Diagnostic accuracy of intraoperative neuromonitoring in transcarotid artery revascularization

BACKGROUND

In recent years, transcarotid artery revascularization (TCAR) has emerged as a safe and effective alternative to carotid artery stenting. While intraoperative neuromonitoring (IONM) techniques such as electroencephalogram (EEG) and somatosensory evoked potentials (SSEPs) are often employed during TCAR, there is limited research on their diagnostic accuracy.

METHODS

The authors retrospectively reviewed a multi-institutional IONM database of TCAR procedures performed with EEG and SSEP monitoring. A total of 516 TCAR procedures were included in this study. Significant changes in EEG and/or SSEPs, surgeon's interventions, resolution of significant changes, and immediate postoperative neurological outcome were documented. Sensitivity, specificity, positive and negative predictive values were calculated.

RESULTS

The incidence of intraoperative onset new neurologic deficit was 0.4%. Significant changes in EEG and/or SSEPs occurred in 5.4% of the cases. Of the cases with IONM alerts, 78.5% returned to baseline with a surgical or hemodynamic intervention. From the cases with unresolved IONM alerts, 33.3% woke up with a new neurological deficit. The overall sensitivity and specificity for IONM was 100% and 99.2%, respectively. The positive predictive value was 33.3% and the negative predictive value was 100%.

CONCLUSIONS

IONM during TCAR offers high sensitivity and specificity in predicting postoperative outcome. Patients with resolved IONM alerts had immediate neurological outcomes that were comparable to those who had no IONM alerts.

Effects of anode position on pedicle screw testing during lumbosacral spinal fusion surgery

OF BACKGROUND DATA

Pedicle screws are commonly placed with lumbar/lumbosacral fusions. Triggered electromyography (tEMG), which employs the application of electrical current between the screw and a complementary anode to determine thresholds of conduction, may be utilized to confirm the safe placement of such implants. While previous research has established clinical thresholds associated with safe screw placement, there is variability in clinical practice of anode placement which could lead to unreliable measurements.

PURPOSE

To determine the variance in pedicle screw stimulation thresholds when using four unique anode locations (ipsilateral/contralateral and paraspinal/gluteal relative to tested pedicle screws).

STUDY DESIGN

Prospective cohort study. Tertiary medical center.

PATIENT SAMPLE

Twenty patients undergoing lumbar/lumbosacral fusion with pedicle screws using tEMG OUTCOME MEASURES: tEMG stimulation return values are used to assess varied anode locations and reproducibility based on anode placement.

METHODS

Measurements were assessed across node placement in ipsilateral/contralateral and paraspinal/gluteal locations relative to the screw being assessed. R² coefficients of correlation were determined, and variances were compared with F-tests.

RESULTS

A total of 94 lumbosacral pedicle screws from 20 patients were assessed. Repeatability was verified using two stimulations at each location for a subset of the screws with an R² of 0.96. Comparisons between the four anode locations demonstrated R² values ranging from 0.76 to 0.87. F-tests comparing thresholds between each anode site demonstrated all groups not to be statistically different.

CONCLUSION

The current study, a first-of-its-kind formal evaluation of anode location for pedicle screw tEMG testing, demonstrated very strong repeatability and strong correlation with different locations of anode placement. These results suggest that there is no need to change the side of the anode for testing of left versus right screws, further supporting that placing an anode electrode into gluteal muscle is sufficient and will avoid a sharp ground needle in the surgical field.

C-27 Neuropsychological Differences in 10 Year Long-Term Stable Mild Cognitive Impairment and Converting Mild Cognitive Impairment

Objective

To examine baseline differences in neuropsychological performance between long-term stable mild cognitive impairment (sMCI) and those who convert from MCI to dementia (cMCI), hypothesizing sMCI will perform better on memory measures. While conversion has been previously examined, none examined sMCI with over 10 years follow-up.

Method

Data from the National Alzheimer’s Coordinating Center were used. Participants were defined as sMCI (n = 29) if cognitive status was MCI at first visit and at least 9 subsequent visits (10 total) and cMCI (n = 1887) if cognitive status was MCI at first visit and the participant converted to dementia at any subsequent visit. Participants with any history of stroke, traumatic brain injury, alcohol or drug abuse, or other neurological disorder were excluded. Participants completed neuropsychological measures of global cognition, immediate and delayed verbal memory, working memory, mental manipulation, semantic fluency, processing speed, and confrontational naming. Depressive symptoms were assessed using the Geriatric Depression Scale. The Mann-Whitney-U non-parametric test was used to compare both groups at baseline on all measures. Predictors of sMCI were explored using binomial logistic regression.

