Update on myelin imaging in neurological syndromes.

PURPOSE OF REVIEW: Myelin water imaging (MWI) is generally regarded as the most rigorous approach for noninvasive, in-vivo measurement of myelin content, which has been histopathologically validated. As such, it has been increasingly applied to neurological diseases with white matter involvement, especially those affecting myelin. This review provides an overview of the most recent research applying MWI in neurological syndromes. RECENT FINDINGS: Myelin water imaging has been applied in neurological syndromes including multiple sclerosis, Alzheimer's disease, Huntington's disease, traumatic brain injury, Parkinson's disease, cerebral small vessel disease, leukodystrophies and HIV. These syndromes generally showed alterations observable with MWI, with decreased myelin content tending to correlate with lower cognitive scores and worse clinical presentation. MWI has also been correlated with genetic variation in the APOE and PLP1 genes, demonstrating genetic factors related to myelin health. SUMMARY: MWI can detect and quantify changes not observable with conventional imaging, thereby providing insight into the pathophysiology and disease mechanisms of a diverse range of neurological syndromes.

Research at a Distance: Replicating Semantic Differentiation Effects Using Remote Data Collection With Children Participants.

Remote data collection procedures can strengthen developmental science by addressing current limitations to in-person data collection and helping recruit more diverse and larger samples of participants. Thus, remote data collection opens an opportunity for more equitable and more replicable developmental science. However, it remains an open question whether remote data collection procedures with children participants produce results comparable to those obtained using in-person data collection. This knowledge is critical to integrate results across studies using different data collection procedures. We developed novel web-based versions of two tasks that have been used in prior work with 4-6-year-old children and recruited children who were participating in a virtual enrichment program. We report the first successful remote replication of two key experimental effects that speak to the emergence of structured semantic representations (N = 52) and their role in inferential reasoning (N = 40). We discuss the implications of these findings for using remote data collection with children participants, for maintaining research collaborations with community settings, and for strengthening methodological practices in developmental science.

Angioedema and Dual Nurse Flight Crew Cricothyrotomy After Envenomation by a Severed Rattlesnake Head.

Crotalid envenomation may result in airway compromise from angioedema, anaphylaxis, or an anaphylactoid reaction. A 57-year-old man was transported by helicopter to the emergency department (ED) after a bite to his hand from a severed rattlesnake head. He rapidly developed facial and oropharyngeal edema that did not respond to standard treatment. After 2 unsuccessful attempts at intubation, the dual flight nurse team performed a cricothyrotomy. They notified the ED team en route, and antivenom was prepared before arrival. Angioedema was suspected because there was no concomitant urticaria, bronchoconstriction, or persistent hypotension. Edema and ecchymosis of the affected extremity were mild. Severe coagulopathy ensued, which was treated with bolus doses of antivenom and continuous infusion. This case report is significant for several reasons. It is the first detailing a prehospital cricothyrotomy performed by flight crew nurses for life-threatening airway edema caused by snakebite envenomation. In-flight notification enabled the ED staff to prepare and administer antivenom immediately after arrival. Despite the use of antivenom in bolus dosing, crotalid envenomation may be complicated by persistent or recurring coagulopathy, and continuous antivenom infusion may be useful. Finally, it highlights the danger of snakebite envenomation even after the death and decapitation of a snake.

Mass Air Medical Repatriation of Coronavirus Disease 2019 Patients.

Recent coronavirus disease 2019 (COVID-19) events have presented challenges to health care systems worldwide. Air medical movement of individuals with potential infectious disease poses unique challenges and threats to crews and receiving personnel. The US Department of Health and Human Services air medical evacuation teams of the National Disaster Medical System directly supported 39 flights, moving over 2,000 individuals. Infection control precautions focused on source and engineering controls, personal protective equipment, safe work practices to limit contamination, and containment of the area of potential contamination. Source control to limit transmission distance was used by requiring all passengers to wear masks (surgical masks for persons under investigation and N95 for known positives). Engineering controls used plastic sheeting to segregate and treat patients who developed symptoms while airborne. Crews used Tyvek (Dupont Richmond, VA) suits with booties and a hood, a double layer of gloves, and either a powered air-purifying respirator or an N95 mask with a face shield. For those outside the 6-ft range, an N95 mask and gloves were worn. Safe work practices were used, which included mandatory aircraft surface decontamination, airflow exchanges, and designated lavatories. Although most patients transported were stable, to the best of our knowledge, this represents the largest repatriation of potentially contagious patients in history without infection of any transporting US Department of Health and Human Services air medical evacuation crews.

Delayed cardiac perforation by defibrillator lead placed in the right ventricular outflow tract resulting in massive pericardial effusion.

