Apathy in depression: An arterial spin labeling perfusion MRI study

INTRODUCTION

Apathy, as defined as a deficit in goal-directed behaviors, is a critical clinical dimension in depression associated with chronic impairment. Little is known about its cerebral perfusion specificities in depression. To explore neurovascular mechanisms underpinning apathy in depression by pseudo-continuous arterial spin labeling (pCASL) magnetic resonance imaging (MRI).

METHODS

Perfusion imaging analysis was performed on 90 depressed patients included in a prospective study between November 2014 and February 2017. Imaging data included anatomical 3D T1-weighted and perfusion pCASL sequences. A multiple regression analysis relating the quantified cerebral blood flow (CBF) in different regions of interest defined from the FreeSurfer atlas, to the Apathy Evaluation Scale (AES) total score was conducted.

RESULTS

After confound adjustment (demographics, disease and clinical characteristics) and correction for multiple comparisons, we observed a strong negative relationship between the CBF in the left anterior cingulate cortex (ACC) and the AES score (standardized beta = -0.74, corrected p value = 0.0008).

CONCLUSION

Our results emphasized the left ACC as a key region involved in apathy severity in a population of depressed participants. Perfusion correlates of apathy in depression evidenced in this study may contribute to characterize different phenotypes of depression.

Postural instability and gait disorders after subthalamic nucleus deep brain stimulation in Parkinson's disease: a PET study

INTRODUCTION

Patients with Parkinson's disease sometimes report postural instability and gait disorders (PIGD) after subthalamic nucleus deep brain stimulation (STN-DBS). Whether this is the direct consequence of DBS or the result of natural disease progression is still subject to debate.

OBJECTIVE

To compare changes in brain metabolism during STN-DBS between patients with and without PIGD after surgery.

METHODS

We extracted consecutive patients from a database where all Rennes Hospital patients undergoing STN-DBS are registered, with regular prospective updates of their clinical data. Patients were divided into two groups (PIGD and No PIGD) according to changes after surgery, as measured with a composite score based on the selected Unified Parkinson's Disease Rating Scale items. All patients underwent positron emission tomography with ¹⁸[F]-fluorodeoxyglucose 3 months before and after surgery. We ran an ANOVA with two factors (group: PIGD vs. No PIGD; and phase: preoperative vs. postoperative) on SPM8 to compare changes in brain metabolism between the two groups.

RESULTS

Participants were 56 patients, including 10 in the PIGD group. The two groups had similar baseline (i.e., before surgery) characteristics. We found two clusters of increased metabolism in the PIGD group relative to the No PIGD group: dorsal midbrain/pons, including locomotor mesencephalic region and reticular pontine formation, and right motor cerebellum.

CONCLUSION

We found different metabolic changes during DBS-STN among patients with PIGD, concerning brain regions that are already known to be involved in gait disorders in Parkinson's disease, suggesting that DBS is responsible for the appearance of PIGD.

Brain Perfusion Imaging in Neonates: An Overview

The development of cognitive function in children has been related to a regional metabolic increase and an increase in regional brain perfusion. Moreover, brain perfusion plays an important role in the pathogenesis of brain damage in high-risk neonates, both preterm and full-term asphyxiated infants. In this article, we will review and discuss several existing imaging techniques for assessing neonatal brain perfusion.

Main applications of hybrid PET-MRI contrast agents: a review

In medical imaging, the continuous quest to improve diagnostic performance and optimize treatment strategies has led to the use of combined imaging modalities. Positron emission tomography (PET) and computed tomography (CT) is a hybrid imaging existing already for many years. The high spatial and contrast resolution of magnetic resonance imaging (MRI) and the high sensitivity and molecular information from PET imaging are leading to the development of this new hybrid imaging along with hybrid contrast agents. To create a hybrid contrast agent for PET-MRI device, a PET radiotracer needs to be combined with an MRI contrast agent. The most common approach is to add a radioactive isotope to the surface of a small superparamagnetic iron oxide (SPIO) particle. The resulting agents offer a wide range of applications, such as pH variation monitoring, non-invasive angiography and early imaging diagnosis of atherosclerosis. Oncology is the most promising field with the detection of sentinel lymph nodes and the targeting of tumor neoangiogenesis. Oncology and cardiovascular imaging are thus major areas of development for hybrid PET-MRI imaging systems and hybrid contrast agents. The aim is to combine high spatial resolution, high sensitivity, morphological and functional information. Future prospects include the use of specific antibodies and hybrid multimodal PET-MRI-ultrasound-fluorescence imaging with the potential to provide overall pre-, intra- and postoperative patient care.

