Longitudinal changes in global structural brain connectivity and cognitive performance in former hospitalized COVID-19 survivors: an exploratory study.

BACKGROUND: Long-term sequelae of COVID-19 can result in reduced functionality of the central nervous system and substandard quality of life. Gaining insight into the recovery trajectory of admitted COVID-19 patients on their cognitive performance and global structural brain connectivity may allow a better understanding of the diseases' relevance. OBJECTIVES: To assess whole-brain structural connectivity in former non-intensive-care unit (ICU)- and ICU-admitted COVID-19 survivors over 2 months following hospital discharge and correlate structural connectivity measures to cognitive performance. METHODS: Participants underwent Magnetic Resonance Imaging brain scans and a cognitive test battery after hospital discharge to evaluate structural connectivity and cognitive performance. Multilevel models were constructed for each graph measure and cognitive test, assessing the groups' influence, time since discharge, and interactions. Linear regression models estimated whether the graph measurements affected cognitive measures and whether they differed between ICU and non-ICU patients. RESULTS: Six former ICU and six non-ICU patients completed the study. Across the various graph measures, the characteristic path length decreased over time (ß = 0.97, p = 0.006). We detected no group-level effects (ß = 1.07, p = 0.442) nor interaction effects (ß = 1.02, p = 0.220). Cognitive performance improved for both non-ICU and ICU COVID-19 survivors on four out of seven cognitive tests 2 months later (p < 0.05). CONCLUSION: Adverse effects of COVID-19 on brain functioning and structure abate over time. These results should be supported by future research including larger sample sizes, matched control groups of healthy non-infected individuals, and more extended follow-up periods.

The optimized combination of aCompCor and ICA-AROMA to reduce motion and physiologic noise in task fMRI data.

One of the main challenges in fMRI processing is filtering the task BOLD signals from the noise. Independent component analysis with automatic removal of motion artifacts (ICA-AROMA) reduces motion artifacts by identifying ICA noise components based on their location at the brain edges and cerebrospinal fluid (CSF), high frequency content and correlation with motion regressors. In anatomical component correction (aCompCor), physiological noise regressors extracted from CSF were regressed out from the fMRI time series. In this study, we compared three methods to combine aCompCor and ICA-AROMA denoising in one denoising step. In the first analysis, we regressed the temporal signals of the ICA components identified as noise by ICA-AROMA together with the noise signals determined by aCompCor from the fMRI signals. For the second and third analyses, the correlation between the temporal signals of the ICA components and the aCompCor noise signals was used as an additional criterion to identify the noise components. In the second analysis, the temporal signals of the ICA components classified as noise were regressed from the fMRI signals. In the third analysis, the noise components were removed. To compare the denoising strategies, we examined the fractional amplitude of low-frequency fluctuations (fALFF) and the overlap between the contrast maps. Our results revealed that including the aCompCor noise signals as regressors in ICA-AROMA resulted in more correctly identified noise components, higher fALFF values, and larger activation maps. Moreover, combining the temporal signals of the noise components identified by ICA-AROMA with the aCompCor signals in a noise regression matrix resulted in deactivations. These results suggest that using the correlation between the ICA component temporal signals and the aCompCor signals as noise identification criteria in ICA-AROMA is the best approach for combining both denoising methods.

Spinal cord stimulation modulates cerebral function: an fMRI study.

INTRODUCTION: Although spinal cord stimulation (SCS) is widely used for chronic neuropathic pain after failed spinal surgery, little is known about the underlying physiological mechanisms. This study aims to investigate the neural substrate underlying short-term (30 s) SCS by means of functional magnetic resonance imaging in 20 patients with failed back surgery syndrome (FBSS). METHODS: Twenty patients with FBSS, treated with externalized SCS, participated in a blocked functional magnetic resonance imaging design with stimulation and rest phases of 30 s each, repeated eight times in a row. During scanning, patients rated pain intensity over time using an 11-point numerical rating scale with verbal anchors (0 = no pain at all to 10 = worst pain imaginable) by pushing buttons (left hand, lesser pain; right hand, more pain). This scale was back projected to the patients on a flat screen allowing them to manually direct the pain indicator. To increase the signal-to-noise ratio, the 8-min block measurements were repeated three times. RESULTS: Marked deactivation of the bilateral medial thalamus and its connections to the rostral and caudal cingulate cortex and the insula was found; the study also showed immediate pain relief obtained by short-term SCS correlated negatively with activity in the inferior olivary nucleus, the cerebellum, and the rostral anterior cingulate cortex. CONCLUSIONS: Results indicate the key role of the medial thalamus as a mediator and the involvement of a corticocerebellar network implicating the modulation and regulation of averse and negative affect related to pain. The observation of a deactivation of the ipsilateral antero-medial thalamus might be used as a region of interest for further response SCS studies.

The effect of one left-sided dorsolateral prefrontal sham-controlled HF-rTMS session on approach and withdrawal related emotional neuronal processes.

OBJECTIVE: Although repetitive Transcranial Magnetic Stimulation (rTMS) is frequently used to examine emotional changes in healthy volunteers, it remains largely unknown how rTMS is able to influence emotion. METHODS: In this sham-controlled, single-blind crossover study using fMRI, we examined in 20 right-handed healthy females whether a single high frequency (HF)-rTMS session applied to the left dorsolateral prefrontal cortex could influence emotional processing while focussing on blocks of positively and negatively valenced baby faces. RESULTS: While positive information was being processed, we observed after one active HF-rTMS session enhanced neuronal activity in the left superior frontal cortex and right inferior parietal cortex. After sham HF-rTMS, we found significant decreases in neuronal activity in the left superior frontal cortex, the left inferior prefrontal cortex, as well as in the right posterior cingulate gyrus. When negative information was processed, one active stimulation attenuated neuronal activity in the right insula only. CONCLUSIONS: Our findings suggest that during the processing of positive information one active session enhanced the ability to empathize with the depicted emotional stimuli, while during the processing of negative information it resulted in decreased psychophysiological reactions. SIGNIFICANCE: These results provide new information on the working mechanism of left-sided HF-rTMS.