Results

Participants did not differ significantly in age, level of education, or depressive symptoms. Comparison between groups at baseline indicate sMCI participants performed significantly better than cMCI on global cognition U = 13673,p < .001, delayed verbal memory U = 14549,p < .001, and semantic fluency U = 15538.5,p < .001. Of these significant measures, none predicted sMCI.

Conclusions

As hypothesized, sMCI performed better on delayed verbal memory, but also semantic fluency and global cognition, though none predicted sMCI. Future research must examine neuropsychological measures of other cognitive domains and their predictive value.

Pollen wall degradation in the Brassicaceae permits cell emergence after pollination

PREMISE OF THE STUDY

Despite attempts to degrade the sporopollenin in pollen walls, this material has withstood a hundred years of experimental treatments and thousands of years of environmental attack in insects and soil. We present evidence that sporopollenin, nonetheless, locally degrades only minutes after pollination in Arabidopsis thaliana flowers, and describe here a two-part pollen germination mechanism in A. thaliana involving both chemical weakening of the exine wall and swelling of the underlying intine.

METHODS

We explored naturally occurring components from pollen and stigma surfaces and found a tripartite mix of hydrogen peroxide, peroxidase and catalase enzymes (all at high levels at the pollination interface) to be experimentally sufficient to degrade the sporopollenin of some Brassicaceae family members.

KEY RESULTS

At pollination, factors carried on the pollen surface may mix with factors on the stigma surface in a reaction that locally oxidizes the exine pollen wall. Hydrogen peroxide, catalases, and peroxidases are biologically present at the right time and place and, when mixed experimentally, are sufficient to degrade the walls of susceptible pollen.

CONCLUSIONS

Our work on native biochemistry for breaching sporopollenin suggests new research directions in pollen aperture evolution and could aid efforts to analyze sporopollenin's composition, needed for application of this corrosion-resistant, but long-intractable material.

Neuromonitoring Using Motor and Somatosensory Evoked Potentials in Aortic Surgery

BACKGROUND

Motor evoked potentials (MEP) and somatosensory evoked potentials (SSEP) are established methods of neuromonitoring aimed at preventing paraplegia after descending or thoracoabdominal aortic repair. However, their predictive impact remains controversial. The aim of this study was to evaluate our single-center experience using this monitoring technique.

METHODS

Between 2009 and 2014, 78 patients (mean age 66 ± 12, 53% male) underwent either descending or thoracoabdominal aortic repairs. Of these, 60% had an aortic aneurysm, 30% dissection, and 10% other etiologies. Intraoperatively, MEPs and SSEPs were monitored and, if necessary, clinical parameters (blood pressure, hematocrit, oxygenation) were adjusted in response to neuromonitoring signals. This analysis is focused on the neurological outcome (paraplegia, stroke) after the use of intraoperative neuromonitoring.

RESULTS

Thirty-day mortality was 10 (12.8%). All patients with continuously stable signals or signals that returned after signal loss developed no spinal cord injury, whereas two out of six of the evaluable patients with signal loss (without return) during the procedure suffered from postoperative paraplegia (one transient and one permanent). Sensitivity and specificity of use of MEP and SSEP were 100% and 94.20% regarding paraplegia, respectively.

CONCLUSIONS

(1) Preservation of signals or return of signals is an excellent prognostic indicator for spinal cord function. (2) Intraoperative modifications in direct response to the signal change may have averted permanent paralysis in the patients with signal loss without neurologic injury. We have found MEP and SSEP neuromonitoring to be instrumental in the prevention of paraplegia. doi: 10.1111/jocs.12739 (J Card Surg 2016;31:383-389).

A unique presentation of immuno-osseous dysplasia

The immuno-osseous dysplasias are a rare group of conditions in which short-limbed dwarfism is associated with an immune defect. The best known of these is cartilage hair hypoplasia. However, several reports of other distinct conditions exist, which have been arbitrarily classified on the basis of the immune defect. We present a child with a previously unreported combination of immune and skeletal abnormalities in whom there was an unusual and distinctive skin appearance associated with defective cutaneous elastic fibers. These cutaneous features suggest a unifying link with other immuno-osseous dysplasia but the combination of immune and skeletal defects exposes weaknesses in the current method of classification.

North Carolina's TBI project ACCESS. Assuring coordinated care, education, and support for survivors of pediatric brain injury

Over the past three years, families, school staff, and healthcare personnel in our state have benefited from an innovative service delivery system designed to demonstrate that we can improve the lives of children with TBI. Project ACCESS has used hospital-based pediatric brain injury Community Transition Coordinators to identify, coordinate care, educate, support, and generally improve the lives of thousands of children with TBI. The project also uncovered a host of barriers that adversely affect the future of many of North Carolina's most vulnerable children. We hope that this article helps delineate the challenges faced by our state's healthcare and educational systems, and contributes to the adoption of a statewide model system of care for children with brain injury.

