly suggested that the method holds great promise for improving detection of emerging spinal cord injury. We sought to compare the efficacy of these two methods of monitoring to detect impending iatrogenic neural injury during scoliosis surgery. Methods: We reviewed the intraoperative neurophysiological monitoring records of 1121 consecutive patients (834 female and 287 male) with adolescent idiopathic scoliosis (mean age, 13.9 years) treated between 2000 and 2004 at four pediatric spine centers. The same group of experienced surgical neurophysiologists monitored spinal cord function in all patients with use of a standardized multimodality technique with the patient under total intravenous anesthesia. A relevant neurophysiological change (an alert) was defined as a reduction in amplitude (unilateral or bilateral) of at least 50% for somatosensory evoked potentials and at least 65% for transcranial electric motor evoked potentials compared with baseline. Results: Thirty-eight (3.4%) of the 1121 patients had recordings that met the criteria for a relevant signal change (i.e., an alert). Of those thirty-eight patients, seventeen showed suppression of the amplitude of transcranial electric motor evoked potentials in excess of 65% without any evidence of changes in somatosensory evoked potentials. In nine of the thirty-eight patients, the signal change was related to hypotension and was corrected with augmentation of the blood pressure. The remaining twenty-nine patients had an alert that was related directly to a surgical maneuver. Three alerts occurred following segmental vessel clamping, and the remaining twenty-six were related to posterior instrumentation and correction. Nine (35%) of these twenty-six patients with an instrumentation-related alert, or 0.8% of the cohort, awoke with a transient motor and/or sensory deficit. Seven of these nine patients presented solely with a motor deficit, which was detected by intraoperative monitoring of transcranial electric motor evoked potentials in all cases, and two patients had only sensory symptoms. Somatosensory evoked potential monitoring failed to identify a motor deficit in four of the seven patients with a confirmed motor deficit. Furthermore, when changes in somatosensory evoked potentials occurred, they lagged behind the changes in transcranial electric motor evoked potentials by an average of approximately five minutes. With an appropriate response to the alert, the motor or sensory deficit resolved in all nine patients within one to ninety days. Conclusions: This study underscores the advantage of monitoring the spinal cord motor tracts directly by recording transcranial electric motor evoked potentials in addition to somatosensory evoked potentials. Transcranial electric motor evoked potentials are exquisitely sensitive to altered spinal cord blood flow due to either hypotension or a vascular insult. Moreover, changes in transcranial electric motor evoked potentials are detected earlier than are changes in somatosensory evoked potentials, thereby facilitating more rapid identification of impending spinal cord injury. Level of Evidence: Diagnostic Level I. See Instructions to Authors for a complete description of levels of evidence.

STUDY DESIGN: A retrospective review. OBJECTIVE: To characterize the risk factors for the development of major complications in 3-column osteotomies and determine whether the presence of a major complication affects ultimate clinical outcomes. SUMMARY OF BACKGROUND DATA: Three-column spinal osteotomies, including pedicle subtraction osteotomy (PSO) and vertebral column resection (VCR), are common techniques to correct severe and/or rigid spinal deformities. METHODS: Two hundred forty consecutive PSO (n = 156) and VCR (n = 84) procedures in 237 patients were performed at a single institution between 1995 and 2008. Of these, 105 patients (87 PSOs, 18 VCRs) had complete preoperative and minimum 2-year postoperative clinical outcomes data available for analysis. Using established criteria, we reported complications as major or minor and further stratified complications as surgical versus medical and permanent versus transient. Risk factors for complications and their effect on Scoliosis Research Society (SRS) clinical outcomes at baseline and at 2 years or more were assessed. RESULTS: Major medical and surgical complications occurred at similar rates in both PSOs and VCRs (38%, 33 of 87 vs. 22%, 4 of 18; P = 0.28). Overall, 24.8% (26 of 105) experienced major surgical complications (3 permanent) and 15.2% (16 of 105) experienced major medical complications (4 permanent). Patients with PSO were older (53 vs. 29 yr; P < 0.001), had greater estimated blood loss (1867 vs. 1278 mL; P = 0.02), and showed a trend toward fewer fused levels (10.1 vs. 12.2; P = 0.06). Risk factors for major complications included preoperative sagittal imbalance of 40 mm or more (P = 0.01), age 60 years and older (P = 0.01), and the presence of 3 or more medical comorbidities (P = 0.04). Both groups improved significantly from baseline in SRS subscores; however, patients with PSO started off worse but improved more than VCRs in both the pain (+1.0 vs. +0.1; P < 0.001) and function (+0.6 vs. +0.2; P = 0.01) domains, with no differences in final satisfaction (4.1 vs. 4.3; P = 0.54). PSO and VCR patients with no complications had slightly higher satisfaction scores than patients with minor-only complications, major transient complications, and major permanent complications. There were no significant differences among the groups with respect to change in SRS subscores from baseline, and all complication groups improved significantly from baseline (P = 0.04). CONCLUSION: Major complications occurred in 35% of 3-column osteotomies and at similar rates for both PSO (38%) and VCR (22%) procedures. The presence of a major complication did not affect the ultimate clinical outcomes at 2 years or more.