Repetitive transcranial magnetic stimulation over the orbitofrontal cortex for obsessive-compulsive disorder: a double-blind, crossover study

This pilot study was designed to assess the efficacy of low-frequency repetitive transcranial magnetic stimulation (rTMS) over the right orbitofrontal cortex (OFC) by means of a double-cone coil in patients suffering from obsessive-compulsive disorder. We hypothesized that low-frequency stimulation of the OFC would lead to a reduction in clinical symptoms, as measured on the Yale-Brown Obsessive Compulsive Scale (Y-BOCS). A randomized, double-blind, crossover design was implemented with two 1-week treatment periods (active stimulation versus sham stimulation) separated by a 1-month washout period. Concomitantly, a subgroup of patients underwent a positron emission tomography (PET) scan after each stimulation sequence. Statistical analyses compared the Y-BOCS scores at the end of each period. At day 7, we observed a significant decrease from baseline in the Y-BOCS scores, after both active (P<0.01) and sham stimulation (P=0.02). This decrease tended to be larger after active stimulation than after sham stimulation: -6 (-29, 0) points versus -2 (-20, 4) points (P=0.07). Active versus sham PET scan contrasts showed that stimulation was related to a bilateral decrease in the metabolism of the OFC. The OFC should definitely be regarded as a key neuroanatomical target for rTMS, as it is easier to reach than either the striatum or the subthalamic nucleus, structures favored in neurosurgical approaches.

[Apathy neural bases in neurodegenerative disorders]

Apathy is widely recognized as a lack of motivation, which expresses through the cognitive, behavioral and emotional dimensions of living. It is described within several neuropsychiatric syndromes such as degenerative disorder and is associated with poorer outcomes. In order to better understand the underpinnings of apathy and to develop specific treatment strategies, much research has been conducted to define its neural bases. In the present review, perfusion, metabolic, pathologic and functional results of apathy neural bases in Alzheimer's and Parkinson's diseases are displayed. Methods and strategies to control for confounding factors such as depression, cognitive impairments and other behavioral disorders are described. Results are not strictly identical between disorders and even within disorders. Variation of methods employed on assessment tools and control for confounding factors such as cognitive disorders, depression, other behavioral disorders and medical treatment is thought to be the main reason for this discrepancy. However, it seems that the inferior prefrontal cortex, especially the orbitofrontal cortex, the lateral prefrontal cortex and the anterior cingulate are of particular interest. The second part of the review discusses the literature in these three areas in conditional learning essentially via the reward characteristic encoding, auto-initiated and perseverance behaviors and emotional experience and its regulation.

Subthalamic nucleus stimulation in Parkinson disease induces apathy: a PET study

OBJECTIVE

Apathy may be induced by subthalamic nucleus deep brain stimulation (STN-DBS) in Parkinson disease (PD). We therefore wished to test the hypothesis that apathy induced by STN-DBS correlates with changes in glucose metabolism, using (18)FDG-PET.

METHODS

Twelve patients with PD were assessed 3 months before (M-3) and 3 months after (M+3) STN-DBS with (18)FDG-PET and the Apathy Evaluation Scale.

RESULTS

Apathy had significantly worsened at M+3 after STN-DBS. Positive correlations were observed between this variation in apathy scores and changes in glucose metabolism, especially in the right frontal middle gyrus (Brodmann area [BA] 10) and right inferior frontal gyrus (BA 46 and BA 47). Negative correlations between the two were observed in the right posterior cingulate gyrus (BA 31) and left medial frontal lobe (BA 9).

CONCLUSION

These preliminary results confirm the role of the subthalamic nucleus in associative and limbic circuitry in humans and suggest that it is a key basal ganglia structure in motivation circuitry.

Subthalamic nucleus stimulation affects orbitofrontal cortex in facial emotion recognition: a PET study

Deep brain stimulation (DBS) of the bilateral subthalamic nucleus (STN) in Parkinson's disease is thought to produce adverse events such as emotional disorders, and in a recent study, we found fear recognition to be impaired as a result. These changes have been attributed to disturbance of the STN's limbic territory and would appear to confirm that the negative emotion recognition network passes through the STN. In addition, it is now widely acknowledged that damage to the orbitofrontal cortex (OFC), especially the right side, can result in impaired recognition of facial emotions (RFE). In this context, we hypothesized that this reduced recognition of fear is correlated with modifications in the cerebral glucose metabolism of the right OFC. The objective of the present study was first, to reinforce our previous results by demonstrating reduced fear recognition in our Parkinson's disease patient group following STN DBS and, second, to correlate these emotional performances with glucose metabolism using ¹⁸FDG-PET. The ¹⁸FDG-PET and RFE tasks were both performed by a cohort of 13 Parkinson's disease patients 3 months before and 3 months after surgery for STN DBS. As predicted, we observed a significant reduction in fear recognition following surgery and obtained a positive correlation between these neuropsychological results and changes in glucose metabolism, especially in the right OFC. These results confirm the role of the STN as a key basal ganglia structure in limbic circuits.