Crystal structures of 1-aminocyclopropane-1-carboxylate (ACC) synthase in complex with aminoethoxyvinylglycine and pyridoxal-5'-phosphate provide new insight into catalytic mechanisms

The structures of tomato 1-aminocyclopropane-1-carboxylate synthase (ACS) in complex with either cofactor pyridoxal-5'-phosphate (PLP) or both PLP and inhibitor aminoethoxyvinylglycine have been determined by x-ray crystallography. The structures showed good conservation of the catalytic residues, suggesting a similar catalytic mechanism for ACS and other PLP-dependent enzymes. However, the proximity of Tyr152 to the C-gamma-S bond of model substrate S-adenosylmethionine implies its critical role in the catalysis. The concerted accomplishment of catalysis by cofactor PLP and a protein residue, as proposed on the basis of the ACS structures in this paper, may represent a general scheme for the diversity of PLP-dependent catalyses. PLP-dependent enzymes have been categorized into four types of folds. A structural comparison revealed that a core fragment of ACS in fold type I is superimposable over tryptophan synthase beta subunit in fold type II and mouse ornithine decarboxylase in fold type III, thus suggesting a divergent evolution of PLP-dependent enzymes.

Toward development of an in vitro model of methamphetamine-induced dopamine nerve terminal toxicity

To develop an in vitro model of methamphetamine (METH)-induced dopamine (DA) neurotoxicity, striatal synaptosomes were incubated at 37 degrees C with METH for different periods of time (10-80 min), washed once, then tested for DA transporter function at 37 degrees C. METH produced time- and dose-dependent reductions in the V(max) of DA uptake, without producing any change in K(m). Incubation of synaptosomes with the DA neurotoxins 1-methyl-4-phenyl-pyridinium ion, 6-hydroxydopamine, and amphetamine under similar conditions produced comparable effects. In contrast, incubation with fenfluramine, a serotonin neurotoxin, did not. METH-induced decreases in DA uptake were selective, insofar as striatal glutamate uptake was unaffected. Various DA transporter blockers (cocaine, methylphenidate, and bupropion) afforded complete protection against METH-induced decreases in DA uptake, without producing any effect themselves. METH's effects were also temperature dependent, with greater decreases in DA uptake occurring at higher temperatures. Tests for residual drug revealed small amounts (0.1-0.2 microM) of remaining METH, but kinetic studies indicated that decreases in DA uptake were not likely to be due to METH acting as a competitive inhibitor of DA uptake. Decreases in the V(max) of DA uptake were not accompanied by decreases in B(max) of [(3)H]WIN 35,428 binding, possibly because there is no mechanism for removing damaged DA nerve endings from the in vitro preparation Collectively, these results give good support to the development of a valid in vitro model that may prove helpful for elucidating the mechanisms underlying METH-induced DA neurotoxicity.

Effects of 2-deoxy-D-glucose on methamphetamine-induced dopamine and serotonin neurotoxicity

The mechanisms underlying the neurotoxic actions of methamphetamine (METH) and related substituted amphetamines are unknown. Previous studies with 2-deoxyglucose (2-DG) have suggested that METH-induced neurotoxicity may involve exhaustion of intracellular energy stores. However, because 2-DG also produces hypothermic effects, and because METH's neurotoxic actions are highly susceptible to thermoregulatory influence, previous findings with 2-DG are difficult to interpret. The present studies were undertaken to further examine the influence of 2-DG's glucoprivic and thermic effects in the context of METH-induced dopamine (DA) and serotonin (5-HT) neurotoxicity. 2-DG protected against METH-induced DA neurotoxicity in both rats and mice. In both species, 2-DG, alone or in combination with METH, produced hypothermic effects. METH's toxic effects on brain 5-HT neurons were either unaffected or exacerbated by 2-DG, depending on species, brain region, and dose of METH tested. These results indicate that different mechanisms may underlie METH-induced DA and 5-HT neurotoxicity, and suggest that, as compared with 5-HT neurons, DA neurons are more susceptible to temperature influence, whereas 5-HT neurons are more vulnerable than DA neurons to metabolic compromise. Additional studies are needed to further assess the role of energy stores in the neurotoxic effects of METH and related drugs.