Right prefrontal HF-rTMS attenuates right amygdala processing of negatively valenced emotional stimuli in healthy females.

Repetitive transcranial magnetic stimulation (rTMS) studies investigating brain imaging correlates of emotion modulation in healthy volunteers can improve our understanding of the 'affective' impact of this application. In this fMRI study, we focused on lateralized amygdala functioning when processing salient emotional visual stimuli after one high-frequency (HF)-rTMS session. In a 'uniform sample' of 20 right-handed, non-depressed, healthy female subjects we examined whether one HF-rTMS session applied to the left (n=10) or right (n=10) dorsolateral prefrontal cortex (DLPFC) would influence amygdala responses to positively and negatively valenced baby faces. Subjects were given no other instructions than to focus on the emotion the visual stimuli elicited during scanning. One HF-rTMS session did not result in a conscious mood change. Whereas one left-sided HF-rTMS session did not affect amygdala processing of the positive or negative stimuli, after a single right-sided HF-rTMS session we found a significant right amygdala activity attenuation during the processing of negatively valenced baby faces. This finding provides additional evidence supporting the role of the right anterior hemisphere in the processing of negative emotional information, and increases our understanding of HF-rTMS treatment effects in mental disorders.

Reduced left subgenual anterior cingulate cortical activity during withdrawal-related emotions in melancholic depressed female patients.

BACKGROUND: Research regarding the neurocircuitry in mood disorders suggests an important role for affective information processing of the subgenual part of the anterior cingulate cortex (Cg25: Brodmann area 25). OBJECTIVE: In this study, we focused on Cg25 neuronal responses in depressed females using a paradigm in which emotions are elicited without explicit cognitive control, relying on the salient nature of the mood inducing stimuli eliciting approach-related emotions (like happiness) or withdrawal-related emotions (like disgust). METHODS: Twelve treatment-resistant melancholic depressed women and 12 healthy female control subjects were asked to passively view blocks of emotionally valenced baby faces while undergoing functional magnetic resonance imaging (fMRI). RESULTS: Compared to the healthy females, the depressed patients displayed significantly higher bilateral Cg25 neuronal activities in both emotional conditions. In melancholically depressed women, we found significantly less left-sided than right-sided Cg25 neuronal activity during the withdrawal-related emotions, while right-sided Cg25 activity was comparable for both emotional responses. CONCLUSIONS: Our results indicate that in depressed women the left Cg25 modulates intense visceral emotional responses to aversive visual stimuli. This could help explain why the left Cg25 provides a valid target region for antidepressant treatment strategies in unipolar melancholic depression.

Dealing with pregnancy in radiology: a thin line between science, social and regulatory aspects.

The participation of pregnant women in radiology can be an emotional experience. The word "radiation" understandably invokes fear and uncertainty. Irradiation of a foetus should be avoided whenever possible. However, radiological examinations of pregnant women are often justified and unintended exposures do occur. Also pregnant radiology staff may remain working in the department. Lack of knowledge about the effects of both ionising (X-rays) and non-ionising (MRI) radiation is responsible for anxiety of patients and workers. If foetal exposures occur, they must be quantitatively evaluated and the risk put into perspective. This paper is intended to inform radiology managers, radiologists, technologists and referring clinicians in their management with pregnant patients and co-workers. The paper describes conceptus doses for both patient and worker that are associated with radiology practice, reviews the risks and effects of in utero irradiation, and discusses current national policies, international guidelines and practical aspects.

Demonstration of tissue alterations by ultrasonography, magnetic resonance imaging and spectroscopy, and histology in breast cancer patients without lymphedema after axillary node dissection.

Estimates of the incidence of arm swelling after axillary lymph node dissection for breast cancer range from 10 to 37%. Yet the subjective sensation of edema is described in at least 54% of patients. The purpose of this research was to examine the structural changes occurring in the subcutaneous tissue that might explain these subjective complaints using multiple imaging modalities. Two female cadavers with unilateral breast amputation and axillary dissection were studied. The dermal and subcutaneous layers of both arms were visualized with high frequency ultrasonography, and magnetic resonance imaging and spectroscopy (MRS), and tissue biopsies were taken for histological evaluation. On the operated side, ultrasound imaging showed a hyperechogenic subcutis and the fat-to-water relationship in adipose cells was higher as measured by MRS. Dissection of the arms revealed structural adipose tissue changes, which were confirmed by microscopic evaluation.

Choice of the regularization parameter for perfusion quantification with MRI.

Truncated singular value decomposition (TSVD) is an effective method for the deconvolution of dynamic contrast enhanced (DCE) MRI. Two robust methods for the selection of the truncation threshold on a pixel-by-pixel basis--generalized cross validation (GCV) and the L-curve criterion (LCC)--were optimized and compared to paradigms in the literature. GCV and LCC were found to perform optimally when applied with a smooth version of TSVD, known as standard form Tikhonov regularization (SFTR). The methods lead to improvements in the estimate of the residue function and of its maximum, and converge properly with SNR. The oscillations typically observed in the solution vanish entirely, and perfusion is more accurately estimated at small mean transit times. This results in improved image contrast and increased sensitivity to perfusion abnormalities, at the cost of 1-2 min in calculation time and hyperintense clusters in the image. Preliminary experience with clinical data suggests that the latter problem can be resolved using spatial continuity and/or hybrid thresholding methods. In the simulations GCV and LCC are equivalent in terms of performance, but GCV thresholding is faster.