The role of intraoperative monitoring of oculomotor and trochlear nuclei -safe entry zone to tegmental lesions.

OBJECTIVE: A safe entry zone to tegmental lesions was identified based on intraoperative electrophysiological findings, the compound muscle action potentials (CMAP) from the extraocular muscles, and anatomic considerations. This entry zone is bordered caudally by the intramesencephalic path of the trochlear, laterally by the spinothalamic tract, and rostrally by the caudal margin of the brachium of the superior colliculus. METHODS: Four intrinsic midbrain lesions were operated upon via the safe entry zone using the infratentorial paramedian supracerebellar approach. All lesions involved the tegmentum and included an anaplastic astrocytoma, a metastatic brain tumor, a radiation necrosis, and a cavernous angioma. CMAP were bilaterally monitored from the inferior recti (for oculomotor function) and superior oblique (for trochlear nerve function) muscles. RESULTS: In three of four cases, CMAP related to the oculomotor nerve were obtained upon stimulation at the cavity wall after removal of the tumor. Stimulation at the surface of the quadrigeminal plate, however, did not cause any CMAP response. Using this monitoring as an indicator, the lesions were totally removed. CONCLUSIONS: In the surgery of tegmental lesions, CMAP monitoring from extraocular muscles is particularly helpful to prevent damage to crucial neural structures during removal of intrinsic lesions, but less so to select the site of the medullary incision. The approach via the lateral part of the colliculi is considered to be a safe route to approach the tegmental lesions.     

A new index for evaluating horizontal skeletal discrepancies and predicting treatment outcomes

The cephalometric measurement known as Wits appraisal (AOBO) was studied to determine its importance in diagnosis, treatment, and prediction of treatment success. The Wits appraisal is used primarily to identify unreliable ANB values (those that do not accurately reflect the degree of horizontal jaw discrepancy, ie, those that differ greatly from the AOBO value). Therefore, differences between AOBO and ANB also were evaluated. Because neither measurement alone can assess jaw discrepancies with total accuracy, they were combined, plotted on a scattergram, and divided into equal zones to create a new index of horizontal skeletal discrepancies and treatment predictability. Pretreatment values correspond to treatment difficulty, and posttreatment values correspond to the effectiveness of treatment. Treatment time for each zone also was evaluated. We were able to draw several conclusions from this study. First, combining AOBO and ANB values results in a more accurate measurement of treatment difficulty. These combined values also can be used to predict both treatment time and the success of treatment for horizontal discrepancies. Second, the AOBO value predicts variations in treatment time at each ANB value. Finally, adding ANB and AOBO values and then dividing the total yields zones that represent statistically significant differences in treatment times and percentages of success. The zones also correlate with the difference between AOBO and ANB measurements.     

Two approaches to social support in smoking cessation: Commodity model and nondirective support

The commodity model of social support and features of Nondirective Support may clarify varied results of support interventions for smoking cessation. A commodity model views social support as attractive in and of itself and as an alternative to high-risk choices such as smoking. If such support is easily accessible, a would-be quitter is less likely to choose to smoke. Consistent with the commodity model, social support interventions tend to be effective as long as support remains available, but they lose their effects when support is terminated. From a second approach, Nondirective Support entails accepting recipients' goals, cooperating without taking control, and validating recipients' feelings. In contrast, Directive Support entails taking control and telling recipients what to do and feel. Review of support interventions indicates the value of the continued availability of support suggested by the commodity model and of Nondirective Support's flexibility and responsiveness to the person.     

IDEC-131 (Anti-CD154), Sirolimus and Donor-Specific Transfusion Facilitate Operational Tolerance in Non-Human Primates

CD154-specific antibody therapy prevents allograft rejection in many experimental transplant models. However, initial clinical transplant trials with anti-CD154 have been disappointing suggesting the need for as of yet undetermined adjuvant therapy. In rodents, donor antigen (e.g., a donor blood transfusion), or mTOR inhibition (e.g., sirolimus), enhances anti-CD154's efficacy. We performed renal transplants in major histocompatibility complex-(MHC) mismatched rhesus monkeys and treated recipients with combinations of the CD154-specific antibody IDEC-131, and/or sirolimus, and/or a pre-transplant donor-specific transfusion (DST). Therapy was withdrawn after 3 months. Triple therapy prevented rejection during therapy in all animals and led to operational tolerance in three of five animals including donor-specific skin graft acceptance in the two animals tested. IDEC-131, sirolimus and DST are highly effective in preventing renal allograft rejection in primates. This apparently clinically applicable regimen is promising for human renal transplant trials.     

Distinct Pharmacologic Properties of Neuromuscular Blocking Agents on Human Neuronal Nicotinic Acetylcholine Receptors: A Possible Explanation for the Train-of-four Fade

Background: Nondepolarizing neuromuscular blocking agents (NMBAs) are extensively used in the practice of anesthesia and intensive care medicine. Their primary site of action is at the postsynaptic nicotinic acetylcholine receptor (nAChR) in the neuromuscular junction, but their action on neuronal nAChRs have not been fully evaluated. Furthermore, observed adverse effects of nondepolarizing NMBAs might originate from an interaction with neuronal nAChRs. The aim of this study was to examine the effect of clinically used nondepolarizing NMBAs on muscle and neuronal nAChR subtypes.

Methods: Xenopus laevis oocytes were injected with messenger RNA encoding for the subunits included in the human [alpha]1[beta]1[varepsilon][delta], [alpha]3[beta]2, [alpha]3[beta]4, [alpha]4[beta]2, and [alpha]7 nAChR subtypes. The interactions between each of these nAChR subtypes and atracurium, cisatracurium, d-tubocurarine, mivacurium, pancuronium, rocuronium, and vecuronium were studied using an eight-channel two-electrode voltage clamp setup. Responses were measured as peak current and net charge.

Results: All nondepolarizing NMBAs inhibited both muscle and neuronal nAChRs. The neuronal nAChRs were reversibly and concentration-dependently inhibited in the low micromolar range. The mechanism (i.e., competitive vs. noncompetitive) of the block at the neuronal nAChRs was dependent both on subtype and the NMBA tested. The authors did not observe activation of the nAChR subtypes by any of the NMBAs tested.     

Interobserver and interstudy variability of myocardial blood flow and flow-reserve measurements with nitrogen 13 ammonia-labeled positron emission tomography

Background  

Experimental studies have shown that positron emission tomography (PET) with ¹³N-labeled ammonia provides accurate quantification of regional myocardial blood flow (MBF) under rest and stress conditions. To establish the clinical utility of this method, the interobserver variability and the temporal variability of serial measurements of blood flow and coronary flow reserve (CFR) must be known. This study investigated the interobserver and temporal reproducibility of ¹³N-labeled PET for measurement of MBF and CFR.