BACKGROUND: Stress exacerbates many neuropsychiatric disorders associated with prefrontal cortical (PFC) dysfunction. Stress also impairs the working memory functions of the PFC. Although stress research has focused on dopaminergic mechanisms, stress also increases norepinephrine (NE) release in PFC, and intra-PFC infusions of NE alpha-1-adrenoceptor agonists impair working memory. The current study examined whether NE alpha-1-adrenoceptor actions in PFC contribute to stress-induced deficits in working memory performance. METHODS: Rats were treated with a pharmacological stressor, FG7142 (30 mg/kg) or vehicle 30 min before testing on a test of spatial working memory, delayed alternation. The alpha-1-adrenoceptor antagonist, urapidil (0.1 microgram/0.5 microL), or saline vehicle, was infused into the PFC 15 min before delayed alternation testing. RESULTS: As observed previously, FG7142 significantly impaired the accuracy of delayed alternation performance, and induced a perseverative pattern of responding consistent with PFC dysfunction. FG7142 also slowed motor response times. Infusion of urapidil into the PFC completely reversed the FG7142-induced impairment in delayed alternation performance, but did not alter the slowed motor responding. CONCLUSIONS: These findings indicate that alpha-1-adrenoceptor stimulation in the PFC contributes to stress-induced impairments in PFC cognitive functions. These neurochemical actions may contribute to symptoms of working memory impairment, poor attention regulation, or disinhibited behaviors in neuropsychiatric disorders sensitive to stress exposure.

Background: Despite the many reports attesting to the efficacy of intraoperative somatosensory evoked potential monitoring in reducing the prevalence of iatrogenic spinal cord injury during corrective scoliosis surgery, these afferent neurophysiological signals can provide only indirect evidence of injury to the motor tracts since they monitor posterior column function. Early reports on the use of transcranial electric motor evoked potentials to monitor the corticospinal motor tracts directly suggested that the method holds great promise for improving detection of emerging spinal cord injury. We sought to compare the efficacy of these two methods of monitoring to detect impending iatrogenic neural injury during scoliosis surgery. Methods: We reviewed the intraoperative neurophysiological monitoring records of 1121 consecutive patients (834 female and 287 male) with adolescent idiopathic scoliosis (mean age, 13.9 years) treated between 2000 and 2004 at four pediatric spine centers. The same group of experienced surgical neurophysiologists monitored spinal cord function in all patients with use of a standardized multimodality technique with the patient under total intravenous anesthesia. A relevant neurophysiological change (an alert) was defined as a reduction in amplitude (unilateral or bilateral) of at least 50% for somatosensory evoked potentials and at least 65% for transcranial electric motor evoked potentials compared with baseline. Results: Thirty-eight (3.4%) of the 1121 patients had recordings that met the criteria for a relevant signal change (i.e., an alert). Of those thirty-eight patients, seventeen showed suppression of the amplitude of transcranial electric motor evoked potentials in excess of 65% without any evidence of changes in somatosensory evoked potentials. In nine of the thirty-eight patients, the signal change was related to hypotension and was corrected with augmentation of the blood pressure. The remaining twenty-nine patients had an alert that was related directly to a surgical maneuver. Three alerts occurred following segmental vessel clamping, and the remaining twenty-six were related to posterior instrumentation and correction. Nine (35%) of these twenty-six patients with an instrumentation-related alert, or 0.8% of the cohort, awoke with a transient motor and/or sensory deficit. Seven of these nine patients presented solely with a motor deficit, which was detected by intraoperative monitoring of transcranial electric motor evoked potentials in all cases, and two patients had only sensory symptoms. Somatosensory evoked potential monitoring failed to identify a motor deficit in four of the seven patients with a confirmed motor deficit. Furthermore, when changes in somatosensory evoked potentials occurred, they lagged behind the changes in transcranial electric motor evoked potentials by an average of approximately five minutes. With an appropriate response to the alert, the motor or sensory deficit resolved in all nine patients within one to ninety days. Conclusions: This study underscores the advantage of monitoring the spinal cord motor tracts directly by recording transcranial electric motor evoked potentials in addition to somatosensory evoked potentials. Transcranial electric motor evoked potentials are exquisitely sensitive to altered spinal cord blood flow due to either hypotension or a vascular insult. Moreover, changes in transcranial electric motor evoked potentials are detected earlier than are changes in somatosensory evoked potentials, thereby facilitating more rapid identification of impending spinal cord injury. Level of Evidence: Diagnostic Level I. See Instructions to Authors for a complete description of levels of evidence.

In Brief Study Design. T1ρ relaxation was quantified and correlated with intervertebral disc degeneration and proteoglycan content in cadaveric human lumbar spine tissue. Objective. To show the use of T1ρ-weighted magnetic resonance imaging (MRI) for the assessment of degeneration and proteoglycan content in the human intervertebral disc. Summary of Background Data. Loss of proteoglycan in the nucleus pulposus occurs during early degeneration. Conventional MRI techniques cannot detect these early changes in the extracellular matrix content of the disc. T1ρ MRI is sensitive to changes in proteoglycan content of articular cartilage and may, therefore, be sensitive to proteoglycan content in the intervertebral disc. Methods. Intact human cadaveric lumbar spines were imaged on a clinical MR scanner. Average T1ρ in the nucleus pulposus was calculated from quantitative T1ρ maps. After MRI, the spines were dissected, and proteoglycan content of the nucleus pulposus was measured. Finally, the stage of degeneration was graded using conventional T2 images. Results. T1ρ decreased linearly with increasing degeneration (r = −0.76, P < 0.01) and age (r = −0.76, P < 0.01). Biochemical analysis revealed a strong linear correlation between T1ρ and sulfated-glycosaminoglycan content. T1ρ was moderately correlated with water content. Conclusions. Results from this study suggest that T1ρ may provide a tool for the diagnosis of early degenerative changes in the disc. T1ρ-weighted MRI is a noninvasive technique that may provide higher dynamic range than T2 and does not require a high static field or exogenous contrast agents. Quantitative measurement of T1ρ relaxation in the intervertebral disc was performed. T1ρ was strongly correlated with degenerative grade and sulfated-glycosaminoglycan content of the nucleus pulposus. Because early degenerative changes are marked by a loss of proteoglycan in the disc, this technique provides a potential tool for noninvasive diagnosis of early disc degeneration.