Fenfluramine-induced loss of serotonin transporters in baboon brain visualized with PET

The present study sought to determine whether or not Positron Emission Tomography (PET) with the newly developed positron emitting serotonin (5-HT) transporter ligand, (+)[11C]McN-5652, could be used to detect fenfluramine-induced 5-HT neurotoxicity in the brain of living primates (baboons). Six PET imaging studies were performed: three before treatment with fenfluramine (5 mg/kg, s.c., twice daily for 4 days) and three after (18, 45, and 81 days after treatment). The dose of fenfluramine used in this study (5 mg/kg) is known to produce 5-HT neurotoxicity in primates, and to be approximately two times higher than a dose of fenfluramine reported to produce small and inconsistent weight loss in baboons (2 mg/kg). Following fenfluramine treatment, marked lasting reductions in regional brain specific binding of (+)[11C]McN-5652 were found by means of PET. Findings with PET corresponded well with post-mortem neurochemical findings indicative of serotonergic neurotoxicity (lasting depletions of regional brain 5-HT, 5-HIAA, and 5-HT uptake sites). These results suggest that PET imaging with (+)[11C]McN-5652 will be useful for evaluating the 5-HT neurotoxic potential of fenfluramine and related drugs in living humans.

Amiodarone, thyroid hormone indexes, and altered thyroid function: long-term serial effects in patients with cardiac arrhythmias

Amiodarone, a drug that has electrophysiologic actions resembling those of hypothyroidism, increases serum levels of T4 and reverse T3 (rT3) and decreases T3. The drug's long-term effects on thyroid function are poorly defined. Serial thyroid hormone indexes in 76 patients given amiodarone for 6 to 32 months (mean +/- standard deviation 16 +/- 7) for arrhythmias were determined serially. Over this period, 68 patients (89%) remained euthyroid; hypothyroidism developed in 6 (8%) and hyperthyroidism developed in 2 (3%). In patients who remained euthyroid, thyroid hormone alterations attained steady-state values at 3 months: T4 increased 42% (p less than 0.01), rT3 increased 172% (p less than 0.01) and T3 decreased 16% (p less than 0.05), without significant effect on thyroid stimulating hormone. For the euthyroid patients, the 90% tolerance limits (95% confidence) over the follow-up period for T4 was 5 to 19 micrograms/dl (normal 4 to 12), for T3 36 to 163 ng/dl (normal 60 to 160), for rT3 22 to 131 ng/dl (normal 15 to 50) and for thyroid stimulating hormone 0 to 14 microU/ml (normal 1 to 6). The changes in hormone indexes in hyperthyroid or hypothyroid patients were unrelated to the cumulative dose or duration of drug therapy. The most reliable diagnostic indexes for amiodarone-induced altered thyroid state were: thyroid stimulating hormone level over 20 microU for hypothyroidism and T4 over 20 ng/dl or high T3 over 200 ng/dl for hyperthyroidism. All levels were within the 90% tolerance limits derived for these hormones from patients remaining euthyroid on amiodarone long-term.(ABSTRACT TRUNCATED AT 250 WORDS)

Central hypoventilation during quiet sleep in two infants

Expired ventilation (VE), tidal volume (VT), frequency (f), and alveolar PCO2 (PACO2) were examined in six normal infants at 41 to 52 weeks post-conceptional age and in two infants who were apneic at birth. Their response to breathing 5% carbon dioxide in air and to 100% oxygen in quiet sleep were compared to those in rapid eye movement (REM) sleep. VE in normal infants was 259 ml/kg/min in REM and 200.2 ml/kg/min in quiet sleep with the difference being due to decreased carbon dioxide production and to decreased dead space. VE increased 34.4 ml/kg/min/mm Hg of PCO2 elevation with 5% carbon dioxide breathing during REM and was not significantly different during quiet sleep. During oxygen breathing VE fell by 32.7% at 30 seconds before increasing again. In the affected infants, VE and PACO2 during REM at 1 and 4 months were normal. At 1 month, during quiet sleep, each infant became apneic and PACO2 rose 9 and 8 mm Hg/min respectively. At this time mechanical ventilation was begun. At 4 months, during quiet sleep, VE was 0.064 and 0.063 ml/kg/min at PACO2 of 66 mm Hg in each infant. The change was due entirely to a decrease in VT to 2.3 and 2.5 ml/kg. At this time 5% carbon dioxide breathing given during normal ventilation in REM produced an abrupt fall in VT to 2.0 and 2.2 ml/kg with no change in frequency. Oxygen breathing during REM at one month had no effect but at 4 months produced apnea requiring mechanical ventilation after one minute. The findings suggest that the ventilatory response to carbon dioxide is (1) important in initiation of extrauterine ventilation and (2) in sustaining ventilation particularly in quiet sleep. It is not necessary in sustaining ventilation awake or in REM sleep and it represents a balance between the stimulatory and depressant effects of carbon dioxide on the central nervous system.