A 76-year-old man received a dual-chamber implantable cardioverter defibrillator (ICD), with the defibrillator lead positioned within the right ventricular outflow tract. The lead parameters at the time of implantation were satisfactory and the post-procedure chest X-ray showed the leads were in place. The patient was cardioverted from atrial fibrillation during defibrillation threshold testing and commenced on anticoagulation immediately. One month post implantation, he experienced multiple ventricular tachycardia episodes all successfully treated with antitachycardia pacing and shocks by his ICD, but he fell and hit his chest against a hard surface during one of these attacks. He developed a massive pericardial effusion and computed tomography confirmed cardiac perforation by the defibrillator lead. Pericardiocentesis was performed and the defibrillator lead replaced with a different model positioned at the right ventricular apex. The patient made an uneventful recovery. The management and avoidance of delayed cardiac perforation by transvenous leads were discussed.

Activation patterns during selective pacing of the left ventricle can be characterized using noninvasive electrocardiographic imaging.

BACKGROUND: Noncontact endocardial mapping allows accurate beat-to-beat reconstruction of the reentrant pathway of ventricular tachycardia and improves outcomes after ablation. Several studies support electrocardiographic imaging (ECGI) as a means of noninvasively outlining epicardial activation despite constraints of internal geometry. However, few have explored its clinical application. This study aims to evaluate ECGI during selective left ventricular (LV) pacing, relative to an invasive approach. METHODS: Multisite pacing was performed within the left ventricles of 3 patients undergoing invasive procedures. Simultaneous recording of endocardial potentials using a noncontact multielectrode array and body surface potentials (BSP) using an 80-electrode torso vest was performed. A total of 16 recordings were made. The inverse solution was applied to BSP to reconstruct epicardial activation. Single-paced beats from real and virtual electrograms were used to construct 3-dimensional isochronal and isopotential maps. Endocardial and epicardial data were then superimposed onto a single geometry to allow quantitative comparison of activation foci. RESULTS: Good correlation was observed between endocardial activation patterns and those reconstructed from BSP using ECGI. This was repeatedly demonstrated in all LV regions except for the septum (3 recordings). Epicardial isochronal maps were able to locate early and late activation to mean distances of 13.8 +/- 4.7 and 12.5 +/- 3.7 mm from endocardial data. Isopotential maps localized pacing sites with comparable accuracy (14 +/- 5.3 mm). CONCLUSIONS: Body surface potentials and reconstructed epicardial activation patterns during LV pacing correlate well with endocardial data acquired invasively. The exception was during pacing of the septum. Although early results are encouraging, further quantitative data are required to fully validate and apply this noninvasive tool in the clinical arena.

In vivo multiecho T2 relaxation measurements using variable TR to decrease scan time.

Multiecho T2 relaxation measurements to determine geometric mean T2 (GMT2) and myelin water fraction (MWF) are lengthy, resulting in increased motion artefacts from patient discomfort and reduced patient compliance. The goal of this study was to shorten the acquisition time for multiecho T2 measurements without affecting T1 weighting by varying TR across k-space. Six phantoms and 10 healthy volunteers were imaged with both a constant TR and a variable TR multiecho T2 sequence. T1 weighting was determined by TR at the center of k-space; for variable TR measurement, TR was shortened linearly from the center to the edges of k-space. Phantoms showed excellent agreement for proton density and GMT2 between constant and variable TR measurements. No significant differences were found in proton density or MWF for any of the brain structures between the two measurements. The average GMT2 over all structures between the two experiments was not significantly different. In summary, with the variable TR approach, scan time was reduced by >20%, with minimal loss of image resolution and no significant affect on proton density, MWF or GMT2.

ST segment elevation in lead aVR during exercise testing is associated with LAD stenosis.

PURPOSE: To evaluate, in patients with chest pain, the diagnostic value of ST elevation (STE) in lead aVR during stress testing prior to (99m) Tc-sestamibi scanning correlating ischaemic territory with angiographic findings. METHODS: Consecutive patients attending for (99m) Tc-sestamibi myocardial perfusion imaging (MPI) completed a treadmill protocol. Peak exercise ECGs were coded. STE >or=0.05 mV in lead aVR was considered significant. Gated perfusion images and findings at angiography were assessed. RESULTS: STE in lead aVR occurred in 25% (138/557) of the patients. More patients with STE in aVR had a reversible defect on imaging compared with those who had no STE in aVR (41%, 56/138 vs 27%, 114/419, p=0.003). Defects indicating a left anterior descending artery (LAD) culprit lesion were more common in the STE in aVR group (20%, 27/138 vs 9%, 39/419, p=0.001). There was a trend towards coronary artery stenosis (>70%) in a double vessel distribution involving the LAD in those patients who had STE in aVR compared with those who did not (22%, 8/37 vs 5%, 4/77, p=0.06). Logistic regression analysis demonstrated that STE in aVR (OR 1.36, p=0.233) is not an independent predictor of inducible abnormality when adjusted for STD >0.1 mV (OR 1.69, p=0.026). However, using anterior wall defect as an end-point, STE in aVR (OR 2.77, p=0.008) was a predictor even after adjustment for STD (OR 1.43, p=0.281). CONCLUSION: STE in lead aVR during exercise does not diagnose more inducible abnormalities than STD alone. However, unlike STD, which is not predictive of a territory of ischaemia, STE in aVR may indicate an anterior wall defect.